WO2011004461A1 - Light detector, optical pickup and control method - Google Patents

Light detector, optical pickup and control method Download PDF

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Publication number
WO2011004461A1
WO2011004461A1 PCT/JP2009/062383 JP2009062383W WO2011004461A1 WO 2011004461 A1 WO2011004461 A1 WO 2011004461A1 JP 2009062383 W JP2009062383 W JP 2009062383W WO 2011004461 A1 WO2011004461 A1 WO 2011004461A1
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WO
WIPO (PCT)
Prior art keywords
light
detection region
lens
recording medium
photodetector
Prior art date
Application number
PCT/JP2009/062383
Other languages
French (fr)
Japanese (ja)
Inventor
裕 松井
正浩 加藤
英作 川野
博之 田中
徹 鐘江
正憲 堀田
Original Assignee
パイオニア株式会社
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Application filed by パイオニア株式会社 filed Critical パイオニア株式会社
Priority to PCT/JP2009/062383 priority Critical patent/WO2011004461A1/en
Publication of WO2011004461A1 publication Critical patent/WO2011004461A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1387—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector using the near-field effect
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/133—Shape of individual detector elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B7/1374—Objective lenses
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B2007/13727—Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only

Definitions

  • the present invention relates to a technical field of a photodetector provided in an apparatus for recording or reproducing information via evanescent light, an optical pickup including the photodetector, and a method for controlling the optical pickup.
  • a lens such as a solid immersion lens (SIL) is used, for example, from a recording medium such as an optical disk. It can be brought close to a position separated by a predetermined distance such as several tens of nanometers (nanometers).
  • the lens is often controlled according to the distance between the lens and the recording medium detected based on the signal output from the photodetector.
  • Patent Document 1 describes a quadrant photodetector in which a circular dead zone is provided at the center.
  • a technique for improving detection sensitivity by setting the dead zone diameter to one half of the beam diameter is described.
  • Patent Document 1 the technique described in Patent Document 1 is intended for a far-field optical system that does not generate evanescent light, and it is difficult to apply directly to a near-field optical system that generates evanescent light. There is.
  • the present invention has been made in view of the above problems, for example, and provides a photodetector, an optical pickup, and a control method that can be used in a near-field optical system and can improve detection sensitivity. Is an issue.
  • the photodetector of the present invention is a photodetector provided in an optical pickup including a lens capable of generating evanescent light with respect to a recording medium, and includes a light receiving surface of the photodetector. And a first detection region for detecting a first portion of the reflected light reflected by the surface of the lens on the recording medium side, and at least partially surrounding the first detection region, which is different from the first portion. A second detection region for detecting a second portion of the reflected light.
  • the photodetector is provided in an optical pickup including a lens such as a solid immersion lens capable of generating evanescent light with respect to a recording medium. That is, the photodetector constitutes a part of the optical pickup.
  • the photodetector receives, for example, reflected light reflected from the surface of the lens on the recording medium side, and outputs a signal corresponding to the amount of the received light.
  • the photodetector may receive reflected light reflected by the recording medium in addition to reflected light reflected by the surface of the lens on the recording medium side.
  • the light detector includes a first detection region for detecting a first portion of reflected light on a light receiving surface of the light detector, and at least partially surrounds the first detection region, and is different from the first portion.
  • a second detection region for detecting a second portion of the reflected light That is, the photo detector is a split photo detector.
  • the “first portion of reflected light” and the “second portion of reflected light” are respectively “light incident on the first detection region of the reflected light” and “light incident on the second detection region of the reflected light”. It means “light”.
  • the first detection area may be, for example, a circular area, an annular area, or an arc area in accordance with the shape of the light spot formed on the photodetector.
  • the second detection region may be, for example, an arc region that partially surrounds the first detection region, or may be, for example, an annular region that surrounds the first detection region. Alternatively, it may be an area other than the first detection area on the light receiving surface of the photodetector.
  • the second detection region is preferably an annular region or an arc region. Further, the second detection area may not be adjacent to the first detection area, that is, there may be a gap between the second detection area and the first detection area.
  • the lens in order to perform recording or reproduction of information via evanescent light, the lens is moved from the recording medium to a distance equal to or less than a half of the wavelength of light irradiated on the recording medium (for example, several tens of nm). Must be close. At this time, the lens may come into contact with the recording medium due to overshoot or servo error.
  • the moving speed of the lens, the timing when the servo loop is closed, etc. are set appropriately, that is, it corresponds to the distance between the lens and the recording medium. It is necessary to detect the signal appropriately.
  • the light spot on the light receiving surface of the photodetector changes. Specifically, for example, immediately before the lens enters the near field region, the amount of light corresponding to a numerical aperture (NA) of less than 1 increases, and immediately after the lens enters the near field region, NA. The amount of light corresponding to the vicinity of 1 decreases.
  • NA numerical aperture
  • the amount of change in the amount of light is small, and it is difficult to determine, for example, whether the lens has entered the near field region.
  • a second detection region for detecting that is, in the present invention, by providing a plurality of detection areas for detecting reflected light, the amount of change in the amount of light in each detection area is relatively increased, and the S / N ratio (or detection sensitivity) of the photodetector is increased. Can be improved.
  • the first detection region is a circular region or an annular region corresponding to a circle formed by light having NA corresponding to 1, light received in the first detection region (that is, NA corresponding to less than 1). It is possible to detect that the lens reaches the near field region on the condition that the amount of light) is increased. Further, if the inner edge of the second detection region is a circle corresponding to a circle formed by light having NA equal to 1, the light received in the second detection region (that is, light having NA equal to or greater than 1). It is possible to detect that the lens has entered the near field area on condition that the amount of light has decreased.
  • the photodetector of the present invention it is possible to determine whether or not the lens has entered the near-field region with relative ease. Therefore, for example, the moving speed of the lens, the timing for closing the servo loop, and the like can be appropriately set.
  • each of the outer edge of the first detection region and the inner edge of the second detection region forms at least a part of a concentric circle sharing the center of the first detection region.
  • a signal corresponding to the distance between the lens and the recording medium can be detected from the change of the light spot on the light receiving surface of the photodetector relatively easily.
  • the photodetector is typically installed so that the center of the spot of light incident on the photodetector coincides with the center of the first detection region.
  • the second detection region is at least partially surrounded, and a third portion of the reflected light different from the first and second portions is detected.
  • a fourth detection region that at least partially surrounds the third detection region and detects a fourth portion of the reflected light different from the first to third portions.
  • the photodetector at least partially surrounds the second detection region, and reflects light that is different from the first and second portions.
  • the “third portion of reflected light” and the “fourth portion of reflected light” are respectively “light entering the third detection region of the reflected light” and “light entering the fourth detection region of the reflected light”. It means “light”.
  • the third detection region may be, for example, an arc region that partially surrounds the second detection region, or may be, for example, an annular region that surrounds the second detection region.
  • the fourth detection region may be, for example, an arc region that partially surrounds the third detection region, or may be, for example, an annular region that surrounds the third detection region.
  • the fourth detection region may be a region other than the first to third detection regions on the light receiving surface of the photodetector.
  • the fourth detection region is an annular region having an outer edge corresponding to the outermost periphery of the spot on the light receiving surface of the photodetector and an inner edge a predetermined distance from the outer edge or a part of the annular region. If a certain arc region is used, the fact that the lens has come close to contact with the recording medium on the condition that the amount of light received in the fourth detection region has decreased (that is, it is in an excessively close state). Can be detected. As a result, it is possible to avoid the lens from coming into contact with the recording medium relatively easily.
  • each of the outer edge of the first detection region, the outer edge of the second detection region, and the outer edge of the third detection region constitutes at least a part of a concentric circle sharing the center of the first detection region. Good.
  • an optical pickup includes a light source that irradiates a recording medium with light, a lens that is disposed in an optical path of the irradiated light, and that can generate evanescent light with respect to the recording medium.
  • a photodetector for receiving at least reflected light reflected from the surface of the lens on the recording medium side of the irradiated light, driving means for driving the lens, and output from the photodetector Control means for controlling the drive means to drive the lens based on a signal, and the light detector detects a first portion of the reflected light on a light receiving surface of the light detector. And a second detection region that at least partially surrounds the first detection region and detects a second portion of the reflected light different from the first portion.
  • a light source such as a semiconductor laser irradiates a recording medium such as an optical disk with light.
  • a lens such as a solid immersion lens, that can generate evanescent light with respect to the recording medium is disposed in the optical path of the irradiated light.
  • the photodetector receives reflected light of a specific polarization state reflected by the surface of the lens on the recording medium side or the recording medium of the irradiated light.
  • the reflected light of a specific polarization state reflected by the recording medium is the polarization state of the reflected light related to light having a large incident angle out of light having an NA of less than 1, and the s-polarization component and the p-polarization component.
  • the photodetector has a first detection region for detecting the first portion of the reflected light on the light receiving surface of the photodetector, and at least partially surrounds the first detection region, and is different in reflection from the first portion. And a second detection region for detecting a second portion of light.
  • a driving means such as a lens actuator can drive the lens.
  • the control unit controls the driving unit to drive the lens based on the signal output from the photodetector.
  • the control means is provided on the condition that the amount of light received by the first detection area has increased. Controls the driving means so that the speed of the lens approaching the recording medium decreases.
  • the control means On the condition that the inner edge of the second detection area is a circle corresponding to the circle formed by the light whose NA is equal to 1, and the light quantity of the light received in the second detection area is reduced, the control means The driving means is controlled so that the lens follows the recording medium with the loop closed.
  • the moving speed of the lens, the timing when the servo loop is closed, and the like can be appropriately set.
  • the outer edge of the first detection region corresponds to the outer edge of a circle formed on the light receiving surface by light corresponding to a numerical aperture of 1 among the reflected light.
  • the inner edge of the second detection region corresponds to the outer edge of a circle formed on the light receiving surface by light corresponding to a numerical aperture of 1 among the reflected light.
  • the servo loop can be appropriately closed in a relatively easy manner based on the amount of light received in the second detection region.
  • the first control method of the present invention is arranged in a light source for irradiating light on a recording medium and an optical path of the irradiated light, and can generate evanescent light on the recording medium
  • An optical lens, a photodetector for receiving reflected light reflected by at least a surface of the lens on the recording medium side, and a driving means capable of driving the lens, the photodetector Includes a first detection region for detecting a first portion of the reflected light on a light receiving surface of the photodetector, and at least partially surrounds the first detection region, and the reflected light different from the first portion.
  • a second detection area for detecting the second portion of the optical pickup, wherein the lens approaches the recording medium according to the amount of light received by the first detection area so as to reduce the speed of the lens approaching the recording medium.
  • Deceleration controlling the drive means It provided with a degree.
  • the driving means is controlled so as to reduce the speed of the lens approaching the recording medium in accordance with the amount of light received in the first detection area.
  • the method further includes a closing step of closing the servo loop in accordance with the amount of light received in the second detection region after the deceleration step.
  • the servo loop is closed according to the amount of light received in the second detection region.
  • the inner edge of the second detection region is a circle corresponding to a circle formed by light having NA equal to 1
  • the lens enters the near field region based on the amount of light received by the second detection region. Can be detected.
  • the servo loop can be appropriately closed in the near field region.
  • the speed of the lens approaching the recording medium on condition that the amount of light received in the second detection region is smaller than a first threshold value.
  • a second deceleration step for controlling the driving means so as to further decrease the servo loop and after the second deceleration step, the servo loop is closed on condition that the amount of light received in the second detection region is smaller than a second threshold value And a closing step.
  • the driving unit is configured to further reduce the speed of the lens approaching the recording medium. Is controlled.
  • the servo loop is closed on the condition that the amount of light received in the second detection region is smaller than the second threshold value. For this reason, the servo loop can be closed while the distance between the lens and the recording medium is shorter.
  • the “first threshold value” is a value that determines whether or not to control the driving unit so as to further reduce the speed at which the lens approaches the recording medium, and is set in advance as a fixed value or to some physical quantity or parameter. It is set as a variable value. Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining a relationship between the amount of light received in the second detection region and the distance between the lens and the recording medium, and based on the obtained relationship.
  • the distance that the lens moves due to inertia and the distance between the lens and the recording medium are set equal to the received light amount, or the received light amount that is larger than the received light amount by a predetermined amount. do it.
  • the “second threshold value” is a value that determines whether or not the servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining a relationship between the amount of light received in the second detection region and the distance between the lens and the recording medium, and based on the obtained relationship. The light reception amount corresponding to the distance at which the servo loop should be closed may be set.
  • the second control method of the present invention is arranged in a light source for irradiating light to the recording medium and an optical path of the irradiated light, and can generate evanescent light to the recording medium
  • a detector at least partially surrounds the first detection region and a first detection region for detecting the first portion of the reflected light on a light receiving surface of the photodetector, and the reflection is different from the first portion;
  • the difference between the received light amount of the first detection region and the received light amount of the second detection region in the present invention, typically, the received light of the second detection region.
  • the difference obtained by subtracting the amount of light received in the first detection area from the amount is calculated.
  • the calculation step is periodically performed, for example, every predetermined period.
  • the driving means is controlled so as to reduce the speed of the lens approaching the recording medium on condition that the calculated difference once increases and then increases.
  • the distance that the lens moves due to inertia can be made relatively short. Therefore, it is possible to avoid the lens from colliding with the recording medium.
  • the amount of light received in the first detection region increases once and then decreases immediately before the lens enters the near field region. For this reason, the difference obtained by subtracting the amount of light received in the first detection region from the amount of light received in the second detection region will increase after once decreasing immediately before the lens enters the near field region.
  • the third control method of the present invention is arranged in a light source for irradiating the recording medium with light and an optical path of the irradiated light, and can generate evanescent light with respect to the recording medium.
  • a detector at least partially surrounds the first detection region and a first detection region for detecting the first portion of the reflected light on a light receiving surface of the photodetector, and the reflection is different from the first portion;
  • a second detection region for detecting a second portion of light and a third detection for detecting a third portion of the reflected light that at least partially surrounds the second detection region and is different from the first and second portions.
  • Region and at least part of the third detection region And a fourth detection region for detecting the fourth portion of the reflected light that is different from the first to third portions, wherein the amount of received light in the fourth detection region is Accordingly, there is provided a collision avoidance step for controlling the driving means so that the lens does not collide with the recording medium.
  • the driving means is controlled so that the lens does not collide with the recording medium in accordance with the amount of light received in the fourth detection area.
  • the driving unit is controlled so as to move the lens away from the recording medium.
  • FIG. 1 is a block diagram showing the configuration of the optical pickup according to the present embodiment. Note that a dotted line L in the figure indicates an optical path.
  • an optical pickup 20 includes a semiconductor laser 201, a collimator lens 202, a diffraction grating 203, a non-polarizing beam splitter 204, a polarizing beam splitter 205, a beam expander 206, a quarter-wave plate 207, a mirror 208, a solid immersion.
  • SIL assembly 209 having lens 210 (hereinafter referred to as “SIL” as appropriate), lenses 211 and 213, light receiving element 212 for RF (Radio Frequency), light receiving element 100 for GE (Gap Error), front monitor (FM) 214, A lens actuator 220 and a gap error (GE) servo circuit 30 are provided.
  • the optical pickup 20 is mounted on a recording / reproducing apparatus that records information on the optical disc 10 or reproduces information recorded on the optical disc 10 via evanescent light, for example.
  • the light L emitted from the semiconductor laser 201 is incident on the diffraction grating 203 via the collimator lens 202.
  • the light L separated into a plurality of diffracted lights by the diffraction grating 203 is sent to the SIL assembly 209 via the non-polarizing beam splitter 204, the polarizing beam splitter 205, the beam expander 206, the quarter wavelength 207, and the mirror 208.
  • light L having a wavelength of 400 nm is emitted from the semiconductor laser 201.
  • a power comparison circuit (not shown) is electrically connected to the front monitor 214.
  • a signal indicating the intensity of the light L transmitted from the front monitor 214 is compared with a reference signal.
  • the power comparison circuit transmits a signal indicating the result of the comparison to a laser driver (not shown).
  • the laser driver controls the output of the semiconductor laser 201 based on the transmitted signal.
  • a part of the light L incident on the SIL 210 is emitted to the optical disc 10 as evanescent light, and the other part is reflected on the bottom of the SIL 210.
  • the reflected light from the optical disk 10 enters the SIL 210 again, and enters the polarization beam splitter 205 via the mirror 208, the quarter-wave plate 207, and the beam expander 206.
  • the polarization direction of the light L emitted from the semiconductor laser 201 and the polarization direction of the reflected light from the optical disk 10 are different from each other by 90 degrees, the reflected light from the optical disk 10 passes through the lens 211 and is RF.
  • Incident light receiving element 212 is, for example, a two-divided or four-divided light receiving element.
  • an RF signal generation circuit (not shown) is electrically connected to the RF light receiving element 212, and an RF signal caused by reflected light incident on the RF light receiving element 212 is generated.
  • the generated RF signal is transmitted to a reproduction signal processing unit (not shown) including, for example, a demodulation circuit, an error correction circuit, a decoding circuit, and the like.
  • a tracking servo circuit (not shown).
  • a tracking error signal is generated by the tracking servo circuit, and the lens actuator 220 is controlled based on the generated tracking error signal so that the position of the spot on the optical disc 10 becomes a predetermined position.
  • the light reflected at the bottom of the SIL 210 enters the non-polarizing beam splitter 204 through the mirror 208, the quarter-wave plate 207, the beam expander 206, and the polarizing beam splitter 205.
  • a part of the light reflected from the bottom of the SIL 210 enters the GE light receiving element 100 through the lens 213.
  • the gap error servo circuit 30 is electrically connected to the light receiving element 214 for GE.
  • the gap error servo circuit 30 controls the lens actuator 220 so that the distance between the bottom of the SIL 210 and the surface of the optical disk 10 (that is, the gap) is a predetermined distance.
  • the “optical disk 10”, “gap error servo circuit 30”, “GE light receiving element 100”, “semiconductor laser 201”, “SIL 210”, and “lens actuator 220” according to the present embodiment are respectively included in the present invention.
  • This is an example of the “recording medium”, “control unit”, “photodetector”, “light source”, “lens”, and “driving unit”.
  • the “bottom portion of the SIL 210” according to the present embodiment is an example of the “surface on the recording medium side of the lens” according to the present invention.
  • FIG. 2 is a block diagram showing a configuration of a light receiving element for GE and a gap error servo circuit according to the present embodiment.
  • the GE light receiving element 100 includes a first detection region 111 and a second detection region 112 that surrounds the first detection region 111 from the outer edge side on the light receiving surface. ing. As shown in FIG. 2, the outer edge of the first detection region 111 and the outer edge of the second detection region 112 are concentric circles that share the center of the first detection region 111.
  • the first detection area 111 is a circular area having a radius r.
  • the radius r corresponds to the radius of a circle formed on the light receiving element 100 for GE by light corresponding to NA of 1.
  • the first detection region 111 reflects light having a NA corresponding to less than 1 among the light L emitted from the semiconductor laser 201, for example, light incident on the bottom surface of the SIL 210 at an incident angle of ⁇ B ⁇ ⁇ ⁇ ⁇ C. Receives light.
  • ⁇ B ” and “ ⁇ C ” indicate “Brewster angle” and “critical angle”, respectively.
  • the second detection region 112 is an annular region having an inner diameter r and an outer diameter R.
  • the outer diameter R corresponds to the radius of a circle formed on the light receiving element 100 for GE by light corresponding to the maximum numerical aperture of the SIL 210.
  • the maximum numerical aperture of the SIL 210 is 2.26, for example.
  • the second detection region 112 receives light L totally emitted from the bottom surface of the SIL 210 (that is, light having NA equal to or greater than 1) out of the light L emitted from the semiconductor laser 201.
  • the gap error servo circuit 30 has a configuration as shown in FIG. 2, for example.
  • the speed at which the SIL assembly 209 approaches the optical disc 10 is controlled based on a signal indicating the amount of light received by the first detection region 111 that is output from the first detection region 111.
  • a gap error signal is generated based on a signal indicating the amount of light received by the second detection region 112 that is output from the second detection region 112.
  • FIG. 3 is an example of a simulation result showing the relationship between the light reception ratio and the gap.
  • FIG. 3A is an example of a simulation result of the light receiving element for GE according to the present embodiment
  • FIG. 3B is an example of a simulation result of the light receiving element for GE according to the comparative example of the present embodiment.
  • the light reception ratio (Detected light ratio) according to the present embodiment means the ratio of the light reception area to the area of the detection region.
  • the broken line in FIG. 3A indicates the light reception ratio related to the first detection region 111
  • the solid line indicates the light reception ratio related to the second detection region 112.
  • the light reception ratio of the GE light receiving element 100 will be described.
  • the gap between the bottom of the SIL 210 and the surface of the optical disc 10 (hereinafter referred to as “gap” as appropriate) is 1000 nm or more, no light is detected in the first detection region 111.
  • the gap is 1000 nm or more, no light is detected in the first detection region 111.
  • light corresponding to NA of less than 1 passes through the bottom surface of the SIL 210 and is reflected by the optical disk 10 and is incident on the RF light receiving element 212 by the polarization beam splitter 205 as described above.
  • the light corresponding to NA of 1 or more is totally reflected on the bottom surface of the SIL 210, so that the light is detected in the second detection region 112.
  • transition region When the gap is 200 nm to 1000 nm (hereinafter referred to as “transition region” as appropriate), light is detected in both the first detection region 111 and the second detection region 112. This is because part of the light reflected by the optical disc 10 is incident on the first detection region 111 of the GE light receiving element 100 without being reflected by the polarizing beam splitter 205 toward the RF light receiving element 212 side.
  • the gap is 200 nm or less (that is, the near field region)
  • no light is detected in the first detection region 111.
  • the light reception ratio related to the second detection region 112 decreases as the gap decreases. This is because evanescent light is generated due to the SIL 210 entering the near field region of the optical system according to the present embodiment.
  • the light reception ratio related to the first detection region 111 increases significantly, so that the SIL 210 approaches the near field region according to the light reception ratio related to the first detection region 111. Can be detected.
  • the light receiving element for GE according to the comparative example is a light receiving element in which the light receiving surface is not divided. As shown in FIG. 3B, the light reception ratio gradually increases in the transition region. Further, when the gap is 200 nm or less, the light receiving ratio decreases as the gap becomes smaller.
  • the amount of increase in the light reception ratio in the transition region is relatively small, so that it is difficult to detect that the SIL 210 has approached the near field region in practice.
  • the GE light receiving element 100 according to the present embodiment is divided into the first detection region 111 and the second detection region 112
  • the dynamic range in the near field region is an undivided light receiving element (that is, It is larger than the light receiving element according to the comparative example of the present embodiment.
