JP6349611B2 - Hologram recording / reproducing device - Google Patents

Description

  The present invention relates to a hologram recording / reproducing apparatus capable of processing unnecessary light generated by transmitting through a hologram recording medium when performing information recording or information reproducing processing using a hologram.

  In recent years, a hologram memory has attracted attention as a high-capacity and high-speed information recording / reproducing system. The hologram memory causes two coherent lights called reference light and signal light to interfere with each other, and records and holds the generated interference fringes on the recording medium as a change in refractive index. The signal light is spatially modulated by a two-dimensional data image called “page data”, and is irradiated onto a recording medium through a lens.

  In order to further increase the density and capacity of such a holographic memory, it is possible to change the reference light conditions (for example, the incident angle, wavelength, or wavefront of the recording medium) to the same location on the medium. Various multiplex recording techniques for multiplexing and recording a plurality of page data have been developed. Various methods of multiplex recording have been proposed so far. A typical example is an angle multiplexing system that performs multiple recording while changing the incident angle (see, for example, Patent Document 1 below).

  In the angle multiplexing method, the reference light is changed by changing the angle of the reference light by a galvanometer mirror or by rotating the recording medium around an axis perpendicular to a plane including the reference light axis and the signal light axis. A plurality of page data are recorded in the form of holograms while gradually changing the approach angle to the recording medium. Further, at the time of reproduction, by irradiating the recording medium with reference light under the same conditions as when recording, the light is diffracted by the hologram inside the recording medium, and reproduction light is obtained. The original information can be read out by photographing and decoding this with a camera or the like.

  FIG. 3 is a diagram showing a main optical system of a hologram recording / reproducing apparatus using a typical angle multiplexing method as found in Patent Document 1, for example. With reference to FIG. 3, an outline of hologram recording / reproduction by the angle multiplexing method will be described. In addition, the code | symbol attached | subjected to each member of the apparatus shown in FIG. 3 shall add 200 to the code | symbol attached | subjected to each member of the apparatus of FIG.

As shown in FIG. 3, page data is displayed on an SLM (Spatial Light Modulator) 223, and signal carrier light is spatially modulated and output as signal light. The signal light is collected by an FTL (Fourier transform lens) 210, and unnecessary high frequency components are removed by the aperture stop 212, and then irradiated to the recording medium 211 by the relay lens 220. At the same time, by irradiating the reference light superimposed on the signal light irradiation position of the recording medium 211, a light interference fringe is generated, and a change in the refractive index according to the intensity of the light of the interference fringe pattern is induced in the recording material. This is held as a hologram. As a medium material, a photoreactive organic material (photopolymer) or the like is often used.

  The reflection angle of the recording reference light toward the recording medium 211 is sequentially changed by the galvanometer mirror 219, and the incident angle when the recording medium 211 is irradiated through the relay lens 220 is sequentially changed. As described above, the angle-multiplexed hologram recording is completed by sequentially overwriting different page data in one place of the recording medium while sequentially changing the reference light incident angle.

  On the other hand, at the time of reproduction, only the reference light is irradiated to the information recording position of the recording medium 211 from the back side. At this time, light is diffracted by the hologram in the medium to generate reproduction light. Thereafter, the reproduction page data photographed by the image sensor (camera) 221 is subjected to signal processing such as interpolation processing, region extraction processing, or filtering, and then the original data can be restored by demodulation and error correction.

  The reference light irradiation method at the time of reproduction is a technique called phase conjugate reproduction in which the reference light at the time of reproduction is irradiated from the direction that is phase conjugate with the reference light at the time of recording (for example, Patent Document 2 below) reference). In this phase conjugate reproduction method, the reproduction light optical system (relay lens 224, aperture stop 212, FTL 210, and PBS 209) at the time of reproduction can also be used as the signal light irradiation optical system at the time of recording, so that the optical system can be simplified. Furthermore, since the optical system aberration (distortion) superimposed on the signal light can be canceled at the time of information reproduction, there is an advantage that a high-quality reproduction signal can be obtained.

