JP2000268380A - Method and device for optical recording, and method and device for optical reproducing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make alignable an optical system to an optical storage medium even without adding an alignment pattern to all pages of signal light, and thereby increase the storage capacity and improve the data transfer speed. SOLUTION: First, signal light 5 of P polarization for retaining data information according to space intensity distribution and including an alignment pattern is obtained, and a hologram is recorded into an optical storage medium 10 by reference light 6 of P polarization. Then, the signal light 5 is broken, reading light 6 of S polarization is applied to the optical storage medium 10, the first hologram is reproduced as diffraction light 8 of S polarization, its intensity is detected by a photo detector 53s, and the recording/reproducing head 20 is aligned to the optical storage medium 10 based on the detection signal of the alignment pattern included in the first hologram. In this state, data information is retained according to the space intensity distribution as the signal light 5 of P polarization, one without including the alignment pattern is obtained, and a second hologram is recorded by making multiplex the second hologram onto the first hologram in a region where the first hologram of the optical storage medium 10 is recorded by the reference light 6 of S polarization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for recording two-dimensional data information as a hologram on an optical recording medium and reproducing it from the optical recording medium.

[0002]

2. Description of the Related Art Rewritable optical disks such as a phase change type and a magneto-optical type are already widely used. These optical disks have a higher recording density than ordinary magnetic disks, but in order to further increase the recording density, it is necessary to reduce the beam spot diameter and shorten the distance between adjacent tracks or adjacent bits. There is.

A DVD that has been put into practical use by the development of such a technique is DVD. Read-only DVD-RO
M is 4.7 GByte on one side on a 12 cm diameter disk
e can be recorded. In addition,
An erasable DVD-RAM uses a phase change method.
High-density recording of 5.2 GByte is possible on both sides of a disk having a diameter of 12 cm.

As described above, the density of optical disks has been increasing year by year. On the other hand, since the above-mentioned optical disks record data in a plane, the recording density is limited to the diffraction limit of light. 5Gbit / i called physical limit
Approaching nch ² . Therefore, in order to further increase the capacity, three-dimensional (volume type) recording including the depth direction is required.

Therefore, as a next-generation computer file memory, large capacity derived from a three-dimensional recording area and 2
A hologram memory that has high speed derived from the one-dimensional batch recording / reproducing method has attracted attention.

In a hologram memory, a plurality of data pages can be recorded in a multiplexed manner in the same volume, and data can be read out collectively for each page. Instead of an analog image, the binary digital data “0, 1” is converted into a digital image as “bright, dark” and recorded and reproduced as a hologram, so that digital data can be recorded and reproduced. Recently, specific optical systems of this digital hologram memory system, evaluation of SN ratio and bit error rate based on volume multiplex recording, or proposal of two-dimensional encoding have been proposed, and the influence of aberration of the optical system has been proposed. Research from a more optical point of view is also progressing.

FIG. 6 shows a document “D. Psaltis, M .;
Levene, A .; Pu, G .; Barbastathi
s and K.S. Curtis; Opt. Lett. 2
0 (1995) 782 ", which is an example of the volume multiplex recording method.

In the shift multiplex recording method disclosed in this document, a hologram recording medium 91 is formed in a disk shape, and an object beam 93 obtained through a spatial light modulator 92 is transmitted to a lens 9.
4 and the hologram recording medium 91
Simultaneously, the hologram recording medium 91 is irradiated with the reference light 96 of the spherical wave obtained through the objective lens 95, and a plurality of holograms are overwritten in the same region by the rotation of the hologram recording medium 91. For example, assuming that the beam diameter is 1.5 mmφ, another hologram can be recorded in almost the same area without crosstalk by moving the hologram recording medium 91 by several tens of μm. This utilizes the fact that the reference light 96 is a spherical wave, which is equivalent to the change in the angle of the reference light 96 due to the movement of the hologram recording medium 91.

