JP2017041288A - Hologram recording medium multiple recording method and hologram recording medium multiple recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate a hologram distortion capable of achieving the improvement of a transfer rate of reproduced data and to compensate a hologram distortion by optimizing a wave surface of reference light in a multi-recorded hologram recording medium.SOLUTION: When a hologram recording medium is reproduced, two polarized states of p-polarized light and s-polarized light are used as reference light incident on the hologram recording medium. In each reference optical path, wave surface controllers 40a, 40b and Galvano-mirrors 50a, 50b for controlling an angle incident on the hologram recording medium 10 are provided. When the hologram multiplied in angle is reproduced, the predetermined page data uses the reference light of the p-polarized light, and the adjacent page data uses the reference light of the s-polarized light so as to perform information reproduction from the recording medium 10. Since the acquired reproduction light advances on the same optical path, the p-polarized light and the s-polarized light are separated by a PBS 17, and each reproduced light is photographed by a camera to reproduce data. The wave surface of the polarized light is acquired based on the camera information of each reproduced image, and the wave surface controllers 40a, 40b are controlled so as to reduce the distortion of the wave surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a holographic recording medium multiplex recording / reproducing method and a holographic recording medium multiplex recording / reproducing apparatus, and more specifically, a holographic recording medium multiplex recording / reproducing method and holographic recording capable of efficiently reproducing page data information multiplex-recorded on a hologram. The present invention relates to a medium multiplex recording / reproducing apparatus.

  In recent years, hologram recording has attracted attention as a high-capacity and high-speed information recording / reproducing system. In hologram recording, two coherent lights from the same light source called reference light and signal light are caused to interfere with each other, and the generated interference fringes are recorded and held as a change in refractive index on a recording medium. The signal light is spatially modulated by a two-dimensional data image called “page data” and irradiated onto a recording medium through a lens. It is possible to multiplex and record multiple page data at the same location on the medium while changing the reference light conditions (for example, incident angle, wavelength, phase, etc. to the recording medium), so the density and capacity are increased. Is possible. Various multiplex methods have been proposed so far, and the one that performs multiplex recording / reproduction while changing the incident angle of irradiation light is called an angle multiplex method (see, for example, Patent Document 1).

  In a recording / reproducing apparatus using the angle multiplexing method, for example, as shown in FIG. 7, a plurality of page data is recorded in the form of a hologram while changing the incident angle of the reference light on the recording medium 410 little by little by a galvanometer mirror 425. To do. Also, during reproduction, when the recording medium 410 is irradiated with reference light under the same conditions as during recording (phase conjugate reproduction) from the side opposite to the reference light irradiation direction during recording, light is emitted by the hologram inside the recording medium 410. Diffracted and reproduced light is obtained. It is possible to read the original information by photographing this with the camera 420 or the like and decoding it (note that the reference numerals given to each member shown in FIG. 7 are the corresponding ones in FIG. 2 (Example 1)). 300 is added to the reference numeral attached to the member).

  By the way, in angle multiplexing, there is a certain range of restrictions on the incident angle of the reference light on the recording medium 410. This is because it is necessary to prevent physical interference from occurring when the signal light and the reference light are incident on the recording medium 410.

  Considering this restriction, for example, if the incident angle of the reference light on the recording medium 410 is a variable range of 30 degrees and the angle interval for angle multiplexing is set in increments of 0.2 degrees, 151 multiplexing is possible. If more holograms are angle multiplexed to the same location on the recording medium 410, the recording density and the recording capacity can be improved. However, it is not always easy to greatly increase the number of angle multiplexing due to problems such as crosstalk.

  By the way, when reproducing the page data recorded on the hologram recording medium (410), the hologram recording medium (410) is irradiated with reference light having a predetermined polarization angle by a half-wave plate (422) or the like disposed in the optical path. . When the reference light is incident on the hologram recording medium (410), it is diffracted by the hologram interference fringes, and reproduced light carrying page data information is output. Thereafter, the reproduction light is incident on the camera (420) or the like, and the page data information is imaged by a two-dimensional image sensor such as the camera (420).

JP 2006-154163 A

However, when increasing the amount of data per page data, the sensitivity of the camera increases due to the increase in the number of pixels of the image sensor and the higher definition of the pixels, as well as the increase in the number of pixels of the image sensor and the higher definition of the pixels. And high-speed data transfer are required.
Even when the frame rate of the camera is improved, it is necessary to increase the sensitivity of each pixel of the camera and to increase the speed of data transfer.
As described above, in the conventional apparatus, the transfer speed of the reproduction data is limited by the performance of the camera. In this case, the function of the camera itself must be improved in order to improve the transfer speed of the reproduction data.

  On the other hand, in recent years, a photosensitive resin material (hereinafter referred to as a photopolymer) is frequently used as a write-once recording medium. A medium based on a photopolymer has an advantage that the multiplicity index is high and data can be retained stably for a long period of time. However, in the case of a photopolymer, a hologram (interference fringes) is recorded by generating a refractive index difference inside the recording medium. At this time, medium shrinkage occurs due to photopolymerization. In addition, when a temperature difference occurs between signal recording and signal reproduction, the recording medium may contract or expand due to the influence of the temperature difference. When the recording medium contracts or expands, so-called interference fringe distortion (hologram recording information distortion: hereinafter referred to as hologram distortion) occurs in which the interference fringes recorded in the medium are distorted.

Even if reference light similar to that at the time of recording is incident on the distorted interference fringes, it becomes difficult to reproduce the recorded bit data without error, so that the SNR (Signal to Noise Ratio) of the reproduced data is lowered.
Therefore, a method for optically compensating for hologram distortion and improving the SNR of reproduced data has been studied. Specifically, this is a method for controlling the wavelength, incident angle, and wavefront of the reference light.

