WO2006022068A1 - 光集積ユニットおよびそれを備えた光ピックアップ装置 - Google Patents
光集積ユニットおよびそれを備えた光ピックアップ装置 Download PDFInfo
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- WO2006022068A1 WO2006022068A1 PCT/JP2005/011134 JP2005011134W WO2006022068A1 WO 2006022068 A1 WO2006022068 A1 WO 2006022068A1 JP 2005011134 W JP2005011134 W JP 2005011134W WO 2006022068 A1 WO2006022068 A1 WO 2006022068A1
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- integrated unit
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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
- G11B7/1353—Diffractive elements, e.g. holograms or gratings
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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
- G11B7/123—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
Definitions
- the present invention relates to an optical integrated unit and an optical pickup device including the same, and more specifically, to realize downsizing of an optical pickup used when recording or reproducing information on an optical recording medium such as an optical disk. And an optical pickup device having the same.
- Patent Document 1 Japanese Patent Laid-Open No. 2001-273666 (published on Oct. 5, 2001) proposes an optical integrated unit including a hologram element and a beam splitter, and an optical pickup device including the optical integrated unit. ing. The principles of the optical integrated unit and the optical pickup device will be described below with reference to FIGS.
- FIG. 13 is a configuration diagram of this optical pickup device.
- Light emitted from the light source mounted on the optical integrated unit 101 is collimated by the collimator lens 102 and then condensed on the optical disc 104 through the objective lens 103. Then, the return light reflected from the optical disc 104 is condensed again on the light receiving element mounted on the optical integrated unit 101 via the objective lens 103 and the collimator lens 102.
- the optical disc 104 includes a substrate 104a, a cover layer 104b through which a light beam is transmitted, and a recording layer 104c used for recording / reproducing information.
- FIG. 14 is a diagram showing a detailed structure of the optical integrated unit 101.
- the light 120 (optical axis center 122) emitted from the semiconductor laser (light source) 105 is divided into a main beam (0th-order diffracted light) and two sub-beams ( ⁇ 1st-order diffracted light) by a three-beam diffraction grating 106.
- the sub beam ( ⁇ 1st order diffraction) (Light) is not shown.
- the return light 121 passes through the 1Z4 wavelength plate 108, is reflected by the PBS surface 107a and the reflection mirror surface 107b, and enters the hologram element 109.
- the return light 121 incident on the hologram element 109 is diffracted and divided into + first-order diffracted light (optical axis center 125 a) and first-order diffracted light (optical axis center 125 b), and enters the light receiving element 110.
- the return light 121 In order to avoid complication of the drawing, only the light beam centered on the optical axis is shown as the return light 121.
- the light emitted from the semiconductor laser 105 is linearly polarized light (P-polarized light) whose polarization direction is the X-axis direction.
- P-polarized light linearly polarized light
- the return light from the optical disk 104 is incident on the 1Z4 wavelength plate 108 again, becomes linearly polarized light (S-polarized light) in the y-axis direction, and is reflected by the PBS surface 107a.
- FIG. 15 is a diagram for explaining the hologram pattern of the hologram element 109 and the light receiving portion pattern of the light receiving element 110.
- the hologram element 109 is divided into three regions 109a to 109c by a dividing line 109x in the X-axis direction corresponding to the tracking direction of the optical disk 104 and a dividing line 109y in the y-axis direction corresponding to the direction along the track.
- the light receiving element 110 includes six light receiving portions 110a to 110f that detect + first-order diffracted light by the hologram element 109, and three light receiving portions l lOg to detect L first order diffracted light. .
- the focus error signal (FES) is detected by the single knife edge method, and the tracking error signal (TES) is detected by the differential push-pull (DPP) method. It is used to detect TES by the information signal (RF signal) and the phase difference (DPD) method.
- the frequency response of the light receiving element required for servo signal detection such as FES detection and TES detection by the DPP method is generally detectable even at a sufficiently lower frequency than the RF signal.
- a TES detection using an RF signal or phase difference (DPD) method requires a light-receiving element that responds quickly.
- the RF signal detection light receiving portion has a high RF signal. While it is necessary to reduce the area of the light receiving unit to support high-speed reproduction, the response to the light receiving unit for FES detection may be slow, but the area of the light receiving unit is increased to ensure a sufficient pull-in range. There were two demands that were difficult to balance. In the conventional technology, both + first-order diffracted light and first-order diffracted light are used to share the role of signal generation, thereby ensuring both high-speed RF signal acquisition and FES signal pull-in range. .
- the diffraction grating 106 for generating three beams is arranged on the light source 105 side in the composite prism 107 as shown in FIG.
- the hologram element 109 for generating the servo signal is also arranged on the light receiving element 110 side in the composite prism 107.
- the distance (optical path length) from the light receiving element 110 to the hologram element 109 is also short as the light source power is short to the diffraction grating 106 (optical path length).
- the beam diameter of the light beam incident on the diffraction element (diffraction grating 106, hologram element 109) becomes small.
- the distance from the light source 105 to the diffraction grating 106 (and the distance from the hologram element 109 to the light receiving element 110) is set in the air. Lmn in terms of optical path length!
- the beam diameter on the diffractive element is about ⁇ .2 ⁇ 0.4mm.
- the distance from the hologram element 109 to the light receiving element 110 cannot be sufficiently secured and the distance from the hologram element 109 to the light receiving element 110 is about 1 mm in terms of the optical path length in the air
- the separation of the + first-order diffracted light and the first-order diffracted light on the element 110 is set to about 0.8 mm, the diffraction angle becomes about 18 deg.
- the grating pitch for realizing this diffraction angle is about 1.4 m in the case of a blue optical system having a wavelength of 405 nm, and the manufacture of the hologram element 109 becomes difficult.
- the first-order diffracted light and the first The role of folding light is divided, and the first-order diffracted light is detected by a dedicated light receiving unit for signals that require high-speed response.
- the diffracted light is affected by wavelength fluctuations and tolerances, it is necessary to design the light receiving unit to be large in consideration of the fact that the condensing position on the light receiving element 110 fluctuates. This limitation on the area of the light receiving area has been a factor limiting the high-speed reproduction of RF signals.
- the present invention has been made in view of the above problems, and an object of the present invention is to reduce the influence of changes over time and temperature changes by increasing the light beam diameter on the diffraction element as much as possible. Force Increase the optical path length to the light receiving element to reduce the diffraction angle (increase the grating pitch) to facilitate the manufacture of the diffraction element, and detect the RF signal using the non-diffracted light from the diffraction element.
- An object of the present invention is to provide an optical integrated unit capable of realizing a response (high-speed reproduction by rotating an optical disk at high speed) and an optical pickup device including the same.
- an optical integrated unit reflects a light source that emits a light beam, a light beam that transmits the light beam, and a return light of the light beam reflected by the optical information recording medium.
- a light guide means provided on the optical axis of the light beam for guiding the return light in a direction different from the light source, and receiving the return light guided by the light guide means.
- the diffractive means for diffracting the light beam and the return light is placed on the optical axis of the light beam and at a position where the light beam transmitted through the functional surface is incident. It is characterized by having.
- the functional surface is preferably a polarizing beam splitter surface.
- the light beam transmitted through the light guide unit is incident on the diffraction unit, and the light receiving element is diffracted by the diffraction unit and passes through the light guide unit. The return light is received.
- the light beam emitted from the light source passes through the light guide unit and then enters the diffraction unit. For this reason, the optical path length of the light beam from the light source until it enters the diffraction means can be increased.
- the beam diameter of the light beam incident on the diffracting means can be reduced by arranging the light guiding means between the light source and the diffracting means. ! Can be larger than the case.