By rotating the optical recording medium in a disk shape as described above, a hologram can be recorded / reproduced in the two-dimensional direction on the surface of the medium, and the storage capacity can be increased and the data transfer speed can be improved.

However, when recording / reproducing a hologram in the two-dimensional direction of the medium surface as described above, an optical system for recording / reproduction is used in both a tracking direction horizontal to the medium surface and a focusing direction perpendicular to the medium surface. If the relative positions of the optical recording medium and the optical recording medium are not accurately adjusted, the SN ratio for recording and reproduction is reduced. In particular, a signal to be recorded and reproduced is two-dimensional data information as shown in FIG. 5A, and since each pixel has a size of about several tens of μm at most, high-precision alignment is required. .

[0011] Therefore, as shown in FIG. 5B, m × n at each of the four corners in the signal light of the M × N pixel of each page.
A hologram is recorded by adding a positioning pattern Pa to the pixel portion, and the relative position between the optical system and the optical recording medium is determined by a detection signal of the positioning pattern Pa portion in the hologram diffracted light at the time of reading. There is a method of controlling the control.

[0012]

However, in this method, four out of the available M × N pixels in each page are used.
× m × n pixels cannot be used for recording / reproducing data information, resulting in a decrease in storage capacity and a decrease in data transfer speed. In addition, the two-dimensional spatial light modulator for forming a signal light at the time of recording and the two-dimensional photodetector for detecting a diffracted light at the time of reproduction also serve as data information of (M × N−4 × m × n) pixels. In this case, M × N pixels are required for recording / reproducing, and the cost of the spatial light modulator and the photodetector is increased, and the cost of the recording / reproducing apparatus is increased.

Therefore, according to the present invention, the optical system and the optical recording medium can be aligned without adding an alignment pattern to every page of the signal light, thereby increasing the recording capacity and increasing the recording capacity. The data transfer speed can be improved, and the cost of the recording / reproducing apparatus can be reduced.

[0014]

According to the optical recording method of the present invention, two-dimensional data information is held by a spatial intensity distribution, and a first signal light including a positioning pattern is used as a first hologram. It is recorded on a recording medium, and then the diffracted light is reproduced from the recorded first hologram to detect the alignment pattern, and the relative position between the signal light and the optical recording medium is determined by the detection signal. In the controlled state, the two-dimensional data information is held by the spatial intensity distribution, and the second signal light not including the alignment pattern is used as the reference light or the polarization angle of the signal light when recording the first hologram. Is changed, and a second hologram is recorded in an area of the optical recording medium where the first hologram is recorded.

According to the optical reproducing method of the present invention, two pages of signal light, each of which holds two-dimensional data information by a spatial intensity distribution and in which a positioning pattern is added to only one page, is referred to for each page. The polarization angle of the light or the signal light is changed, and the optical recording medium recorded in the same area as the hologram is irradiated with the reading light,
Simultaneously reproducing the diffracted light from the holograms for the two pages, detecting the alignment pattern from the diffracted light, and controlling the relative position between the readout light and the optical recording medium by the detection signal, The two-dimensional data information of each page is separated and read from the diffracted light.

[0016]

A material exhibiting light-induced birefringence (light-induced anisotropy, light-induced dichroism) is sensitive to the polarization state of light incident thereon and records the polarization angle (polarization direction) of the incident light. be able to. For example, a polymer having a group that photoisomerizes in a side chain or a polymer liquid crystal, or a polymer in which a molecule that photoisomerizes is dispersed, is irradiated with linearly polarized light, photoisomerization is induced, and linearly polarized light is irradiated. Anisotropy of the refractive index occurs depending on the direction, and the polarization direction can be recorded and stored. At this time, by simultaneously irradiating the reference light, the polarization angle of the signal light can be recorded as a hologram.

A normal hologram is recorded with the signal light (object light) and the reference light having the same (parallel) polarization direction. The hologram recorded or recorded in this way is referred to as an intensity-modulated hologram in this specification.

