WO2004086388A1 - Optical record carrier and optical scanning device - Google Patents
Optical record carrier and optical scanning device Download PDFInfo
- Publication number
- WO2004086388A1 WO2004086388A1 PCT/IB2004/050315 IB2004050315W WO2004086388A1 WO 2004086388 A1 WO2004086388 A1 WO 2004086388A1 IB 2004050315 W IB2004050315 W IB 2004050315W WO 2004086388 A1 WO2004086388 A1 WO 2004086388A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- information
- record carrier
- scanning
- grating
- profile
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- 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
-
- 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
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
-
- 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
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
-
- 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
Definitions
- Fig. 2 shows the positions of the sub-beams of different diffraction orders relative to the pupil of the objective lens of the device
- the scanning device 1 comprises a radiation source, preferably in the form of a semiconductor laser 9 emitting a radiation beam 7.
- the radiation beam, or read beam, is 2004/086388
- a beam splitter 13 for example a semi-transparent mirror, reflects the diverging radiation beam from the radiation source 9 along the optical path towards a collimator lens 14, which converts the diverging beam 7 into a collimated beam 15.
- the collimated beam is incident on an objective system 18.
- the objective system usually called objective lens, may comprise one or more lenses and/or a grating.
- the objective system of Fig. 1 consists of two elements in this example a first lens 18a and a second lens 18b.
- the objective lens 18 has an optical axis 19.
- the objective lens changes the beam 15 into a converging beam 20 which is incident on the entrance face 6 of the record carrier 2.
- the converging beam 20 forms a read spot 21 on the information layer 4.
- the focus error signal and the radial error signal are fed to a servo circuit, which converts these signals into a focus servo signal for controlling a mechanical focus actuator (not shown) in the optical head and a tracking servo signal for controlling the centering of the spot on the track being momentarily scanned.
- the mechanical focus actuator controls the position of the objective lens 18 in the focus direction 33, thereby controlling the actual position of the spot 21 such that it coincides substantially with the plane of the information layer 4.
- a further mechanical actuator such as a radially movable arm (not shown) alters the position of the optical head 1 in the radial direction 34 of the record carrier 2, thereby controlling the radial position of the spot 21 to lie above a track to be followed in the information layer 4.
- the tracks in the record carrier 2 run in a direction perpendicular to the plane of Fig. 1
- the circle 40 having the center 46 represents the cross-section of the zero- order sub-beam in this plane.
- the circles 42 and 44 having centers 48 and 50 represent the cross-sections of the (+1) order sub-beam and the (-1) order sub-beam, respectively, which are diffracted in the tangential, or track direction 36.
- the dashed circle 52 represents the pupil of the objective lens.
- the zero-order sub- beam fills the pupil entirely, so that in reality the circles 40 and 52 coincide. Only that portion of the radiation coming from the information layer that falls within the objective pupil is used for information scanning. Information reading uses the phase variations in the (+1) and (-1) order sub-beams relative to the zero-order sub-beam.
- A( ⁇ ) decreases at decreasing values of ⁇ .
- the amplitude A( ⁇ )cos ⁇ is constant.
- the frequency of the signal Si is then determined by the information which is momentarily being scanned.
- Fig. 3 represents the situation in which the spatial frequency is approximately 1.5 times higher than the cut-off frequency of the scanning device of Figs. 1 and 2.
- the distance d between the center 46 of the zero -order sub-beam and the center 48 of the + first- order sub-beam 42 is approximately 3 times the distance d in Fig. 2. Because these sub- beams have been shifted to the left in Fig. 3, the hatched portions 48 and 60 fall within the pupil 52 of the objective lens.
- the - first-order sub-beam 44 now falls entirely outside this pupil. As shown in Fig.
- the intensity patterns at two consecutive instants will be in accordance with the dash-dot curve 66 and the dashed curve 68, respectively.
- the intensity pattern thus travels across the detection plane during scanning of the read spot 21.
- the radiation this detector receives will consequently vary during scanning.
- the output signal of this detector varies indepenence on the information being read momentarily.
- the width of the detector, in the tangential direction, should be small relative to the period of the intensity pattern. This period is determined by the local spatial frequency of the information areas being scanned. The maximum spatial frequency is known for a specific information structure in a record carrier or of documents or optical representations to be scanned, so that the width of the detector 70 can be adapted accordingly.
- the tilt angle and thus the angle of incidence of the chief ray of the read beam 20 on the record carrier, is chosen such that a portion of the reflected zero -order sub-beam b(0) and a portion of one of the reflected first-order sub-beams pass this pupil.
- the zero-order sub- beam and the first-order sub-beam are deflected downwards so that a portion of the first- order sub-beam b(+l) passes through one half of the pupil of the objective lens and a portion of the zero-order beam b(0) passes through the other half of this pupil.
- Fig. 6 schematically shows elements of the read device and a first embodiment of such a record carrier.
- the rear surface, i.e. the information layer 4, of the record earner has a triangular shape 80, i.e. comprises alternating first regions 82, which show a first inclination or tilt, and second regions 84, which show a second tilt opposed to the first tilt.