- the light receiving element receives the return light that is diffracted by the diffraction means and passes through the light guide means. That is, it passes through the light guide means after passing through the diffraction means and before entering the light receiving element. Therefore, the optical path length of the diffracted return light until it is received by the light receiving element can be increased.
- the diffracted light (returned light) on the light receiving element can be favorably separated.
- the diffracting unit diffracts polarized light having a predetermined polarization vibration surface, and transmits polarized light having a polarization vibration surface perpendicular to the polarization vibration surface as it is.
- a polarization diffraction element is preferable.
- the diffraction means includes a first hologram region and a second hologram region, each of which diffracts polarized light having a predetermined polarization vibration surface.
- the polarization diffraction element that transmits the polarized light having a polarization vibration surface perpendicular to the polarization vibration surface as it is, and the first hologram region and the second hologram region are the predetermined polarizations provided respectively. It is preferable that the vibration planes are arranged on the optical axis of the light beam so that the vibration surfaces are perpendicular to each other!
- the light beam can be diffracted and the return light can be diffracted.
- Each of the first hologram area and the second hologram area is provided with a grating, and has the predetermined polarization transmission axis of light (polarized light) incident on each hologram area.
- the polarized light is diffracted by the grating and becomes diffracted light.
- the diffraction angle of the diffracted light is determined by the pitch of the grating.
- the first hologram region and the second hologram region are arranged on the optical axis of the light beam so that the predetermined polarization vibration planes provided in each of the first hologram region and the second hologram region are perpendicular to each other. Therefore, the polarized light diffracted in the first hologram region passes through the second hologram region as it is, and conversely, the polarized light diffracted in the second hologram region passes through the first hologram region. It passes through as it is.
- the light beam and the return light can be diffracted by providing the diffractive means having such a configuration.
- the “diffracted light” is not particularly limited, and includes diffracted light having a diffraction angle and non-diffracted light (0th order diffracted light) having no diffraction angle. Including both.
- the first hologram region divides the return light into non-diffracted light and diffracted light.
- the optical integrated unit according to the present invention can increase the optical path length of the diffracted return light received by the light receiving element, the return light is converted into non-diffracted light and diffracted light. Even when the light is diffracted, the light can be sufficiently separated on the light receiving element.
- the diffracted light passes through the long optical path.
- the distance between the diffracted light and the non-diffracted light is widened, and the diffracted light and the non-diffracted light can be well separated on the light receiving element.
- the second hologram region divides the light beam into three beams.
- the light receiving element includes a light receiving unit that receives the diffracted light and a light receiving unit that receives the non-diffracted light.
- the optical integrated unit according to the present invention has the diffracted return light (diffracted light and light). Therefore, even if the diffracted light and the non-diffracted light cannot be sufficiently separated in the vicinity of the first hologram region, the diffracted light and the non-diffracted light on the light receiving element can be increased. It becomes possible to separate non-diffracted light well.
- the light receiving element includes a light receiving portion that receives the non-diffracted light, the non-diffracted light can be used for detection of a high-speed signal.
- the non-diffracted light can be used to detect a high-speed signal such as an RF signal or a DPD TES signal.
- the diffracted light can be used for servo signal detection.
- the high-speed signal is detected using diffracted light, it is affected by wavelength fluctuations and tolerances, so that the light collection position varies on the light receiving element. It is necessary to design the light receiving part to be large, and such restriction on the light receiving part area becomes a factor that limits high-speed reproduction of the RF signal. However, in the optical integrated unit according to the present invention, There is no restriction on the area. Therefore, it is possible to realize high-speed reproduction of a good RF signal.
- the grating pitch of the first hologram region and the second hologram region can be formed large.
- the diffraction means first hologram region and second hologram region
- the light guide means includes a reflective surface that reflects the return light reflected by the functional surface.
- the diffracted return light can be reflected in a desired direction, and the optical path length can be further increased accordingly.
- the light source is a semiconductor laser housed in a hermetically sealed package.
- the light source is not exposed to the outside air, and characteristic deterioration occurs.
- the light source can be adjusted in position with respect to the light receiving element and the light guiding means.
- the light source and the light receiving element are accurately positioned, even when a semiconductor laser housed in a package is used as the light source, the return light can be reliably incident on the light receiving element. Therefore, it is possible to minimize the area of the light receiving portion that receives non-diffracted light, and high-speed signal detection can be performed satisfactorily.
- the optical integrated unit according to the present invention is preferably provided with a 1Z4 wavelength plate on the side opposite to the side where the light guiding unit of the diffractive unit is disposed.
- the linearly polarized light is irradiated as circularly polarized light on the optical information recording medium by transmitting through the 1Z4 wavelength plate. Therefore, it is not easily affected by the birefringence of the substrate of the optical information recording medium when generating an RF signal. Furthermore, since the return light reflected on the optical information recording medium is linearly polarized light whose polarization oscillation plane is orthogonal to the linear polarization, it is incident on the diffracting means and is diffracted and reflected on the functional surface. The utilization efficiency of the reflected return light can be increased.
- the optical integrated unit according to the present invention preferably further comprises a 1Z2 wavelength plate on the optical axis of the light beam until it enters the functional surface.
- the light source when the functional surface (polarization beam splitter surface) has a characteristic of transmitting only a light beam having a P-polarized polarization vibration surface, the light source has a P-polarization polarization vibration surface.
- the layout is limited to emit light. Therefore, by providing a 1Z2 wavelength plate on the optical axis of the light beam until it enters the functional surface, the light source emits a light beam other than the P-polarized light beam, that is, an S-polarized light beam. Even if it does, it can be applied without reducing the light utilization efficiency. In other words, there is an effect that the degree of freedom of light source layout is increased.
- the optical pickup device can be mounted with an optical integrated unit having the above-described configuration.
- the optical pickup device can realize a small and light weight.
- FIG. 1 (a)] is a configuration diagram showing a configuration of an optical integrated unit in the first embodiment according to the present invention.
- FIG. 1 (b) is a top view of the optical integrated unit shown in FIG. 1 (a).
- FIG. 2 is a schematic configuration diagram showing the configuration of an optical pickup device using the optical integrated unit shown in FIGS. 1 (a) and 1 (b).
- FIG. 2 is a schematic configuration diagram showing the configuration of an optical pickup device using the optical integrated unit shown in FIGS. 1 (a) and 1 (b).
- FIG. 3 is a configuration diagram showing a hologram pattern of a first polarization hologram element used in the optical integrated unit in each embodiment according to the invention.
- FIG. 4 is a configuration diagram showing a hologram pattern of a second polarization hologram element used in the optical integrated unit in each embodiment according to the invention.
- FIG. 5 (a) is a diagram for explaining a light receiving portion pattern of a light receiving element used in an optical integrated unit in the first to fifth embodiments according to the present invention, in which spherical aberration occurs in the light receiving portion pattern.
- FIG. 6 is a diagram showing a light receiving state of a light beam in the case.
- FIG. 5 (b) is a diagram for explaining a light receiving portion pattern of a light receiving element used in the optical integrated unit in the first to fifth embodiments according to the present invention, and the state force objective lens in FIG. FIG. 6 is a view showing a light receiving state of a light beam when approaching an optical disc.
- FIG. 6 (a) is a diagram for explaining the shape of the light beam on the light receiving element when the optical disc is positioned at the focal point of the objective lens when spherical aberration remains.
- FIG. 6 (b) is a diagram for explaining the shape of the light beam on the light receiving element when the optical disc is located at the focal point of the objective lens when spherical aberration remains.
