JP2008129073A - Hologram recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording and reproducing device that reduces moire patterns superposed on a reproduced image of page data and significantly improves the SN ratio of the reproduced image. <P>SOLUTION: Upon reproducing page data information, a reproduced image acquiring means 20 acquires a first reproduced image and a second reproduced image of any page data; and a reproduced image adding means 21 adds the two reproduced images to compensate moire patterns superposed on the reproduced images. The reproduced image acquiring means 20 is composed of a Fourier transformation lens 13 and a CCD 14. The two reproduced images have reversed moire patterns to each other on the images and are photographed by varying the incident angle of the incident laser beam to the CCD 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hologram recording / reproducing apparatus capable of high-density multiplex recording, and more particularly to an apparatus for recording / reproducing discrete digital data (for example, large-capacity archive data for storage) to / from a holographic memory.

In recent years, optical information recording media such as optical discs are becoming popular in information recording. In addition, research and development of next-generation optical information recording media aiming at higher speed and larger capacity is being actively conducted.
Among them, various multiplex recording / reproducing apparatuses using a hologram recording / reproducing method have been proposed from the viewpoint that the recording capacity can be significantly increased (for example, Patent Document 1 below).

  Hereinafter, a conventional hologram recording / reproducing apparatus will be described with reference to FIG.

The coherent laser beam emitted from the laser light source 301 is expanded in beam diameter by a beam expander including a diverging lens 302 and a collimator lens 303, and is split into two beams by a beam splitter including a polarization beam splitter 305, Each of them functions as signal light (object light: actually, it is made into signal light by the spatial light modulation element 309) and reference light.
The signal light branched by the polarization beam splitter 305 is applied to the spatial light modulator 309 via the polarization beam splitter 308.

  Digital information to be recorded is arranged in a two-dimensional array called page data, and is sequentially displayed on the spatial light modulation element 309, thereby spatially modulating light passing (reflecting). The polarization direction of the signal light emitted from the spatial light modulation element 309 is changed from that of the incident light, is reflected by the polarization beam splitter 308, optically Fourier transformed by the Fourier transform lens 311, and hologram recording medium 312. Is irradiated. At this time, if the reference light branched by the polarization beam splitter 305 is simultaneously irradiated from a different angle to the place where the signal light in the hologram recording medium 312 passes, interference fringes are generated in the volume inside the recording medium 312, and this fringe distribution is expressed. Hologram recording is performed by transferring to a recording area of the recording medium 312 in the form of a refractive index distribution or the like. Then, different page data is displayed on the spatial light modulator 309 and the incident angle of the reference light on the hologram recording medium 312 is changed little by little to multiplex-record different page data on the same area in the recording medium 312. It becomes possible to store information at high density.

  In the optical path, reflection mirrors 304 and 306 for deflecting the light beam and shutters 307 and 310 for appropriately passing / blocking the light beam are provided.

  On the other hand, when reproducing the page data recorded on the hologram recording medium 312, the same recording area is obtained by irradiating the recording medium 312 with the reference light at the same angle as the incident angle at the time of recording as described above. Even when a plurality of page data are recorded in a multiplexed manner, only desired page data can be selectively extracted and imaged by a CCD (imaging device) 314 via a Fourier transform lens (imaging lens) 312.

JP 2004-272268 A

  By the way, since laser light has extremely high coherence, moire interference fringes (hereinafter simply referred to as moire) are likely to occur due to interference caused by reflection on the surfaces of mirrors and lenses in the optical path. It is also known that interference occurs due to reflection inside the light receiving element, and moire is likely to occur. When such moire occurs, a reproduced image of the page data on which the moire pattern is superimposed is captured, and the reproduced image is extremely deteriorated.

  FIG. 2 shows a reproduced image captured when the entire screen is displayed in white, and a moire pattern is superimposed on the entire screen.