  Further, phase conjugate reproduction is performed by irradiating the hologram of the recording medium 211 with reference light during reproduction from the galvanometer mirror 232 via the relay lens 233. In this case, the reproduction light reaches the image sensor (camera) 221 from the recording medium via the relay lens 224, the aperture stop 212, the FTL 210, and the PBS 209.

  By the way, after the reference light is applied to the recording medium, most of the light is transmitted through the recording medium as light that does not contribute to recording or reproduction (hereinafter referred to as “unnecessary transmitted light”). If this unnecessary transmitted light is left as it is, it may be reflected by a mirror or the like arranged in the optical system and irradiated to an unexpected part, which may cause various disadvantages described later.

  For such inconvenience caused by unnecessary transmitted light, a solution technique disclosed in Patent Document 3 below is known.

JP 2006-154163 A JP 2010-129110 A JP 2005-275061 A

However, according to the conventional method described in Patent Document 3 described above, there is a possibility that various disadvantages as described below may occur.
That is, at the time of information recording, unless the light absorption rate of the light absorber disposed close to the recording medium is extremely high, unnecessary transmitted light is irradiated to the information unrecorded portion of the recording medium, and the polymerization reaction of the photopolymer is caused. The recording material will not be able to demonstrate its original recording performance, or unnecessary transmission light will be irradiated to the part of the recording medium where information is being recorded, resulting in double reference light recording, and the signal quality of the recorded page data will deteriorate. There is a risk.

  Further, when information is recorded, if unnecessary transmitted light is scattered by the optical components in the signal light path, the scattered light is superimposed on the signal light, and the signal quality of the page data may be deteriorated.

  Further, at the time of information reproduction, unnecessary transmitted light is radiated to the portion of the recording medium where information is being reproduced, and two or more page data are reproduced at the same time, resulting in mutual crosstalk noise and deterioration in signal quality. is there.

  The present invention has been made in view of the above circumstances, and appropriately treats unnecessary transmitted light that does not contribute to information recording and information reproduction, and is likely to cause various inconveniences when unnecessary transmitted light is irradiated to an unexpected part. It is an object of the present invention to provide a hologram recording / reproducing apparatus that can be avoided.

The angle multiplexing hologram recording / reproducing apparatus of the present invention is
The light is emitted from the light source and separated into the signal carrier light and the reference light by the first polarization beam splitter. At the time of recording information, the signal carrier light carries desired information and serves as signal light at a predetermined position on the hologram recording medium. The information is recorded at the predetermined position by irradiating the separated reference light to the predetermined position, and when reproducing the information, only the reference light is irradiated to the predetermined position. The recorded information is read out, and the read information is picked up by the image pickup means so that the information is reproduced.
A positional relationship in which the recording reference light at the time of recording the information and the reproduction reference light at the time of reproducing the information are polarized and separated by the second polarization beam splitter and face each other with the hologram recording medium interposed therebetween In the hologram recording / reproducing apparatus in which the hologram recording medium is irradiated with the phase conjugate type,
During recording of the information, out of the recording reference light irradiated onto the hologram recording medium by the recording reference light deflection angle variable mirror, the recording reference light is transmitted through the hologram recording medium, and the reproduction reference light deflection angle variable mirror is transmitted. A light absorbing portion that absorbs the recording reference light transmitted light reflected by the light source, and the recording reference light transmitted light is incident on the light absorbing portion regardless of a change in the incident angle of the reference light to the hologram recording medium. Recording light absorbing means comprising recording reference light deflection angle control means for controlling the reference light deflection angle by the reproduction reference light deflection angle variable mirror so as to be incident,
During reproduction of the information, out of the reproduction reference light irradiated to the hologram recording medium by the reproduction reference light deflection angle variable mirror, the reproduction reference light is transmitted through the hologram recording medium and is recorded. Regardless of the change in the incident angle of the reference light on the hologram recording medium, the light absorbing portion that absorbs the reference light transmitted for reproduction reflected by the variable deflection angle mirror, A reproduction light absorbing means comprising: a reproduction reference light deflection angle control means for controlling a reference light deflection angle by the recording reference light deflection angle variable mirror so as to enter the absorption section;
Among these, at least one light absorbing means is provided.