- FIG. 7 is a diagram showing another configuration of the optical integrated unit in the first embodiment according to the present invention. It is a chart.
- FIG. 8 (a) is a configuration diagram showing a configuration of an optical integrated unit in the second embodiment according to the present invention.
- FIG. 8 (b) is a top view of the optical integrated unit shown in FIG. 8 (a).
- FIG. 9 (a) is a configuration diagram showing a configuration of an optical integrated unit in the third embodiment according to the present invention.
- FIG. 9 (b) is a top view of the optical integrated unit shown in FIG. 9 (a).
- FIG. 10 is a configuration diagram showing a configuration of an optical integrated unit in a fourth embodiment according to the present invention.
- FIG. 11 (a) is a diagram for explaining a light receiving portion pattern of a light receiving element used in an optical integrated unit according to a fifth embodiment of the present invention, in which spherical aberration occurs in the light receiving portion pattern. It is the figure which showed the light-receiving state of the light beam in a case.
- FIG. 11 (b) is a diagram for explaining a light-receiving part pattern of a light-receiving element used in an optical integrated unit in the fifth embodiment according to the present invention, in which the state force in FIG. It is the figure which showed the light-receiving state of the light beam in the case of.
- FIG. 12 shows a 1Z4 wavelength plate provided in the optical integrated unit in each embodiment according to the present invention.
- the optical pickup device is detached from the optical integrated unit and attached to the optical integrated unit as a configuration of the optical pickup device.
- FIG. 13 is a configuration diagram of an optical pickup device in the prior art.
- FIG. 14 is a configuration diagram of an optical integrated unit used in an optical pickup device in the prior art.
- FIG. 15 is an explanatory diagram for explaining a hologram pattern of a hologram element provided in an optical integrated unit used in an optical pickup device in the prior art and a light receiving portion pattern of a light receiving element.
- the optical integrated unit of the present invention is an optical information recording / reproducing apparatus that optically records and reproduces information with respect to an optical disc (optical information recording medium). The case where it is used for a pickup device will be described.
- FIG. 2 is a schematic diagram showing a configuration of an optical pickup device 40 using the optical integrated unit of the present embodiment.
- the optical pickup device 40 shown in FIG. 2 includes an optical integrated unit 1, a collimator lens 2, and an object lens 3.
- the light beam emitted from the light source mounted on the optical integrated unit 1 is collimated by the collimator lens 2 and then condensed on the optical disc 4 through the objective lens 3. Then, the light reflected from the optical disk 4 (hereinafter referred to as “returned light”) passes through the objective lens 3 and the collimator lens 2 again and is received by the light receiving element mounted on the optical integrated unit 1.
- returned light the light reflected from the optical disk 4
- the optical disc 4 includes a substrate 4a, a cover layer 4b through which a light beam is transmitted, and a recording layer 4c formed at the boundary between the substrate 4a and the cover layer 4b.
- the objective lens 3 is driven in the focus direction (z-axis direction) and tracking direction (X-axis direction) by an objective lens drive mechanism (not shown). Even in such a case, the focused spot follows the predetermined position of the recording layer 4c.
- the optical integrated unit 1 is provided with a short wavelength light source having a wavelength of about 405 nm, and the object lens 3 is provided with a high NA objective lens of about NAO.
- the present invention is not limited to this, but by providing such a short wavelength light source and a high NA objective lens, high-density recording / reproduction becomes possible.
- FIG. 1 (a) and FIG. 1 (b) are configuration diagrams showing the configuration of the optical integrated unit 1 shown in FIG. FIG. 1 (a) is a side view of the y-axis direction force with respect to the illustrated optical axis (z-axis) direction.
- the optical integrated unit 1 includes a semiconductor laser (light source) 11, a light receiving element 12, a polarization beam splitter 14 (light guide means), and a polarization diffraction element (diffraction). Means) 15, 1 Z4 wave plate 16, and package 17.
- the package 17 includes a stem 17a, a base 17b, and a cap 17c. Yes.
- the cap 17c is formed with a window portion 17d for allowing light to pass therethrough.
- a semiconductor laser 11 and a light receiving element 12 are mounted in the package 17.
- FIG. 1 (b) shows the arrangement of the package 17 in the optical axis (z-axis) direction shown in FIG. 1 (a) in order to show the positional relationship between the semiconductor laser 11 and the light receiving element 12 in the laser / cage 17.
- FIG. 6 is a top view as seen from the side (that is, from the window 17d side of the cap 17c).
- the polarization beam splitter 14, the polarization diffraction element 15, and the 1 Z4 wavelength plate 16 are omitted.
- the light receiving element 12 is mounted on the stem 17a, and the semiconductor laser 11 is provided on the side of the stem 17a.
- the light beam emitting part of the semiconductor laser 11 and the light receiving part of the light receiving element 12 are caps so that the optical path of the light beam emitted from the semiconductor laser 11 and the optical path of the return light received by the light receiving element 12 are secured. Arranged so as to be included in the region of the window 17d formed in 17c.
- the surface of the polarization beam splitter 14 on which the light beam 20 emitted from the semiconductor laser 11 is incident is the light beam incident surface of the polarization beam splitter 14, and the polarization beam splitter 14
- the surface on which the return light is incident is the return light incident surface of the polarization beam splitter 14.
- the surface on which the optical beam 20 emitted from the semiconductor laser 11 in the polarization diffraction element 15 is incident is the light beam incident surface of the polarization diffraction element 15, and the surface on which the return light is incident on the polarization diffraction element 15 is polarization diffraction. This is the return light incident surface of element 15.
- the polarizing beam splitter 14 is disposed on a knock 17. Specifically, the light beam incident surface force of the polarizing beam splitter 14 is disposed on the package 17 so as to cover the window portion 17d.
- the polarization diffraction element 15 is disposed on the optical axis of the light beam emitted from the semiconductor laser 11 so that the light beam incident surface faces the return light incident surface of the polarization beam splitter 14. Has been.
- P-polarized light linearly polarized light
- the polarization beam splitter 14 has a polarization beam splitter (PBS) surface (functional surface) 14a and a reflection mirror (reflection surface) 14b.
- PBS polarization beam splitter
- the PBS surface 14a in the present embodiment transmits linearly polarized light (P-polarized light) having a polarization vibration surface in the x-axis direction with respect to the illustrated optical axis (z-axis) direction, and passes through the polarization vibration surface. It has a characteristic of reflecting linearly polarized light (S-polarized light) having a vertical polarization vibration surface, that is, having a polarization vibration surface in the y-axis direction with respect to the illustrated optical axis (z-axis) direction.
- S-polarized light linearly polarized light having a vertical polarization vibration surface
- the present invention is not limited to this, and the above characteristics can be changed. Specifically, as described in Embodiment 3 described later, it is possible to reflect part of the P-polarized light.
- the PBS surface 14a is disposed on the optical axis of the P-polarized light beam emitted from the semiconductor laser 11 so that the light beam 20 is transmitted.
- the reflection mirror 14b is arranged so as to be parallel to the PBS surface 14a!
- the size of the polarizing beam splitter 14 is such that the light beam 20 emitted from the semiconductor laser 11 can pass through the PBS surface 14a, and the return light reflected by the optical information recording medium is reflected by the PBS surface 14a. The reflected light is further reflected by the reflecting mirror 14b and received by the light receiving element 12.