On the other hand, the above-mentioned material exhibiting light-induced birefringence can record the signal light as a hologram by making the polarization directions of the signal light and the reference light orthogonal. The hologram recorded or recorded in this way is referred to as a polarization modulation hologram in this specification. However, the polarization-modulated hologram can be spatially modulated in accordance with two-dimensional data information, similarly to the intensity-modulated hologram.

For example, P-polarized signal light can be recorded as an intensity-modulated hologram by P-polarized reference light, and can be recorded as a polarization-modulated hologram by S-polarized reference light. The P-polarized signal light recorded as the intensity-modulated hologram can be reproduced as S-polarized diffracted light by the S-polarized readout light.
The polarized signal light can be reproduced as P-polarized diffracted light by S-polarized readout light. At the time of recording, instead of changing the polarization angle of the reference light, the polarization angle of the signal light may be changed.

Utilizing this, in the optical recording method of the present invention, first, two-dimensional data information is held by a spatial intensity distribution, and a first signal light including a positioning pattern is converted to a first hologram. For example, it is recorded on an optical recording medium as an intensity modulation type hologram.

Next, the recorded first hologram,
For example, by reproducing the diffracted light from the intensity-modulated hologram,
The alignment pattern is detected, and the relative position between the signal light and the optical recording medium is controlled by the detection signal. For example, if the intensity-modulated hologram as the first hologram is the one in which the P-polarized signal light is recorded by the P-polarized reference light, the S-polarized readout light can provide the S-polarized hologram diffracted light. , The alignment pattern can be detected.

In the state where the signal light and the optical recording medium are aligned as described above, next, the second signal light holding the two-dimensional data information by the spatial intensity distribution and not including the alignment pattern is formed. At the time of recording the first hologram, the polarization angle of the reference light or the signal light is changed, and the first hologram of the optical recording medium, for example, an intensity modulation hologram is recorded as a second hologram, for example, as a polarization modulation hologram. Record in the area that has been set.

Therefore, only by adding the alignment pattern only to the page of the signal light to be recorded first, two pages of the signal light can be recorded as holograms in the same area of the optical recording medium.

After multiplexed recording in this way, the intensity modulation hologram and the polarization modulation hologram are illuminated by irradiating readout light to an area of the optical recording medium where the intensity modulation hologram and the polarization modulation hologram are multiplex recorded. It can be reproduced simultaneously as diffracted lights whose polarization directions are orthogonal to each other. For example, an intensity-modulated hologram is one in which P-polarized signal light is recorded by P-polarized reference light, and a polarization-modulated hologram is one in which P-polarized signal light is recorded by S-polarized reference light. In some cases, by irradiating the S-polarized readout light, S-polarized diffracted light is obtained from the intensity-modulated hologram, and P-polarized diffracted light is obtained from the polarization-modulated hologram.

Therefore, the hologram diffracted light is separated into an S-polarized light component and a P-polarized light component by a polarizing beam splitter or the like, and each of the polarized light components is detected by a separate photodetector. The data information and the data information recorded as the polarization modulation hologram can be read at the same time by separating them at a high SN ratio.

In addition, in this case, the reading light and the light are simultaneously read for two pages of the intensity modulation hologram and the polarization modulation hologram by the alignment pattern added to only one hologram, for example, the intensity modulation hologram. The recording medium can be positioned.

As described above, according to the present invention, the optical system and the optical recording medium can be positioned without adding a positioning pattern to all pages of the signal light. It is possible to increase the recording capacity and the data transfer speed, and to reduce the cost of the recording / reproducing apparatus.