Further, at the time of recording the information, sequentially changing the reflection angle of the recording reference light irradiated to the hologram recording medium, while sequentially changing the incident angle of the recording reference light to the hologram recording medium, A recording reference beam deflection angle variable mirror that irradiates the recording reference beam on the irradiated portion of the hologram recording medium; and
During reproduction of the information, the reflection angle of the reproduction reference light applied to the hologram recording medium is sequentially changed, and the reproduction reference light is sequentially changed while changing the incident angle of the reproduction reference light to the hologram recording medium. It is preferable to provide a reproducing reference beam deflection angle variable mirror that irradiates the reference beam on the irradiated portion of the hologram recording medium.

In addition, both the recording light absorption means and the reproduction light absorption means,
At the time of recording the information, the recording reference light transmitted light is reflected by the reproduction reference light deflection angle variable mirror, and travels backward in the optical path of the reference light at the time of reproducing the information. The polarizing beam splitter is reflected / transmitted, and irradiated to the light absorbing portion disposed in the vicinity of the second polarizing beam splitter,
At the time of reproducing the information, the reproduction reference light transmitted light is reflected by the recording reference light deflection angle variable mirror, and reversely travels the optical path of the reference light at the time of recording the information. It is preferable that the light absorbing unit disposed in the vicinity of the second polarizing beam splitter is irradiated / reflected through the polarizing beam splitter.

  Here, “reverses the optical path of the reference light at the time of information reproduction and reflects / transmits the second polarization beam splitter,... Reverses the optical path of the reference light at the time of information recording, and “Transmitted / reflected through second polarizing beam splitter” means “reflecting the optical path of reference light during information reproduction and reflected by the second polarizing beam splitter, and so on when recording information”. Reverse the optical path of the light and pass through the second polarizing beam splitter "or" Reverse the optical path of the reference light during information reproduction and pass through the second polarizing beam splitter " ,..., Reversely traveling in the optical path of the reference light during information recording, and reflected by the second polarizing beam splitter.

In addition, both the recording light absorption means and the reproduction light absorption means,
The light absorbing unit is composed of a recording light absorbing unit disposed in the vicinity of the reproducing reference light deflection angle variable mirror and a reproducing light absorbing unit disposed in the vicinity of the recording reference light deflection angle variable mirror. It is preferable.

In addition, it is preferable to include an optical waveguide or a plurality of reflection mirrors for guiding the recording reference light transmitted light and / or the reproduction reference light transmitted light to the light absorbing portion.
Here, “the recording reference light transmission light and / or the reproduction reference light transmission light” means “
It means “the recording reference light transmitted light and the reproduction reference light transmitted light” or “the recording reference light transmitted light or the reproduction reference light transmitted light”.
Furthermore, it is preferable that the light absorbing portion is made of a beam pocket or a light absorbing material.

According to the hologram recording / reproducing apparatus of the present invention, unnecessary transmitted light is taken in and absorbed inside by a light absorbing portion provided at a predetermined position.
Thereby, at the time of information recording, it is possible to reduce the possibility that unnecessary transmitted light is irradiated to the information non-recorded area of the recording medium, thereby preventing the polymerization reaction of the photopolymer from starting and recording. It is possible to avoid a situation in which the material cannot exhibit its original recording performance.

  Similarly, it is possible to reduce the possibility that unnecessary transmitted light is irradiated to the information recording area of the recording medium, and thus it is possible to avoid the possibility that the same area is irradiated with the reference light twice. The signal quality of the recorded page data can be maintained.

  Further, at the time of information reproduction, it is possible to reduce the possibility that unnecessary transmitted light is irradiated to the information reproducing area of the recording medium, thereby avoiding the possibility of two or more page data being reproduced simultaneously. Therefore, crosstalk noise can be reduced and signal quality can be maintained.

  Furthermore, when recording information, optical components in the signal optical path are irradiated with unnecessary transmitted light during recording, and the possibility of the scattered light being generated can be reduced, so that the scattered light is prevented from being superimposed on the signal light. Therefore, the signal quality of the page data can be maintained well.