  FIG. 3 shows a reproduced image of page data on which a moire pattern is superimposed. Due to the superimposition of the moiré pattern, a phenomenon in which pixels that are originally white become black occurs, and the reproduced image is extremely deteriorated. Thus, the moire pattern reduces the SNR (Signal to Noise Ratio) of the reproduced page data. For this reason, in the hologram recording / reproducing technique, it is an important issue to reduce the moire pattern in order to achieve high density and large recording capacity of recorded information.

  Reflection of laser light can be reduced by coating AR coating (Anti Reflection Coating) on reflective mirrors and lenses placed in the optical path, as well as protective glass inside the image sensor. Thus, the generation of moire can be suppressed to some extent, but since the reflection of laser light cannot be completely prevented, some moire is generated.

  In addition, it is conceivable to insert ground glass just before the image pickup element to diffuse the laser light so that interference does not occur. However, the reproduced image is blurred due to the diffusion effect of the ground glass.

  Furthermore, it is conceivable to remove the moire component by performing signal processing on the captured reproduced image, but it is difficult in practice because the moire pattern includes various frequency components.

  The present invention has been made in view of the above circumstances, and provides a hologram recording / reproducing apparatus capable of reducing the moire pattern superimposed on the reproduced image of page data and greatly improving the SN ratio of the reproduced image. It is the purpose.

In order to solve the above problems, the hologram recording / reproducing apparatus of the present invention has the following features.
That is, the hologram recording / reproducing apparatus of the present invention causes the signal light carrying the data information and the reference light to interfere with each other and holographically records the interference fringes due to the interference light on the hologram recording medium as page data. In a hologram recording / reproducing apparatus for reproducing data information,
When the page data information is reproduced, a first reproduced image of arbitrary page data and a second reproduced image on which an inverted moire pattern that can cancel the moire pattern superimposed on the first reproduced image is superimposed. Reconstructed image acquiring means for acquiring, and reconstructed image adding means for adding the first reproduced image and the second reproduced image to cancel the moire pattern superimposed on these reproduced images, Is.

  Note that the reproduced image adding means includes a case where the same member as the reproduced image acquiring means or a part thereof is used.

  The reproduction image acquisition means includes an image sensor, and changes the incident angle of the reproduction light beam incident on the image sensor from the hologram recording medium when the first reproduction image and the second reproduction image are captured. Thus, the first reproduced image and the second reproduced image on which the moiré patterns that are reversed with each other are superimposed can be captured.

  The reproduction image acquisition means includes an imaging device, and when imaging the first reproduction image and the second reproduction image, an incident angle of a reproduction light beam incident on the imaging device from the hologram recording medium, and By changing the position of the image sensor with respect to the incident reproduction light beam, the first reproduction image and the second reproduction image on which the moiré patterns that are reversed with each other are superimposed can be captured.

  Further, the reproduced image acquisition means includes an imaging lens, a reflecting mirror, and an imaging element in order from the hologram recording medium side, and when imaging the first reproduced image and the second reproduced image, The first angle in which the moiré patterns that are inverted from each other are superimposed by changing the exit angle of the reproduction light beam incident on the reflection mirror from the hologram recording medium and the position of the image sensor with respect to the reproduction light beam incident on the image sensor. A reconstructed image and the second reconstructed image can be captured.

  Further, the reproduced image acquisition means includes an imaging lens, a plurality of reflecting mirrors, and an image sensor in order from the hologram recording medium side, and captures the first reproduced image and the second reproduced image. The first reproduction image and the second reproduction image in which the moiré patterns that are reversed to each other are superimposed are obtained by changing the emission angles of the reproduction light beams incident and emitted from the hologram recording medium to the plurality of reflection mirrors, respectively. Can be configured to.

  In each of the hologram recording / reproducing apparatuses described above, the reproduced image adding means optically adds the corresponding first reproduced image and the second reproduced image to each other, or the corresponding first reproduced image and the corresponding The second reconstructed image can be configured to be added after image processing.

