WO2007138867A1 - Optical information recording method and recording medium - Google Patents
Optical information recording method and recording medium Download PDFInfo
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- WO2007138867A1 WO2007138867A1 PCT/JP2007/060111 JP2007060111W WO2007138867A1 WO 2007138867 A1 WO2007138867 A1 WO 2007138867A1 JP 2007060111 W JP2007060111 W JP 2007060111W WO 2007138867 A1 WO2007138867 A1 WO 2007138867A1
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- light
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- information
- recording
- pattern
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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
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0065—Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
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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
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0938—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following servo format, e.g. guide tracks, pilot signals
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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
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
- G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H2210/00—Object characteristics
- G03H2210/20—2D object
- G03H2210/22—2D SLM object wherein the object beam is formed of the light modulated by the SLM
Definitions
- the present invention relates to an optical information recording method for recording interference fringes due to interference between information light and reference light as a hologram on a recording medium, and a recording medium on which interference fringes are recorded.
- Holographic recording in which information is recorded on a recording medium using holography is generally performed by using information light carrying image information constituting recording light and reference light for recording inside the recording medium. This is done by superimposing and writing the interference pattern created at that time on the recording medium.
- the image information is reproduced by diffracting by the interference pattern by irradiating the recording medium with reproduction reference light (see Patent Document 1).
- volume holography has been developed and attracted attention for practical use for ultra-high density optical recording.
- Volume holography is a method of writing an interference pattern in three dimensions by actively utilizing the thickness direction of the recording medium. Increasing the thickness increases the diffraction efficiency and increases the recording capacity by using multiple recording. There is a feature that can be planned.
- Digital volume holography uses the same recording medium and recording method as volume holography, but the image information to be recorded is
- image information such as an analog picture is also digitized and developed into two-dimensional digital pattern information, which is recorded as image information.
- the two-dimensional digital pattern information is read and decoded to restore the original image information and display it.
- SN ratio signal-to-noise ratio
- the optical axis of the information light and the optical axis of the reference light are coaxial from the same surface side of the recording medium with the information light and the reference light by an object lens.
- An apparatus for irradiating a recording medium is proposed (Patent Document 1).
- a spatial modulation pattern for information light and a spatial modulation pattern for reference light are provided to a spatial light modulator (also abbreviated as SLM) having a large number of pixels arranged in a lattice pattern.
- Information light and reference light carrying two-dimensional digital pattern information were generated by changing the state of light phase, intensity, wavelength, etc. for each pixel by a spatial light modulator.
- a liquid crystal display device may be used as the spatial light modulator, but a DMD (digital 'micromirror' device) may be used.
- the DMD has a plurality of reflective pixels, and can reflect light by changing the reflection direction for each pixel.
- the spatially modulated information light and reference light are irradiated so as to converge on the recording medium by the objective lens, the Fourier transform of the spatial modulation pattern for information light and the spatial modulation pattern for reference light is performed.
- the converted frequency components form interference fringes.
- FIG. 19 shows a configuration of a pickup of an optical information recording / reproducing apparatus using a DMD.
- the pick-up 101 is for irradiating the optical information recording medium 151 with reference light and information light and receiving the reproduction light from the optical information recording medium 151.
- Pickup 101 includes laser light source 103, collimator lens 105, mirror 107, DMD 109, polarization beam splitter 111, relay lens 113, 115, aperture 127, mirror 117, quarter wave plate 119, objective lens 121, ring mask 123, A photodetector 125 is provided.
- laser light is emitted from the laser light source 103, converted into parallel rays by the collimator lens 105, and reflected toward the DM D 109 by the mirror 107.
- the DMD 109 has a plurality of minute mirrors as pixels, and the mirror tilt angle can be changed for each pixel. If the information light spatial modulation pattern and the reference light spatial modulation pattern are displayed on a plurality of pixels of the DMD 109, the reflected light 133 is spatially modulated by the information light spatial modulation pattern and the reference light spatial modulation pattern. Information light and reference light.
- the information light and the reference light pass through the polarization beam splitter 111 and propagate so as to form an image on the entrance pupil plane of the objective lens 121 by the pair of relay lenses 113 and 115.
- the diffracted light is radiated by the aperture 127 disposed in the focal plane between the pair of relay lenses 113 and 115. Is removed by the mirror 117 and reflected by the mirror 117 toward the objective lens 121, and passes through the quarter-wave plate 119.
- the objective lens 121 causes information light and recording reference light to interfere with the hologram recording layer 153 of the optical information recording medium 151 to form holography.
- the reproduction light and the reproduction reference light change the polarization force S90 ° by passing through the quarter-wave plate 119 twice, the reproduction beam and the reproduction reference light are directed toward the photodetector 125 by the polarization beam splitter 111.
- the reflected reference light is removed by the ring mask 123, and the reproduced light is incident on the photodetector 125.
- the optical information recording medium 151 for recording interference fringes is provided with a hologram recording layer 153 and a reflection layer 155 between two substrates 151a and 151b.
- the hologram recording layer 153 is mixed with a monomer that is sensitive to information light and reference light, and a part of the monomer reacts with the polymer by interference fringes formed by interference of the information light and reference light.
- the optical characteristics such as the refractive index are changed, and interference fringes (holograms) are recorded. That is, by recording the interference fringes, a part of the monomer in the hologram recording layer is consumed.
- the monomer concentration in the recorded portion decreases, the monomer diffuses from the surroundings.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2005-32307
- FIG. 20 shows a configuration of a conventional spatial modulation pattern 141 for information light.
- the spatial modulation pattern 141 for information light is formed by arranging a plurality of block units 143, and each block unit 143 is composed of a reference mark 147 and a symbol unit 145 of a certain amount of two-dimensional pattern information. .
- the symbol unit 145 of the two-dimensional pattern information is generated by encoding information to be recorded for each unit of a certain amount of information.
- symbol unit 145 is information to be recorded every 8 bits, and 3 pixels out of 4 ⁇ 4 pixels are turned on pixel 145a (indicated by shading in FIG. 20!). , Encoded according to the arrangement of the ON pixels 145a.
- the reference mark 147 is a two-dimensional pattern having a predetermined shape.
- the position of the entire spatial modulation pattern, the orientation of the entire spatial modulation pattern, and each symbol unit 145 of the two-dimensional pattern information in the spatial modulation pattern.
- This is a standard for the position or orientation of each symbol unit.
- the reference mark 147 is represented by turning on all the 4 ⁇ 4 square pixels.
- the symbol unit 145 in FIG. 20 can be recognized as distinguished from the symbol unit 145 if only 4 ⁇ 4 pixels are on because only three of the 4 ⁇ 4 pixels are on. Can be the standard.
- a block unit 143 has a 4 ⁇ 4 on-pixel 145a at the center as a reference mark 147, and is surrounded by two pixels to obtain a region of 6 ⁇ 6 symbol units (24 Arrange 32 symbol units 145 to fill (24 pixels)! In Fig. 20! /, In the spatial modulation pattern for information light 141, there are 4 block units 143 at the top, 6 at the 2nd level, 8 at the 3rd to 6th levels, and 7th level. 6 on the 4th and 4 on the 8th stage.
- the leftmost block unit 143a (indicated by the dotted line) at the top is a configuration in which only the reference mark 147 is arranged at the center, and symbol units of 2D pattern information are arranged around the reference mark 147. Absent. Therefore, the leftmost block unit 143a in the uppermost stage can be distinguished from other block units, and can be used as a reference for the position and orientation of the spatial modulation pattern for information light 141 itself. For example, when the spatial modulation pattern 141 for information light is detected during reproduction, alignment is performed so that the block unit 143a is at the upper left, and then the block unit force on the right of the block unit 143a is also decoded and reproduced in order. can do.
- each block unit 143 the symbol units are arranged so as to form a square shape with the reference mark 147 as the center. Therefore, the relative position with respect to the reference mark 147 must be specified. Thus, the arrangement of each symbol unit 145 can be specified.
- the spatial light modulator Since the spatial light modulator is an aggregate of minute pixels having a periodic structure, it forms a kind of diffraction grating.
- Figure 21 shows this relationship.
- the interval between the pixels 13 5 of the DMD 109 is the period a of the diffraction grating, and the angle ⁇ of the diffracted light 132 is the interval a between the pixels 135 and d
- the output angle 0 of the reflected light 133 (in FIG. 21—overlapping the third-order diffracted light) is 0 for the incident light 131 and 13 for the DMD 109.
- FIG. 21 shows a case where all the pixels 135 of the spatial light modulator 109 are turned on, and the interval “a” of the pixels 135 is the period of the diffraction grating.
- the spatial modulation pattern for information light or the spatial modulation pattern for reference light has an on pixel and an off pixel. Since they are formed in combination, they have various periodic components, and the period of the diffraction grating is not limited to the interval a between adjacent pixels.
- the pixel interval “a” is minimized as the period of the diffraction grating. Therefore, the spatial frequency with all the pixels 135 turned on is called the fundamental spatial frequency in the spatial light modulator.
- the optical axes ( ⁇ ) of the information light, the recording reference light, and the reproduction reference light reflected and generated by the DMD 109 coincide with the traveling direction (0) of a part of the diffracted light 132.
- the incident angle is equal to the outgoing angle, and the 0th-order diffracted light coincides with the optical axis! /.
- the present inventor compared the optical information recording / reproducing apparatus with the optical axis of information light from the spatial light modulator toward the objective lens by the spatial light modulator.
- We proposed an optical information recording device that was constructed so as not to match the diffracted light of the mth order (m 0, ⁇ 1, ⁇ 2 ⁇ ).
- the optical axis of the information light is configured so as not to coincide with the diffracted light, the bright spot generated by the fundamental spatial frequency of the spatial light modulator Fourier-transformed by the objective lens is placed in the region with the highest light intensity.
- the interference fringes can be strengthened and the hologram size can be reduced.
- the present invention makes it possible to further reduce the hologram size and increase the recording density when the optical axis of the information light does not coincide with the diffracted light! It is an object of the present invention to provide a possible optical information recording method and recording medium. It is another object of the present invention to provide an optical information recording method and a recording medium that can improve the reliability of recording and reproduction more than ever.
- the optical information recording method of the present invention uses a recording reference light and a spatial modulation pattern for information light displayed on a spatial light modulator having a plurality of pixels.
- the information light spatial modulation pattern includes a plurality of reference marks, and the spatial frequency in the area of the reference marks is higher than the basic spatial frequency of the spatial light modulator. It includes a small spatial frequency.
- the direction of the optical axis of the information light is within the range of the traveling direction of the (m + O. 2) order to (m + O. 8) order diffracted light. It is preferable.
- the plurality of pixels are arranged in a lattice shape, and the optical axis direction of the information light is approximately (m + O) with respect to the diagonal direction of the lattice of the plurality of pixels. 5) Next It is preferable to coincide with the traveling direction of the diffracted light.
- the spatial frequency in the area of the reference mark includes a spatial frequency that is half of the fundamental spatial frequency of the spatial light modulator.
- the reference mark preferably includes a pattern in which pixels having different attributes are alternately arranged.
- the direction of the optical axis of the information light is perpendicular to the spatial light modulator.
- the recording medium of the present invention is characterized in that interference fringes are recorded on the hologram recording layer by the optical information recording method.
- optical information recording method of the present invention bright spots with a plurality of fundamental spatial frequencies are arranged in the strongest region by shifting the optical axis of the outgoing light toward the objective lens from the m-th order diffracted light. And the intensity of the interference fringes can be increased.
- the output angle ⁇ from the spatial light modulator is caused by errors in the tilt angle of the reflective surface of the pixel.
- the optical information recording method of the present invention has a plurality of bright spots arranged in a region where the light intensity is high. Therefore, if the light intensity distribution in the hologram recording region is compared with the conventional method. Can be averaged. As a result, the monomer concentration also decreases on average, and the multiple recording characteristics can be improved, so that the recording capacity can be increased.
- the spatial modulation pattern for information light includes a plurality of reference marks, and the spatial frequency in the area of the reference mark is smaller than the basic spatial frequency of the spatial light modulator.
- the frequency Since the frequency is included, the bright spot generated by Fourier transform of the reference mark exists inside the bright spot with the four basic spatial frequencies, and even if the hologram size is reduced, the reference mark does not disappear and reliability is improved. Can be improved. Further, the size of the hologram can be further reduced, and it is possible to improve the recording capacity.
- FIG. 1 is a diagram for explaining the relationship of light in the spatial light modulator of the present invention.
- FIG. 3 is a Fourier transform image in the optical information recording / reproducing apparatus of the present invention.
- FIG. 5 is a table showing one condition of DMD that can implement the present invention.
- FIG. 7 Fourier transform image in the present invention
- FIG. 10 is a diagram for explaining the relationship of light in the transmissive spatial light modulator of the present invention.
- FIG. 11] (A) to (C) are diagrams for explaining the relationship between the spatial modulation pattern and the periodicity t.
- FIG. 12 (A) and (B) are diagrams showing Fourier transform images in each spatial modulation pattern.
- FIG. 13 (A) is a diagram showing a conventional spatial light modulation pattern according to an embodiment of the present invention (B).
- FIG. 15 is an image obtained by reproducing a hologram recorded by the optical information recording method of the present invention.
- FIG. 17 (A) to (H) are diagrams showing another embodiment of the fiducial mark of the present invention.
- FIG. 18 is a schematic configuration diagram showing a configuration of a pickup of the optical information recording / reproducing apparatus of the present invention.
- FIG. 19 is a schematic configuration diagram showing a configuration of a pickup of a conventional optical information recording / reproducing apparatus.
- FIG. 20 is a diagram for explaining the relationship of light in a conventional spatial light modulator.
- FIG. 21 is a diagram for explaining the relationship of light in a conventional spatial light modulator.
- the optical information recording / reproducing apparatus of the present invention displays the spatial modulation pattern for information light and the spatial modulation pattern for reference light for recording on the spatial light modulator 11 during recording to spatially modulate the light.
- Information light and recording reference light are generated. If the recording reference light does not have to be spatially modulated, only the information light spatial modulation pattern may be displayed on the spatial light modulator 11. Then, the information light and the recording reference light are irradiated so as to converge on the recording medium (not shown) by the objective lens 13, and interfere with the hologram recording layer of the recording medium.
- Interference fringes of the recording reference beam are recorded on the hologram recording layer.
- the spatial light modulator 11 when reproducing the interference fringes recorded using the spatially modulated reference light for recording, the spatial light modulator 11 generates the reference light for recording after recording in the spatial light modulator 11.
- the reproduction reference light spatial modulation pattern that is the same as the modulation pattern is displayed, and the light is spatially modulated to generate reproduction reference light.
- the reproduction reference light is irradiated by the objective lens 13 so as to converge on the recording medium, and interferes with interference fringes recorded on the hologram recording layer of the recording medium to generate reproduction light.
- the generated reproduction light is propagated by the optical system including the objective lens 13, and the spatial modulation pattern is detected by the photodetector.
- the emission angle of the light 22 is ⁇ , the wavelength of the light is obtained, and the circumference of the plurality of pixels 12 in the spatial light modulator 11 is obtained.
- the apparatus is configured to satisfy the following relational expression.
- FIG. 1 the reflection-type spatial light modulation Although it is exemplified by the tuner, the same applies to a transmissive spatial light modulator.
- the direction of the optical axis of the emitted light 22 is preferably within the range of the traveling direction of the (m + O. 2) th to (m + O.8) th diffracted light 23.
- the traveling direction of the diffracted light 23 of about (m + O.5) order is preferable. That is, (m + O. 2) ⁇ a (sin 0 -sin 0) ⁇ (m + 0. 8)
- the angle ⁇ of the emitted light 22 is emitted obliquely so that it can be easily divided.
- the display surface of the spatial light modulator 11 that displays the two-dimensional pattern information is the entrance pupil plane of the objective lens 13 (perpendicular to the optical axis).
- the exit angle 0 is 0 °
- Equation 3 becomes m ⁇ — a 'sin ⁇ and the incident angle
- FIG. 2 shows a conventional optical information recording / reproducing apparatus in which the angle 0 of the emitted light coincides with the mth-order diffracted light.
- Fig. 3 shows that the angle 0 of the emitted light coincides with the mth-order diffracted light.
- FIG. 4 shows a Fourier transform image in the optical information recording / reproducing apparatus according to the present invention.
- the bright spot 138 based on the fundamental spatial frequency is located on the optical axis (center).
- the components of the spatial light modulator 109 are the arrangement component 135a resulting from the arrangement of the pixel 135 and the shape of the pixel 135. It can be decomposed into the shape component 135b caused by In FIGS. 2 and 3, the “*” between the arrangement component and the shape component is a convolution calculation symbol.
- the arrangement component 135a is subjected to Fourier transform to obtain an arrangement component pattern 137a having a bright spot 138a arranged in a similar shape to the arrangement component 135a, and the shape component 135b is converted to a pixel shape after Fourier transformation.
- the resulting shape component pattern 137b has an intensity distribution.
- a shape component pattern 137b for a square pixel 135 is shown.
- the region with the strongest intensity is located in the center, and the force is also periodically arranged in the direction facing each side of the square of the pixel 135 (up, down, left and right in Fig. 2). Then, the strength gradually weakens as the central force increases.
- the pattern 137 is a pattern in which the arrangement component pattern 137a and the shape component pattern 137b are overlapped and multiplied by the intensity. This point will first be explained using a one-dimensional Fourier transform waveform. As shown in FIG. 4, a periodic peak corresponding to the arrangement component is shown in the shape component pattern 41 obtained by Fourier transforming the rectangular wave corresponding to the shape component.
- the composite pattern 44 is obtained by superposing the arrangement component patterns 42 and multiplying them by the intensity. Tsuma Thus, the intensity of the shape component pattern 41 at the peak position of the arrangement component pattern 42 becomes the composite pattern 44. In the composite pattern 44, the shape component pattern 41 is indicated by a dotted line.
- the synthesized pattern 44 corresponds to the Fourier transform pattern 137 in the conventional optical information recording / reproducing apparatus in that the center of the shape component pattern 41 and the center of the arrangement component pattern 42 are aligned.
- the angle 0 of the emitted light matches the angle 0 of the mth-order diffracted light.
- the center of the arrangement component pattern 137a and the center of the shape component pattern 137b coincide.
- the Fourier transform pattern 137 has the strongest light intensity in the m-th order diffracted light located at the center. From there, the next bright spot 138 (m ⁇ l, 2...) Is moved away from the center. The strength decreases as the difference from m increases.
- the shape component pattern 137b exists only in the vicinity of the center portion, so each bright spot of the Fourier transform pattern 137 (m ⁇ l, 2 ...) is It exists only in the vicinity of the central part, and the intensity decreases as the luminescent spot and central force move away (the difference from m increases).
- the spatial light modulator 11 in FIG. 3 can also be decomposed into an arrangement component 12 a resulting from the arrangement of the pixel 12 and a shape component 12 b resulting from the shape of the pixel 12 as in the case of FIG.
- the arrangement component 12a is subjected to Fourier transform to obtain an arrangement component pattern 3la having a bright spot 33a arranged in a similar shape to the arrangement component 12a, and the shape component 12b is converted to a pixel shape by Fourier transformation.
- the resulting shape component pattern 31b has an intensity distribution.
- the arrangement component pattern 31a and the shape component pattern 31b in FIG. 3 are the same as those obtained by rotating the arrangement component pattern 137a and the shape component pattern 137b in FIG. 2 by 45 °.
- the optical axis of the outgoing light directed toward the objective lens is configured not to match the m-th order diffracted light
- the bright spot 33a of the arrangement component pattern 31a is shifted from the optical axis.
- the shape component pattern 41 is indicated by a dotted line, and it can be seen that the two peaks near the center are both strong and strong.
- the position of the m + O. 5th-order diffracted light coincides with the optical axis in the diagonal direction of pixel 12 (lateral direction 15 in FIG. 3, oblique 45 ° direction in FIG. 2).
- the optical axis is the center of the four bright spots 33a.
- the period a in Equation 3: m ⁇ a (sin 0 -sin 0) for obtaining the diffraction order in the diagonal direction is the rotation axis 1 as shown in Fig. 3.
- the center of the shape component pattern 31b is the output angle ⁇ .
- the pattern 31 obtained by superimposing the arrangement component pattern 3 la and the shape component pattern 3 lb overlaps with each other as the strength increases at the bright spot 33 at the four basic spatial frequencies near the optical axis.
- the intensity of the bright spot 33 due to each fundamental spatial frequency decreases.
- the optical axis of the outgoing light directed toward the objective lens is configured not to match the m-th order diffracted light
- the bright spot due to the fundamental spatial frequency of the spatial light modulator is shown in the strongest region.
- a plurality of 33 can be arranged, and the intensity of interference fringes can be increased.
- the output angle ⁇ varies due to an error in the tilt angle of the reflective surface of the pixel.
- the monomer concentration in the hologram recording layer of the optical information recording medium is partially depleted.
- the bright spots 33 having a plurality of fundamental spatial frequencies are arranged in the region where the light intensity is strong, the light intensity distribution in the hologram recording region is compared with the conventional one. Can be averaged. As a result, the monomer concentration also decreases on average, and the multiple recording characteristics can be improved, so that the recording capacity can be increased.
- the hologram size can be reduced.
- the hologram recording area 139 is indicated by a white circle.
- the hologram recording area 34 (indicated by white circles) can be reduced to a size that includes it. Accordingly, since the size of each hologram can be reduced, a larger number of holograms can be recorded accordingly, and the recording capacity can be increased.
- the tilt angle of the pixel which is the traveling direction of the diffracted light in the diagonal direction (m + O.5) when using light with a wavelength of 532 nm and light with a wavelength of 410 nm.
- the DMD tilt angle is designed to be 11 to 13 °. Therefore, within the angle range, when using light with a wavelength of 532 nm, the tilt of the pixel is set to be the direction of travel of the fifth-order light. If the angle is 12.18 °, the angle of incidence on the DMD is 24.36 °, and light with a wavelength of 410 nm is used, the pixel tilt angle is 11.87 so that the 9.5th-order light travels. ° To DMD The incident angle is 23.74 °.
- FIGS. 6 to 9 show that for a DMD using light with a wavelength of 532 nm and pixel tilt angles of 11.4 °, 12.0 °, 12.2 °, and 12.4 °, 24.4
- a Fourier transform image is shown when light is incident at an incident angle of °.
- the upper row shows the case where all the pixels are in the on state, and the lower row shows the case where the pixels in the on state and the off state (hatched with hatching) are randomly arranged.
- each bright spot is blurred and the light intensity distribution is widened.
- the light intensity is still weak in a part of the hologram recording area (white circle) 64, and it is difficult to record and reproduce reliable information.
- the lower Fourier transform pattern 75 in which the on-pixel 72a and the off-pixel 72b are randomly arranged is also slightly deviated to the left of the center, but the light intensity distribution spreads over the entire hologram recording area (white circle) 74. Therefore, interference fringes can be recorded and information can be recorded and reproduced with high reliability.
- X 12. 4 ° -0. 4 °.
- the upper Fourier transform pattern 93 has a slightly strong light intensity at the right bright spot among the four bright spots with four fundamental spatial frequencies near the center, but the other three bright spots are sufficiently strong.
- the hologram recording area (white circle) 94 can record interference fringes throughout.