It is a figure which shows the whole structure (an optical system is included) of the hologram recording / reproducing apparatus which concerns on Example 1 of this invention. It is a figure which shows the whole structure (an optical system is included) of the hologram recording / reproducing apparatus which concerns on Example 2 of this invention. It is a figure which shows the whole structure (an optical system is included) of the hologram memory recording / reproducing apparatus based on a prior art.

  Embodiments of the hologram recording / reproducing apparatus according to the present invention will be described in detail below with reference to the drawings.

<Example 1>
An angle multiplexing hologram apparatus 100 shown in FIG. 1 constitutes a hologram recording / reproducing apparatus according to Embodiment 1 of the present invention, and a hologram optical system 500 for recording / reproducing holograms on a recording medium (hologram recording medium) 11. And an image sensor 21 made of a CCD, a CMOS, or the like that images the reproduced information. As the recording medium 11, for example, a recording medium made of a photopolymer material having a thickness of about 1 mm sandwiched between two glass plates can be used.

  Laser light emitted from the laser light source 1 (for example, wavelength λ = 532 nm) is output through the shutter 2, the beam diameter is expanded by the spatial filter 3, and the polarization direction (vibration plane direction) of the half-wave plate 5. ) Can be changed arbitrarily. That is, the ratio of the P-polarized component and the S-polarized component can be arbitrarily changed. The laser light outputted from the half-wave plate 5 is a PBS (first beam splitter in the claims) 6 where the P-polarized component travels straight to become signal carrier light, and the S-polarized component is referenced with its traveling direction bent at a right angle. It is assumed to be light.

The ratio of signal carrier light and reference light separated by PBS 6 during recording is generally 1: 1.
It should be in the range of ~ 1: 3. This ratio is determined based on the configuration of the optical system (particularly, the spot size of the signal light on the recording medium), the beam profile, the white / black ratio of the page data, and the like.

On the other hand, the ratio of the signal carrier light and the reference light separated by the PBS 6 at the time of reproduction is 0: 1 because the recording medium 11 is irradiated with only the reference light.
The reference light whose optical path is bent at a right angle by the PBS 6 is brought into a polarization state of either the S-polarization state or the P-polarization state by selectively inserting / removing the half-wave plate 14 from the optical path.

  In the angle multiplexing hologram apparatus 100 shown in FIG. 1, the half-wave plate 14 is removed from the optical path during recording and the reference light remains in the S-polarized state, and the half-wave plate 14 is inserted into the optical path during reproduction. Thus, the reference light is converted into a P-polarized state (same in the angle multiplexing hologram apparatus 200 shown in FIG. 2). Hereinafter, a case where the reference light at the time of recording is set to the S polarization state and the reference light at the time of reproduction is set to the P polarization state will be described. However, on the condition that the recording medium 11 is irradiated with the signal light from the side opposite to that shown in FIG. 1, the reference light during recording is in the P-polarized state, and the reference light during reproduction is the S-polarized light. Even if the state is set, the same effect can be obtained.

  Thereafter, after the reference light passes through the aperture stop 16, it is transmitted by the PBS (second beam splitter) 17 in the case of the reference light during reproduction (P-polarized light) and the reference light during recording (S-polarized light). The case is reflected at a right angle.

On the other hand, the signal carrier light traveling straight through the PBS 6 has its beam diameter enlarged by the two lenses 7 and 8 and enters the PBS 9 via the shutter 22. Since the signal carrier light is in the P-polarized state when it enters the PBS 9, it passes through the PBS 9 and enters the SLM 23. The SLM 23 is configured to sequentially display desired page data information, and the signal carrier light incident on the SLM 23 carries information and is output as signal light. The signal light output from the SLM 23 is reflected in the direction of the recording medium 11 by the PBS 9 because the vibration plane is shifted by a half wavelength and is in the S polarization state. Thereafter, the signal light is irradiated onto a predetermined area of the recording medium 11 through an FTL (Fourier transform lens) 10, an aperture stop 12 and a relay lens 24.
The recording reference light reflected by the PBS 17 at a right angle is applied to a galvanometer mirror (recording reference light deflection angle variable mirror in claims) 19 via a mirror 18. On the other hand, the reproduction reference light transmitted through the PBS 17 is applied to a galvanometer mirror (reproduction reference light deflection angle variable mirror in claims) 32 via a mirror 31.