  • the S / N ratio of the gap error signal can be improved.
  • the light reception ratio related to the first detection region 111 fluctuates relatively greatly, so that it is possible to appropriately detect that the SIL 210 has approached the near field region.
  • the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S101).
  • the gap error servo circuit 30 detects the amount of light received by the first detection region 111 of the light receiving element 100 for GE (step S102). Note that the detection of the amount of light received in the first detection region 111 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the detected amount of received light is greater than or equal to a threshold value (step S103). If it is determined that the detected amount of received light is equal to or greater than the threshold (step S103: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S104). On the other hand, when it is determined that the detected amount of received light is less than the threshold value (step S103: No), the gap error servo circuit 30 executes the process of step S101.
  • the “threshold value” is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and may be a fixed value or some sort of value in advance. It is set as a variable value according to the physical quantity or parameter. Such a threshold is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of light received in the first detection region 111 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
  • the GE light receiving element 100 is not limited to the form shown in FIG.
  • the GE light receiving element 100 may have, for example, an arc-shaped second detection region 112 as shown in FIG. 5A, or the GE light receiving element 100 as shown in FIG. 5B.
  • the second detection region 112 may be a region other than the first detection region 111 of the light receiving surface.
  • the light receiving element 100 for GE may have an annular first detection region 111 as shown in FIG. 5C, for example.
  • FIG. 5 is a schematic diagram showing a modification of the light receiving element for GE according to the present embodiment.
  • FIG. 6 is a block diagram showing the configuration of a light receiving element for GE and a gap error servo circuit according to this modification having the same concept as in FIG.
  • the first detection region 111 output from the first detection region 111. Based on a difference signal obtained by subtracting a signal indicating the amount of received light, control of the speed at which the SIL assembly 209 approaches the optical disk 10 and generation of a gap error signal are performed.
  • FIG. 7 is another example of the simulation result showing the relationship between the light reception ratio and the gap, which has the same concept as in FIG.
  • the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S201).
  • the gap error servo circuit 30 detects the amount of light received by the second detection region 112 (step S202) and receives the amount of light received by the first detection region 111. Is detected (step S203). Subsequently, the gap error servo circuit 30 calculates the difference light amount by subtracting the detected light amount related to the first detection region from the detected light amount related to the second detection region 112 (step S204). Note that the processing in steps S202 and S203 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the calculated difference light amount is equal to or less than a threshold value (step S205). When it is determined that the calculated difference light amount is equal to or smaller than the threshold (step S205: Yes), the gap error servo circuit 30 continues to control the lens actuator 220 so that the SIL assembly 209 approaches the optical disc 10 (step S206). ). On the other hand, when it is determined that the calculated difference light amount is larger than the threshold value (step S205: No), the gap error servo circuit 30 executes the process of step S201.
  • the gap error servo circuit 30 detects the amount of light received by the second detection region 112 (step S207) and also receives the amount of light received by the first detection region 111. Is detected (step S208). Subsequently, the gap error servo circuit 30 calculates the difference light amount by subtracting the detected light amount related to the first detection region from the detected light amount related to the second detection region 112 (step S209). Note that the processing in steps S207 and S208 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the calculated difference light amount is greater than or equal to a threshold value (step S210). If it is determined that the calculated difference light amount is equal to or greater than the threshold (step S210: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S111). On the other hand, when it is determined that the calculated difference light quantity is less than the threshold value (step S210: No), the gap error servo circuit 30 executes the process of step S206.
  • the control method by detecting that the difference light amount becomes equal to or greater than the threshold value after becoming less than or equal to the threshold value, the light amount ratio increases as shown in FIG. The phenomenon is detected.
  • the “threshold value” according to this modification is set as a value that can reliably detect the phenomenon that the threshold value increases after the light reception ratio decreases.
  • the threshold value in step S205 and the threshold value in step S210 may be the same or different from each other.
  • FIGS. 9 to 14 A second embodiment of the photodetector of the present invention will be described with reference to FIGS.
  • the second embodiment is the same as the first embodiment except that the configurations of the light receiving element for GE and the gap error servo circuit are partially different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and common portions in the drawings are denoted by the same reference numerals, and FIGS. 9 to 14 are shown only for different points. The description will be given with reference.
  • FIG. 9 is a schematic diagram showing a light receiving element for GE according to the present embodiment.
  • FIG. 10 is a block diagram showing the configuration of the light receiving element for GE and the gap error servo circuit according to the present embodiment having the same concept as in FIG.
  • the light receiving element 100 for GE includes, on its light receiving surface, a first detection area 121, a second detection area 122 surrounding the first detection area 121 from its outer edge side, and the second detection area 122.
  • a third detection region 123 that surrounds from the outer edge side and a fourth detection region 124 that surrounds the third detection region 123 from the outer edge side are configured.
  • the outer edge of the first detection region 121, the outer edge of the second detection region 122, the outer edge of the third detection region 123, and the outer edge of the fourth detection region 124 share the center of the first detection region 121. It is a concentric circle.
  • the first detection area 121 is a circular area having a radius r.
  • the second detection region 122 is an annular region having an inner diameter r and an outer diameter (1 + ⁇ N) r.
  • ⁇ N is a value such as 0.2.
  • the third detection region 123 is an annular region having an inner diameter (1 + ⁇ N) r and an outer diameter R ⁇ N ⁇ r.
  • the fourth detection region 124 is an annular region having an inner diameter R ⁇ N ⁇ r and an outer diameter R.
  • the SIL 210 when the SIL 210 enters the near field region, the amount of light corresponding to NA of 1 or more decreases due to the generation of evanescent light.
  • the gap becomes smaller light having a low NA does not enter the light receiving element 100 for GE (that is, a dark part generated at the center of the spot gradually spreads).
  • the SIL 210 has entered the near field region by dividing the region corresponding to the second detection region 112 according to the first embodiment into a plurality of detection regions. It is possible to detect that the SIL 210 is too close to the optical disk 10 or the like.
  • the gap error servo circuit 30 outputs a signal indicating the amount of light received by the first detection area 121 output from the first detection area 121 and the second output from the second detection area 122. Based on a signal indicating the amount of light received by the detection region 122 and a signal indicating the amount of light received by the fourth detection region 124 output from the fourth detection region 124, the SIL assembly 209 Control of the speed approaching the optical disk 10, control of timing for closing the servo loop, and collision avoidance processing are performed.
  • the gap error servo circuit 30 also outputs a signal indicating the amount of light received by the second detection region 122 output from the second detection region 122 and the third detection region output from the third detection region 123. 123, based on a signal indicating the amount of light received by 123 and a signal indicating the sum of signals indicating the amount of light received by the fourth detection region 124 output from the fourth detection region 124. Generate an error signal.
  • FIG. 11 is another example of the simulation result showing the relationship between the light reception ratio and the gap, which has the same concept as in FIG.
  • FIG. 11A shows the light reception ratio related to the first detection region 121
  • FIG. 11B shows the light reception ratio related to the second detection region 122
  • FIG. 11 , The light reception ratio relating to the fourth detection region 124 is shown.
  • the amount of light corresponding to NA near 1 decreases due to the generation of evanescent light. For this reason, as shown in FIG.11 (b), the light reception ratio concerning the 2nd detection area
  • the SIL 210 When the SIL 210 is so close that it may come into contact with the optical disk 10 (that is, in an excessively close state), the amount of light at the outermost periphery of the spot on the GE light receiving element 100 decreases. For this reason, as shown in FIG.11 (c), the light reception ratio concerning the 4th detection area
  • the GE light receiving element 100 is divided into the first detection region 121, the second detection region 122, the third detection region 123, and the fourth detection region 124. Therefore, it is possible to detect that the SIL 210 has approached the near field area based on the amount of light received in the first detection area 121. Further, it is possible to detect that the SIL 210 has entered the near field area based on the amount of light received in the second detection area 122. Further, it is possible to detect that the SIL 210 is in an excessively close state based on the amount of light received in the fourth detection region 124.
  • the rising or falling slope of the light reception ratio is relatively large.
  • the gap can be detected with high sensitivity.
  • a change in gap of 16.05 nm can be detected by a 1% change in the light reception ratio related to the first detection region 121.
  • a change in gap of 0.32 nm can be detected by a change of 1% in the light reception ratio of the second detection region 122.
  • a change in gap of 0.32 nm can be detected by a 1% change in the light reception ratio of the fourth detection region 124. This is a maximum of about 25 times the sensitivity when the undivided light receiving element is applied to the light receiving element 100 for GE.
  • the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S301).
  • the gap error servo circuit 30 detects the amount of light received by the first detection region 121 of the light receiving element 100 for GE (step S302). Note that the detection of the amount of light received in the first detection region 121 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or greater than a threshold value (step S303). If it is determined that the detected amount of received light is equal to or greater than the threshold (step S303: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S304). On the other hand, when it is determined that the detected amount of received light is less than the threshold (step S303: No), the gap error servo circuit 30 executes the process of step S301.
  • step S304 the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S305).
  • the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S306).
  • the detection of the amount of received light related to the second detection region 122 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S307). When it is determined that the detected amount of received light is equal to or less than the threshold (step S307: Yes), the gap error servo circuit 30 closes the gap servo loop (step S308). On the other hand, when it is determined that the detected amount of received light is larger than the threshold (step S307: No), the gap error servo circuit 30 executes the process of step S305.
  • the “threshold value” in the process of step S303 according to the present embodiment is a value that determines whether to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is fixed in advance. It is set as a value or a variable value according to some physical quantity or parameter. Such a threshold value is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of light received in the first detection region 121 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
  • the “threshold value” in the process of step S307 according to the present embodiment is a value that determines whether or not the gap servo loop is to be closed, and is a fixed value in advance or a variable value according to some physical quantity or parameter Set as Such a threshold value is set based on the obtained relationship by obtaining, for example, a relationship between the signal level indicating the amount of received light related to the second detection region 122 and the gap experimentally, empirically, or by simulation. That's fine.
  • the collision avoidance process executed by the gap error servo circuit 30 will be described.
  • the collision avoidance process is executed mainly when the gap servo loop is in a closed state.
  • the gap error servo circuit 30 detects the amount of light received by the fourth detection region 124 of the GE light receiving element 100 (step S401). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S402).
  • the gap error servo circuit 30 executes a collision avoidance process (step S403).
  • the collision avoidance process means a process for avoiding a collision between the SIL assembly 209 and the optical disk 10 such as moving the SIL assembly 209 away from the optical disk 10 or interrupting the gap servo.
  • step S402 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S405).
  • step S405: Yes If it is determined that the detected amount of received light is greater than or equal to the threshold (step S405: Yes), the gap error servo circuit 30 turns off the gap servo (step S406). On the other hand, when it is determined that the detected amount of received light is smaller than the threshold value (step S405: No), the gap error servo circuit 30 executes the process of step S401.
  • the “threshold value” in the process of step S402 according to the present embodiment is a value that determines whether or not to perform the collision avoidance process, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter. Is done. Such a threshold is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of received light related to the fourth detection region 124 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
  • the “threshold value” in the process of step S405 according to the present embodiment is a value that determines whether or not the gap servo is turned off, and is a fixed value in advance or a variable value according to some physical quantity or parameter. Is set. Such a threshold value is set based on the obtained relationship by obtaining, for example, a relationship between the signal level indicating the amount of received light related to the second detection region 122 and the gap experimentally, empirically, or by simulation. That's fine.
  • the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S501).
  • the gap error servo circuit 30 detects the amount of light received by the first detection region 121 of the light receiving element 100 for GE (step S502). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is greater than or equal to a threshold value (step S503).
  • step S503: Yes the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S504).
  • step S503: No the gap error servo circuit 30 executes the process of step S501.
  • step S504 the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S505).
  • the gap error servo circuit 30 In parallel with the processing in step S505, the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S506). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than the first threshold (step S507).
  • step S507: Yes When it is determined that the detected amount of received light is equal to or less than the first threshold (step S507: Yes), the gap error servo circuit 30 moves the lens actuator 220 so that the speed at which the SIL assembly 209 approaches the optical disc 10 is further reduced. Control is performed (step S508). On the other hand, when it is determined that the detected amount of received light is larger than the first threshold (step S507: No), the gap error servo circuit 30 executes the process of step S505.
  • step S508 the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S509).
  • the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S510). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than the second threshold (step S511).
  • step S511: Yes When it is determined that the detected amount of received light is equal to or less than the second threshold (step S511: Yes), the gap error servo circuit 30 closes the gap servo loop (step S511). On the other hand, when it is determined that the detected amount of received light is larger than the second threshold (step S511: No), the gap error servo circuit 30 executes the process of step S509.
  • the gap servo loop can be closed with a smaller gap than in the second embodiment described above.
  • the “threshold value” in the process of step S503 according to this modification may be set in the same manner as the “threshold value” in the process of step S303 according to the second embodiment described above.
  • the “first threshold value” in step S507 is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is set as a fixed value in advance. Or a variable value according to some physical quantity or parameter.
  • Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the amount of received light and the gap related to the second detection region 122 and, based on the determined relationship, the lens actuator 220.
  • the distance of movement of the SIL assembly 209 due to inertia and the received light amount equal to the gap may be set, or the received light amount may be set larger than the received light amount by a predetermined amount.
  • the “second threshold value” is a value that determines whether or not the gap servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the amount of received light and the gap related to the second detection region 122 and, based on the determined relationship, the gap servo loop. What is necessary is just to set as a light reception amount corresponding to the distance which should be set as a closed state.
  • FIGS. 1 and 2 A third embodiment of the photodetector of the present invention will be described with reference to FIGS.
  • the third embodiment is the same as the second embodiment except that the configuration of the light receiving element for GE is partially different. Accordingly, the description of the third embodiment that is the same as that of the second embodiment is omitted, and common portions in the drawings are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. The description will be given with reference.
  • FIG. 15 is a schematic diagram showing a light receiving element for GE according to the present embodiment having the same purpose as in FIG.
  • the light receiving element 100 for GE includes a first detection region 131, a second detection region 132 surrounding the first detection region 131 from the outer edge side, and the second detection region 132 on the light receiving surface.
  • a third detection region 133 surrounding the outer edge side and a fourth detection region 134 surrounding the third detection region 133 from the outer edge side are configured.
  • the outer edge of the first detection region 131, the outer edge of the second detection region 132, the outer edge of the third detection region 133, and the outer edge of the fourth detection region 134 share the center of the first detection region 131. It is a concentric circle.
  • each detection region is set as follows so as to appropriately cope with the optical axis shift.
  • the first detection area 131 is a circular area with a radius r ⁇ S.
  • the second detection region 132 is an annular region having an inner diameter r ⁇ S and an outer diameter (1 + ⁇ N) r + S.
  • the third detection region 133 is an annular region having an inner diameter (1 + ⁇ N) r + S and an outer diameter R ⁇ N ⁇ r ⁇ S.
  • the fourth detection region 134 is an annular region having an inner diameter R ⁇ N ⁇ r ⁇ S and an outer diameter R + S.
  • S means an assumed upper limit value of the optical axis shift on the light receiving element 100 for GE.
  • S is, for example, 0.2r (where “r” is equivalent to the radius of the circle formed on the light receiving element 100 for GE when NA is equal to 1 as described above) What is necessary is just to set according to the optical system etc. of an optical pick-up provided with the light receiving element 100 for GE.
  • FIG. 16 is an example of a simulation result showing the change in the light reception ratio in the transition region for each optical axis shift amount.
  • FIG. 17 is an example of a simulation result showing the change in the light reception ratio when the gap is in the vicinity of 200 nm for each optical axis deviation amount.
  • FIG. 18 is an example of a simulation result showing the change in the light reception ratio in the excessively close area for each optical axis deviation amount.
  • FIGS. 16A, 17A, and 18A are simulation results of the light receiving element 100 for GE according to this embodiment.
  • FIGS. 16B, 17B, and 18B show simulation results of the light receiving element for GE according to the second embodiment.
  • the “optical axis deviation amount” in FIGS. 16 to 18 indicates how much the optical axis is deviated from the center of the light receiving element 100 for GE.
  • “optical axis deviation amount 0” indicates that no optical axis deviation occurs.
  • the “optical axis deviation amount 0.05r” indicates that the optical axis is deviated from the center of the light receiving element 100 for GE by 0.05r.
  • the light receiving element 100 for GE according to the present embodiment changes the light receiving ratio when the gap is near 400 nm, but the influence of the optical axis shift is other than that in the region. I have not received it.
  • the light receiving element for GE according to the second embodiment see FIG. 16B
  • the light receiving ratio changes greatly due to the optical axis shift.
  • the light receiving element 100 for GE according to the present embodiment is not affected by the optical axis deviation.
  • the light receiving element for GE according to the second embodiment see FIG. 17B
  • the light receiving ratio changes greatly due to the optical axis shift.
  • the light receiving element 100 for GE according to the present embodiment is not affected by the optical axis deviation.
  • the light receiving element for GE according to the second embodiment see FIG. 18B
  • the light receiving ratio changes greatly due to the optical axis shift. Also in this case, it is difficult to keep the sensitivity constant because the gradient of the light reception ratio is greatly changed.
  • the light receiving element 100 for GE can eliminate or suppress the influence of the optical axis deviation, which is very advantageous in practice.
  • a fourth embodiment of the photodetector of the present invention will be described with reference to FIGS.
  • the fourth embodiment is the same as the configuration of the third embodiment except that the configurations of the light receiving element for GE and the gap error servo circuit are partially different. Accordingly, the description of the fourth embodiment that is the same as that of the third embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. The description will be given with reference.
  • FIG. 19 is a schematic diagram showing a light receiving element for GE according to the present embodiment having the same purpose as in FIG. Particularly in this embodiment, in order to eliminate the influence of the optical axis shift in the transition region (see FIG. 16A), a region corresponding to the second region 132 of the light receiving element for GE according to the third embodiment is divided. Yes.
  • the light receiving element 100 for GE includes, on its light receiving surface, a first detection area 141, a 21st detection area 142 surrounding the first detection area 141 from the outer edge side, and the 21st detection area 142.
  • the “21st detection area 142” and the “22nd detection area 143” according to the present embodiment are examples of the “second detection area” according to the present invention.
  • the first detection area 141 is a circular area with a radius r ⁇ S.
  • the twenty-first detection region 142 is an annular region having an inner diameter r ⁇ S and an outer diameter r + S.
  • the twenty-second detection region 143 is an annular region having an inner diameter r + S and an outer diameter (1 + ⁇ N) r + S.
  • the third detection region 144 is an annular region having an inner diameter (1 + ⁇ N) r + S and an outer diameter R ⁇ N ⁇ r ⁇ S.
  • the fourth detection region 145 is an annular region having an inner diameter R ⁇ N ⁇ r ⁇ S and an outer diameter R + S.
  • FIG. 20 is a block diagram showing the configuration of the light receiving element for GE and the gap error servo circuit according to the present embodiment having the same concept as in FIG.
  • the gap error servo circuit 30 outputs a signal indicating the amount of light received by the first detection region 141 output from the first detection region 141 and the first output output from the twenty-first detection region 142.
  • the speed at which the SIL assembly 209 approaches the optical disk 10 is controlled based on a signal indicating the sum of signals indicating the amount of light received by the 21 detection area 142.
  • the gap error servo circuit 30 also outputs a signal indicating the amount of light received by the 21st detection area 142 output from the 21st detection area 142 and the 22nd detection output from the 22nd detection area 143. Based on a signal indicating the sum of signals indicating the amount of received light received in the region 143, timing control for closing the servo loop is performed.
  • the gap error servo circuit 30 performs a collision avoidance process based on a signal indicating the amount of light received by the fourth detection area 145 output from the fourth detection area 145. Further, the gap error servo circuit 30 outputs a signal indicating the amount of light received by the 21st detection area 142 output from the 21st detection area 142 and the 22nd detection area output from the 22nd detection area 143. A signal indicating the amount of light received at 143, a signal indicating the amount of light received at the third detection region 144 output from the third detection region 144, and an output from the fourth detection region 145 A gap error signal is generated based on a signal indicating the sum of signals indicating the amount of light received by the fourth detection region 145.
  • FIG. 21 is another example of the simulation result showing the change in the light reception ratio in the transition region for each optical axis deviation amount having the same meaning as in FIG. 16.
  • the light receiving element 100 for GE is not affected by the optical axis shift even in the transition region.
  • the light reception ratio shown in FIG. 16 indicates the ratio of the light reception area to the total area of the first detection region 141 and the 21st detection region 142.
  • the change in the light reception ratio in this embodiment, the ratio of the light reception area to the total area of the twenty-first detection region 142 and the twenty-second detection region 143) in the vicinity of the gap of 200 nm is the same as in FIG. Further, the change in the light reception ratio in the excessively close area is the same as that in FIG.
  • the light receiving element 100 for GE can eliminate the influence of the optical axis deviation, and is very advantageous in practice.
  • the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S601).
  • the gap error servo circuit 30 detects the amount of light received by the first detection region 141 and the twenty-first detection region 142 of the light receiving element 100 for GE (step S602). Note that the detection of the amount of light received in the first detection area 141 and the second detection area 142 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S603). If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S603: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10. (Step S604). On the other hand, when it is determined that the detected sum of received light amounts is less than the threshold value (step S603: No), the gap error servo circuit 30 executes the process of step S601.
  • step S604 the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S605).
  • the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S606).
  • the detection of the amount of received light according to the 22nd detection region 143 may be executed continuously or periodically.
  • the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or less than a threshold value (step S607). When it is determined that the sum of the detected amounts of received light is equal to or less than the threshold (step S607: Yes), the gap error servo circuit 30 closes the gap servo loop (step S608). On the other hand, when it is determined that the detected sum of received light amounts is larger than the threshold (step S607: No), the gap error servo circuit 30 executes the process of step S605.
  • the “threshold value” in the process of step S603 according to the present embodiment is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is fixed in advance. It is set as a value or a variable value according to some physical quantity or parameter. Such a threshold is obtained by determining the relationship between the gap between the signal level indicating the sum of the amounts of light received in the first detection area 141 and the 21st detection area 142, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on established relationship.
  • the “threshold value” in the process of step S607 according to the present embodiment is a value that determines whether or not the gap servo loop is to be closed, and is a fixed value in advance or a variable value according to some physical quantity or parameter Set as Such a threshold value is obtained by calculating the relationship between the gap between the signal level indicating the amount of received light in the twenty-first detection region 142 and the twenty-second detection region 143, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on a relationship.
  • the collision avoidance process executed by the gap error servo circuit 30 will be described.
  • the collision avoidance process is executed mainly when the gap servo loop is in a closed state.