- the range of the tilt angle is a design value for one product, and is not limited to the above numerical value.
- the tilt angle is 10.5 °
- the direction of travel of the quintic light can be used when using light with a wavelength of 532 nm, and when using light with a wavelength of 410 nm, 8. Since the direction of travel of the fifth-order light can be set, a highly versatile DMD can be manufactured. Also, if the pixel spacing is changed, the angle must be redesigned.
- FIG. 10 shows the relationship between the incident light 21, the emitted light 22, and the diffracted light 23 in the transmissive spatial light modulator 11.
- the incident angle of the incident light 21 is ⁇
- the angle of light 22 emitted from the optical modulator 11 is ⁇ , the wavelength of the light is obtained, and the spatial light modulator 11
- Equation 3 111 ⁇ ⁇ & 110 -sin0
- the spatial light modulator 11 of the type has a refracting means 16.
- incident light 21 is incident on the spatial light modulator 11 at an incident angle ⁇ .
- the outgoing light 22 modulated by is emitted through the refracting means 16 at an outgoing angle ⁇ .
- the angle 0 of the outgoing light 22 is 0 °, that is, the optical axis of the outgoing light 22
- Equation 3 m ⁇ — a'sin0, and the incident angle 0 is (m + O.2)
- the angle ⁇ with respect to incident light 21 is r 0 of (m + O.2) l ⁇ -a-sin0 ⁇ (m + O.8)
- the angle of the output light 22 with respect to the incident light 21 satisfies the relation of 0 force m ⁇ —a'sin0, and the optical axis of the output light 22 is perpendicular to the spatial light modulator 11. And the configuration does not match the diffracted light.
- an angled phase plate can be used as the refracting means 16.
- the refracting means 16 is provided on the exit surface side of the spatial light modulator 11. However, the refracting means 16 may be arranged on the incident surface side, or the refracting means 16 may be realized as a function inside the spatial light modulator 11.
- the spatial modulation pattern for information light includes a plurality of reference marks, and the spatial frequency in the reference mark region is smaller than the basic spatial frequency of the spatial light modulator. To include the frequency. From another viewpoint, it is sufficient that the periodicity of the pixels in the reference mark region is larger than the periodicity of the pixels of the spatial light modulator. For example, the spatial frequency of a pattern in which ON pixels and OFF pixels are alternately arranged is half the basic spatial frequency.
- FIGS. 11 (A) to 11 (C) each show an 8-pixel spatial modulation pattern arranged linearly in the upper stage, and the light intensity and periodicity t in the lower stage. It is a figure for demonstrating the relationship between and periodicity t.
- the spatial modulation pattern is composed of a binary force of an on state and an off state.
- FIG. 11 (A) shows a spatial modulation pattern 1101 in which all eight pixels are in the ON state, and has a period t of the distance a between adjacent pixels, so that the spatial frequency is the fundamental spatial frequency.
- FIG. 11 (A) the light intensity between the pixels is 0 because of the gap between the pixels of the spatial light modulator.
- FIG. 11B shows a spatial modulation pattern 1102 in which ON pixels and OFF pixels are alternately arranged, and has a period t of an interval of 2 pixels (2 Xa).
- the period t of the spatial modulation pattern 1102 in Fig. 11 (B) is the spatial modulation in Fig. 11 (A).
- Fig. 11 (C) shows a spatial modulation pattern 1103 in which ON and OFF pixels are arranged alternately in two pixels, with a period t of 4 pixels (4 X a) and one image.
- the 3 has a period t with an interval a. Of these, the period t is four times the period t.
- the intermodulation pattern 1103 includes a spatial frequency that is a quarter of the fundamental spatial frequency.
- FIGS. 12A and 12B are similar to FIG. 3, in which the position of the m + O. Fifth-order diffracted light in the diagonal direction of the pixel coincides with the optical axis, that is, there are four optical axes.
- a spatially transformed pattern 1201 in which all the pixels are in an on state and a spatial modulation pattern 1202 in which the pixels are in an on state in a lattice form in the state of being the center of the bright spot 33 by the basic spatial frequency is shown.
- the reference mark 147 has all the 4 x 4 square pixels turned on (Fig.
- the pattern is indicated by shading).
- the spatial frequency in the region of the reference mark 147 becomes the fundamental spatial frequency
- the bright spot by the reference mark obtained by Fourier transform becomes the pattern 1203 in FIG.
- the bright spot due to the reference mark first deviates from the range of hologram 1207. Becomes worse. If the hologram 1207 is further reduced in size, the reference mark disappears from the reproduced spatial modulation pattern, and information cannot be reproduced.
- the spatial frequency is half of the basic spatial frequency.
- a bright spot is also generated at the center position of a square (see dotted line 1206 in Figs. 12A and 12B) formed by bright spots 1205 having four adjacent fundamental spatial frequencies.
- the bright spot due to the reference mark exists inside the bright spot with the four fundamental spatial frequencies, and even if the size of the hologram 1207 is reduced, the reference mark does not disappear and the reliability can be improved. Further, the size of the hologram can be further reduced, and the recording capacity can be improved.
- the bright spot by the reference mark is located on the optical axis because the reference mark can be reproduced more reliably. For example, as shown in FIG. m + 0. If the position of the fifth-order diffracted light coincides with the optical axis, that is, the center of the bright spot 33 by the basic spatial frequency of the optical axis force, the reference mark has a spatial frequency that is half the basic spatial frequency. If you include it.
- FIG. 13 (A) shows a conventional spatial light modulation pattern for information light 1301 and a spatial light modulation pattern for reference light 1302, and FIG. 13 (B) is a space for information light in one embodiment of the present invention.
- An optical modulation pattern 1303 and a spatial light modulation pattern 1302 for reference light are shown.
- information light spatial light modulation patterns 1301 and 1303 are arranged at the center, and an annular reference light spatial light modulation pattern 1302 is arranged therearound.
- the overall configuration of the spatial light modulation patterns 1301 and 1303 for information light encodes the information to be recorded for each unit of a certain amount of information to generate a symbol unit of two-dimensional pattern information
- the symbol unit and the reference mark are formed as one block unit, and are formed by arranging a plurality of block units.
- the reference mark 1306 is a pixel, as is clear from the partially enlarged view shown on the left side of the figure. Is a pattern in which is turned on in a lattice shape. Note that the enlarged portions of FIGS. 13A and 13B are portions of block units in which only the reference marks 1305 and 1306 are arranged and symbol units are not arranged, and the spatial light modulation pattern for information light 1301 , 1303 itself is the location and orientation standard.
- FIG. 14 and FIG. 15 show the spatial light modulation when reproducing the recorded interference fringes by actually changing the size of the aperture (indicated by reference numeral 227 in FIG. 18) (also called aperture size). It is a pattern.
- 14 uses the spatial modulation pattern for information light 1301 and the spatial modulation pattern for reference light 1302 in FIG. 13 (A)
- FIG. 15 uses the spatial modulation pattern for information light 1303 and the reference light in FIG. 13 (B). Holograms were recorded using the spatial modulation pattern 1302. In Fig. 14 and Fig.
- the upper five reproduced images have 8.4m in opening size in order of left force. m, 8. Omm, 7.6 mm, 7.2 mm, and 6.8 mm were recorded and played back.
- the four playback images in the lower row had an aperture size of 6.4 mm, 6. Omm in order from the left. , 5.6mm and 5.2mm recorded and reproduced.
- the reference mark can be confirmed in the upper stage.
- the reference mark disappears in the lower stage where the aperture size is 6.4 mm or less.
- the mark cannot be played.
- the optical information recording method of the present invention shown in FIG. 15 was used, the fiducial mark could be confirmed both in the upper and lower stages, and the fiducial mark could be reproduced even if the aperture was reduced.
- FIG. 16 is a diagram showing the relationship between the aperture size (aperture size) and the bit error rate of the reproduced reference mark. If the aperture is reduced, the size of the recorded hologram is also reduced.
- the bit error rate increases rapidly when the aperture size is 6.4 mm or less. However, it cannot be played at all.
- the bit error rate does not increase so much even if the aperture size is 6.4 mm or less, and it becomes 4 mm. However, the bit error rate could be reduced to about 0.2.
- FIGS. 17A to 17H show another embodiment of the reference mark of the present invention.
- the white pixels are in the on state and the shaded pixels are in the off state.
- the force is not limited to 4 ⁇ 4 pixels with 4 ⁇ 4 pixels as the reference mark region.
- the reference mark region is a 3 ⁇ 4 pixel
- the reference mark region is a 5 ⁇ 5 pixel.
- FIG. 18 shows the configuration of the pickup 201 of the optical information recording / reproducing apparatus of the present invention using a reflective spatial light modulator.
- the pickup 201 of the present invention is the same as the pickup 201 of the optical information recording / reproducing apparatus of the present invention, the recording / reproducing light source 203, collimator lens 205, mirror 207, spatial light modulator 209, polarization beam splitter 211, relay lenses 213, 215, An aperture 227, a mirror 217, a quarter-wave plate 219, an objective lens 221, a ring mask 223, and a light detection means 225 are provided.
- the light emitted from the recording / reproducing light source 203 is converted into parallel rays by the collimator lens 205 and directed to the spatial light modulator 209 by the mirror 207. Reflected with force.
- the incident angle of the incident light 231 to the spatial light modulator and the period of the pixels of the spatial light modulator are configured.
- the angle of inclination of the reflective surface of the pixel is also set so that the outgoing light 232 of the spatial light modulator does not match the diffracted light 233. Composed.
- each component of the optical information recording / reproducing apparatus will be described in order.
- the recording / reproducing light source 203 emits light for forming information light for recording information and light for forming reference light for recording and light for forming reference light for reproduction for reproducing information.
- a semiconductor laser that generates a coherent linearly polarized light beam can be used.
- a shorter wavelength is advantageous in order to perform high-density recording, and it is preferable to employ a blue laser (for example, wavelength 532 nm) or a green laser (for example, wavelength 410 nm). Further, a solid laser can be used as the light source 203.
- the collimator lens 205 converts the divergent light beam from the recording / reproducing light source 61 into a substantially parallel light beam.
- the mirror 207 reflects the light from the recording / reproducing light source 203 toward the spatial light modulator 209. With the mirror 207, the incident angle of the light 231 incident on the spatial light modulator 209 can be adjusted. For example, the position or angle of the mirror may be changed with respect to light having different wavelengths so that the outgoing light 232 of the spatial light modulator does not coincide with the diffracted light 233.
- Spatial light modulator 209 has a plurality of pixels, and uses a transmissive or reflective spatial light modulator that can modulate the phase or Z and intensity of emitted light for each pixel. be able to.
- a DMD digital 'micromirror' device
- a matrix type liquid crystal element can be used as the spatial light modulator 209. DMD spatially modulates the intensity of incident light by changing the reflection direction for each pixel, and reflects the incident light for each pixel.
- the phase can be spatially modulated by changing the position.
- the liquid crystal element can spatially modulate the intensity and phase of incident light by controlling the alignment state of the liquid crystal for each pixel.
- the phase of light can be spatially modulated by setting the phase of outgoing light for each pixel to one of two values that differ from each other by ⁇ radians.
- the spatial light modulator 209 is of a reflective type, and is disposed so as to reflect incident light and emit it perpendicularly to the spatial light modulator.
- the information light spatial modulation pattern is displayed on the display surface of the spatial light modulator 209, and information light is generated by spatially modulating the light with the displayed information light spatial modulation pattern.
- the spatial modulation pattern for information light includes two-dimensional pattern information obtained by encoding information to be recorded, and is represented by two-dimensionally arranging pixels whose attributes are changed in multiple stages.
- the state of light such as phase and intensity is changed in multiple stages.
- the power explained in the method of changing the light intensity for each pixel in two steps of on (white pixel) and off (black or shaded pixel) is not limited to this method. Absent.
- the phase of light may be changed, or it may be changed to three or more steps instead of two steps.
- the recording reference light may be spatially modulated or may not be spatially modulated.
- the recording reference light is spatially modulated, multiple recording can be performed by changing the spatial modulation pattern of the recording reference light, and information recording can be performed by keeping the spatial modulation pattern of the recording reference light as a key. Security against unauthorized access can be improved.
- the reference light is spatially modulated, for example, the spatial light modulator displaying the reference light spatial modulation pattern is irradiated with light to generate the reference light spatially modulated by the reference light spatial modulation pattern. it can.
- the information light and the recording reference light are generated by one spatial light modulator 209, an information light region and a reference light region are provided on the display surface of the spatial light modulator 209, respectively.
- the pattern and the spatial modulation pattern for recording reference light may be displayed.
- the information light region is preferably arranged near the center of the spatial light modulator 209, and the reference light region is preferably arranged in an annular shape so as to surround the information light region.
- a spatial light modulator that generates information light and recording reference light may be provided separately.
- the light from the light source 203 is split by a beam splitter or the like, and one light is Information light may be spatially modulated by one spatial light modulator, and reference light may be generated by spatially modulating the other light by a second spatial light modulator.
- the spatial light modulator that generates the information light and the reference light are generated.
- the spatial light modulator has a conjugate relationship, and is propagated to the entrance pupil plane of the object lens 221 by the pair of relay lenses 213 and 215.
- the optical axis of the outgoing light 23 emitted from the spatial light modulator 209 is about the diagonal direction of the lattice of the plurality of pixels.
- the optical axis moves in the diagonal direction of the bright spot on the Fourier plane as shown in the arrangement component pattern 31a in FIG. 3, so the distance to each bright spot close to the optical axis force This is preferable because it is easy to equalize.
- the distances to four adjacent bright spots will be equal.
- the intensity of the Fourier transform image can be flattened. Even when the plurality of pixels of the spatial light modulator 209 are arranged in a non-lattice arrangement, for example, a honeycomb and shifted in a stepwise manner, the optical axis does not coincide with the m-th order diffracted light. As a result, a plurality of bright spots can be arranged in a strong region in the Fourier transform image.
- the arrangement component pattern 31a in FIG. 3 is changed.
- the plurality of pixels of the spatial light modulator 209 may have a shape other than a square shape.
- it may be a rectangle, rhombus, hexagon, triangle, or circle.
- the shape component pattern 31b in FIG. 3 changes according to the shape.
- the polarization beam splitter 211 has a semi-reflective surface that reflects or transmits linearly polarized light (for example, P-polarized light) and transmits or reflects linearly polarized light (for example, S-polarized light) perpendicular to the polarized light.
- a polarization beam splitter 211 transmits information light, recording reference light, or reproduction reference light emitted from the spatial light modulator 209, and reproduces and records the reproduction light generated from the hologram recording layer of the recording medium.
- the reproduction reference light reflected by the medium is reflected toward the light detection means 225.
- the pair of relay lenses 213 and 215 are arranged between the spatial light modulator 209 and the objective lens 221.
- the image displayed on the spatial light modulator 209 is formed on the entrance pupil plane of the objective lens 221. That is, the distance from the spatial light modulator 209 to the first relay lens 213 is the focal length fl of the first relay lens 213, and the distance from the second relay lens 215 to the entrance pupil plane of the objective lens 221 is the second distance
- the distance between the first and second relay lenses 213 and 215 is the sum of the focal length fl of the first relay lens 213 and the focal length f2 of the second relay lens 215. It is arranged to become.
- a pair of relay lenses 213 and 215 are arranged between the objective lens 221 and the light detection means 225, and the hologram recording layer 253 of the recording medium 251 is read by reference light for reproduction.
- the light detection means 225 is arranged again to form an image on the exit pupil plane of the objective lens 221 of the reproduction light generated from the light. That is, the exit pupil surface force of the objective lens 221 is also the distance to the second relay lens 215 is the focal length f2, the distance from the first relay lens 213 to the light detecting means 225 is the focal length fl, and the first and first The second relay lenses 213 and 215 are arranged such that the distance between them is the sum of the focal length fl and the focal length f2.
- the arrangement of the pair of relay lenses 213 and 215 changes by appropriately arranging other optical elements. For example, if a magnifying lens is placed between the first relay lens 213 and the light detection means 225, the distance from the first relay lens 213 to the entrance pupil plane of the magnifying lens is the focal distance fl. Be placed.
- the aperture 227 is disposed at the focal position between the first and second relay lenses 213 and 215, and removes higher-order diffracted light.
- the size of the recording area of the hologram can be adjusted.
- the spatial frequency in the area of the reference mark includes a spatial frequency smaller than the basic spatial frequency of the spatial light modulator, it can be reproduced even if the hologram recording area is reduced.
- the opening 227 may be reduced to reduce the hologram recording area.
- the optical axis of outgoing light 232 matches the traveling direction of m + O. 5th order diffracted light
- the m-order and m + 1 first-order diffracted light 233 in the vicinity thereof may be passed, and diffracted light having a higher order may be blocked.
- the means for adjusting the recording area of the hologram is not limited to the opening 227.
- the mirror 217 reflects the traveling direction of light toward the objective lens 221 and is not necessary depending on the configuration of the optical system.
- the quarter-wave plate 219 is a phase plate that changes the optical path difference of polarized light that vibrates in directions perpendicular to each other by a quarter wavelength. P-polarized light is converted to circularly polarized light by the quarter-wave plate 219, and further, when this circularly polarized light passes through the quarter-wave plate 219, it is changed to S-polarized light.
- the reference beam for reproduction and the reproduction beam at the time of reproduction can be separated by the polarization beam splitter 211.
- the objective lens 221 irradiates the recording medium 251 with information light and recording reference light imaged on the entrance pupil plane, and causes the hologram recording layer 253 to interfere and record.
- the reproduction reference light imaged on the entrance pupil plane is irradiated onto the recording medium 251 and the reproduction light generated from the hologram recording layer 253 of the recording medium 251 is incident on the exit pupil plane.
- the image is formed.
- the objective lens 221 is shown as a single lens, but a compound lens may be used.
- the ring mask 223 is for removing reproduction reference light reflected by the reflective layer 255 of the recording medium 251 together with reproduction light during reproduction.
- the light detection means 225 has a plurality of light receiving pixels, and can detect the intensity of light received for each light receiving pixel.
- a CCD solid-state image sensor or a MOS type solid-state image sensor can be used.
- a smart optical sensor in which a MOS type solid-state imaging device and a signal processing circuit are integrated on one chip for example, WO plus E, September 1996, No. 202, pages 93 to 99) : Shine ,.) use! /, Techi,.
- This smart optical sensor has a high transfer function with a large transfer rate, so it can be played back at high speed by using this smart optical sensor, for example, with a transfer rate on the order of G (giga) bits Z seconds. Playback can be performed.
- the recording medium 251 has a hologram recording layer 253 on which interference fringes are recorded.
- the recording medium 251 further includes a first substrate 251a, a reflective layer 255, and a second transparent substrate 251b.
- a disk-shaped or card-shaped one can be used, and recording and reproduction may be performed while the recording medium 251 is rotated, or may be fixed at the time of recording and reproduction.
- the disk drive mechanism used in CD drives and DVD drives can be used. Is preferred because it makes it easier to have compatibility with CD and DVD drives.
- information for positioning is recorded in advance on the recording medium 251 and a feedback mechanism is used for positioning of the irradiation position because more accurate positioning can be performed.
- a pit may be formed as positioning information on the surface of the reflective layer 255 of the recording medium 251 and the positioning information may be recorded in advance.
- the light for recording or reproduction is separated from the reflection layer for the light for reading the positioning information forming the pits.
- a wavelength selective reflection layer that reflects light may be provided.
- the positioning information is superimposed on the recording / reproducing area. Recording can be performed, and the pickup device can be arranged on the same side of the recording medium, so that the recording / reproducing apparatus can be downsized.
- the optical information recording apparatus The operation of the optical information recording apparatus will be described.
- Light emitted from the light source 203 is converted into parallel light by the collimator lens 205 and reflected by the mirror 207 toward the spatial light modulator 209.
- Information light and recording reference light are generated by the information light spatial modulation pattern and the reference light spatial modulation pattern displayed on the spatial light modulator 209.
- the spatial modulation pattern for information light has a plurality of reference marks, and the spatial frequency in the region of the reference mark is smaller than the basic spatial frequency of the spatial light modulator 209. To include.
- the optical axis of light directed toward the spatial light modulator 209 force objective lens (the central ray in the figure) is arranged so as not to coincide with the traveling direction of the m-th order diffracted light 233.
- the optical axis of the information light and the optical axis of the recording reference light are located on the same line. Coincides with the traveling direction of m-order diffracted light 233 Not done.
- the information light and the recording reference light pass through the polarization beam splitter 211, and are displayed on the spatial light modulator 209 on the entrance pupil plane of the objective lens 221 by the pair of relay lenses 213 and 215.
- the modulation pattern is propagated to form an image.
- high-order diffracted light is removed by the aperture 227, reflected by the mirror 217 toward the objective lens 221, and passes through the quarter-wave plate 219. Interference fringes of information light and recording reference light are recorded on the hologram recording layer 253 of the recording medium 251.
- the recording medium on which the interference fringes are recorded by the recording method of the present invention can reproduce information by reproducing the reference mark even when the hologram size is small! Therefore, the reliability as an information recording medium is improved, and the recording capacity is also improved.
- the light emitted from the light source 203 is converted into parallel light by the collimator lens 205 and reflected by the mirror 207 toward the spatial light modulator 209. Then, the reference light for reproduction is generated by the spatial modulation pattern for reference light displayed on the spatial light modulator 209.
- the reference light spatial modulation pattern of the reproduction reference light at the time of reproduction is a reference light spatial modulation pattern of the recording reference light irradiated when information recorded on the recording medium is recorded.
- the optical axis of light directed from the spatial light modulator 209 to the objective lens does not coincide with the traveling direction of the m-th order diffracted light 233.
- an annular reproduction reference beam is arranged, and its optical axis does not coincide with the traveling direction of the mth-order diffracted beam 233.
- the reproduction reference light emitted from the spatial light modulator 209 passes through the polarization beam splitter 211 and is displayed on the spatial light modulator 209 on the entrance pupil plane of the objective lens 221 by the pair of relay lenses 213 and 215.
- the transmitted spatial modulation pattern for reference light is propagated so as to form an image.
- high-order diffracted light is removed by the aperture 227, reflected by the mirror 217 toward the objective lens 221, and passes through the quarter-wave plate 219.
- the recording medium 251 is irradiated by the objective lens 221 and is diffracted by the interference fringes recorded on the hologram recording layer 253 of the recording medium 251 to generate reproduction light having the same information as the information light at the time of recording.
- the reproduction light is reflected by the reflection layer 255 of the recording medium 251 and is reflected from the recording medium 251 to the objective lens 2.
- a pair of relay lenses 215 are emitted so as to form a spatial modulation pattern for information light on the exit pupil plane by the objective lens 221 so that a powerful image is formed again on the light detection means 255. , 213.
- the reproduction light passes through the quarter-wave plate 219 and is reflected by the mirror 217 toward the polarization beam splitter 211. Since the reproduction light passes through the quarter-wave plate 219 twice compared to the reproduction reference light at the time of irradiation, the polarization direction is shifted by 90 °. Reflected toward 255.
- the reproduction reference light is removed by the ring mask 223, and the spatial modulation pattern of the reproduction light is detected by the light detection means 225.
- the detected information is sent to a control means (not shown), and the control means decodes and reproduces the information.
- the present invention is not limited to the above-described embodiment, and various kinds are necessary as necessary. Can be changed.
