JP2006268933A - Holography apparatus and method of reproducing holography medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holography apparatus and a method of reproducing a holography medium by which the holography medium can be reproduced with conditions of a desired angle and a frequency for an angle deviation and a wavelength deviation due to variation of ambient temperature. <P>SOLUTION: The holography apparatus performs multiple recording for each prescribed storage region by varying an angle of reference light irradiated on a holography medium, the apparatus has a reference light irradiating means irradiating the holography medium with the reference light varying an angle, a data detecting means in which reproduced light emitted from each information data page by the reference light is made incident on a detection plane and information data is reproduced from the reproduced light, a produced light deviation detecting means detecting light intensity of the reproduced light in each of a plurality of prescribed regions of a detection plane by the reproduced light emitted from the holography medium by the reference light and detecting deviation of an angle and wavelength of the reference light made incident on the holography medium, and a reference light control means controlling the incident angle and the wavelength of the reference light by a detected result of deviation of the angle and the wavelength of the reproduced light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a holographic device used for recording information data on a holographic medium and a method for reproducing the holographic medium.

2. Description of the Related Art A holographic recording system is used in which signal light composed of information data and reference light are irradiated on a holographic medium, an interference pattern is generated in the holographic medium, and the information data is recorded.
As a method for multiplex recording and reproduction of digital data consisting of “1” or “0” on this holographic medium, there is a method described in Patent Document 1 shown below and an apparatus corresponding to this method.
In this document, as a method for multiplex recording of information data at each of a plurality of locations of a holographic medium, a recording angle reproduction method in which recording and reproduction are performed by changing the angle of the reference light, and a recording by changing the wavelength of the reference light are performed. -The method of performing playback is described.

In the multiple recording method shown in Patent Document 1, in the case of writing angle multiplexing, information data recorded on a holographic medium is read with reference light for reading at an angle similar to the reference light at the time of recording. If irradiation can be performed, the information data (information data of the data page) written at a desired angle from among the multiplexed data can be arbitrarily read out.
JP 2004-177958 A

However, in the recording / reproducing method described above, when the holographic medium is irradiated with the reference light at the time of reading, the angle is the same as the angle of the reference light at the time of recording due to the mechanical accuracy in the optical system of the reproducing apparatus. There is a problem that information data cannot be read with high accuracy.
In particular, when considering recording with a holographic recording device and reading with a holographic reproducing device, the dimensional accuracy of the holographic medium varies, or the holographic medium is loaded into the reproducing device every time it is read. Since the angular deviation of the holographic medium with respect to a predetermined incident angle may not be constant and may vary, it becomes more difficult to set the reference light at the time of reading as the angle of the reference light at the time of recording.
For example, in the case of angle multiplexing, if reference light having the same angle as the angle recorded on the holographic medium can be incident, the data of the desired page can be reproduced by the holographic reproducing device.

Further, the deviation of the angle of the reference beam may occur not only in the scanning direction for multiplexing information data pages, that is, in the Bragg diffraction direction but also in a direction perpendicular to the Bragg diffraction direction (non-Bragg direction). is there. If there is an angle shift in the non-Bragg direction both when recording and reproducing information data, the reproduction of information data recorded on the holographic medium is affected.
On the other hand, in the case of wavelength multiplexing, when recording / reproducing information data on a holographic medium, for example, by adjusting the temperature of a wavelength tunable laser such as a VCSEL (surface emitting semiconductor laser), the chip temperature can be changed. Then, by thermally expanding and contracting the chip, the wavelength of the emitted light is controlled according to the change of the resonance wavelength, and information data is multiplexed and recorded.

The temperature of the VCSEL can be controlled with an error within a certain range by adjusting the operating current.
However, the control temperature depends on the ambient temperature and the mounting form, and the operating current and the temperature of the VCSEL do not always coincide with each other. When reproducing, the wavelength of the reference light used for reproduction is recorded on the holographic medium. There is a problem that it is difficult to match the wavelength of the reference light.

In addition, when a holographic medium expands and contracts due to changes in ambient temperature during reproduction by a conventional holographic apparatus, the expansion and contraction is not necessarily isotropic, and both wavelength and angle are corrected. If not, there is a problem that an area where the information data stored in the information data page cannot be reproduced is generated.
In other words, in some areas of the information data page, the Bragg angle at which the intensity of the reproduction light is maximized may be shifted, and the entire information data page may not be reproduced at a time.

  The present invention has been made in view of such circumstances, and a holography device that can be reproduced according to conditions of a desired angle and wavelength, even with respect to a wavelength shift due to an angle shift or a change in ambient temperature, And a method for reproducing a holographic medium.

The holography apparatus of the present invention changes the angle of the reference light during recording, and sequentially changes the angle of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of the plurality of information data pages, and multiplexes at different angles. A holography device that reads data of a recorded information data page and reproduces the recorded information data. Reference light irradiation means for irradiating the holographic medium with reference light at a different angle; and by the reference light The detection surface is incident on the detection surface by the reproduction light emitted from each information data page and reproduces the information data from the reproduction light, and the reproduction light emitted from the holographic medium by the reference light. The light intensity of the reproduction light in each of a plurality of predetermined regions is detected and incident on the holographic medium of the reference light The incident angle and wavelength of the reference light are controlled by the reproduction light deviation detecting means for detecting the deviation of the angle (angles θx and θy) and the wavelength (deviation of the wavelength λ), and the detection result of the angle and wavelength deviation of the reproduction light. Reference light control means.
The reproducing method of the holographic medium of the present invention is different by changing the angle of the reference light at the time of recording and sequentially changing the angle of the reference light to be irradiated to the holographic medium in which the information data is recorded for each of a plurality of information data pages. A method for reproducing a holographic medium that reads out data of an information data page that is multiplexed and recorded at an angle and reproduces the recorded information data, the process of irradiating the holographic medium with reference light at different angles, and the data A process in which the detection means makes the reproduction light emitted from each information data page incident on the detection surface by the reference light and reproduces the information data from the reproduction light, and the reproduction light deviation detection means has the holography by the reference light. The reproduction light emitted from the medium detects the light intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface, A process of detecting a shift in angle and wavelength of the reference light incident on the holographic medium, and a process in which the reference light control means controls the incident angle and wavelength of the reference light based on the detection result of the angle and wavelength shift of the reproduction light. And have.
As a result, the holographic device / holographic medium reproducing method of the present invention detects and reads out the angle and wavelength deviation of the reference light based on the light intensity even if the wavelength deviation occurs due to the angular deviation or the ambient temperature change. Since the appropriate angle and wavelength of the reference light are adjusted for the target holographic medium, the entire two-dimensional information data can be reproduced uniformly and with high accuracy.