However, the method for compensating for the hologram distortion based on the wavelength and the incident angle of the reference light is not sufficiently compensated when the NA of the lens in the signal light path becomes high due to the recent increase in the density of information recording.
Therefore, attention has been paid to a technique that can compensate for hologram distortion even when the lens NA is increased by optimizing the wavefront of the reference light.

  The present invention has been made in view of the above circumstances, and in a multiplex recorded hologram recording medium, a hologram capable of improving the transfer speed of reproduction data and optimizing the wavefront of reference light to compensate for hologram distortion It is an object of the present invention to provide a recording medium multiplex recording / reproducing method and a hologram recording medium multiplex recording / reproducing apparatus.

The first hologram recording medium multiplex recording / reproducing apparatus of the present invention comprises:
For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Reproduction reference light separating means for separating the reproduction reference light into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
A wavefront for controlling the wavefront of each reproduction reference light disposed in the optical path of each of the p-polarized light and the s-polarized reproduction reference light separated by the reproduction reference light separating means so as to reduce the distortion of the hologram. Control means;
P-polarized light irradiation means and s-polarized light irradiation means for irradiating p-polarized light and s-polarized light of the reproduction reference light to the same position of the hologram recording medium with different incident angles;
Deflection angle adjusting means for adjusting to the reference light incident angle state in which angle-multiplexed recording and page data information of the next step can be reproduced,
Reproduction light that separates p-polarization reproduction light and s-polarization reproduction light output from the hologram recording medium in response to irradiation of p-polarized light and s-polarized reproduction reference light by the p-polarization irradiation means and the s-polarization irradiation means. Separating means;
P-polarization imaging means and s-polarization imaging means for imaging the page data information relating to the separated p-polarized reproduction light and s-polarization reproduction light, respectively, and converting them into electrical information signals;
It is characterized by having.

The second hologram recording medium multiplex recording / reproducing apparatus of the present invention comprises:
For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Wavefront control means for controlling the wavefront of the reproduction reference light arranged in the optical path of the reproduction reference light so as to reduce distortion of the hologram;
Reproduction reference light separating means for separating the reproduction reference light wavefront controlled by the wavefront control means into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
P-polarized light irradiation means and s-polarized light irradiation means for irradiating p-polarized light and s-polarized light of the reproduction reference light to the same position of the hologram recording medium with different incident angles;
Deflection angle adjusting means for adjusting to the reference light incident angle state in which angle-multiplexed recording and page data information of the next step can be reproduced,
Reproduction light that separates p-polarization reproduction light and s-polarization reproduction light output from the hologram recording medium in response to irradiation of p-polarized light and s-polarized reproduction reference light by the p-polarization irradiation means and the s-polarization irradiation means. Separating means;
P-polarization imaging means and s-polarization imaging means for imaging the page data information relating to the separated p-polarized reproduction light and s-polarization reproduction light, respectively, and converting them into electrical information signals;
It is characterized by having.

The third hologram recording medium multiplex recording / reproducing apparatus of the present invention comprises:
Reference light for reproduction is applied to a hologram recording medium in which a plurality of interference fringes formed by interfering signal light carrying information related to page data and reference light for recording are overlapped at the same position and subjected to angle multiplexing recording. In a hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by making it incident at a predetermined angle,
First reference light polarization adjusting means for adjusting and outputting the reproduction reference light to first reference light that is either p-polarized light or s-polarized light;
First wavefront control means for controlling the wavefront of the first reference light from the first reference light polarization adjusting means so as to reduce hologram distortion;
First deflection angle adjustment means for adjusting an emission angle of the first reference light from the first wavefront control means so as to be incident on the hologram recording medium at a predetermined angle;
Of the first reference light output from the first deflection angle adjusting means and incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is converted into the first reference light among p-polarized light and s-polarized light. Second reference light polarization adjusting means for adjusting and outputting the second reference light having a different polarization from
For the second reference light from the second reference light polarization adjusting means, the wavefront of the second reference light is reduced so that the distortion of the wavefront of the first reference light and the distortion of the hologram due to transmission through the hologram recording medium are reduced. Second wavefront control means for controlling
Second deflection angle adjusting means for adjusting an exit angle so that the second reference light from the second wavefront control means is incident on the hologram recording medium at an angle different from the predetermined angle;
Reproduction light separating means for separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
Two image pickup means for picking up images of hologram information carried on the two separated reproduction lights;
It is characterized by comprising.

  Here, the “hologram recording medium multiplex recording / reproducing apparatus” includes not only those having a multiplex recording / reproducing function but also those having only a function of reproducing multiplex recorded holograms.

  It is preferable that noise light trapping means for trapping noise light output out of the optical path of the second reference light transmitted through the hologram recording medium is provided.

  In the first, second, and third hologram recording medium multiplex recording / reproducing apparatuses described above, the multiplex recording / reproducing means is preferably a galvanometer mirror that deflects each linearly polarized light.

  In addition, signal light is emitted when recording page data, while a modulation element that modulates light based on page data is recorded at a predetermined position where reproduction light is incident when reproducing page data. When the page data is reproduced, there is provided an element replacement mechanism for switching the image pickup elements for picking up the page data information carried by either the p-polarized light or the s-polarized linearly polarized light out of the reproduced light reproduced. It is preferable to provide.