  Further, the reproduced image acquisition means optically adds the corresponding first reproduced image and the second reproduced image to each other, and the first reproduced image and the second image within the frame period of the image sensor. It is possible to switch the imaging of the second reconstructed image so that the images are captured for the same time.

  In the hologram recording / reproducing apparatus of the present invention, when reproducing the page data information, the reproduced image acquisition means cancels the first reproduced image of arbitrary page data and the moire pattern superimposed on the first reproduced image. A second reproduced image on which the obtained inverted moire pattern is superimposed is acquired, and the first reproduced image and the second reproduced image are added by the reproduced image adding means to cancel the moire pattern superimposed on these reproduced images. Therefore, the moire pattern superimposed on the reproduced image of page data can be reduced, and the SN ratio of the reproduced image can be greatly improved. As a result, it is possible to achieve higher recording information density and higher recording capacity.

  Hereinafter, a hologram recording / reproducing apparatus according to an embodiment of the present invention will be described separately for an information recording function and an information reproducing function with reference to the drawings.

Example 1
FIG. 1 is a plan view (A) and a partial side view (B) showing a main optical system of a hologram recording / reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, some members for controlling the optical system are not shown.

<Information recording function>
As shown in FIGS. 1A and 1B, the coherent laser beam emitted from the laser light source 1 is expanded in beam diameter by a beam expander including a diverging lens 2 and a collimating lens 3, and is reflected by a reflection mirror 4. After being reflected, it is split into two light beams by a beam splitter comprising a polarizing beam splitter 5 and the like, and functions as signal light (object light: actually signal light by a spatial light modulator) and reference light, respectively. It is done.

The reference light (longitudinal linearly polarized light in the present embodiment: the same applies hereinafter) is reflected by the reflecting mirror 6 and irradiated onto a predetermined area on the hologram recording medium 12 via the shutter 7.
On the other hand, the signal light (horizontal linearly polarized light in the present embodiment: the same applies hereinafter) is applied to the spatial light modulator 9 via the polarization beam splitter 8.

  As the spatial light modulator 9, a light valve such as a liquid crystal display panel or DMD (Digital Micromirror Device) is used. Each pixel on the spatial light modulator 9 passes light (reflects in the example of FIG. 1) / blocks light according to binary digital information on the page data, thereby spatially modulating the light. Signal light carrying page data information is generated by this modulation processing.

  The polarization direction of the signal light emitted from the spatial light modulator 9 is changed from the incident state (horizontal linearly polarized light → vertical linearly polarized light), reflected by the polarizing beam splitter 8, and passed through the shutter 7. Optically Fourier-transformed by a post-Fourier transform lens (FTL: Fourier Transform Lens) 11 is applied to the hologram recording medium 12. At this time, since the reference light is simultaneously irradiated from another angle to the place where the signal light in the hologram recording medium 12 passes, interference fringes are generated in the volume inside the recording medium 12, and this fringe distribution is changed to the refractive index distribution. Hologram recording is performed by transferring to the recording area of the recording medium 12 in a form such as. Then, different page data is displayed on the spatial light modulation element 9 and the incident angle of the reference light on the hologram recording medium 12 is changed little by little to multiplex-record different page data on the same area in the recording medium 12. It becomes possible to store information at high density.

<Information playback function>
Further, at the time of information reproduction, the reference light that has passed through the shutter 7 is applied to a predetermined region of the hologram recording medium 12 at the same incident angle and position as at the time of information recording. The shutter 10 is in a closed state.

  In other words, when reproducing the desired page data, the diffracted light carrying the desired page data information is set by setting the same reference light incident conditions as when the information was recorded when the desired page data was recorded. Is output from the hologram recording medium 12, and the diffracted light is incident on the image pickup device including the CCD 14 via the Fourier transform lens 13 and is imaged.