- the pitch of the triangular shape is such that it only deflects the read beam while being reflected and does not split this beam into sub-beams. This pitch, or spatial period is thus larger than the pitch of the information structure, i.e. the sum of the length (in the read direction) of an information area and that of an intermediate area.
- the triangular shape is superposed on the information structure. If the read beam is incident on a facet 82, the sub-beams formed by the information structure will be deflected upwards, such that a portion of the zero-order sub-beam b(0) and a portion of the first-order sub-beam b(-l) will pass through different halves of the pupil of the objective lens, thus allowing reading of the high-density information at the location of this facet.
- the sub-beams formed by the information structure will be deflected downwards, such that a portion of the first-order sub-beam b(+l ) and a portion of the zero-order sub-beam will pass through different halves of the objective lens pupil.
- the phase modulation introduced by the information structure in the b(+l) sub-beam is the same as the phase modulation introduced in the b(-l) sub-beam.
- either a portion of the b(+l) or of the b(-l) sub-beam passes through the objective lens pupil together with a portion of the zero-order sub-beam at any moment.
- the radiation-sensitive detection system supplies an information signal Si (26) at each and every moment.
- the triangular shape of the information layer thus allows the reading of the same high-density information structure as can be read with a tilted record carrier.
- the read beam does not pass obliquely through the carrier substrate so that unacceptable large aberrations are no longer introduced into this beam and into the read spot formed by this beam.
- the spherical aberration that may be introduced by the triangular thickness variation of the information layer is so small that it can be disregarded.
- the schematic cross-sectional view of the record carrier with a triangular surface profile may be a tangential or a radial cross-section.
- the succession of the facets 82 and 84 is in the tangential, i.e. the scan, direction, a considerably larger bandwidth is required for the focus servo loop to keep the read beam focused on the information structure.
- the said succession may also be in any direction between the tangential direction and the radial direction.
- the preferred direction is determined by the arrangement of the information areas and the way these areas are read.
- the preferred direction for an information structure arranged in tracks may be different from that for an information structure which is arranged otherwise.
- the information areas succeed each other in the track direction, and the track width sufficies to accommodate only one information area. Only one information area is read at any time.
- An example of a differently arranged info ⁇ nation structure is a so-called 2D-OS (two-dimensional optical storage). These structures are divided into a number of blocks which each comprise a number of information areas. These blocks may have a hexagonal shape. The information areas of one block are all read out simultaneously, for example by means of an array of detection elements, the number of which corresponds to the number of information areas in the block.
- a 2D-OS information structure is described in previously filed co-pending application PHNL020147.
- the preferred direction of the surface profile or of the grating strips may be diagonal with respect to the blocks.
- the information layer may also show a sawtooth-shaped rear surface.
- the period of the regular grating is larger than the period of the information structure, so that the sub-beams b'(+l) and b'(-l) are deflected by the regular grating at an angle that is smaller than the angle at which the sub-beams b(+l) and b(-l) are deflected by the information structure.
- the sub-beams b(+l) an b(-l) are denoted by a single solid arrow line in Fig. 7.
- each of the zero- and first-order sub-beams b(0), b(+l) and b(-l) formed by the information structure will be further diffracted by the regular grating into double-diffracted zero-order and first-order sub-beams.
- double-diffracted sub-beams the sub-beams, b(-l,+l) and b(+l,-l) pass through the pupil of the objective lens and collimator lens, as shown in Fig. 7.
- the first and the second index relate to the order of diffraction caused by the information structure and by the regular grating, respectively.
- the pitch of the regular grating may again be made variable, if the pitch of the information structure is variable, such that the grating pitch follows the pitch of the information structure.
- the regular grating may be any kind of amplitude or phase grating.
- the grating is preferably a phase grating.
- Such a grating may comprise grating strips at another height than the intermediate strips.
- the grating may comprise grating strips having an index of refraction different from that of the intermediate strips.
- the material of the latter grating is a phase change material which has been processed such that the material of the grating strips is in a crystalline state, whilst that of the intermediate strips is in an amorphous state.
- the regular grating may also be constituted by a surface shape similar to that shown in Fig. 5, i.e. a triangular shape or a sawtooth shape, but having a substantially smaller period such that it diffracts incident read radiation. It can be arranged that the same double- diffracted sub-beams as shown in Fig. 7 pass through the pupil of the objective lens.
- the mastering step which forms part of the manufacturing process of the record carrier, may be adapted so as to provide a record carrier with the required surface profile or regular grating.
- a resist layer on top of a substrate is exposed to a focused beam of radiation whose intensity is modulated in accordance with the information to be written.
- the modulated scanning across the resist layer forms a pattern of exposed areas alternating with non-exposed areas in the resist layer.
- Developing the resist and using the resist pattern as an etch mask transfers this pattern into the substrate. From this substrate, which is called a master, different generations of molds are made, which molds are used to make record carriers.
- the required surface profile or regular grating can be encoded in the signal which controls the modulation of the writing beam so that the profile or grating is inscribed in the master.