- a hologram is formed by irradiating the recording medium with the same surface side force information light and the reference light of the recording medium so that the optical axis of the information light and the optical axis of the reference light are coaxial.
- a two-beam interference type hologram may be formed by irradiating the recording medium with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light intersect at a certain angle.
- at least one of the light spatially modulated by the spatial light modulator is configured such that the light emitted from the spatial light modulator does not coincide with the mth-order diffracted light as described above. ,.
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Abstract
[PROBLEMS] To provide an optical information recording method by which hologram size is reduced and recording density is improved, and to provide a recording medium. [MEANS FOR SOLVING PROBLEMS] An optical information recording apparatus records interference fringes of a recording reference beam and an information beam by applying the recording reference beam and the information beam spatially modulated by a spatial light modulator (11) having a plurality of pixels (12) to an recording medium by converging the beams to the recording medium by an objective lens (13). The optical axis (22) of the information beam traveling to the objective lens (13) from the spatial light modulator (11) does not accord with the mth diffracted beam (23) (m=0, ±1, ±2 and so on) diffracted by the spatial light modulator, a spatial modulation pattern (1303) for information beams includes a plurality of reference marks (1306), and a spatial frequency in a region of the reference mark (1306) includes a spatial frequency smaller than the basic spatial frequency of the spatial light modulator.
Description
明 細 書 Specification
光情報記録方法及び記録媒体 Optical information recording method and recording medium
技術分野 Technical field
[0001] 本発明は、情報光と参照光との干渉による干渉縞をホログラムとして記録媒体に記 録する光情報記録方法及び干渉縞が記録された記録媒体に関する。 The present invention relates to an optical information recording method for recording interference fringes due to interference between information light and reference light as a hologram on a recording medium, and a recording medium on which interference fringes are recorded.
背景技術 Background art
[0002] ホログラフィを利用して記録媒体に情報を記録するホログラフィック記録は、一般的 に、記録用光を構成するイメージ情報を担持した情報光と記録用参照光とを記録媒 体の内部で重ね合わせ、その時にできる干渉パターンを記録媒体に書き込むことに よって行われる。記録された情報の再生時には、その記録媒体に再生用参照光を照 射することにより、干渉パターンによる回折によりイメージ情報が再生される(特許文 献 1参照)。 [0002] Holographic recording in which information is recorded on a recording medium using holography is generally performed by using information light carrying image information constituting recording light and reference light for recording inside the recording medium. This is done by superimposing and writing the interference pattern created at that time on the recording medium. When the recorded information is reproduced, the image information is reproduced by diffracting by the interference pattern by irradiating the recording medium with reproduction reference light (see Patent Document 1).
[0003] 近年では、超高密度光記録のために、ボリュームホログラフィ、特にデジタルボリュ ームホログラフィが実用域で開発され注目を集めている。ボリュームホログラフィとは、 記録媒体の厚み方向も積極的に活用して、 3次元的に干渉パターンを書き込む方式 であり、厚みを増すことで回折効率を高め、多重記録を用いて記録容量の増大を図 ることができるという特徴がある。そして、デジタルボリュームホログラフィとは、ボリユー ムホログラフィと同様の記録媒体と記録方式を用いつつも、記録するイメージ情報は In recent years, volume holography, particularly digital volume holography, has been developed and attracted attention for practical use for ultra-high density optical recording. Volume holography is a method of writing an interference pattern in three dimensions by actively utilizing the thickness direction of the recording medium. Increasing the thickness increases the diffraction efficiency and increases the recording capacity by using multiple recording. There is a feature that can be planned. Digital volume holography uses the same recording medium and recording method as volume holography, but the image information to be recorded is
2値ィ匕したデジタルパターンに限定した、コンピュータ指向のホログラフィック記録方 式である。このデジタルボリュームホログラフィでは、例えばアナログ的な絵のような画 像情報も、ー且デジタイズして、 2次元デジタルパターン情報に展開し、これをィメー ジ情報として記録する。再生時は、この 2次元デジタルパターン情報を読み出してデ コードすることで、元の画像情報に戻して表示する。これにより、再生時に SN比 (信 号対雑音比)が多少悪くても、微分検出を行ったり、 2値ィ匕データをコードィ匕しエラー 訂正を行ったりすることで、極めて忠実に元の情報を再現することが可能になる。 This is a computer-oriented holographic recording method that is limited to a binary digital pattern. In this digital volume holography, image information such as an analog picture is also digitized and developed into two-dimensional digital pattern information, which is recorded as image information. During playback, the two-dimensional digital pattern information is read and decoded to restore the original image information and display it. As a result, even if the SN ratio (signal-to-noise ratio) is somewhat poor during playback, differential detection is performed, or binary data is coded and error correction is performed, so that the original information is faithfully reproduced. Can be reproduced.
[0004] かかるホログラフィック記録を行う光記録再生装置として、情報光および参照光を対 物レンズによって記録媒体の同一面側から、情報光の光軸と参照光の光軸とが同軸
となるように記録媒体に照射する装置が提案されて 、る (特許文献 1)。 [0004] As an optical recording / reproducing apparatus for performing such holographic recording, the optical axis of the information light and the optical axis of the reference light are coaxial from the same surface side of the recording medium with the information light and the reference light by an object lens. An apparatus for irradiating a recording medium is proposed (Patent Document 1).
[0005] この光記録再生装置においては、格子状に配列された多数の画素を有する空間 光変調器 (SLMと略すこともある)に情報光用空間変調パターンおよび参照光用空 間変調パターンを表示し、空間光変調器によって光の位相、強度、波長等の状態を 各画素毎に変化させることで 2次元デジタルパターン情報を担持した情報光および 参照光を生成していた。空間光変調器として、液晶表示装置を使用することもあるが 、 DMD (デジタル 'マイクロミラー'デバイス)を使用することも考えられる。 DMDは、 複数の反射型の画素を有し、画素毎に反射方向を変えて反射することができる。 In this optical recording / reproducing apparatus, a spatial modulation pattern for information light and a spatial modulation pattern for reference light are provided to a spatial light modulator (also abbreviated as SLM) having a large number of pixels arranged in a lattice pattern. Information light and reference light carrying two-dimensional digital pattern information were generated by changing the state of light phase, intensity, wavelength, etc. for each pixel by a spatial light modulator. A liquid crystal display device may be used as the spatial light modulator, but a DMD (digital 'micromirror' device) may be used. The DMD has a plurality of reflective pixels, and can reflect light by changing the reflection direction for each pixel.
[0006] そして、空間的に変調された情報光および参照光は、対物レンズによって記録媒 体に対し収束するように照射されるので、情報光用空間変調パターンおよび参照光 用空間変調パターンのフーリエ変換された周波数成分同士が干渉縞を形成すること になる。 [0006] Since the spatially modulated information light and reference light are irradiated so as to converge on the recording medium by the objective lens, the Fourier transform of the spatial modulation pattern for information light and the spatial modulation pattern for reference light is performed. The converted frequency components form interference fringes.
[0007] DMDを使用した光情報記録再生装置のピックアップの構成を図 19に示す。ピック アップ 101は、参照光および情報光を光情報記録媒体 151に照射し、光情報記録媒 体 151からの再生光を受けるためのものである。ピックアップ 101は、レーザ光源 103 、コリメータレンズ 105、ミラー 107、 DMD109、偏光ビームスプリッタ 111、リレーレ ンズ 113、 115、開口 127、ミラー 117、 4分の 1波長板 119、対物レンズ 121、リング マスク 123、光検出器 125を備えている。 [0007] FIG. 19 shows a configuration of a pickup of an optical information recording / reproducing apparatus using a DMD. The pick-up 101 is for irradiating the optical information recording medium 151 with reference light and information light and receiving the reproduction light from the optical information recording medium 151. Pickup 101 includes laser light source 103, collimator lens 105, mirror 107, DMD 109, polarization beam splitter 111, relay lens 113, 115, aperture 127, mirror 117, quarter wave plate 119, objective lens 121, ring mask 123, A photodetector 125 is provided.
[0008] 図 19の光情報記録再生装置によって情報を記録する場合、レーザ光源 103からレ 一ザ光を射出し、コリメータレンズ 105によって平行光線とし、ミラー 107によって DM D109に向かって反射される。 DMD109は、画素として複数の微小なミラーを有して おり、画素毎にミラーの傾斜角を変更できる。 DMD109の複数の画素に情報光用空 間変調パターンおよび参照光用空間変調パターンを表示すれば、その反射光 133 は、情報光用空間変調パターンおよび参照光用空間変調パターンによって空間的 に変調された情報光および参照光となる。 When information is recorded by the optical information recording / reproducing apparatus in FIG. 19, laser light is emitted from the laser light source 103, converted into parallel rays by the collimator lens 105, and reflected toward the DM D 109 by the mirror 107. The DMD 109 has a plurality of minute mirrors as pixels, and the mirror tilt angle can be changed for each pixel. If the information light spatial modulation pattern and the reference light spatial modulation pattern are displayed on a plurality of pixels of the DMD 109, the reflected light 133 is spatially modulated by the information light spatial modulation pattern and the reference light spatial modulation pattern. Information light and reference light.
[0009] 情報光および参照光は、偏光ビームスプリッタ 111を通過し、一対のリレーレンズ 1 13、 115によって対物レンズ 121の入射瞳面に結像するように伝搬される。その途中 、一対のリレーレンズ 113、 115の間の焦点面に配置された開口 127によって回折光
の一部が取り除かれ、ミラー 117によって対物レンズ 121に向けて反射され、 4分の 1 波長板 119を通過する。対物レンズ 121は、情報光および記録用参照光を光情報記 録媒体 151のホログラム記録層 153にお 、て干渉させ、ホログラフィを形成させる。 The information light and the reference light pass through the polarization beam splitter 111 and propagate so as to form an image on the entrance pupil plane of the objective lens 121 by the pair of relay lenses 113 and 115. On the way, the diffracted light is radiated by the aperture 127 disposed in the focal plane between the pair of relay lenses 113 and 115. Is removed by the mirror 117 and reflected by the mirror 117 toward the objective lens 121, and passes through the quarter-wave plate 119. The objective lens 121 causes information light and recording reference light to interfere with the hologram recording layer 153 of the optical information recording medium 151 to form holography.
[0010] また、図 19の光情報記録再生装置によって情報を再生する場合は、 DMD109に 再生用の参照光用空間変調パターンのみを表示して、再生用参照光を生成し、再 生用参照光を対物レンズ 121によって光情報記録媒体 151のホログラム記録層 153 に形成された干渉縞に照射する。干渉縞から再生された再生光と再生用参照光は、 光情報記録媒体 151の反射層 155によって反射され、逆方向に対物レンズ 121、 4 分の 1波長板 119、ミラー 117、一対のリレーレンズ 113、 115を経て伝搬される。ここ で、再生光と再生用参照光は、 4分の 1波長板 119を 2回通過することによって、偏光 力 S90° 変化しているので、偏光ビームスプリッタ 111によって光検出器 125に向かつ て反射され、リングマスク 123によって再生用参照光が取り除かれ、再生光が光検出 器 125に入射する。 In addition, when information is reproduced by the optical information recording / reproducing apparatus in FIG. 19, only the reference modulation spatial modulation pattern for reproduction is displayed on the DMD 109 to generate reproduction reference light, and reproduction reference Light is irradiated onto the interference fringes formed on the hologram recording layer 153 of the optical information recording medium 151 by the objective lens 121. The reproduction light and reproduction reference light reproduced from the interference fringes are reflected by the reflection layer 155 of the optical information recording medium 151, and in the reverse direction, the objective lens 121, the quarter-wave plate 119, the mirror 117, and a pair of relay lenses Propagated via 113 and 115. Here, since the reproduction light and the reproduction reference light change the polarization force S90 ° by passing through the quarter-wave plate 119 twice, the reproduction beam and the reproduction reference light are directed toward the photodetector 125 by the polarization beam splitter 111. The reflected reference light is removed by the ring mask 123, and the reproduced light is incident on the photodetector 125.
[0011] なお、干渉縞を記録するための光情報記録媒体 151は、 2枚の基板 151a、 151b 間に、ホログラム記録層 153および反射層 155が設けられている。ホログラム記録層 153は、情報光および参照光に対して感光性を有するモノマーが混入されており、 情報光および参照光が干渉して形成された干渉縞によってモノマーの一部が反応し てポリマーとなることで、屈折率等の光学特性を変化させ、干渉縞 (ホログラム)を記 録する。つまり、干渉縞を記録することによって、ホログラム記録層中のモノマーの一 部が消費される。また、記録された部分のモノマー濃度が減少すると、周囲からモノ マーが拡散移動する。 Note that the optical information recording medium 151 for recording interference fringes is provided with a hologram recording layer 153 and a reflection layer 155 between two substrates 151a and 151b. The hologram recording layer 153 is mixed with a monomer that is sensitive to information light and reference light, and a part of the monomer reacts with the polymer by interference fringes formed by interference of the information light and reference light. As a result, the optical characteristics such as the refractive index are changed, and interference fringes (holograms) are recorded. That is, by recording the interference fringes, a part of the monomer in the hologram recording layer is consumed. In addition, when the monomer concentration in the recorded portion decreases, the monomer diffuses from the surroundings.
[0012] 特許文献 1 :特開 2005— 32307号公報 Patent Document 1: Japanese Patent Application Laid-Open No. 2005-32307
発明の開示 Disclosure of the invention
発明が解決しょうとする課題 Problems to be solved by the invention
[0013] 図 20に従来の情報光用空間変調パターン 141の構成を示す。情報光用空間変調 パターン 141は、複数のブロック単位 143を配列させて形成されており、各ブロック単 位 143は基準マーク 147と一定量の 2次元パターン情報のシンボル単位 145とから 構成されている。
[0014] 2次元パターン情報のシンボル単位 145は、記録する情報を一定情報量の単位毎 に符号化して生成される。図 20においてシンボル単位 145は、記録する情報を 8ビッ ト毎に、 4 X 4の画素の中から 3つの画素をオンの画素 145a (図 20にお!/、ては網掛 けで示す)とし、オンの画素 145aの配置によって符号化したものである。 FIG. 20 shows a configuration of a conventional spatial modulation pattern 141 for information light. The spatial modulation pattern 141 for information light is formed by arranging a plurality of block units 143, and each block unit 143 is composed of a reference mark 147 and a symbol unit 145 of a certain amount of two-dimensional pattern information. . [0014] The symbol unit 145 of the two-dimensional pattern information is generated by encoding information to be recorded for each unit of a certain amount of information. In FIG. 20, symbol unit 145 is information to be recorded every 8 bits, and 3 pixels out of 4 × 4 pixels are turned on pixel 145a (indicated by shading in FIG. 20!). , Encoded according to the arrangement of the ON pixels 145a.
[0015] 基準マーク 147は、予め定められた形状の 2次元パターンであり、空間変調パター ン全体の位置、空間変調パターン全体の向き、空間変調パターンにおける 2次元パ ターン情報の各シンボル単位 145の位置または各シンボル単位の向き等の基準とな るものである。従来、 4 X 4の正方形状の画素を全てオン状態にして基準マーク 147 を表わしていた。図 20のシンボル単位 145は、 4 X 4の画素中 3つの画素しかオンの 画素とならないため、 4 X 4の画素がオンとなっていれば、シンボル単位 145と区別し て認識することができ、基準とすることができる。 [0015] The reference mark 147 is a two-dimensional pattern having a predetermined shape. The position of the entire spatial modulation pattern, the orientation of the entire spatial modulation pattern, and each symbol unit 145 of the two-dimensional pattern information in the spatial modulation pattern. This is a standard for the position or orientation of each symbol unit. Conventionally, the reference mark 147 is represented by turning on all the 4 × 4 square pixels. The symbol unit 145 in FIG. 20 can be recognized as distinguished from the symbol unit 145 if only 4 × 4 pixels are on because only three of the 4 × 4 pixels are on. Can be the standard.
[0016] 図 20においてブロック単位 143は、中心に 4 X 4のオン画素 145aを基準マーク 14 7として配置し、その周囲を 2画素分あけて、 6 X 6個のシンボル単位分の領域(24 X 24画素)を埋めるようにシンボル単位 145を 32個配置して!/ヽる。図 20にお!/ヽては、 情報光用空間変調パターン 141の中にブロック単位 143が最上段に 4個、 2段目に 6 個、 3〜6段目に各 8個、 7段目に 6個、 8段目に 4個配置されている。最上段の一番 左側のブロック単位 143a (点線で示す)だけは、中心に基準マーク 147のみ配置さ れた構成であり、基準マーク 147の周囲に 2次元パターン情報のシンボル単位が配 置されていない。このため、最上段の一番左側のブロック単位 143aは、他のブロック 単位と区別することができ、情報光用空間変調パターン 141自体の位置や向きの基 準とすることができる。例えば、再生時において、情報光用空間変調パターン 141を 検出すると、ブロック単位 143aが左上となるように位置合わせをし、その後、ブロック 単位 143aの右隣のブロック単位力も順に復号ィ匕して再生することができる。 In FIG. 20, a block unit 143 has a 4 × 4 on-pixel 145a at the center as a reference mark 147, and is surrounded by two pixels to obtain a region of 6 × 6 symbol units (24 Arrange 32 symbol units 145 to fill (24 pixels)! In Fig. 20! /, In the spatial modulation pattern for information light 141, there are 4 block units 143 at the top, 6 at the 2nd level, 8 at the 3rd to 6th levels, and 7th level. 6 on the 4th and 4 on the 8th stage. Only the leftmost block unit 143a (indicated by the dotted line) at the top is a configuration in which only the reference mark 147 is arranged at the center, and symbol units of 2D pattern information are arranged around the reference mark 147. Absent. Therefore, the leftmost block unit 143a in the uppermost stage can be distinguished from other block units, and can be used as a reference for the position and orientation of the spatial modulation pattern for information light 141 itself. For example, when the spatial modulation pattern 141 for information light is detected during reproduction, alignment is performed so that the block unit 143a is at the upper left, and then the block unit force on the right of the block unit 143a is also decoded and reproduced in order. can do.
[0017] 更に、各ブロック単位 143については、基準マーク 147を中心とした正方形状とな るようにシンボル単位が配置されて 、るので、基準マーク 147との相対的な位置を特 定することで、各シンボル単位 145の配置を特定することができる。 [0017] Furthermore, for each block unit 143, the symbol units are arranged so as to form a square shape with the reference mark 147 as the center. Therefore, the relative position with respect to the reference mark 147 must be specified. Thus, the arrangement of each symbol unit 145 can be specified.
[0018] 空間光変調器は、周期構造を持った微小な画素の集合体であるため、一種の回折 格子を形成する。回折格子は、回折格子の周期を a、回折光の角度を Θ 、入射光の
角度を 0 、回折次数を m (m=0、 ± 1、 ± 2)、光の波長をえとすると、Since the spatial light modulator is an aggregate of minute pixels having a periodic structure, it forms a kind of diffraction grating. The diffraction grating has a diffraction grating period of a, a diffraction light angle of Θ, If the angle is 0, the diffraction order is m (m = 0, ± 1, ± 2), and the light wavelength is
0 0
式丄: a isin 0 — sm Θ ) =m Formula 丄: a isin 0 — sm Θ) = m
d 0 d 0
の関係を満たす。 Satisfy the relationship.
[0019] 図 19の光情報記録再生装置においては、ミラー 107力らの光 131は、 DMD109 に対して入射角 0 を有して入射し、 DMD109から垂直(0 =0° )に射出するよう In the optical information recording / reproducing apparatus of FIG. 19, light 131 from the force of the mirror 107 is incident on the DMD 109 with an incident angle of 0 and is emitted perpendicularly (0 = 0 °) from the DMD 109.
0 1 0 1
に配置されている。この関係を図に示すと、図 21のようになる。 DMD109の画素 13 5の間隔が回折格子の周期 aとなり、回折光 132の角度 Θ は、画素 135の間隔 a、入 d Is arranged. Figure 21 shows this relationship. The interval between the pixels 13 5 of the DMD 109 is the period a of the diffraction grating, and the angle Θ of the diffracted light 132 is the interval a between the pixels 135 and d
射光 131の波長えおよび入射角 Θ 力 式 1によって決まり、 DMD109の画素 135 The wavelength of incident light 131 and the angle of incidence Θ force
0 0
の傾斜角 Ψには依存しない。他方、反射光 133 (図 21においては— 3次の回折光と 重なっている)の出射角 0 は、入射光 131の入射角 0 および DMD109の画素 13 It does not depend on the tilt angle Ψ. On the other hand, the output angle 0 of the reflected light 133 (in FIG. 21—overlapping the third-order diffracted light) is 0 for the incident light 131 and 13 for the DMD 109.
1 0 Ten
5の傾斜角度 Ψから From an inclination angle Ψ of 5
式 2 : θ = θ - 2Ψ Equation 2: θ = θ-2Ψ
によって決まる。図 21においては、反射光 133の出射角 0 は 0° であるから出射角 It depends on. In FIG. 21, since the exit angle 0 of the reflected light 133 is 0 °, the exit angle is
1 1
Θ を示していない。 Θ is not shown.
1 1
[0020] なお、図 21は、空間光変調器 109の全ての画素 135をオン状態とした場合であり、 画素 135の間隔 aが回折格子の周期となっている。ところが、情報光用空間変調バタ ーンゃ参照光用空間変調パターンが表示された空間光変調器の場合、情報光用空 間変調パターンや参照光用空間変調パターンは、オン画素とオフ画素が組み合わさ れて形成されているから、様々な周期成分を有し、回折格子の周期としては、隣接す る画素の間隔 aだけではない。しかし、空間光変調器 109において表示されるパター ンは、画素 135を基準の単位要素として構成されるため、回折格子の周期としては、 画素の間隔 aが最小となる。そこで、全ての画素 135をオン状態とした状態の空間周 波数をその空間光変調器における基本空間周波数と呼ぶ。 FIG. 21 shows a case where all the pixels 135 of the spatial light modulator 109 are turned on, and the interval “a” of the pixels 135 is the period of the diffraction grating. However, in the case of a spatial light modulator displaying a spatial modulation pattern for information light or a spatial modulation pattern for reference light, the spatial modulation pattern for information light or the spatial modulation pattern for reference light has an on pixel and an off pixel. Since they are formed in combination, they have various periodic components, and the period of the diffraction grating is not limited to the interval a between adjacent pixels. However, since the pattern displayed in the spatial light modulator 109 is configured with the pixel 135 as a reference unit element, the pixel interval “a” is minimized as the period of the diffraction grating. Therefore, the spatial frequency with all the pixels 135 turned on is called the fundamental spatial frequency in the spatial light modulator.
[0021] 従来では、 DMD109によって反射されて生成される情報光、記録用参照光および 再生用参照光の光軸(Θ )は、回折光 132の内の一部の進行方向(0 )と一致する Conventionally, the optical axes (Θ) of the information light, the recording reference light, and the reproduction reference light reflected and generated by the DMD 109 coincide with the traveling direction (0) of a part of the diffracted light 132. Do
1 d 1 d
ように定められていた(特許文献 1の段落 0029)。つまり、 a (sin 0 - sin 0 ) =m (Patent Document 1, paragraph 0029). That is, a (sin 0-sin 0) = m
1 0 を満たし、入射角 Θ がー a' sin 0 =πι λとなるように構成されていたのである。 It was constructed so that 1 0 was satisfied and the incident angle Θ was −a ′ sin 0 = πι λ.