For example, in M × N pixels of the first page,
When an alignment pattern is added to each of the four corners of m × n pixels, two pages worth of data information are added to the area of the same area of the optical recording medium by 4 × m × n pixels more than the conventional method. Can be recorded. Conversely, when the same amount of data information as the conventional method is recorded for two pages, the area of the recording area can be made smaller than that of the conventional method, and the space for forming the signal light can be reduced. The number of pixels of the optical modulator and the photodetector for detecting diffracted light can be reduced.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Example of Optical Recording Medium) FIG. 1 shows an example of an optical recording medium used in the method of the present invention, in which a polarization sensitive layer 12 is formed on one surface of a transparent substrate 11 such as a glass substrate. Things.

The polarization-sensitive layer 12 may be any material as long as it exhibits photoinduced birefringence and can record polarization information as a hologram. Having a polymer or polymer liquid crystal,
Alternatively, a polymer in which photoisomerizable molecules are dispersed can be used. Further, as the photoisomerizable group or molecule, for example, those containing an azobenzene skeleton are preferable.

As one preferable example of the polarization sensitive layer 12, a polyester having cyanoazobenzene in a side chain represented by a chemical formula shown in FIG. 2 can be used. As described in detail in Japanese Patent Application No. 10-32834, this material is capable of recording, reproducing, and erasing a hologram having polarization information by light-induced anisotropy due to photoisomerization of side chain cyanoazobenzene. It is possible.

In order to record a hologram volumetrically (three-dimensionally), the thickness of the polarization sensitive layer 12 needs to be at least about 10 μm. The larger the thickness, the larger the storage capacity. Note that the entire optical recording medium 10 may be formed as a polarization-sensitive layer exhibiting photoinduced birefringence.

(Example of optical recording device and optical reproducing device) FIG.
1 shows an example of an optical recording device and an optical reproducing device according to the present invention.

As the light source 21 of the recording / reproducing head 20,
A material that emits sensitive coherent light is used for the polarization sensitive layer of the optical recording medium 10. For example, as a polarization sensitive layer,
When a polyester having cyanoazobenzene in the side chain shown in FIG. 2 is used, a wavelength 515 sensitive to this is used.
nm argon laser is used.

The polarized light of the light 1 from the light source 21 is, for example, S-polarized light perpendicular to the paper surface. After passing the S-polarized light 1 through the spatial filter 22 to remove the wavefront disorder, the lens 23
To form parallel light, and further split by the beam splitter 24 into two light beams.

At the time of recording, the shutter 25 is opened, and the P-polarized light 2 transmitted through the beam splitter 24 is
The light enters the spatial light modulator 26 for forming signal light. By the control circuit omitted in the figure, the spatial light modulator 26 includes a positioning pattern as shown in FIG.
Alternatively, a binary two-dimensional data image that does not include the alignment pattern as shown in FIG. As a result, the light 4 transmitted through the spatial light modulator 26 is spatially intensity-modulated in accordance with the value of each pixel of the two-dimensional data image, and holds the two-dimensional data information according to the spatial intensity distribution.
It becomes a polarized signal light. As such a spatial light modulator 26, a liquid crystal panel or the like can be used.

The P-polarized signal light 4 from the spatial light modulator 26 is Fourier-transformed by the lens 27, and the converted P-polarized signal light 5 is applied to the optical recording medium 10.

At the same time, the S-polarized light 3 reflected by the beam splitter 24 is made incident on the polarization rotation element 28, and the polarization of the light transmitted through the polarization rotation element 28 is controlled in accordance with a control signal from a control circuit not shown in the figure. Rotate the corner. A liquid crystal valve, a Pockels element, a Faraday element, a half-wave plate, or the like can be used as the polarization rotation element 28 that can rotate the polarization angle of transmitted light.

At the time of recording, a P-polarized or S-polarized reference light is obtained as the light 6 transmitted through the polarization rotating element 28.
At the time of recording, the P-polarized or S-polarized reference light 6 is reflected by the mirror 29a, condensed by the lens 29b, and reflected by the mirror 29c to be irradiated with the signal light 5 of the optical recording medium 10. Irradiation.