In the holographic device according to the present invention, the data detection means divides the information data page into a lattice shape on a two-dimensional plane formed by the X-axis direction which is the Bragg diffraction direction and the Y-axis direction perpendicular to the X-axis direction. A plurality of blocks are generated, the intensity of the reference light is detected for each block, and the detected intensity is output.
In the holography device of the present invention, the reference light control unit calculates a variation evaluation amount between all blocks from the dispersion or standard deviation of the light intensity between the blocks, and refers to minimize the variation evaluation amount. Control the wavelength and angle of light.
As a result, the holography device according to the present invention performs a simple calculation based on the detected reference light intensity data indicating the angle and wavelength deviation, and the reproduced light emitted in the entire information data detected in the information data page. Therefore, since the angle and wavelength of the reference light are controlled so as to balance the two, the entire two-dimensional information data can be reproduced uniformly and with high accuracy.

In the holographic device of the present invention, the reproduction light shift detection means calculates an average intensity that is an average of the intensity of the reproduction light incident on each block, and normalizes the variation evaluation amount by dividing by the average intensity, The reference light control means controls the wavelength and angle of the reference light so as to minimize the standardized variation evaluation amount.
As a result, the holography apparatus of the present invention standardizes the variation evaluation amount with a numerical value obtained by averaging the intensity of the reference light over the entire information data page. The wavelength and angle of the reference light can be optimally adjusted in any information data page without depending on the intensity of the reproduction light that differs for each data purge.

In the holography device according to the present invention, the reproduction light shift detection means calculates an average intensity that is an average of the intensity of the reproduction light incident on each block, and divides the variation evaluation amount by a value obtained by squaring the average intensity. Then, a variation evaluation amount linked with the intensity of the reference light is obtained, and the reference light control means controls the wavelength and angle of the reference light so as to minimize the standardized variation evaluation amount.
As a result, the holography device of the present invention controls the amount of variation linked to the intensity to a minimum, so that the angle and wavelength are adjusted in a direction where the variation is small and the overall strength is large, thereby correcting the variation. Not only that, the intensity of the entire information data is controlled to be maximized.

In the holography device of the present invention, the data detection means scans the reference light while changing the angle of the reference light in the X-axis direction, which is the Bragg diffraction direction, and detects information data at a position where the variation evaluation amount is minimum. .
As a result, the holography device of the present invention is an effective signal at an angle in the X-axis direction that maximizes the Bragg diffraction intensity in a state where the wavelength and the angle in the Y-axis direction (direction perpendicular to the Bragg diffraction direction) are adjusted. Playback is possible.

In the holography device of the present invention, the reproduction light shift detection unit detects the wavelength of the reference light and the angle shift in the Y-axis direction at predetermined intervals, and the reference light control unit detects the wavelength of the reference light and the reference light in the cycle. Adjust the lateral angle in the Y-axis direction.
As a result, the holography apparatus of the present invention adjusts the variation evaluation amount so as to be the smallest in the respective adjustments in the control of the wavelength and angle even when the wavelength and angle are unknown. The initial wavelength and the Y-axis direction angle can be appropriately set for each holographic medium.

In the holography device of the present invention, the reference light control means causes the wavelength of the reference light to be deviated from the predetermined wavelength by a negative minute amount and a positive minute amount by the second wavelength. The predetermined wavelength is adjusted by the variation evaluation amount.
In the holography device of the present invention, the reference light control means includes a first lateral angle obtained by causing the lateral angle of the reference light in the Y-axis direction to deviate by a minute amount from a predetermined lateral angle, and a positive The predetermined lateral angle is adjusted according to the variation evaluation amount by alternately changing the second lateral angle that is deviated by a minute amount.
Thus, when reproducing information data from a holographic medium, the holographic device of the present invention constantly monitors the intensity of the reproduction light during the reproduction operation, and controls to obtain the optimum wavelength and angle of the reference light based on the monitoring result. Therefore, stable reproduction light can be obtained, and the entire two-dimensional information data can be reproduced uniformly and with high accuracy.

The holography apparatus of the present invention changes the wavelength of the reference light during recording, and sequentially changes the wavelength of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of a plurality of information data pages, and multiplexes at different wavelengths. A holography device that reads data of a recorded information data page and reproduces the recorded information data. Reference light irradiation means for irradiating the holographic medium with a reference light by changing a wavelength; and by the reference light The detection surface is incident on the detection surface by the reproduction light emitted from each information data page and reproduces the information data from the reproduction light, and the reproduction light emitted from the holographic medium by the reference light. The light intensity of the reproduction light in each of a plurality of predetermined regions is detected and incident on the holographic medium of the reference light And reproduction light displacement detection means for detecting a deviation of the angle and wavelength, the detection result of the angle and the wavelength shift of the reproduction light, and a reference light control means for controlling the angle of incidence and wavelength of the reference light.
The reproducing method of the holographic medium of the present invention is different by changing the wavelength of the reference light at the time of recording and sequentially changing the wavelength of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of a plurality of information data pages. A reproduction method of a holographic medium that reads out data of an information data page that is multiplexed and recorded at a wavelength and reproduces the recorded information data. Reference light irradiating means irradiates the holographic medium with reference light by changing the wavelength. A process in which the data detection means makes the reproduction light emitted from each information data page incident on the detection surface by the reference light and reproduces the information data from the reproduction light, and the reproduction light deviation detection means has the reference light Due to the reproduction light emitted from the holographic medium by light, the intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface And detecting the angle and wavelength deviation of the reference light incident on the holographic medium, and the reference light control means detects the incident angle of the reference light and the reference light based on the detection result of the angle and wavelength deviation of the reproduction light. And controlling the wavelength.
As a result, the holographic device / holographic medium reproducing method of the present invention detects and reads out the angle and wavelength deviation of the reference light based on the light intensity even if the wavelength deviation occurs due to the angular deviation or the ambient temperature change. Since the appropriate angle and wavelength of the reference light are adjusted for the target holographic medium, the entire two-dimensional information data can be reproduced uniformly and with high accuracy.

  As described above, according to the holographic device / holographic medium reproducing method of the present invention, in the reproducing light emitted from the holographic medium by the reference light, the reproducing light in each of a plurality of predetermined regions on the detection surface where the reproducing process is performed. By detecting the light intensity of each region, monitoring the light intensity of the reproduction light in each region, and balancing each region over the entire detection surface, the angle and wavelength of the reference light incident on the holographic medium during reproduction are adjusted. In order to detect the deviation, even if an angular deviation or a wavelength deviation due to a change in ambient temperature occurs, the angle and wavelength deviation of the reference light are detected based on the light intensity, and the appropriate holographic medium to be read out is detected. The entire two-dimensional information data stored in each information data page of the holographic medium to adjust the angle and wavelength of the reference beam Uniform, can be reproduced at high precision.