  • the gap error servo circuit 30 detects the amount of light received by the fourth detection region 145 of the GE light receiving element 100 (step S701). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S702).
  • step S702 When it is determined that the detected amount of received light is equal to or less than the threshold (step S702: Yes), the gap error servo circuit 30 executes a collision avoidance process (step S703). On the other hand, when it is determined that the detected amount of received light is greater than the threshold (step S702: No), the gap error servo circuit 30 is received by the 21st detection region 142 and the 22nd detection region 143 of the GE light receiving element 100. The amount of received light is detected (step S704).
  • the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S705). If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S705: Yes), the gap error servo circuit 30 turns off the gap servo (step S706). On the other hand, when it is determined that the detected sum of received light amounts is smaller than the threshold value (step S705: No), the gap error servo circuit 30 executes the process of step S701.
  • the “threshold value” in the process of step S702 according to the present modification may be set in the same manner as the “threshold value” in the process of step S402 according to the second embodiment described above.
  • the “threshold value” in the process of step S705 according to the present embodiment is a value that determines whether or not to turn off the gap servo, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter.
  • the Such a threshold is obtained by determining the relationship between the gap between the signal level indicating the sum of the received light amounts related to the twenty-first detection region 142 and the twenty-second detection region 143, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on established relationship.
  • the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S801).
  • step S803 the gap error servo circuit 30 detects the amount of light received by the first detection region 141 and the twenty-first detection region 142 of the light receiving element 100 for GE (step S802). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S803).
  • step S803: Yes If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S803: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10. (Step S804). On the other hand, when it is determined that the sum of the detected amounts of received light is less than the threshold (step S803: No), the gap error servo circuit 30 executes the process of step S801.
  • step S804 the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S805).
  • the gap error servo circuit 30 In parallel with the processing in step S805, the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S806). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or less than the first threshold value (step S807).
  • step S807: Yes When it is determined that the sum of the detected amounts of received light is equal to or less than the first threshold (step S807: Yes), the gap error servo circuit 30 causes the lens actuator to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10. 220 is controlled (step S808). On the other hand, when it is determined that the detected sum of received light amounts is larger than the first threshold (step S807: No), the gap error servo circuit 30 executes the process of step S805.
  • step S808 the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S809).
  • the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S810). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or smaller than a second threshold value (step S811).
  • step S811: Yes If it is determined that the sum of the detected amounts of received light is equal to or smaller than the second threshold (step S811: Yes), the gap error servo circuit 30 closes the gap servo loop (step S811). On the other hand, when it is determined that the detected sum of received light amounts is larger than the second threshold (step S811: No), the gap error servo circuit 30 executes the process of step S809.
  • the “threshold value” in the process of step S803 according to the present modification may be set similarly to the “threshold value” in the process of step S603 according to the fourth embodiment described above.
  • the “first threshold value” in step S807 is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is set as a fixed value in advance. Or a variable value according to some physical quantity or parameter. Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the sum of received light amounts and the gap in the twenty-first detection region 142 and the twenty-second detection region 143.
  • the lens actuator 220 when the lens actuator 220 is requested to stop, the distance that the SIL assembly 209 moves due to inertia and the received light amount equal to the gap, or the received light amount that is larger than the received light amount by a predetermined amount You only have to set it.
  • the “second threshold value” is a value that determines whether or not the gap servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining the relationship between the sum of received light amounts and the gap according to the twenty-first detection region 142 and the twenty-second detection region. Based on this, the received light amount corresponding to the distance at which the gap servo loop should be closed may be set.
  • Optical disk 20 Optical pickup 30 Gap error servo circuit 100 GE light receiving elements 111, 121, 131, 141 First detection areas 112, 122, 132 Second detection areas 123, 133, 144 Third detection areas 124, 134, 145 First 4 detection area 142 21st detection area 143 22nd detection area 201
  • Semiconductor laser 209 SIL assembly 210 SIL 220 Lens actuator

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  • Optics & Photonics (AREA)
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Abstract

A light detector (100) is provided in an optical pickup (20) wherein a lens (210) which can emit evanescent light to a recording medium (10) is arranged.  The light detector is provided with a first detecting region (111), which detects a first portion of reflection light reflected by a surface on a recording medium side of a lens on a light receiving surface of the light detector; and a second detecting region (112) which at least partially surrounds the first detecting region and detects a second portion of the reflection light different from the first portion.  When the first detecting region is set so that light equivalent to that obtained with an NA of less than 1 is received, the light detector can detect with high sensitivity that the lens is brought close to a near field region.

Description

光検出器及び光ピックアップ、並びに制御方法Photodetector, optical pickup, and control method
　本発明は、例えばエバネッセント光を介した情報の記録又は再生を行う装置等が備える光検出器、及び該光検出器を備える光ピックアップ、並びに該光ピックアップの制御方法の技術分野に関する。 The present invention relates to a technical field of a photodetector provided in an apparatus for recording or reproducing information via evanescent light, an optical pickup including the photodetector, and a method for controlling the optical pickup.
　エバネッセント光を介した情報の記録又は再生を行う装置では、情報の記録又は再生を行う際に、例えば固体浸レンズ（Ｓｏｌｉｄ　Ｉｍｍｅｒｓｉｏｎ　Ｌｅｎｓ：ＳＩＬ）等のレンズが、例えば光ディスク等の記録媒体から、例えば数十ｎｍ（ナノメートル）等の所定距離だけ離れた位置まで近づけられる。該装置では、光検出器から出力される信号に基づいて検出された、レンズと記録媒体との間の距離に応じて、レンズが制御されることが多い。 In an apparatus for recording or reproducing information via evanescent light, when recording or reproducing information, a lens such as a solid immersion lens (SIL) is used, for example, from a recording medium such as an optical disk. It can be brought close to a position separated by a predetermined distance such as several tens of nanometers (nanometers). In this apparatus, the lens is often controlled according to the distance between the lens and the recording medium detected based on the signal output from the photodetector.
　この種の光検出器として、例えば特許文献１には、中心部分に円形の不感帯が設けられた４分割光検出器が記載されている。ここでは特に、不感帯の径をビーム径の２分の１とすることで、検出感度を向上させる技術が記載されている。 As this type of photodetector, for example, Patent Document 1 describes a quadrant photodetector in which a circular dead zone is provided at the center. In particular, a technique for improving detection sensitivity by setting the dead zone diameter to one half of the beam diameter is described.
特開平６－６０４０４号公報Japanese Patent Laid-Open No. 6-60404
　しかしながら、特許文献１に記載の技術は、エバネッセント光の発生しないファーフィールド光学系を対象としており、エバネッセント光が発生するニアフィールド光学系には、直接適用することが困難であるという技術的問題点がある。 However, the technique described in Patent Document 1 is intended for a far-field optical system that does not generate evanescent light, and it is difficult to apply directly to a near-field optical system that generates evanescent light. There is.
　本発明は、例えば上記問題点に鑑みてなされたものであり、ニアフィールド光学系に用いることができ、且つ検出感度を向上させることができる光検出器及び光ピックアップ、並びに制御方法を提供することを課題とする。 The present invention has been made in view of the above problems, for example, and provides a photodetector, an optical pickup, and a control method that can be used in a near-field optical system and can improve detection sensitivity. Is an issue.
　本発明の光検出器は、上記課題を解決するために、記録媒体に対してエバネッセント光を発生可能なレンズを備える光ピックアップに設けられた光検出器であって、当該光検出器の受光面に、前記レンズの前記記録媒体側の面で反射された反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを備える。 In order to solve the above problems, the photodetector of the present invention is a photodetector provided in an optical pickup including a lens capable of generating evanescent light with respect to a recording medium, and includes a light receiving surface of the photodetector. And a first detection region for detecting a first portion of the reflected light reflected by the surface of the lens on the recording medium side, and at least partially surrounding the first detection region, which is different from the first portion. A second detection region for detecting a second portion of the reflected light.
　本発明の光検出器によれば、当該光検出器は、記録媒体に対してエバネッセント光を発生可能な、例えば固体浸レンズ等のレンズを備える光ピックアップに設けられている。即ち、当該光検出器は、該光ピックアップの一部を構成している。当該光検出器は、例えばレンズの記録媒体側の面で反射された反射光を受光し、該受光された光の光量に応じた信号を出力する。尚、当該光検出器は、レンズの記録媒体側の面で反射された反射光に加えて、記録媒体で反射された反射光も受光してよい。 According to the photodetector of the present invention, the photodetector is provided in an optical pickup including a lens such as a solid immersion lens capable of generating evanescent light with respect to a recording medium. That is, the photodetector constitutes a part of the optical pickup. The photodetector receives, for example, reflected light reflected from the surface of the lens on the recording medium side, and outputs a signal corresponding to the amount of the received light. The photodetector may receive reflected light reflected by the recording medium in addition to reflected light reflected by the surface of the lens on the recording medium side.
　当該光検出器は、該光検出器の受光面に、反射光の第１部分を検出する第１検出領域と、該第１検出領域を少なくとも部分的に包囲し、該第１部分とは異なる反射光の第２部分を検出する第２検出領域とを備える。即ち、当該光検出器は、分割型光検出器である。 The light detector includes a first detection region for detecting a first portion of reflected light on a light receiving surface of the light detector, and at least partially surrounds the first detection region, and is different from the first portion. A second detection region for detecting a second portion of the reflected light. That is, the photo detector is a split photo detector.
　尚、「反射光の第１部分」及び「反射光の第２部分」は、夫々、「反射光のうち第１検出領域に入射する光」及び「反射光のうち第２検出領域に入射する光」を意味する。 The “first portion of reflected light” and the “second portion of reflected light” are respectively “light incident on the first detection region of the reflected light” and “light incident on the second detection region of the reflected light”. It means “light”.
　第１検出領域は、例えば、当該光検出器上に形成される光のスポットの形状に合わせて円領域であってもよいし、環状領域又は円弧領域であってもよい。第２検出領域は、第１検出領域を部分的に包囲する、例えば円弧領域等であってもよいし、第１検出領域を包囲する、例えば環状領域等であってもよい。或いは、当該光検出器の受光面のうち第１検出領域以外の領域であってもよい。 The first detection area may be, for example, a circular area, an annular area, or an arc area in accordance with the shape of the light spot formed on the photodetector. The second detection region may be, for example, an arc region that partially surrounds the first detection region, or may be, for example, an annular region that surrounds the first detection region. Alternatively, it may be an area other than the first detection area on the light receiving surface of the photodetector.
　尚、第２検出領域に係る信号のＳ／Ｎ比（Ｓｉｇｎａｌ　ｔｏ　Ｎｏｉｓｅ　ｒａｔｉｏ）の観点から、第２検出領域は、環状領域又は円弧領域であることが望ましい。また、第２検出領域は、第１検出領域に隣接してなくてよい、即ち、第２検出領域と第１検出領域との間に空隙があってもよい。 In addition, from the viewpoint of the S / N ratio (Signal to Noise ratio) of the signal related to the second detection region, the second detection region is preferably an annular region or an arc region. Further, the second detection area may not be adjacent to the first detection area, that is, there may be a gap between the second detection area and the first detection area.
　本願発明者の研究によれば、以下の事が判明している。即ち、エバネッセント光を介した情報の記録又は再生を行うためには、記録媒体から、該記録媒体に照射される光の波長の２分の１以下の距離（例えば、数十ｎｍ）まで、レンズを近づけなければならない。この際、オーバーシュートやサーボの誤差等により、レンズが記録媒体に接触するおそれがある。レンズが記録媒体に接触することを回避するためには、例えばレンズの移動速度、サーボループをクローズ状態とするタイミング等を適切に設定する、即ち、レンズと記録媒体との間の距離に対応する信号を適切に検出する必要がある。 According to the inventor's research, the following has been found. That is, in order to perform recording or reproduction of information via evanescent light, the lens is moved from the recording medium to a distance equal to or less than a half of the wavelength of light irradiated on the recording medium (for example, several tens of nm). Must be close. At this time, the lens may come into contact with the recording medium due to overshoot or servo error. In order to avoid the lens coming into contact with the recording medium, for example, the moving speed of the lens, the timing when the servo loop is closed, etc. are set appropriately, that is, it corresponds to the distance between the lens and the recording medium. It is necessary to detect the signal appropriately.
　他方で、レンズと記録媒体との間の距離が縮まるにつれて、光検出器の受光面における光のスポットが変化する。具体的には例えば、レンズがニアフィールド領域に侵入する直前では、開口数（Ｎｕｍｅｒｉｃａｌ　Ａｐｅｒｔｕｒｅ：ＮＡ）が１未満に相当する光の光量が増加し、レンズがニアフィールド領域に侵入した直後では、ＮＡが１近傍に相当する光の光量が減少する。しかしながら、光検出器の受光面の全面で光量を検出する場合、前述の光量の変化量は小さく、例えばレンズがニアフィールド領域に侵入したか否かを判定することは困難である。 On the other hand, as the distance between the lens and the recording medium decreases, the light spot on the light receiving surface of the photodetector changes. Specifically, for example, immediately before the lens enters the near field region, the amount of light corresponding to a numerical aperture (NA) of less than 1 increases, and immediately after the lens enters the near field region, NA. The amount of light corresponding to the vicinity of 1 decreases. However, when the amount of light is detected over the entire light receiving surface of the photodetector, the amount of change in the amount of light is small, and it is difficult to determine, for example, whether the lens has entered the near field region.
　しかるに本発明では、受光面上に、反射光の第１部分を検出する第１検出領域と、該第１検出領域を少なくとも部分的に包囲し、第１部分とは異なる反射光の第２部分を検出する第２検出領域とを備える。即ち、本発明では、反射光を検出する検出領域を複数備えることにより、各検出領域における光量の変化量を相対的に大きくして、当該光検出器のＳ／Ｎ比（又は検出感度）を向上させることができる。 However, in the present invention, the first detection region for detecting the first portion of the reflected light on the light receiving surface, and the second portion of the reflected light that at least partially surrounds the first detection region and is different from the first portion. And a second detection region for detecting. That is, in the present invention, by providing a plurality of detection areas for detecting reflected light, the amount of change in the amount of light in each detection area is relatively increased, and the S / N ratio (or detection sensitivity) of the photodetector is increased. Can be improved.
　更に、第１検出領域を、ＮＡが１に相当する光が形成する円に対応する円領域又は環状領域とすれば、該第１検出領域で受光した光（即ち、ＮＡが１未満に相当する光）の光量が増加したことを条件に、レンズがニアフィールド領域に達することを検出することができる。また、第２検出領域の内縁を、ＮＡが１に相当する光が形成する円に対応する円とすれば、第２検出領域で受光した光（即ち、ＮＡが１以上に相当する光）の光量が減少したことを条件に、レンズがニアフィールド領域に侵入したことを検出することができる。 Furthermore, if the first detection region is a circular region or an annular region corresponding to a circle formed by light having NA corresponding to 1, light received in the first detection region (that is, NA corresponding to less than 1). It is possible to detect that the lens reaches the near field region on the condition that the amount of light) is increased. Further, if the inner edge of the second detection region is a circle corresponding to a circle formed by light having NA equal to 1, the light received in the second detection region (that is, light having NA equal to or greater than 1). It is possible to detect that the lens has entered the near field area on condition that the amount of light has decreased.
　以上の結果、本発明の光検出器によれば、比較的容易にして、レンズがニアフィールド領域に侵入したか否かを判定することができる。従って、例えばレンズの移動速度、サーボループをクローズ状態とするタイミング等を適切に設定することができる。 As a result, according to the photodetector of the present invention, it is possible to determine whether or not the lens has entered the near-field region with relative ease. Therefore, for example, the moving speed of the lens, the timing for closing the servo loop, and the like can be appropriately set.
　本発明の光検出器の一態様では、前記第１検出領域の外縁及び前記第２検出領域の内縁の各々は、前記第１検出領域の中心を共有する同心円の少なくとも一部を構成する。 In one aspect of the photodetector of the present invention, each of the outer edge of the first detection region and the inner edge of the second detection region forms at least a part of a concentric circle sharing the center of the first detection region.
　この態様によれば、比較的容易にして、当該光検出器の受光面における光のスポットの変化から、レンズと記録媒体との間の距離に対応する信号を検出することができる。尚、当該光検出器は、典型的には、当該光検出器に入射する光のスポットの中心と第１検出領域の中心とが一致するように設置される。 According to this aspect, a signal corresponding to the distance between the lens and the recording medium can be detected from the change of the light spot on the light receiving surface of the photodetector relatively easily. Note that the photodetector is typically installed so that the center of the spot of light incident on the photodetector coincides with the center of the first detection region.
　本発明の光検出器の他の態様では、前記受光面上に、前記第２検出領域を少なくとも部分的に包囲し、前記第１及び第２部分とは異なる前記反射光の第３部分を検出する第３検出領域と、前記第３検出領域を少なくとも部分的に包囲し、前記第１乃至第３部分とは異なる前記反射光の第４部分を検出する第４検出領域とを更に備える。 In another aspect of the photodetector of the present invention, on the light receiving surface, the second detection region is at least partially surrounded, and a third portion of the reflected light different from the first and second portions is detected. And a fourth detection region that at least partially surrounds the third detection region and detects a fourth portion of the reflected light different from the first to third portions.
　この態様によれば、当該光検出器は、第１検出領域及び第２検出領域に加えて、該第２検出領域を少なくとも部分的に包囲し、第１及び第２部分とは異なる反射光の第３部分を検出する第３検出領域と、該第３検出領域を少なくとも部分的に包囲し、第１乃至第３部分とは異なる反射光の第４部分を検出する第４検出領域とを備える。 According to this aspect, in addition to the first detection region and the second detection region, the photodetector at least partially surrounds the second detection region, and reflects light that is different from the first and second portions. A third detection region for detecting the third portion; and a fourth detection region for at least partially surrounding the third detection region and detecting a fourth portion of reflected light different from the first to third portions. .
　尚、「反射光の第３部分」及び「反射光の第４部分」は、夫々、「反射光のうち第３検出領域に入射する光」及び「反射光のうち第４検出領域に入射する光」を意味する。 The “third portion of reflected light” and the “fourth portion of reflected light” are respectively “light entering the third detection region of the reflected light” and “light entering the fourth detection region of the reflected light”. It means “light”.
　第３検出領域は、第２検出領域を部分的に包囲する、例えば円弧領域等であってもよいし、第２検出領域を包囲する、例えば環状領域等であってもよい。同様に、第４検出領域は、第３検出領域を部分的に包囲する、例えば円弧領域等であってもよいし、第３検出領域を包囲する、例えば環状領域等であってもよい。尚、第４検出領域は、当該光検出器の受光面のうち第１乃至第３検出領域以外の領域であってもよい。 The third detection region may be, for example, an arc region that partially surrounds the second detection region, or may be, for example, an annular region that surrounds the second detection region. Similarly, the fourth detection region may be, for example, an arc region that partially surrounds the third detection region, or may be, for example, an annular region that surrounds the third detection region. The fourth detection region may be a region other than the first to third detection regions on the light receiving surface of the photodetector.
　ここで、第４検出領域を、当該光検出器の受光面上のスポットの最外周に対応する外縁と、該外縁から所定距離だけ内側の内縁とを有する環状領域又は該環状領域の一部である円弧領域とすれば、第４検出領域で受光した光の光量が減少したことを条件に、レンズが記録媒体に接触するおそれがある程近づいたこと（即ち、過接近状態であること）を検出することができる。この結果、比較的容易にして、レンズが記録媒体に接触することを回避することができる。 Here, the fourth detection region is an annular region having an outer edge corresponding to the outermost periphery of the spot on the light receiving surface of the photodetector and an inner edge a predetermined distance from the outer edge or a part of the annular region. If a certain arc region is used, the fact that the lens has come close to contact with the recording medium on the condition that the amount of light received in the fourth detection region has decreased (that is, it is in an excessively close state). Can be detected. As a result, it is possible to avoid the lens from coming into contact with the recording medium relatively easily.
　尚、本願発明者の研究によれば、過接近状態では、光検出器の受光面における光のスポットの最外周近傍の光量が減少することが判明している。 In addition, according to the research by the inventors of the present application, it has been found that the amount of light in the vicinity of the outermost periphery of the light spot on the light receiving surface of the photodetector decreases in an excessively close state.
　この態様では、前記第１検出領域の外縁、前記第２検出領域の外縁及び前記第３検出領域の外縁の各々は、前記第１検出領域の中心を共有する同心円の少なくとも一部を構成してよい。 In this aspect, each of the outer edge of the first detection region, the outer edge of the second detection region, and the outer edge of the third detection region constitutes at least a part of a concentric circle sharing the center of the first detection region. Good.
　このように構成すれば、比較的容易にして、当該光検出器の受光面における光のスポットの変化から、レンズと記録媒体との間の距離に対応する信号を検出することができる。 With this configuration, a signal corresponding to the distance between the lens and the recording medium can be detected from the change in the light spot on the light receiving surface of the photodetector relatively easily.
　本発明の光ピックアップは、上記課題を解決するために、記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段と、前記光検出器から出力される信号に基づいて、前記レンズを駆動するように前記駆動手段を制御する制御手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する。 In order to solve the above problems, an optical pickup according to the present invention includes a light source that irradiates a recording medium with light, a lens that is disposed in an optical path of the irradiated light, and that can generate evanescent light with respect to the recording medium. , A photodetector for receiving at least reflected light reflected from the surface of the lens on the recording medium side of the irradiated light, driving means for driving the lens, and output from the photodetector Control means for controlling the drive means to drive the lens based on a signal, and the light detector detects a first portion of the reflected light on a light receiving surface of the light detector. And a second detection region that at least partially surrounds the first detection region and detects a second portion of the reflected light different from the first portion.
　本発明の光ピックアップによれば、例えば半導体レーザ等である光源は、例えば光ディスク等の記録媒体に光を照射する。記録媒体に対してエバネッセント光を発生可能な、例えば固体浸レンズ等であるレンズは、照射された光の光路に配置される。光検出器は、照射された光のうちレンズの記録媒体側の面又は記録媒体で反射された特定の偏光状態の反射光を受光する。ここで、記録媒体で反射された特定の偏光状態の反射光とは、ＮＡが1未満の光のうち、入射角の大きな光に係る反射光の偏光状態が、ｓ偏光成分とｐ偏光成分との反射率の違いに起因して反射光のｓ偏光成分とｐ偏光成分との間に振幅差が生じることにより、レンズの記録媒体側の面で反射された光と同じ偏光状態になった反射光を指す。 According to the optical pickup of the present invention, a light source such as a semiconductor laser irradiates a recording medium such as an optical disk with light. A lens, such as a solid immersion lens, that can generate evanescent light with respect to the recording medium is disposed in the optical path of the irradiated light. The photodetector receives reflected light of a specific polarization state reflected by the surface of the lens on the recording medium side or the recording medium of the irradiated light. Here, the reflected light of a specific polarization state reflected by the recording medium is the polarization state of the reflected light related to light having a large incident angle out of light having an NA of less than 1, and the s-polarization component and the p-polarization component. The difference in amplitude between the s-polarized component and the p-polarized component of the reflected light due to the difference in reflectance between the reflected light and the reflected light in the same polarization state as the light reflected on the surface of the lens on the recording medium side Point to light.