The first hologram recording medium multiplex recording / reproducing method of the present invention comprises:
For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Separating the reference light for reproduction into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
Controlling the wavefront of each reproduction reference light so that the distortion of the hologram is reduced in the optical path of each of the separated p-polarized light and s-polarized reproduction reference light;
Irradiating p-polarized light and s-polarized light of the reproduction reference light at the same position on the hologram recording medium with different incident angles,
Separating the p-polarized reproduction light and the s-polarized reproduction light output from the hologram recording medium according to the irradiation of the p-polarized light and the s-polarized light by the p-polarized light irradiation means and the s-polarized light irradiation means,
The page data information related to the separated p-polarized reproduction light and s-polarized reproduction light is imaged and converted into an electrical information signal,
After that, the process of reproducing the page data information of the next step is repeatedly performed by adjusting to the reference light incident angle state where the page data information of the next step recorded by angle multiplexing can be reproduced,
It is characterized by this.

The second hologram recording medium multiplex recording / reproducing method of the present invention includes:
For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Controlling the wavefront of the reproduction reference light disposed in the optical path of the reproduction reference light so as to reduce distortion of the hologram;
The reproduction reference light wavefront controlled by the wavefront control means is separated into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other,
Irradiating p-polarized light and s-polarized light of the reproduction reference light at the same position on the hologram recording medium with different incident angles,
Separating the p-polarized reproduction light and the s-polarized reproduction light output from the hologram recording medium in accordance with the irradiation of the p-polarized light and the s-polarized reproduction reference light by the p-polarized light irradiation means and the s-polarized light irradiation means,
The page data information related to the separated p-polarized reproduction light and s-polarized reproduction light is imaged and converted into an electrical information signal,
After that, the process of reproducing the page data information of the next step is repeatedly performed by adjusting to the reference light incident angle state where the page data information of the next step recorded by angle multiplexing can be reproduced,
It is characterized by this.

Furthermore, the third hologram recording medium multiplex recording / reproducing method of the present invention provides:
Reference light for reproduction is applied to a hologram recording medium in which a plurality of interference fringes formed by interfering signal light carrying information related to page data and reference light for recording are overlapped at the same position and subjected to angle multiplexing recording. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by making it incident at a predetermined angle,
Adjusting the reproduction reference light to a first reference light that is either p-polarized light or s-polarized light, and outputting the first reference light;
Controlling the wavefront of the first reference beam so as to reduce the distortion of the hologram;
For the first reference light, the incident angle is adjusted so as to enter the hologram at a predetermined angle,
Of the first reference light incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is adjusted to the second reference light that is different from the first reference light in p-polarized light and s-polarized light. Output
Controlling the wavefront of the second reference light so as to reduce the distortion of the wavefront of the first reference light and the distortion of the hologram due to the transmission of the hologram recording medium;
Adjusting the incident angle so that the second reference light is incident on the hologram recording medium at an angle different from the predetermined angle,
Separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
The hologram information carried on the two separated reproduction lights is imaged by two imaging means, respectively.
It is characterized by this.

  Here, the “hologram recording medium multiplex recording / reproducing method” means not only a multiplex recording process and a multiplex recording reproduction process, but also a process specialized to multiplex recorded hologram reproduction. It shall be called including.

According to the hologram reproducing method and apparatus of the present invention, the reference light at the time of reproduction is separated into p-polarized light and s-polarized light, and these polarized lights are simultaneously incident on the same position of the hologram recording medium with different incident angles. Since the page data information that is multiplexed and recorded on these hologram recording media is sequentially reproduced every two pages by using the multiple recording and reproduction method, the data per page of the page data in the multiplexed recording hologram The transfer speed of the data reproduced from the hologram can be improved without improving the functions of the camera such as increasing the amount or improving the frame rate of the camera.

  In addition, the reproduction reference light for reproducing each page data is controlled so as to reduce the distortion of its wavefront before irradiating the hologram recording medium. The SNR of data can be improved.

It is the schematic for demonstrating the principle of the hologram recording-medium multiplex recording / reproducing apparatus which concerns on embodiment of this invention. It is the schematic which shows the optical system of the hologram recording-medium multiplex recording / reproducing apparatus which concerns on Example 1 of this invention. It is the schematic which shows the optical system of the hologram recording-medium multiplex recording / reproducing apparatus which concerns on Example 2 of this invention. It is the schematic which shows the optical system of the hologram recording-medium multiplex recording / reproducing apparatus which concerns on Example 3 of this invention. It is a photograph which shows the data obtained by the hologram recording-medium multiplex recording / reproducing apparatus which concerns on embodiment of this invention. It is the schematic which shows a part of optical system of the modification of the hologram recording medium multiplex recording / reproducing apparatus based on Example 3 of this invention. It is the schematic which shows the optical system of the hologram recording-medium multiplex recording / reproducing apparatus based on a prior art.

Hereinafter, a hologram recording medium multiplex recording / reproducing method and a hologram recording medium multiplex recording / reproducing apparatus according to embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a reproduction principle of a hologram recording medium capable of simultaneously reproducing two pages of page data by compensating for distortion of the hologram recording medium and distortion of the reference light wavefront.

Two reference states of p-polarized light and s-polarized light are used as reference light incident on the hologram recording medium when reproducing the hologram recording medium.
Wavefront controllers 40a and 40b for controlling the wavefront, and galvanometer mirrors 50a and 50b for controlling the incident angle on the hologram recording medium 10, each including a phase modulation SLM, a deformable mirror, and the like in each reference optical path. Provide. When reproducing an angle-multiplexed hologram, predetermined page data uses p-polarized reference light, and page data adjacent to the predetermined page data uses s-polarized reference light. Are simultaneously incident on the recording medium 10. Reconstructed light obtained by diffracting each reference light by a hologram travels on the same optical path. For this reason, PBS (polarization separation means) is provided in the reproduction optical path to separate p-polarized reproduction light and s-polarized reproduction light, and data can be reproduced by imaging each reproduction light with a camera. The wavefronts of the respective polarizations control the wavefront controllers 40a and 40b in the reference optical path so that the reproduced image is optimized based on the information of the camera that captures each reproduced image.
Hereinafter, three examples will be specifically described.