  By the way, since the laser light has extremely high coherence, moire is likely to occur due to reflection of a mirror or a lens in the optical path and further due to reflection inside the image sensor. When such moire occurs, a reproduction image of page data on which the moire pattern is superimposed is picked up, and the reproduction image is extremely deteriorated. Therefore, in the present embodiment, when page data information is reproduced, a first reproduced image of arbitrary page data and an inverted moire pattern that can cancel out the moire pattern superimposed on the first reproduced image are superimposed. Reproduced image acquisition means 20 for acquiring the reproduced second reproduced image, and reproduced image addition means 21 for adding the first reproduced image and the second reproduced image by image processing to cancel the moire pattern superimposed on the reproduced image; It has. That is, when the page data information is reproduced, the reproduction image acquisition unit 20 acquires a first reproduction image and a second reproduction image of arbitrary page data, and the reproduction image addition unit 21 acquires these first reproduction images. And the second reproduced image are added to cancel the moire pattern superimposed on the reproduced image.

  The Fourier transform lens (imaging lens) 13 and the CCD 14 constitute a reproduced image acquisition means 20.

Further, when acquiring the above-described first reproduction image and second reproduction image, as shown in FIG. 1B, the incident angle (rotation angle) of the CCD 14 is changed with respect to the incident laser beam. as it will be (changed between a ₁ and a _2), also by imaging as its incident position as required (shift position) (changed between z ₁ and z ₂₎ change each The two reproduced images are acquired.

  The incident angle adjustment and the incident position adjustment of the laser beam to the CCD 14 are performed manually or automatically after the CCD 14 is placed on an adjustment table (not shown) that can adjust its rotational movement and parallel movement. This is done by adjusting the attitude of the CCD 14 on the adjustment table.

  Hereinafter, the adjustment will be described in more detail.

The rotation angle of the CCD 14 when the first reproduction image is obtained is a ₁ , the shift position is z ₁ , the rotation angle of the CCD 14 when the second reproduction image is obtained is a ₂ , and the shift position is z ₂ . .
Here, the “rotation angle” means that the axis perpendicular to the plane including the surface normal of the target incident surface and the incident light beam axis is the rotation axis, and the incident angle of the reproduction light beam is 0 degree as a reference. It is expressed by the rotation angle of the rotation shaft (the same applies to the following description). Further, the “shift position” means a position in the vertical direction in FIG. 1B within a plane including the surface normal of the target incident surface and the incident light beam axis, and the axis of the reproduction light beam. And the center axis of the CCD 14 (referred to in the following description).

First, at time t ₀ , the angle of the CCD 14 is set to a ₁ and the position is set to z ₁ .
Next, at time t ₁ , the shutter 7 is opened, and the hologram recording medium 12 on which page data has been recorded is irradiated with reference light. In this state, the CCD 14 captures the first reproduced image. The shutter 10 is kept closed.

Then, close the shutter 7 at time t _2, the setting angle of the CCD 14 a _2, the position to z _2.
Thereafter, at time t ₃ , the shutter 7 is opened and the hologram recording medium 12 is irradiated with the reference light again. In this state, the CCD 14 captures a second reproduced image.

  As described above, the first reproduced image and the second reproduced image are obtained by reversing the moire patterns on the reproduced image, so that the reproduced image adding means 21 thereafter reproduces the two captured images. By adding the images using image processing, a reproduced image of page data with reduced moire patterns can be obtained.

  Further, the addition of the reproduced image can be performed not only in image processing but also optically. When optically performed, the CCD 14 substantially functions as the reproduced image adding means 21, whereas when performed by image processing, an additional means (usually a computer) separate from the CCD 14 is used for the reproduced image. The function as the adding means 21 is assumed.

  After this, the page data is decoded using a conventionally known method.

Here, an example of the method for determining the angle and position of the CCD 14 in the first embodiment will be described in detail.
For example, the setting angle of the CCD 14 for obtaining the second reproduction image with respect to the first reproduction image picked up with the rotation angle of the CCD 14 set to 0 is obtained as follows. First, the rotational angle of the CCD 14 is changed variously to capture a temporarily reproduced image on which the moire pattern is superimposed. At this time, the shift position of the CCD 14 is determined so that the positions of the page data of the first reproduction image and the temporary reproduction image coincide.