  The galvanometer mirror 19 is controlled so as to change the mirror rotation angle by a predetermined amount every time page data is recorded (by a control signal from the control device 41). The incident angle of the recording reference light is changed every time the page data is recorded, and angle multiplex recording is performed by interference with each signal light incident on the same area of the recording medium 11 from different angles. Can be done. A relay lens 20 is inserted between the galvanometer mirror 19 and the recording medium 11.

  On the other hand, the galvanometer mirror 32 is controlled to change the mirror rotation angle by a predetermined amount every time the page data is reproduced (by a control signal from the control device 41). The incident angle of the reproduction reference light to the area is changed every time the page data is reproduced. A relay lens 33 is inserted between the galvanometer mirror 32 and the recording medium 11.

  Incidentally, during recording, the recording reference light transmitted through the recording medium 11 is unnecessary transmitted light that has not contributed to the recording process. The unnecessary transmitted light at the time of recording reaches the galvanometer mirror 32, which is a reproduction reference light deflection angle variable mirror, via the relay lens 33.

  In the prior art, during recording, the galvanometer mirror 32, which is a reference light deflection angle variable mirror for reproduction, is not normally operated. Therefore, the emitted light from the recording medium 11 that changes every moment in angle multiplex recording can be obtained. When incident on the galvanometer mirror 32 at various angles, the reference light transmitted light at the time of recording is reflected in various directions by the galvanometer mirror 32, and the reference light transmitted at the time of recording reflected by each member of the optical system is further reflected. This causes various problems as follows.

For example, at the time of information recording, a reference light transmitted light at the time of recording is irradiated to an unrecorded portion of the recording medium, a photopolymer polymerization reaction is started, and the recording material cannot exhibit its original recording performance, Unnecessary recording transmitted light is irradiated to a portion where information is being recorded, so that double reference light recording is performed, and the signal quality of the recorded page data deteriorates.
Further, when information is recorded, when the recording reference light transmitted light is irradiated onto the optical component in the signal optical path to generate scattered light, the scattered light is superimposed on the signal light, and the signal quality of the page data is deteriorated.

  Therefore, in the present embodiment, by adjusting the rotation angle of the reproducing galvanometer mirror 32 during recording, it is related to the size of the emission angle of the reference light transmitted light during recording from the recording medium 11 that changes every moment. Instead, the deflection angle of the reference light transmitted light during recording in the galvanometer mirror 32 is controlled so that it can be reflected in a certain direction (the direction of the mirror 31). As described above, the deflection angle of the recording reference light transmitted light in the galvanometer mirror 32 is controlled by inputting a predetermined drive instruction signal from the control device 41 to the drive unit of the rotary motor of the galvanometer mirror 19.

The control device 41 not only performs the deflection angle control of the reference light transmitted light during recording (and the reference light transmitted for reproduction) but also the galvanometer mirrors 19 and 32 related to normal angle multiplex recording operation and angle multiplex reproduction operation. It has various functions such as rotation drive control, laser light output adjustment from the laser light source 1, opening / closing operation of the shutters 2 and 22, and imaging timing adjustment of the image sensor 21, but here, reference light transmitted light during recording is used. The explanation is focused on the control performed on the deflection angle of (and the reproduction reference light transmitted light).

  Here, at the time of recording described above, the reference light transmitted during recording reflected by the galvanometer mirror 32 is reflected by the mirror 31 at a right angle and enters the PBS 17 from the side in FIG.

  When the recording reference light transmitted light is incident on the PBS 17, it is in the S-polarized state, so that the recording reference light transmitted light is reflected by the PBS 17 in the perpendicular direction. That is, since the reference light transmitted light at the time of recording is reflected above the PBS 17 in FIG. 1, the reference light transmitted light at the time of recording can be absorbed by arranging the light absorbing portion 25 at a position near the upper portion of the PBS 17. And it does not cause the above-mentioned problems due to disturbance light.