　光検出器は、該光検出器の受光面上に、反射光の第１部分を検出する第１検出領域と、該第１検出領域を少なくとも部分的に包囲し、第１部分とは異なる反射光の第２部分を検出する第２検出領域とを有している。 The photodetector has a first detection region for detecting the first portion of the reflected light on the light receiving surface of the photodetector, and at least partially surrounds the first detection region, and is different in reflection from the first portion. And a second detection region for detecting a second portion of light.
　例えばレンズアクチュエータ等である駆動手段は、レンズを駆動可能である。制御手段は、光検出器から出力される信号に基づいて、レンズを駆動するように駆動手段を制御する。具体的には例えば、第１検出領域をＮＡが１に相当する光が形成する円に対応する円領域として、該第１検出領域で受光した光の光量が増加したことを条件に、制御手段は、レンズの記録媒体に近づく速度が低下するように駆動手段を制御する。或いは、第２検出領域の内縁を、ＮＡが１に相当する光が形成する円に対応する円とし、第２検出領域で受光した光の光量が減少したことを条件に、制御手段は、サーボループをクローズ状態として、レンズが記録媒体に追従するように駆動手段を制御する。 For example, a driving means such as a lens actuator can drive the lens. The control unit controls the driving unit to drive the lens based on the signal output from the photodetector. Specifically, for example, if the first detection area is a circular area corresponding to a circle formed by light corresponding to NA of 1, the control means is provided on the condition that the amount of light received by the first detection area has increased. Controls the driving means so that the speed of the lens approaching the recording medium decreases. Alternatively, on the condition that the inner edge of the second detection area is a circle corresponding to the circle formed by the light whose NA is equal to 1, and the light quantity of the light received in the second detection area is reduced, the control means The driving means is controlled so that the lens follows the recording medium with the loop closed.
　以上の結果、本発明の光ピックアップによれば、例えばレンズの移動速度、サーボループをクローズ状態とするタイミング等を適切に設定することができる。 As a result, according to the optical pickup of the present invention, for example, the moving speed of the lens, the timing when the servo loop is closed, and the like can be appropriately set.
　本発明の光ピックアップの一態様では、前記第１検出領域の外縁は、前記反射光のうち開口数が１に相当する光が前記受光面に形成する円の外縁に対応する。 In one aspect of the optical pickup of the present invention, the outer edge of the first detection region corresponds to the outer edge of a circle formed on the light receiving surface by light corresponding to a numerical aperture of 1 among the reflected light.
　この態様によれば、第１検出領域で受光した光の光量に基づいて、比較的容易にして、レンズがニアフィールド領域に達するか否かを判定することができる。 According to this aspect, it is possible to determine whether or not the lens reaches the near field region relatively easily based on the light amount of the light received in the first detection region.
　或いは、本発明の光ピックアップの他の態様では、前記第２検出領域の内縁は、前記反射光のうち開口数が１に相当する光が前記受光面に形成する円の外縁に対応する。 Alternatively, in another aspect of the optical pickup of the present invention, the inner edge of the second detection region corresponds to the outer edge of a circle formed on the light receiving surface by light corresponding to a numerical aperture of 1 among the reflected light.
　この態様によれば、第２検出領域で受光した光の光量に基づいて、比較的容易にして、適切にサーボループをクローズ状態とすることができる。 According to this aspect, the servo loop can be appropriately closed in a relatively easy manner based on the amount of light received in the second detection region.
　本発明の第１の制御方法は、上記課題を解決するために、記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する光ピックアップの制御方法であって、前記第１検出領域の受光量に応じて、前記レンズの前記記録媒体に近づく速度を低下させるように前記駆動手段を制御する減速工程を備える。 In order to solve the above problems, the first control method of the present invention is arranged in a light source for irradiating light on a recording medium and an optical path of the irradiated light, and can generate evanescent light on the recording medium An optical lens, a photodetector for receiving reflected light reflected by at least a surface of the lens on the recording medium side, and a driving means capable of driving the lens, the photodetector Includes a first detection region for detecting a first portion of the reflected light on a light receiving surface of the photodetector, and at least partially surrounds the first detection region, and the reflected light different from the first portion. And a second detection area for detecting the second portion of the optical pickup, wherein the lens approaches the recording medium according to the amount of light received by the first detection area so as to reduce the speed of the lens approaching the recording medium. Deceleration controlling the drive means It provided with a degree.
　本発明の第１の制御方法によれば、減速工程において、第１検出領域の受光量に応じて、レンズの記録媒体に近づく速度を低下させるように駆動手段が制御される。この結果、駆動手段に対し停止要求があった場合に、慣性によりレンズが移動する距離を比較的短くすることができる。従って、レンズが記録媒体に衝突することを回避することができる。 According to the first control method of the present invention, in the deceleration process, the driving means is controlled so as to reduce the speed of the lens approaching the recording medium in accordance with the amount of light received in the first detection area. As a result, when the drive unit is requested to stop, the distance that the lens moves due to inertia can be made relatively short. Therefore, it is possible to avoid the lens from colliding with the recording medium.
　本発明の第１の制御方法の一態様では、前記減速工程の後、前記第２検出領域の受光量に応じて、サーボループをクローズ状態とするクローズ工程を更に備える。 In one aspect of the first control method of the present invention, the method further includes a closing step of closing the servo loop in accordance with the amount of light received in the second detection region after the deceleration step.
　この態様によれば、減速工程の後、クローズ工程において、第２検出領域の受光量に応じて、サーボループがクローズ状態とされる。ここで、第２検出領域の内縁を、ＮＡが１に相当する光が形成する円に対応する円とすれば、第２検出領域で受光した光の光量に基づいてレンズがニアフィールド領域に侵入したことを検出することができる。この結果、ニアフィールド領域において、適切にサーボループをクローズ状態とすることができる。 According to this aspect, after the deceleration process, in the closing process, the servo loop is closed according to the amount of light received in the second detection region. Here, if the inner edge of the second detection region is a circle corresponding to a circle formed by light having NA equal to 1, the lens enters the near field region based on the amount of light received by the second detection region. Can be detected. As a result, the servo loop can be appropriately closed in the near field region.
　或いは、本発明の第１の制御方法の他の態様では、前記減速工程の後、前記第２検出領域の受光量が第１閾値より小さいことを条件に、前記レンズの前記記録媒体に近づく速度をより低下させるように前記駆動手段を制御する第２減速工程と、前記第２減速工程の後、前記第２検出領域の受光量が第２閾値より小さいことを条件に、サーボループをクローズ状態とするクローズ工程とを更に備える。 Alternatively, in another aspect of the first control method of the present invention, after the deceleration step, the speed of the lens approaching the recording medium on condition that the amount of light received in the second detection region is smaller than a first threshold value. A second deceleration step for controlling the driving means so as to further decrease the servo loop, and after the second deceleration step, the servo loop is closed on condition that the amount of light received in the second detection region is smaller than a second threshold value And a closing step.
　この態様によれば、減速工程の後、第２減速工程において、第２検出領域の受光量が第１閾値より小さいことを条件に、レンズの記録媒体に近づく速度をより低下させるように駆動手段が制御される。第２減速工程の後、クローズ工程において、第２検出領域の受光量が第２閾値より小さいことを条件にサーボループがクローズ状態とされる。このため、レンズと記録媒体との距離がより短い状態で、サーボループをクローズ状態とすることができる。 According to this aspect, after the deceleration process, in the second deceleration process, on the condition that the amount of light received in the second detection area is smaller than the first threshold value, the driving unit is configured to further reduce the speed of the lens approaching the recording medium. Is controlled. After the second deceleration step, in the closing step, the servo loop is closed on the condition that the amount of light received in the second detection region is smaller than the second threshold value. For this reason, the servo loop can be closed while the distance between the lens and the recording medium is shorter.
　本発明に係る「第１閾値」は、レンズの記録媒体に近づく速度をより低下させるように駆動手段を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第１閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域の受光量と、レンズ及び記録媒体間の距離との関係を求め、該求められた関係に基づいて、駆動手段に対し停止要求があった際に慣性によりレンズが移動する距離と、レンズ及び記録媒体間の距離とが等しくなる受光量として、又は該受光量よりも所定量だけ大きい受光量として設定すればよい。 The “first threshold value” according to the present invention is a value that determines whether or not to control the driving unit so as to further reduce the speed at which the lens approaches the recording medium, and is set in advance as a fixed value or to some physical quantity or parameter. It is set as a variable value. Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining a relationship between the amount of light received in the second detection region and the distance between the lens and the recording medium, and based on the obtained relationship. When the drive unit is requested to stop, the distance that the lens moves due to inertia and the distance between the lens and the recording medium are set equal to the received light amount, or the received light amount that is larger than the received light amount by a predetermined amount. do it.
　本発明に係る「第２閾値」は、サーボループをクローズ状態とするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第２閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域の受光量と、レンズ及び記録媒体間の距離との関係を求め、該求められた関係に基づいて、サーボループをクローズ状態とすべき距離に対応する受光量として設定すればよい。 The “second threshold value” according to the present invention is a value that determines whether or not the servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining a relationship between the amount of light received in the second detection region and the distance between the lens and the recording medium, and based on the obtained relationship. The light reception amount corresponding to the distance at which the servo loop should be closed may be set.
　本発明の第２の制御方法は、上記課題を解決するために、記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する光ピックアップの制御方法であって、前記第１検出領域の受光量と前記第２検出領域の受光量との差分を演算する演算工程と、前記演算された差分が一旦減少した後に増加したことを条件に、前記レンズの前記記録媒体に近づく速度を低下させるように前記駆動手段を制御する減速工程とを備える。 In order to solve the above problems, the second control method of the present invention is arranged in a light source for irradiating light to the recording medium and an optical path of the irradiated light, and can generate evanescent light to the recording medium An optical lens, a photodetector for receiving reflected light reflected from at least the surface of the lens on the recording medium side, and a driving means capable of driving the lens. A detector at least partially surrounds the first detection region and a first detection region for detecting the first portion of the reflected light on a light receiving surface of the photodetector, and the reflection is different from the first portion; A method for controlling an optical pickup having a second detection area for detecting a second portion of light, wherein the calculation step calculates a difference between the amount of light received in the first detection area and the amount of light received in the second detection area; The calculated difference once decreases On condition that increased after, and a reduction step for controlling the drive means to reduce the speed of approaching to the recording medium of the lens.
　本発明の第２の制御方法によれば、演算工程において、第１検出領域の受光量と第２検出領域の受光量との差分（本発明では、典型的には、第２検出領域の受光量から第１検出領域の受光量を引くことによって得られる差分）が演算される。尚、演算工程は、例えば所定期間毎に周期的に実施される。減速工程において、演算された差分が一旦減少した後に増加したことを条件に、レンズの記録媒体に近づく速度を低下させるように駆動手段が制御される。 According to the second control method of the present invention, in the calculation step, the difference between the received light amount of the first detection region and the received light amount of the second detection region (in the present invention, typically, the received light of the second detection region). The difference obtained by subtracting the amount of light received in the first detection area from the amount is calculated. Note that the calculation step is periodically performed, for example, every predetermined period. In the deceleration step, the driving means is controlled so as to reduce the speed of the lens approaching the recording medium on condition that the calculated difference once increases and then increases.
　この結果、上述した本発明の第１の制御方法と同様に、駆動手段に対し停止要求があった場合に、慣性によりレンズが移動する距離を比較的短くすることができる。従って、レンズが記録媒体に衝突することを回避することができる。 As a result, similar to the above-described first control method of the present invention, when the drive unit is requested to stop, the distance that the lens moves due to inertia can be made relatively short. Therefore, it is possible to avoid the lens from colliding with the recording medium.
　尚、本願発明者の研究によれば、レンズがニアフィールド領域に侵入する直前では、第１検出領域の受光量が一旦増加し、その後減少することが判明している。このため、第２検出領域の受光量から第１検出領域の受光量を引くことによって得られる差分は、レンズがニアフィールド領域に侵入する直前に、一旦減少した後に増加することとなる。 Incidentally, according to the research of the present inventors, it has been found that the amount of light received in the first detection region increases once and then decreases immediately before the lens enters the near field region. For this reason, the difference obtained by subtracting the amount of light received in the first detection region from the amount of light received in the second detection region will increase after once decreasing immediately before the lens enters the near field region.
　本発明の第３の制御方法は、上記課題を解決するために、記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域と、前記第２検出領域を少なくとも部分的に包囲し、前記第１及び第２部分とは異なる前記反射光の第３部分を検出する第３検出領域と、前記第３検出領域を少なくとも部分的に包囲し、前記第１乃至第３部分とは異なる前記反射光の第４部分を検出する第４検出領域とを有する光ピックアップの制御方法であって、前記第４検出領域の受光量に応じて、前記レンズが前記記録媒体に衝突しないように前記駆動手段を制御する衝突回避工程を備える。 In order to solve the above-described problem, the third control method of the present invention is arranged in a light source for irradiating the recording medium with light and an optical path of the irradiated light, and can generate evanescent light with respect to the recording medium. An optical lens, a photodetector for receiving reflected light reflected from at least the surface of the lens on the recording medium side, and a driving means capable of driving the lens. A detector at least partially surrounds the first detection region and a first detection region for detecting the first portion of the reflected light on a light receiving surface of the photodetector, and the reflection is different from the first portion; A second detection region for detecting a second portion of light and a third detection for detecting a third portion of the reflected light that at least partially surrounds the second detection region and is different from the first and second portions. Region and at least part of the third detection region And a fourth detection region for detecting the fourth portion of the reflected light that is different from the first to third portions, wherein the amount of received light in the fourth detection region is Accordingly, there is provided a collision avoidance step for controlling the driving means so that the lens does not collide with the recording medium.
　本発明の第３の制御方法によれば、衝突回避工程において、第４検出領域の受光量に応じて、レンズが記録媒体に衝突しないように駆動手段が制御される。具体的には例えば、レンズを記録媒体から遠ざけるように駆動手段が制御される。この結果、比較的容易にして、レンズが記録媒体に接触することを回避することができる。 According to the third control method of the present invention, in the collision avoidance step, the driving means is controlled so that the lens does not collide with the recording medium in accordance with the amount of light received in the fourth detection area. Specifically, for example, the driving unit is controlled so as to move the lens away from the recording medium. As a result, it is possible to avoid the lens from coming into contact with the recording medium relatively easily.
　本発明の作用及び他の利得は次に説明する実施するための形態から明らかにされる。 The operation and other advantages of the present invention will be clarified from the embodiments to be described below.
第１実施形態に係る光ピックアップの構成を示すブロック図である。It is a block diagram which shows the structure of the optical pick-up concerning 1st Embodiment. 第１実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。It is a block diagram which shows the structure of the light receiving element for GE which concerns on 1st Embodiment, and a gap error servo circuit. 受光比とギャップとの関係を示すシミュレーション結果の一例である。It is an example of the simulation result which shows the relationship between a light reception ratio and a gap. 第１実施形態に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on 1st Embodiment performs. 第１実施形態に係るＧＥ用受光素子の変形例を示す模式図である。It is a schematic diagram which shows the modification of the light receiving element for GE which concerns on 1st Embodiment. 第１実施形態の変形例に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。It is a block diagram which shows the structure of the light receiving element for GE and the gap error servo circuit which concern on the modification of 1st Embodiment. 受光比とギャップとの関係を示すシミュレーション結果の他の例である。It is another example of the simulation result which shows the relationship between a light reception ratio and a gap. 第１実施形態の変形例に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on the modification of 1st Embodiment performs. 第２実施形態に係るＧＥ用受光素子を示す模式図である。It is a schematic diagram which shows the light receiving element for GE which concerns on 2nd Embodiment. 第２実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。It is a block diagram which shows the structure of the light receiving element for GE which concerns on 2nd Embodiment, and a gap error servo circuit. 受光比とギャップとの関係を示すシミュレーション結果の他の例である。It is another example of the simulation result which shows the relationship between a light reception ratio and a gap. 第２実施形態に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on 2nd Embodiment performs. 第２実施形態に係るギャップエラーサーボ回路が、ギャップサーボループクローズ中に実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit based on 2nd Embodiment performs during a gap servo loop close. 第２実施形態の変形例に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on the modification of 2nd Embodiment performs. 第３実施形態に係るＧＥ用受光素子を示す模式図である。It is a schematic diagram which shows the light receiving element for GE which concerns on 3rd Embodiment. 遷移領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。It is an example of the simulation result which showed the change of the light reception ratio in a transition area | region for every deviation | shift amount of an optical axis. ギャップが２００ｎｍ近傍である場合の受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。It is an example of the simulation result which showed the change of the light reception ratio in case a gap is 200 nm vicinity for every deviation | shift amount of an optical axis. 過接近領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。It is an example of the simulation result which showed the change of the light reception ratio in the excessive approach area | region for every deviation | shift amount of an optical axis. 第４実施形態に係るＧＥ用受光素子を示す模式図である。It is a schematic diagram which shows the light receiving element for GE which concerns on 4th Embodiment. 第４実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。It is a block diagram which shows the structure of the light receiving element for GE which concerns on 4th Embodiment, and a gap error servo circuit. 遷移領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の他の例である。It is another example of the simulation result which showed the change of the light reception ratio in a transition area | region for every deviation | shift amount of an optical axis. 第４実施形態に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on 4th Embodiment performs. 第４実施形態に係るギャップエラーサーボ回路が、ギャップサーボループクローズ中に実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit based on 4th Embodiment performs during a gap servo loop close. 第４実施形態の変形例に係るギャップエラーサーボ回路が実行するレンズアクチュエータの制御方法を示すフローチャートである。It is a flowchart which shows the control method of the lens actuator which the gap error servo circuit which concerns on the modification of 4th Embodiment performs.
　以下、本発明の光検出器及び光ピックアップ、並びに制御方法に係る実施形態を図面に基づいて説明する。 Hereinafter, embodiments of a photodetector, an optical pickup, and a control method according to the present invention will be described with reference to the drawings.
　＜第１実施形態＞
　本発明の光検出器に係る第１実施形態を、図１乃至図４を参照して説明する。 <First Embodiment>
A first embodiment of the photodetector of the present invention will be described with reference to FIGS.
　先ず、本実施形態に係る光検出器を備える光ピックアップの構成について、図１を参照して説明する。図１は、本実施形態に係る光ピックアップの構成を示すブロック図である。尚、図中の点線Ｌは光路を示している。 First, the configuration of an optical pickup including the photodetector according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the optical pickup according to the present embodiment. Note that a dotted line L in the figure indicates an optical path.
　図１において、光ピックアップ２０は、半導体レーザ２０１、コリメータレンズ２０２、回折格子２０３、無偏光ビームスプリッタ２０４、偏光ビームスプリッタ２０５、ビーム拡大器２０６、４分の１波長板２０７、ミラー２０８、固体浸レンズ２１０（以下、適宜“ＳＩＬ”と称する）を有するＳＩＬアッセンブリ２０９、レンズ２１１及び２１３、ＲＦ（Ｒａｄｉｏ　Ｆｒｅｑｕｅｎｃｙ）用受光素子２１２、ＧＥ（Ｇａｐ　Ｅｒｒｏｒ）用受光素子１００、フロントモニタ（ＦＭ）２１４、レンズアクチュエータ２２０並びにギャップエラー（ＧＥ）サーボ回路３０を備えて構成されている。 In FIG. 1, an optical pickup 20 includes a semiconductor laser 201, a collimator lens 202, a diffraction grating 203, a non-polarizing beam splitter 204, a polarizing beam splitter 205, a beam expander 206, a quarter-wave plate 207, a mirror 208, a solid immersion. SIL assembly 209 having lens 210 (hereinafter referred to as “SIL” as appropriate), lenses 211 and 213, light receiving element 212 for RF (Radio Frequency), light receiving element 100 for GE (Gap Error), front monitor (FM) 214, A lens actuator 220 and a gap error (GE) servo circuit 30 are provided.
　本実施形態に係る光ピックアップ２０は、例えば、エバネッセント光を介して光ディスク１０に情報の記録を行う又は光ディスク１０に記録された情報の再生を行う、記録再生装置に搭載される。 The optical pickup 20 according to the present embodiment is mounted on a recording / reproducing apparatus that records information on the optical disc 10 or reproduces information recorded on the optical disc 10 via evanescent light, for example.
　半導体レーザ２０１から出射された光Ｌは、コリメータレンズ２０２を介して回折格子２０３に入射する。該回折格子２０３によって複数の回折光に分離された光Ｌは、無偏光ビームスプリッタ２０４、偏光ビームスプリッタ２０５、ビーム拡大器２０６、４分の１波長２０７及びミラー２０８を介して、ＳＩＬアッセンブリ２０９に入射する。尚、半導体レーザ２０１からは、例えば波長４００ｎｍの光Ｌが出射される。 The light L emitted from the semiconductor laser 201 is incident on the diffraction grating 203 via the collimator lens 202. The light L separated into a plurality of diffracted lights by the diffraction grating 203 is sent to the SIL assembly 209 via the non-polarizing beam splitter 204, the polarizing beam splitter 205, the beam expander 206, the quarter wavelength 207, and the mirror 208. Incident. For example, light L having a wavelength of 400 nm is emitted from the semiconductor laser 201.
　尚、無偏光ビームスプリッタ２０５に入射した光Ｌの一部は、フロントモニタ２１４によって受光される。該フロントモニタ２１４には、例えば、図示しないパワー比較回路等が電気的に接続されている。該パワー比較回路では、フロントモニタ２１４から送信された光Ｌの強度を示す信号と基準信号とが比較される。パワー比較回路は、該比較の結果を示す信号を、図示しないレーザドライバに送信する。該レーザドライバは、送信された信号に基づいて半導体レーザ２０１の出力を制御する。 Note that part of the light L incident on the non-polarizing beam splitter 205 is received by the front monitor 214. For example, a power comparison circuit (not shown) is electrically connected to the front monitor 214. In the power comparison circuit, a signal indicating the intensity of the light L transmitted from the front monitor 214 is compared with a reference signal. The power comparison circuit transmits a signal indicating the result of the comparison to a laser driver (not shown). The laser driver controls the output of the semiconductor laser 201 based on the transmitted signal.