Hereinafter, a holographic recording apparatus and a reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the embodiment of the present invention, when multiplex recording of information data is performed, a plurality of pages (hereinafter referred to as information) for recording information data by changing the angle or wavelength of the reference light for each recording area of the holographic medium (hereinafter referred to as media). Data page), and multiple recording of information data is performed.
That is, the holographic device of the present invention changes the angle (or wavelength) of the reference light during recording, and the angle (or wavelength) of the reference light that irradiates the holographic medium on which information data is recorded for each of a plurality of information data pages. ) Are sequentially changed to read out the data of the information data page that is multiplexed and recorded at different angles (or wavelengths) and reproduce the recorded information data.

  In the holography apparatus of the present invention, the reference light irradiating means (the mirror 8 and the laser light source (not shown) of the embodiment) irradiates the medium with the reference light while changing the angle (or wavelength), and the data detecting means (embodiment) The detector 6) is irradiated with the reproduction light emitted from each multiplexed information data page by the reference light irradiated to the detection surface to reproduce the information data from the reproduction light, and the reproduction light deviation detection means (implemented) The form variation evaluation amount F calculating unit 9) detects the light intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface by the reproduction light emitted from the medium by the reference light, and is incident on the holographic medium of the reference light The reference light control means (the X-axis direction angle adjustment unit 11 and the Y-axis direction angle adjustment unit 12 in the embodiment) detects the angle and wavelength shift of the reproduction light. Results The controls the incident angle and wavelength of the reference light.

<First Embodiment>
Next, a holography device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration example of a holography device according to the first embodiment. That is, FIG. 1 is an optical layout diagram showing an example of a configuration for recording and reproducing on a medium.
In the first embodiment of FIG. 1, a transmission hologram in which signal light and reference light are incident on the medium 4 from the same side is described as an example.
The holography device shown in FIG. 1 includes a shutter 1, an SLM • 2, an FT lens 3 and 5, a detector 6, a shutter 7, a mirror 8, a variation evaluation amount F calculation unit 9, a wavelength adjustment unit 10, and an X-axis direction angle adjustment unit. 11, Y-axis direction angle adjustment unit 12 and a laser light source (not shown).

A. Recording process of information data on the medium 4 The laser light source emits a laser beam having a predetermined wavelength, and this laser beam is divided into a distribution light M and a distribution light N by a predetermined mechanism (such as a beam splitter (not shown)), The light enters the shutter 1 and the shutter 7, respectively.
The shutter 1 is opened when information data is written to the medium 4, and is closed when not written.

The SLM 2 is composed of a liquid crystal panel or the like, and displays a checkered dot pattern corresponding to information data to be written on the medium 4, that is, two-dimensional information data to be written, on a modulation surface perpendicular to the incident angle of the distribution light M. To form.
This SLM · 2 modulates the amplitude of the incident distributed light M with the dot pattern on the modulation surface, and emits it to the FT (Fourier transform) lens 3 as signal light including information to be written on the medium 4.

In FIG. 4, a transmissive SLM is used, but a reflective SLM can also be used in combination with a beam splitter or the like.
Here, on the modulation surface, for example, it is preferable that the modulation is performed in black so that the portion where the data is “1” does not transmit the reference light, and the portion where the data is “0” transmits the reference light.

The FT lens 3 collects the signal light from the SLM 2 and irradiates the medium 4 to be hologram-recorded (multiplexed recording). Here, the medium 4 is installed in the vicinity of the condensing point of the FT lens 3.
The shutter 7 controls the emission of the distributed light N distributed by the beam splitter to the mirror 8 by performing an opening / closing process synchronized with the opening / closing timing of the shutter 1.

  The mirror 8 is composed of a galvanometer mirror or the like that can change the reflection angle of incident light, and the reflection angle of the incident distributed light N is sequentially changed for each information data page under the control of a write control unit (not shown). Then, it is emitted to the medium 4 as reference light.

Here, the reference light is controlled to be incident so that the signal light is overlapped in the vicinity where the signal light is incident on the medium 4, and information on interference fringes formed by the interference between the signal light and the reference light is information data (each Sub-data) in the block).
At this time, the mirror 8 changes the angle of the reference light at a predetermined angle pitch, so that the information data of different signal light is recorded in multiple in a predetermined storage area of the medium 4 by a plurality of information data pages. In other words, new data can be sequentially overwritten by two-dimensional information data of different dot patterns (checkered pattern) formed on the modulation surface of the SLM · 2.
Here, the angle of the reference light in which the two-dimensional information data is recorded is referred to as an information data page. In the writing process described above, the angle of the reference light described above is changed, and information data is written in the information data page corresponding to each angle.

In the multiplex recording method described above, the medium 4 is a hologram medium having a relatively thick recording layer (a layer in the thickness direction where interference fringes are formed) (for example, 1 mm or more), and the angle of the reference light is multiplexed. When recording, the angular resolution at the angular pitch of the information data page is the wavelength λ of the laser light, the incident angle θx of the signal light and reference light in the Bragg diffraction direction with respect to the surface of the medium 4 (an angle corresponding to the information data page), and It is determined by the thickness D of the medium 4.
That is, the angular resolution at the angular pitch is proportional to the laser wavelength λ and inversely proportional to the thickness D of the medium 4.
Here, the incident angle θx (a direction parallel to the Bragg diffraction direction) is an angle formed with the incident direction of the reference light with respect to the vertical axis P of the incident surface of the reference light of the medium 4.

B. Next, when reproducing information data recorded on the medium 4, the signal light side shutter 1 is closed, the reference light side shutter 7 is opened, and only the distribution light N is obtained. By making the light incident on the medium 4, the information data recorded on the medium 4 is reproduced.
Here, the mirror 8 uses the distribution light N incident from the shutter 7 as a reference light at the time of reading, at an angle adjusted by the X-axis direction angle adjustment unit 11 and the Y-axis direction angle adjustment unit 12. 4 is output (reflected).

The FT lens 5 returns the reproduction light incident from the medium 4 to the signal light incident on the FT lens 3, that is, the parallel light (coherent light) by the irradiation of the reference light, and the detector (detector) 6 Project to.
Here, the focal lengths of the FT lens 3 and the FT lens 5 are the same, and the SLM · 2, the FT lens 3, the media 4, the FT lens 5, and the detector 6 are arranged apart from each other by the focal length.
In other words, the SLM 2 and the detector 6 are respectively placed at the front focal point of the FT lens 3 and the rear focal point position of the FT lens 5.

For this reason, the reference light is diffracted by the information data stored in the information data page in the recording area of the medium 4, that is, interference fringes, and reproduction light is generated.
This reproduction light is converted into parallel components by the FT lens 5 and imaged on the detector 6 as a pattern similar to the two-dimensional dot pattern on the modulation surface of the SLM · 2, and information data is reproduced.
The detector 6 is composed of a two-dimensional CCD, a C-MOS image sensor or the like, reads the pattern, and outputs it as information data to an external circuit.