- the cap 17c of the package 17 is not particularly limited. It is preferable that the dimensions are sufficiently large with respect to the area of the formed window portion 17d. If the size of the polarizing beam splitter 14 is sufficiently large with respect to the area of the window portion of the cap 17c, the polarizing beam splitter 14 can be bonded and fixed onto the cap 17c. As a result, the semiconductor / cage 17 can be sealed, the semiconductor laser 11 and the light receiving element 12 are not exposed to the outside air, and these characteristic deteriorations are less likely to occur.
- the light beam 20 (P-polarized light) incident on the PBS surface 14a passes through the PBS surface 14a as it is.
- the light beam 20 transmitted through the PBS surface 14 a is incident on the polarization diffraction element 15.
- the optical integrated unit according to the present invention is not limited to the polarizing beam splitter 14 and can transmit the light beam 20 emitted from the semiconductor laser 11 as described above. Any configuration that can guide the return light reflected by the optical information recording medium in a direction different from that of the semiconductor laser 11, change the optical path of the return light, and cause the light receiving element 12 to receive the return light. Good. Therefore, in addition to the polarizing beam splitter, a beam splitter having the functional surface 14a as a mirror mirror surface can also be used.
- the polarization diffraction element 15 includes first polarization hologram element 31 (second hologram area) and second polarization hologram element 32 (first hologram area). ! RU
- Both the first polarization hologram element 31 and the second polarization hologram element 32 are arranged on the optical axis of the light beam 20, and the first polarization hologram element 31 is the second polarization hologram element described above.
- the polarization hologram element 32 is arranged closer to the semiconductor laser 11 side.
- the first polarization hologram element 31 diffracts P-polarized light and transmits S-polarized light
- the second polarization hologram element 32 diffracts S-polarized light and transmits P-polarized light.
- the diffraction of these polarized light is performed by the groove structure (grating) formed in each polarization hologram element, and the diffraction angle is defined by the pitch of the grating (hereinafter referred to as the grating pitch).
- the first polarization hologram element 31 has a three-beam generating hologram pattern for detecting a tracking error signal (TES).
- TES tracking error signal
- TES tracking error signal
- 3 beams (a main beam and two sub beams) are emitted from the first polarization hologram element 31.
- the detailed hologram pattern of the first polarization hologram element 31 will be described later.
- a TES detection method using three beams a three beam method, a differential push-pull (DPP) method, a phase shift DPP method, or the like can be used.
- the second polarization hologram element 32 diffracts S-polarized light and transmits P-polarized light as it is in the incident light. Specifically, the second polarization hologram element 32 diffracts the incident S-polarized light into zero-order diffracted light (non-diffracted light) and + first-order diffracted light (diffracted light). However, the present invention is not limited to this diffraction condition and can be set as appropriate. . Specifically, in Embodiment 5 to be described later, the second polarization hologram element 32 that diffracts incident S-polarized light into zero-order diffracted light (non-diffracted light) and first-order diffracted light (diffracted light) is provided. I have.
- the P-polarized light beam 20 emitted from the first polarization hologram element 31 is incident on the second polarization hologram element 32 and is transmitted as it is.
- the P-polarized light beam 20 that has passed through the second polarization hologram element 32 enters the 1Z4 wavelength plate 16.
- the detailed hologram pattern of the second polarization hologram element 32 will be described later.
- the 1Z4 wave plate 16 can receive linearly polarized light, convert it into circularly polarized light, and emit it. Therefore, the P-polarized light beam 20 (linearly polarized light) incident on the 1Z4 wavelength plate 16 is converted into a circularly polarized light beam and emitted from the optical integrated unit 1.
- the circularly polarized light beam emitted from the optical integrated unit 1 is collimated by the collimator lens 2 and then condensed on the optical disc 4 through the objective lens 3. Then, the light beam reflected by the optical disk 4, that is, the return light again passes through the objective lens 3 and the collimator lens 2 and again enters the quarter-wave plate 16 of the optical integrated unit 1. .
- the return light incident on the 1Z4 wavelength plate 16 of the optical integrated unit 1 is circularly polarized light, and the 1Z4 wavelength plate 16 causes the polarization vibration plane in the y-axis direction to the optical axis (z-axis) direction shown in the figure. It is converted to linearly polarized light (S-polarized light). Then, the S-polarized return light is incident on the second polarization hologram element 32.
- the S-polarized return light incident on the second polarization hologram element 32 is diffracted into 0th-order diffracted light (non-diffracted light) and + 1st-order diffracted light (diffracted light) as described above. To do.
- the diffracted S-polarized return light (0th-order diffracted light and + first-order diffracted light) is incident on the first polarization hologram element 31 and is transmitted as it is.
- the S-polarized return light is incident on the polarization beam splitter 14, reflected by the PBS surface 14 a, further reflected by the reflection mirror 14 b, and emitted from the polarization beam splitter 14.
- the S-polarized return light emitted from the polarization beam splitter 14 is received by the light receiving element 12.
- the light receiving part pattern of the light receiving element 12 will be described later.
- a short wavelength light source having a wavelength of about 405 nm is provided, and the objective lens 3 is provided with NAO. It has a high NA objective lens of about 85, and the distance from the semiconductor laser 11 to the polarization diffraction element 15 (specifically, the first polarization hologram element 31) is about 5 mm in terms of the optical path length in air. It is said.
- the distance (optical path length) from the polarization diffraction element 15 (specifically, the second polarization hologram element 32) to the light receiving element 12 is set to about 5 mm.
- the present invention is not limited to this value.
- a short wavelength light source having a wavelength of about 405 nm is provided and the objective lens 3 is provided with a high NA objective lens of NAO.
- the distance to the polarization diffraction element 15 (specifically, the first polarization hologram element 31) can increase the effective diameter of the light beam on the first polarization hologram element 31.
- the distance (optical path length) from the polarization diffraction element 15 (specifically, the second polarization hologram element 32) to the light receiving element 12 must be designed near the focal point of the non-diffracted light. The distance is approximately the same as the distance from 11 to the polarization diffraction element 15 (specifically, the first polarization hologram element 31).
- the grating pitch in the first polarization hologram element 31 is designed so that three beams are sufficiently separated on the light receiving element 12.
- the distance between the semiconductor laser 11 and the first polarization hologram element 31 is about 5 mm in terms of the optical path length in the air, and the distance between the main beam and the sub beam on the light receiving element 12 is 150 m. It is trying to be about.
- the distance between the main beam and the sub beam on the optical disc 4 is set to about 16 m.
- the grating pitch in this embodiment is used. Is preferably about 14 ⁇ m.
- the present invention is not limited to this value, and the distance between the main beam and the sub beam on the light receiving element 12 should be as wide as possible to reduce the signal crosstalk between the light receiving parts.
- the distance between the main beam and the sub beam on the light receiving element 12 should be as wide as possible to reduce the signal crosstalk between the light receiving parts.
- it is designed to be the minimum necessary 100 to 200 / ⁇ m, preferably about 150 m.
- the smaller the distance between the main beam and the sub beam on the optical disc 4 the smaller the offset of the tracking error signal generated due to the influence of the assembly error. When the interval is determined, it is determined at the same time.
- the distance between the main beam and the sub beam on the light receiving element 12 is 100 to 100 Assuming 200 ⁇ m, the distance between the main beam and the sub beam on the optical disc 4 is 11 to 22 ⁇ m, and the grating pitch in this case is designed to be 20 to 10 / ⁇ ⁇ . Therefore, if the distance between the main beam and the sub beam on the optical disk 4 cannot be sufficiently narrowed, the offset of the tracking error signal generated by the influence of the assembly error is small compared to the three beam method or the DPP method. It is preferable to adopt the phase shift DPP method with the characteristic as a tracking error signal detection method.