<Example 1>
The hologram recording medium multiplex recording / reproducing apparatus shown in FIG. 2 according to the first embodiment is configured as a recording / reproducing apparatus having a hologram recording function and a reproducing function.
Note that the hologram recording medium 110 is made of a photopolymer and has a configuration corresponding to the phase conjugate type.
However, the material of the hologram recording medium 110 according to the apparatus of the present invention is not limited to the photopolymer, and the optical system is not necessarily limited to the phase conjugate type.

  As shown in FIG. 2, at the time of recording, the coherent laser beam emitted from the laser light source 111 passes through a shutter (not shown), and the beam diameter is expanded by a beam expander including a diverging lens 112 and a collimating lens 113. The light passes through the half-wave plate 114, is deflected at a right angle by the mirror 115, and is split into two light beams by a polarization beam splitter (PBS: hereinafter simply referred to as PBS) 116.

  A light beam (signal carrying light: p-polarized light) traveling leftward from the PBS 116 passes through the PBS 117 and is not shown in FIG. 2. A spatial light modulator (SLM (amplitude modulator): hereinafter simply referred to as SLM: recording) At times, an SLM is disposed so as to replace the camera 130 shown in the figure, and is spatially modulated by the SLM to be signal light carrying page data information consisting of a digital image. The amplitude modulation SLM is arranged just like the amplitude modulation SLM 460 shown in FIG.

  Also, the signal light emitted (reflected) from the SLM changes in polarization state from the incident state depending on the page data to become s-polarized light, and is reflected downward in the drawing by the PBS 117 and is reflected by the lens (FTL) 118. The hologram recording medium 110 is irradiated with an optical Fourier transform.

  On the other hand, a light beam (s-polarized light) traveling downward from the PBS 116 in the figure is used as reference light (recording reference light) so that the half-wave plate 122 (the optical axis of the half-wave plate 122 matches the polarization direction of the incident light). It is deflected at right angles by the mirror 123, but is reflected by the PBS 124 and is directed downward from the PBS 124 in the figure. This light beam is angle-controlled by a galvanometer mirror 125, and is irradiated at a different angle from the signal light to the place where the signal light in the recording medium 110 is irradiated via the relay lens 126, and thereby the recording material of the recording medium 110 is recorded. A refractive index change according to the intensity of interference fringe pattern light is induced therein, and this is held as hologram information.

  In this embodiment, since angle multiplexing recording is assumed, the page data is displayed on the SLM, and the display of the page data on the SLM is sequentially updated, and the reference is made for each update. By changing the incident angle of light on the recording medium little by little by the galvanometer mirror 125, it becomes possible to multiplex-record different page data at the same position in the recording medium, and to store information at high density. Yes.

  Note that a measurement control unit (not shown) performs drive control of the laser light source 111 and angle control of the galvano mirror 125 at the time of recording, and instructs the SLM to send and display page data.

Next, the reproducing function of the hologram recording medium multiple recording / reproducing apparatus of the first embodiment will be described with reference to FIG.
As shown in FIG. 2, when reproducing the page data information recorded on the hologram recording medium 110, the polarization direction of the reference light (from s-polarized light to p-polarized light) is adjusted by adjusting the position of the half-wave plate 122. )Convert. The reference light is reflected by the mirror 123 and then reaches the PBS 124. However, since the reference light is converted to p-polarized light by the half-wave plate 122, the reference light travels straight through the PBS 124.

Next, the reference beam is split into two beams by a beam splitter (BS) 131 disposed in the reproduction reference beam path. The reference light reflected by the beam splitter (BS) 131 has its wavefront controlled by the wavefront controller 140 a and is reflected by the mirror 132 and reaches the PBS 135, but passes through the PBS 135 because it is in a p-polarized state. On the other hand, the reference light transmitted through the beam splitter (BS) 131 is converted into s-polarized light by the half-wave plate 134, the wavefront is controlled by the wavefront controller 140b, the angle is controlled by the galvanometer mirror 150b, and reaches the PBS135. Since it is in the s-polarized state, it is reflected by this PBS 135.

  The p-polarized light transmitted through the PBS 135 and the s-polarized light reflected by the PBS 135 reach the galvano mirror 150a so as to overlap each other, and the galvano mirror 150a converts the p-polarized reproduction reference light and the s-polarized reproduction reference light. On the other hand, the incident angle for performing the angle multiplexing process is controlled.

  That is, the incident angle of the reproduction reference light 2 on the hologram recording medium 110 is different from the incident angle of the reproduction reference light 1 (usually, it differs by the incident angle of the adjacent step in which page data is recorded). The rotation angle of the galvanometer mirror 150b is controlled. In other words, the galvanometer mirror 150b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light that are simultaneously incident on the recording medium 110.

Further, as described above, by adjusting the angle of the s-polarized reproduction reference light from the wavefront controller 140b with the galvanometer mirror 150b, the incident angle on the s-polarized recording medium 110 is set to the p-polarized recording medium 110. Is controlled so as to give an angle between adjacent pages of the angle-multiplexed recording hologram.
A relay lens 136 is disposed between the galvanometer mirror 150a and the hologram recording medium 110.
As described above, the s-polarized reproduction reference light and the p-polarized reproduction reference light incident on the recording medium 110 are used for recording from the back side to the place where the signal light in the recording medium 110 is irradiated. Irradiation is from a direction opposite to the incident direction of the reference light.