0 0 0 0
[0022] なお、 SLMとして透過型の液晶表示装置等を使用した場合は、 SLMに対して光を
垂直(0 =0° )に入射させて、垂直(0 =0° )に出射した光を利用していたため、[0022] When a transmissive liquid crystal display device or the like is used as the SLM, light is emitted to the SLM. Because we used light that was incident vertically (0 = 0 °) and emitted vertically (0 = 0 °),
0 1 0 1
入射角 =出射角であり、 0次の回折光と光軸が一致して!/、た。 The incident angle is equal to the outgoing angle, and the 0th-order diffracted light coincides with the optical axis! /.
[0023] 本発明者は、特願 2005— 312513号において、かかる従来の光情報記録再生装 置に対して、空間光変調器から対物レンズに向かう情報光の光軸が、空間光変調器 によって回折される m次 (m=0, ± 1, ± 2· ··)の回折光と一致しないように構成した 光情報記録装置を提案した。情報光の光軸が回折光と一致しないように構成した場 合は、対物レンズによってフーリエ変換された空間光変調器の基本空間周波数によ つて発生する輝点を最も光強度の強 、領域に配置させることができ、干渉縞の強度 を強くすることができ、ホログラムサイズを小さくすることが可能となる。 [0023] In the Japanese Patent Application No. 2005-312513, the present inventor compared the optical information recording / reproducing apparatus with the optical axis of information light from the spatial light modulator toward the objective lens by the spatial light modulator. We proposed an optical information recording device that was constructed so as not to match the diffracted light of the mth order (m = 0, ± 1, ± 2 ···). When the optical axis of the information light is configured so as not to coincide with the diffracted light, the bright spot generated by the fundamental spatial frequency of the spatial light modulator Fourier-transformed by the objective lens is placed in the region with the highest light intensity. The interference fringes can be strengthened and the hologram size can be reduced.
[0024] 本発明は、かかる情報光の光軸が回折光と一致しな!、ように構成した場合にお!ヽ て、更にホログラムサイズを小さくすることを可能にし、記録密度を高めることが可能 な光情報記録方法及び記録媒体を提供することを課題とする。また、本発明は、従 来よりも記録再生の信頼性を高めることが可能な光情報記録方法及び記録媒体を提 供することを課題とする。 The present invention makes it possible to further reduce the hologram size and increase the recording density when the optical axis of the information light does not coincide with the diffracted light! It is an object of the present invention to provide a possible optical information recording method and recording medium. It is another object of the present invention to provide an optical information recording method and a recording medium that can improve the reliability of recording and reproduction more than ever.
課題を解決するための手段 Means for solving the problem
[0025] 以上のような課題を解決するため、本発明の光情報記録方法は、記録用参照光と 、複数の画素を有する空間光変調器に表示された情報光用空間変調パターンによ つて空間的に変調された情報光とを対物レンズによって記録媒体に対して収束する ように照射して前記記録媒体のホログラム記録層における前記記録用参照光と前記 情報光との干渉縞を記録する光情報記録方法にお!、て、前記空間光変調器から前 記対物レンズに向力う前記情報光の光軸力 前記空間光変調器によって回折される m次 (m=0, ± 1, ± 2· ··)の回折光と一致せず、前記情報光用空間変調パターンは 複数の基準マークを含み、前記基準マークの領域内における空間周波数が、前記 空間光変調器の基本空間周波数よりも小さい空間周波数を含むことを特徴とする。 In order to solve the above-described problems, the optical information recording method of the present invention uses a recording reference light and a spatial modulation pattern for information light displayed on a spatial light modulator having a plurality of pixels. Light for recording interference fringes between the recording reference light and the information light in the hologram recording layer of the recording medium by irradiating the spatially modulated information light with the objective lens so as to converge on the recording medium In the information recording method, the optical axial force of the information light directed from the spatial light modulator to the objective lens is m-order (m = 0, ± 1, ± diffracted by the spatial light modulator. 2)), the information light spatial modulation pattern includes a plurality of reference marks, and the spatial frequency in the area of the reference marks is higher than the basic spatial frequency of the spatial light modulator. It includes a small spatial frequency.
[0026] 更に、上記光情報記録方法において、前記情報光の光軸の方向は、 (m+O. 2) 次乃至 (m+O. 8)次の回折光の進行方向の範囲内であることが好ましい。また、前 記空間光変調器は、前記複数の画素が格子状に配置されており、前記情報光の光 軸の方向は、前記複数の画素による格子の対角方向についての約 (m+O. 5)次の
回折光の進行方向と一致することが好ましい。 [0026] Further, in the optical information recording method, the direction of the optical axis of the information light is within the range of the traveling direction of the (m + O. 2) order to (m + O. 8) order diffracted light. It is preferable. Further, in the spatial light modulator, the plurality of pixels are arranged in a lattice shape, and the optical axis direction of the information light is approximately (m + O) with respect to the diagonal direction of the lattice of the plurality of pixels. 5) Next It is preferable to coincide with the traveling direction of the diffracted light.
[0027] 更に、上記光情報記録方法において、前記基準マークの領域内における空間周 波数が、前記空間光変調器の基本空間周波数の半分の空間周波数を含むことが好 ましい。また、前記基準マークは属性の異なる画素を交互に配置したパターンを含む ことが好ましい。 Furthermore, in the optical information recording method, it is preferable that the spatial frequency in the area of the reference mark includes a spatial frequency that is half of the fundamental spatial frequency of the spatial light modulator. The reference mark preferably includes a pattern in which pixels having different attributes are alternately arranged.
[0028] 更に、上記光情報記録方法において、前記情報光の光軸の方向は、前記空間光 変調器に対して垂直であることが好まし 、。 Furthermore, in the optical information recording method, it is preferable that the direction of the optical axis of the information light is perpendicular to the spatial light modulator.
[0029] また、本発明の記録媒体は、上記光情報記録方法によってホログラム記録層に干 渉縞が記録されたことを特徴とするものである。 [0029] Further, the recording medium of the present invention is characterized in that interference fringes are recorded on the hologram recording layer by the optical information recording method.
発明の効果 The invention's effect
[0030] 本発明の光情報記録方法では、対物レンズへ向かう出射光の光軸を m次の回折 光とずらすことによって、最も強度の強い領域に複数の基本空間周波数による輝点 を配置させることができ、干渉縞の強度を強くすることができる。また、画素の反射面 の傾斜角度の誤差等によって、空間光変調器からの出射角 Θ [0030] In the optical information recording method of the present invention, bright spots with a plurality of fundamental spatial frequencies are arranged in the strongest region by shifting the optical axis of the outgoing light toward the objective lens from the m-th order diffracted light. And the intensity of the interference fringes can be increased. In addition, the output angle Θ from the spatial light modulator is caused by errors in the tilt angle of the reflective surface of the pixel.
1にバラツキが生じて、 形状成分パターンのフーリエ面における位置がずれたとしても、複数の基本空間周 波数による輝点が存在するため、ホログラムの記録領域内において強い強度を保つ ことができ、信頼性が向上する。 Even if variations occur in 1 and the position of the shape component pattern in the Fourier plane deviates, there are bright spots with multiple fundamental spatial frequencies, so strong intensity can be maintained within the hologram recording area, and reliability can be maintained. Improves.
[0031] 更に、従来では、中心に非常に強い光強度の領域が局在化するため、光情報記録 媒体のホログラム記録層中におけるモノマー濃度が部分的に枯渴してしま 、多重記 録の妨げとなることもあったが、本発明の光情報記録方法では、光強度の強い領域 に複数の輝点を配置させているので、ホログラムの記録領域内における光強度分布 を従来に比較すれば平均化することができる。この結果、モノマー濃度も平均的に減 少し、多重記録特性を向上できるので、記録容量を増やすことができる。 [0031] Further, conventionally, since a region of very strong light intensity is localized at the center, the monomer concentration in the hologram recording layer of the optical information recording medium is partially depleted. In some cases, the optical information recording method of the present invention has a plurality of bright spots arranged in a region where the light intensity is high. Therefore, if the light intensity distribution in the hologram recording region is compared with the conventional method. Can be averaged. As a result, the monomer concentration also decreases on average, and the multiple recording characteristics can be improved, so that the recording capacity can be increased.
[0032] また、本発明の光情報記録方法にお!、ては、光軸の近傍に位置する 4つの輝点に よって全ての空間周波数特性が示されるため、それら 4つの輝点を含む大きさまでホ ログラムの記録領域を小さくすることができる。よって、一つ当たりのホログラムサイズ を小さくできるので、その分、多くのホログラムを記録することができ、記録容量を増や すことができる。
[0033] 力!]えて、本発明の光情報記録方法では、情報光用空間変調パターンが複数の基 準マークを含み、基準マークの領域内における空間周波数が、空間光変調器の基 本空間周波数よりも小さい空間周波数を含んでいるので、基準マークをフーリエ変換 することによって発生する輝点が 4つの基本空間周波数による輝点の内部に存在し、 ホログラムサイズを小さくしても、基準マークが消えず信頼性を向上させることができ る。そして、ホログラムの大きさをより小さくすることが可能となり、記録容量を向上させ ることち可會となる。 [0032] In addition, in the optical information recording method of the present invention, all the spatial frequency characteristics are indicated by four bright spots located in the vicinity of the optical axis. In this way, the recording area of the hologram can be reduced. Accordingly, the size of each hologram can be reduced, so that more holograms can be recorded and the recording capacity can be increased. [0033] Power! In the optical information recording method of the present invention, the spatial modulation pattern for information light includes a plurality of reference marks, and the spatial frequency in the area of the reference mark is smaller than the basic spatial frequency of the spatial light modulator. Since the frequency is included, the bright spot generated by Fourier transform of the reference mark exists inside the bright spot with the four basic spatial frequencies, and even if the hologram size is reduced, the reference mark does not disappear and reliability is improved. Can be improved. Further, the size of the hologram can be further reduced, and it is possible to improve the recording capacity.
図面の簡単な説明 Brief Description of Drawings
[0034] [図 1]本発明の空間光変調器における光の関係を説明する図 [0034] FIG. 1 is a diagram for explaining the relationship of light in the spatial light modulator of the present invention.
[図 2]従来の光情報記録再生装置におけるフーリエ変換像 [Figure 2] Fourier transform image in a conventional optical information recording / reproducing apparatus
[図 3]本発明の光情報記録再生装置におけるフーリエ変換像 FIG. 3 is a Fourier transform image in the optical information recording / reproducing apparatus of the present invention.
[図 4]1次元のフーリエ変換波形によってフーリエ変換の合成を説明する図 [Fig.4] Diagram explaining synthesis of Fourier transform by one-dimensional Fourier transform waveform
[図 5]本発明を実施できる DMDの一条件を示す表 FIG. 5 is a table showing one condition of DMD that can implement the present invention.
[図 6]比較例におけるフーリエ変換像 [Figure 6] Fourier transform image in comparative example
[図 7]本発明におけるフーリエ変換像 FIG. 7: Fourier transform image in the present invention
[図 8]本発明におけるフーリエ変換像 [Fig. 8] Fourier transform image in the present invention
[図 9]本発明におけるフーリエ変換像 [Fig. 9] Fourier transform image in the present invention.
[図 10]本発明の透過型の空間光変調器における光の関係を説明する図 FIG. 10 is a diagram for explaining the relationship of light in the transmissive spatial light modulator of the present invention.
[図 11] (A)乃至 (C)は空間変調パターンと周期性 tの関係を説明するための図 [FIG. 11] (A) to (C) are diagrams for explaining the relationship between the spatial modulation pattern and the periodicity t.
[図 12] (A)及び (B)は各空間変調パターンにおけるフーリエ変換像を示す図 [FIG. 12] (A) and (B) are diagrams showing Fourier transform images in each spatial modulation pattern.
[図 13] (A)は従来の(B)は本発明の一実施形態の空間光変調パターンを示す図 FIG. 13 (A) is a diagram showing a conventional spatial light modulation pattern according to an embodiment of the present invention (B).
[図 14]従来の方法で記録されたホログラムを再生した像 [Fig.14] Image reproduced from hologram recorded by conventional method
[図 15]本発明の光情報記録方法で記録されたホログラムを再生した像 FIG. 15 is an image obtained by reproducing a hologram recorded by the optical information recording method of the present invention.
[図 16]開口の大きさと再生した基準マークのビットエラーレートとの関係を示す図 [Fig.16] Diagram showing the relationship between the aperture size and the bit error rate of the reproduced reference mark
[図 17] (A)乃至 (H)は本発明の基準マークの他の実施形態を示す図 [FIG. 17] (A) to (H) are diagrams showing another embodiment of the fiducial mark of the present invention.
[図 18]本発明の光情報記録再生装置のピックアップの構成を示す概略構成図 FIG. 18 is a schematic configuration diagram showing a configuration of a pickup of the optical information recording / reproducing apparatus of the present invention.
[図 19]従来の光情報記録再生装置のピックアップの構成を示す概略構成図 FIG. 19 is a schematic configuration diagram showing a configuration of a pickup of a conventional optical information recording / reproducing apparatus.
[図 20]従来の空間光変調器における光の関係を説明する図
[図 21]従来の空間光変調器における光の関係を説明する図 FIG. 20 is a diagram for explaining the relationship of light in a conventional spatial light modulator. FIG. 21 is a diagram for explaining the relationship of light in a conventional spatial light modulator.
発明を実施するための最良の形態 BEST MODE FOR CARRYING OUT THE INVENTION
[0035] まず、図 1を用いて、本発明の空間光変調器 11における入射光 21、出射光 22およ び回折光 23の関係を説明する。本発明の光情報記録再生装置は、記録時には、空 間光変調器 11に情報光用空間変調パターンおよび記録用参照光用空間変調バタ ーンを表示して、光を空間的に変調して情報光および記録用参照光を生成する。な お、記録用参照光は空間的に変調しなくてもよぐその場合は、空間光変調器 11に 情報光用空間変調パターンのみを表示すればよい。そして、情報光と記録用参照光 は、対物レンズ 13によって記録媒体(図示せず)に対して収束するように照射され、 記録媒体のホログラム記録層にお 、て干渉することで、情報光と記録用参照光の干 渉縞がホログラム記録層に記録される。次に、空間的に変調した記録用参照光を利 用して記録した干渉縞を再生する時には、空間光変調器 11に記録時にぉ 、て記録 用参照光を生成した記録用参照光用空間変調パターンと同じ再生用参照光用空間 変調パターンを表示して、光を空間的に変調して再生用参照光を生成する。再生用 参照光は、対物レンズ 13によって記録媒体に対して収束するように照射され、記録 媒体のホログラム記録層に記録された干渉縞と干渉して再生光を発生させる。発生し た再生光は、対物レンズ 13を含む光学系によって伝搬され、光検出器によってその 空間変調パターンが検出される。 [0035] First, the relationship among incident light 21, emitted light 22, and diffracted light 23 in the spatial light modulator 11 of the present invention will be described with reference to FIG. The optical information recording / reproducing apparatus of the present invention displays the spatial modulation pattern for information light and the spatial modulation pattern for reference light for recording on the spatial light modulator 11 during recording to spatially modulate the light. Information light and recording reference light are generated. If the recording reference light does not have to be spatially modulated, only the information light spatial modulation pattern may be displayed on the spatial light modulator 11. Then, the information light and the recording reference light are irradiated so as to converge on the recording medium (not shown) by the objective lens 13, and interfere with the hologram recording layer of the recording medium. Interference fringes of the recording reference beam are recorded on the hologram recording layer. Next, when reproducing the interference fringes recorded using the spatially modulated reference light for recording, the spatial light modulator 11 generates the reference light for recording after recording in the spatial light modulator 11. The reproduction reference light spatial modulation pattern that is the same as the modulation pattern is displayed, and the light is spatially modulated to generate reproduction reference light. The reproduction reference light is irradiated by the objective lens 13 so as to converge on the recording medium, and interferes with interference fringes recorded on the hologram recording layer of the recording medium to generate reproduction light. The generated reproduction light is propagated by the optical system including the objective lens 13, and the spatial modulation pattern is detected by the photodetector.
[0036] 本発明においては、空間光変調器 11から対物レンズ 13に向かう出射光 22 (情報 光、記録用参照光または再生用参照光)の光軸が、空間光変調器 11によって回折さ れる m次 (m=0, ± 1, ± 2· · ·)の回折光 23と一致しないように構成されている。これ は、出射光 22が m次と (m+ 1)次の回折光 23の間に位置することを意味する。図 1 においては、—1次の回折光と 0次の回折光の間に出射光 22が位置している。また、 空間光変調器 11に入射する光 21の入射角を 0 、空間光変調器 11から出射される In the present invention, the optical axis of the outgoing light 22 (information light, recording reference light or reproduction reference light) directed from the spatial light modulator 11 toward the objective lens 13 is diffracted by the spatial light modulator 11. It is configured not to match the diffracted light 23 of the mth order (m = 0, ± 1, ± 2 ···). This means that the emitted light 22 is located between the m-th order and the (m + 1) -th order diffracted light 23. In FIG. 1, the outgoing light 22 is located between the first-order diffracted light and the zeroth-order diffracted light. Further, the incident angle of the light 21 incident on the spatial light modulator 11 is 0, and is emitted from the spatial light modulator 11.
0 0
光 22の出射角を Θ 、光の波長をえ、空間光変調器 11における複数の画素 12の周 The emission angle of the light 22 is Θ, the wavelength of the light is obtained, and the circumference of the plurality of pixels 12 in the spatial light modulator 11 is obtained.
1 1
期を a、回折光 23の回折次数を m (m=0, ± 1, ± 2· · ·)とすると、 If the period is a and the diffraction order of the diffracted light 23 is m (m = 0, ± 1, ± 2 ···),
式 3 : m 7= a (sm Θ — sm θ ) Equation 3: m 7 = a (sm Θ — sm θ)
1 0 Ten
の関係式を満たすように装置を構成する。なお、図 1においては、反射型の空間光変
調器で例示したが、透過型の空間光変調器であっても同じである。 The apparatus is configured to satisfy the following relational expression. In FIG. 1, the reflection-type spatial light modulation Although it is exemplified by the tuner, the same applies to a transmissive spatial light modulator.
[0037] ここで、出射光 22の光軸の方向は、(m+O. 2)次乃至 (m+O. 8)次の回折光 23 の進行方向の範囲内であることが好ましぐ特に約 (m+O. 5)次の回折光 23の進行 方向であることが好ましい。つまり、 (m+O. 2) λ≤a (sin 0 -sin 0 )≤(m+0. 8) Here, the direction of the optical axis of the emitted light 22 is preferably within the range of the traveling direction of the (m + O. 2) th to (m + O.8) th diffracted light 23. In particular, the traveling direction of the diffracted light 23 of about (m + O.5) order is preferable. That is, (m + O. 2) λ≤a (sin 0 -sin 0) ≤ (m + 0. 8)
1 0 Ten
の関係式を満たすことが好ましぐ特に約(m+O. 5) l =a (sin 0 sin 0 )の関係 It is particularly preferable to satisfy the relation of (m + O. 5) l = a (sin 0 sin 0)
1 0 式を満たすことがより好まし 、。 It is more preferable to satisfy 1 0 expression.
[0038] また、図 1においては、出射光 22の角度 Θ を分力りやすくするため、斜めに射出さ [0038] Also, in FIG. 1, the angle Θ of the emitted light 22 is emitted obliquely so that it can be easily divided.
1 1
せているが、対物レンズ 13によって 2次元パターン情報をフーリエ変換する際に、 2 次元パターン情報を表示する空間光変調器 11の表示面が対物レンズ 13の入射瞳 面 (光軸に対して垂直)と平行となることが好ましいので、出射角 0 は 0° であること、 However, when the two-dimensional pattern information is Fourier transformed by the objective lens 13, the display surface of the spatial light modulator 11 that displays the two-dimensional pattern information is the entrance pupil plane of the objective lens 13 (perpendicular to the optical axis). ), The exit angle 0 is 0 °,
1 1
つまり出射光 22の光軸が空間光変調器 11に対して垂直となるように構成することが 好ましい。この場合、 sin Θ =0となるので、式 3は、 m ≠— a' sin Θ となり、入射角 That is, it is preferable to configure the optical axis of the emitted light 22 to be perpendicular to the spatial light modulator 11. In this case, since sin Θ = 0, Equation 3 becomes m ≠ — a 'sin Θ and the incident angle
1 0 Ten
Θ としては、 (m+0. 2) λ≤-a- sin 0 ≤ (m+0. 8)の関係式を満たすことが好ま As Θ, it is preferable to satisfy the relation (m + 0.2) λ≤-a-sin 0 ≤ (m + 0.8)
0 0 0 0
しぐ特に約 (m+0. 5) λ =— a' sin Θ の関係式を満たすことがより好ましい。 In particular, it is more preferable to satisfy the relational expression of about (m + 0.5) λ = —a 'sin Θ.
0 0
[0039] 更に、反射型の画素を有する DMDの場合、画素の反射面の角度を Ψとすると、出 射角 0 = 0 —2Ψとなるので、空間光変調器 11の画素 12の周期 aおよび傾斜角 Ψ [0039] Further, in the case of a DMD having a reflection type pixel, if the angle of the reflection surface of the pixel is Ψ, the emission angle is 0 = 0−2Ψ. Tilt angle Ψ
1 0 Ten
が m ≠— a' sin2¥の関係式を満たすと、出射光 22の光軸が、空間光変調器 11に 対して垂直となり、且つ回折光と一致しない構成となる。空間光変調器 11の画素の 周期 aおよび傾斜角 Ψは、(m+0. 2) l≤-a- sin2¥≤(m+0. 8)の関係式を満 たすことが好ましぐ特に約 (m+0. 5) λ =— a' sin2¥の関係式を満たすことがより 好ましい。 Satisfies the relational expression m ≠ — a ′ sin2 ¥, the optical axis of the outgoing light 22 is perpendicular to the spatial light modulator 11 and does not coincide with the diffracted light. It is preferable that the period a and the inclination angle Ψ of the pixel of the spatial light modulator 11 satisfy the relational expression (m + 0.2) l≤-a-sin2 ¥ ≤ (m + 0.8) In particular, it is more preferable to satisfy the relational expression of about (m + 0.5) λ = — a 'sin2 ¥.
[0040] 図 2は、出射光の角度 0 が m次の回折光と一致する従来の光情報記録再生装置 FIG. 2 shows a conventional optical information recording / reproducing apparatus in which the angle 0 of the emitted light coincides with the mth-order diffracted light.
1 1
におけるフーリエ変換像を示し、図 3は、出射光の角度 0 が m次の回折光と一致し Fig. 3 shows that the angle 0 of the emitted light coincides with the mth-order diffracted light.
1 1
ない本発明の光情報記録再生装置におけるフーリエ変換像を示す。 4 shows a Fourier transform image in the optical information recording / reproducing apparatus according to the present invention.