　ＳＩＬ２１０に入射した光Ｌの一部は、エバネッセント光として光ディスク１０に出射され、他の一部はＳＩＬ２１０の底部で反射される。光ディスク１０からの反射光は、再びＳＩＬ２１０に入射し、ミラー２０８、４分の１波長板２０７及びビーム拡大器２０６を介して、偏光ビームスプリッタ２０５に入射する。ここで、半導体レーザ２０１から出射される光Ｌの偏光方向と、光ディスク１０からの反射光の偏光方向とは互いに９０度異なっているため、光ディスク１０からの反射光は、レンズ２１１を介してＲＦ用受光素子２１２に入射する。尚、ＲＦ用受光素子２１２は、例えば２分割又は４分割受光素子である。 A part of the light L incident on the SIL 210 is emitted to the optical disc 10 as evanescent light, and the other part is reflected on the bottom of the SIL 210. The reflected light from the optical disk 10 enters the SIL 210 again, and enters the polarization beam splitter 205 via the mirror 208, the quarter-wave plate 207, and the beam expander 206. Here, since the polarization direction of the light L emitted from the semiconductor laser 201 and the polarization direction of the reflected light from the optical disk 10 are different from each other by 90 degrees, the reflected light from the optical disk 10 passes through the lens 211 and is RF. Incident light receiving element 212. The RF light receiving element 212 is, for example, a two-divided or four-divided light receiving element.
　尚、ＲＦ用受光素子２１２には、例えば、図示しないＲＦ信号生成回路が電気的に接続されており、ＲＦ用受光素子２１２に入射した反射光に起因するＲＦ信号が生成される。該生成されたＲＦ信号は、図示しない、例えば復調回路、エラー訂正回路、デコード回路等を含んで構成される再生信号処理部に送信される。或いは、図示しないトラッキングサーボ回路に送信される。該トラッキングサーボ回路によってトラッキングエラー信号が生成され、該生成されたトラッキングエラー信号に基づいて、光ディスク１０上のスポットの位置が所定の位置となるように、レンズアクチュエータ２２０が制御される。 Note that, for example, an RF signal generation circuit (not shown) is electrically connected to the RF light receiving element 212, and an RF signal caused by reflected light incident on the RF light receiving element 212 is generated. The generated RF signal is transmitted to a reproduction signal processing unit (not shown) including, for example, a demodulation circuit, an error correction circuit, a decoding circuit, and the like. Alternatively, it is transmitted to a tracking servo circuit (not shown). A tracking error signal is generated by the tracking servo circuit, and the lens actuator 220 is controlled based on the generated tracking error signal so that the position of the spot on the optical disc 10 becomes a predetermined position.
　他方、ＳＩＬ２１０の底部で反射した光は、ミラー２０８、４分の１波長板２０７、ビーム拡大器２０６及び偏光ビームスプリッタ２０５を介して、無偏光ビームスプリッタ２０４に入射する。ＳＩＬ２１０の底部で反射した光の一部は、レンズ２１３を介して、ＧＥ用受光素子１００に入射する。 On the other hand, the light reflected at the bottom of the SIL 210 enters the non-polarizing beam splitter 204 through the mirror 208, the quarter-wave plate 207, the beam expander 206, and the polarizing beam splitter 205. A part of the light reflected from the bottom of the SIL 210 enters the GE light receiving element 100 through the lens 213.
　ＧＥ用受光素子２１４には、ギャップエラーサーボ回路３０が電気的に接続されている。該ギャップエラーサーボ回路３０は、ＳＩＬ２１０の底部及び光ディスク１０の表面間の距離（即ち、ギャップ）が所定距離となるように、レンズアクチュエータ２２０を制御する。 The gap error servo circuit 30 is electrically connected to the light receiving element 214 for GE. The gap error servo circuit 30 controls the lens actuator 220 so that the distance between the bottom of the SIL 210 and the surface of the optical disk 10 (that is, the gap) is a predetermined distance.
　尚、本実施形態に係る「光ディスク１０」、「ギャップエラーサーボ回路３０」、「ＧＥ用受光素子１００」、「半導体レーザ２０１」、「ＳＩＬ２１０」及び「レンズアクチュエータ２２０」は、夫々、本発明に係る「記録媒体」、「制御手段」、「光検出器」、「光源」、「レンズ」及び「駆動手段」の一例である。また、本実施形態に係る「ＳＩＬ２１０の底部」は、本発明に係る「レンズの記録媒体側の面」の一例である。 The “optical disk 10”, “gap error servo circuit 30”, “GE light receiving element 100”, “semiconductor laser 201”, “SIL 210”, and “lens actuator 220” according to the present embodiment are respectively included in the present invention. This is an example of the “recording medium”, “control unit”, “photodetector”, “light source”, “lens”, and “driving unit”. The “bottom portion of the SIL 210” according to the present embodiment is an example of the “surface on the recording medium side of the lens” according to the present invention.
　次に、ＧＥ用受光素子１００及びギャップエラーサーボ回路３０について、図２を参照して説明する。図２は、本実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。 Next, the GE light receiving element 100 and the gap error servo circuit 30 will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of a light receiving element for GE and a gap error servo circuit according to the present embodiment.
　図２において、先ず、ＧＥ用受光素子１００は、その受光面上に、第１検出領域１１１と、該第１検出領域１１１をその外縁側から包囲する第２検出領域１１２とを備えて構成されている。図２に示すように、第１検出領域１１１の外縁と、第２検出領域１１２の外縁とは、第１検出領域１１１の中心を共有する同心円である。 In FIG. 2, first, the GE light receiving element 100 includes a first detection region 111 and a second detection region 112 that surrounds the first detection region 111 from the outer edge side on the light receiving surface. ing. As shown in FIG. 2, the outer edge of the first detection region 111 and the outer edge of the second detection region 112 are concentric circles that share the center of the first detection region 111.
　第１検出領域１１１は、半径ｒの円領域である。ここで、半径ｒは、ＮＡが１に相当する光が、ＧＥ用受光素子１００上に形成する円の半径に相当する。第１検出領域１１１は、半導体レーザ２０１から出射された光Ｌのうち、ＮＡが１未満に相当する光、例えばθＢ≦θ≦θＣの入射角でＳＩＬ２１０の底面に入射した光、の反射光を受光する。尚、“θＢ”及び“θＣ”は、夫々“ブリュースター角”及び“臨界角”を示している。 The first detection area 111 is a circular area having a radius r. Here, the radius r corresponds to the radius of a circle formed on the light receiving element 100 for GE by light corresponding to NA of 1. The first detection region 111 reflects light having a NA corresponding to less than 1 among the light L emitted from the semiconductor laser 201, for example, light incident on the bottom surface of the SIL 210 at an incident angle of θ B ≦ θ ≦ θ C. Receives light. “Θ B ” and “θ C ” indicate “Brewster angle” and “critical angle”, respectively.
　第２検出領域１１２は、内径ｒ、外径Ｒの環状領域である。ここで、外径Ｒは、ＳＩＬ２１０の最大開口数に相当する光が、ＧＥ用受光素子１００上に形成する円の半径に相当する。尚、本実施形態では、ＳＩＬ２１０の最大開口数は、例えば２．２６である。第２検出領域１１２は、半導体レーザ２０１から出射された光Ｌのうち、ＳＩＬ２１０の底面で全反射された光（即ち、ＮＡが１以上に相当する光）を受光する。 The second detection region 112 is an annular region having an inner diameter r and an outer diameter R. Here, the outer diameter R corresponds to the radius of a circle formed on the light receiving element 100 for GE by light corresponding to the maximum numerical aperture of the SIL 210. In the present embodiment, the maximum numerical aperture of the SIL 210 is 2.26, for example. The second detection region 112 receives light L totally emitted from the bottom surface of the SIL 210 (that is, light having NA equal to or greater than 1) out of the light L emitted from the semiconductor laser 201.
　次に、ギャップエラーサーボ回路３０は、例えば図２に示すような構成となっている。本実施形態では特に、第１検出領域１１１から出力される該第１検出領域１１１で受光された光の受光量を示す信号に基づいて、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度が制御されている。また、第２検出領域１１２から出力される該第２検出領域１１２で受光された光の受光量を示す信号に基づいて、ギャップエラー信号が生成される。 Next, the gap error servo circuit 30 has a configuration as shown in FIG. 2, for example. Particularly in this embodiment, the speed at which the SIL assembly 209 approaches the optical disc 10 is controlled based on a signal indicating the amount of light received by the first detection region 111 that is output from the first detection region 111. . Further, a gap error signal is generated based on a signal indicating the amount of light received by the second detection region 112 that is output from the second detection region 112.
　ここで、第１検出領域１１１及び第２検出領域１１２の各々における受光量と、ＳＩＬ２１０の底部及び光ディスク１０の表面間のギャップとの関係について、図３を参照して説明する。図３は、受光比とギャップとの関係を示すシミュレーション結果の一例である。 Here, the relationship between the amount of received light in each of the first detection region 111 and the second detection region 112 and the gap between the bottom of the SIL 210 and the surface of the optical disc 10 will be described with reference to FIG. FIG. 3 is an example of a simulation result showing the relationship between the light reception ratio and the gap.
　尚、図３（ａ）は、本実施形態に係るＧＥ用受光素子のシミュレーション結果の一例であり、図３（ｂ）は、本実施形態の比較例に係るＧＥ用受光素子のシミュレーション結果の一例である。また、本実施形態に係る受光比（Ｄｅｔｅｃｔｅｄ　ｌｉｇｈｔ　ｒａｔｉｏ）とは、検出領域の面積に対する受光面積の比を意味する。また、図３（ａ）の破線は、第１検出領域１１１に係る受光比を示し、実線は、第２検出領域１１２に係る受光比を示している。 3A is an example of a simulation result of the light receiving element for GE according to the present embodiment, and FIG. 3B is an example of a simulation result of the light receiving element for GE according to the comparative example of the present embodiment. It is. Further, the light reception ratio (Detected light ratio) according to the present embodiment means the ratio of the light reception area to the area of the detection region. Also, the broken line in FIG. 3A indicates the light reception ratio related to the first detection region 111, and the solid line indicates the light reception ratio related to the second detection region 112.
　先ず、本実施形態に係るＧＥ用受光素子１００に係る受光比について説明する。図３（ａ）に示すように、ＳＩＬ２１０の底部及び光ディスク１０の表面間のギャップ（以下、適宜“ギャップ”と称する）が１０００ｎｍ以上では、第１検出領域１１１では光が検出されない。これは、ＮＡが１未満に相当する光は、ＳＩＬ２１０の底面を透過して光ディスク１０で反射され、上述の如く、偏光ビームスプリッタ２０５によりＲＦ用受光素子２１２に入射するためである。他方、ＮＡが１以上に相当する光は、ＳＩＬ２１０の底面で全反射されるので、第２検出領域１１２では光が検出される。 First, the light reception ratio of the GE light receiving element 100 according to this embodiment will be described. As shown in FIG. 3A, when the gap between the bottom of the SIL 210 and the surface of the optical disc 10 (hereinafter referred to as “gap” as appropriate) is 1000 nm or more, no light is detected in the first detection region 111. This is because light corresponding to NA of less than 1 passes through the bottom surface of the SIL 210 and is reflected by the optical disk 10 and is incident on the RF light receiving element 212 by the polarization beam splitter 205 as described above. On the other hand, the light corresponding to NA of 1 or more is totally reflected on the bottom surface of the SIL 210, so that the light is detected in the second detection region 112.
　ギャップが２００ｎｍから１０００ｎｍまで（以下、適宜“遷移領域”と称する）では、第１検出領域１１１及び第２検出領域１１２の両方において光が検出される。これは、光ディスク１０で反射された光の一部が、偏光ビームスプリッタ２０５によりＲＦ用受光素子２１２側に反射されずに、ＧＥ用受光素子１００の第１検出領域１１１に入射するためである。 When the gap is 200 nm to 1000 nm (hereinafter referred to as “transition region” as appropriate), light is detected in both the first detection region 111 and the second detection region 112. This is because part of the light reflected by the optical disc 10 is incident on the first detection region 111 of the GE light receiving element 100 without being reflected by the polarizing beam splitter 205 toward the RF light receiving element 212 side.
　ギャップが２００ｎｍ以下（即ち、ニアフィールド領域）では、第１検出領域１１１では光が検出されない。また、第２検出領域１１２に係る受光比が、ギャップが小さくなるにつれ低下する。これは、本実施形態に係る光学系のニアフィールド領域にＳＩＬ２１０が侵入したことに起因して、エバネッセント光が発生するためである。 When the gap is 200 nm or less (that is, the near field region), no light is detected in the first detection region 111. In addition, the light reception ratio related to the second detection region 112 decreases as the gap decreases. This is because evanescent light is generated due to the SIL 210 entering the near field region of the optical system according to the present embodiment.
　図３（ａ）に示すように、遷移領域では、第１検出領域１１１に係る受光比が顕著に増加するので、第１検出領域１１１に係る受光比に応じて、ＳＩＬ２１０がニアフィールド領域に接近したことを検出することができる。 As shown in FIG. 3A, in the transition region, the light reception ratio related to the first detection region 111 increases significantly, so that the SIL 210 approaches the near field region according to the light reception ratio related to the first detection region 111. Can be detected.
　次に、本実施形態の比較例に係るＧＥ用受光素子に係る受光比について説明する。尚、比較例に係るＧＥ用受光素子は、受光面が分割されていない受光素子である。図３（ｂ）に示すように、遷移領域において、受光比が緩やかに増加する。また、ギャップが２００ｎｍ以下において、受光比はギャップが小さくなるにつれ低下する。 Next, the light reception ratio according to the light receiving element for GE according to the comparative example of the present embodiment will be described. The light receiving element for GE according to the comparative example is a light receiving element in which the light receiving surface is not divided. As shown in FIG. 3B, the light reception ratio gradually increases in the transition region. Further, when the gap is 200 nm or less, the light receiving ratio decreases as the gap becomes smaller.
　しかしながら、図３（ｂ）に示すように、遷移領域における受光比の増加量は比較的小さいため、実践上、ＳＩＬ２１０がニアフィールド領域に接近したことを検出することは困難である。 However, as shown in FIG. 3B, the amount of increase in the light reception ratio in the transition region is relatively small, so that it is difficult to detect that the SIL 210 has approached the near field region in practice.
　このように、本実施形態に係るＧＥ用受光素子１００は、第１検出領域１１１及び第２検出領域１１２に分割されているため、ニアフィールド領域において、ダイナミックレンジが、未分割受光素子（即ち、本実施形態の比較例に係る受光素子）に比べて大きくなっている。この結果、ギャップエラー信号のＳ／Ｎ比を向上させることができる。加えて、遷移領域において、第１検出領域１１１に係る受光比が比較的大きく変動しているため、ＳＩＬ２１０がニアフィールド領域に接近したことを適切に検出することができる。 Thus, since the GE light receiving element 100 according to the present embodiment is divided into the first detection region 111 and the second detection region 112, the dynamic range in the near field region is an undivided light receiving element (that is, It is larger than the light receiving element according to the comparative example of the present embodiment. As a result, the S / N ratio of the gap error signal can be improved. In addition, in the transition region, the light reception ratio related to the first detection region 111 fluctuates relatively greatly, so that it is possible to appropriately detect that the SIL 210 has approached the near field region.
　次に、以上のように構成された本実施形態に係る光ピックアップ２０において、ギャップエラーサーボ回路３０が実行するレンズアクチュエータ２２０の制御方法について、図４のフローチャートを参照して説明する。 Next, a method for controlling the lens actuator 220 executed by the gap error servo circuit 30 in the optical pickup 20 according to the present embodiment configured as described above will be described with reference to the flowchart of FIG.
　図４において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ１０１）。 4, first, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S101).
　上記ステップＳ１０１と並行して、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第１検出領域１１１で受光された光の受光量を検出する（ステップＳ１０２）。尚、第１検出領域１１１に係る受光量の検出は、連続して又は周期的に実行されてよい。 In parallel with step S101, the gap error servo circuit 30 detects the amount of light received by the first detection region 111 of the light receiving element 100 for GE (step S102). Note that the detection of the amount of light received in the first detection region 111 may be executed continuously or periodically.
　続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以上であるか否かを判定する（ステップＳ１０３）。検出された受光量が閾値以上であると判定された場合（ステップＳ１０３：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下するようにレンズアクチュエータ２２０を制御する（ステップＳ１０４）。他方、検出された受光量が閾値未満であると判定された場合（ステップＳ１０３：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ１０１の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is greater than or equal to a threshold value (step S103). If it is determined that the detected amount of received light is equal to or greater than the threshold (step S103: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S104). On the other hand, when it is determined that the detected amount of received light is less than the threshold value (step S103: No), the gap error servo circuit 30 executes the process of step S101.
　尚、本実施形態に係る「閾値」は、ＳＩＬアッセンブリ２０９の光ディスク１０に近づく速度をより低下させるようにレンズアクチュエータ２２０を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第１検出領域１１１に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 The “threshold value” according to the present embodiment is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and may be a fixed value or some sort of value in advance. It is set as a variable value according to the physical quantity or parameter. Such a threshold is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of light received in the first detection region 111 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
　尚、本実施形態に係るＧＥ用受光素子１００は、図２に示した形態に限られない。ＧＥ用受光素子１００は、例えば図５（ａ）に示すような、円弧状の第２検出領域１１２を有していてもよいし、図５（ｂ）に示すような、ＧＥ用受光素子１００の受光面のうち第１検出領域１１１以外の領域が第２検出領域１１２であってもよい。或いは、ＧＥ用受光素子１００は、例えば図５（ｃ）に示すような、環状の第１検出領域１１１を有していてもよい。ここに、図５は、本実施形態に係るＧＥ用受光素子の変形例を示す模式図である。 The GE light receiving element 100 according to the present embodiment is not limited to the form shown in FIG. The GE light receiving element 100 may have, for example, an arc-shaped second detection region 112 as shown in FIG. 5A, or the GE light receiving element 100 as shown in FIG. 5B. The second detection region 112 may be a region other than the first detection region 111 of the light receiving surface. Alternatively, the light receiving element 100 for GE may have an annular first detection region 111 as shown in FIG. 5C, for example. FIG. 5 is a schematic diagram showing a modification of the light receiving element for GE according to the present embodiment.
　＜変形例＞
　次に、本実施形態の変形例について、図６乃至図８を参照して説明する。図６は、図２と同趣旨の、本変形例に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。 <Modification>
Next, a modification of this embodiment will be described with reference to FIGS. FIG. 6 is a block diagram showing the configuration of a light receiving element for GE and a gap error servo circuit according to this modification having the same concept as in FIG.
　本変形例では特に、第２検出領域１１２から出力される該第２検出領域１１２で受光された光の受光量を示す信号から、第１検出領域１１１から出力される該第１検出領域１１１で受光された光の受光量を示す信号を引いた差分信号に基づいて、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度の制御、及びギャップエラー信号の生成が行われている。 In the present modification, in particular, from the signal indicating the amount of light received by the second detection region 112 output from the second detection region 112, the first detection region 111 output from the first detection region 111. Based on a difference signal obtained by subtracting a signal indicating the amount of received light, control of the speed at which the SIL assembly 209 approaches the optical disk 10 and generation of a gap error signal are performed.
　ここで、差分信号により示される受光比とギャップとの関係について、図７を参照して説明する。図７は、図３と同趣旨の、受光比とギャップとの関係を示すシミュレーション結果の他の例である。 Here, the relationship between the light reception ratio indicated by the difference signal and the gap will be described with reference to FIG. FIG. 7 is another example of the simulation result showing the relationship between the light reception ratio and the gap, which has the same concept as in FIG.
　本変形例では特に、図７に示すように、遷移領域において、ＳＩＬアッセンブリ２０９が光ディスク１０に近づくにつれて、受光比が低下し、その後上昇している。このため、受光比が低下した後に上昇するという現象を検出することによって、ＳＩＬアッセンブリ２０９がニアフィールド領域に接近したことを検出することができる。 Particularly in the present modification, as shown in FIG. 7, in the transition region, as the SIL assembly 209 approaches the optical disc 10, the light reception ratio decreases and then increases. For this reason, it is possible to detect that the SIL assembly 209 has approached the near field region by detecting a phenomenon that the light receiving ratio increases after decreasing.
　次に、以上のように構成された本変形例に係る光ピックアップ２０において、ギャップエラーサーボ回路３０が実行するレンズアクチュエータ２２０の制御方法について、図８のフローチャートを参照して説明する。 Next, a control method of the lens actuator 220 executed by the gap error servo circuit 30 in the optical pickup 20 according to this modification configured as described above will be described with reference to the flowchart of FIG.
　図８において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ２０１）。 8, first, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S201).
　上記ステップＳ２０１と並行して、ギャップエラーサーボ回路３０は、第２検出領域１１２で受光された光の受光量を検出する（ステップＳ２０２）と共に、第１検出領域１１１で受光された光の受光量を検出する（ステップＳ２０３）。続いて、ギャップエラーサーボ回路３０は、検出された第２検出領域１１２に係る受光量から、検出された第１検出領域に係る受光量を引いて、差分光量を計算する（ステップＳ２０４）。尚、ステップＳ２０２及びＳ２０３の処理は、連続して又は周期的に実行されてよい。 In parallel with step S201, the gap error servo circuit 30 detects the amount of light received by the second detection region 112 (step S202) and receives the amount of light received by the first detection region 111. Is detected (step S203). Subsequently, the gap error servo circuit 30 calculates the difference light amount by subtracting the detected light amount related to the first detection region from the detected light amount related to the second detection region 112 (step S204). Note that the processing in steps S202 and S203 may be executed continuously or periodically.
　次に、ギャップエラーサーボ回路３０は、計算された差分光量が閾値以下であるか否かを判定する（ステップＳ２０５）。計算された差分光量が閾値以下であると判定された場合（ステップＳ２０５：Ｙｅｓ）、ギャップエラーサーボ回路３０は、引き続き、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ２０６）。他方、計算された差分光量が閾値より大きいと判定された場合（ステップＳ２０５：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ２０１の処理を実行する。 Next, the gap error servo circuit 30 determines whether or not the calculated difference light amount is equal to or less than a threshold value (step S205). When it is determined that the calculated difference light amount is equal to or smaller than the threshold (step S205: Yes), the gap error servo circuit 30 continues to control the lens actuator 220 so that the SIL assembly 209 approaches the optical disc 10 (step S206). ). On the other hand, when it is determined that the calculated difference light amount is larger than the threshold value (step S205: No), the gap error servo circuit 30 executes the process of step S201.