As described above, the reproduction light of the predetermined page data is emitted from the hologram recording medium 110 by the irradiation of the s-polarized reproduction reference light, and the predetermined page is output from the hologram recording medium 110 by the irradiation of the p-polarization reproduction reference light. The reproduction light of the page data adjacent to the data is emitted.
These two emitted reproduction lights are emitted in the same direction (upward in the figure) and irradiated to the PBS 117 through the lens 118. In this PBS 117, the p-polarized reproduction light is transmitted and the s-polarized reproduction light is reflected. Therefore, the page data information carried by the p-polarized reproduction light is incident on the camera 120 and imaged. On the other hand, the page data information carried by the reproduction light that is s-polarized light enters the camera 130 and is imaged.

  In the reproduction light information acquired by the camera 120, for example, an evaluation value represented by the following expression is calculated, and the wavefront controller 140a is controlled so that the evaluation value becomes high.

  Similarly, the wavefront controller 140b is controlled based on the reproduction light information acquired by the camera 130. Thereby, reproduction data with a high SNR can be obtained. Moreover, since the hologram distortion of adjacent page data is similar, the set values of the wavefront controllers 140a and 140b for compensation are also similar. Therefore, only the wavefront controller 140a (or 140b) may be controlled, and the wavefront controller 140b (or 140a) may be controlled using the same value as the wavefront controller 140a (or 140b).

  Furthermore, in consideration of the fact that the hologram distortion between adjacent page data is similar, the wavefront controllers 140a and 140b may be controlled by the average value of the reproduction light information acquired by the camera 120 and the camera 130, respectively. Good.

This also provides reproduction data with a high SNR.
5A shows the p-polarized reproduction data (page number 003) from the camera 120, and FIG. 5B shows the s-polarized reproduction data (page number 00) from the camera 130.
4). As described above, since the reproduction data of the two-page data having a high SNR can be obtained at the same time, the data transfer speed can be greatly improved.

<Example 2>
The hologram recording medium multiplex recording / reproducing apparatus shown in FIG. 3 according to the second embodiment is configured as a recording / reproducing apparatus having a hologram recording function and a reproducing function, as in the first embodiment.
Since the hologram recording medium multiplex recording / reproducing apparatus of the second embodiment is mostly configured in the same manner as that of the first embodiment, the same reference numerals of the corresponding members of the first embodiment are used for these similar members. The reference numerals to which are added are shown, and detailed description is omitted.
The feature of the second embodiment is that the wavefront controller 240 performs wavefront control before the reproduction reference light is separated into p-polarized light and s-polarized light by the BS 231.

That is, the reproduction reference light transmitted through the PBS 224 has its wavefront controlled by the wavefront controller 240 and is divided into two systems by the beam splitter (BS) 231.
Since the reproduction reference light transmitted through the beam splitter (BS) remains p-polarized light, it passes through the PBS 235 and reaches the galvanometer mirror 250a.
On the other hand, the reproduction reference light reflected by the beam splitter (BS) 231 is incident on the half-wave plate 234 via the mirror 232, and p-polarized light is converted to s-polarized light. Thereafter, the reproduction reference light converted into s-polarized light is reflected by the galvanometer mirror 250b, reflected by the PBS 235, and reaches the galvanometer mirror 250a.

The subsequent operation on the reference light for reproduction is the same as that of the first embodiment.
That is, the incident angle of the reproduction reference beam 2 on the hologram recording medium 210 is different from the incident angle of the reproduction reference beam 1 (usually, it differs by the incident angle of the adjacent step in which page data is recorded). The rotation angle of the galvano mirror 250b is controlled. In other words, the galvanometer mirror 250b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light that are simultaneously incident on the recording medium 210.

  Further, as the wavefront control method, as in the first embodiment, in the reproduction information acquired by the camera 220 and the camera 230, the evaluation values represented by the above-described expression (1) are calculated, and the average value becomes high. The wavefront controller 240 is controlled as follows. Since the hologram distortion of adjacent pages is similar, reproduced data having a high SNR is obtained for both p-polarized light and s-polarized light. Similarly to the first embodiment, the evaluation value may be calculated using only the camera 220 or the reproduction data of the camera 230, and the wavefront controller 240 may be controlled so that the value becomes higher.

<Example 3>
The hologram recording medium multiplex recording / reproducing apparatus shown in FIG. 4 according to the third embodiment is configured as a recording / reproducing apparatus having a hologram recording function and a reproducing function, as in the first embodiment.
Here, since the optical configuration related to the hologram recording function is the same as in the first and second embodiments, detailed description is omitted, and only the optical configuration related to the reproducing function will be described.

  As shown in FIG. 4, when reproducing the page data information recorded on the hologram recording medium 310, the polarization direction of the reference light is changed (from s-polarized light to p-polarized light) by adjusting the half-wave plate 322. To do. The reference light is reflected by the mirror 323 and then reaches the PBS 324. Since the reference light is converted to p-polarized light by the half-wave plate 322, the reference light travels straight through the PBS 324. Next, the light is reflected downward in the figure by the wavefront controller 340a and passes through the PBS 335 because it is p-polarized light. The p-polarized reproduction reference light that has traveled straight through the PBS 335 passes through the galvanometer mirror 350a and the relay lens 336 for angle control, and the recording reference light on the back side of the recording medium 310 is irradiated with the signal light. Irradiation is from a direction opposite to the incident direction.

By the way, the reproduction reference light 1 irradiated on the hologram recording medium 310 is diffracted inside the hologram recording medium 310 to generate reproduction light. However, most of the irradiation light does not contribute as reproduction light, but the hologram. It passes through the recording medium 310 as it is.
In the present embodiment, a part of the irradiation light transmitted in this way is used as the reproduction reference light 2 to irradiate the hologram recording medium 310 again, and the reproduction speed of data from the hologram recording medium 310 is about doubled. To increase.