[0041] 図 2の左上に示すように、格子状に配列した複数の画素 135を有する空間光変調 器 109の全ての画素 135をオン状態とした場合、対物レンズによってフーリエ変換さ れると、同図右上に示すようなパターン 137に変換される。図 2において、空間光変 調器 109の全ての画素 135がオン状態であるから、空間光変調器 109に表示された
ノターンは、基本空間周波数からなるパターンであり、そのフーリエ変換されたバタ ーン 137は、基本空間周波数の周波数成分を示すものとなる。パターン 137におけ る輝点 138を「基本空間周波数による輝点」と呼ぶ。 [0041] As shown in the upper left of FIG. 2, when all the pixels 135 of the spatial light modulator 109 having a plurality of pixels 135 arranged in a lattice shape are turned on, the Fourier transform is performed by the objective lens. It is converted to pattern 137 as shown in the upper right of the figure. In FIG. 2, since all the pixels 135 of the spatial light modulator 109 are on, they are displayed on the spatial light modulator 109. A no-turn is a pattern composed of a basic spatial frequency, and its Fourier-transformed pattern 137 indicates a frequency component of the basic spatial frequency. The bright spot 138 in the pattern 137 is called “the bright spot by the fundamental spatial frequency”.
[0042] 各基本空間周波数による輝点 138は、それぞれの方向における m次の回折光であ り、各輝点 138の位置は、前述した式 1 : a (sin 0 - sin 0 ) =m における回折角 0 d 0 [0042] The bright spot 138 by each fundamental spatial frequency is m-th order diffracted light in each direction, and the position of each bright spot 138 is in the above-described formula 1: a (sin 0-sin 0) = m Diffraction angle 0 d 0
によって求められる。図 2においては、対物レンズへ向力う出射光の光軸が m次の回 d Sought by. In Fig. 2, the optical axis of the outgoing light directed toward the objective lens
折光と一致するので、光軸上(中心)に基本空間周波数による輝点 138が位置する。 Since it coincides with the folded light, the bright spot 138 based on the fundamental spatial frequency is located on the optical axis (center).
[0043] 空間光変調器 109によって空間的に変調される光のフーリエ変換を解析するにあ たって、空間光変調器 109の成分は、画素 135の配置に起因する配置成分 135aと 画素 135の形状に起因する形状成分 135bとに分解することができる。なお、図 2お よび図 3において配置成分と形状成分の間の「*」はコンボリューシヨンの演算記号 である。 [0043] In analyzing the Fourier transform of the light spatially modulated by the spatial light modulator 109, the components of the spatial light modulator 109 are the arrangement component 135a resulting from the arrangement of the pixel 135 and the shape of the pixel 135. It can be decomposed into the shape component 135b caused by In FIGS. 2 and 3, the “*” between the arrangement component and the shape component is a convolution calculation symbol.
[0044] 配置成分 135aは、フーリエ変換すると、配置成分 135aと相似形に配置された輝点 138aを有する配置成分パターン 137aが得られ、形状成分 135bは、フーリエ変換す ると、画素の形状に起因した強度分布を有する形状成分パターン 137bとなる。図 2 では、正方形状の画素 135に対する形状成分パターン 137bが示されている。形状 成分パターン 137bの強度分布は、中心部分に最も強度の強い領域が位置し、そこ 力も画素 135の正方形の各辺に対面する方向(図 2の上下左右)に周期的に配置さ れた領域では中心部分力も遠ざかるにつれて徐々に強度が弱くなる。また、画素 13 5の対角方向(図 2の斜め方向)については、中心部分の近傍のみに領域が存在し、 その領域の光強度も中心部分力 遠ざ力るにつれて徐々に弱くなる。形状成分バタ ーン 137bの位置は、前述した式 2 : θ = θ —2Ψにおける出射角 Θ によって求め The arrangement component 135a is subjected to Fourier transform to obtain an arrangement component pattern 137a having a bright spot 138a arranged in a similar shape to the arrangement component 135a, and the shape component 135b is converted to a pixel shape after Fourier transformation. The resulting shape component pattern 137b has an intensity distribution. In FIG. 2, a shape component pattern 137b for a square pixel 135 is shown. In the intensity distribution of the shape component pattern 137b, the region with the strongest intensity is located in the center, and the force is also periodically arranged in the direction facing each side of the square of the pixel 135 (up, down, left and right in Fig. 2). Then, the strength gradually weakens as the central force increases. In addition, in the diagonal direction of pixel 135 (oblique direction in FIG. 2), there is a region only in the vicinity of the central portion, and the light intensity in that region gradually decreases as the central partial force increases. The position of the shape component pattern 137b is determined by the exit angle Θ in Equation 2 above: θ = θ −2Ψ.
1 0 1 1 0 1
られる。 It is done.
[0045] パターン 137は、配置成分パターン 137aと形状成分パターン 137bとを重ね合わ せて強度を掛け合わせたパターンである。この点をまずは 1次元のフーリエ変換波形 で説明すると、図 4に示すように、形状成分に対応する矩形波をフーリエ変換した形 状成分パターン 41に対し、配置成分に対応する周期的なピークを有する配置成分 パターン 42を重ね合わせて強度を掛け合わせると合成パターン 44が得られる。つま
り、配置成分パターン 42のピーク位置における形状成分パターン 41の強度が合成 ノターン 44となる。合成パターン 44において、点線で形状成分パターン 41を示して いる。合成パターン 44は、形状成分パターン 41の中心と配置成分パターン 42の中 心とがー致している点で、従来の光情報記録再生装置におけるフーリエ変換パター ン 137に相当する。 The pattern 137 is a pattern in which the arrangement component pattern 137a and the shape component pattern 137b are overlapped and multiplied by the intensity. This point will first be explained using a one-dimensional Fourier transform waveform. As shown in FIG. 4, a periodic peak corresponding to the arrangement component is shown in the shape component pattern 41 obtained by Fourier transforming the rectangular wave corresponding to the shape component. The composite pattern 44 is obtained by superposing the arrangement component patterns 42 and multiplying them by the intensity. Tsuma Thus, the intensity of the shape component pattern 41 at the peak position of the arrangement component pattern 42 becomes the composite pattern 44. In the composite pattern 44, the shape component pattern 41 is indicated by a dotted line. The synthesized pattern 44 corresponds to the Fourier transform pattern 137 in the conventional optical information recording / reproducing apparatus in that the center of the shape component pattern 41 and the center of the arrangement component pattern 42 are aligned.
[0046] 図 2においては、出射光の角度 0 が m次の回折光の角度 0 と一致するので、配 In FIG. 2, the angle 0 of the emitted light matches the angle 0 of the mth-order diffracted light.
1 d 1 d
置成分パターン 137aの中心と、形状成分パターン 137bの中心とがー致する。フーリ ェ変換パターン 137は、中心に位置する m次の回折光において最も光強度が強ぐ そこから上下左右の(m± l、 2· ··)次の各輝点 138については、中心から遠ざかる( mとの差が大きくなる)につれて強度が弱まる。また、対角方向(図 2の斜め方向)に ついては、中心部分の近傍しか形状成分パターン 137bが存在しないため、フーリエ 変換パターン 137の (m± l、 2· ··)次の各輝点も中心部分の近傍のみにしか存在せ ず、それらの輝点も中心力も遠ざかる (mとの差が大きくなる)につれて強度が弱まる The center of the arrangement component pattern 137a and the center of the shape component pattern 137b coincide. The Fourier transform pattern 137 has the strongest light intensity in the m-th order diffracted light located at the center. From there, the next bright spot 138 (m ± l, 2...) Is moved away from the center. The strength decreases as the difference from m increases. In addition, in the diagonal direction (diagonal direction in Fig. 2), the shape component pattern 137b exists only in the vicinity of the center portion, so each bright spot of the Fourier transform pattern 137 (m ± l, 2 ...) is It exists only in the vicinity of the central part, and the intensity decreases as the luminescent spot and central force move away (the difference from m increases).
[0047] 次に、図 3の左上に示すように、本発明の記録再生方法において、格子状に配列し た複数の画素 12を有する空間光変調器 11の全ての画素 12をオン状態とした場合、 対物レンズによってフーリエ変換されると、同図右上に示すようなパターン 31に変換 される。なお、図 3では、空間光変調器 11が光軸を中心として 45° 回転されているが 、これは DMDの各画素 12が図 2における縦方向の対角線を回転軸 14として回動す る構成となっており、回転軸を装置において垂直に配置したためである。空間光変調 器 11を回転させると、そのフーリエ変換されたパターン 31も回転する力 パターン 31 の形状それ自体に変化はなぐ図 3のパターン 31も基本空間周波数の周波数成分 を示すものであり、パターン 31における輝点 33も基本空間周波数による輝点である Next, as shown in the upper left of FIG. 3, in the recording / reproducing method of the present invention, all the pixels 12 of the spatial light modulator 11 having a plurality of pixels 12 arranged in a grid are turned on. In this case, when the Fourier transform is performed by the objective lens, the pattern 31 is transformed as shown in the upper right of the figure. In FIG. 3, the spatial light modulator 11 is rotated by 45 ° about the optical axis. This is a configuration in which each pixel 12 of the DMD rotates about the vertical diagonal line in FIG. This is because the rotating shaft is arranged vertically in the apparatus. When the spatial light modulator 11 is rotated, the Fourier transformed pattern 31 also rotates. The shape of the pattern 31 itself does not change. Pattern 31 in Fig. 3 also shows the frequency components of the fundamental spatial frequency. The bright spot 33 at 31 is also a bright spot by the fundamental spatial frequency.
[0048] 図 3の空間光変調器 11も、図 2の時と同様に、画素 12の配置に起因する配置成分 12aと画素 12の形状に起因する形状成分 12bとに分解することができる。配置成分 1 2aは、フーリエ変換すると、配置成分 12aと相似形に配置された輝点 33aを有する配 置成分パターン 3 laが得られ、形状成分 12bは、フーリエ変換すると、画素の形状に
起因した強度分布を有する形状成分パターン 31bとなる。なお、図 3の配置成分バタ ーン 31aおよび形状成分パターン 31bは、図 2の配置成分パターン 137aおよび形状 成分パターン 137bを 45° 回転させたものと同じである。 The spatial light modulator 11 in FIG. 3 can also be decomposed into an arrangement component 12 a resulting from the arrangement of the pixel 12 and a shape component 12 b resulting from the shape of the pixel 12 as in the case of FIG. The arrangement component 12a is subjected to Fourier transform to obtain an arrangement component pattern 3la having a bright spot 33a arranged in a similar shape to the arrangement component 12a, and the shape component 12b is converted to a pixel shape by Fourier transformation. The resulting shape component pattern 31b has an intensity distribution. The arrangement component pattern 31a and the shape component pattern 31b in FIG. 3 are the same as those obtained by rotating the arrangement component pattern 137a and the shape component pattern 137b in FIG. 2 by 45 °.
[0049] 図 3のように、対物レンズに向力う出射光の光軸を m次の回折光と一致しないように 構成すると、配置成分パターン 31aの輝点 33aが光軸からずれる。これは、図 4の形 状成分パターン 41に対し、中心にピークが位置しな 、配置成分パターン 43を重ね 合わせて掛け合わせたときの合成パターン 45の関係に相当する。合成パターン 45 において、点線で形状成分パターン 41を示しており、中心に近い 2つのピークが共 に強 、強度を示して 、ることが分かる。 As shown in FIG. 3, when the optical axis of the outgoing light directed toward the objective lens is configured not to match the m-th order diffracted light, the bright spot 33a of the arrangement component pattern 31a is shifted from the optical axis. This corresponds to the relationship of the composite pattern 45 when the arrangement component pattern 43 is overlapped and multiplied with the shape component pattern 41 of FIG. In the composite pattern 45, the shape component pattern 41 is indicated by a dotted line, and it can be seen that the two peaks near the center are both strong and strong.
[0050] 図 3においては、画素 12の対角方向(図 3においては横方向 15、図 2においては 斜め 45° の方向)における m+O. 5次の回折光の位置が光軸と一致するようにして おり、光軸は 4つの輝点 33aの中心となる。ここで、対角方向についての回折次数を 求める式 3 :m ≠a (sin 0 -sin 0 )における周期 aは、図 3に示すように、回転軸 1 [0050] In FIG. 3, the position of the m + O. 5th-order diffracted light coincides with the optical axis in the diagonal direction of pixel 12 (lateral direction 15 in FIG. 3, oblique 45 ° direction in FIG. 2). The optical axis is the center of the four bright spots 33a. Here, the period a in Equation 3: m ≠ a (sin 0 -sin 0) for obtaining the diffraction order in the diagonal direction is the rotation axis 1 as shown in Fig. 3.
1 0 Ten
4間の間隔 (画素の対角線の半分)となる。つまり、画素の 1辺の長さを Lとすると 21/2· L/2となる。 The interval between 4 (half the diagonal of the pixel). In other words, if the length of one side of the pixel is L, then 2 1/2 · L / 2.
[0051] 他方、形状成分パターン 3 lbの位置は、前述した式 2 : 0 = Θ — 2Ψにおける出 [0051] On the other hand, the position of the shape component pattern 3 lb is expressed in the above-described formula 2: 0 = Θ — 2Ψ.
1 0 Ten
射角 Θ によって求められるので、形状成分パターン 31bの中心は、出射角 Θ の出 The center of the shape component pattern 31b is the output angle Θ.
1 1 射光の光軸と一致する。このため、配置成分パターン 3 laと形状成分パターン 3 lbと を重ね合わせて掛け合わせたパターン 31は、光軸近傍にある 4つの基本空間周波 数による輝点 33において強度が強ぐそれら力 遠ざかるにつれて各基本空間周波 数による輝点 33の強度が弱くなる。 1 1 Matches the optical axis of the incident light. For this reason, the pattern 31 obtained by superimposing the arrangement component pattern 3 la and the shape component pattern 3 lb overlaps with each other as the strength increases at the bright spot 33 at the four basic spatial frequencies near the optical axis. The intensity of the bright spot 33 due to each fundamental spatial frequency decreases.
[0052] このように、対物レンズに向力う出射光の光軸を m次の回折光と一致しないように構 成すると、最も強度の強い領域に空間光変調器の基本空間周波数による輝点 33を 複数個配置させることができ、干渉縞の強度を強くすることができる。 [0052] As described above, when the optical axis of the outgoing light directed toward the objective lens is configured not to match the m-th order diffracted light, the bright spot due to the fundamental spatial frequency of the spatial light modulator is shown in the strongest region. A plurality of 33 can be arranged, and the intensity of interference fringes can be increased.
[0053] また、画素の反射面の傾斜角度の誤差等によって、出射角 Θ にバラツキが生じて [0053] Further, the output angle Θ varies due to an error in the tilt angle of the reflective surface of the pixel.
1 1
、形状成分パターン 31bのフーリエ面における位置がずれたとしても、複数の基本空 間周波数による輝点 33が存在するため、ホログラムの記録領域内において強い強度 を保つことができ、信頼性が向上する。
[0054] 更に、従来では、中心に非常に強い光強度の領域が局在化するため、光情報記録 媒体のホログラム記録層中におけるモノマー濃度が部分的に枯渴してしま 、多重記 録の妨げとなることもあったが、本発明では、光強度の強い領域に複数の基本空間 周波数による輝点 33を配置させているので、ホログラムの記録領域内における光強 度分布を従来に比較すれば平均化することができる。この結果、モノマー濃度も平均 的に減少し、多重記録特性を向上できるので、記録容量を増やすことができる。 Even if the position of the shape component pattern 31b in the Fourier plane is shifted, there are bright spots 33 with a plurality of fundamental spatial frequencies, so that strong intensity can be maintained in the hologram recording area, and reliability is improved. . [0054] Further, conventionally, since a region of very strong light intensity is localized at the center, the monomer concentration in the hologram recording layer of the optical information recording medium is partially depleted. In the present invention, since the bright spots 33 having a plurality of fundamental spatial frequencies are arranged in the region where the light intensity is strong, the light intensity distribution in the hologram recording region is compared with the conventional one. Can be averaged. As a result, the monomer concentration also decreases on average, and the multiple recording characteristics can be improved, so that the recording capacity can be increased.
[0055] 別の利点として、対物レンズに向力う出射光の光軸を m次の回折光と一致しないよ うに構成すると、ホログラムサイズを小さくすることも可能となる。図 2のパターン 137に おいて、ホログラムの記録領域 139を白丸で示す。図 2においては、全ての空間周波 数特性を得るためにはホログラムの記録領域 139中に、少なくとも中心の輝点 138と その四方に位置する輝点 138を含める必要があった。これに対し、図 3のパターン 31 に示すように、本発明においては、光軸の近傍に位置する 4つの輝点 33によって全 ての空間周波数特性が示されるため、それら 4つの輝点 33を含む大きさまでホロダラ ムの記録領域 34 (白丸で示す)を小さくすることができる。よって、一つ当たりのホログ ラムサイズを小さくできるので、その分、多くのホログラムを記録することができ、記録 容量を増やすことができる。 [0055] As another advantage, if the optical axis of the outgoing light directed toward the objective lens is configured not to match the m-th order diffracted light, the hologram size can be reduced. In the pattern 137 in FIG. 2, the hologram recording area 139 is indicated by a white circle. In FIG. 2, in order to obtain all the spatial frequency characteristics, it is necessary to include at least the central bright spot 138 and the bright spots 138 located in the four directions in the hologram recording area 139. In contrast, as shown in the pattern 31 of FIG. 3, in the present invention, all four bright spots 33 located in the vicinity of the optical axis indicate all the spatial frequency characteristics. The hologram recording area 34 (indicated by white circles) can be reduced to a size that includes it. Accordingly, since the size of each hologram can be reduced, a larger number of holograms can be recorded accordingly, and the recording capacity can be increased.
[0056] 具体的に、 DMDにおいて、 DMDから対物レンズに対して垂直に出射させ(0 = [0056] Specifically, in the DMD, the DMD emits perpendicularly to the objective lens (0 =
1 1
0)、出射光の光軸が(m+O. 5)次の回折光の進行方向とする場合、 (m+O. 5) λ =— a' sin2¥の関係式を満たすことになる。例えば、テキサス 'インスツルメンッ社製 0. 7インチ XGA(1024 X 768画素)型 DMDの場合、正方形状の画素のピッチが 1 3. 68 /z mであるから、対角方向における(m+O. 5)次の回折光の進行方向を選択 した場合、画素の周期 aは、 21 2· 13. 68 ^ πι/2 = 9. 65 /z mとなる。図 5は、この D MDにおいて、波長 532nmの光と波長 410nmの光を使用したとき、対角方向にお ける(m+O. 5)次の回折光の進行方向となる画素の傾斜角および入射角である。こ の DMDの傾斜角は 11〜13° の設計であるから、その角度の範囲内としては、波長 532nmの光を使用する場合は、 7. 5次光の進行方向となるように画素の傾斜角 を 12. 18° とし DMDへの入射角を 24. 36° とし、波長 410nmの光を使用する場 合は、 9. 5次光の進行方向となるように画素の傾斜角を 11. 87° とし DMDへの
入射角を 23. 74° とする。 0) When the optical axis of the emitted light is the (m + O.5) -order diffracted light traveling direction, the relational expression (m + O.5) λ = —a ′ sin2 ¥ is satisfied. For example, in the case of a 0.7 inch XGA (1024 X 768 pixels) DMD manufactured by Texas Instruments Inc., the square pixel pitch is 1 3.68 / zm, so (m + O.5 in the diagonal direction) ) When the traveling direction of the next diffracted light is selected, the pixel period a is 2 1 2 · 13. 68 ^ πι / 2 = 9.65 / zm. Fig. 5 shows the tilt angle of the pixel, which is the traveling direction of the diffracted light in the diagonal direction (m + O.5) when using light with a wavelength of 532 nm and light with a wavelength of 410 nm. Incident angle. The DMD tilt angle is designed to be 11 to 13 °. Therefore, within the angle range, when using light with a wavelength of 532 nm, the tilt of the pixel is set to be the direction of travel of the fifth-order light. If the angle is 12.18 °, the angle of incidence on the DMD is 24.36 °, and light with a wavelength of 410 nm is used, the pixel tilt angle is 11.87 so that the 9.5th-order light travels. ° To DMD The incident angle is 23.74 °.
[0057] 図 6乃至図 9は、波長 532nmの光を使用し、画素の傾斜角が 11. 4° 、 12. 0° 、 12. 2° 、 12. 4° の DMDに対し、 24. 4° の入射角で光を入射させた場合のフー リエ変換像を示す。なお、それぞれ上段が全ての画素をオン状態とした場合であり、 下段がオン状態とオフ状態 (斜線の網掛けを付している)の画素をランダムに配置し た場合である。 [0057] FIGS. 6 to 9 show that for a DMD using light with a wavelength of 532 nm and pixel tilt angles of 11.4 °, 12.0 °, 12.2 °, and 12.4 °, 24.4 A Fourier transform image is shown when light is incident at an incident angle of °. The upper row shows the case where all the pixels are in the on state, and the lower row shows the case where the pixels in the on state and the off state (hatched with hatching) are randomly arranged.
[0058] 図 6は、 DMD61の画素 62の傾斜角が 11. 4° であるから、出射角は 24. 4° —2 [0058] In FIG. 6, since the tilt angle of the pixel 62 of the DMD 61 is 11.4 °, the output angle is 24.4 ° —2
X I I . 4° = 1. 6° である。出射角 1. 6° の回折次数は、 9. 65 /z m X (sin(l . 6° ) -sin (24. 4° ) ) Z532nm=— 7. 00次光である。従って、図 6では、従来の光情 報記録再生装置と同様、出射光の光軸が回折光と一致する。図 6において、上段の フーリエ変換パターン 63は、中心より左側の基本空間周波数による輝点に光軸が位 置しており、その位置で光強度が強くなつている。しかし、肝心のホログラム記録領域 (白丸) 64では、光強度が弱く干渉縞の強度が弱くなる。また、オンの画素 62aとオフ の画素 62bをランダムに配置した下段のフーリエ変換パターン 65では、各輝点がぼ やけており、光強度の分布が広がっている。しかし、やはりホログラム記録領域(白丸 ) 64の一部において光強度が弱くなつており、信頼性のある情報の記録再生が難し い。 X I I. 4 ° = 1.6 °. The diffraction order at an output angle of 1.6 ° is 9.65 / z m X (sin (l.6 °) -sin (24.4 °)) Z532nm = —7.00th order light. Therefore, in FIG. 6, as in the conventional optical information recording / reproducing apparatus, the optical axis of the emitted light coincides with the diffracted light. In FIG. 6, in the upper Fourier transform pattern 63, the optical axis is located at the bright spot with the fundamental spatial frequency on the left side of the center, and the light intensity is strong at that position. However, in the essential hologram recording area (white circle) 64, the light intensity is weak and the interference fringes are weak. Further, in the lower Fourier transform pattern 65 in which the on-pixel 62a and the off-pixel 62b are randomly arranged, each bright spot is blurred and the light intensity distribution is widened. However, the light intensity is still weak in a part of the hologram recording area (white circle) 64, and it is difficult to record and reproduce reliable information.