Next, the moiré contrast C _m of the temporary addition image obtained by adding the first reproduction image and the temporary reproduction image is obtained as follows.
First, the moire contrast C _mhi for the i-th line in the horizontal direction of the screen is obtained. That is, when the luminance levels of one line in the horizontal direction are arranged in ascending order, the luminance level arranged at 95% of the total (0.95Nth value from the smallest when N is the number of elements in the arrangement) is I _max. If the luminance level (the 0.05N-th value from the smallest when the number of elements in the array is N) is I _min , the moiré contrast C _mhi is obtained by the following arithmetic expression. .

The calculation by the above equation is performed for all horizontal lines, and the average value thereof is set as the horizontal average moire contrast C _mh .
Similarly, the average moire contrast C _mv of the line in the vertical direction of the screen is obtained.

Thereafter, of the average moire contrast C _mh in the horizontal direction and the average moire contrast C _{mv in} the vertical direction, the larger value is set as the moire contrast C _m .

  When the moire pattern is offset, the moire contrast is reduced. Here, FIG. 11 shows the relationship between the rotation angle of the CCD 14 when capturing a provisional reproduction image and the moiré contrast of the provisional addition image obtained by adding the provisional reproduction image and the first reproduction image. When the angle is 6 mrad, the contrast is minimized, and the moire is reduced most at this time. Therefore, the temporarily reproduced image at this time is set as the second reproduced image.

  The angle and position of the CCD 14 (or the CCD and the reflection mirror) can be set in the same manner in Examples 2 and 3 described later.

  Hereinafter, the results obtained in this example will be described with reference to FIGS. Here, an example in which an addition operation is performed using image processing is shown.

  FIG. 2 shows a reproduced image captured when the entire screen is displayed in white as described above, and shows an example of the first reproduced image. It is clear that the moire pattern is superimposed on the entire screen. FIG. 3 also shows the first reproduced image of the page data on which the moire pattern is superimposed as described above. Due to the superimposition of the moiré pattern, a phenomenon in which pixels that are originally white become black occurs, and the reproduced image is extremely deteriorated.

On the other hand, FIG. 4 shows an example of a second reproduced image on which a moire pattern obtained by inverting the moire pattern of the first reproduced image shown in FIG. 2 is superimposed. The second reproduced image, as described above, from a state where the first reproduced image obtained, so as to change the incident angle of the laser beam (changes from a ₁ to a ₂₎ for the CCD 14, also optionally to to imaging to change the incident position (changed from z ₁ to z _2), in which acquired.

  FIG. 5 shows a reproduced image obtained by adding the first reproduced image shown in FIG. 2 and the second reproduced image shown in FIG. It is clear that the moire patterns that are inverted from each other are added, and the moire patterns are substantially cancelled.

  6 shows a second reproduction image of the page data on which the moire pattern shown in FIG. 4 is superimposed. FIG. 7 shows a first reproduction image of the page data on which the moire pattern shown in FIG. 3 is superimposed. The reproduction image obtained by adding the second reproduction image of the page data on which the moire pattern shown in FIG. 6 is superimposed by the reproduction image adding means 21 is shown. Moire patterns that are inverted from each other are added, and the moire patterns are substantially cancelled. In FIGS. 3 and 6, the phenomenon that the pixels that are originally white become black due to the superposition of the moire pattern occurs, and the reproduced image is extremely deteriorated. In, pixels that should originally be white are white and pixels that should be black are black, so that a desired reproduced image can be obtained. As a result, the SNR (SN ratio) of the reproduced image of the page data can be greatly improved.