- FIG. 3 is a schematic diagram showing a hologram pattern formed on the first polarization hologram element 31.
- the hologram pattern may be a regular linear grating for detecting a tracking error signal (TES) using a three-beam method or a differential push-pull method (DPP method). The case where the phase shift DPP method disclosed in the 2001-250250 publication (published on Sep. 14, 2001) is described.
- the hologram pattern of the first polarization hologram element 31 in FIG. 3 is composed of two regions, a region 31a and a region 31b.
- the region 31a and the region 31b have a phase difference of 180 degrees between the periodic structures.
- the amplitude of the push-pull signal of the sub-beam becomes almost zero, and offset can be canceled with respect to objective lens shift and disc tilt.
- the light beam 20 on the first polarization hologram element 31 is more accurately aligned with respect to the region 31a and the region 31b, better offset canceling performance is obtained.
- the effective diameter of the light beam 20 is larger, the positional deviation between the light beam 20 and the region 3 la and the positional deviation between the light beam 20 and the region 3 lb due to changes with time and temperature are affected. Can be reduced. That is, the influence on the servo signal detected later can be reduced.
- the optical system in which the effective NA of the collimator lens 2 in Fig. 2 is about 0.1.
- the distance from the semiconductor laser 11 to the first polarization hologram element 31 is about 5 mm in terms of the optical path length in air, and the effective diameter of the light beam 20 on the first polarization hologram element 31 is about 1 mm.
- the effective diameter can be increased 2.5 to 5 times for 4mm.
- the effective diameter of the light beam 20 on the first polarization hologram element 31 is ⁇ ⁇ . 6 to 1.4 mm.
- FIG. 4 is a schematic diagram showing a hologram pattern formed on the second polarization hologram element 32.
- the hologram pattern of the second polarization hologram element 32 includes three regions 32a, 32b, and 32c. Specifically, one semicircular region 32c divided into two by a boundary line 32x in the X-axis direction corresponding to the tracking direction, and an inner peripheral region 32a in which the other semicircular region is further divided by an arc-shaped boundary line And the outer peripheral region 32b.
- the return light is indicated by a dotted line.
- the grating pitch in each region of the second polarization hologram element 32 is the smallest in the region 32b (maximum diffraction angle), the largest in the region 32c (minimum diffraction angle), and the region 32a in these regions It becomes an intermediate number.
- SAES spherical aberration error signal
- FES focus error signal
- the 0th-order diffracted light is used to detect a high-speed signal such as an RF signal or a DPD TES signal.
- the interval between the 0th-order diffracted light and the + 1st-order diffracted light on the light receiving element 12 is set to 0.5 to 1.2 mm, more preferably 0.7 mn! It needs to be about 0.9mm.
- the distance from the light element 32 to the light receiving element 12 is about 5 mm in terms of the optical path length in the air, it is preferable to set the diffraction angle in the second hologram element 32 to 5 to: LOdeg 7 to More preferably, it is about 9 deg.
- the distance from the second hologram element 32 to the light receiving element 12 is about 5 mm in terms of the optical path length in air, separation of the 0th-order diffracted light and the + first-order diffracted light on the light receiving element 12 is performed.
- the diffraction angle is about 8 deg.
- the pitch of the grating formed in the second hologram element 32 is 2.8 nm, which is the wavelength of the light beam in this embodiment, which is 2.8 nm. m. In other words, this lattice pitch can be increased by a factor of 4 compared to 0.7 m for the prior art. Therefore, the shape has no problem in manufacturing as described above.
- the diffraction angle strength (approximately 1Z4 the diffraction angle 35deg prior art) is ⁇ so, even when the error factor such as the wavelength variation and position deviation occurs, the on the light receiving element 12 Small variation in condensing position! / ⁇ and ⁇ ⁇ effect.
- the first polarization hologram element 31 and the second polarization hologram element 32 can be integrally manufactured with accurate positioning with mask accuracy. Therefore, the position adjustment of the first polarization hologram element 32 is completed simultaneously with the position adjustment of the second polarization hologram element 32 so that a predetermined servo signal is obtained. That is, the assembly adjustment of the optical integrated unit 1 can be facilitated and the adjustment accuracy can be increased.
- FIG. 5 (a) shows the position of the collimator lens 2 in the optical axis direction so that spherical aberration does not occur in the focused beam by the objective lens 3 with respect to the thickness of the cover layer 4b of the optical disk 4 in FIG.
- the light beam on the light receiving element 12 when focused on the recording layer 4c in a state where the position adjustment is made is shown.
- the relationship between the three regions 32a to 32c of the second polarization hologram element 32 described in FIG. 4 and the traveling direction of the + first-order diffracted light is also shown.
- the center position of the second polarization hologram element 32 is set at a position corresponding to the center position of the light receiving portions 12a to 12d.
- the light receiving element 12 is composed of 14 light receiving portions 12a to 12n.
- Three light beams (main beam, two sub-beams) 21 formed by the first polarization hologram element 31 in the outward optical system are reflected by the optical disc 4 and are not diffracted by the second polarization hologram element 32 in the return optical system.
- the light receiving element 12 includes a light receiving unit for receiving a light beam necessary for detecting an RF signal or a servo signal out of the non-diffracted light 22 and the diffracted light 23.
- the non-diffracted light (0th order diffracted light) 22 is designed to be a light beam having a certain size so that TES detection by the push-pull method can be performed.
- the light receiving element 12 is slightly behind the condensing point of the non-diffracted light 22 so that the beam diameter of the non-diffracted light (0th order diffracted light) 22 has a certain size. Installed in a shifted position. The present invention is not limited to this, and the light receiving element 12 may be installed at a position shifted to the near side with respect to the condensing point of the non-diffracted light 22.
- FIG. 5 (b) shows a light beam on the light receiving element 12 when the objective lens 3 in FIG. 2 approaches the optical disc 4 from the state of FIG. 5 (a).
- the beam diameter of the light beam increases.
- the light beam protrudes from the light receiving part.
- the servo signal generation operation will be described with reference to FIG. 4, FIG. 5 (a), and FIG. 5 (b).
- the output signals of the light receiving portions 12a to 12n are represented as Sa to Sn.
- the RF signal (RF) is detected using non-diffracted light. That is, the RF signal (RF) is
- the tracking error signal (TES1) by the DPD method is detected by comparing the phases of Sa to Sd. Specifically, the following principle is used. Shaped on recording layer 4c of optical disc 4 When the light beam condensed by the objective lens 3 scans the formed pit row, the intensity distribution pattern of the reflected beam changes depending on the positional relationship between the pit row and the light beam. Therefore, when (Sa + Sc) and (Sb + Sd) are detected, the light beam is out of phase with the center of the pit row, whereas the light beam is in the same phase when scanning the center of the pit row. When scanning a different position, a phase difference in the opposite direction occurs depending on the direction of deviation. Therefore, a tracking error signal can be obtained by detecting the phase difference between (Sa + Sc) and (Sb + Sd).
- Phase shift DPP tracking error signal (TES2)
- ⁇ is set to an optimum coefficient for canceling offset due to objective lens shift or optical disc tilt.
- FES focus error signal
- the optical pickup device includes a short wavelength light source having a wavelength of about 405 nm in the optical integrated unit 1 and a high NA objective lens having a NAO. High-density recording / playback is possible.
- a DVD Digital Versatile Disc
- CD Compact Disc
- BD Blu-ray Disc
- NA numerical aperture
- laser light with a wavelength of 405 nm the influence of aberration becomes a problem as the numerical aperture NA of the objective lens increases.