[0059] 図 7は、 DMD71の画素 72の傾斜角が 12. 0° であるから、出射角は 24. 4° —2 [0059] In FIG. 7, since the tilt angle of the pixel 72 of the DMD 71 is 12.0 °, the output angle is 24.4 ° —2
X 12. 0° =0. 4° である。出射角 0. 4° の回折次数は、 9. 65 m X (sin(0. 4° ) -sin(24. 4° ) ) Z532nm=— 7. 37次光である。従って、図 7では、出射光の光 軸が回折光と一致していない。図 7において、上段のフーリエ変換パターン 73は、中 心近傍の 4つの基本空間周波数による輝点のうち、左側の輝点の光強度が若干強 いが、他の 3つの輝点も十分光強度が強ぐホログラム記録領域(白丸) 74全体で干 渉縞を記録することが可能である。オンの画素 72aとオフの画素 72bをランダムに配 置した下段のフーリエ変換パターン 75においても、中心より若干左側に偏っているが 、ホログラム記録領域(白丸) 74の全体に光強度の分布が広がっているので、干渉縞 を記録することができ、信頼性のある情報の記録再生をすることが可能である。 X 12. 0 ° = 0.4 °. The diffraction order at an output angle of 0.4 ° is 9.65 m X (sin (0.4 °) -sin (24.4 °)) Z532nm = — 7.37th order light. Therefore, in FIG. 7, the optical axis of the emitted light does not coincide with the diffracted light. In Fig. 7, the upper Fourier transform pattern 73 shows that the light intensity of the left bright spot is slightly strong among the four basic spatial frequency bright spots near the center, but the other three bright spots have sufficient light intensity. It is possible to record interference fringes in the entire hologram recording area (white circle) 74. The lower Fourier transform pattern 75 in which the on-pixel 72a and the off-pixel 72b are randomly arranged is also slightly deviated to the left of the center, but the light intensity distribution spreads over the entire hologram recording area (white circle) 74. Therefore, interference fringes can be recorded and information can be recorded and reproduced with high reliability.
[0060] 図 8は、 DMD81の画素 82の傾斜角が 12. 2° であるから、出射角は 24. 4° —2
X 12. 2° =0° である。出射角 0° の回折次数は、 9. 65 m X (sin (0° )—sin ( 24. 4° ) ) Z532nm=— 7. 49次光である。従って、図 8では、出射光の光軸が回 折光と一致していない。図 8において、上段のフーリエ変換パターン 83は、中心近傍 の 4つの基本空間周波数による輝点が均等に光強度が強くなつており、ホログラム記 録領域(白丸) 84全体で均一な干渉縞を記録することが可能である。オンの画素 82a とオフの画素 82bをランダムに配置した下段のフーリエ変換パターン 85においても、 ホログラム記録領域(白丸) 84の全体に光強度の分布が広がって 、るので、均等に 干渉縞を記録することができ、信頼性のある情報の記録再生をすることが可能である [0060] In FIG. 8, since the tilt angle of the pixel 82 of the DMD81 is 12.2 °, the output angle is 24.4 ° -2 X 12. 2 ° = 0 °. The diffraction order at an output angle of 0 ° is 9.65 m X (sin (0 °) —sin (24.4 °)) Z532nm = — 7. 49th order light. Therefore, in FIG. 8, the optical axis of the emitted light does not coincide with the diffracted light. In Fig. 8, the Fourier transform pattern 83 in the upper part shows that the bright spots of the four basic spatial frequencies in the vicinity of the center are equally strong in light intensity, and records uniform interference fringes throughout the hologram recording area (white circle) 84. Is possible. Even in the lower Fourier transform pattern 85 in which the ON pixels 82a and OFF pixels 82b are randomly arranged, the light intensity distribution spreads out over the entire hologram recording area (white circle) 84, so that interference fringes are recorded evenly. It is possible to record and reproduce reliable information
[0061] 図 9は、 DMD91の画素 92の傾斜角が 12. 4° であるから、出射角は 24. 4° —2 [0061] In Fig. 9, since the tilt angle of the pixel 92 of the DMD 91 is 12.4 °, the exit angle is 24.4 ° -2
X 12. 4° = -0. 4° である。出射角— 0. 4° の回折次数は、 9. 65 m X (sin ( -0. 4° )—sin (24. 4° ) ) Z532nm=— 7. 62次光である。従って、図 9では、出 射光の光軸が回折光と一致していない。図 9において、上段のフーリエ変換パターン 93は、中心近傍の 4つの基本空間周波数による輝点のうち、右側の輝点の光強度が 若干強いが、他の 3つの輝点も十分光強度が強ぐホログラム記録領域(白丸) 94全 体で干渉縞を記録することが可能である。オンの画素 92aとオフの画素 92bをランダ ムに配置した下段のフーリエ変換パターン 95にお 、ても、中心より若干左側に偏つ て!、るが、ホログラム記録領域(白丸) 94の全体に光強度の分布が広がって 、るので 、干渉縞を記録することができ、信頼性のある情報の記録再生をすることが可能であ る。 X 12. 4 ° = -0. 4 °. The diffraction angle at the exit angle—0.4 ° is 9.65 m X (sin (−0.4 °) —sin (24.4 °)) Z532nm = —7.62nd order light. Therefore, in FIG. 9, the optical axis of the emitted light does not coincide with the diffracted light. In Fig. 9, the upper Fourier transform pattern 93 has a slightly strong light intensity at the right bright spot among the four bright spots with four fundamental spatial frequencies near the center, but the other three bright spots are sufficiently strong. The hologram recording area (white circle) 94 can record interference fringes throughout. In the lower Fourier transform pattern 95 in which the on-pixel 92a and the off-pixel 92b are randomly arranged, it is slightly shifted to the left of the center! However, the entire hologram recording area (white circle) 94 Since the light intensity distribution is widened, interference fringes can be recorded and information can be recorded and reproduced with high reliability.
[0062] なお、上記傾斜角の範囲は一製品における設計値であり、上記数値に限定される ものではない。例えば、傾斜角を 10. 5° とすれば、波長 532nmの光を使用する場 合は、 6. 5次光の進行方向とすることができ、波長 410nmの光を使用する場合は、 8. 5次光の進行方向とすることができるので、汎用性の高い DMDを製造することが できる。また、画素の間隔が変更されれば、角度も再度設計する必要がある。 [0062] The range of the tilt angle is a design value for one product, and is not limited to the above numerical value. For example, if the tilt angle is 10.5 °, the direction of travel of the quintic light can be used when using light with a wavelength of 532 nm, and when using light with a wavelength of 410 nm, 8. Since the direction of travel of the fifth-order light can be set, a highly versatile DMD can be manufactured. Also, if the pixel spacing is changed, the angle must be redesigned.
[0063] また、上では DMDのように、反射型の画素を有する空間光変調器を主に説明した 力 透過型の空間光変調器にも適用できる。図 10は、透過型の空間光変調器 11に おける入射光 21、出射光 22および回折光 23の関係を示すものである。
[0064] まず、透過型の空間光変調器 11においても、入射する光 21の入射角を Θ 、空間 In addition, the present invention can also be applied to a force-transmitting spatial light modulator that mainly describes a spatial light modulator having a reflective pixel, such as a DMD. FIG. 10 shows the relationship between the incident light 21, the emitted light 22, and the diffracted light 23 in the transmissive spatial light modulator 11. First, in the transmissive spatial light modulator 11, the incident angle of the incident light 21 is Θ
0 光変調器 11から出射される光 22の出射角を Θ 、光の波長をえ、空間光変調器 11 0 The angle of light 22 emitted from the optical modulator 11 is Θ, the wavelength of the light is obtained, and the spatial light modulator 11
1 1
における複数の画素 12の周期を a、回折光 23の回折次数を m(m=0, ±1, ±2···) とすると、式3:111ぇ≠& 110 -sin0 )の関係式を満たすように装置を構成する。 If the period of multiple pixels 12 in a is a and the diffraction order of the diffracted light 23 is m (m = 0, ± 1, ± 2 ...), the relational expression of Equation 3: 111 ≠ ≠ & 110 -sin0) is obtained. Configure the device to meet.
1 0 Ten
ただし、図 10においては、射出角 Θ は 0° のため図示していない。このため、透過 However, in FIG. 10, the exit angle Θ is not shown because it is 0 °. Because of this, transmission
1 1
型の空間光変調器 11は、屈折手段 16を有している。図 10において、入射光 21は、 空間光変調器 11に対し、入射角 Θ で入射する。空間光変調器 11の複数の画素 12 The spatial light modulator 11 of the type has a refracting means 16. In FIG. 10, incident light 21 is incident on the spatial light modulator 11 at an incident angle Θ. Multiple pixels of spatial light modulator 11 12
0 0
によって変調された出射光 22は、屈折手段 16を経て出射角 Θ で射出される。透過 The outgoing light 22 modulated by is emitted through the refracting means 16 at an outgoing angle Θ. Transparent
1 1
型の空間光変調器 11においては、屈折手段 16によって入射光 21が屈折されるの で、出射光 22の入射光 21に対する角度を 0 とすると、 0 = 0 — 0 となる。他方、 r 1 0 r In the spatial light modulator 11 of the type, since the incident light 21 is refracted by the refracting means 16, if the angle of the emitted light 22 with respect to the incident light 21 is 0, 0 = 0−0. On the other hand, r 1 0 r
空間光変調器 11の複数の画素 12が回折格子として機能するので、式 l:a(sin0 - d sin0 )=m (m=0, ±1, ±2···)にしたがって回折角 0 の回折光 23が発生するSince the plurality of pixels 12 of the spatial light modulator 11 function as a diffraction grating, the diffraction angle 0 is determined according to the equation l : a (sin0-d sin0) = m (m = 0, ± 1, ± 2 ...) Diffracted light 23 is generated
0 d 0 d
[0065] 図 10に示すように、出射光 22の角度 0 は 0° であること、つまり出射光 22の光軸 As shown in FIG. 10, the angle 0 of the outgoing light 22 is 0 °, that is, the optical axis of the outgoing light 22
1 1
が空間光変調器 11に対して垂直となるように構成することが好ましい。この場合、 sin Θ =0となるので、式 3は、 m ≠— a'sin0 となり、入射角 0 としては、 (m+O.2) Is preferably perpendicular to the spatial light modulator 11. In this case, sin Θ = 0, so Equation 3 becomes m ≠ — a'sin0, and the incident angle 0 is (m + O.2)
1 0 0 1 0 0
λ≤-α·3ίηθ ≤(m+0.8)の関係式を満たすことが好ましぐ特に約(m+O.5) It is particularly preferable to satisfy the relation of λ≤-α · 3ίηθ ≤ (m + 0.8) (m + O.5)
0 0
l=-a-sin0 の関係式を満たすことがより好ましい。ここで、 θ = θ — Θであるか It is more preferable to satisfy the relational expression of l = -a-sin0. Where θ = θ — Θ
0 1 0 r ら、 Θ =0の場合、 θ = θであり、上記式 3は、 m ≠— a'sin0となり、出射光 22 0 1 0 r et al., When Θ = 0, θ = θ, and the above equation 3 becomes m ≠ — a'sin0, and the output light 22
1 0 r r 1 0 r r
の入射光 21に対する角度 Θ としては、 (m+O.2)l≤-a-sin0 ≤ (m+O.8)の r 0 The angle Θ with respect to incident light 21 is r 0 of (m + O.2) l≤-a-sin0 ≤ (m + O.8)
関係式を満たすことが好ましい。別の見方をすれば、出射光 22の入射光 21に対す る角度 0 力 m ≠—a'sin0 の関係式を満たすと、出射光 22の光軸が、空間光 変調器 11に対して垂直となり、且つ回折光と一致しない構成となる。 It is preferable to satisfy the relational expression. From another viewpoint, the angle of the output light 22 with respect to the incident light 21 satisfies the relation of 0 force m ≠ —a'sin0, and the optical axis of the output light 22 is perpendicular to the spatial light modulator 11. And the configuration does not match the diffracted light.
[0066] 屈折手段 16としては、角度の付いたエツヂゃ位相板を使用することが可能である。 As the refracting means 16, an angled phase plate can be used.
周囲の材質と屈折率が異なる透明部材のエツヂに角度を付けると、部分的に厚さが 異なるので位相差を生じる。また、位相板とは、透明部材に部分的に屈折率の異なる 部分を設けたものであり、屈折率の異なる部分の厚みによって、位相差を生じさせる ものである。なお、図 10においては、空間光変調器 11の出射面側に屈折手段 16を
配置したが、入射面側に屈折手段 16を配置してもよいし、空間光変調器 11内部の 一機能として屈折手段 16を実現してもよい。 If the edge of a transparent member having a refractive index different from that of the surrounding material is angled, a phase difference is generated because the thickness is partially different. Further, the phase plate is a transparent member in which a portion having a different refractive index is provided, and a phase difference is generated depending on the thickness of the portion having a different refractive index. In FIG. 10, the refracting means 16 is provided on the exit surface side of the spatial light modulator 11. However, the refracting means 16 may be arranged on the incident surface side, or the refracting means 16 may be realized as a function inside the spatial light modulator 11.
[0067] 更に、本発明の光情報記録方法では、情報光用空間変調パターンが複数の基準 マークを含み、基準マークの領域内における空間周波数が、空間光変調器の基本 空間周波数よりも小さい空間周波数を含むようにする。別の見方をすれば、基準マー クの領域内における画素の周期性が、空間光変調器の画素同士の周期性よりも大き くなればよい。例えば、オン画素とオフ画素を交互に配置したパターンの空間周波数 は、基本空間周波数の半分になる。 Furthermore, in the optical information recording method of the present invention, the spatial modulation pattern for information light includes a plurality of reference marks, and the spatial frequency in the reference mark region is smaller than the basic spatial frequency of the spatial light modulator. To include the frequency. From another viewpoint, it is sufficient that the periodicity of the pixels in the reference mark region is larger than the periodicity of the pixels of the spatial light modulator. For example, the spatial frequency of a pattern in which ON pixels and OFF pixels are alternately arranged is half the basic spatial frequency.
[0068] 図 11 (A)乃至 (C)は、それぞれ上段に直線状に配列した 8画素の空間変調パター ンを示し、下段に光強度と周期性 tとを示すものであり、空間変調パターンと周期性 t の関係を説明するための図である。なお、図 11 (A)乃至 (C)において、空間変調パ ターンはオン状態とオフ状態の 2値力 構成されて 、る。 [0068] FIGS. 11 (A) to 11 (C) each show an 8-pixel spatial modulation pattern arranged linearly in the upper stage, and the light intensity and periodicity t in the lower stage. It is a figure for demonstrating the relationship between and periodicity t. In FIGS. 11A to 11C, the spatial modulation pattern is composed of a binary force of an on state and an off state.
[0069] 図 11 (A)は、 8個の画素が全てオン状態の空間変調パターン 1101であり、隣接す る画素と画素の間隔 aの周期 tを有するので、その空間周波数は基本空間周波数と [0069] FIG. 11 (A) shows a spatial modulation pattern 1101 in which all eight pixels are in the ON state, and has a period t of the distance a between adjacent pixels, so that the spatial frequency is the fundamental spatial frequency.
1 1
なる。図 11 (A)において、画素と画素との間で光強度が 0となっているのは、空間光 変調器の画素と画素との間の隙間によるものである。図 11 (B)は、オン画素とオフ画 素が交互に配置された空間変調パターン 1102であり、 2画素分の間隔(2 X a)の周 期 tを有する。図 11 (B)の空間変調パターン 1102の周期 tは図 11 (A)の空間変調 Become. In FIG. 11 (A), the light intensity between the pixels is 0 because of the gap between the pixels of the spatial light modulator. FIG. 11B shows a spatial modulation pattern 1102 in which ON pixels and OFF pixels are alternately arranged, and has a period t of an interval of 2 pixels (2 Xa). The period t of the spatial modulation pattern 1102 in Fig. 11 (B) is the spatial modulation in Fig. 11 (A).
2 2 twenty two
パターン 1101の周期 tの 2倍であるから、空間変調パターン 1102の空間周波数は Since it is twice the period t of pattern 1101, the spatial frequency of spatial modulation pattern 1102 is
1 1
基本空間周波数の半分となる。図 11 (C)は、オン画素とオフ画素が 2画素づっ交互 に配置された空間変調パターン 1103であり、 4画素分の間隔 (4 X a)の周期 tと 1画 Half of the fundamental spatial frequency. Fig. 11 (C) shows a spatial modulation pattern 1103 in which ON and OFF pixels are arranged alternately in two pixels, with a period t of 4 pixels (4 X a) and one image.
3 素分の間隔 aの周期 tとを有している。このうち周期 tは周期 tの 4倍であるから、空 3 has a period t with an interval a. Of these, the period t is four times the period t.
1 3 1 1 3 1
間変調パターン 1103は基本空間周波数の四分の一の空間周波数を含んでいる。 The intermodulation pattern 1103 includes a spatial frequency that is a quarter of the fundamental spatial frequency.
[0070] 空間変調パターンの周期が大きくなると、空間周波数が小さくなり、大きい周期を有 する空間変調パターンをフーリエ変換すると、基本空間周波数による輝点と輝点の 間に輝点が発生する。つまり、本発明においては、基準マークをフーリエ変換するこ とで発生する輝点(以下「基準マークによる輝点」という)が、基本空間周波数による 輝点と輝点の間に発生する。
[0071] 図 12 (A)及び (B)は、図 3と同様に、画素の対角方向における m+O. 5次の回折 光の位置が光軸と一致する、即ち光軸が 4つの基本空間周波数による輝点 33の中 心となる状態で、全ての画素をオン状態とした空間変調パターン 1201及び格子状に 画素をオン状態とした空間変調パターン 1202のフーリエ変換したパターンを示す。 [0070] When the period of the spatial modulation pattern increases, the spatial frequency decreases, and when a spatial modulation pattern having a large period is Fourier transformed, a bright spot is generated between the bright spot and the bright spot by the basic spatial frequency. That is, in the present invention, a bright spot generated by Fourier transform of the reference mark (hereinafter referred to as “bright spot by the reference mark”) is generated between the bright spot by the basic spatial frequency. [0071] FIGS. 12A and 12B are similar to FIG. 3, in which the position of the m + O. Fifth-order diffracted light in the diagonal direction of the pixel coincides with the optical axis, that is, there are four optical axes. A spatially transformed pattern 1201 in which all the pixels are in an on state and a spatial modulation pattern 1202 in which the pixels are in an on state in a lattice form in the state of being the center of the bright spot 33 by the basic spatial frequency is shown.
[0072] 図 12 (A)の全ての画素をオン状態とした空間変調パターン 1201の場合は、基本 空間周波数力もなるので、パターン 1203に示すように、 4つの基本空間周波数によ る輝点 1205の中心が光軸となる。図 20に示すとおり、従来の情報光用空間光変調 パターンにおいて、基準マーク 147は、 4 X 4の正方形状の画素を全てオン状態(図 [0072] In the case of the spatial modulation pattern 1201 in which all the pixels in FIG. 12A are in the on state, the fundamental spatial frequency force is also obtained, and as shown in the pattern 1203, the bright spots 1205 by the four basic spatial frequencies 1205 The center of is the optical axis. As shown in Fig. 20, in the conventional spatial light modulation pattern for information light, the reference mark 147 has all the 4 x 4 square pixels turned on (Fig.
20においては網掛けで示す)としたパターンであった。このため、基準マーク 147の 領域内の空間周波数は基本空間周波数となり、フーリエ変換することで得られる基準 マークによる輝点は、図 12 (A)のパターン 1203となる。このため、図 12 (A)のパタ ーン 1203において、ホログラム 1207の大きさを小さくしていくと、まず基準マークに よる輝点がホログラム 1207の範囲から外れるため、最初に基準マークの SN比が悪く なる。さらにホログラム 1207の大きさを小さくすると、再生した空間変調パターンから 基準マークが消えて情報が再生できなくなる。 In Fig. 20, the pattern is indicated by shading). For this reason, the spatial frequency in the region of the reference mark 147 becomes the fundamental spatial frequency, and the bright spot by the reference mark obtained by Fourier transform becomes the pattern 1203 in FIG. For this reason, in pattern 1203 in FIG. 12 (A), when the size of hologram 1207 is reduced, the bright spot due to the reference mark first deviates from the range of hologram 1207. Becomes worse. If the hologram 1207 is further reduced in size, the reference mark disappears from the reproduced spatial modulation pattern, and information cannot be reproduced.
[0073] これに対し、図 12 (B)に示すとおり、格子状に画素をオン状態とした空間変調バタ ーン 1202の場合は、空間周波数が基本空間周波数の半分であるから、パターン 12 04に示すように、隣接する 4つの基本空間周波数による輝点 1205によって形成され る正方形(図 12 (A)及び (B)の点線 1206を参照)の中心の位置にも輝点が発生す る。このため、図 12 (B)に示すような格子状の空間変調パターンを基準マークとして 使用すると、その領域内の空間周波数は、基本空間周波数の半分となり、基準マー クによる輝点は、図 12 (B)のパターン 1204のようになる。この結果、基準マークによ る輝点が 4つの基本空間周波数による輝点の内部に存在し、ホログラム 1207の大き さを小さくしても、基準マークが消えず信頼性を向上させることができる。そして、ホロ グラムの大きさをより小さくすることが可能となり、記録容量を向上させることも可能と なる。 On the other hand, as shown in FIG. 12 (B), in the case of the spatial modulation pattern 1202 in which the pixels are turned on in a lattice shape, the spatial frequency is half of the basic spatial frequency. As shown in Fig. 5, a bright spot is also generated at the center position of a square (see dotted line 1206 in Figs. 12A and 12B) formed by bright spots 1205 having four adjacent fundamental spatial frequencies. For this reason, when a lattice-like spatial modulation pattern as shown in Fig. 12 (B) is used as a reference mark, the spatial frequency in that region becomes half of the basic spatial frequency, and the bright spot by the reference mark is shown in Fig. 12. It becomes like pattern 1204 of (B). As a result, the bright spot due to the reference mark exists inside the bright spot with the four fundamental spatial frequencies, and even if the size of the hologram 1207 is reduced, the reference mark does not disappear and the reliability can be improved. Further, the size of the hologram can be further reduced, and the recording capacity can be improved.
[0074] 特に、光軸上に基準マークによる輝点が位置すると、基準マークをより確実に再生 することができるので好ましい。例えば、図 12 (B)のように、画素の対角方向における
m+0. 5次の回折光の位置が光軸と一致する、即ち光軸力 つの基本空間周波数 による輝点 33の中心となる状態であれば、基準マークが基本空間周波数の半分の 空間周波数を含むようにすればょ 、。 [0074] In particular, it is preferable that the bright spot by the reference mark is located on the optical axis because the reference mark can be reproduced more reliably. For example, as shown in FIG. m + 0. If the position of the fifth-order diffracted light coincides with the optical axis, that is, the center of the bright spot 33 by the basic spatial frequency of the optical axis force, the reference mark has a spatial frequency that is half the basic spatial frequency. If you include it.