<< Example 2 >>
FIG. 8 shows a plan view (A) and a partial side view (B) of the main optical system of the hologram recording / reproducing apparatus according to Embodiment 2 of the present invention. The hologram recording / reproducing apparatus according to the present embodiment is the same as that of the first embodiment in the basic configuration. Therefore, for the common members, 100 is added to the reference numerals in FIG. Detailed description is omitted for convenience of explanation.

The hologram recording / reproducing apparatus according to the second embodiment is different from that according to the first embodiment in that a reflection mirror 125 is provided between the Fourier transform lens (imaging lens) 113 and the CCD 114. That is, in the first embodiment, the incident angle adjustment of the laser beam to the CCD 14 is performed by rotating the CCD 14. In this embodiment, however, the reflection provided between the Fourier transform lens 113 and the CCD 114 is performed. The mirror 125 is rotationally moved (changed between a ₁ and a ₂ ) about an axis perpendicular to the plane including the surface normal of the mirror 125 and the incident light beam axis, so that the laser light beam enters the CCD 114. Adjust the angle. In the present embodiment, as in the first embodiment, the adjustment of the incident position of the laser beam to the CCD 114 is performed by moving the CCD 114 in parallel (changing between z ₁ and z ₂ ).

Hereinafter, the adjustment will be described in more detail.
The rotation angle of the reflection mirror 125 when the first reproduction image is obtained is a ₁ , the shift position of the CCD 114 is z ₁ , the rotation angle of the reflection mirror 125 when the second reproduction image is obtained is a ₂ , and the CCD 114. Let z _{2 be} the shift position.

First, at time t ₀ , the angle of the reflection mirror 125 is set to a ₁ and the position of the CCD 114 is set to z ₁ .
Next, at time t ₁ , the shutter 107 is opened, and reference light is irradiated onto the hologram recording medium 112 on which page data is recorded in advance. In this state, the CCD 114 captures the first reproduced image. Note that the shutter 110 is closed.

Then, close the shutter 107 at time t _2, the setting angle of the reflecting mirror 125 the position of a _2, CCD 114 to z _2.
Thereafter, at time t ₃ , the shutter 107 is opened and the hologram recording medium 112 is irradiated with the reference light again. In this state, the CCD 114 captures a second reproduced image.

  As described above, the first reproduced image and the second reproduced image are obtained by reversing the moire patterns on the reproduced image, so that the reproduced image adding means 121 thereafter reproduces the two captured images. By adding the images optically or using image processing, a reproduction image of page data with reduced moire patterns can be obtained.

  Thereafter, decoding of page data using a conventionally known method is the same as that of the first embodiment.

Example 3
FIG. 9 shows a plan view (A) and a partial side view (B) of the main optical system of the hologram recording / reproducing apparatus according to Embodiment 3 of the present invention. The hologram recording / reproducing apparatus according to the present embodiment is the same as that of the first embodiment in the basic configuration. Therefore, for the common members, 200 is added to the reference numerals in FIG. Detailed description is omitted for convenience of explanation.

The hologram recording / reproducing apparatus according to the third embodiment is different from that according to the first embodiment in that the first reflection mirror 225 and the second reflection mirror 226 are provided between the Fourier transform lens (imaging lens) 213 and the CCD 214. Is different. That is, in the first embodiment, the adjustment of the incident angle of the laser light beam to the CCD 14 is performed by rotating and translating the CCD 14. In this embodiment, the angle between the Fourier transform lens 213 and the CCD 214 is adjusted. The first reflection mirror 225 and the second reflection mirror 226 provided are rotated and moved with the axis perpendicular to the plane including the normal of the mirror surface and the incident light beam axis as the rotation axis (a ₁ , a _2, and b ₁ , respectively). by each change) allowed to between b _2, performs the incident angle adjustment and incident position adjustment of the laser beam to the CCD 214.

Hereinafter, the adjustment will be described in more detail.
Note that the rotation angle of the first reflection mirror 225 when the first reproduction image is obtained is a ₁ and the rotation angle of the second reflection mirror 226 is b _1, and the first reflection mirror 225 when the second reproduction image is obtained. Is a ₂ and the rotation angle of the second reflecting mirror 226 is b ₂ .