  The variation evaluation amount F calculation unit 9 inputs the information data detected by the detection surface of the detector 6, divides the detection surface of the detector 6 into a lattice shape, as shown in FIG. 2, and a plurality of blocks Bxy (for example, The blocks B11, B12, B13, B21, B22, B23, B31, B32, B33) are formed as 9 blocks of 3 × 3, and the information data included in each block is included as sub-data in this block The signal intensity or signal amplitude value of the sub-data (detection element, that is, a set of detection values in dot units) to be added is added to obtain a sub-data total value for each block.

  Further, the variation evaluation amount F calculation unit 9 obtains an average value Bave of the obtained sub-data total values of each block, and from the average value Bave and the sub-data total value of each block, the following equation (1) is used. The variance σ2 is obtained, and the standard deviation σ is obtained from the following equation (2) using the variance σ2. In the following equations, n = i * j is the number of lattice divisions, i is the number of divisions in the X-axis direction, and j is the number of divisions in the Y-axis direction.

Here, in the variation evaluation amount F calculation unit 9, the standard deviation σ obtained by the equation (2) is an index indicating variation in the sub-data total value between the respective blocks in the lattice shape, that is, variation or balance in signal intensity. Therefore, it can be used as the variation evaluation amount Fa of the signal intensity between the blocks divided in a lattice shape.
Further, the variation evaluation amount F calculation unit 9 adjusts each parameter of the wavelength λ, the X-axis direction angle θx, and the Y-axis direction angle θy of the laser light source by using the calculated variation evaluation amount Fa, thereby evaluating the variation. The amount Fa is adjusted to be smaller. Here, in the variation evaluation amount F calculation unit 9, the variance σ2 may be used as the variation evaluation amount Fa.

The X-axis direction angle adjustment unit 11 adjusts the X-axis direction angle θx (Bragg diffraction direction) by controlling the angle of the reflection surface of the mirror 8 under the control of the variation evaluation amount F calculation unit 9, and each information data The angle corresponds to the page.
At this time, as shown in FIG. 3, the variation evaluation amount F calculation unit 9 reproduces the information data page so that the reference light is at the maximum position of the signal intensity of the reproduction light emitted after being diffracted in the medium. θ (that is, the X-axis direction angle θx) is controlled by the X-axis direction angle adjustment unit 11.
That is, the X-axis direction angles θx1, θx2, θx3, which are signal intensities S1, S2, S3,... Of the reproduced light (this signal intensity is a value obtained by adding all the detected signal intensities on the detection surface of the detector 6). ... corresponds to the angle of the information data page.

The wavelength adjusting unit 10 controls the wavelength λ by controlling the laser light source. Here, the variation evaluation amount F calculation unit 9 determines the amount of the reference light so that the variation evaluation amount due to the signal intensity of the reproduction light emitted after being diffracted by the medium 4 is smaller (preferably becomes a minimum value). The wavelength adjustment unit 10 controls the wavelength λ.
When reading, the wavelength λ of the reference light is deviated, or the medium 4 is distorted due to the influence of the surrounding temperature change or the like, and deviates from the appropriate wavelength of the reference light. As shown in (a), the Bragg diffraction angle of a part of the diffracted light in the X-axis direction (a band-like region parallel to the Y-axis direction) is shifted, and the incident angle of the reproduction light having the maximum intensity near the center. In, the corresponding area becomes dark, that is, the signal intensity becomes weak.

The Y-axis direction angle adjustment unit 12 adjusts the Y-axis direction angle θy, which is an angle perpendicular to the Bragg diffraction direction (the angle scan direction in which the information data page is multiplexed), and tilts the reflection surface of the mirror 8. This is done by controlling the corners. Here, the variation evaluation amount F calculation unit 9 sets the Y-axis direction angle θy in the Y-axis direction so that the variation evaluation amount Fa due to the signal intensity of the reproduction light emitted after the reference light is diffracted by the medium 4 is smaller. Control is performed by the angle adjustment unit 12.
When there is an angle deviation in the Y-axis direction during reading, if it is not adjusted to an appropriate Y-axis direction angle θy, a part of the diffracted reproduction light, that is, as shown in FIG. The Bragg diffraction angle of a partial region in the Y-axis direction (a belt-like region parallel to the X-axis direction) is shifted, and the corresponding region becomes dark, that is, the signal intensity becomes weak.
Generally, the above-mentioned wavelength component deviation and the Y axis direction angle deviation are mixed, and unless the wavelength λ and the Y axis direction angle θy are adjusted to appropriate values, the entire information data page is reproduced uniformly as a result. It will not be done.

As described above, as the component of the angle deviation of the angle at which the reference light enters the medium 4, assuming that the Bragg diffraction direction is the X axis and the Y axis is perpendicular to the X axis direction, the angle deviation in the X axis direction and Y It can be decomposed into an angular deviation in the axial direction.
As described above, the angular deviation in the X-axis direction is such that the signal intensity of the reproduction light that is swept in the X-axis direction and is incident on the detection surface of the detector 6 as shown in FIG. Thus, the correction can be performed by setting the reflection surface of the mirror as an appropriate angle.
Further, the angle deviation in the X-axis direction may be controlled as another adjustment means so that the variation evaluation amount Fc linked with the intensity described later becomes smaller as in the adjustment of the wavelength λ and the Y-axis direction angle θy. good.

Next, the control of the wavelength λ at the time of reading information data in the holography device according to the first embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing an operation example of controlling the wavelength λ at the time of reading in the holography device according to the first embodiment.
As a premise, the angle adjustment in the Bragg diffraction direction is performed, and the X-axis direction angle θx is adjusted to the angle at which the signal intensity S is maximized at the present time.
The wavelength adjusting unit 10 adjusts the wavelength of the laser light emitted from the laser light source to the center wavelength λc set in advance by the control of the variation evaluation amount F calculating unit 9.
Then, the variation evaluation amount F calculation unit 9 calculates the variation evaluation amount F0 at the center wavelength λc (step S1).

Next, the variation evaluation amount F calculation unit 9 outputs a control signal to the wavelength control unit 10 so as to change the wavelength of the laser light to λc−Δλ. Here, the deviation amount Δλ is appropriately set depending on the wavelength adjustment stage, that is, coarse adjustment (large value) or fine adjustment (small value). For example, the deviation amount Δλ may be varied in the range of 0.01 nm to 1.0 nm. It may be.
Thereby, the wavelength controller 10 controls the laser light source and changes the wavelength of the emitted laser light source to λc−Δλ (step S2).
Next, the variation evaluation amount F calculation unit 9 controls the X-axis direction angle θx to calculate the variation evaluation amount F1 at the wavelength λc−Δλ at the X-axis direction angle θx at which reproduction light with the maximum signal intensity is obtained. (Step S3).