[0075] 図 13 (A)は、従来の情報光用空間光変調パターン 1301と参照光用空間光変調 ノターン 1302を示し、図 13 (B)は、本発明の一実施形態における情報光用空間光 変調パターン 1303と参照光用空間光変調パターン 1302を示す。図 13 (A)及び (B )では、中央に情報光用空間光変調パターン 1301、 1303が配置され、その周囲に 円環状の参照光用空間光変調パターン 1302が配置されている。中央に情報光用 空間光変調パターン 1301、 1303の全体的な構成は、記録する情報を一定情報量 の単位毎に符号ィ匕して、 2次元パターン情報のシンボル単位を生成し、一定量のシ ンボル単位と基準マークとを一つのブロック単位として構成し、複数のブロック単位を 配列させて形成されて!、る。 FIG. 13 (A) shows a conventional spatial light modulation pattern for information light 1301 and a spatial light modulation pattern for reference light 1302, and FIG. 13 (B) is a space for information light in one embodiment of the present invention. An optical modulation pattern 1303 and a spatial light modulation pattern 1302 for reference light are shown. In FIGS. 13A and 13B, information light spatial light modulation patterns 1301 and 1303 are arranged at the center, and an annular reference light spatial light modulation pattern 1302 is arranged therearound. In the center, the overall configuration of the spatial light modulation patterns 1301 and 1303 for information light encodes the information to be recorded for each unit of a certain amount of information to generate a symbol unit of two-dimensional pattern information, The symbol unit and the reference mark are formed as one block unit, and are formed by arranging a plurality of block units.
[0076] そして、図 13 (A)の従来の情報光用空間光変調パターン 1301においては、同図 左に示す一部拡大図から明らかなように、基準マーク 1305が 4 X 4の正方形状の画 素を全てオン状態としたパターンであり、図 13 (B)の情報光用空間光変調パターン 1 303においては、同図左に示す一部拡大図から明らかなように、基準マーク 1306が 画素を格子状にオン状態としたパターンである。なお、図 13 (A)及び (B)の拡大した 部分は、基準マーク 1305, 1306だけが配置され、シンボル単位は配置されていな いブロック単位の部分であり、情報光用空間光変調パターン 1301、 1303自体の位 置や向きの基準となる箇所である。 Then, in the conventional spatial light modulation pattern for information light 1301 shown in FIG. 13 (A), as is clear from the partially enlarged view shown on the left side of FIG. In the spatial light modulation pattern for information light 1303 in FIG. 13B, the reference mark 1306 is a pixel, as is clear from the partially enlarged view shown on the left side of the figure. Is a pattern in which is turned on in a lattice shape. Note that the enlarged portions of FIGS. 13A and 13B are portions of block units in which only the reference marks 1305 and 1306 are arranged and symbol units are not arranged, and the spatial light modulation pattern for information light 1301 , 1303 itself is the location and orientation standard.
[0077] 図 14及び図 15は、実際に開口(図 18においては 227の符号で示す)の大きさ(ァ パーチヤーサイズとも呼ぶ)を変えて記録した干渉縞を再生した時の空間光変調バタ ーンである。開口の大きさは、記録される干渉縞の大きさ(=ホログラムサイズ)に影 響し、開口が大きいと記録される干渉縞も大きぐ開口が小さくなると記録される干渉 縞も小さくなる。図 14では図 13 (A)の情報光用空間変調パターン 1301及び参照光 用空間変調パターン 1302を使用し、図 15では図 13 (B)の情報光用空間変調パタ ーン 1303及び参照光用空間変調パターン 1302を使用してホログラムを記録した。 図 14及び図 15において、上段の 5つの再生像は左力も順に開口の大きさが 8. 4m
m、 8. Omm、 7. 6mm、 7. 2mm及び 6. 8mmの条件で記録再生したものであり、下 段の 4つの再生像は左から順に開口の大きさが 6. 4mm、 6. Omm、 5. 6mm及び 5 . 2mmの条件で記録再生したものである。 FIG. 14 and FIG. 15 show the spatial light modulation when reproducing the recorded interference fringes by actually changing the size of the aperture (indicated by reference numeral 227 in FIG. 18) (also called aperture size). It is a pattern. The size of the aperture affects the size of the interference fringes to be recorded (= hologram size). The larger the aperture, the larger the interference fringe recorded, and the smaller the aperture, the smaller the interference fringe recorded. 14 uses the spatial modulation pattern for information light 1301 and the spatial modulation pattern for reference light 1302 in FIG. 13 (A), and FIG. 15 uses the spatial modulation pattern for information light 1303 and the reference light in FIG. 13 (B). Holograms were recorded using the spatial modulation pattern 1302. In Fig. 14 and Fig. 15, the upper five reproduced images have 8.4m in opening size in order of left force. m, 8. Omm, 7.6 mm, 7.2 mm, and 6.8 mm were recorded and played back. The four playback images in the lower row had an aperture size of 6.4 mm, 6. Omm in order from the left. , 5.6mm and 5.2mm recorded and reproduced.
[0078] 図 14の従来の光情報記録方法を使用した場合は、上段では基準マークを確認す ることができる力 開口の大きさが 6. 4mm以下の下段では基準マークが消えており 、基準マークを再生することができていない。図 15の本発明の光情報記録方法を使 用した場合は、上段でも下段でも基準マークを確認することができ、開口を小さくして も基準マークを再生することができた。 [0078] When the conventional optical information recording method of FIG. 14 is used, the reference mark can be confirmed in the upper stage. The reference mark disappears in the lower stage where the aperture size is 6.4 mm or less. The mark cannot be played. When the optical information recording method of the present invention shown in FIG. 15 was used, the fiducial mark could be confirmed both in the upper and lower stages, and the fiducial mark could be reproduced even if the aperture was reduced.
[0079] 図 16は、開口の大きさ(アパーチャ一サイズ)と再生した基準マークのビットエラー レートとの関係を示す図である。開口を小さくすると、記録されるホログラムの大きさも 小さくなる。図 16において、 4 X 4の正方形状の画素を全てオン状態とした従来の基 準マークの場合(參の折れ線)は、開口の大きさが 6. 4mm以下になると急激にビット エラーレートが増加し、全く再生できなくなってしまう。これに対し、格子状に画素をォ ン状態とした基準マークの場合(園の折れ線)は、開口の大きさが 6. 4mm以下にな つてもビットエラーレートがあまり増加せず、 4mmになってもビットエラーレートを約 0. 2に抑えることができた。 FIG. 16 is a diagram showing the relationship between the aperture size (aperture size) and the bit error rate of the reproduced reference mark. If the aperture is reduced, the size of the recorded hologram is also reduced. In Fig. 16, in the case of the conventional reference mark with all the 4 x 4 square pixels in the ON state (folded line), the bit error rate increases rapidly when the aperture size is 6.4 mm or less. However, it cannot be played at all. On the other hand, in the case of a fiducial mark in which the pixels are turned on in a grid pattern (garden line), the bit error rate does not increase so much even if the aperture size is 6.4 mm or less, and it becomes 4 mm. However, the bit error rate could be reduced to about 0.2.
[0080] 図 17 (A)乃至 (H)は、本発明の基準マークの他の実施形態を示すものである。図 17 (A)乃至 (H)において、白抜きの画素がオン状態であり、網掛けの画素がオフ状 態である。図 17 (A)乃至(D)では 4 X 4画素を基準マークの領域としている力 4 X 4 画素に限定されるものではない。図 17 (F)においては、基準マークの領域が 3 X 4画 素の場合であり、図 17 (G)及び (H)においては、基準マークの領域が 5 X 5画素の 場合である。 FIGS. 17A to 17H show another embodiment of the reference mark of the present invention. In FIGS. 17A to 17H, the white pixels are in the on state and the shaded pixels are in the off state. In FIGS. 17A to 17D, the force is not limited to 4 × 4 pixels with 4 × 4 pixels as the reference mark region. In FIG. 17 (F), the reference mark region is a 3 × 4 pixel, and in FIGS. 17 (G) and (H), the reference mark region is a 5 × 5 pixel.
[0081] 反射型の空間光変調器を使用した本発明の光情報記録再生装置のピックアップ 2 01の構成を図 18に示す。本発明のピックアップ 201は、本発明の光情報記録再生 装置のピックアップ 201は、記録再生用光源 203、コリメータレンズ 205、ミラー 207、 空間光変調器 209、偏光ビームスプリッタ 211、リレーレンズ 213、 215、開口 227、ミ ラー 217、 4分の 1波長板 219、対物レンズ 221、リングマスク 223、光検出手段 225 を備えている。
[0082] 図 18のピックアップ 201において、情報を記録または再生する場合、記録再生用 光源 203から射出された光は、コリメータレンズ 205によって平行光線とされ、ミラー 2 07によって空間光変調器 209に向力つて反射される。本発明では、空間光変調器 2 09の出射光 232が空間光変調器 209による回折光 233 (点線で示す)と一致しない ように、記録再生用光源 203から射出される光の波長、ミラー 207による空間光変調 器に対する入射光 231の入射角および空間光変調器の画素の周期が構成される。 なお、図 18のように反射型の画素を有する空間光変調器を使用する場合は、画素の 反射面の傾斜角も、空間光変調器の出射光 232がその回折光 233と一致しないよう に構成される。以下、光情報記録再生装置の各構成を順に説明する。 FIG. 18 shows the configuration of the pickup 201 of the optical information recording / reproducing apparatus of the present invention using a reflective spatial light modulator. The pickup 201 of the present invention is the same as the pickup 201 of the optical information recording / reproducing apparatus of the present invention, the recording / reproducing light source 203, collimator lens 205, mirror 207, spatial light modulator 209, polarization beam splitter 211, relay lenses 213, 215, An aperture 227, a mirror 217, a quarter-wave plate 219, an objective lens 221, a ring mask 223, and a light detection means 225 are provided. In the pickup 201 of FIG. 18, when information is recorded or reproduced, the light emitted from the recording / reproducing light source 203 is converted into parallel rays by the collimator lens 205 and directed to the spatial light modulator 209 by the mirror 207. Reflected with force. In the present invention, the wavelength of the light emitted from the recording / reproducing light source 203, the mirror 207 so that the outgoing light 232 of the spatial light modulator 209 does not coincide with the diffracted light 233 (shown by a dotted line) by the spatial light modulator 209. The incident angle of the incident light 231 to the spatial light modulator and the period of the pixels of the spatial light modulator are configured. When a spatial light modulator having a reflective pixel as shown in FIG. 18 is used, the angle of inclination of the reflective surface of the pixel is also set so that the outgoing light 232 of the spatial light modulator does not match the diffracted light 233. Composed. Hereinafter, each component of the optical information recording / reproducing apparatus will be described in order.
[0083] 記録再生用光源 203は、情報を記録するための情報光および記録用参照光を形 成するための光および情報を再生するための再生用参照光を形成するための光を 射出する。光源 203としては、コヒーレントな直線偏光の光線束を発生する例えば半 導体レーザを用いることができる。この記録再生用光源 203としては、高密度記録を 行うために波長が短い方が有利であり、青色レーザ (例えば波長 532nm)やグリーン レーザ (例えば波長 410nm)を採用することが好ましい。また、光源 203として、固体 レーザーを使用することもできる。 The recording / reproducing light source 203 emits light for forming information light for recording information and light for forming reference light for recording and light for forming reference light for reproduction for reproducing information. . As the light source 203, for example, a semiconductor laser that generates a coherent linearly polarized light beam can be used. As the recording / reproducing light source 203, a shorter wavelength is advantageous in order to perform high-density recording, and it is preferable to employ a blue laser (for example, wavelength 532 nm) or a green laser (for example, wavelength 410 nm). Further, a solid laser can be used as the light source 203.
[0084] コリメータレンズ 205は記録再生用光源 61からの発散光線束をほぼ平行光線とす るものである。 The collimator lens 205 converts the divergent light beam from the recording / reproducing light source 61 into a substantially parallel light beam.
[0085] ミラー 207は、記録再生用光源 203からの光を反射して空間光変調器 209へ向け るものである。ミラー 207によって、空間光変調器 209に入射する光 231の入射角を 調整することができる。例えば、波長の異なる光に対し、ミラーの位置または角度を変 更して、空間光変調器の出射光 232がその回折光 233と一致しないように調整可能 に設けてもよい。 The mirror 207 reflects the light from the recording / reproducing light source 203 toward the spatial light modulator 209. With the mirror 207, the incident angle of the light 231 incident on the spatial light modulator 209 can be adjusted. For example, the position or angle of the mirror may be changed with respect to light having different wavelengths so that the outgoing light 232 of the spatial light modulator does not coincide with the diffracted light 233.
[0086] 空間光変調器 209は、複数の画素を有し、各画素毎に出射光の位相または Zおよ び強度を変調することができる透過型または反射型の空間光変調器を使用すること ができる。空間光変調器 209としては、 DMD (デジタル 'マイクロミラー'デバイス)や マトリクス型の液晶素子を使用することができる。 DMDは、入射した光を画素ごとに 反射方向を変えることで強度を空間的に変調したり、入射した光を画素ごとに反射位
置を変えることで位相を空間的に変調することができる。液晶素子は、画素ごとに液 晶の配向状態を制御することで、入射した光の強度や位相を空間的に変調すること ができる。例えば、各画素毎に出射光の位相を、互いに πラジアンだけ異なる 2つの 値のいずれかに設定することによって、光の位相を空間的に変調することができる。 図 18において空間光変調器 209は、反射型であり、入射光を反射して空間光変調 器に対して垂直に射出させるように配置されて 、る。 Spatial light modulator 209 has a plurality of pixels, and uses a transmissive or reflective spatial light modulator that can modulate the phase or Z and intensity of emitted light for each pixel. be able to. As the spatial light modulator 209, a DMD (digital 'micromirror' device) or a matrix type liquid crystal element can be used. DMD spatially modulates the intensity of incident light by changing the reflection direction for each pixel, and reflects the incident light for each pixel. The phase can be spatially modulated by changing the position. The liquid crystal element can spatially modulate the intensity and phase of incident light by controlling the alignment state of the liquid crystal for each pixel. For example, the phase of light can be spatially modulated by setting the phase of outgoing light for each pixel to one of two values that differ from each other by π radians. In FIG. 18, the spatial light modulator 209 is of a reflective type, and is disposed so as to reflect incident light and emit it perpendicularly to the spatial light modulator.
[0087] そして、空間光変調器 209の表示面に情報光用空間変調パターンを表示して、表 示された情報光用空間変調パターンによって光を空間的に変調すれば、情報光を 生成することができる。情報光用空間変調パターンは、記録する情報を符号化して 得られる 2次元パターン情報を含むものであり、多段階に属性を変化させた画素を 2 次元的に配置して表現される。情報光用空間変調パターンの各画素毎に、例えば、 光の位相や強度等の状態を多段階に変化させる。以下の説明においては、各画素 毎に光の強度をオン(白色の画素)とオフ(黒色または網掛けの画素)の 2段階に変 化させる方法で説明する力 この方法に限定されるものではない。例えば、光の位相 を変化させてもよいし、 2段階ではなく 3段階以上に変化させてもよい。 [0087] Then, the information light spatial modulation pattern is displayed on the display surface of the spatial light modulator 209, and information light is generated by spatially modulating the light with the displayed information light spatial modulation pattern. be able to. The spatial modulation pattern for information light includes two-dimensional pattern information obtained by encoding information to be recorded, and is represented by two-dimensionally arranging pixels whose attributes are changed in multiple stages. For each pixel of the spatial modulation pattern for information light, for example, the state of light such as phase and intensity is changed in multiple stages. In the following explanation, the power explained in the method of changing the light intensity for each pixel in two steps of on (white pixel) and off (black or shaded pixel) is not limited to this method. Absent. For example, the phase of light may be changed, or it may be changed to three or more steps instead of two steps.
[0088] 記録用参照光は、空間的に変調されていてもよいし、空間的に変調されていなくて もよい。記録用参照光を空間的に変調すると、記録用参照光の空間変調パターンを 変えることで、多重記録することができるし、記録用参照光の空間変調パターンをキ 一とすることで、情報の不正アクセスに対する安全性を高めることができる。参照光を 空間的に変調する場合は、例えば、参照光用空間変調パターンを表示した空間光 変調器に光を照射して、参照光用空間変調パターンによって空間的に変調された参 照光を生成できる。一つの空間光変調器 209によって、情報光および記録用参照光 を生成する場合、空間光変調器 209の表示面に情報光用の領域および参照光用の 領域を設け、それぞれ情報光用空間変調パターンおよび記録用参照光用空間変調 ノターンを表示すればよい。情報光用の領域は、空間光変調器 209の中心付近に 配置し、情報光用の領域を囲うように参照光用の領域を環状に配置することが好まし い。なお、情報光と記録用参照光を生成する空間光変調器を別々に設けることもで きる。例えば、光源 203からの光をビームスプリッタ等により分割して、一方の光を第
一の空間光変調器によって空間的に変調して情報光を生成し、他方の光を第二の 空間光変調器によって空間的に変調して参照光を生成してもよい。この場合は、情 報光用空間変調パターンと参照光用空間変調パターンを対物レンズ 221の入射瞳 面において結像させる必要があるため、情報光を生成する空間光変調器と参照光を 生成する空間光変調器を共役な関係とし、一対のリレーレンズ 213、 215によって対 物レンズ 221の入射瞳面に伝搬させる。 [0088] The recording reference light may be spatially modulated or may not be spatially modulated. When the recording reference light is spatially modulated, multiple recording can be performed by changing the spatial modulation pattern of the recording reference light, and information recording can be performed by keeping the spatial modulation pattern of the recording reference light as a key. Security against unauthorized access can be improved. When the reference light is spatially modulated, for example, the spatial light modulator displaying the reference light spatial modulation pattern is irradiated with light to generate the reference light spatially modulated by the reference light spatial modulation pattern. it can. When the information light and the recording reference light are generated by one spatial light modulator 209, an information light region and a reference light region are provided on the display surface of the spatial light modulator 209, respectively. The pattern and the spatial modulation pattern for recording reference light may be displayed. The information light region is preferably arranged near the center of the spatial light modulator 209, and the reference light region is preferably arranged in an annular shape so as to surround the information light region. A spatial light modulator that generates information light and recording reference light may be provided separately. For example, the light from the light source 203 is split by a beam splitter or the like, and one light is Information light may be spatially modulated by one spatial light modulator, and reference light may be generated by spatially modulating the other light by a second spatial light modulator. In this case, since the information light spatial modulation pattern and the reference light spatial modulation pattern need to be imaged on the entrance pupil plane of the objective lens 221, the spatial light modulator that generates the information light and the reference light are generated. The spatial light modulator has a conjugate relationship, and is propagated to the entrance pupil plane of the object lens 221 by the pair of relay lenses 213 and 215.
[0089] 空間光変調器 209の複数の画素が格子状に配列されて 、る場合、空間光変調器 209から出射する出射光 23の光軸は、複数の画素による格子の対角方向について の回折次数をずらすと、図 3の配置成分パターン 31aに示したように、フーリエ面にお ける輝点の対角方向に光軸が移動するので、光軸力 近接する各輝点までの距離 を均等化し易いので好ましい。特に、出射光 23の光軸の出射角が、画素による格子 の対角方向についての(m±0. 5)次の回折角と等しくすると、近接する 4つの輝点ま での距離が等しくなり、フーリエ変換像の強度を平坦ィ匕することができる。なお、空間 光変調器 209の複数の画素が格子状ではない配列、例えば蜂の巣のように段違い にずらして配列させた場合、であっても、光軸を m次の回折光と一致しないようにする ことで、フーリエ変換像における強度の強い領域に複数の輝点を配置させることがで きる。なお、配列を変更すると、図 3における配置成分パターン 31aが変更されること になる。 [0089] In the case where a plurality of pixels of the spatial light modulator 209 are arranged in a lattice pattern, the optical axis of the outgoing light 23 emitted from the spatial light modulator 209 is about the diagonal direction of the lattice of the plurality of pixels. When the diffraction order is shifted, the optical axis moves in the diagonal direction of the bright spot on the Fourier plane as shown in the arrangement component pattern 31a in FIG. 3, so the distance to each bright spot close to the optical axis force This is preferable because it is easy to equalize. In particular, if the exit angle of the optical axis of the emitted light 23 is equal to the (m ± 0.5) order diffraction angle in the diagonal direction of the grating by the pixel, the distances to four adjacent bright spots will be equal. The intensity of the Fourier transform image can be flattened. Even when the plurality of pixels of the spatial light modulator 209 are arranged in a non-lattice arrangement, for example, a honeycomb and shifted in a stepwise manner, the optical axis does not coincide with the m-th order diffracted light. As a result, a plurality of bright spots can be arranged in a strong region in the Fourier transform image. When the arrangement is changed, the arrangement component pattern 31a in FIG. 3 is changed.
[0090] 空間光変調器 209の複数の画素は、正方形状以外の形状であってもよい。例えば 、長方形、菱形、六角形、三角形、円形の場合であってもよい。この場合、図 3の形状 成分パターン 31bが形状に合わせて変化する。 [0090] The plurality of pixels of the spatial light modulator 209 may have a shape other than a square shape. For example, it may be a rectangle, rhombus, hexagon, triangle, or circle. In this case, the shape component pattern 31b in FIG. 3 changes according to the shape.
[0091] 偏光ビームスプリッタ 211は、直線偏光 (例えば P偏光)を反射または透過し、当該 偏光に垂直な直線偏光 (例えば S偏光)を透過または反射するような半反射面を有し ている。図 18において、偏光ビームスプリッタ 211は、空間光変調器 209から射出さ れた情報光、記録用参照光または再生用参照光を透過し、記録媒体のホログラム記 録層から発生した再生光および記録媒体によって反射された再生用参照光を光検 出手段 225に向けて反射する。 The polarization beam splitter 211 has a semi-reflective surface that reflects or transmits linearly polarized light (for example, P-polarized light) and transmits or reflects linearly polarized light (for example, S-polarized light) perpendicular to the polarized light. In FIG. 18, a polarization beam splitter 211 transmits information light, recording reference light, or reproduction reference light emitted from the spatial light modulator 209, and reproduces and records the reproduction light generated from the hologram recording layer of the recording medium. The reproduction reference light reflected by the medium is reflected toward the light detection means 225.
[0092] 一対のリレーレンズ 213、 215は、空間光変調器 209から対物レンズ 221までの間
に配置されており、空間光変調器 209に表示された像を対物レンズ 221の入射瞳面 に結像するように配置されている。すなわち、空間光変調器 209から第 1のリレーレン ズ 213までの距離が第 1のリレーレンズ 213の焦点距離 flとなり、第 2のリレーレンズ 215から対物レンズ 221の入射瞳面までの距離が第 2のリレーレンズ 215の焦点距 離 f2となり、第 1および第 2のリレーレンズ 213、 215間の距離が第 1のリレーレンズ 2 13の焦点距離 flと第 2のリレーレンズ 215の焦点距離 f2の和となるように配置されて いる。 [0092] The pair of relay lenses 213 and 215 are arranged between the spatial light modulator 209 and the objective lens 221. The image displayed on the spatial light modulator 209 is formed on the entrance pupil plane of the objective lens 221. That is, the distance from the spatial light modulator 209 to the first relay lens 213 is the focal length fl of the first relay lens 213, and the distance from the second relay lens 215 to the entrance pupil plane of the objective lens 221 is the second distance The distance between the first and second relay lenses 213 and 215 is the sum of the focal length fl of the first relay lens 213 and the focal length f2 of the second relay lens 215. It is arranged to become.