　ギャップエラーサーボ回路３０は、上記ステップＳ２０６と並行して、第２検出領域１１２で受光された光の受光量を検出する（ステップＳ２０７）と共に、第１検出領域１１１で受光された光の受光量を検出する（ステップＳ２０８）。続いて、ギャップエラーサーボ回路３０は、検出された第２検出領域１１２に係る受光量から、検出された第１検出領域に係る受光量を引いて、差分光量を計算する（ステップＳ２０９）。尚、ステップＳ２０７及びＳ２０８の処理は、連続して又は周期的に実行されてよい。 In parallel with step S206, the gap error servo circuit 30 detects the amount of light received by the second detection region 112 (step S207) and also receives the amount of light received by the first detection region 111. Is detected (step S208). Subsequently, the gap error servo circuit 30 calculates the difference light amount by subtracting the detected light amount related to the first detection region from the detected light amount related to the second detection region 112 (step S209). Note that the processing in steps S207 and S208 may be executed continuously or periodically.
　次に、ギャップエラーサーボ回路３０は、計算された差分光量が閾値以上であるか否かを判定する（ステップＳ２１０）。計算された差分光量が閾値以上であると判定された場合（ステップＳ２１０：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下するようにレンズアクチュエータ２２０を制御する（ステップＳ１１１）。他方、計算された差分光量が閾値未満であると判定された場合（ステップＳ２１０：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ２０６の処理を実行する。 Next, the gap error servo circuit 30 determines whether or not the calculated difference light amount is greater than or equal to a threshold value (step S210). If it is determined that the calculated difference light amount is equal to or greater than the threshold (step S210: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S111). On the other hand, when it is determined that the calculated difference light quantity is less than the threshold value (step S210: No), the gap error servo circuit 30 executes the process of step S206.
　このように、本変形例に係る制御方法では、差分光量が、閾値以下になった後に閾値以上となったことを検出することによって、図７に示した、受光比が低下した後に上昇するという現象を検出している。 As described above, in the control method according to the present modification, by detecting that the difference light amount becomes equal to or greater than the threshold value after becoming less than or equal to the threshold value, the light amount ratio increases as shown in FIG. The phenomenon is detected.
　尚、本変形例に係る「閾値」は、受光比が低下した後に上昇するという現象を確実に検出できる値として設定されている。尚、上記ステップＳ２０５における閾値と、ステップＳ２１０における閾値とは、同じであってもよいし、互いに異なっていてもよい。 It should be noted that the “threshold value” according to this modification is set as a value that can reliably detect the phenomenon that the threshold value increases after the light reception ratio decreases. The threshold value in step S205 and the threshold value in step S210 may be the same or different from each other.
　＜第２実施形態＞
　本発明の光検出器に係る第２実施形態を、図９乃至図１４を参照して説明する。第２実施形態では、ＧＥ用受光素子及びギャップエラーサーボ回路の構成が一部異なる以外は、第１実施形態の構成と同様である。よって、第２実施形態について、第１実施形態と重複する説明を省略すると共に、図面上における共通箇所には同一符号を付して示し、基本的に異なる点についてのみ、図９乃至図１４を参照して説明する。 <Second Embodiment>
A second embodiment of the photodetector of the present invention will be described with reference to FIGS. The second embodiment is the same as the first embodiment except that the configurations of the light receiving element for GE and the gap error servo circuit are partially different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and common portions in the drawings are denoted by the same reference numerals, and FIGS. 9 to 14 are shown only for different points. The description will be given with reference.
　先ず、本実施形態に係るＧＥ用受光素子１００及びギャップエラーサーボ回路３０について、図９及び図１０を参照して説明する。図９は、本実施形態に係るＧＥ用受光素子を示す模式図である。また、図１０は、図２と同趣旨の、本実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。 First, the GE light receiving element 100 and the gap error servo circuit 30 according to this embodiment will be described with reference to FIGS. FIG. 9 is a schematic diagram showing a light receiving element for GE according to the present embodiment. FIG. 10 is a block diagram showing the configuration of the light receiving element for GE and the gap error servo circuit according to the present embodiment having the same concept as in FIG.
　図９において、ＧＥ用受光素子１００は、その受光面に、第１検出領域１２１と、該第１検出領域１２１をその外縁側から包囲する第２検出領域１２２と、該第２検出領域１２２をその外縁側から包囲する第３検出領域１２３と、該第３検出領域１２３をその外縁側から包囲する第４検出領域１２４とを備えて構成されている。図９に示すように、第１検出領域１２１の外縁、第２検出領域１２２の外縁、第３検出領域１２３の外縁及び第４検出領域１２４の外縁は、第１検出領域１２１の中心を共有する同心円である。 In FIG. 9, the light receiving element 100 for GE includes, on its light receiving surface, a first detection area 121, a second detection area 122 surrounding the first detection area 121 from its outer edge side, and the second detection area 122. A third detection region 123 that surrounds from the outer edge side and a fourth detection region 124 that surrounds the third detection region 123 from the outer edge side are configured. As shown in FIG. 9, the outer edge of the first detection region 121, the outer edge of the second detection region 122, the outer edge of the third detection region 123, and the outer edge of the fourth detection region 124 share the center of the first detection region 121. It is a concentric circle.
　第１検出領域１２１は、半径ｒの円領域である。第２検出領域１２２は、内径ｒ、外径（１＋ΔＮ）ｒの環状領域である。ここで、“ΔＮ”は、例えば０．２等の値である。第３検出領域１２３は、内径（１＋ΔＮ）ｒ、外径Ｒ－ΔＮ・ｒの環状領域である。第４検出領域１２４は、内径Ｒ－ΔＮ・ｒ、外径Ｒの環状領域である。 The first detection area 121 is a circular area having a radius r. The second detection region 122 is an annular region having an inner diameter r and an outer diameter (1 + ΔN) r. Here, “ΔN” is a value such as 0.2. The third detection region 123 is an annular region having an inner diameter (1 + ΔN) r and an outer diameter R−ΔN · r. The fourth detection region 124 is an annular region having an inner diameter R−ΔN · r and an outer diameter R.
　ここで、ＳＩＬ２１０がニアフィールド領域に侵入すると、エバネッセント光が発生することに起因して、ＮＡが１以上に相当する光の光量が減少する。特に、ギャップが小さくなるにつれ、ＮＡの低い光からＧＥ用受光素子１００に入射しなくなる（即ち、スポットの中央部に生じる暗部が徐々に広がる）。 Here, when the SIL 210 enters the near field region, the amount of light corresponding to NA of 1 or more decreases due to the generation of evanescent light. In particular, as the gap becomes smaller, light having a low NA does not enter the light receiving element 100 for GE (that is, a dark part generated at the center of the spot gradually spreads).
　このため、図９に示したように、上述の第１実施形態に係る第２検出領域１１２に相当する領域を、複数の検出領域に分割することによって、例えばＳＩＬ２１０がニアフィールド領域に侵入したこと、ＳＩＬ２１０が光ディスク１０に接近し過ぎであること等を検出することができる。 For this reason, as shown in FIG. 9, for example, the SIL 210 has entered the near field region by dividing the region corresponding to the second detection region 112 according to the first embodiment into a plurality of detection regions. It is possible to detect that the SIL 210 is too close to the optical disk 10 or the like.
　図１０において、ギャップエラーサーボ回路３０は、第１検出領域１２１から出力される該第１検出領域１２１で受光される光の受光量を示す信号、第２検出領域１２２から出力される該第２検出領域１２２で受光される光の受光量を示す信号、及び第４検出領域１２４から出力される該第４検出領域１２４で受光される光の受光量を示す信号に基づいて、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度の制御、サーボループをクローズ状態とするタイミングの制御、及び衝突回避処理を行う。 In FIG. 10, the gap error servo circuit 30 outputs a signal indicating the amount of light received by the first detection area 121 output from the first detection area 121 and the second output from the second detection area 122. Based on a signal indicating the amount of light received by the detection region 122 and a signal indicating the amount of light received by the fourth detection region 124 output from the fourth detection region 124, the SIL assembly 209 Control of the speed approaching the optical disk 10, control of timing for closing the servo loop, and collision avoidance processing are performed.
　また、ギャップエラーサーボ回路３０は、第２検出領域１２２から出力される該第２検出領域１２２で受光される光の受光量を示す信号、第３検出領域１２３から出力される該第３検出領域１２３で受光される光の受光量を示す信号、及び第４検出領域１２４から出力される該第４検出領域１２４で受光される光の受光量を示す信号の和を示す信号に基づいて、ギャップエラー信号を生成する。 The gap error servo circuit 30 also outputs a signal indicating the amount of light received by the second detection region 122 output from the second detection region 122 and the third detection region output from the third detection region 123. 123, based on a signal indicating the amount of light received by 123 and a signal indicating the sum of signals indicating the amount of light received by the fourth detection region 124 output from the fourth detection region 124. Generate an error signal.
　次に、第１検出領域１２１、第２検出領域１２２及び第４検出領域１２４の各々における受光量と、ギャップとの関係について、図１１を参照して説明する。図１１は、図３と同趣旨の、受光比とギャップとの関係を示すシミュレーション結果の他の例である。尚、図１１（ａ）は、第１検出領域１２１に係る受光比を示しており、図１１（ｂ）は、第２検出領域１２２に係る受光比を示しており、図１１（ｃ）は、第４検出領域１２４に係る受光比を示している。 Next, the relationship between the amount of received light and the gap in each of the first detection region 121, the second detection region 122, and the fourth detection region 124 will be described with reference to FIG. FIG. 11 is another example of the simulation result showing the relationship between the light reception ratio and the gap, which has the same concept as in FIG. FIG. 11A shows the light reception ratio related to the first detection region 121, FIG. 11B shows the light reception ratio related to the second detection region 122, and FIG. , The light reception ratio relating to the fourth detection region 124 is shown.
　遷移領域において、光ディスク１０で反射された光の一部が、ＧＥ用受光素子１００の第１検出領域１２１に入射する。このため、図１１（ａ）に示すように、第１検出領域１２１に係る受光比が増加する。 In the transition region, a part of the light reflected by the optical disc 10 enters the first detection region 121 of the light receiving element 100 for GE. For this reason, as shown to Fig.11 (a), the light reception ratio which concerns on the 1st detection area 121 increases.
　ギャップが２００ｎｍ以下（即ち、ニアフィールド領域）になった直後では、エバネッセント光が発生することに起因して、ＮＡが１近傍に相当する光の光量が減少する。このため、図１１（ｂ）に示すように、第２検出領域１２２に係る受光比が減少する。 Immediately after the gap is 200 nm or less (that is, the near field region), the amount of light corresponding to NA near 1 decreases due to the generation of evanescent light. For this reason, as shown in FIG.11 (b), the light reception ratio concerning the 2nd detection area | region 122 reduces.
　ＳＩＬ２１０が光ディスク１０に接触するおそれがある程近づいた場合（即ち、過接近状態）では、ＧＥ用受光素子１００上のスポットの最外周の光量が減少する。このため、図１１（ｃ）に示すように、第４検出領域１２４に係る受光比が減少する。 When the SIL 210 is so close that it may come into contact with the optical disk 10 (that is, in an excessively close state), the amount of light at the outermost periphery of the spot on the GE light receiving element 100 decreases. For this reason, as shown in FIG.11 (c), the light reception ratio concerning the 4th detection area | region 124 reduces.
　このように、本実施形態に係るＧＥ用受光素子１００は、第１検出領域１２１、第２検出領域１２２、第３検出領域１２３及び第４検出領域１２４に分割されている。このため、第１検出領域１２１に係る受光量に基づいてＳＩＬ２１０がニアフィールド領域に接近したことを検出することができる。また、第２検出領域１２２に係る受光量に基づいてＳＩＬ２１０がニアフィールド領域に侵入したことを検出することができる。また、第４検出領域１２４に係る受光量に基づいてＳＩＬ２１０が過接近状態であることを検出することができる。 As described above, the GE light receiving element 100 according to the present embodiment is divided into the first detection region 121, the second detection region 122, the third detection region 123, and the fourth detection region 124. Therefore, it is possible to detect that the SIL 210 has approached the near field area based on the amount of light received in the first detection area 121. Further, it is possible to detect that the SIL 210 has entered the near field area based on the amount of light received in the second detection area 122. Further, it is possible to detect that the SIL 210 is in an excessively close state based on the amount of light received in the fourth detection region 124.
　本実施形態では特に、図１１に示したように、受光比の上昇の傾き又は下降の傾きが比較的大きい。このため、ギャップを高感度に検出することができる。具体的には例えば、遷移領域においては、第１検出領域１２１に係る受光比の１％の変化により、１６．０５ｎｍのギャップの変化を検出することができる。また、ギャップが２００ｎｍ近傍では、第２検出領域１２２に係る受光比の１％の変化により、０．３２ｎｍのギャップの変化を検出することができる。また、ギャップが０ｎｍ近傍（以下、適宜“過接近領域”と称する）では、第４検出領域１２４に係る受光比の１％の変化により、０．３２ｎｍのギャップの変化を検出することができる。これは、ＧＥ用受光素子１００に、未分割受光素子を適用した場合の感度に対して、最大約２５倍の感度である。 In the present embodiment, in particular, as shown in FIG. 11, the rising or falling slope of the light reception ratio is relatively large. For this reason, the gap can be detected with high sensitivity. Specifically, for example, in the transition region, a change in gap of 16.05 nm can be detected by a 1% change in the light reception ratio related to the first detection region 121. In addition, when the gap is in the vicinity of 200 nm, a change in gap of 0.32 nm can be detected by a change of 1% in the light reception ratio of the second detection region 122. In addition, when the gap is in the vicinity of 0 nm (hereinafter, referred to as “over-close region” as appropriate), a change in gap of 0.32 nm can be detected by a 1% change in the light reception ratio of the fourth detection region 124. This is a maximum of about 25 times the sensitivity when the undivided light receiving element is applied to the light receiving element 100 for GE.
　次に、以上のように構成された本実施形態に係る光ピックアップ２０において、ギャップエラーサーボ回路３０が実行するレンズアクチュエータ２２０の制御方法について、図１２及び図１３のフローチャートを参照して説明する。 Next, a control method of the lens actuator 220 executed by the gap error servo circuit 30 in the optical pickup 20 according to the present embodiment configured as described above will be described with reference to the flowcharts of FIGS.
　図１２において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ３０１）。 12, first, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S301).
　上記ステップＳ３０１と並行して、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第１検出領域１２１で受光された光の受光量を検出する（ステップＳ３０２）。尚、第１検出領域１２１に係る受光量の検出は、連続して又は周期的に実行されてよい。 In parallel with step S301, the gap error servo circuit 30 detects the amount of light received by the first detection region 121 of the light receiving element 100 for GE (step S302). Note that the detection of the amount of light received in the first detection region 121 may be executed continuously or periodically.
　続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以上であるか否かを判定する（ステップＳ３０３）。検出された受光量が閾値以上であると判定された場合（ステップＳ３０３：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下させるようにレンズアクチュエータ２２０を制御する（ステップＳ３０４）。他方、検出された受光量が閾値未満であると判定された場合（ステップＳ３０３：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ３０１の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or greater than a threshold value (step S303). If it is determined that the detected amount of received light is equal to or greater than the threshold (step S303: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S304). On the other hand, when it is determined that the detected amount of received light is less than the threshold (step S303: No), the gap error servo circuit 30 executes the process of step S301.
　ステップＳ３０４の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ３０５）。 After step S304, the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S305).
　上記ステップＳ３０５の処理と並行して、ギャップエラーサーボ回路３０は、第２検出領域１２２で受光された光の受光量を検出する（ステップＳ３０６）。尚、第２検出領域１２２に係る受光量の検出は、連続して又は周期的に実行されてよい。 In parallel with the processing in step S305, the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S306). The detection of the amount of received light related to the second detection region 122 may be executed continuously or periodically.
　続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以下であるか否かを判定する（ステップＳ３０７）。検出された受光量が閾値以下であると判定された場合（ステップＳ３０７：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボループをクローズ状態とする（ステップＳ３０８）。他方、検出された受光量が閾値より大きいと判定された場合（ステップＳ３０７：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ３０５の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S307). When it is determined that the detected amount of received light is equal to or less than the threshold (step S307: Yes), the gap error servo circuit 30 closes the gap servo loop (step S308). On the other hand, when it is determined that the detected amount of received light is larger than the threshold (step S307: No), the gap error servo circuit 30 executes the process of step S305.
　尚、本実施形態に係るステップＳ３０３の処理における「閾値」は、ＳＩＬアッセンブリ２０９の光ディスク１０に近づく速度をより低下させるようにレンズアクチュエータ２２０を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第１検出領域１２１に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 The “threshold value” in the process of step S303 according to the present embodiment is a value that determines whether to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is fixed in advance. It is set as a value or a variable value according to some physical quantity or parameter. Such a threshold value is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of light received in the first detection region 121 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
　また、本実施形態に係るステップＳ３０７の処理における「閾値」は、ギャップサーボループをクローズ状態とするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域１２２に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 In addition, the “threshold value” in the process of step S307 according to the present embodiment is a value that determines whether or not the gap servo loop is to be closed, and is a fixed value in advance or a variable value according to some physical quantity or parameter Set as Such a threshold value is set based on the obtained relationship by obtaining, for example, a relationship between the signal level indicating the amount of received light related to the second detection region 122 and the gap experimentally, empirically, or by simulation. That's fine.
　次に、ギャップエラーサーボ回路３０が実行する衝突回避処理について説明する。尚、衝突回避処理は、主に、ギャップサーボループがクローズ状態である場合に実行される。 Next, the collision avoidance process executed by the gap error servo circuit 30 will be described. The collision avoidance process is executed mainly when the gap servo loop is in a closed state.
　図１３において、先ず、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第４検出領域１２４で受光された光の受光量を検出する（ステップＳ４０１）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以下であるか否かを判定する（ステップＳ４０２）。 In FIG. 13, first, the gap error servo circuit 30 detects the amount of light received by the fourth detection region 124 of the GE light receiving element 100 (step S401). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S402).
　検出された受光量が閾値以下であると判定された場合（ステップＳ４０２：Ｙｅｓ）、ギャップエラーサーボ回路３０は、衝突回避処理を実行する（ステップＳ４０３）。ここで、衝突回避処理とは、例えば、ＳＩＬアッセンブリ２０９を光ディスク１０から遠ざける、ギャップサーボを中断する等の、ＳＩＬアッセンブリ２０９と光ディスク１０との衝突を回避するための処理を意味する。 When it is determined that the detected amount of received light is equal to or less than the threshold (step S402: Yes), the gap error servo circuit 30 executes a collision avoidance process (step S403). Here, the collision avoidance process means a process for avoiding a collision between the SIL assembly 209 and the optical disk 10 such as moving the SIL assembly 209 away from the optical disk 10 or interrupting the gap servo.
　他方、ステップＳ４０２において、検出された受光量が閾値より大きいと判定された場合（ステップＳ４０２：Ｎｏ）、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第２検出領域１２２で受光された光の受光量を検出する（ステップＳ４０４）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以下であるか否かを判定する（ステップＳ４０５）。 On the other hand, if it is determined in step S402 that the detected amount of received light is larger than the threshold (step S402: No), the gap error servo circuit 30 receives the light received by the second detection region 122 of the GE light receiving element 100. Is detected (step S404). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S405).
　検出された受光量が閾値以上であると判定された場合（ステップＳ４０５：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボをオフ状態にする（ステップＳ４０６）。他方、検出された受光量が閾値より小さいと判定された場合（ステップＳ４０５：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ４０１の処理を実行する。 If it is determined that the detected amount of received light is greater than or equal to the threshold (step S405: Yes), the gap error servo circuit 30 turns off the gap servo (step S406). On the other hand, when it is determined that the detected amount of received light is smaller than the threshold value (step S405: No), the gap error servo circuit 30 executes the process of step S401.
　尚、本実施形態に係るステップＳ４０２の処理における「閾値」は、衝突回避処理を実行するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第４検出領域１２４に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 The “threshold value” in the process of step S402 according to the present embodiment is a value that determines whether or not to perform the collision avoidance process, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter. Is done. Such a threshold is set based on the obtained relationship by obtaining a relationship between the gap between the signal level indicating the amount of received light related to the fourth detection region 124 and the gap, for example, experimentally, empirically, or by simulation. That's fine.
　また、本実施形態に係るステップＳ４０５の処理における「閾値」は、ギャップサーボをオフ状態にするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域１２２に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 Further, the “threshold value” in the process of step S405 according to the present embodiment is a value that determines whether or not the gap servo is turned off, and is a fixed value in advance or a variable value according to some physical quantity or parameter. Is set. Such a threshold value is set based on the obtained relationship by obtaining, for example, a relationship between the signal level indicating the amount of received light related to the second detection region 122 and the gap experimentally, empirically, or by simulation. That's fine.
　＜変形例＞
　次に、本実施形態の変形例について、図１４のフローチャートを参照して説明する。 <Modification>
Next, a modification of the present embodiment will be described with reference to the flowchart of FIG.
　図１４において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ５０１）。 14, first, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S501).
　上記ステップＳ５０１と並行して、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第１検出領域１２１で受光された光の受光量を検出する（ステップＳ５０２）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以上であるか否かを判定する（ステップＳ５０３）。 In parallel with step S501, the gap error servo circuit 30 detects the amount of light received by the first detection region 121 of the light receiving element 100 for GE (step S502). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is greater than or equal to a threshold value (step S503).
　検出された受光量が閾値以上であると判定された場合（ステップＳ５０３：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下するようにレンズアクチュエータ２２０を制御する（ステップＳ５０４）。他方、検出された受光量が閾値未満であると判定された場合（ステップＳ５０３：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ５０１の処理を実行する。 When it is determined that the detected amount of received light is equal to or greater than the threshold (step S503: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10 ( Step S504). On the other hand, when it is determined that the detected amount of received light is less than the threshold value (step S503: No), the gap error servo circuit 30 executes the process of step S501.
　ステップＳ５０４の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ５０５）。 After step S504, the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S505).
　上記ステップＳ５０５の処理と並行して、ギャップエラーサーボ回路３０は、第２検出領域１２２で受光された光の受光量を検出する（ステップＳ５０６）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が第１閾値以下であるか否かを判定する（ステップＳ５０７）。 In parallel with the processing in step S505, the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S506). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than the first threshold (step S507).
　検出された受光量が第１閾値以下であると判定された場合（ステップＳ５０７：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度をより低下するようにレンズアクチュエータ２２０を制御する（ステップＳ５０８）。他方、検出された受光量が第１閾値より大きいと判定された場合（ステップＳ５０７：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ５０５の処理を実行する。 When it is determined that the detected amount of received light is equal to or less than the first threshold (step S507: Yes), the gap error servo circuit 30 moves the lens actuator 220 so that the speed at which the SIL assembly 209 approaches the optical disc 10 is further reduced. Control is performed (step S508). On the other hand, when it is determined that the detected amount of received light is larger than the first threshold (step S507: No), the gap error servo circuit 30 executes the process of step S505.