  In this embodiment, the reference light transmitted light at the time of reproduction is also absorbed at the time of reproduction by the same method as at the time of recording. That is, during reproduction, the reproduction reference light transmitted through the recording medium 11 is unnecessary reproduction reference light transmitted light that has not contributed to the reproduction process. The reference light transmitted light during reproduction reaches the galvanometer mirror 19 which is a recording reference light deflection angle variable mirror via the relay lens 20.

  In the prior art, the galvanometer mirror 19, which is a recording reference beam deflection angle variable mirror, is not normally operated at the time of reproduction. Therefore, the recording reference from the recording medium 11 that changes momentarily in angle multiplexing recording. When transmitted light enters the galvanometer mirror 19 at various angles, it is reflected in various directions by the galvanometer mirror 19 and further reflected by each member of the optical system, causing the following problems.

  That is, at the time of information reproduction, the reference transmission light at the time of reproduction is irradiated on the portion of the recording medium where information is being reproduced, and two or more page data are reproduced at the same time.

  Therefore, in this embodiment, at the time of reproduction, as in the case of the recording, the reference light transmission light at the time of reproduction from the recording medium 11 that changes every moment by adjusting the rotation angle of the galvanometer mirror 19 for recording. The deflection angle of the reference light transmitted light at the time of reproduction in the galvanometer mirror 19 is controlled so that it can be reflected in a fixed direction (direction of the mirror 18) regardless of the size of the emission angle.

  Here, at the time of reproduction described above, the reference light transmitted during reproduction reflected by the galvanometer mirror 19 is reflected at right angles by the mirror 18 and enters the PBS 17 from below in FIG.

  When the reference light transmitted light during reproduction enters the PBS 17, it is in the P-polarized state, so that the reference light transmitted light during reproduction passes through the PBS 17. That is, the reference light transmitted light at the time of reproduction is transmitted above the PBS 17 as shown in FIG. 1. Therefore, if the light absorbing portion 25 is arranged near the upper portion of the PBS 17, the reference light transmitted light at the time of recording is absorbed. And it does not cause the above-mentioned problems due to disturbance light.

As described above, according to the present embodiment, the reference light transmitted light can be absorbed by the single light absorbing portion 25 arranged in the vicinity of the upper portion of the PBS 17 during recording and during reproduction, thereby simplifying the optical system. And miniaturization can be promoted.
In addition, mirrors 4, 15, 18, and 31 are provided to bend the optical path as necessary.

<Example 2>
An angle multiplexing hologram apparatus 200 shown in FIG. 2 constitutes a hologram recording / reproducing apparatus according to Example 2 of the present invention, and is reproduced with a hologram optical system 600 that records and reproduces holograms on the recording medium 111. And an image sensor 121 made of a CCD, a CMOS or the like for imaging a hologram. In addition, the code | symbol attached | subjected to each member of the apparatus which concerns on Example 2 shown in FIG. 2 shall add and express 100 to the code | symbol attached | subjected to each corresponding member of the apparatus which concerns on Example 1 shown in FIG. The duplicate description will be omitted.

  In the apparatus 200, it may be difficult to secure a space for the light absorbing portion in the vicinity of the PBS 117 from the viewpoint of preventing the arrangement of the optical member and the interference of physical parts based on a request for downsizing the apparatus. In such a case, a light absorbing unit may be set outside the reference optical path as in this embodiment.

  In other words, during recording, the recording reference light transmitted light that has passed through the recording medium 111 passes through the relay lens 133 and reaches the galvanometer mirror 132. In order to irradiate the recording light absorbing unit 134 in FIG. 2 with a beam, if a deflection angle control of the galvanometer mirror 32 described in the first embodiment is given an offset amount of a predetermined angle, a recording medium for recording reference light transmitted light is recorded. 1, the reflected light of the galvanometer mirror 32 can be emitted in the direction of the recording light absorber 134 (in the direction of the mirror 31 in the first embodiment) regardless of the angle of the emitted light.

