JP2012243354A - Holographic memory reproducing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the necessity of pixel matching between a reproduced image and a photodetector when in page data having multi-valued phase information added to each pixel, to detect phase information added to each pixel, oversampling is executed to detect it by a photodetector having four pixels for each pixel of the page data.SOLUTION: A photographic memory includes oscillator light generation means for generating oscillator light overlapped with diffracted light from a hologram storage medium to interfere during reproduction, phase modulation means for adding a predetermined phase difference between the oscillator light and the diffracted light from the hologram recording medium, and photodetection means for detecting interference light where the oscillator light is overlapped with the diffracted light from the hologram recording medium. For example, 9 pixels of the photodetector are set in correspondence to the respective pixels of the data page.

Description

  The present invention relates to an apparatus and method for reproducing information from a recording medium using holography.

  Currently, the Blu-ray Disc (TM) standard using a blue-violet semiconductor laser has made it possible to commercialize an optical disc having a recording density of about 50 GB even for consumer use. In the future, it is desired to increase the capacity of an optical disk to the same level as an HDD (Hard Disc Drive) capacity of 100 GB to 1 TB.

  However, in order to realize such an ultra-high density with an optical disc, a high-density technology by a new method different from the high-density technology by shortening the wavelength and increasing the objective lens NA is necessary.

  While research on next-generation storage technology is underway, hologram recording technology that records digital information using holography is attracting attention.

  As a hologram recording technique, for example, there is JP-A-2004-272268 (Patent Document 1). This publication describes a so-called angle multiplex recording method in which multiplex recording is performed by displaying different page data on a spatial light modulator while changing the incident angle of the reference light to the optical recording medium. Furthermore, this publication describes a technique for shortening the interval between adjacent holograms by condensing signal light with a lens and arranging an opening (spatial filter) in the beam waist.

  As a means for increasing the capacity of the hologram recording technique, for example, a method of adding multilevel phase information to each pixel of signal light has been proposed (Non-Patent Document 1).

JP 2004-272268 A

H.Noichi, H.Horimai, P.B.Lim, K.Watanabe and M.Inoue, “Collinear phase-lock holography for memories of the next generation” IWHM 2008 Digests, 42-43 (2008).

  By the way, in the page data in which multi-level phase information is added to each pixel, in order to detect the phase information added to each pixel, a photodetector having four pixels is used for each pixel of the page data. When detecting by oversampling, there is a problem that a pixel match between the reproduced image and the photodetector is necessary.

  The above problem is solved by the invention described in the claims, for example.

  According to the present invention, even if the reproduced page data and the photodetector do not have a pixel match, the phase information added to each pixel of the page data to which the phase information is added can be detected and the information can be reproduced. A holographic memory device that enables value recording / reproduction can be realized.

Schematic showing the effect when 9 pixels of the camera correspond to each pixel of page data Schematic diagram showing an embodiment of an optical information recording / reproducing apparatus Schematic showing a recording state in an embodiment of a pickup in an optical information recording / reproducing apparatus Schematic showing the state at the time of reproduction in the embodiment of the pickup in the optical information recording / reproducing apparatus Schematic which shows the positional relationship of the pixel on a camera in Example, a diffracted light, and oscillator light Schematic showing the phase state of the oscillator light in the present invention Enlarged view of phase modulation means in the embodiment Configuration diagram of phase modulation means in the embodiment Schematic showing an embodiment of the operation flow of the optical information recording / reproducing apparatus Schematic diagram showing phase distribution of page data Schematic showing the problem when 4 pixels of the camera correspond to each pixel of page data Schematic showing the pattern of 4 pixels used for reproduction among 9 pixels of a camera Schematic showing the operation | movement flow of the read-out process in an Example. Schematic showing an example of the arrangement of pixels in four types of phase states of the camera

  Examples of the present invention will be described below.

  Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a block diagram showing a recording / reproducing apparatus of an optical information recording medium for recording and / or reproducing digital information using holography.