　ステップＳ５０８の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ５０９）。 After step S508, the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S509).
　上記ステップＳ５０９の処理と並行して、ギャップエラーサーボ回路３０は、第２検出領域１２２で受光された光の受光量を検出する（ステップＳ５１０）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が第２閾値以下であるか否かを判定する（ステップＳ５１１）。 In parallel with the processing in step S509, the gap error servo circuit 30 detects the amount of light received by the second detection region 122 (step S510). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than the second threshold (step S511).
　検出された受光量が第２閾値以下であると判定された場合（ステップＳ５１１：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボループをクローズ状態とする（ステップＳ５１１）。他方、検出された受光量が第２閾値より大きいと判定された場合（ステップＳ５１１：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ５０９の処理を実行する。 When it is determined that the detected amount of received light is equal to or less than the second threshold (step S511: Yes), the gap error servo circuit 30 closes the gap servo loop (step S511). On the other hand, when it is determined that the detected amount of received light is larger than the second threshold (step S511: No), the gap error servo circuit 30 executes the process of step S509.
　このようにすれば、上述した第２実施形態に比べて、ギャップがより小さい状態でギャップサーボループをクローズ状態とすることができる。 In this way, the gap servo loop can be closed with a smaller gap than in the second embodiment described above.
　尚、本変形例に係るステップＳ５０３の処理における「閾値」は、上述した第２実施形態に係るステップＳ３０３の処理における「閾値」と同様に設定すればよい。 It should be noted that the “threshold value” in the process of step S503 according to this modification may be set in the same manner as the “threshold value” in the process of step S303 according to the second embodiment described above.
　本変形例に係るステップＳ５０７における「第１閾値」は、ＳＩＬアッセンブリ２０９の光ディスク１０に近づく速度をより低下させるようにレンズアクチュエータ２２０を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第１閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域１２２に係る受光量とギャップとの関係を求め、該求められた関係に基づいて、レンズアクチュエータ２２０に対し停止要求があった際に慣性によりＳＩＬアッセンブリ２０９が移動する距離と、ギャップとが等しくなる受光量として、又は該受光量よりも所定量だけ大きい受光量として設定すればよい。 The “first threshold value” in step S507 according to this modification is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is set as a fixed value in advance. Or a variable value according to some physical quantity or parameter. Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the amount of received light and the gap related to the second detection region 122 and, based on the determined relationship, the lens actuator 220. On the other hand, when the stop request is made, the distance of movement of the SIL assembly 209 due to inertia and the received light amount equal to the gap may be set, or the received light amount may be set larger than the received light amount by a predetermined amount.
　本変形例に係る「第２閾値」は、ギャップサーボループをクローズ状態とするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第２閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２検出領域１２２に係る受光量とギャップとの関係を求め、該求められた関係に基づいて、ギャップサーボループをクローズ状態とすべき距離に対応する受光量として設定すればよい。 The “second threshold value” according to this modification is a value that determines whether or not the gap servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the amount of received light and the gap related to the second detection region 122 and, based on the determined relationship, the gap servo loop. What is necessary is just to set as a light reception amount corresponding to the distance which should be set as a closed state.
　＜第３実施形態＞
　本発明の光検出器に係る第３実施形態を、図１５乃至図１８を参照して説明する。第３実施形態では、ＧＥ用受光素子の構成が一部異なる以外は、第２実施形態の構成と同様である。よって、第３実施形態について、第２実施形態と重複する説明を省略すると共に、図面上における共通箇所には同一符号を付して示し、基本的に異なる点についてのみ、図１５乃至図１８を参照して説明する。 <Third Embodiment>
A third embodiment of the photodetector of the present invention will be described with reference to FIGS. The third embodiment is the same as the second embodiment except that the configuration of the light receiving element for GE is partially different. Accordingly, the description of the third embodiment that is the same as that of the second embodiment is omitted, and common portions in the drawings are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. The description will be given with reference.
　図１５は、図９と同趣旨の、本実施形態に係るＧＥ用受光素子を示す模式図である。 FIG. 15 is a schematic diagram showing a light receiving element for GE according to the present embodiment having the same purpose as in FIG.
　図１５において、ＧＥ用受光素子１００は、その受光面に、第１検出領域１３１と、該第１検出領域１３１をその外縁側から包囲する第２検出領域１３２と、該第２検出領域１３２をその外縁側から包囲する第３検出領域１３３と、該第３検出領域１３３をその外縁側から包囲する第４検出領域１３４とを備えて構成されている。図１５に示すように、第１検出領域１３１の外縁、第２検出領域１３２の外縁、第３検出領域１３３の外縁及び第４検出領域１３４の外縁は、第１検出領域１３１の中心を共有する同心円である。 In FIG. 15, the light receiving element 100 for GE includes a first detection region 131, a second detection region 132 surrounding the first detection region 131 from the outer edge side, and the second detection region 132 on the light receiving surface. A third detection region 133 surrounding the outer edge side and a fourth detection region 134 surrounding the third detection region 133 from the outer edge side are configured. As shown in FIG. 15, the outer edge of the first detection region 131, the outer edge of the second detection region 132, the outer edge of the third detection region 133, and the outer edge of the fourth detection region 134 share the center of the first detection region 131. It is a concentric circle.
　本実施形態に係るＧＥ用受光素子１００は、光軸ずれに適切に対応できるように、各検出領域が次のように設定されている。第１検出領域１３１は、半径ｒ－Ｓの円領域である。第２検出領域１３２は、内径ｒ－Ｓ、外径（１＋ΔＮ）ｒ＋Ｓの環状領域である。第３検出領域１３３は、内径（１＋ΔＮ）ｒ＋Ｓ、外径Ｒ－ΔＮ・ｒ－Ｓの環状領域である。第４検出領域１３４は、内径Ｒ－ΔＮ・ｒ－Ｓ、外径Ｒ＋Ｓの環状領域である。 In the GE light receiving element 100 according to the present embodiment, each detection region is set as follows so as to appropriately cope with the optical axis shift. The first detection area 131 is a circular area with a radius r−S. The second detection region 132 is an annular region having an inner diameter r−S and an outer diameter (1 + ΔN) r + S. The third detection region 133 is an annular region having an inner diameter (1 + ΔN) r + S and an outer diameter R−ΔN · r−S. The fourth detection region 134 is an annular region having an inner diameter R−ΔN · r−S and an outer diameter R + S.
　ここで、“Ｓ”は、ＧＥ用受光素子１００上における光軸ずれの想定される上限値を意味する。“Ｓ”は、例えば０．２ｒ（尚、“ｒ”は、上述の如く、ＮＡが１に相当する光が、ＧＥ用受光素子１００上に形成する円の半径に相当する）であり、当該ＧＥ用受光素子１００を備える光ピックアップの光学系等に応じて設定すればよい。 Here, “S” means an assumed upper limit value of the optical axis shift on the light receiving element 100 for GE. “S” is, for example, 0.2r (where “r” is equivalent to the radius of the circle formed on the light receiving element 100 for GE when NA is equal to 1 as described above) What is necessary is just to set according to the optical system etc. of an optical pick-up provided with the light receiving element 100 for GE.
　次に、本実施形態に係るＧＥ用受光素子１００と、上述した第２実施形態に係るＧＥ用受光素子との各々における光軸ずれの影響を、図１６乃至図１８を参照して説明する。図１６は、遷移領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。図１７は、ギャップが２００ｎｍ近傍である場合の受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。図１８は、過接近領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の一例である。 Next, the influence of the optical axis shift in each of the GE light receiving element 100 according to the present embodiment and the GE light receiving element according to the second embodiment will be described with reference to FIGS. 16 to 18. FIG. 16 is an example of a simulation result showing the change in the light reception ratio in the transition region for each optical axis shift amount. FIG. 17 is an example of a simulation result showing the change in the light reception ratio when the gap is in the vicinity of 200 nm for each optical axis deviation amount. FIG. 18 is an example of a simulation result showing the change in the light reception ratio in the excessively close area for each optical axis deviation amount.
　尚、図１６（ａ）、図１７（ａ）及び図１８（ａ）は、本実施形態に係るＧＥ用受光素子１００のシミュレーション結果である。また、図１６（ｂ）、図１７（ｂ）及び図１８（ｂ）は、第２実施形態に係るＧＥ用受光素子のシミュレーション結果である。 16A, 17A, and 18A are simulation results of the light receiving element 100 for GE according to this embodiment. FIGS. 16B, 17B, and 18B show simulation results of the light receiving element for GE according to the second embodiment.
　また、図１６乃至図１８における「光軸ずれ量」は、光軸がＧＥ用受光素子１００の中心からどの程度ずれているかを示している。例えば「光軸ずれ量０」とは、光軸ずれが生じていないことを示している。また、「光軸ずれ量０．０５ｒ」とは、光軸がＧＥ用受光素子１００の中心から０．０５ｒだけずれていることを示している。 Also, the “optical axis deviation amount” in FIGS. 16 to 18 indicates how much the optical axis is deviated from the center of the light receiving element 100 for GE. For example, “optical axis deviation amount 0” indicates that no optical axis deviation occurs. The “optical axis deviation amount 0.05r” indicates that the optical axis is deviated from the center of the light receiving element 100 for GE by 0.05r.
　図１６に示すように、本実施形態に係るＧＥ用受光素子１００は（図１６（ａ）参照）、ギャップが４００ｎｍ近傍で受光比が変化するものの、それ以外の領域では光軸ずれの影響を受けていない。他方、第２実施形態に係るＧＥ用受光素子は（図１６（ｂ）参照）、光軸ずれに起因して受光比が大きく変化している。 As shown in FIG. 16, the light receiving element 100 for GE according to the present embodiment (see FIG. 16A) changes the light receiving ratio when the gap is near 400 nm, but the influence of the optical axis shift is other than that in the region. I have not received it. On the other hand, in the light receiving element for GE according to the second embodiment (see FIG. 16B), the light receiving ratio changes greatly due to the optical axis shift.
　図１７に示すように、本実施形態に係るＧＥ用受光素子１００は（図１７（ａ）参照）、光軸ずれの影響を受けていない。他方、第２実施形態に係るＧＥ用受光素子は（図１７（ｂ）参照）、光軸ずれに起因して受光比が大きく変化している。特に、受光比の傾きが大きく変化しているため、感度を一定に保つことが困難である。 As shown in FIG. 17, the light receiving element 100 for GE according to the present embodiment (see FIG. 17A) is not affected by the optical axis deviation. On the other hand, in the light receiving element for GE according to the second embodiment (see FIG. 17B), the light receiving ratio changes greatly due to the optical axis shift. In particular, it is difficult to keep the sensitivity constant because the slope of the light reception ratio has changed greatly.
　図１８に示すように、本実施形態に係るＧＥ用受光素子１００は（図１８（ａ）参照）、光軸ずれの影響を受けていない。他方、第２実施形態に係るＧＥ用受光素子は（図１８（ｂ）参照）、光軸ずれに起因して受光比が大きく変化している。この場合も、受光比の傾きが大きく変化しているため、感度を一定に保つことが困難である。 As shown in FIG. 18, the light receiving element 100 for GE according to the present embodiment (see FIG. 18A) is not affected by the optical axis deviation. On the other hand, in the light receiving element for GE according to the second embodiment (see FIG. 18B), the light receiving ratio changes greatly due to the optical axis shift. Also in this case, it is difficult to keep the sensitivity constant because the gradient of the light reception ratio is greatly changed.
　このように、本実施形態に係るＧＥ用受光素子１００では、光軸ずれの影響を無くす又は抑制することができ、実用上非常に有利である。 As described above, the light receiving element 100 for GE according to the present embodiment can eliminate or suppress the influence of the optical axis deviation, which is very advantageous in practice.
　＜第４実施形態＞
　本発明の光検出器に係る第４実施形態を、図１９乃至図２３を参照して説明する。第４実施形態では、ＧＥ用受光素子及びギャップエラーサーボ回路の構成が一部異なる以外は、第３実施形態の構成と同様である。よって、第４実施形態について、第３実施形態と重複する説明を省略すると共に、図面上における共通箇所には同一符号を付して示し、基本的に異なる点についてのみ、図１９乃至図２３を参照して説明する。 <Fourth embodiment>
A fourth embodiment of the photodetector of the present invention will be described with reference to FIGS. The fourth embodiment is the same as the configuration of the third embodiment except that the configurations of the light receiving element for GE and the gap error servo circuit are partially different. Accordingly, the description of the fourth embodiment that is the same as that of the third embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. The description will be given with reference.
　図１９は、図１５と同趣旨の、本実施形態に係るＧＥ用受光素子を示す模式図である。本実施形態では特に、遷移領域における光軸ずれの影響（図１６（ａ）参照）を無くすために、第３実施形態に係るＧＥ用受光素子の第２領域１３２に相当する領域を分割している。 FIG. 19 is a schematic diagram showing a light receiving element for GE according to the present embodiment having the same purpose as in FIG. Particularly in this embodiment, in order to eliminate the influence of the optical axis shift in the transition region (see FIG. 16A), a region corresponding to the second region 132 of the light receiving element for GE according to the third embodiment is divided. Yes.
　図１９において、ＧＥ用受光素子１００は、その受光面に、第１検出領域１４１と、該第１検出領域１４１をその外縁側から包囲する第２１検出領域１４２と、該第２１検出領域１４２をその外縁側から包囲する第２２検出領域１４３と、該第２２検出領域をその外縁側から包囲する第３検出領域１４４と、該第３検出領域１４４をその外縁側から包囲する第４検出領域１４５とを備えて構成されている。尚、本実施形態に係る「第２１検出領域１４２」及び「第２２検出領域１４３」は、本発明に係る「第２検出領域」の一例である。 In FIG. 19, the light receiving element 100 for GE includes, on its light receiving surface, a first detection area 141, a 21st detection area 142 surrounding the first detection area 141 from the outer edge side, and the 21st detection area 142. A 22nd detection area 143 surrounding the outer edge side, a third detection area 144 surrounding the 22nd detection area from the outer edge side, and a fourth detection area 145 surrounding the third detection area 144 from the outer edge side. And is configured. The “21st detection area 142” and the “22nd detection area 143” according to the present embodiment are examples of the “second detection area” according to the present invention.
　第１検出領域１４１は、半径ｒ－Ｓの円領域である。第２１検出領域１４２は、内径ｒ－Ｓ、外径ｒ＋Ｓの環状領域である。第２２検出領域１４３は、内径ｒ＋Ｓ、外径（１＋ΔＮ）ｒ＋Ｓの環状領域である。第３検出領域１４４は、内径（１＋ΔＮ）ｒ＋Ｓ、外径Ｒ－ΔＮ・ｒ－Ｓの環状領域である。第４検出領域１４５は、内径Ｒ－ΔＮ・ｒ－Ｓ、外径Ｒ＋Ｓの環状領域である。 The first detection area 141 is a circular area with a radius r−S. The twenty-first detection region 142 is an annular region having an inner diameter r−S and an outer diameter r + S. The twenty-second detection region 143 is an annular region having an inner diameter r + S and an outer diameter (1 + ΔN) r + S. The third detection region 144 is an annular region having an inner diameter (1 + ΔN) r + S and an outer diameter R−ΔN · r−S. The fourth detection region 145 is an annular region having an inner diameter R−ΔN · r−S and an outer diameter R + S.
　次に、本実施形態に係るギャップエラーサーボ回路３０について図２０を参照して説明する。図２０は、図１０と同趣旨の、本実施形態に係るＧＥ用受光素子及びギャップエラーサーボ回路の構成を示すブロック図である。 Next, the gap error servo circuit 30 according to this embodiment will be described with reference to FIG. FIG. 20 is a block diagram showing the configuration of the light receiving element for GE and the gap error servo circuit according to the present embodiment having the same concept as in FIG.
　図２０において、ギャップエラーサーボ回路３０は、第１検出領域１４１から出力される該第１検出領域１４１で受光される光の受光量を示す信号、及び第２１検出領域１４２から出力される該第２１検出領域１４２で受光される光の受光量を示す信号の和を示す信号に基づいて、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度の制御を行う。また、ギャップエラーサーボ回路３０は、第２１検出領域１４２から出力される該第２１検出領域１４２で受光される光の受光量を示す信号、及び第２２検出領域１４３から出力される該第２２検出領域１４３で受光される光の受光量を示す信号の和を示す信号に基づいて、サーボループをクローズ状態とするタイミングの制御を行う。 In FIG. 20, the gap error servo circuit 30 outputs a signal indicating the amount of light received by the first detection region 141 output from the first detection region 141 and the first output output from the twenty-first detection region 142. The speed at which the SIL assembly 209 approaches the optical disk 10 is controlled based on a signal indicating the sum of signals indicating the amount of light received by the 21 detection area 142. The gap error servo circuit 30 also outputs a signal indicating the amount of light received by the 21st detection area 142 output from the 21st detection area 142 and the 22nd detection output from the 22nd detection area 143. Based on a signal indicating the sum of signals indicating the amount of received light received in the region 143, timing control for closing the servo loop is performed.
　また、ギャップエラーサーボ回路３０は、第４検出領域１４５から出力される該第４検出領域１４５で受光される光の受光量を示す信号に基づいて、衝突回避処理を行う。また、ギャップエラーサーボ回路３０は、第２１検出領域１４２から出力される該第２１検出領域１４２で受光される光の受光量を示す信号、第２２検出領域１４３から出力される該第２２検出領域１４３で受光される光の受光量を示す信号、第３検出領域１４４から出力される該第３検出領域１４４で受光される光の受光量を示す信号、及び第４検出領域１４５から出力される該第４検出領域１４５で受光される光の受光量を示す信号の和を示す信号に基づいて、ギャップエラー信号を生成する。 Further, the gap error servo circuit 30 performs a collision avoidance process based on a signal indicating the amount of light received by the fourth detection area 145 output from the fourth detection area 145. Further, the gap error servo circuit 30 outputs a signal indicating the amount of light received by the 21st detection area 142 output from the 21st detection area 142 and the 22nd detection area output from the 22nd detection area 143. A signal indicating the amount of light received at 143, a signal indicating the amount of light received at the third detection region 144 output from the third detection region 144, and an output from the fourth detection region 145 A gap error signal is generated based on a signal indicating the sum of signals indicating the amount of light received by the fourth detection region 145.
　次に、本実施形態に係るＧＥ用受光素子１００における光軸ずれの影響を、図２１を参照して説明する。図２１は、図１６と同趣旨の、遷移領域における受光比の変化を光軸のずれ量毎に示したシミュレーション結果の他の例である。 Next, the influence of the optical axis shift in the GE light receiving element 100 according to the present embodiment will be described with reference to FIG. FIG. 21 is another example of the simulation result showing the change in the light reception ratio in the transition region for each optical axis deviation amount having the same meaning as in FIG. 16.
　図２１に示すように、本実施形態に係るＧＥ用受光素子１００は、遷移領域においても光軸ずれの影響を受けていない。尚、図１６に示す受光比は、第１検出領域１４１及び第２１検出領域１４２の合計の面積に対する受光面積の比を示している。 As shown in FIG. 21, the light receiving element 100 for GE according to the present embodiment is not affected by the optical axis shift even in the transition region. The light reception ratio shown in FIG. 16 indicates the ratio of the light reception area to the total area of the first detection region 141 and the 21st detection region 142.
　尚、ギャップが２００ｎｍ近傍における受光比（本実施形態では、第２１検出領域１４２及び第２２検出領域１４３の合計の面積に対する受光面積の比）の変化は、図１７（ａ）と同様となる。また、過接近領域における受光比の変化は、図１８（ａ）と同様となる。 Note that the change in the light reception ratio (in this embodiment, the ratio of the light reception area to the total area of the twenty-first detection region 142 and the twenty-second detection region 143) in the vicinity of the gap of 200 nm is the same as in FIG. Further, the change in the light reception ratio in the excessively close area is the same as that in FIG.
　従って、本実施形態に係るＧＥ用受光素子１００では、光軸ずれの影響を無くすことができ、実用上非常に有利である。 Therefore, the light receiving element 100 for GE according to this embodiment can eliminate the influence of the optical axis deviation, and is very advantageous in practice.
　次に、以上のように構成された本実施形態に係る光ピックアップ２０において、ギャップエラーサーボ回路３０が実行するレンズアクチュエータ２２０の制御方法について、図２２及び図２３のフローチャートを参照して説明する。 Next, a control method of the lens actuator 220 executed by the gap error servo circuit 30 in the optical pickup 20 according to the present embodiment configured as described above will be described with reference to the flowcharts of FIGS.
　図２２において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ６０１）。 22, first, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S601).
　上記ステップＳ６０１と並行して、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第１検出領域１４１及び第２１検出領域１４２で受光された光の受光量を検出する（ステップＳ６０２）。尚、第１検出領域１４１及び第２検出領域１４２に係る受光量の検出は、連続して又は周期的に実行されてよい。 In parallel with step S601, the gap error servo circuit 30 detects the amount of light received by the first detection region 141 and the twenty-first detection region 142 of the light receiving element 100 for GE (step S602). Note that the detection of the amount of light received in the first detection area 141 and the second detection area 142 may be executed continuously or periodically.
　続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が閾値以上であるか否かを判定する（ステップＳ６０３）。検出された受光量の和が閾値以上であると判定された場合（ステップＳ６０３：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下するようにレンズアクチュエータ２２０を制御する（ステップＳ６０４）。他方、検出された受光量の和が閾値未満であると判定された場合（ステップＳ６０３：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ６０１の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S603). If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S603: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10. (Step S604). On the other hand, when it is determined that the detected sum of received light amounts is less than the threshold value (step S603: No), the gap error servo circuit 30 executes the process of step S601.
　ステップＳ６０４の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ６０５）。 After step S604, the gap error servo circuit 30 controls the lens actuator 220 so as to bring the SIL assembly 209 closer to the optical disc 10 (step S605).
　上記ステップＳ６０５の処理と並行して、ギャップエラーサーボ回路３０は、第２１検出領域１４２及び第２２検出領域１４３で受光された光の受光量を検出する（ステップＳ６０６）。尚、第２２検出領域１４３に係る受光量の検出は、連続して又は周期的に実行されてよい。 In parallel with the process of step S605, the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S606). The detection of the amount of received light according to the 22nd detection region 143 may be executed continuously or periodically.