Thus, the spatial intensity distribution of the P-polarized signal light 5 in the optical recording medium 10 is an intensity-modulated hologram when the reference light 6 is P-polarized, and a polarization-modulated hologram when the reference light 6 is S-polarized. Each is recorded as a hologram.

At the time of reproduction (reading), the shutter 25 is closed to block the signal light 5, and the reading light of S polarization is obtained as the light 6 transmitted through the polarization rotating element 28, and the read light is converted by the hologram of the optical recording medium 10. Irradiate the recorded area. The irradiated reading light 6 is diffracted by the hologram, and a diffracted light 7 is obtained on the optical path of the signal light 5.

In the case of hologram multiplex recording described later, in a state where the P-polarized signal light 5 is initially recorded as an intensity-modulated hologram by the P-polarized reference light 6,
When the S-polarized readout light 6 is irradiated, S-polarized diffracted light from the intensity modulation hologram is obtained as the diffracted light 7. Further, when the S-polarized readout light 6 is irradiated after the intensity modulation hologram and the polarization modulation hologram are multiplex-recorded in the same area of the optical recording medium 10, the S-polarized light from the intensity modulation hologram is converted as the diffracted light 7 And the component of P-polarized light from the polarization modulation hologram are obtained.

The diffracted light 7 is converted into a parallel light by a lens 51 and is incident on a polarization beam splitter 52. The S polarization component 8 reflected by the polarization beam splitter 52 and the P polarization component 9 transmitted through the polarization beam splitter 52. The S-polarized component 8 is imaged on the photodetector 53s to read its spatial intensity distribution, and the P-polarized component 9 is imaged on the photodetector 53p and its spatial intensity distribution Read. Therefore, the data information recorded as the intensity modulation type hologram and the data information recorded as the polarization modulation type hologram can be separated at a high SN ratio and read simultaneously.

(Example of hologram multiplex recording) When the intensity modulation hologram and the polarization modulation hologram are multiplex-recorded in the same area of the optical recording medium 10 by the above-described apparatus, FIG.
As shown in the multiplex recording processing routine 100, first, in step 101, as the P-polarized signal light 5 (4), a signal including an alignment pattern as shown in FIG. A P-polarized reference light is obtained as the light 6 transmitted through the rotating element 28, and both are irradiated onto the optical recording medium 10 at the same time to record an intensity-modulated hologram in the optical recording medium 10.

Next, in step 102, the signal light 5
Is blocked, and as light 6 transmitted through the polarization rotation element 28, S
A polarization readout light is obtained, and it is irradiated on the optical recording medium 10, and the intensity modulation hologram recorded in the optical recording medium 10 in step 101 is reproduced as S-polarized diffracted light 8, and the intensity is converted to light. The control circuit 70 controls the head moving mechanism 60 and the motor 40 based on the detection signal of the alignment pattern contained in the intensity-modulated hologram, which is detected by the detector 53s, and
And the optical recording medium 10 are aligned.

Then, after the recording / reproducing head 20 and the optical recording medium 10 are aligned as described above, step 1 is performed.
In FIG. 5, as P-polarized signal light 5 (4), FIG.
(A) does not include the alignment pattern as shown in FIG.
Is the reference light as it is in S-polarized light,
Are simultaneously radiated to the area where the intensity-modulated hologram is recorded, and multiplexed with the intensity-modulated hologram in the area to record the polarization-modulated hologram.

In step 103, the signal light 5 passes through the optical recording medium 10 and enters the polarization beam splitter 52 via the lens 51. Since the signal light 5 is P-polarized,
It does not affect the position control by the control circuit 70 based on the detection of the S-polarized component 8 by the photodetector 53s.

(Example of hologram multiplex reproduction) When the intensity modulation hologram and the polarization modulation hologram multiplexed and recorded by the above method are reproduced at the same time, the signal light 5 is cut off and the light transmitted through the polarization rotating element 28 is transmitted. In step 6, S-polarized readout light is obtained, and the readout light is applied to an area of the optical recording medium 10 where the intensity modulation hologram and the polarization modulation hologram are multiplex-recorded.