Next, the variation evaluation amount F calculation unit 9 outputs a control signal to the wavelength control unit 10 so as to change the wavelength of the laser light to λc + Δλ.
As a result, the wavelength control unit 10 controls the laser light source and changes the wavelength of the emitted laser light source to λc + Δλ (step S4).
Next, the variation evaluation amount F calculation unit 9 controls the X-axis direction angle θx to calculate the variation evaluation amount F2 at the wavelength λc + Δλ at the X-axis direction angle θx at which the reproduction light with the maximum signal intensity is obtained ( Step S5).

Then, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F1 is smaller than the variation evaluation amount F2, and at this time, if detecting that the variation evaluation amount F1 is smaller than the variation evaluation amount F2, On the other hand, if it is detected that the variation evaluation amount F1 is larger than the variation evaluation amount F2, the process proceeds to step S10 (step S6).
If YES in step S6 (when it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F2), the process proceeds to step S7. In this step S7, the variation evaluation amount F calculation unit 9 performs the variation evaluation. It is detected whether or not the amount F1 is smaller than the variation evaluation amount F0. At this time, if it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F0, the process proceeds to step S8. When it is detected that the variation evaluation amount F0 is greater, the process is terminated.

In the case of YES in step S7 (when it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F0), the process proceeds to step S8, and in this step S8, the variation evaluation amount F calculation unit 9 includes the wavelength control unit. 10, a control signal is output so that the wavelength of the laser beam is changed to λc−Δλ.
As a result, the wavelength control unit 10 controls the laser light source and changes the wavelength of the emitted laser light source to λc−Δλ.
Then, the variation evaluation amount F calculation unit 9 sets the variation evaluation amount F1 based on a reference value (allowable value of the adjustment residual amount of the variation evaluation amount necessary for signal detection, such as the S / N ratio distribution of the reproduction signal). In this case, if it is detected that the variation evaluation amount F1 is smaller than the reference value, the process is terminated because it is the control limit value, while the variation evaluation amount F1 is the reference value. If it is detected that the value is greater than the value, the process returns to step S1 (step S9).

On the other hand, in step S6, the variation evaluation amount F calculation unit 9 detects that the variation evaluation amount F1 is larger than the variation evaluation amount F2 (in the case of NO), and advances the process to step S10.
In step S10, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F2 is smaller than the variation evaluation amount F0, and at this time, detects that the variation evaluation amount F2 is smaller than the variation evaluation amount F0. Then, the process proceeds to step S11. On the other hand, when it is detected that the variation evaluation amount F2 is larger than the variation evaluation amount F0, the processing is terminated.

If YES in step S10 (when it is detected that the variation evaluation amount F2 is smaller than the variation evaluation amount F0), the process proceeds to step S11. In this step S11, the variation evaluation amount F calculation unit 9 includes the wavelength control unit. 10, a control signal is output so that the wavelength of the laser beam is changed to λc + Δλ.
Thereby, the wavelength control unit 10 controls the laser light source, changes the wavelength of the emitted laser light source to λc + Δλ, and advances the process to step S12.
In step S12, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F2 is smaller than the reference value. At this time, if it is detected that the variation evaluation amount F2 is smaller than the reference value, the process is performed. On the other hand, if it is detected that the variation evaluation amount F2 is larger than the reference value, the process returns to step S1.

Next, the control of the Y-axis direction angle θy at the time of reading information data in the holographic device according to the first embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing an operation example of control of the Y-axis direction angle θy at the time of reading in the holography device according to the first embodiment.
As a premise, the angle adjustment in the Bragg diffraction direction is performed, and either the X-axis direction angle θx is adjusted to the angle at which the signal intensity S is maximized at the present time, or the adjustment of the wavelength λ described above has been completed. It is. Alternatively, a sequence in which the control of the Y-axis direction angle θy is performed first and the wavelength λ is performed thereafter may be used.

The Y-axis direction angle adjustment unit 12 controls the variation evaluation amount F calculation unit 9 to set the angle in the Y-axis direction at which the reference light is incident on the surface of the medium 4 to the Y-axis direction center angle θyc set inside in advance. The angle of the reflecting surface of the mirror 8 is adjusted so that
Then, the variation evaluation amount F calculation unit 9 calculates the variation evaluation amount F0 at the center angle θyc in the Y-axis direction (step S21).

Next, the variation evaluation amount F calculation unit 9 causes the Y-axis direction angle adjustment unit 12 to change the angle at which the reference light is incident on the surface of the medium 4 to be the Y-axis direction angle θyc−Δθy. Adjust the angle. Here, the deviation amount Δθy is appropriately set according to the adjustment step of the Y-axis direction angle, that is, coarse adjustment (large value) or fine adjustment (small value), for example, in the range of 0.01 degree to 1.0 degree. You may make it vary by.
As a result, the Y-axis direction angle adjustment unit 12 controls the angle of the reflection surface of the mirror 8 and changes the angle at which the reference light is incident on the surface of the medium 4 to the Y-axis direction angle θyc−Δθy (step S22). .
Next, the variation evaluation amount F calculation unit 9 controls the X-axis direction angle θx, and the variation evaluation amount at the Y-axis direction angle θyc−Δθy at the X-axis direction angle θx at which reproduction light with the maximum signal intensity is obtained. F1 is calculated (step S23).

Next, the variation evaluation amount F calculation unit 9 adjusts the angle of the reflection surface of the mirror 8 so that the angle at which the reference light enters the surface of the medium 4 becomes the Y-axis direction angle θyc + Δθy. A control signal is output to the angle adjustment unit 12.
As a result, the Y-axis direction angle adjusting unit 12 controls the angle of the reflection surface of the mirror 8 and changes the angle at which the reference light is incident on the surface of the medium 4 to the Y-axis direction angle θyc + Δθy (step S24).
Next, the variation evaluation amount F calculation unit 9 controls the X-axis direction angle θx to calculate the variation evaluation amount F2 at the Y-axis direction angle θyc + Δθy at the X-axis direction angle θx at which the maximum reproduction light is obtained ( Step S25).

Then, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F1 is smaller than the variation evaluation amount F2, and at this time, if detecting that the variation evaluation amount F1 is smaller than the variation evaluation amount F2, On the other hand, if it is detected that the variation evaluation amount F1 is larger than the variation evaluation amount F2, the process proceeds to step S30 (step S26).
In the case of YES in step S26 (when it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F2), the process proceeds to step S27, and in this step S27, the variation evaluation amount F calculation unit 9 performs the variation evaluation amount. It is detected whether or not F1 is smaller than the variation evaluation amount F0. At this time, if it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F0, the process proceeds to step S28, while the variation evaluation amount F1 varies. If it is detected that the evaluation amount is greater than F0, the process is terminated.