  That is, the p-polarized light that has passed through the hologram recording medium 310 is used as the reproduction reference light 2, travels back through the incident path of the recording reproduction light, passes through the relay lens 326, is reflected by the galvanometer mirror 325, travels straight through the PBS 324, The light is reflected leftward in the drawing by the mirror 332 and reaches the half-wave plate 334. In the half-wave plate 334, p-polarized light is converted into s-polarized light, and thereafter the reproduction reference light 2 reaches the PBS 335 via the wavefront controller 340b and the galvanometer mirror 350b. Since the reproduction reference light 2 at this time is s-polarized light, it is reflected downward in the figure by the PBS 335 and irradiated with the signal light in the hologram recording medium 310 via the galvano mirror 350a and the relay lens 336 for controlling the angle. Is irradiated from the direction opposite to the incident direction of the recording reference light on the back side.

  Note that the incident angle of the reproduction reference beam 2 on the hologram recording medium 310 is different from the incident angle of the reproduction reference beam 1 (usually, it differs by the incident angle of the adjacent step in which page data is recorded). The rotation angle of the galvano mirror 350b is controlled. In other words, the galvanometer mirror 350b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light that are simultaneously incident on the recording medium 310.

  As described above, the second reproduction light is emitted from the hologram recording medium 310 by the irradiation of the reproduction reference light 2. The second reproduction light is emitted in the same direction (upward in the figure) as the first reproduction light emitted from the hologram recording medium 310 by the irradiation of the reproduction reference light 1, and passes through the lens 318 to the PBS 317. Irradiated. In this PBS 317, the first reproduction light that is p-polarized light is transmitted and the second reproduction light that is s-polarized light is reflected, so that the page data information carried by the first reproduction light is incident on the camera 320. On the other hand, the page data information carried by the second reproduction light is incident on the camera 330 and imaged.

Thereafter, the two reproduction reference lights are galvano mirror 325 and galvano mirror 350a.
, B, the incident angle to the hologram recording medium 310 is controlled so that angle-multiplexed recording is sequentially reproduced.
As a result, two page data recorded by angle multiplexing can be simultaneously reproduced without increasing the length of reference light irradiation or increasing the power of the light source, and the reproduction speed of data from the hologram recording medium 310 can be increased. It can be increased to about 2 times.

  A measurement control unit (not shown) performs drive control of the laser light source 311 and angle control of the galvanometer mirrors 325, 350a, and 350b during reproduction, and processes the page data information signal output from the cameras 320 and 330. Instruct to display as a page data image on a monitor (not shown).

  Further, when the first reproduction light and the second reproduction light described above are compared, the amount of light obtained by each camera at the time of imaging usually differs. This is because among the reproduction reference lights 1 and 2 irradiated on the hologram recording medium 310, the reflected light amount, diffracted light amount, absorbed light amount in the hologram recording medium 310, and the absorbed light amount in optical parts such as mirrors and PBSs This is because the power of the reference light during reproduction in the reproduction reference light 2 is lower than that in the reproduction reference light 1 due to the amount of reflected light.

  Therefore, in this embodiment, a light reducing means such as an ND filter (other light reducing means may be used: not shown) is provided in front of the lens of the camera 320 on which the first reproduction light is incident. By adjusting the amount of light incident on the camera 320, the light amounts of the two page data can be made equal even if the reproduction times of the two page data are made equal.

  Further, like the reproduction reference light 1, most of the reproduction reference light 2 is transmitted through the hologram recording medium 310. Therefore, in the present embodiment, noise light trap means (not shown) for trapping the transmitted light is provided so that the transmitted light becomes stray light and does not adversely affect the noise light.

  That is, of the reproduction reference light 2 irradiated on the hologram recording medium 310, the s-polarized light transmitted through the hologram recording medium 310 is reflected to the right in the drawing by the PBS 324 via the relay lens 326 and the galvanometer mirror 325. , And reflected by the mirror 323 and converted to p-polarized light by the half-wave plate 322. Since the converted p-polarized light can pass through the PBS 316 and become noise light output to the outside, noise light trapping means is provided in the vicinity of the upper portion of the PBS 316 in the figure to trap the noise light. As a result, the light does not return to the hologram recording medium 310 again, and the signal quality of the page data to be reproduced can be prevented from being lowered.

  The noise light trap means is preferably a light absorbing material or a beam pocket, but is not limited to this.

  Further, since the hologram recording medium multiplex recording / reproducing apparatus according to the present embodiment is configured as a recording / reproducing apparatus having a hologram recording function and a reproducing function, the SLM used at the time of recording is shown in FIG. The camera 330 used at the time of reproduction shown in the figure can be switched and installed. For example, the SLM and the camera 330 are respectively placed on a linear motion plate that moves linearly or on a rotary plate that rotates. It is preferable to dispose the corresponding SLM or camera 330 on the optical path by switching and moving the linear motion plate or the rotating plate. Further, it is preferable that the start of the switching movement is automatically performed according to the switching timing at the time of recording / reproduction.

As a wavefront control method, as in the first embodiment, the evaluation values represented by the expression (1) are calculated in the reproduction data acquired by the camera 320 and the camera 330 so that the respective evaluation values become high. The respective wavefront controllers 340a and 340b are controlled. Since the reference light wavefront control of s-polarized light can simultaneously control the distortion of the wavefront caused by the transmission through the recording medium, reproduction data having a higher SNR than before can be obtained.

  In the third embodiment, for example, as shown in FIG. 6, the number of optical elements is reduced so that the optical path of the reproduction reference light 1 and a part of the optical path of the reproduction reference light 2 are shared. You may make it make it.

  That is, as shown in FIG. 6, at the time of reproduction, the reproduction reference light 1 incident as p-polarized light is irradiated to the PBS 524 through the mirror 523, and is transmitted to the left in the drawing by the PBS 524, thereby controlling the wavefront. The position where the signal light in the hologram recording medium 510 is irradiated through the device 540, and further the angle control galvano mirror 550 and the relay lens 536 are opposed to the incident direction of the recording reference light on the back surface side. Irradiated from such a direction.