  The optical information recording / reproducing apparatus 10 includes a pickup 11, a phase conjugate optical system 12, a disk cure optical system 13, a disk rotation angle detection optical system 14, and a rotation motor 50, and the optical information recording medium 1 is a rotation motor 50. It is the structure which can be rotated by.

  The pickup 11 plays a role of emitting reference light and signal light to the optical information recording medium 1 and recording digital information on the recording medium using holography. At this time, the information signal to be recorded is sent by the controller 89 to the spatial light modulator in the pickup 11 via the signal generation circuit 86, and the signal light is modulated by the spatial light modulator.

  When reproducing the information recorded in the optical information recording medium 1, the phase conjugate light of the reference light emitted from the pickup 11 is generated by the phase conjugate optical system 12. Here, the phase conjugate light is a light wave that travels in the opposite direction while maintaining the same wavefront as the input light. Reproduction light reproduced by the phase conjugate light is detected by a photodetector described later in the pickup 11, and a signal is reproduced by the signal processing circuit 85.

  The irradiation time of the reference light and the signal light applied to the optical information recording medium 1 can be adjusted by controlling the opening / closing time of the shutter in the pickup 11 via the shutter control circuit 87 by the controller 89.

  The disk cure optical system 13 plays a role of generating a light beam used for pre-cure and post-cure of the optical information recording medium 1. Precure is a pre-process for irradiating a predetermined light beam in advance before irradiating the desired position with reference light and signal light when recording information at a desired position in the optical information recording medium 1. Post-cure is a post-process for irradiating a predetermined light beam after recording information at a desired position in the optical information recording medium 1 so that additional recording cannot be performed at the desired position.

  The disk rotation angle detection optical system 14 is used to detect the rotation angle of the optical information recording medium 1. When adjusting the optical information recording medium 1 to a predetermined rotation angle, a signal corresponding to the rotation angle is detected by the disk rotation angle detection optical system 14, and a disk rotation motor control circuit is detected by the controller 89 using the detected signal. The rotation angle of the optical information recording medium 1 can be controlled via 88.

  A predetermined light source driving current is supplied from the light source driving circuit 82 to the light sources in the pickup 11, the disk cure optical system 13, and the disk rotation angle detection optical system 14, and each light source emits a light beam with a predetermined light quantity. be able to.

  Further, the pickup 11 and the disk cure optical system 13 are provided with a mechanism capable of sliding the position in the radial direction of the optical information recording medium 1, and position control is performed via the access control circuit 81.

  By the way, the recording technique using the principle of angle multiplexing of holography tends to have a very small tolerance for the deviation of the reference beam angle.

  Therefore, a mechanism for detecting the deviation amount of the reference beam angle is provided in the pickup 11, a servo control signal is generated by the servo signal generation circuit 83, and the deviation amount is corrected via the servo control circuit 84. It is necessary to provide a servo mechanism for this purpose in the optical information recording / reproducing apparatus 10.

  The pickup 11, the disk cure optical system 13, and the disk rotation angle detection optical system 14 may be simplified by combining several optical system configurations or all optical system configurations.

  FIG. 3 is a schematic view of an embodiment of the optical pickup device 11 according to the present invention. FIG. 3 shows a state during recording.

  The light beam emitted from the light source 201 passes through the collimator lens 202 and enters the shutter 203. When the shutter 203 is open, after the light beam passes through the shutter 203, the light quantity ratio of P-polarized light and S-polarized light is adjusted to a desired ratio by the polarization direction conversion element 204 configured by, for example, a half-wave plate. After the polarization direction is controlled in such a manner, the light enters the polarization beam splitter 205.

  The light beam transmitted through the polarization beam splitter 205 is enlarged by the beam expander 230, and then enters the spatial light modulator 212 via the polarization direction conversion element 209 and the polarization beam splitter 211. For example, as shown in FIG. 10, the modulator 212 generates page data to which phase information is added for each pixel. Here, the phase distribution in the page data is, for example, a phase distribution that removes DC intensity (so-called hot spot) in the light intensity distribution on the Fourier plane of the optical information recording medium 1. By doing in this way, the phase mask which was conventionally used in order to reduce DC intensity can be deleted. As an example, the phase distribution is such that the average value of the phases added to each pixel is π. As another example, the phase distribution is such that the average value of the phases added to each pixel is 0.5π or 1.5π. As another example, in one page, the number of pixels randomized with respect to phase = 0 and the number of pixels randomized with respect to phase π are made equal.