If YES in step S27 (when it is detected that the variation evaluation amount F1 is smaller than the variation evaluation amount F0), the process proceeds to step S28. In step S28, the variation evaluation amount F calculation unit 9 A control signal is output to the Y-axis direction angle adjustment unit 12 so as to adjust the angle of the reflecting surface of the mirror 8 so that the angle at which the reference light is incident becomes the Y-axis direction angle θyc−Δθy.
As a result, the Y-axis direction angle adjustment unit 12 controls the angle of the reflection surface of the mirror 8 and changes the angle at which the reference light is incident on the surface of the medium 4 to the Y-axis direction angle θyc−Δθy. Proceed to S29.
Then, the variation evaluation amount F calculation unit 9 sets the variation evaluation amount F1 based on a reference value (allowable value of the adjustment residual amount of the variation evaluation amount necessary for signal detection, such as the S / N ratio distribution of the reproduction signal). In this case, if it is detected that the variation evaluation amount F1 is smaller than the reference value, the process is terminated because it is a control limit value, while the variation evaluation amount F1 is the reference value. If it is detected that the value is greater than the value, the process returns to step S21 (step S29).

On the other hand, in step S26, when the variation evaluation amount F calculating unit 9 detects that the variation evaluation amount F1 is larger than the variation evaluation amount F2, the process proceeds to step S30.
In step S30, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F2 is smaller than the variation evaluation amount F0. At this time, it is detected that the variation evaluation amount F2 is smaller than the variation evaluation amount F0. Then, the process proceeds to step S31. On the other hand, when it is detected that the variation evaluation amount F2 is larger than the variation evaluation amount F0, the processing is terminated.

In the case of YES in step S30 (when it is detected that the variation evaluation amount F2 is smaller than the variation evaluation amount F0), the process proceeds to step S31, and in this step S31, the variation evaluation amount F calculation unit 9 A control signal is output to the Y-axis direction angle adjustment unit 12 so as to adjust the angle of the reflection surface of the mirror 8 so that the angle at which the reference light enters the surface becomes the Y-axis direction angle θyc + Δθy.
Thereby, the Y-axis direction angle adjustment unit 12 controls the angle of the reflection surface of the mirror 8 to change the angle at which the reference light is incident on the surface of the medium 4 to the Y-axis direction angle θyc + Δθy, and the process goes to step S32. Proceed.
Then, the variation evaluation amount F calculation unit 9 detects whether or not the variation evaluation amount F2 is smaller than the reference value. At this time, when it is detected that the variation evaluation amount F2 is smaller than the reference value, the process is terminated. On the other hand, if it is detected that the variation evaluation amount F2 is larger than the reference value, the process returns to step S1 (step S32).

Here, as shown in FIG. 7, the signal intensity and the amplitude of the reproduction light output from the detector 6 vary depending on the position of the angle and the position of the wavelength, and either of these is evaluated as a variation evaluation amount F (Fa, Fb, Fc). ) Is used when calculating.
The variation evaluation amount Fa focuses only on the balance between the blocks in the information data page. However, when the signal intensity due to the reproduction light increases as a whole, the variation evaluation amount Fa also increases. Therefore, it is desirable to use an index standardized by the overall intensity. Here, as shown in the following equation (3), the standard deviation σ obtained by the equation (2) is divided by the average strength Bave, and the variation evaluation amount Fb normalized by the signal strength is obtained as shown in FIG. Also, it may be used as the variation evaluation amount F used in the processing of the flowchart in FIG.

The condition for reducing the standardized variation evaluation amount Fb obtained by the above equation (3) is that the variation in signal intensity between blocks is small, that is, the angle (θx and θy) and the wavelength λ are in an appropriate state. It is a condition that the entire information data page is reproduced uniformly.
Furthermore, as an index for adjusting the signal intensity of the entire reproduced light to be larger, as shown in the following expression (4), the standard deviation σ obtained by the expression (2) is set to the square of the average intensity Bave. The variation evaluation amount Fc linked with the intensity may be calculated and used as the variation evaluation amount F used in the processing of the flowcharts in FIGS.
This variation evaluation amount Fc is linked to the signal intensity, and as a condition for decreasing, the variation between the blocks is small and the signal intensity on the entire detection surface is large. That is, the angle (θx and θy) and the wavelength λ are The adjusted information data page is a condition that the entire information data page is reproduced with a uniform and desired intensity.

  Further, as a variation evaluation amount F when adjusting the wavelength λ in the flowchart of FIG. 5, as shown in FIG. 8A, in the block divided in a lattice shape, the detection surface of the detector 6 is parallel to the Y-axis direction. Using the blocks along the opposite sides, the average value of the signal intensity in the blocks B11, B12, and B13 along the side parallel to one Y-axis direction, and the block along the other side parallel to the Y-axis direction You may use the absolute value of the difference with the average value of the signal strength in B31, B32, and B33.

  Similarly, as the variation evaluation amount F when adjusting the Y-axis direction angle θy in the flowchart of FIG. 6, as shown in FIG. 8B, the X-axis of the detection surface of the detector 6 in the block divided into a lattice shape as shown in FIG. Using blocks along opposite sides parallel to the direction, the average value of the signal intensity in blocks B11, B21, and B31 along the side parallel to one X-axis direction, and the other side parallel to the X-axis direction The absolute value of the difference from the average value of the signal intensity in the blocks B13, B23, and B33 along the line may be used.

Note that the adjustment operation of the X-axis direction angle θx, the Y-axis direction angle θy, and the wavelength λ described above is initialized after a certain amount of time elapses when the power is turned on or after the medium is replaced, without playback. The adjustment operation of the wavelength λ and the Y-axis direction angle θy may be performed at a necessary time.
The flowchart of the initial setting and the adjustment operation of the steady wavelength λ is as shown in FIG. 5. The wavelength λ is deviated from the center wavelength λc by the change of −Δλ and + Δλ, and the variation evaluation amount F is smaller. Then, the central wavelength is updated.
The deviation amount Δλ is more efficient when the magnitude of the deviation amount is changed between the initial coarse adjustment and the fine adjustment. That is, the deviation amount Δλ is set large during coarse adjustment and small during fine adjustment.

Similarly, the procedure for adjusting the Y-axis direction angle is also evaluated by deviating the Y-axis direction angle θy from the central Y-axis direction angle θy by the change of −Δθy and + Δθy in the flowchart shown in FIG. The central Y-axis direction angle θ is updated so that the amount F becomes smaller.
The deviation amount Δθy is more efficient when the deviation amount is changed between the initial coarse adjustment and the fine adjustment. That is, the deviation amount Δθy is set large during coarse adjustment and small during fine adjustment.
In addition, the adjustment operation described above can be adjusted periodically during the continuous reproduction operation to cope with a change in ambient temperature that occurs with the passage of time.

Furthermore, as shown in FIG. 9, a method of adjusting the wavelength λ in real time during a normal reproduction operation is also conceivable.
As shown in FIG. 9A, the center wavelength λ0 is deviated by a minute amount Δλ, that is, after reproducing information data of a stack of information pages (unit of storage area for multiplexing information data pages of the media 4), Deviation to negative deviation λ0 (that is, λc) −Δλ, and after reproducing the information data of the information data page of the next stack, deviation to positive deviation λ0 + Δλ is continued, and the reproduction operation of the media 4 is continued. The wavelength may be adjusted almost in real time.