- the surface profile or grating may be fixed in a separate layer on top of the information layer.
- the separate layer may be a layer of phase change material into which the surface profile or grating can be written by a beam focused onto a spot that is larger than the write spot used for writing the information structure.
- the invention may also be used in a multi-layer record carrier, i.e. a record carrier having two or more information layers.
- a record carrier having two or more information layers.
- Each of the information layers should be provided with a surface profile or regular grating as discussed above.
- the invention may also be applied outside optical recording technology, for example in confocal scanning microscopy.
- the implementation of the invention comprises providing the sample, or in general an information plane, to be viewed or inspected by the microscope with a surface profile or regular grating, for example in the form of a phase plate comprising the profile or grating, which plate covers the information plane during scanning.
- the pitch of the profile or grating should be larger than the pitch(es) expected to be present in the sample.
- the said plate forms part of the scanning device so that the invention is now implemented in the device.
- the scanning device differs from conventional confocal scanning microscopes, or scanning devices in general, in that it comprises a plate provided with means for directing the scanning beam radiation from the information plane in a direction at an acute angle to the chief ray of the incident scanning beam.
- the plate means are similar to those for the record carrier means described above, the plate means need not to be described in detail.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2006506756A JP2006523907A (en) | 2003-03-28 | 2004-03-23 | Optical record carrier and optical scanning device |
EP04722620A EP1611573A1 (en) | 2003-03-28 | 2004-03-23 | Optical record carrier and optical scanning device |
US10/550,333 US20070247984A1 (en) | 2003-03-28 | 2004-03-23 | Optical Record Carrier and Optical Scanning Device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03100817 | 2003-03-28 | ||
EP03100817.0 | 2003-03-28 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2004086388A1 true WO2004086388A1 (en) | 2004-10-07 |
Family
ID=33041063
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2004/050315 WO2004086388A1 (en) | 2003-03-28 | 2004-03-23 | Optical record carrier and optical scanning device |
Country Status (7)
Country | Link |
---|---|
US (1) | US20070247984A1 (en) |
EP (1) | EP1611573A1 (en) |
JP (1) | JP2006523907A (en) |
KR (1) | KR20060002866A (en) |
CN (1) | CN1764961A (en) |
TW (1) | TW200501103A (en) |
WO (1) | WO2004086388A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7791986B2 (en) * | 2006-03-15 | 2010-09-07 | Canon Kabushiki Kaisha | Optical information recording/reproducing apparatus |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4242579A (en) * | 1978-05-11 | 1980-12-30 | U.S. Philips Corporation | Apparatus for the pointwise scanning of an information surface |
EP0110730A2 (en) * | 1982-12-06 | 1984-06-13 | Plasmon Data Systems N.V. | Improvements relating to data storage and recording |
WO1998058370A1 (en) * | 1997-06-16 | 1998-12-23 | Digital Papyrus Corporation | Planar proximity lens element and disk drive using same |
WO1999026240A1 (en) * | 1997-11-18 | 1999-05-27 | Polaroid Corporation | Optical recording systems and media with integral near-field optics |
US20010028620A1 (en) * | 1997-12-24 | 2001-10-11 | Guerra John M. | Information storage systems utilizing media with optically-differentiated data sites |
-
2004
- 2004-03-23 EP EP04722620A patent/EP1611573A1/en not_active Withdrawn
- 2004-03-23 WO PCT/IB2004/050315 patent/WO2004086388A1/en not_active Application Discontinuation
- 2004-03-23 JP JP2006506756A patent/JP2006523907A/en active Pending
- 2004-03-23 US US10/550,333 patent/US20070247984A1/en not_active Abandoned
- 2004-03-23 KR KR1020057018028A patent/KR20060002866A/en not_active Application Discontinuation
- 2004-03-23 CN CNA2004800083437A patent/CN1764961A/en active Pending
- 2004-03-25 TW TW093108123A patent/TW200501103A/en unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4242579A (en) * | 1978-05-11 | 1980-12-30 | U.S. Philips Corporation | Apparatus for the pointwise scanning of an information surface |
EP0110730A2 (en) * | 1982-12-06 | 1984-06-13 | Plasmon Data Systems N.V. | Improvements relating to data storage and recording |
WO1998058370A1 (en) * | 1997-06-16 | 1998-12-23 | Digital Papyrus Corporation | Planar proximity lens element and disk drive using same |
WO1999026240A1 (en) * | 1997-11-18 | 1999-05-27 | Polaroid Corporation | Optical recording systems and media with integral near-field optics |
US20010028620A1 (en) * | 1997-12-24 | 2001-10-11 | Guerra John M. | Information storage systems utilizing media with optically-differentiated data sites |
Also Published As
Publication number | Publication date |
---|---|
TW200501103A (en) | 2005-01-01 |
EP1611573A1 (en) | 2006-01-04 |
JP2006523907A (en) | 2006-10-19 |
CN1764961A (en) | 2006-04-26 |
US20070247984A1 (en) | 2007-10-25 |
KR20060002866A (en) | 2006-01-09 |
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