  The phase light is added to each pixel by the spatial light modulator 212, and the signal light 206 that has become page data is reflected by the polarization beam splitter 211 and propagates through the relay lens 213 and the spatial filter 214. The spatial light modulator 212 is not limited to a spatial light modulator having only a phase modulation function. By providing the spatial light modulator 212 with an amplitude modulation function, it is possible to modulate the amplitude spatially. Thereafter, the signal light 206 is condensed on the optical information recording medium 1 by the objective lens 215.

  On the other hand, the light beam reflected from the polarization beam splitter 205 works as reference light 207, and is set to a predetermined polarization direction according to recording or reproduction by the polarization direction conversion element 216, and then passes through the mirror 217 and the mirror 218. , Enters the mirror 219. The angle of the mirror 219 can be adjusted by the actuator 220, and the light enters the optical information recording medium 1 after passing through the lens 221 and the lens 222.

  In this way, the signal light 206 and the reference light 207 are incident on the optical information recording medium 1 so as to overlap each other, whereby an interference fringe pattern is formed in the recording medium, and information is written by writing this pattern on the recording medium. Record. Further, since the incident angle of the reference light 207 incident on the optical information recording medium 1 can be changed by the mirror 219, recording by angle multiplexing is possible.

  FIG. 4 shows a state during reproduction in this embodiment. The reference light 207 enters the optical information recording medium 1 along the same optical path as that during recording. In this embodiment, a reproduction method using phase conjugate light is used, and information is reproduced using the reference light 207 that is reflected by the mirror 224 driven by the actuator 223 and incident on the optical information recording medium 1 again. The diffracted light 231 diffracted from the optical information recording medium 1 enters the camera 225 via the objective lens 215, the relay lens 213, the spatial filter 214, the polarization beam splitter 211, the optical element 250, and the optical element 251.

  Further, in order to generate the oscillator light 208 that causes the camera 225 to interfere with the diffracted light 231, the polarization direction is controlled by the polarization direction conversion element 204, and a desired amount of light is transmitted through the polarization beam splitter 205. The oscillator light 208 that has passed through the polarization beam splitter 205 passes through the beam expander 230, and then the polarization direction is controlled by the polarization direction conversion element 209, and is reflected from the polarization beam splitter 211. Thereafter, the oscillator light 208 is incident on the camera 225 via the optical element 250 and the optical element 251, and overlaps and interferes with the diffracted light 231 described above.

  Here, in order to detect the phase information added to each pixel of the page data, the optical element 250 and the optical element 251 are arranged in front of the camera 225 as shown in FIG. 7, for example, having a configuration as shown in FIG. Use elements.

  For example, the optical element 250 is an element partially composed of a quarter-wave plate and functions to advance the phase of light having polarization with respect to a predetermined optical axis by a quarter wavelength. In the figure of the optical element 250, the region other than the hatched portion is a region having no action of adding a phase. That is, the areas to which the phase is added and the areas to which the phase is not added are alternately arranged.

  The optical element 251 is an element configured by, for example, a first polarizer that transmits light having a specific polarization direction and a second polarizer that transmits light having a polarization direction different from the direction by 90 degrees. Such elements are arranged as shown in FIG. Here, the quarter-wave plate and the polarizer in the optical element 250 and the optical element 251 can be composed of, for example, a photonic crystal capable of controlling the polarization and transmission / reflection characteristics of incident light with a fine structure equal to or less than the wavelength. . Since the method for detecting the phase using the photonic crystal is described in JP-A-2008-286518, only the phase relationship between the diffracted light 231 and the oscillator light 208 in this embodiment will be described here.