First, at time t ₀ , the rotation angle of the first reflection mirror 225 is set to a ₁ and the rotation angle of the second reflection mirror 226 is set to b ₁ .
Next, at time t ₁ , the shutter 207 is opened, and reference light is irradiated onto the hologram recording medium 212 on which page data is recorded in advance. In this state, the CCD 214 captures the first reproduced image. Note that the shutter 210 is closed.

Then, close the shutter 207 at time t _2, the rotation angle of the first reflecting mirror 225 a _2, the rotation angle of the second reflecting mirror 226 and b _2.
Thereafter, at time t ₃ , the shutter 207 is opened and the hologram recording medium 212 is irradiated with the reference light again. In this state, the CCD 214 captures a second reproduced image.

  As described above, the first reproduced image and the second reproduced image are obtained by reversing the moire patterns on the reproduced image, so that the reproduced image adding means 221 thereafter reproduces the two captured images. By adding the images optically or using image processing, a reproduction image of page data with reduced moire patterns can be obtained.

  Thereafter, decoding of page data using a conventionally known method is the same as that of the first embodiment.

  The hologram recording / reproducing apparatus of the present invention is not limited to the above-described embodiment, and other various modifications can be made. For example, in the above embodiment, during the acquisition of the first reproduction image and the second reproduction image, centering on the rotation axis perpendicular to the plane including the surface normal of the target incident surface and the incident light beam axis, The CCD 14 or the reflection mirrors 125, 225, and 226 are rotated, but the direction of rotation is not limited to this. For example, the CCD or the reflection is centered on an axis that is perpendicular to the rotation axis. By rotating the mirror, it is possible to cancel moiré in the same way. Similarly, the direction in which the CCDs 14 and 114 are translated is not limited to the direction of the above-described embodiment.

  Furthermore, an electro-optic element (EOM), an acousto-optic element (AOM), or the like can be used to change the angle of the reproduction light from the hologram recording medium.

  In the above embodiment, the reproduction image adding means 21 adds the first reproduction image and the second reproduction image by image processing to cancel the moire pattern superimposed on the reproduction image. When the image and the second reconstructed image are optically added (added), the reconstructed image adding means switches between capturing of both reconstructed images within each frame period of the image sensor, and captures the same time each other. By adding in this way, the moire pattern superimposed on the reproduced image is canceled.

Schematic (A) and partial side view (B) showing a main optical system of a hologram recording / reproducing apparatus according to Embodiment 1 of the present invention. The figure which shows an example of the 1st reproduction | regeneration image imaged in the state on which the moire pattern was superimposed when the whole screen was displayed in white. The figure which shows the 1st reproduction image of the page data on which the moire pattern shown in FIG. 2 was superimposed. The figure which shows an example of the 2nd reproduction image imaged in the state on which the moire pattern reverse to the moire pattern of FIG. 2 was superimposed when the whole screen was displayed in white. The figure which shows the reproduction image of the state which added the 1st reproduction image shown in FIG. 2, and the 2nd reproduction image shown in FIG. The figure which shows the 2nd reproduction image of the page data on which the moire pattern shown in FIG. 4 was superimposed. The figure which shows the reproduction image of the page data of the state which added the 1st reproduction image of the page data shown in FIG. 3, and the 2nd reproduction image of the page data shown in FIG. Schematic (A) and partial side view (B) showing a main optical system of a hologram recording / reproducing apparatus according to Embodiment 2 of the present invention. Schematic (A) and partial side view (B) showing a main optical system of a hologram recording / reproducing apparatus according to Embodiment 3 of the present invention. Schematic showing the main optical system of a hologram recording and reproducing apparatus according to the prior art The graph which shows the relationship between the rotation angle of CCD when picking up a reproduction image (temporary reproduction image), and the moire contrast of the addition image (temporary addition image) which added this reproduction image and another reproduction image (1st reproduction image).