As a result, S-polarized diffracted light 8 is obtained as the diffracted light from the intensity modulation hologram including the alignment pattern, and P diffracted from the polarization modulation hologram not including the alignment pattern. A polarized diffracted light 9 is obtained. Therefore, based on the detection signal of the alignment pattern by the photodetector 53s, the control circuit 7
0 controls the head moving mechanism 60 and the motor 40, and the recording / reproducing head 20 and the optical recording medium 10 are aligned.

In this state, the photodetector 53s records the S-polarized diffracted light 8 from the intensity modulation hologram as an intensity modulation hologram from a portion other than the alignment pattern. The read data information was read, and in the photodetector 53p, the data information recorded as the polarization modulation hologram was read from the P-polarized diffraction light 9 from the polarization modulation hologram, and recorded as the intensity modulation hologram. The data information and the data information recorded as the polarization modulation hologram are combined with a high SN.
They can be separated and separated and reproduced at the same time.

(Verification by Experiment) With the above-described method and apparatus, recording and reproduction of two-dimensional data information were actually attempted. As the optical recording medium 10, a polarization-sensitive layer formed of polyester having cyanoazobenzene in a side chain was used, and as the light source 21, the above-described argon ion laser having a wavelength of 515 nm was used. The signal light and reference light at the time of recording are about 0.5 W / cm ² , and the reading light at the time of reproduction is
0.15 W / cm ² . As the spatial light modulator 26, the size of one pixel is 42 μm × 42 μm and 640 × 4
A liquid crystal panel for a projector having 80 pixels was used.

As a result, an intensity-modulated hologram and a polarization-modulated hologram can be recorded in the same area of the optical recording medium, and the S-polarized component 8 and the P-polarized component 9 are respectively recorded.
Was successfully reproduced as a two-dimensional binary image without crosstalk. Also, only by the alignment pattern added to the intensity-modulated hologram,
High-precision alignment in pixel units was realized.

(Recording-only or reproduction-only device) The example of FIG. 3 shows a case where recording and reproduction can be performed by one device, but recording only (however, hologram reproduction for positioning is included). Alternatively, it may be a reproduction-only device. In an apparatus dedicated to recording, the polarization beam splitter 5
2, and the above example does not require the photodetector 53p,
By excluding these, it is possible to reduce the size and weight of the recording head and reduce the cost of the recording apparatus. In an apparatus dedicated to reproduction, the shutter 25, the spatial light modulator 26 and the lens 27, and furthermore, the beam splitter 24 and the polarization rotation element 28 are unnecessary depending on the configuration. Cost reduction of the device can be realized.

[0054]

As described above, according to the present invention, the optical system and the optical recording medium can be aligned without adding an alignment pattern to all pages of the signal light. Accordingly, it is possible to increase the recording capacity and the data transfer speed, and to reduce the cost of the recording / reproducing apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an optical recording medium used in the method of the present invention.

FIG. 2 is a diagram showing a chemical formula of an example of a material of a polarization sensitive layer of an optical recording medium.

FIG. 3 is a diagram showing an example of an optical recording device and an optical reproducing device according to the present invention.

FIG. 4 is a diagram illustrating an example of a multiplex recording processing routine.

FIG. 5 is a diagram illustrating examples of signal light that does not include a positioning pattern and signal light that does.

FIG. 6 is a diagram for explaining a shift multiplex recording method.