  Similarly, during reproduction, the reference light transmitted during reproduction that has passed through the recording medium 111 passes through the relay lens 120 and reaches the galvanometer mirror 119. In order to irradiate the reproduction light absorbing section 125 in FIG. 2 with the reproduction reference light transmitted light in FIG. 2, an offset amount of a predetermined angle is given to the deflection angle control of the galvanometer mirror 19 described in the first embodiment, and the recording reference is made Regardless of the angle of light emitted from the recording medium 111 of the light transmitted light, the reflected light of the galvanometer mirror 119 can be emitted in the direction of the reproducing light absorbing portion 125 (in the direction of the mirror 18 in the first embodiment).

<Light absorption part>
The light absorber according to the first embodiment and the second embodiment can be configured using various light absorbers. Of these, the most basic light absorber is a beam pocket. The beam pocket has a cone shape that becomes thinner as it goes in the light traveling direction, and the inside is tapered and shading screwed. Further, a black alumite treatment or the like that can absorb light whenever incident light is reflected by the inner wall portion is applied to the inner wall surface. The thus configured beam pocket absorbs the reference light transmitted light incident on the inside from the bottom surface side thereof while being shielded and reflected.

  As a smaller light absorber, a black paint made of an organic material or the like having a high absorbance in the use wavelength range of laser light can be selected and applied to a base material. Furthermore, as a light absorber having a small thickness, a light absorbing material using carbon nanotubes developed recently (for example, Japanese Patent No. 5119407) can be used.

<Modification>
The hologram recording / reproducing apparatus of the present invention is not limited to that of the above-described embodiment (Examples 1 and 2), and can be changed to various other aspects. For example, in the above embodiment, the invention is applied to a hologram recording / reproducing apparatus related to angle multiplexing. However, the hologram recording / reproducing apparatus of the present invention is not limited to this, and a multiplexing method other than angle multiplexing is used. The present invention can also be applied to a hologram recording / reproducing apparatus and a non-multiplexed hologram recording / reproducing apparatus.

In addition, when the light absorption part must be disposed at a position apart from the vicinity of the PBS or the galvanometer mirror, an optical waveguide including an optical fiber or a plurality of reflection mirrors may be used. You may make it light-guide from a galvanometer mirror to a light absorption part.
In the above embodiment, both the recording light absorbing means and the reproducing light absorbing means are provided so as to absorb the reference light transmitted light both during recording and during reproduction. Only the means may be provided to absorb the reference light transmitted light only during recording or reproduction.

Further, instead of the galvanometer mirror, other optical scanning means such as a polygon mirror may be used.
Further, depending on the amount of the reference light transmitted light to the light absorption part and the irradiation time, the light absorption part may be heated, so that a cooling fin or fan (air disturbance is not induced in the light absorption part. It is also important to do so.

1, 101, 201 Laser light source 2, 22, 102, 122, 202, 222 Shutter 3, 103, 203 Spatial filter 4, 15, 18, 31, 104, 115, 118, 131,
204, 215, 218, 231 Mirror 5, 14, 105, 114, 205, 214 Half-wave plate 6, 9, 17, 106, 109, 117,
206, 209, 217 Polarizing beam splitter (PBS)
7, 8, 10, 107, 108, 110, 207, 208, 210 Lens (including FTL)
11, 111, 211 Hologram recording medium 12, 16, 112, 116, 212, 216 Aperture stop 19, 32, 119, 132, 219, 232 Galvanometer mirror 20, 24, 33, 120, 124, 133,
220, 224, 233 Relay lens 21, 121, 221 Image sensor 23, 123, 223 SLM (spatial modulator)
25, 125, 134 Light absorber 41, 141 Control device 100, 200, 300 Angle multiplexing hologram device 500, 600, 700 Hologram optical system

Claims (6)