　続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が閾値以下であるか否かを判定する（ステップＳ６０７）。検出された受光量の和が閾値以下であると判定された場合（ステップＳ６０７：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボループをクローズ状態とする（ステップＳ６０８）。他方、検出された受光量の和が閾値より大きいと判定された場合（ステップＳ６０７：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ６０５の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or less than a threshold value (step S607). When it is determined that the sum of the detected amounts of received light is equal to or less than the threshold (step S607: Yes), the gap error servo circuit 30 closes the gap servo loop (step S608). On the other hand, when it is determined that the detected sum of received light amounts is larger than the threshold (step S607: No), the gap error servo circuit 30 executes the process of step S605.
　尚、本実施形態に係るステップＳ６０３の処理における「閾値」は、ＳＩＬアッセンブリ２０９の光ディスク１０に近づく速度をより低下させるようにレンズアクチュエータ２２０を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第１検出領域１４１及び第２１検出領域１４２に係る受光量の和を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 The “threshold value” in the process of step S603 according to the present embodiment is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is fixed in advance. It is set as a value or a variable value according to some physical quantity or parameter. Such a threshold is obtained by determining the relationship between the gap between the signal level indicating the sum of the amounts of light received in the first detection area 141 and the 21st detection area 142, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on established relationship.
　また、本実施形態に係るステップＳ６０７の処理における「閾値」は、ギャップサーボループをクローズ状態とするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２１検出領域１４２及び第２２検出領域１４３に係る受光量を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 In addition, the “threshold value” in the process of step S607 according to the present embodiment is a value that determines whether or not the gap servo loop is to be closed, and is a fixed value in advance or a variable value according to some physical quantity or parameter Set as Such a threshold value is obtained by calculating the relationship between the gap between the signal level indicating the amount of received light in the twenty-first detection region 142 and the twenty-second detection region 143, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on a relationship.
　次に、ギャップエラーサーボ回路３０が実行する衝突回避処理について説明する。尚、衝突回避処理は、主に、ギャップサーボループがクローズ状態である場合に実行される。 Next, the collision avoidance process executed by the gap error servo circuit 30 will be described. The collision avoidance process is executed mainly when the gap servo loop is in a closed state.
　図２３において、先ず、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第４検出領域１４５で受光された光の受光量を検出する（ステップＳ７０１）。続いて、ギャップエラーサーボ回路３０は、検出された受光量が閾値以下であるか否かを判定する（ステップＳ７０２）。 23, first, the gap error servo circuit 30 detects the amount of light received by the fourth detection region 145 of the GE light receiving element 100 (step S701). Subsequently, the gap error servo circuit 30 determines whether or not the detected amount of received light is equal to or less than a threshold value (step S702).
　検出された受光量が閾値以下であると判定された場合（ステップＳ７０２：Ｙｅｓ）、ギャップエラーサーボ回路３０は、衝突回避処理を実行する（ステップＳ７０３）。他方、検出された受光量が閾値より大きいと判定された場合（ステップＳ７０２：Ｎｏ）、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第２１検出領域１４２及び第２２検出領域１４３で受光された光の受光量を検出する（ステップＳ７０４）。 When it is determined that the detected amount of received light is equal to or less than the threshold (step S702: Yes), the gap error servo circuit 30 executes a collision avoidance process (step S703). On the other hand, when it is determined that the detected amount of received light is greater than the threshold (step S702: No), the gap error servo circuit 30 is received by the 21st detection region 142 and the 22nd detection region 143 of the GE light receiving element 100. The amount of received light is detected (step S704).
　続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が閾値以上であるか否かを判定する（ステップＳ７０５）。検出された受光量の和が閾値以上であると判定された場合（ステップＳ７０５：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボをオフ状態にする（ステップＳ７０６）。他方、検出された受光量の和が閾値より小さいと判定された場合（ステップＳ７０５：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ７０１の処理を実行する。 Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S705). If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S705: Yes), the gap error servo circuit 30 turns off the gap servo (step S706). On the other hand, when it is determined that the detected sum of received light amounts is smaller than the threshold value (step S705: No), the gap error servo circuit 30 executes the process of step S701.
　尚、本変形例に係るステップＳ７０２の処理における「閾値」は、上述した第２実施形態に係るステップＳ４０２の処理における「閾値」と同様に設定すればよい。本実施形態に係るステップＳ７０５の処理における「閾値」は、ギャップサーボをオフ状態にするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２１検出領域１４２及び第２２検出領域１４３に係る受光量の和を示す信号レベルと、ギャップとの関係を求め、該求められた関係に基づいて設定すればよい。 The “threshold value” in the process of step S702 according to the present modification may be set in the same manner as the “threshold value” in the process of step S402 according to the second embodiment described above. The “threshold value” in the process of step S705 according to the present embodiment is a value that determines whether or not to turn off the gap servo, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter. The Such a threshold is obtained by determining the relationship between the gap between the signal level indicating the sum of the received light amounts related to the twenty-first detection region 142 and the twenty-second detection region 143, for example, experimentally, empirically, or by simulation. What is necessary is just to set based on established relationship.
　＜変形例＞
　次に、本実施形態の変形例について、図２４のフローチャートを参照して説明する。 <Modification>
Next, a modification of the present embodiment will be described with reference to the flowchart of FIG.
　図２４において、先ず、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ８０１）。 24, first, the gap error servo circuit 30 controls the lens actuator 220 to bring the SIL assembly 209 closer to the optical disc 10 (step S801).
　上記ステップＳ８０１と並行して、ギャップエラーサーボ回路３０は、ＧＥ用受光素子１００の第１検出領域１４１及び第２１検出領域１４２で受光された光の受光量を検出する（ステップＳ８０２）。続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が閾値以上であるか否かを判定する（ステップＳ８０３）。 In parallel with step S801, the gap error servo circuit 30 detects the amount of light received by the first detection region 141 and the twenty-first detection region 142 of the light receiving element 100 for GE (step S802). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or greater than a threshold value (step S803).
　検出された受光量の和が閾値以上であると判定された場合（ステップＳ８０３：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度を低下するようにレンズアクチュエータ２２０を制御する（ステップＳ８０４）。他方、検出された受光量の和が閾値未満であると判定された場合（ステップＳ８０３：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ８０１の処理を実行する。 If it is determined that the sum of the detected amounts of received light is equal to or greater than the threshold (step S803: Yes), the gap error servo circuit 30 controls the lens actuator 220 so as to reduce the speed at which the SIL assembly 209 approaches the optical disc 10. (Step S804). On the other hand, when it is determined that the sum of the detected amounts of received light is less than the threshold (step S803: No), the gap error servo circuit 30 executes the process of step S801.
　ステップＳ８０４の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ８０５）。 After step S804, the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S805).
　上記ステップＳ８０５の処理と並行して、ギャップエラーサーボ回路３０は、第２１検出領域１４２及び第２２検出領域１４３で受光された光の受光量を検出する（ステップＳ８０６）。続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が第１閾値以下であるか否かを判定する（ステップＳ８０７）。 In parallel with the processing in step S805, the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S806). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or less than the first threshold value (step S807).
　検出された受光量の和が第１閾値以下であると判定された場合（ステップＳ８０７：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９が光ディスク１０に近づく速度をより低下するようにレンズアクチュエータ２２０を制御する（ステップＳ８０８）。他方、検出された受光量の和が第１閾値より大きいと判定された場合（ステップＳ８０７：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ８０５の処理を実行する。 When it is determined that the sum of the detected amounts of received light is equal to or less than the first threshold (step S807: Yes), the gap error servo circuit 30 causes the lens actuator to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10. 220 is controlled (step S808). On the other hand, when it is determined that the detected sum of received light amounts is larger than the first threshold (step S807: No), the gap error servo circuit 30 executes the process of step S805.
　ステップＳ８０８の処理の後、ギャップエラーサーボ回路３０は、ＳＩＬアッセンブリ２０９を光ディスク１０に近づけるようにレンズアクチュエータ２２０を制御する（ステップＳ８０９）。 After step S808, the gap error servo circuit 30 controls the lens actuator 220 so that the SIL assembly 209 is brought closer to the optical disc 10 (step S809).
　上記ステップＳ８０９の処理と並行して、ギャップエラーサーボ回路３０は、第２１検出領域１４２及び第２２検出領域１４３で受光された光の受光量を検出する（ステップＳ８１０）。続いて、ギャップエラーサーボ回路３０は、検出された受光量の和が第２閾値以下であるか否かを判定する（ステップＳ８１１）。 In parallel with the processing in step S809, the gap error servo circuit 30 detects the amount of light received by the 21st detection area 142 and the 22nd detection area 143 (step S810). Subsequently, the gap error servo circuit 30 determines whether or not the detected sum of received light amounts is equal to or smaller than a second threshold value (step S811).
　検出された受光量の和が第２閾値以下であると判定された場合（ステップＳ８１１：Ｙｅｓ）、ギャップエラーサーボ回路３０は、ギャップサーボループをクローズ状態とする（ステップＳ８１１）。他方、検出された受光量の和が第２閾値より大きいと判定された場合（ステップＳ８１１：Ｎｏ）、ギャップエラーサーボ回路３０は、ステップＳ８０９の処理を実行する。 If it is determined that the sum of the detected amounts of received light is equal to or smaller than the second threshold (step S811: Yes), the gap error servo circuit 30 closes the gap servo loop (step S811). On the other hand, when it is determined that the detected sum of received light amounts is larger than the second threshold (step S811: No), the gap error servo circuit 30 executes the process of step S809.
　尚、本変形例に係るステップＳ８０３の処理における「閾値」は、上述した第４実施形態に係るステップＳ６０３の処理における「閾値」と同様に設定すればよい。 It should be noted that the “threshold value” in the process of step S803 according to the present modification may be set similarly to the “threshold value” in the process of step S603 according to the fourth embodiment described above.
　本変形例に係るステップＳ８０７における「第１閾値」は、ＳＩＬアッセンブリ２０９の光ディスク１０に近づく速度をより低下させるようにレンズアクチュエータ２２０を制御するか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第１閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２１検出領域１４２及び第２２検出領域１４３に係る受光量の和とギャップとの関係を求め、該求められた関係に基づいて、レンズアクチュエータ２２０に対し停止要求があった際に慣性によりＳＩＬアッセンブリ２０９が移動する距離と、ギャップとが等しくなる受光量として、又は該受光量よりも所定量だけ多きい受光量として設定すればよい。 The “first threshold value” in step S807 according to the present modification is a value that determines whether or not to control the lens actuator 220 so as to further reduce the speed at which the SIL assembly 209 approaches the optical disc 10, and is set as a fixed value in advance. Or a variable value according to some physical quantity or parameter. Such a first threshold value is obtained experimentally, empirically, or by simulation, for example, by determining the relationship between the sum of received light amounts and the gap in the twenty-first detection region 142 and the twenty-second detection region 143. Based on the above, when the lens actuator 220 is requested to stop, the distance that the SIL assembly 209 moves due to inertia and the received light amount equal to the gap, or the received light amount that is larger than the received light amount by a predetermined amount You only have to set it.
　本変形例に係る「第２閾値」は、ギャップサーボループをクローズ状態とするか否かを決定する値であり、予め固定値として、或いは何らかの物理量又はパラメータに応じた可変値として設定される。このような第２閾値は、実験的若しくは経験的に、又はシミュレーションによって、例えば第２１検出領域１４２及び第２２検出領域に係る受光量の和とギャップとの関係を求め、該求められた関係に基づいて、ギャップサーボループをクローズ状態とすべき距離に対応する受光量として設定すればよい。 The “second threshold value” according to this modification is a value that determines whether or not the gap servo loop is closed, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a second threshold value is obtained experimentally, empirically, or by simulation, for example, by obtaining the relationship between the sum of received light amounts and the gap according to the twenty-first detection region 142 and the twenty-second detection region. Based on this, the received light amount corresponding to the distance at which the gap servo loop should be closed may be set.
　尚、本発明は、上述した実施形態に限られるものではなく、請求の範囲及び明細書全体から読み取れる発明の要旨、或いは思想に反しない範囲で適宜変更可能であり、そのような変更を伴う光検出器及び光ピックアップ並びに制御方法もまた、本発明の技術的範囲に含まれるものである。 The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Detectors and optical pickups and control methods are also included in the technical scope of the present invention.
１０　　光ディスク
２０　　光ピックアップ
３０　　ギャップエラーサーボ回路
１００　　ＧＥ用受光素子
１１１、１２１、１３１、１４１　　第１検出領域
１１２、１２２、１３２　　第２検出領域
１２３、１３３、１４４　　第３検出領域
１２４、１３４、１４５　　第４検出領域
１４２　　第２１検出領域
１４３　　第２２検出領域
２０１　　半導体レーザ
２０９　　ＳＩＬアッセンブリ
２１０　　ＳＩＬ
２２０　　レンズアクチュエータ 10 Optical disk 20 Optical pickup 30 Gap error servo circuit 100 GE light receiving elements 111, 121, 131, 141 First detection areas 112, 122, 132 Second detection areas 123, 133, 144 Third detection areas 124, 134, 145 First 4 detection area 142 21st detection area 143 22nd detection area 201 Semiconductor laser 209 SIL assembly 210 SIL
220 Lens actuator

Claims (12)

  1. 　記録媒体に対してエバネッセント光を発生可能なレンズを備える光ピックアップに設けられた光検出器であって、
    　当該光検出器の受光面に、
    　前記レンズの前記記録媒体側の面で反射された反射光の第１部分を検出する第１検出領域と、
    　前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域と
    　を備えることを特徴とする光検出器。     A photodetector provided in an optical pickup including a lens capable of generating evanescent light with respect to a recording medium,
    On the light receiving surface of the photodetector,
    A first detection region for detecting a first portion of reflected light reflected by the surface of the lens on the recording medium side;
    And a second detection region that at least partially surrounds the first detection region and detects a second portion of the reflected light different from the first portion.
  2. 　前記第１検出領域の外縁及び前記第２検出領域の内縁の各々は、前記第１検出領域の中心を共有する同心円の少なくとも一部を構成することを特徴とする請求項１に記載の光検出器。 2. The light detection according to claim 1, wherein each of an outer edge of the first detection region and an inner edge of the second detection region constitutes at least a part of a concentric circle sharing a center of the first detection region. vessel.
  3. 　前記受光面に、
    　前記第２検出領域を少なくとも部分的に包囲し、前記第１及び第２部分とは異なる前記反射光の第３部分を検出する第３検出領域と、
    　前記第３検出領域を少なくとも部分的に包囲し、前記第１乃至第３部分とは異なる前記反射光の第４部分を検出する第４検出領域と
    　を更に備えることを特徴とする請求項１に記載の光検出器。     On the light receiving surface,
    A third detection region that at least partially surrounds the second detection region and detects a third portion of the reflected light that is different from the first and second portions;
    The fourth detection region further comprising: a fourth detection region that at least partially surrounds the third detection region and detects a fourth portion of the reflected light different from the first to third portions. The described photodetector.
  4. 　前記第１検出領域の外縁、前記第２検出領域の外縁及び前記第３検出領域の外縁の各々は、前記第１検出領域の中心を共有する同心円の少なくとも一部を構成することを特徴とする請求項３に記載の光検出器。 Each of the outer edge of the first detection region, the outer edge of the second detection region, and the outer edge of the third detection region constitutes at least a part of a concentric circle sharing the center of the first detection region. The photodetector according to claim 3.
  5. 　記録媒体に光を照射する光源と、
    　前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、
    　前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、
    　前記レンズを駆動可能な駆動手段と、
    　前記光検出器から出力される信号に基づいて、前記レンズを駆動するように前記駆動手段を制御する制御手段と
    　を備え、
    　前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する
    　ことを特徴とする光ピックアップ。     A light source for irradiating the recording medium with light;
    A lens arranged in the optical path of the irradiated light and capable of generating evanescent light with respect to the recording medium;
    A photodetector that receives reflected light reflected by at least the surface of the lens on the recording medium side of the irradiated light;
    Driving means capable of driving the lens;
    Control means for controlling the driving means to drive the lens based on a signal output from the photodetector; and
    The photodetector includes a first detection region for detecting a first portion of the reflected light on a light receiving surface of the photodetector, and at least partially surrounds the first detection region. An optical pickup comprising: a second detection region that detects a different second portion of the reflected light.
  6. 　前記第１検出領域の外縁は、前記反射光のうち開口数が１に相当する光が前記受光面に形成する円の外縁に対応することを特徴とする請求項５に記載の光ピックアップ。 6. The optical pickup according to claim 5, wherein an outer edge of the first detection region corresponds to an outer edge of a circle formed on the light receiving surface by light having a numerical aperture of 1 among the reflected light.
  7. 　前記第２検出領域の内縁は、前記反射光のうち開口数が１に相当する光が前記受光面に形成する円の外縁に対応することを特徴とする請求項５に記載の光ピックアップ。 6. The optical pickup according to claim 5, wherein an inner edge of the second detection region corresponds to an outer edge of a circle formed on the light receiving surface by light having a numerical aperture of 1 among the reflected light.
  8. 　記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する光ピックアップの制御方法であって、
    　前記第１検出領域の受光量に応じて、前記レンズの前記記録媒体に近づく速度を低下させるように前記駆動手段を制御する減速工程を備えることを特徴とする制御方法。     A light source for irradiating the recording medium with light, a lens disposed in an optical path of the irradiated light and capable of generating evanescent light with respect to the recording medium, and at least the recording medium of the lens among the irradiated light A photodetector that receives the reflected light reflected by the surface on the side, and drive means that can drive the lens, wherein the photodetector has a first surface of the reflected light on the light receiving surface of the photodetector. An optical pickup comprising: a first detection region for detecting a portion; and a second detection region for at least partially surrounding the first detection region and detecting a second portion of the reflected light different from the first portion. A control method,
    A control method comprising: a decelerating step of controlling the driving unit so as to reduce the speed of the lens approaching the recording medium in accordance with the amount of light received in the first detection region.
  9. 　前記減速工程の後、前記第２検出領域の受光量に応じて、サーボループをクローズ状態とするクローズ工程を更に備えることを特徴とする請求項８に記載の制御方法。 9. The control method according to claim 8, further comprising a closing step for closing the servo loop in accordance with the amount of light received in the second detection region after the deceleration step.
  10. 　前記減速工程の後、前記第２検出領域の受光量が第１閾値より小さいことを条件に、前記レンズの前記記録媒体に近づく速度をより低下させるように前記駆動手段を制御する第２減速工程と、
    　前記第２減速工程の後、前記第２検出領域の受光量が第２閾値より小さいことを条件に、サーボループをクローズ状態とするクローズ工程と
    　を更に備えることを特徴とする請求項８に記載の制御方法。     After the deceleration step, on the condition that the amount of light received in the second detection region is smaller than a first threshold value, a second deceleration step for controlling the driving means to further reduce the speed of the lens approaching the recording medium. When,
    9. The closing step of closing the servo loop on the condition that the amount of light received in the second detection region is smaller than a second threshold after the second deceleration step. Control method.
  11. 　記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域とを有する光ピックアップの制御方法であって、
    　前記第１検出領域の受光量と前記第２検出領域の受光量との差分を演算する演算工程と、
    　前記演算された差分が一旦減少した後に増加したことを条件に、前記レンズの前記記録媒体に近づく速度を低下させるように前記駆動手段を制御する減速工程と
    　を備えることを特徴とする制御方法。     A light source for irradiating the recording medium with light, a lens disposed in an optical path of the irradiated light and capable of generating evanescent light with respect to the recording medium, and at least the recording medium of the lens among the irradiated light A photodetector that receives the reflected light reflected by the surface on the side, and drive means that can drive the lens, wherein the photodetector has a first surface of the reflected light on the light receiving surface of the photodetector. An optical pickup comprising: a first detection region for detecting a portion; and a second detection region for at least partially surrounding the first detection region and detecting a second portion of the reflected light different from the first portion. A control method,
    A calculation step of calculating a difference between the received light amount of the first detection region and the received light amount of the second detection region;
    And a decelerating step of controlling the driving means so as to reduce the speed at which the lens approaches the recording medium, on condition that the calculated difference has increased after being once decreased.
  12. 　記録媒体に光を照射する光源と、前記照射された光の光路に配置され、前記記録媒体に対してエバネッセント光を発生可能なレンズと、前記照射された光のうち少なくとも前記レンズの前記記録媒体側の面で反射された反射光を受光する光検出器と、前記レンズを駆動可能な駆動手段とを備え、前記光検出器は、前記光検出器の受光面に、前記反射光の第１部分を検出する第１検出領域と、前記第１検出領域を少なくとも部分的に包囲し、前記第１部分とは異なる前記反射光の第２部分を検出する第２検出領域と、前記第２検出領域を少なくとも部分的に包囲し、前記第１及び第２部分とは異なる前記反射光の第３部分を検出する第３検出領域と、前記第３検出領域を少なくとも部分的に包囲し、前記第１乃至第３部分とは異なる前記反射光の第４部分を検出する第４検出領域とを有する光ピックアップの制御方法であって、
    　前記第４検出領域の受光量に応じて、前記レンズが前記記録媒体に衝突しないように前記駆動手段を制御する衝突回避工程を備えることを特徴とする制御方法。     A light source for irradiating the recording medium with light, a lens disposed in an optical path of the irradiated light and capable of generating evanescent light with respect to the recording medium, and at least the recording medium of the lens among the irradiated light A photodetector that receives the reflected light reflected by the surface on the side, and drive means that can drive the lens, wherein the photodetector has a first surface of the reflected light on the light receiving surface of the photodetector. A first detection region for detecting a portion, a second detection region for at least partially surrounding the first detection region and detecting a second portion of the reflected light different from the first portion, and the second detection A third detection region that at least partially surrounds the region and detects a third portion of the reflected light that is different from the first and second portions; and at least partially surrounds the third detection region; The reflected light different from the first to third parts A method of controlling an optical pickup and a fourth detection area for detecting the fourth portion,
    A control method comprising: a collision avoidance step of controlling the driving means so that the lens does not collide with the recording medium in accordance with the amount of light received in the fourth detection region.
PCT/JP2009/062383 2009-07-07 2009-07-07 Light detector, optical pickup and control method WO2011004461A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008511090A (en) * 2004-08-23 2008-04-10 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Optical scanning device
WO2008114406A1 (en) * 2007-03-20 2008-09-25 Pioneer Corporation Optical pickup, and reproducer
JP2009093745A (en) * 2007-10-05 2009-04-30 Sanyo Electric Co Ltd Optical pickup device, optical disk device, and gap adjusting device and method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008511090A (en) * 2004-08-23 2008-04-10 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Optical scanning device
WO2008114406A1 (en) * 2007-03-20 2008-09-25 Pioneer Corporation Optical pickup, and reproducer
JP2009093745A (en) * 2007-10-05 2009-04-30 Sanyo Electric Co Ltd Optical pickup device, optical disk device, and gap adjusting device and method thereof

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