- the distance between the incident surface of the laser beam and the recording layer is a distance through which the laser beam irradiated onto the recording layer on which information is recorded is transmitted.
- Spherical convergence caused by error in cover layer thickness t (hereinafter referred to as disk substrate thickness t)
- NA numerical aperture
- the CD disk substrate thickness t has a dimensional tolerance of ⁇ 10 O ⁇ m, the laser beam wavelength is 650 nm, and the numerical aperture NA is 0.6.
- the DVD disk substrate thickness t has a dimensional tolerance of ⁇ 30 m, as in the case of the present embodiment, while the laser beam has a wavelength of 05 nm and a numerical aperture NA of 0.85.
- the dimensional tolerance of the disk substrate thickness t of the density optical disk is ⁇ 3 / zm. In this way, as the capacity is increased, the disc manufacturing accuracy becomes increasingly severe.
- the optical pickup device is required to have a function of correcting spherical aberration that occurs when reproducing an optical disk.
- spherical aberration correction is performed by mechanically moving a lens such as a beam expander.
- a lens such as a beam expander.
- it is necessary to detect a spherical aberration error signal which is a target for spherical aberration correction.
- the position of the collimator lens 2 is adjusted in the optical axis direction by a collimator lens driving mechanism (not shown) in order to correct the spherical aberration caused by the thickness error of the cover layer 4b.
- a beam expander (not shown) composed of two lens groups arranged between the collimator lens 2 and the objective lens 3 is adjusted to adjust the distance of the beam expander driving mechanism (not shown). It has become.
- the spherical aberration error signal (SAES) is detected using the detection signal of the optical beamer separated into the inner and outer circumferences. That is, SAES
- SAES (Sk-Sl)- ⁇ (Si-Sj) Given in.
- ⁇ is set to an optimum coefficient for canceling the SAES offset.
- FIGS. 6 (a) and 6 (b) show that the optical disc 4 is objective in a state where spherical aberration occurs in the focused beam of the objective lens 3 due to the thickness error of the cover layer 4b of the optical disc 4.
- FIG. 4 is a diagram for explaining the shape of a light beam on the light receiving element 12 when it is located at the focal point of a lens 3. Since spherical aberration remains, the inner and outer beams are larger in the opposite direction to the parting line. This is because the generation direction of spherical aberration (sign of thickness error) differs between Fig. 6 (a) and Fig. 6 (b).
- the light beam transmitted through the polarization beam splitter 14 is incident on the polarization diffraction element 15, and the polarization diffraction is incident on the light receiving element 12.
- the return light diffracted by the element 15 and passed through the polarization beam splitter 14 is received.
- the light beam 20 emitted from the light source passes through the polarization beam splitter 14 and then enters the polarization diffraction element 15 (first hologram element 31). Therefore, the optical path length of the light beam 20 from the light source until it enters the first hologram element 31 can be increased.
- the optical path length can be increased, the beam diameter of the light beam 20 incident on the first hologram element 31 is changed between the semiconductor laser 11 and the first hologram element 31. This can be increased compared to the case where the beam splitter 14 is not arranged.
- the light receiving element 12 receives the return light diffracted by the polarization diffraction element 15 (second hologram element 32) and passed through the polarization beam splitter 14. That is, the light passes through the polarizing beam splitter 14 after passing through the second hologram element 32 and before entering the light receiving element 12. Therefore, the optical path length of the diffracted return light until it is received by the light receiving element 12 can be increased. Accordingly, even when the diffraction angle of the polarization diffraction element 15 (the first hologram element 31 and the second hologram element 32) is set to be small, the light diffracted on the light receiving element 12 is set. (Return light) can be separated well.
- the polarization diffraction element 15 includes a first hologram element 31 and a second hologram element 32, each of which has a predetermined polarization vibration surface.
- the first hologram element 31 and the second hologram element 32 are provided respectively for the polarization diffraction element that transmits the polarized light having the polarization vibration plane perpendicular to the polarization vibration plane.
- the predetermined polarization vibration planes are arranged on the optical axis of the light beam 20 so as to be perpendicular to each other.
- the polarized light diffracted in the first hologram area is transmitted through the second hologram area as it is, and conversely, the polarized light diffracted in the second hologram area is
- the hologram area is transmitted as it is. That is, by providing the polarization diffraction element 15, the light beam and the return light can be diffracted.
- the second hologram element 32 diffracts the return light into non-diffracted light and diffracted light.
- the optical integrated unit 1 can receive the light reception even when the return light is diffracted into non-diffracted light and diffracted light. These can be sufficiently separated on the element 12.
- the diffracted light and the non-diffracted light cannot be sufficiently separated in the vicinity of the second hologram element 32, the distance between the diffracted light and the non-diffracted light while passing through a long optical path.
- the diffracted light and the non-diffracted light can be satisfactorily separated on the light receiving element 12.
- the first hologram element 31 divides the optical beam into three beams.
- the light receiving element 12 includes a light receiving unit that receives the diffracted light and a light receiving unit that receives the non-diffracted light.
- the optical integrated unit 1 has the diffracted return light (diffracted light and non-diffracted light).
- the optical path length of the light) can be increased, so that even if the diffracted light and non-diffracted light cannot be sufficiently separated in the vicinity of the second hologram element 32, the diffracted light and It becomes possible to separate non-diffracted light well.
- the light receiving element 12 includes a light receiving section that receives the non-diffracted light, the non-diffracted light can be used for detection of a high-speed signal.
- the non-diffracted light can be used to detect a high-speed signal such as an RF signal or a TES signal by the DPD method.
- the diffracted light can be used for servo signal detection.
- the grating pitch of the first hologram element 31 and the second hologram element 32 can be formed large. Thereby, the polarization diffraction element 15 (the first hologram element 31 and the second hologram element 32) can be easily manufactured.
- the polarizing beam splitter 14 further includes a reflecting mirror 14b, so that the diffracted return light can be reflected in a desired direction, and Accordingly, the optical path length can be further increased.
- the semiconductor laser 11 is housed in the hermetically sealed package 17, so that the semiconductor laser 11 is not exposed to the outside air, resulting in deterioration of characteristics. It becomes difficult to occur.
- the semiconductor laser 11 can be used as the light receiving element. 12 and the polarization beam splitter 14 can be adjusted so that the semiconductor laser 11 and the light receiving element 12 are accurately positioned, so that the semiconductor laser 11 housed in the knocker 17 is used. Even in this case, the return light can be reliably incident on the light receiving element 12. Therefore, it is possible to minimize the area of the light receiving portion that receives non-diffracted light, and high-speed signal detection can be performed satisfactorily.
- the 1Z4 wavelength plate 16 is provided on the side of the polarization diffraction element 15 opposite to the side on which the polarization beam splitter 14 is disposed. While the light beam emitted from 11 is linearly polarized light, the linearly polarized light is irradiated on the optical disc 4 as circularly polarized light by being transmitted through the 1Z4 wavelength plate 16. Therefore, it is not easily affected by the birefringence of the substrate 4a when generating an RF signal.
- the return light reflected on the optical disc 4 is linearly polarized light whose polarization oscillation plane is orthogonal to the linearly polarized light, it enters the polarization diffraction element 15 and is diffracted and reflected by the PBS surface 14a.
- the return light utilization efficiency can be increased. Further, unnecessary interference between the light beam and the return light can be suppressed.
- optical pickup device 40 in the present embodiment can be mounted with the optical integrated unit 1 having the above-described configuration, it is possible to realize a small and light weight.
- the force described in the configuration in which three beams are generated by the first hologram element 31 is not limited to this.
- the present invention is not limited to this.