[0093] また、図 18において、一対のリレーレンズ 213、 215は、対物レンズ 221から光検出 手段 225までの間に配置されており、再生用の参照光によって記録媒体 251のホロ グラム記録層 253から発生した再生光の対物レンズ 221の射出瞳面における像を再 び光検出手段 225において結像するように配置されている。すなわち、対物レンズ 2 21の射出瞳面力も第 2のリレーレンズ 215までの距離が焦点距離 f2となり、第 1のリ レーレンズ 213から光検出手段 225までの距離が焦点距離 flとなり、第 1および第 2 のリレーレンズ 213、 215間の距離が焦点距離 flと焦点距離 f2の和となるように配置 されている。 In FIG. 18, a pair of relay lenses 213 and 215 are arranged between the objective lens 221 and the light detection means 225, and the hologram recording layer 253 of the recording medium 251 is read by reference light for reproduction. The light detection means 225 is arranged again to form an image on the exit pupil plane of the objective lens 221 of the reproduction light generated from the light. That is, the exit pupil surface force of the objective lens 221 is also the distance to the second relay lens 215 is the focal length f2, the distance from the first relay lens 213 to the light detecting means 225 is the focal length fl, and the first and first The second relay lenses 213 and 215 are arranged such that the distance between them is the sum of the focal length fl and the focal length f2.
[0094] なお、一対のリレーレンズ 213、 215の配置は、他の光学素子を適宜配置すること で変化する。例えば、第 1のリレーレンズ 213から光検出手段 225までの間に拡大レ ンズを配置すれば、第 1のリレーレンズ 213と拡大レンズの入射瞳面までの距離が焦 点距離 flとなるように配置される。 [0094] Note that the arrangement of the pair of relay lenses 213 and 215 changes by appropriately arranging other optical elements. For example, if a magnifying lens is placed between the first relay lens 213 and the light detection means 225, the distance from the first relay lens 213 to the entrance pupil plane of the magnifying lens is the focal distance fl. Be placed.
[0095] 開口 227は、第 1および第 2のリレーレンズ 213、 215間の焦点位置に配置されて おり、高次の回折光を取り除くものである。開口 227の大きさによって、ホログラムの 記録領域の大きさを調節することができる。本発明においては、空間光変調器 209 力 の出射光 232の光軸力 m次(m=0, ± 1, ± 2· ··)の回折光 233と一致しないよ うに構成されているため、ホログラムの記録領域を小さくすることができる。さらに、基 準マークの領域内における空間周波数が、空間光変調器の基本空間周波数よりも 小さい空間周波数を含むため、ホログラムの記録領域を小さくしても再生することが できる。よって、開口 227を小さくしてホログラムの記録領域を小さくしてもよい。図 18 において、出射光 232の光軸が m+O. 5次の回折光の進行方向と一致する場合、
その近傍の m次と m+ 1次の回折光 233を通過させ、それ以上の次数が離れた回折 光は遮断するようにしてもよい。なお、ホログラムの記録領域を調節する手段として、 開口 227に限定されるものではない。 The aperture 227 is disposed at the focal position between the first and second relay lenses 213 and 215, and removes higher-order diffracted light. Depending on the size of the opening 227, the size of the recording area of the hologram can be adjusted. In the present invention, since it is configured not to coincide with the diffracted light 233 of the optical axis force m order (m = 0, ± 1, ± 2...) Of the outgoing light 232 of the spatial light modulator 209 force, The recording area of the hologram can be reduced. Furthermore, since the spatial frequency in the area of the reference mark includes a spatial frequency smaller than the basic spatial frequency of the spatial light modulator, it can be reproduced even if the hologram recording area is reduced. Therefore, the opening 227 may be reduced to reduce the hologram recording area. In Fig. 18, when the optical axis of outgoing light 232 matches the traveling direction of m + O. 5th order diffracted light, The m-order and m + 1 first-order diffracted light 233 in the vicinity thereof may be passed, and diffracted light having a higher order may be blocked. The means for adjusting the recording area of the hologram is not limited to the opening 227.
[0096] ミラー 217は、光の進行方向を対物レンズ 221に向けて反射するものであり、光学 系の構成によっては不要である。 The mirror 217 reflects the traveling direction of light toward the objective lens 221 and is not necessary depending on the configuration of the optical system.
[0097] 4分の 1波長板 219は、互いに垂直な方向に振動する偏光の光路差を 4分の 1波長 変化させる位相板である。 4分の 1波長板 219によって P偏光の光は円偏光に変化さ れ、更に、この円偏光の光が 4分の 1波長板 219を通過すると S偏光に変化されること になる。この 4分の 1波長板 219によって、再生時における再生用の参照光と再生光 を偏光ビームスプリッタ 211で分離することができる。 The quarter-wave plate 219 is a phase plate that changes the optical path difference of polarized light that vibrates in directions perpendicular to each other by a quarter wavelength. P-polarized light is converted to circularly polarized light by the quarter-wave plate 219, and further, when this circularly polarized light passes through the quarter-wave plate 219, it is changed to S-polarized light. By this quarter-wave plate 219, the reference beam for reproduction and the reproduction beam at the time of reproduction can be separated by the polarization beam splitter 211.
[0098] 対物レンズ 221は、記録時においては、入射瞳面に結像した情報光および記録用 参照光を記録媒体 251に照射し、ホログラム記録層 253にお 、て干渉させて記録す るものであり、また再生時においては、入射瞳面に結像した再生用参照光を記録媒 体 251に照射し、記録媒体 251のホログラム記録層 253から発生した再生光を入射 して射出瞳面に結像させるものである。図 18では対物レンズ 221として、一枚のレン ズで示しているが、複合レンズを使用してもよい。 [0098] At the time of recording, the objective lens 221 irradiates the recording medium 251 with information light and recording reference light imaged on the entrance pupil plane, and causes the hologram recording layer 253 to interfere and record. At the time of reproduction, the reproduction reference light imaged on the entrance pupil plane is irradiated onto the recording medium 251 and the reproduction light generated from the hologram recording layer 253 of the recording medium 251 is incident on the exit pupil plane. The image is formed. In FIG. 18, the objective lens 221 is shown as a single lens, but a compound lens may be used.
[0099] リングマスク 223は、再生時に、再生光と一緒に記録媒体 251の反射層 255で反射 された再生用参照光を除去するためのものである。 The ring mask 223 is for removing reproduction reference light reflected by the reflective layer 255 of the recording medium 251 together with reproduction light during reproduction.
[0100] 光検出手段 225は、複数の受光画素を有し、各受光画素毎に受光した光の強度を 検出できるようになつている。光検出手段 225としては、 CCD型固体撮像素子や M OS型固体撮像素子を用いることができる。また、光検出手段 225として、 MOS型固 体撮像素子と信号処理回路とが 1チップ上に集積されたスマート光センサ (例えば、 WO plus E, 1996 9月, No. 202, 93〜99ページ」 :照、。)を用!/、てち 、 。このスマート光センサは、転送レートが大きぐ高速な演算機能を有するので、この スマート光センサを用いることにより、高速な再生が可能となり、例えば、 G (ギガ)ビッ ト Z秒オーダの転送レートで再生を行うことが可能となる。 [0100] The light detection means 225 has a plurality of light receiving pixels, and can detect the intensity of light received for each light receiving pixel. As the light detection means 225, a CCD solid-state image sensor or a MOS type solid-state image sensor can be used. In addition, as the light detection means 225, a smart optical sensor in which a MOS type solid-state imaging device and a signal processing circuit are integrated on one chip (for example, WO plus E, September 1996, No. 202, pages 93 to 99) : Shine ,.) use! /, Techi,. This smart optical sensor has a high transfer function with a large transfer rate, so it can be played back at high speed by using this smart optical sensor, for example, with a transfer rate on the order of G (giga) bits Z seconds. Playback can be performed.
[0101] 記録媒体 251は、干渉縞が記録されるホログラム記録層 253を有しており、図 18に おいては、更に、第 1基板 251a、反射層 255および第 2透明基板 251bを備えている
。記録媒体 251としては、ディスク状やカード状のものを使用することができ、記録媒 体 251を回転させながら記録および再生してもいいし、記録および再生の時には固 定されていてもよい。記録媒体 251として、ディスク状の記録媒体を使用し、回転させ つつ記録再生を行う方式の場合は、 CDドライブや DVDドライブにお ヽて使用されて いるディスク駆動機構を使用することができ、更には、 CDドライブや DVDドライブと の互換性を持たせることも容易になるので好ま 、。 [0101] The recording medium 251 has a hologram recording layer 253 on which interference fringes are recorded. In FIG. 18, the recording medium 251 further includes a first substrate 251a, a reflective layer 255, and a second transparent substrate 251b. Have . As the recording medium 251, a disk-shaped or card-shaped one can be used, and recording and reproduction may be performed while the recording medium 251 is rotated, or may be fixed at the time of recording and reproduction. In the case of using a disk-shaped recording medium as the recording medium 251 and performing recording and reproduction while rotating, the disk drive mechanism used in CD drives and DVD drives can be used. Is preferred because it makes it easier to have compatibility with CD and DVD drives.
[0102] また、記録媒体 251に、位置決め用の情報を予め記録しておき、照射位置の位置 決めにフィードバック機構を採用すると、より正確な位置決めを行うことができるので 好ましい。例えば、記録媒体 251の反射層 255の表面に位置決め用の情報としてピ ットを形成し、位置決め用の情報を予め記録してもよい。なお、位置決め情報を読み 取る光として、記録または再生用の光とは異なる波長の光を使用する場合は、ピット を形成した位置決め情報を読み取る光に対する反射層とは別に、記録または再生用 の光を反射する波長選択反射層を設けてもよい。例えば、反射層とホログラム記録層 との間に、記録または再生用の光を反射し、位置決め情報を読み取る光を透過する 波長選択反射層を形成すれば、記録再生領域に重畳して位置決め情報を記録する ことができ、更に記録媒体の同一面側にピックアップ装置を配置できるので記録再生 装置を小型化することができる。 [0102] It is preferable that information for positioning is recorded in advance on the recording medium 251 and a feedback mechanism is used for positioning of the irradiation position because more accurate positioning can be performed. For example, a pit may be formed as positioning information on the surface of the reflective layer 255 of the recording medium 251 and the positioning information may be recorded in advance. When light with a wavelength different from that for recording or reproduction is used as the light for reading positioning information, the light for recording or reproduction is separated from the reflection layer for the light for reading the positioning information forming the pits. A wavelength selective reflection layer that reflects light may be provided. For example, if a wavelength selective reflection layer that reflects light for recording or reproduction and transmits light for reading positioning information is formed between the reflective layer and the hologram recording layer, the positioning information is superimposed on the recording / reproducing area. Recording can be performed, and the pickup device can be arranged on the same side of the recording medium, so that the recording / reproducing apparatus can be downsized.
[0103] 光情報記録装置としての動作を説明すると、光源 203から射出した光は、コリメータ レンズ 205によって平行光とされ、ミラー 207によって空間光変調器 209に向けて反 射される。そして、空間光変調器 209に表示された情報光用空間変調パターンおよ び参照光用空間変調パターンによって情報光および記録用の参照光が生成される 。本発明の光情報記録方法においては、情報光用空間変調パターンは複数の基準 マークを有し、基準マークの領域内における空間周波数が、空間光変調器 209の基 本空間周波数よりも小さい空間周波数を含むようにする。さらに、空間光変調器 209 力 対物レンズへ向力う光の光軸(図では中央の光線)は、 m次の回折光 233の進行 方向と一致しないように配置される。また、図 18において、中心部分に情報光が配置 され、その周囲に環状の記録用参照光が配置されるので、情報光の光軸および記録 用参照光の光軸は、同一線上に位置しており m次の回折光 233の進行方向と一致
していない。 The operation of the optical information recording apparatus will be described. Light emitted from the light source 203 is converted into parallel light by the collimator lens 205 and reflected by the mirror 207 toward the spatial light modulator 209. Information light and recording reference light are generated by the information light spatial modulation pattern and the reference light spatial modulation pattern displayed on the spatial light modulator 209. In the optical information recording method of the present invention, the spatial modulation pattern for information light has a plurality of reference marks, and the spatial frequency in the region of the reference mark is smaller than the basic spatial frequency of the spatial light modulator 209. To include. Further, the optical axis of light directed toward the spatial light modulator 209 force objective lens (the central ray in the figure) is arranged so as not to coincide with the traveling direction of the m-th order diffracted light 233. In FIG. 18, since the information light is arranged at the center and the annular recording reference light is arranged around it, the optical axis of the information light and the optical axis of the recording reference light are located on the same line. Coincides with the traveling direction of m-order diffracted light 233 Not done.
[0104] 情報光および記録用参照光は、偏光ビームスプリッタ 211を通過して、一対のリレ 一レンズ 213、 215によって、対物レンズ 221の入射瞳面に空間光変調器 209に表 示された空間変調パターンが結像するように伝搬される。その途中、開口 227によつ て、高次の回折光は取り除かれ、ミラー 217によって対物レンズ 221に向けて反射さ れ、 4分の 1波長板 219を通過する。記録媒体 251のホログラム記録層 253に情報光 および記録用参照光の干渉縞が記録される。 [0104] The information light and the recording reference light pass through the polarization beam splitter 211, and are displayed on the spatial light modulator 209 on the entrance pupil plane of the objective lens 221 by the pair of relay lenses 213 and 215. The modulation pattern is propagated to form an image. On the way, high-order diffracted light is removed by the aperture 227, reflected by the mirror 217 toward the objective lens 221, and passes through the quarter-wave plate 219. Interference fringes of information light and recording reference light are recorded on the hologram recording layer 253 of the recording medium 251.
[0105] このように本発明の記録方法によって干渉縞が記録された記録媒体は、再生時に お!、て、ホログラムサイズが小さくしても基準マークを再生して情報を再生することが できるので、情報記録媒体としての信頼性が向上し、また記録容量も向上する。 [0105] Thus, the recording medium on which the interference fringes are recorded by the recording method of the present invention can reproduce information by reproducing the reference mark even when the hologram size is small! Therefore, the reliability as an information recording medium is improved, and the recording capacity is also improved.
[0106] 更に、光情報再生装置としての動作を説明すると、光源 203から射出した光は、コリ メータレンズ 205によって平行光とされ、ミラー 207によって空間光変調器 209に向 けて反射される。そして、空間光変調器 209に表示された参照光用空間変調パター ンによって再生用参照光が生成される。なお、再生時における再生用参照光の参照 光用空間変調パターンは、記録媒体に記録された情報が記録される際に照射された 記録用参照光の参照光用空間変調パターンである。ここで、空間光変調器 209から 対物レンズへ向力う光の光軸(図では中央の光線)は、 m次の回折光 233の進行方 向と一致しない。また、図 18において、環状の再生用参照光が配置され、その光軸 は、 m次の回折光 233の進行方向と一致していない。 Further, the operation as the optical information reproducing apparatus will be described. The light emitted from the light source 203 is converted into parallel light by the collimator lens 205 and reflected by the mirror 207 toward the spatial light modulator 209. Then, the reference light for reproduction is generated by the spatial modulation pattern for reference light displayed on the spatial light modulator 209. Note that the reference light spatial modulation pattern of the reproduction reference light at the time of reproduction is a reference light spatial modulation pattern of the recording reference light irradiated when information recorded on the recording medium is recorded. Here, the optical axis of light directed from the spatial light modulator 209 to the objective lens (the central ray in the figure) does not coincide with the traveling direction of the m-th order diffracted light 233. In FIG. 18, an annular reproduction reference beam is arranged, and its optical axis does not coincide with the traveling direction of the mth-order diffracted beam 233.
[0107] 空間光変調器 209から射出した再生用参照光は、偏光ビームスプリッタ 211を通過 して、一対のリレーレンズ 213、 215によって、対物レンズ 221の入射瞳面に空間光 変調器 209に表示された参照光用空間変調パターンが結像するように伝搬される。 その途中、開口 227によって、高次の回折光は取り除かれ、ミラー 217によって対物 レンズ 221に向けて反射され、 4分の 1波長板 219を通過する。そして、対物レンズ 2 21によって記録媒体 251に照射され、記録媒体 251のホログラム記録層 253に記録 された干渉縞によって回折され、記録時における情報光と同じ情報を有する再生光 を発生する。 The reproduction reference light emitted from the spatial light modulator 209 passes through the polarization beam splitter 211 and is displayed on the spatial light modulator 209 on the entrance pupil plane of the objective lens 221 by the pair of relay lenses 213 and 215. The transmitted spatial modulation pattern for reference light is propagated so as to form an image. On the way, high-order diffracted light is removed by the aperture 227, reflected by the mirror 217 toward the objective lens 221, and passes through the quarter-wave plate 219. Then, the recording medium 251 is irradiated by the objective lens 221 and is diffracted by the interference fringes recorded on the hologram recording layer 253 of the recording medium 251 to generate reproduction light having the same information as the information light at the time of recording.
[0108] 再生光は、記録媒体 251の反射層 255に反射して記録媒体 251から対物レンズ 2
21に向力つて射出し、対物レンズ 221によってその射出瞳面に情報光用空間変調 ノターンを結像させ、力かる像を光検出手段 255に再び結像されるように一対のリレ 一レンズ 215、 213によって伝搬される。その間に、再生光は、 4分の 1波長板 219を 通過し、ミラー 217によって偏光ビームスプリッタ 211に向けて反射される。再生光は 、照射時の再生用の参照光と比べて 4分の 1波長板 219を 2回通過しているので偏 光方向が 90° ずれているため、偏光ビームスプリッタ 211によって、光検出手段 255 に向けて反射される。そして、リングマスク 223によって再生用参照光が除去され、再 生光の空間変調パターンが光検出手段 225において検出される。検出された情報 は、制御手段(図示せず)に送られ、制御手段においてデコードされ情報を再生する なお、本発明は、前述した実施の形態に限定されるものではなぐ必要に応じて種 々の変更が可能である。例えば、図 18においては、情報光の光軸と参照光の光軸と が同軸となるように、記録媒体の同一面側力 情報光と参照光を記録媒体に照射し て、ホログラムを形成したが、情報光の光軸と参照光の光軸とが一定の角度で交差 するように情報光と参照光を記録媒体に照射して、二光束干渉型のホログラムを形 成してもよい。この場合、空間光変調器によって空間的に変調した光の少なくとも一 つについて、上述したとおり、空間光変調器からの出射光が m次の回折光と一致し な 、ように構成することが好ま 、。
[0108] The reproduction light is reflected by the reflection layer 255 of the recording medium 251 and is reflected from the recording medium 251 to the objective lens 2. A pair of relay lenses 215 are emitted so as to form a spatial modulation pattern for information light on the exit pupil plane by the objective lens 221 so that a powerful image is formed again on the light detection means 255. , 213. In the meantime, the reproduction light passes through the quarter-wave plate 219 and is reflected by the mirror 217 toward the polarization beam splitter 211. Since the reproduction light passes through the quarter-wave plate 219 twice compared to the reproduction reference light at the time of irradiation, the polarization direction is shifted by 90 °. Reflected toward 255. Then, the reproduction reference light is removed by the ring mask 223, and the spatial modulation pattern of the reproduction light is detected by the light detection means 225. The detected information is sent to a control means (not shown), and the control means decodes and reproduces the information. Note that the present invention is not limited to the above-described embodiment, and various kinds are necessary as necessary. Can be changed. For example, in FIG. 18, a hologram is formed by irradiating the recording medium with the same surface side force information light and the reference light of the recording medium so that the optical axis of the information light and the optical axis of the reference light are coaxial. However, a two-beam interference type hologram may be formed by irradiating the recording medium with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light intersect at a certain angle. In this case, it is preferable that at least one of the light spatially modulated by the spatial light modulator is configured such that the light emitted from the spatial light modulator does not coincide with the mth-order diffracted light as described above. ,.
Claims
[1] 記録用参照光と、複数の画素を有する空間光変調器に表示された情報光用空間 変調パターンによって空間的に変調された情報光とを対物レンズによって記録媒体 に対して収束するように照射して前記記録媒体のホログラム記録層における前記記 録用参照光と前記情報光との干渉縞を記録する光情報記録方法において、 前記空間光変調器から前記対物レンズに向かう前記情報光の光軸が、前記空間 光変調器によって回折される m次 (m=0, ± 1, ± 2· ··)の回折光と一致せず、 前記情報光用空間変調パターンは複数の基準マークを含み、前記基準マークの 領域内における空間周波数が、前記空間光変調器の基本空間周波数よりも小さい 空間周波数を含むことを特徴とする光情報記録方法。 [1] The reference light for recording and the information light spatially modulated by the spatial modulation pattern for information light displayed on the spatial light modulator having a plurality of pixels are converged on the recording medium by the objective lens. In the optical information recording method for recording interference fringes between the recording reference light and the information light in the hologram recording layer of the recording medium, the information light directed from the spatial light modulator toward the objective lens The optical axis does not coincide with the mth order (m = 0, ± 1, ± 2 ...) diffracted light diffracted by the spatial light modulator, and the spatial modulation pattern for information light has a plurality of reference marks. An optical information recording method comprising: a spatial frequency in a region of the reference mark including a spatial frequency smaller than a basic spatial frequency of the spatial light modulator.
[2] 前記情報光の光軸の方向は、 (m+O. 2)次乃至 (m+O. 8)次の回折光の進行方 向の範囲内であることを特徴とする請求項 1に記載の光情報記録方法。 [2] The direction of the optical axis of the information light is in the range of the traveling direction of the (m + O. 2) th to (m + O. 8) th diffracted light. The optical information recording method according to 1.
[3] 前記空間光変調器は、前記複数の画素が格子状に配置されており、前記情報光 の光軸の方向は、前記複数の画素による格子の対角方向についての約 (m+O. 5) 次の回折光の進行方向と一致することを特徴とする請求項 1に記載の光情報記録方 法。 [3] In the spatial light modulator, the plurality of pixels are arranged in a grid pattern, and an optical axis direction of the information light is approximately (m + O) with respect to a diagonal direction of the grid formed by the plurality of pixels. 5. The optical information recording method according to claim 1, wherein the optical information recording method coincides with the traveling direction of the next diffracted light.
[4] 前記基準マークの領域内における空間周波数が、前記空間光変調器の基本空間 周波数の半分の空間周波数を含むことを特徴とする請求項 1乃至 3の何れか 1項に 記載の光情報記録方法。 [4] The optical information according to any one of [1] to [3], wherein a spatial frequency in a region of the reference mark includes a spatial frequency that is half of a basic spatial frequency of the spatial light modulator. Recording method.
[5] 前記基準マークは属性の異なる画素を交互に配置したパターンを含むことを特徴と する請求項 1乃至 3の何れか 1項に記載の光情報記録方法。 5. The optical information recording method according to any one of claims 1 to 3, wherein the reference mark includes a pattern in which pixels having different attributes are alternately arranged.
[6] 前記情報光の光軸の方向は、前記空間光変調器に対して垂直であることを特徴と する請求項 1乃至 5の何れか 1項に記載の光情報記録方法。 6. The optical information recording method according to any one of claims 1 to 5, wherein an optical axis direction of the information light is perpendicular to the spatial light modulator.
[7] 請求項 1乃至 6の何れか 1項に記載の光情報記録方法によってホログラム記録層に 干渉縞が記録されたことを特徴とする記録媒体。
[7] A recording medium, wherein interference fringes are recorded on the hologram recording layer by the optical information recording method according to any one of [1] to [6].
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WO2006123732A1 (en) * | 2005-05-18 | 2006-11-23 | Optware Corporation | Recording medium, optical information recording method, optical information recording device, optical information reproducing method, optical information reproducing device and recording medium manufacturing method |
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