  FIG. 5 is a schematic diagram showing the arrangement of pixels in the camera 225 and the positional relationship between the diffracted light 231 and the oscillator light 208. Note that FIG. 5 shows page data that has been subjected to amplitude modulation in addition to phase modulation, but may be white page data that is not subjected to amplitude modulation. Four phase differences (reference phase (for convenience, 0 ° in this embodiment), reference phase + 90 °, reference phase + 180 °, reference phase + 270 °) are added to diffracted light 231 and oscillator light 208 In this configuration, the light is incident on each of the four pixels that perform oversampling. Here, I1 and I2 used in the figure are obtained by subtracting the output value from the pixel on which the oscillator light 208 added with the reference phase + 180 ° is input from the output value from the pixel on which the oscillator light 208 added with the reference phase is incident. The value obtained by subtracting the output value from the pixel on which the oscillator light 208 added with the reference phase + 90 ° is subtracted from the output value from the pixel on which the oscillator light 208 added with the value I1 and the reference phase + 270 ° is incident is I2. For convenience, FIG. 5 depicts the positional relationship of the diffracted light 231 and the oscillator light 208 with respect to some pixels of the camera 225. Basically, in this embodiment, all combinations of four pixels used for oversampling are shown. On the other hand, it is assumed that the same positional relationship holds.

  Note that the phase states of the oscillator light 208 that is incident on at least four pixels used for oversampling are the above-described four phase states (for convenience, the four phase states are a, b, c, and d). The positional relationship as shown in FIG.

  With such a configuration, the phase difference between the diffracted light 231 incident on each pixel and the reference phase added to the oscillator light 208 using the principle of the fringe scanning method generally used in an interferometer or the like. Since Δφ can be calculated by (Equation 1) using I1 and I2 defined in FIG. 5, the phase information added to each pixel of the page data can be detected.

  In addition, when reproducing and compatibilizing page data subjected to amplitude modulation without performing phase multi-level recording, for example, by stopping the operation of the generation unit of the oscillator light 208 and stopping the generation of the oscillator light, the reproduction is performed. Device playback compatibility can be realized.

  FIG. 9 shows an operation flow of recording and reproduction in the optical information recording / reproducing apparatus 10. Here, a flow relating to recording / reproduction using holography in particular will be described.

  FIG. 9A shows an operation flow from when the optical information recording medium 1 is inserted into the optical information recording / reproducing apparatus 10 until preparation for recording or reproduction is completed, and FIG. FIG. 9C shows an operation flow until information is recorded on the information recording medium 1, and FIG. 9C shows an operation flow until the information recorded on the optical information recording medium 1 is reproduced from the ready state.

  When a medium is inserted as shown in FIG. 9A (401), the optical information recording / reproducing apparatus 10 discriminates whether or not the inserted medium is a medium for recording or reproducing digital information using holography, for example. (402).

  As a result of disc discrimination, when it is determined that the optical information recording medium records or reproduces digital information using holography, the optical information recording / reproducing apparatus 10 reads control data provided on the optical information recording medium (403). ), For example, information relating to the optical information recording medium and information relating to various setting conditions during recording and reproduction, for example.

  After reading out the control data, various adjustments according to the control data and learning processing (404) related to the pickup 11 are performed, and the optical information recording / reproducing apparatus 10 is ready for recording or reproduction (405).

  As shown in FIG. 9B, the operation flow from the ready state to recording information is as follows. First, data to be recorded is received (411), and information corresponding to the data is received from the spatial light modulator in the pickup 11. To send.

  Thereafter, various learning processes are performed in advance as necessary so that high-quality information can be recorded on the optical information recording medium (412), and the positions of the pickup 11 and the disk cure optical system 13 are optically determined by a seek operation (413). It is arranged at a predetermined position on the information recording medium.

  Thereafter, a predetermined area is pre-cured using a light beam emitted from the disk cure optical system 13 (414), and data is recorded using reference light and signal light emitted from the pickup 11 (415).

  After the data is recorded, the data is verified as necessary (416), and post-cure is performed using the light beam emitted from the disk Cure optical system 13 (417).