Explanation of symbols

1, 101, 201, 301 Laser light source 2, 102, 202, 302 Diverging lens 3, 103, 203, 303 Collimating lens 4, 6, 104, 106, 125, 204, 206,
225, 226, 304, 306 Reflective mirror 5, 8, 105, 108, 205, 208, 305, 308 Polarizing beam splitter 7, 10, 107, 110, 207, 210, 307, 310 Shutter 9, 109, 209, 309 Spatial light modulators 11, 13, 111, 113, 211, 213, 311, 313 Lenses 12, 112, 212, 312 Hologram recording medium 14, 114, 214, 314 CCD
20, 120, 220 Reproduction image acquisition means 21, 121, 221 Reproduction image addition means

Claims (7)

In the hologram recording / reproducing apparatus for causing the signal light carrying the data information to interfere with the reference light and holographically recording the interference fringes due to the interference light on the hologram recording medium as page data, and reproducing the recorded page data information,
When the page data information is reproduced, a first reproduced image of arbitrary page data and a second reproduced image on which an inverted moire pattern that can cancel the moire pattern superimposed on the first reproduced image is superimposed. Reconstructed image acquiring means for acquiring, and reconstructed image adding means for adding the first reproduced image and the second reproduced image to cancel the moire pattern superimposed on these reproduced images, Hologram recording / reproducing device.   The reproduction image acquisition means includes an image sensor, and changes the incident angle of the reproduction light beam incident on the image sensor from the hologram recording medium when imaging the first reproduction image and the second reproduction image. 2. The hologram recording / reproducing apparatus according to claim 1, wherein the holographic recording / reproducing apparatus is configured to pick up the first reproduced image and the second reproduced image on which moiré patterns that are inverted to each other are superimposed.   The reproduction image acquisition means includes an image sensor, and when imaging the first reproduction image and the second reproduction image, the incident angle of the reproduction light beam incident on the image sensor from the hologram recording medium, and the incident 2. The apparatus according to claim 1, wherein the first reproduction image and the second reproduction image on which the moiré patterns that are reversed with each other are superimposed are picked up by changing the position of the image sensor with respect to the reproduction light beam to be reproduced. Hologram recording / reproducing apparatus.   The reproduction image acquisition means includes an imaging lens, a reflection mirror, and an imaging element in order from the hologram recording medium side, and the hologram recording is performed when the first reproduction image and the second reproduction image are picked up. The first reconstructed image in which the moiré patterns that are reversed with each other are superimposed by changing the exit angle of the reconstructed light beam incident on the reflection mirror from the medium and the position of the image sensor with respect to the reconstructed light beam incident on the image sensor The hologram recording / reproducing apparatus according to claim 1, wherein the second reproduced image is captured.   The reproduction image acquisition means includes an imaging lens, a plurality of reflection mirrors, and an imaging element in order from the hologram recording medium side, and when the first reproduction image and the second reproduction image are imaged, The first reproduction image and the second reproduction image on which the moiré patterns that are reversed with each other are superimposed are picked up by changing the emission angles of the reproduction light beams incident and emitted from the hologram recording medium to the plurality of reflection mirrors. 2. The hologram recording / reproducing apparatus according to claim 1, wherein the hologram recording / reproducing apparatus is configured as follows.   The reproduced image adding means optically adds the corresponding first reproduced image and the second reproduced image to each other, or adds the corresponding first reproduced image and second reproduced image after image processing. 6. The hologram recording / reproducing apparatus according to claim 1, wherein:   The reproduced image acquisition means optically adds the corresponding first reproduced image and second reproduced image to each other, and the first reproduced image and the second reproduced image within each frame period of the image sensor. 6. The hologram recording / reproducing apparatus according to claim 1, wherein the hologram recording / reproducing apparatus is configured to switch the imaging of the reproduced image and to image each other for the same time.

Images