The light is emitted from the light source and separated into the signal carrier light and the reference light by the first polarization beam splitter. At the time of recording information, the signal carrier light carries desired information and serves as signal light at a predetermined position on the hologram recording medium. The information is recorded at the predetermined position by irradiating the separated reference light to the predetermined position, and when reproducing the information, only the reference light is irradiated to the predetermined position. The recorded information is read out, and the read information is picked up by the image pickup means so that the information is reproduced.
A positional relationship in which the recording reference light at the time of recording the information and the reproduction reference light at the time of reproducing the information are polarized and separated by the second polarization beam splitter and face each other with the hologram recording medium interposed therebetween In the hologram recording / reproducing apparatus in which the hologram recording medium is irradiated with the phase conjugate type,
During recording of the information, out of the recording reference light irradiated onto the hologram recording medium by the recording reference light deflection angle variable mirror, the recording reference light is transmitted through the hologram recording medium, and the reproduction reference light deflection angle variable mirror is transmitted. A light absorbing portion that absorbs the recording reference light transmitted light reflected by the light source, and the recording reference light transmitted light is incident on the light absorbing portion regardless of a change in the incident angle of the reference light to the hologram recording medium. Recording light absorbing means comprising recording reference light deflection angle control means for controlling the reference light deflection angle by the reproduction reference light deflection angle variable mirror so as to be incident,
During reproduction of the information, out of the reproduction reference light irradiated to the hologram recording medium by the reproduction reference light deflection angle variable mirror, the reproduction reference light is transmitted through the hologram recording medium and is recorded. Regardless of the change in the incident angle of the reference light on the hologram recording medium, the light absorbing portion that absorbs the reference light transmitted for reproduction reflected by the variable deflection angle mirror, A reproduction light absorbing means comprising: a reproduction reference light deflection angle control means for controlling a reference light deflection angle by the recording reference light deflection angle variable mirror so as to enter the absorption section;
A hologram recording / reproducing apparatus comprising at least one light absorbing means. At the time of recording the information, the recording reference light irradiated on the hologram recording medium is sequentially changed in reflection angle, and the incident angle of the recording reference light on the hologram recording medium is sequentially changed. Recording reference light deflection angle variable mirror that irradiates the reference light for recording on the irradiated portion of the hologram recording medium,
During reproduction of the information, the reflection angle of the reproduction reference light applied to the hologram recording medium is sequentially changed, and the reproduction reference light is sequentially changed while changing the incident angle of the reproduction reference light to the hologram recording medium. 2. The hologram recording / reproducing apparatus according to claim 1, further comprising a reproducing reference beam deflection angle variable mirror for irradiating the reference beam on the irradiated portion of the hologram recording medium. Comprising both the recording light absorbing means and the reproducing light absorbing means,
At the time of recording the information, the recording reference light transmitted light is reflected by the reproduction reference light deflection angle variable mirror, and travels backward in the optical path of the reference light at the time of reproducing the information. The polarizing beam splitter is reflected / transmitted, and irradiated to the light absorbing portion disposed in the vicinity of the second polarizing beam splitter,
At the time of reproducing the information, the reproduction reference light transmitted light is reflected by the recording reference light deflection angle variable mirror, and reversely travels the optical path of the reference light at the time of recording the information. 3. The configuration according to claim 1, wherein the light absorbing unit is transmitted / reflected through the polarizing beam splitter and irradiated to the light absorbing unit disposed in the vicinity of the second polarizing beam splitter. Hologram recording / reproducing apparatus. Comprising both the recording light absorbing means and the reproducing light absorbing means,
The light absorbing unit is composed of a recording light absorbing unit disposed in the vicinity of the reproducing reference light deflection angle variable mirror and a reproducing light absorbing unit disposed in the vicinity of the recording reference light deflection angle variable mirror. The hologram recording / reproducing apparatus according to claim 1, wherein 5. The optical recording medium according to claim 1, further comprising: an optical waveguide or a plurality of reflection mirrors that guide the recording reference light transmitted light and / or the reproduction reference light transmitted light to the light absorbing unit. 2. A hologram recording / reproducing apparatus according to 1. The hologram recording / reproducing apparatus according to any one of claims 1 to 5, wherein the light absorbing portion is made of a beam pocket or a light absorbing material.