- Three beams are used for TES generation. It can also be applied to an integrated optical unit for one beam.
- the optical pickup device includes an optical integrated unit 1 ′ from which the 1Z4 wavelength plate 16 has been removed and is combined with an external quarter-wave plate 5. It is also possible.
- the force of the present invention is a configuration in which the polarization diffraction element 15 that diffracts the light beam and the return light is disposed on the side opposite to the semiconductor laser 11 in the polarization beam splitter 14. It is not limited to this.
- the diffractive element 33 for generating the three beams for detecting the tracking error signal is provided in the polarization beam splitter 14 as shown in FIG.
- the semiconductor laser 11 may be arranged on the side of the semiconductor laser 11.
- Rotation adjustment is required to match the track direction of the optical disc 4 and the arrangement direction of the three beams. This can be done by adjusting the rotation of the entire optical integrated unit 1 about the optical axis. Therefore, the diffraction element 33 can be fixed to the package 17 without adjustment.
- the diffractive element 33 does not pass the return light and passes only the light beam 20, so it is not necessary to have a polarization characteristic. Therefore, a normal hologram element having no polarization characteristic can be used for the diffraction element 33. Further, as shown in FIG. 7, since the package 17 can be sealed using the diffraction element 33, it is possible to suppress the deterioration of the characteristics of the semiconductor laser 11 and the light receiving element 12! .
- the present invention can also be expressed as having the following features. That is, in the optical integrated unit according to the present invention, the light source, the light guiding means for guiding the return light from the optical information recording medium in a different direction from the light source, the polarization diffraction element, and the light receiving element are integrated.
- the optical integrated unit is characterized in that the polarization diffraction element is disposed on a side of the light guide means facing the light source and the light receiving element.
- the light guiding means may be a polarizing beam splitter including at least two reflecting surfaces parallel to each other.
- FIGS. 8 (a) and 8 (b) Another embodiment of the present invention will be described below with reference to FIGS. 8 (a) and 8 (b). In the present embodiment, differences from the first embodiment will be described. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals. The description is omitted.
- FIGs. 8 (a) and 8 (b) are configuration diagrams showing the configuration of the optical integrated unit according to the second embodiment of the present invention.
- FIG. 8 (a) is a side view seen from the y-axis direction with respect to the illustrated optical axis (z-axis) direction
- FIG. 8 (b) shows the semiconductor laser 11 and the light receiving element 12 in the package 17.
- FIG. 9 is a top view of the package 17 as seen from the optical axis (z-axis) direction shown in FIG. 8A (that is, from the window 17d side of the cap 17c) in order to show the arrangement relationship.
- the optical integrated unit in the present embodiment is the same as the optical integrated unit in the first embodiment.
- the mounting direction of the semiconductor laser 11 is different.
- the 1Z2 wavelength plate 13 is provided in the optical integrated unit of the present embodiment.
- the semiconductor laser 11 shown in FIG. 2 is linearly polarized light (P-polarized light) having a polarization oscillation plane in the X-axis direction with respect to the illustrated optical axis (z-axis) direction.
- linearly polarized light (S-polarized) light beam 21 having a polarization oscillation plane in the y-axis direction with respect to the illustrated optical axis (z-axis) direction is emitted into package 17. It is installed.
- the semiconductor laser 11 in the present embodiment is an S-polarized light beam 21 having a polarization oscillation plane in the y-axis direction with respect to the illustrated optical axis (z-axis) direction.
- the polarization beam splitter 14 in the first embodiment As it is, all of the light is reflected by the PBS surface 14a and the directional light beam is lost on the optical disk 4.
- the 1Z2 wavelength plate 13 is disposed in the optical path between the semiconductor laser 11 and the polarization beam splitter 14.
- the polarization oscillation plane of the light beam 21 is converted into linearly polarized light (P-polarized light) in the X-axis direction with respect to the optical axis (z-axis) direction shown in the figure, All of the polarized PBS surface 14a of the polarization beam splitter 14 can be transmitted.
- the semiconductor laser 11 emits a light beam other than the P-polarized light beam, that is, an S-polarized light beam, it uses light. It can be applied without reducing the efficiency.
- this has the effect of increasing the degree of freedom of component layout of the semiconductor laser 11 and the intensity distribution correction element (not shown). Furthermore, there is an effect that the degree of freedom in designing the RIM intensity of the light beam incident on the objective lens 3 is increased.
- FIGS. 9 (a) and 9 (b) Another embodiment of the present invention will be described below with reference to FIGS. 9 (a) and 9 (b). In the present embodiment, differences from the first embodiment will be described. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals. The description is omitted.
- FIG. 9 (a) and Fig. 9 (b) show the configuration of the optical integrated unit of the third embodiment of the present invention.
- FIG. 9 (a) is a side view seen from the y-axis direction with respect to the illustrated optical axis (z-axis) direction
- FIG. 9 (b) shows the semiconductor laser 11 and the light receiving element 12 in the package 17.
- FIG. 10 is a top view of the package 17 as viewed from the optical axis (z-axis) direction shown in FIG. 9A (that is, from the window 17d side of the cap 17c) in order to show the positional relationship.
- the optical integrated unit in the present embodiment has a configuration in which a reflecting surface 14c is added to the polarization beam splitter 14 in the optical integrated unit in the first embodiment, and an APC is included in the nockage 17.
- a light receiving element (APC light receiving element) 18 for (control of the amount of light emitted from the objective lens) is added.
- the emitted light 20 from the semiconductor laser 11 passes through the PBS surface 14a of the polarization beam splitter 14 and is emitted from the optical integrated unit 1, and has only an optical path toward the objective lens 3.
- the emitted light 20 from the semiconductor laser 11 passes through the PBS surface 14a of the polarization beam splitter 14 and is emitted from the optical integrated unit 1, and is applied to the objective lens 3 in the direction of the optical path in addition to the PBS. After the light is reflected by the surface 14a, the light path is reflected by the reflecting surface 14c and incident on the APC light receiving element 18.
- the amount of light emitted from the objective lens 3 and the amount of light incident on the APC light-receiving element 18 change in proportion to the amount of light emitted from the semiconductor laser 11, using the light amount detected by the APC light-receiving element 18, The amount of light emitted from the objective lens 3 can be accurately controlled.
- the configuration different from the configuration of the first embodiment is provided in the following points. That is, in the present embodiment, (l) a force that slightly modifies the characteristics of the PBS surface 14a to reflect a part of the P-polarized light, and (2) a force that rotates the mounting direction of the semiconductor laser 11 around the optical axis, A 1Z2 wave plate (not shown) is added between the semiconductor laser 11 and the polarization beam splitter 14 so that an optical beam having an S-polarized component is incident on the PBS surface 14a.
- the APC light receiving element 18 can be integrated in the optical integrated unit 1. Therefore, the optical pickup device can be further miniaturized.
- FIG. Street Another embodiment according to the present invention will be described with reference to FIG. Street.
- members having the same functions as those described in the first embodiment are denoted by the same reference numerals, The description is omitted.
- FIG. 10 shows a configuration of the optical integrated unit 1 according to the fourth embodiment of the present invention.
- the configurations of the semiconductor laser 11 and the light receiving element 12 are different.
- the semiconductor laser 11 and the light receiving element 12 are arranged in the knock 17 as they are.
- the semiconductor laser 11 and the light receiving element 12 are housed in independent packages 18 and 19, respectively.
- the semiconductor laser 11 and the light receiving element 12 in this embodiment are housed in independent packages 18 and 19, respectively, as shown in FIG. In the state of being housed in the same package 17, it is further integrated in the same package 17 as in the first embodiment.