  Of the reference light for reproduction 1 irradiated onto the hologram recording medium 510, the p-polarized light that has passed through the hologram recording medium 510 is used as the reference light for reproduction 2, and reverses the incident path of the reproduction light for recording. Passes, is reflected by the galvanometer mirror 525, enters the half-wave plate 534, and is converted from p-polarized light to s-polarized light. The reproduction reference light 2 converted to s-polarized light is reflected leftward in the drawing by the PBS 524, reflected by the wavefront controller 540, and transmitted through the galvano mirror 550 and the relay lens 536 for angle control in the hologram recording medium 510. The place irradiated with the reproduction reference light 1 is irradiated on the back side thereof from a direction opposite to the incident direction of the recording reference light.

This makes it possible to perform angle-multiplexed recording / reproduction of two page data at the same time without compensating for a long time of reference light irradiation or increasing the power of the light source and compensating for distortion of the reference light wavefront. As in the case of No. 1, the reproduction speed of data from the hologram recording medium 510 can be increased about twice.
However, in this modified example, when recording data, the PBS 524 is rotated 90 degrees in the direction of arrow A, and the recording reference light that is s-polarized light incident from the mirror 523 direction is reflected on the polarization reflection surface of the PBS 524. It is necessary to set so as to be reflected downward in the figure.

  Further, each of the above-described embodiments has both a recording function and a reproducing function. However, the hologram recording medium multiplex recording / reproducing apparatus of the present invention may have only a reproducing function. It doesn't matter.

As described above, in angle multiplexing recording and reproduction, the angle and position of the galvanometer mirror are changed little by little. Specifically, for example, reference light is incident on the axis of signal light. The angle is in the range of 55 degrees to 75 degrees (within the range in which the light emitting end structure and the emitted light do not physically interfere with vignetting when the signal light and the reference light are incident on the recording medium), for example, 0.2 degrees. It is only necessary to record or reproduce page data information in the area each time it is changed.

In each of the above embodiments, a part of the first deflection angle adjusting means (for example, the galvanometer mirror 150a of the first embodiment) and the second deflection angle adjusting means (for example, the galvanometer mirrors 150a, 150b of the first embodiment). (For example, the galvano mirror 150a of the first embodiment is configured using the same deflection angle adjusting means, but it is also possible to adopt a configuration in which these two deflection angle adjusting means do not have common elements.
The noise light trap means of each embodiment described above is provided in the vicinity of the optical element from which the noise light is output. However, the noise light is guided from this position by an optical fiber or the like to be separated from the element. Noise light may be trapped at the position.
In addition, if the concept of the present invention is extended and used, it can be applied to various multiplexing methods such as peritropic multiplexing other than angle multiplexing.

111, 211, 311, 411 Laser light source 112, 212, 312, 412 Divergent lens 113, 213, 313, 413 Collimate lens 114, 122, 134, 214, 222, 234, 314, 322, 334, 414, 422, 534 Half-wave plates 115, 123, 132, 215, 223, 232, 315, 323, 332, 415, 423, 432, 523 Mirrors 17, 116, 117, 124, 135, 216, 217, 224, 235, 316, 317 324, 335, 416, 417, 424, 524
Polarizing beam splitter (PBS) 131, 231 Beam splitter (BS)
118, 126, 136, 218, 226, 236, 318, 326, 336, 418, 426, 436, 518, 526, 536 Lens 10, 110, 210, 310, 410, 510 Hologram recording medium (recording medium) 20, 30, 120, 130, 220, 230, 320, 330, 420 Cameras 50a, 50b, 125, 150a, 150b, 225, 250a, 250b, 325, 350a, 350b, 425, 450, 525, 550 Galvano mirror 460 Amplitude modulation SLM
40a, 40b, 140a, 140b, 240, 340a, 340b, 540
Wavefront controller

Claims (7)