[Explanation of symbols]

 4, 5 ... signal light 6 ... reference light, readout light 7 ... diffracted light 10 ... optical recording medium 12 ... polarization sensitive layer 20 ... recording / reproducing head 21 ... light source 24 ... beam splitter 25 ... shutter 26 ... spatial light modulator 28 ... Polarization rotating element 40 ... Motor 52 ... Polarizing beam splitter 53s, 53p ... Photodetector 60 ... Head moving mechanism 70 ... Control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2K008 AA04 AA17 BB04 BB06 CC01 DD11 DD12 FF07 FF17 FF21 FF24 HH12 HH13 HH14 HH26 5D090 AA01 CC01 CC04 CC14 DD03 FF02 GG22 HH01 LL02 5D118 AA13 BA01 BB02 CD02 CF02 CD02

Claims (7)

[Claims] 1. A first signal light, which holds two-dimensional data information according to a spatial intensity distribution and includes a positioning pattern, is recorded as a first hologram on an optical recording medium. Reproducing the diffracted light from the first hologram, detecting the positioning pattern, and controlling the relative position of the signal light and the optical recording medium by the detection signal, the two-dimensional data is obtained by the spatial intensity distribution. The second signal light that retains the information and does not include the alignment pattern is changed as the second hologram by changing the polarization angle of the reference light or the signal light from the time of recording the first hologram.
An optical recording method for recording in an area of the optical recording medium where the first hologram is recorded. 2. A light source that emits coherent light, and a spatial light modulator that intensity-modulates light from the light source according to two-dimensional data information to obtain signal light that holds two-dimensional data information by a spatial intensity distribution. An imaging optical system that irradiates the signal light onto an optical recording medium; a reference light optical system that obtains reference light from light from the light source and irradiates the optical recording medium; and a polarization of the reference light or the signal light. A polarization rotation element for rotating an angle, a photodetector for detecting the intensity of a polarization component having a predetermined polarization angle in the diffracted light from the hologram recorded on the optical recording medium, and a detection signal of the photodetector. A recording head including the light source, the spatial light modulator, the imaging optical system, the reference light optical system, a polarization rotating element, and a photodetector, and control means for controlling a relative position of the optical recording medium. . 3. The optical recording apparatus according to claim 2, wherein said optical recording medium is disk-shaped, said optical recording apparatus includes a medium driving mechanism for rotating said optical recording medium, and said recording head being connected to said optical recording medium. An optical recording device comprising: a head moving mechanism for moving the head in a radial direction. 4. A signal light for two pages, each of which holds two-dimensional data information according to a spatial intensity distribution and has a positioning pattern added to only one of the pages, serves as a reference light or a polarization of the signal light for each page. The angle is changed, and the readout light is applied to the optical recording medium recorded in the same area as the hologram, and the diffracted light is simultaneously reproduced from the hologram for the two pages, and the alignment pattern is obtained from the diffracted light. And a method of reading the two-dimensional data information of each page by separating the two-dimensional data information from the diffracted light in a state where the relative position between the read light and the optical recording medium is controlled by the detection signal. 5. A signal light for two pages, each of which holds two-dimensional data information by a spatial intensity distribution and has a positioning pattern added to only one page, is a reference light or a polarization of the signal light for each page. A readout optical system for changing the angle and irradiating readout light to an optical recording medium recorded in the same area as a hologram and reading out the holograms for the two pages simultaneously, A diffracted light optical system that separates the diffracted light into two polarization components orthogonal to each other, two photodetectors that detect the intensities of the two polarization components, and the above-described readout based on a detection signal of one of the photodetectors. An optical reproducing apparatus comprising: a reproducing head including an optical optical system, a diffractive optical system, and two photodetectors; and control means for controlling a relative position of the optical recording medium. 6. The optical reproducing apparatus according to claim 5, wherein said optical recording medium has a disk shape, and said optical reproducing apparatus comprises: a medium driving mechanism for rotating said optical recording medium; And a head moving mechanism for moving the head in a radial direction. 7. A signal light of two pages, each of which holds two-dimensional data information by a spatial intensity distribution and has a positioning pattern added to only one page, is a reference light or a polarization of the signal light for each page. An optical recording medium in which the angles are changed and each is recorded in the same area as a hologram.