- the knock 17 does not need to be sealed, and the size of the polarizing beam splitter 14 does not have to cover the window 17d completely. There is an effect that the unit can be made small and light and low cost.
- FIGS. 11 (a) and 11 (b) Another embodiment of the present invention will be described below with reference to FIGS. 11 (a) and 11 (b).
- a member having the same function as the member described in Embodiment 1 is described in order to explain differences from Embodiment 1 above. Are given the same numbers, and the description thereof is omitted.
- the incident S-polarized light is diffracted into 0th-order folded light (non-diffracted light) and + first-order diffracted light (diffracted light).
- the second polarization hologram element 32 is provided that refracts incident S-polarized light into zero-order diffracted light (non-diffracted light) and ⁇ first-order diffracted light (diffracted light). Yes.
- the light receiving element 12 of the first embodiment is configured with a light receiving portion pattern that receives 0th-order diffracted light (non-diffracted light) and + first-order diffracted light (diffracted light).
- the second polarization hologram element 32 diffracts the incident S-polarized light into 0th order diffracted light (non-diffracted light) and ⁇ 1st order diffracted light (diffracted light)
- the light receiving element 12 receives 0th order diffracted light ( Non-diffracted light), first-order diffracted light (diffracted light), and + first-order diffracted light (diffracted light) are received.
- FIGS. 11A and 11B illustrate the relationship between the division pattern of the second polarization hologram element 32 provided in the optical integrated unit of the present embodiment and the light receiving portion pattern of the light receiving element 12.
- FIG. 11 (a) shows the alignment of the collimator lens 2 in the optical axis direction so that spherical aberration does not occur in the focused beam from the objective lens 3 with respect to the thickness of the cover layer 4b of the optical disk 4 in FIG. Shown is the light beam on the light receiving element 12 when focused on the recording layer 4c in the focused state.
- the light receiving element 12 is composed of 14 light receiving portions 12a to 12n.
- the three light beams 21 formed by the first polarization hologram element 31 are reflected by the optical disk 4 and are then diffracted by the second polarization hologram element 32 in the return optical system (0th order diffracted light). ) Separated into 22 and diffracted light ( ⁇ first order diffracted light) 23.
- the light receiving element 12 includes a light receiving unit for receiving a light beam necessary for detection of an RF signal and a servo signal among non-diffracted light (0th order diffracted light) 22 and diffracted light ( ⁇ 1st order diffracted light). It has been. Specifically, the 12 non-diffracted lights (0th order diffracted light) 40 of the second polarization hologram element 32, 6 + 1st order diffracted lights 41 and 3 1st order diffracted lights 42 are formed in total 12 beams. It is done.
- the hologram pattern is blazed.
- the cross-sectional shape of the grating is formed into a slope shape or a staircase shape so that the light intensity of the specific order of diffracted light is increased.
- the region 32a and the region 32b have a cross-sectional shape in which the light intensity is concentrated on the + first-order diffracted light, and the region 32c has a light-intensity concentrated on the first-order diffracted light. Therefore, unnecessary diffraction By suppressing the light intensity and increasing the light intensity of the diffracted light used for signal detection, the signal quality of the detection signal can be improved.
- the second polarization hologram element 32 also generates non-diffracted light, unnecessary diffracted light cannot be completely removed. Therefore, the shapes of the light receiving portions 12i to 12n of the light receiving element 12 are designed so that a sufficient interval in the X-axis direction can be secured so that unnecessary diffracted light (not shown) does not enter.
- FIG. 11B shows a light beam on the light receiving element 12 when the objective lens 3 in FIG. 2 approaches the optical disc 4 from the state of FIG. 11A.
- the beam diameter of the light beam increases. The light beam protrudes from the light-receiving unit while the force is applied.
- the offset adjustment of the FES signal of the double knife edge method is reliably performed by adjusting the rotation of the center of the optical axis of the polarization diffractive element 15. If you can do it, there is a positive effect.
- the optical integrated unit according to the present invention can reduce the influence of changes with time and temperature by increasing the light beam diameter on the diffractive element as much as possible, and can reduce the optical path length to the diffractive element and the light receiving element.
- Increasing the diffraction angle reduces the grating angle (increasing the grating pitch) to facilitate manufacture of the diffractive element, and detects the RF signal using the non-diffracted light from the diffractive element, resulting in high-speed response (the optical disk is rotated at high speed). High-speed playback) can be realized.
- the present invention is suitable for an optical integrated unit for realizing miniaturization of an optical pickup used for recording or reproducing information on an optical recording medium such as an optical disc, and an optical pickup apparatus equipped with the same. Can be used.
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Abstract
Description
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US11/660,824 US7697396B2 (en) | 2004-08-25 | 2005-06-17 | Optical integrated unit and optical pickup device including same |
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JP2004-245925 | 2004-08-25 | ||
JP2004245925A JP3836483B2 (ja) | 2004-08-25 | 2004-08-25 | 光集積ユニットおよびそれを備えた光ピックアップ装置 |
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US (1) | US7697396B2 (ja) |
JP (1) | JP3836483B2 (ja) |
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EP1868189A1 (en) * | 2005-03-17 | 2007-12-19 | Sharp Kabushiki Kaisha | Aberration detector and optical pickup with same |
Families Citing this family (6)
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JP4275650B2 (ja) * | 2005-05-13 | 2009-06-10 | シャープ株式会社 | 光集積ユニットおよびそれを備えた光ピックアップ装置 |
CN101297362B (zh) * | 2005-11-01 | 2011-12-14 | 三菱电机株式会社 | 光拾取装置和光盘装置 |
JP4694455B2 (ja) | 2006-10-03 | 2011-06-08 | シャープ株式会社 | 収差検出装置およびそれを有する光ピックアップ装置 |
US8483571B2 (en) | 2010-06-30 | 2013-07-09 | Avago Technologies General Ip (Singapore) Pte. Ltd. | Optical beam splitter for use in an optoelectronic module, and a method for performing optical beam splitting in an optoelectronic module |
JP6032535B2 (ja) * | 2011-10-17 | 2016-11-30 | パナソニックIpマネジメント株式会社 | 光ピックアップおよび光記録再生装置 |
US11579014B1 (en) * | 2020-08-20 | 2023-02-14 | Amazon Technologies, Inc. | Optical detector system |
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2004
- 2004-08-25 JP JP2004245925A patent/JP3836483B2/ja active Active
-
2005
- 2005-06-17 WO PCT/JP2005/011134 patent/WO2006022068A1/ja active Application Filing
- 2005-06-17 CN CNA2005800284708A patent/CN101036189A/zh active Pending
- 2005-06-17 US US11/660,824 patent/US7697396B2/en not_active Expired - Fee Related
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JP2000011443A (ja) * | 1998-04-21 | 2000-01-14 | Nec Corp | 光モジュール装置、それに用いる複合プリズムおよびその形成方法 |
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Cited By (2)
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EP1868189A1 (en) * | 2005-03-17 | 2007-12-19 | Sharp Kabushiki Kaisha | Aberration detector and optical pickup with same |
EP1868189A4 (en) * | 2005-03-17 | 2009-05-06 | Sharp Kk | ABERRATION DETECTOR AND OPTICAL BUYER WITH IT |
Also Published As
Publication number | Publication date |
---|---|
JP2006065935A (ja) | 2006-03-09 |
JP3836483B2 (ja) | 2006-10-25 |
US20070242572A1 (en) | 2007-10-18 |
US7697396B2 (en) | 2010-04-13 |
CN101036189A (zh) | 2007-09-12 |
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