On the other hand, as described above, the deviation is not switched for each unit for sweeping the stack of a plurality of data pages, but the deviation is switched for one page or a plurality of information data pages as shown in FIG. 9B. (Wobbling operation).
Although not shown, the wobbling operation may be made sinusoidal so that a different deviation amount Δλ is assigned to each information data page.

Furthermore, as shown in FIG. 10, a method of adjusting the Y-axis direction angle θy in real time during a normal reproduction operation is also conceivable.
As shown in FIG. 9 (a), the center Y-axis direction angle θyc is deviated by a minute amount Δθy, that is, the information data of the stack of information pages (unit of storage area for multiplexing information data pages of the media 4). After reproduction, the negative deviation θyc−Δθy is deviated, and after the information data of the next stack information data page is reproduced, the deviation is made positive deviation θyc + Δθy, and the reproduction operation of the media 4 is continued, and the above Y-axis direction angle adjustment is performed. Depending on the method, the wavelength may be adjusted substantially in real time.

On the other hand, as described above, the deviation is not switched for each unit for sweeping the stack of a plurality of data pages, but the deviation is switched for one page or a plurality of information data pages as shown in FIG. (Wobbling operation).
Although not shown, the wobbling operation may be made sinusoidal so that a different deviation amount Δθy is assigned to each information data page.

<Second Embodiment>
Next, as a second embodiment, a system configuration corresponding to a ROM (read only memory) type or a write-once type medium in which a holographic recording device and a holographic reproducing device are separated may be employed.
For example, in the system configuration shown in FIG. 11, signal light and reference light are incident from the opposite side of the medium 4 during recording (FIG. 11A), and the reference light is used as phase conjugate reproduction illumination light during reproduction. A reflection hologram is taken as an example (FIG. 11B).

In the case of the configuration shown in FIG. 11, in the holographic recording apparatus shown in FIG. 11A, the angle of the reference beam is changed, and the medium 4 on which the information data is multiplexed and recorded for a plurality of information data pages is used as the holography ROM. create.
Here, as in FIG. 1, the signal light is emitted from the SLM 2, the reference light is emitted from the mirror 8, and the FT lens 3 is disposed at the front part of the SLM 2 for other configurations. Other than that, the configuration is the same as in FIG. A rectangular opening 13 is provided between the SLM 2 and the medium 4.
And the writing process of the information data to the medium 4 is performed by the same process as in the first embodiment described above.
At this time, the reference light is incident on the recording area where the incident light is incident on the medium 4 from the surface opposite to the surface on which the signal light is incident.

Then, in the holographic reproducing device shown in FIG. 11B, at the time of reading, the phase conjugate reproducing illumination light is used instead of the reference light, and the information data reproducing process is performed by the reading process described in the first embodiment. .
In this holographic reproducing device, phase conjugate reproduced illumination light is incident on the same surface as the surface on which signal light is input in the holographic recording device. Thereby, it is not necessary to provide an FT lens on the holography reproducing device side.
Since the phase conjugate reproduction illumination light is configured to be read from behind, it is defined so that the reference light becomes phase conjugate light, and is the same beam as the reference light in FIG.

At this time, the angle of the phase conjugate reproduction illumination light is controlled in the same manner as in the first embodiment by using the angle θ of incidence of the phase conjugate reproduction illumination light by inclining the reflecting surface of the mirror 8 and phase conjugate reproduction. Control is performed so that the illumination light is incident at an angle corresponding to the information data page.
Although not shown, the holographic reproduction device includes a laser device, a detector 6, a shutter 7, a mirror 8, a variation evaluation amount F calculation unit 9, an X-axis direction angle adjustment unit 11, and a Y-axis direction angle adjustment unit 12. Similar to the first embodiment, it is provided as necessary.
The difference from the first embodiment is that the detector 6 is the same as the surface of the medium 4 to which the phase conjugate reproduction illumination light is input via the rectangular opening 14 (the area corresponding to the detection surface of the detector 6). It is arranged on the side.

Therefore, the holographic reproducing device shown in FIG. 11B can be a holographic ROM reproducing device that makes phase conjugate reproduction illumination light incident on the medium 4 from a desired angle and reproduces recorded information data. .
In the above-described holographic ROM reproducing device, it is difficult to make the angle of the reference light at the time of writing and the angle of the phase conjugate reproducing illumination light at the time of reading particularly the same in the configuration. Assuming that different media are loaded, angular deviation is inevitable.
However, as described above, the angle deviation and the wavelength deviation are allowed by adjusting the angle and the wavelength of the phase conjugate reproduction illumination light based on the variation evaluation amount F by the method shown in the second embodiment. Accurate information data can be reproduced.

<Third Embodiment>
Next, a holographic recording / reproducing apparatus according to the third embodiment of the present invention will be described.
In the first and second embodiments, as described above, the information data in each storage area is multiplexed by generating the information data page for each different angle by changing the angle of the reference light. .
On the other hand, the third embodiment is an example applied to a wavelength multiplexing system that controls the laser light source, changes the wavelength of the emitted laser light, and multiplexes each wavelength.
However, in general, the wavelength resolution of transmission holograms is significantly inferior to that of reflection holograms. Therefore, in the case of multiplexing by wavelength, the reflection hologram method, that is, the phase conjugate light of the second embodiment is used. A configuration example in which the information signal is reproduced by using is preferable.

However, in either case of using a transmission hologram or a reflection hologram, the recording process in the third embodiment is not to shift the angle by setting the angle θ in the first and second embodiments to the wavelength λ. Instead, the information data is multiplexed and recorded by a plurality of information data pages by shifting the wavelength for each information data page.
In wavelength multiplexing, the temperature of the VCSEL or the like is controlled and the wavelength of the emitted laser light is changed. Therefore, it is difficult to provide a reference for control beyond the angle. This is effective as a method of reading information data recorded in each information data page.