For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Reproduction reference light separating means for separating the reproduction reference light into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
A wavefront for controlling the wavefront of each reproduction reference light disposed in the optical path of each of the p-polarized light and the s-polarized reproduction reference light separated by the reproduction reference light separating means so as to reduce the distortion of the hologram. Control means;
P-polarized light irradiation means and s-polarized light irradiation means for irradiating p-polarized light and s-polarized light of the reproduction reference light to the same position of the hologram recording medium with different incident angles;
Deflection angle adjusting means for adjusting to the reference light incident angle state in which angle-multiplexed recording and page data information of the next step can be reproduced,
Reproduction light that separates p-polarization reproduction light and s-polarization reproduction light output from the hologram recording medium in response to irradiation of p-polarized light and s-polarized reproduction reference light by the p-polarization irradiation means and the s-polarization irradiation means. Separating means;
P-polarization imaging means and s-polarization imaging means for imaging the page data information relating to the separated p-polarized reproduction light and s-polarization reproduction light, respectively, and converting them into electrical information signals;
A holographic recording medium multiplex recording / reproducing apparatus comprising: For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Wavefront control means for controlling the wavefront of the reproduction reference light arranged in the optical path of the reproduction reference light so as to reduce distortion of the hologram;
Reproduction reference light separating means for separating the reproduction reference light wavefront controlled by the wavefront control means into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
P-polarized light irradiation means and s-polarized light irradiation means for irradiating p-polarized light and s-polarized light of the reproduction reference light to the same position of the hologram recording medium with different incident angles;
Deflection angle adjusting means for adjusting to the reference light incident angle state in which angle-multiplexed recording and page data information of the next step can be reproduced,
Reproduction light that separates p-polarization reproduction light and s-polarization reproduction light output from the hologram recording medium in response to irradiation of p-polarized light and s-polarized reproduction reference light by the p-polarization irradiation means and the s-polarization irradiation means. Separating means;
P-polarization imaging means and s-polarization imaging means for imaging the page data information relating to the separated p-polarized reproduction light and s-polarization reproduction light, respectively, and converting them into electrical information signals;
A holographic recording medium multiplex recording / reproducing apparatus comprising: Reference light for reproduction is applied to a hologram recording medium in which a plurality of interference fringes formed by interfering signal light carrying information related to page data and reference light for recording are overlapped at the same position and subjected to angle multiplexing recording. In a hologram recording medium multiplex recording / reproducing apparatus for reproducing the page data information by making it incident at a predetermined angle,
First reference light polarization adjusting means for adjusting and outputting the reproduction reference light to first reference light that is either p-polarized light or s-polarized light;
First wavefront control means for controlling the wavefront of the first reference light from the first reference light polarization adjusting means so as to reduce hologram distortion;
First deflection angle adjustment means for adjusting an emission angle of the first reference light from the first wavefront control means so as to be incident on the hologram recording medium at a predetermined angle;
Of the first reference light output from the first deflection angle adjusting means and incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is converted into the first reference light among p-polarized light and s-polarized light. Second reference light polarization adjusting means for adjusting and outputting the second reference light having a different polarization from
Second wavefront control means for controlling the wavefront of the second reference light from the second reference light polarization adjusting means so as to reduce the distortion of the wavefront of the reference light and the distortion of the hologram due to transmission through the hologram recording medium; ,
Second deflection angle adjusting means for adjusting an exit angle so that the second reference light from the second wavefront control means is incident on the hologram recording medium at an angle different from the predetermined angle;
Reproduction light separating means for separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
Two image pickup means for picking up images of hologram information carried on the two separated reproduction lights;
A holographic recording medium multiplex recording / reproducing apparatus comprising:   Signal light is emitted when page data is recorded, while a modulation element that modulates light based on page data is recorded at a predetermined position where reproduction light is incident when page data is reproduced. At the time of data reproduction, an element replacement mechanism is provided that switches an image pickup element that picks up page data information carried by either p-polarized light or s-polarized light of the reproduced light to be installed. The holographic recording medium multiplex recording / reproducing apparatus according to claim 1, wherein: For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
Separating the reference light for reproduction into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other;
Controlling the wavefront of each reproduction reference light so that the distortion of the hologram is reduced in the optical path of each of the separated p-polarized light and s-polarized reproduction reference light;
Irradiating p-polarized light and s-polarized light of the reproduction reference light at the same position on the hologram recording medium with different incident angles,
Separating the p-polarized reproduction light and the s-polarized reproduction light output from the hologram recording medium according to the irradiation of the p-polarized light and the s-polarized light by the p-polarized light irradiation means and the s-polarized light irradiation means,
The page data information related to the separated p-polarized reproduction light and s-polarized reproduction light is imaged and converted into an electrical information signal,
After that, the process of reproducing the page data information of the next step is repeatedly performed by adjusting to the reference light incident angle state where the page data information of the next step recorded by angle multiplexing can be reproduced,
A holographic recording medium multiplex recording / reproducing method. For a hologram recording medium in which interference fringes formed by interfering signal light carrying information related to page data and recording reference light are multiplexed and superimposed at the same position using an angle multiplex recording technique. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by causing the reproduction reference light to enter at a predetermined angle,
In the optical path of the reproduction reference light, control the wavefront of the reproduction reference light so as to reduce the distortion of the hologram,
The reproduction reference light wavefront controlled by the wavefront control means is separated into p-polarized light and s-polarized light, which are linearly polarized light whose polarization planes are orthogonal to each other,
Irradiating p-polarized light and s-polarized light of the reproduction reference light at the same position on the hologram recording medium with different incident angles,
Using the multiple recording / reproducing method, the page data information that has been recorded in multiple recordings is sequentially reproduced by two pages,
Separating the p-polarized reproduction light and the s-polarized reproduction light output from the hologram recording medium in accordance with the irradiation of the p-polarized light and the s-polarized reproduction reference light by the p-polarized light irradiation means and the s-polarized light irradiation means,
The page data information related to the separated p-polarized reproduction light and s-polarized reproduction light is imaged and converted into an electrical information signal,
After that, the process of reproducing the page data information of the next step is repeatedly performed by adjusting to the reference light incident angle state where the page data information of the next step recorded by angle multiplexing can be reproduced,
A holographic recording medium multiplex recording / reproducing method. Reference light for reproduction is applied to a hologram recording medium in which a plurality of interference fringes formed by interfering signal light carrying information related to page data and reference light for recording are overlapped at the same position and subjected to angle multiplexing recording. In the hologram recording medium multiplex recording / reproducing method for reproducing the page data information by making it incident at a predetermined angle,
Adjusting the reproduction reference light to a first reference light that is either p-polarized light or s-polarized light, and outputting the first reference light;
Controlling the wavefront of the first reference beam so as to reduce the distortion of the hologram;
For the first reference light, the incident angle is adjusted so as to enter the hologram at a predetermined angle,
Of the first reference light incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is adjusted to the second reference light that is different from the first reference light in p-polarized light and s-polarized light. Output
Controlling the wavefront of the second reference light so as to reduce the distortion of the wavefront of the reference light and the distortion of the hologram due to the transmission of the hologram recording medium,
Adjusting the incident angle so that the second reference light is incident on the hologram recording medium at an angle different from the predetermined angle,
Separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
2. A hologram recording medium multiplex recording / reproducing method, wherein the hologram information carried by the two separated reproducing lights is imaged by two imaging means, respectively.