1 is a block diagram illustrating a configuration example of a holography device according to a first embodiment of the present invention. It is a conceptual diagram explaining the grid | lattice division | segmentation of the detection surface of the detector 6 at the time of reproduction | regeneration of the holography apparatus by the 1st Embodiment of this invention. 6 is a graph showing the signal intensity that the detector 6 receives and outputs the reproduction light from the medium 4. FIG. 5 is a conceptual diagram illustrating variations in the intensity of reference light on the detection surface of the detector 6 due to wavelength shift and angle (incident angle of reference light with respect to the storage surface of the medium 4). It is a flowchart which shows the operation example which correct | amends the shift | offset | difference of wavelength (lambda) in the reproduction | regeneration in embodiment of this invention. 7 is a flowchart illustrating an example of an operation for correcting a shift in a Y-axis direction angle θy during reproduction in the embodiment of the present invention. It is a conceptual diagram which shows the example of a change of the signal intensity | strength and amplitude used when calculating variation evaluation amount F. FIG. It is a conceptual diagram which shows the other example of calculation of the variation evaluation amount F used for the correction | amendment of the shift | offset | difference of wavelength (lambda), and the correction | amendment of an angle ((theta) y). FIG. 6 is a conceptual diagram showing timing for correcting the shift of the wavelength λ using the process of the flowchart of FIG. 5 when reproducing information data. FIG. 7 is a conceptual diagram showing timing for correcting a shift in angle (θy) using the processing of the flowchart of FIG. 6 when reproducing information data. It is a conceptual diagram explaining the holography recording device and holography reproducing | regenerating apparatus in the 2nd Embodiment of this invention.

Explanation of symbols

1,7 ... Shutter 2 ... SLM
3, 5 ... FT lens 4 ... Media 6 ... Detector 8 ... Mirror 9 ... Variation evaluation amount F calculation unit 10 ... Wavelength adjustment unit 11 ... X-axis direction angle adjustment unit 12 ... Y-axis direction angle adjustment unit 13, 14 ... Rectangular opening Part

Claims (12)

By changing the angle of the reference light at the time of recording and sequentially changing the angle of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of the plurality of information data pages, A holographic device that reads data and reproduces recorded information data,
Reference light irradiating means for irradiating the holographic medium with reference light at different angles;
Data detection means for making reproduction light emitted from each information data page incident on a detection surface by the reference light and reproducing information data from the reproduction light;
The reproduction light emitted from the holographic medium by the reference light detects the light intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface, and the angle and wavelength shift of the reference light incident on the holographic medium A reproducing light shift detecting means for detecting
A holography apparatus comprising: a reference light control unit configured to control an incident angle and a wavelength of the reference light based on a detection result of an angle and a wavelength shift of the reproduction light.   The data detection unit divides the information data page into a grid and generates a plurality of blocks on a two-dimensional plane formed by the X-axis direction that is the Bragg diffraction direction and the Y-axis direction perpendicular to the X-axis direction. 2. The holography device according to claim 1, wherein the intensity of the reference light is detected for each block and output as the detected intensity.   The reference light control means calculates a variation evaluation amount between all blocks from the dispersion or standard deviation of the light intensity between the blocks, and controls the wavelength and angle of the reference light so as to minimize this variation evaluation amount. The holographic device according to claim 2, wherein the holographic device is a holographic device.   The reproduction light shift detection means calculates an average intensity that is an average of the intensity of the reproduction light incident on each block, divides the variation evaluation amount by the average intensity, and normalizes the reference light control means. 4. The holography apparatus according to claim 3, wherein the wavelength and angle of the reference light are controlled so as to minimize a standardized variation evaluation amount.   The reproduction light shift detection means calculates an average intensity that is an average of the intensity of the reproduction light incident on each block, and divides the variation evaluation amount by a value obtained by squaring the average intensity to obtain the intensity of the reference light. 4. The holography device according to claim 3, wherein a linked variation evaluation amount is obtained, and the reference light control means controls the wavelength and angle of the reference light so as to minimize the standardized variation evaluation amount. .   The data detection unit scans the reference light while changing the angle of the reference light in the X-axis direction, which is the Bragg diffraction direction, and detects information data at a position where the variation evaluation amount is minimum. The holographic device according to claim 4 or 5.   The reproduction light deviation detecting means detects the wavelength of the reference light and the angle deviation in the Y-axis direction every predetermined period, and the reference light control means determines the wavelength of the reference light and the lateral angle in the Y-axis direction in the period. The holography device according to claim 1, wherein the holography device is adjusted.   The reference light control means alternately changes the wavelength of the reference light between a first wavelength obtained by deviating a negative minute amount from a predetermined wavelength and a second wavelength obtained by deviating a positive minute amount. The holography apparatus according to claim 1, wherein a predetermined wavelength is adjusted according to the variation evaluation amount.   The reference light control means deviates the lateral angle of the reference light in the Y-axis direction by a negative minute amount from the first lateral angle with respect to a predetermined lateral angle and a positive minute amount. The holographic apparatus according to claim 1, wherein the holographic apparatus is alternately changed to a lateral angle of 2, and a predetermined lateral angle is adjusted according to the variation evaluation amount. By changing the wavelength of the reference light at the time of recording and sequentially changing the wavelength of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of the plurality of information data pages, A holographic device that reads data and reproduces recorded information data,
Reference light irradiating means for irradiating the holographic medium with reference light at a different wavelength;
Data detection means for making reproduction light emitted from each information data page incident on a detection surface by the reference light and reproducing information data from the reproduction light;
The reproduction light emitted from the holographic medium by the reference light detects the light intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface, and the angle and wavelength shift of the reference light incident on the holographic medium A reproducing light shift detecting means for detecting
A holography apparatus comprising: a reference light control unit configured to control an incident angle and a wavelength of the reference light based on a detection result of an angle and a wavelength shift of the reproduction light. By changing the angle of the reference light at the time of recording and sequentially changing the angle of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of the plurality of information data pages, A method for reproducing a holographic medium that reads data and reproduces recorded information data,
Irradiating the holographic medium with reference light at different angles;
A process in which data detection means makes the reproduction light emitted from each information data page incident on the detection surface by the reference light and reproduces the information data from the reproduction light;
A reproduction light deviation detecting means detects the light intensity of the reproduction light in each of a plurality of predetermined areas of the detection surface by the reproduction light emitted from the holographic medium by the reference light, and enters the holographic medium of the reference light Detecting the angle and wavelength deviations to be performed;
A method for reproducing a holographic medium, comprising: a step in which a reference light control unit controls an incident angle and a wavelength of the reference light based on a detection result of an angle and a wavelength shift of the reproduction light. By changing the wavelength of the reference light at the time of recording and sequentially changing the wavelength of the reference light to be irradiated on the holographic medium in which the information data is recorded for each of the plurality of information data pages, A method for reproducing a holographic medium that reads data and reproduces recorded information data,
A process in which the reference light irradiation means irradiates the holographic medium with the reference light by changing the wavelength,
A process in which data detection means makes the reproduction light emitted from each information data page incident on the detection surface by the reference light and reproduces the information data from the reproduction light;
The reproduction light deviation detecting means detects the light intensity of the reproduction light in each of a plurality of predetermined regions of the detection surface by the reproduction light emitted from the holographic medium by the reference light, and is incident on the holographic medium of the reference light. Detecting the angle and wavelength shift
A method for reproducing a holographic medium, comprising: a step in which a reference light control unit controls an incident angle and a wavelength of the reference light based on a detection result of an angle and a wavelength shift of the reproduction light.

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