  As shown in FIG. 9C, the operation flow from the ready state to the reproduction of recorded information is performed in advance with various learning processes as necessary so that high-quality information can be reproduced from the optical information recording medium. (421). Thereafter, the positions of the pickup 11 and the phase conjugate optical system 12 are arranged at predetermined positions of the optical information recording medium by a seek operation (422).

  Thereafter, reference light is emitted from the pickup 11 and information recorded on the optical information recording medium is read (423). The present invention is applied in the operation of reading this information.

  Incidentally, FIG. 6 shows a configuration in which pixels of four photodetectors are arranged and oversampled for each pixel of page data, but the reproduced page data pixels are pixels in the photodetector pixels. Matching is required. FIG. 11 shows an example in which the pixel of the page data reproduced does not match the pixel of the photodetector. Since the pixels a, b, and c of the camera in FIG. 11 are on the boundary of the page data pixels, the phase information of each pixel of the page data is detected in a mixed state. For this reason, the problem that appropriate phase information cannot be acquired occurs.

  FIG. 1 shows a configuration of a camera for solving the above-described problem. FIG. 1A shows the relationship between page data pixels and photodetector pixels. For each pixel of the page data, 9 × 3 pixels of the camera are arranged. A thick line in FIG. 1 indicates a page data pixel. The arrangement of pixels for detecting the four types of phases in the camera is the same as in FIG. When the pixels are arranged in this way, as shown in FIGS. 1B to 1D, even if the positional relationship between the page data and the photodetector is shifted in the vertical direction and the horizontal direction, At least four of the nine pixels of the detector can be detected without being on the boundary of the page data pixels. Each of the four pixels surrounded by a dotted line in FIG. 1 indicates a pixel that is not on the page data boundary. For this reason, it is possible to detect appropriate phase information using four pixels surrounded by a dotted line. As described above, the number of pixels of the camera for detecting the phase information of one pixel of the page data requires 2 × 2 pixels for detecting the phase information. Since these pixels cannot be used for detecting phase information, at least 3 × 3 9 pixels are required.

  FIG. 12 shows four types of combination patterns of four pixels used for reproduction as patterns AD. A portion surrounded by a dotted line in FIG. 12 is a pixel used for resampling.

  FIG. 13 shows an operation flow of processing for reading information in this embodiment. First, information recorded on the optical information recording medium 1 is reproduced and received by a camera (1301). Next, resampling processing is performed according to the patterns A to D in FIG. 12 (1302 to 1305). Next, quality evaluation is performed using the results of re-sampling for patterns A to D (1306 to 1309). Next, based on the quality evaluation result, a pattern with good quality is determined from the four types of page data information (1310). Finally, page data is decoded using the determined pattern (1311). Here, as an index for quality evaluation, a histogram of phase information is created, and the fact that the histogram can be separated for each phase may be used as an index, SNR may be used as an index, and bER may be decoded and used as an index. good. When using a histogram or SNR, it is not necessary to decode data, so there is an advantage that processing can be performed at a higher speed than when using bER. When using bER, decoding is performed, and therefore there is a difference in quality. There is an advantage that it becomes clearer. In addition, any index can be used as long as it can determine whether the four types of page data are meaningful information.

  In addition, it is not necessary to perform the resampling process and the quality evaluation process for all the pixels of the page data, the adoption pattern is determined by performing the resampling and the quality evaluation for a part of the page data, and then adopted The entire page data may be resampled using a pattern. As a result, it is possible to reduce the time required to determine the adopted pattern as compared with the case where all pixels are processed. Further, it is not always necessary to perform resampling processing and quality evaluation processing on a plurality of patterns as shown in FIG. 13 for all page data. For example, if a pattern with good quality is determined for a certain page data, quality evaluation is performed on the other page data in the same book as the page data using the determined pattern. If it is greater than or equal to a predetermined threshold, playback is performed using the determined pattern. If the index of quality evaluation of the determined pattern falls below the predetermined threshold, such resampling is performed on the page data. Processing and quality evaluation processing may be performed. As a result, the time required for processing can be shortened.

  Further, the process as shown in FIG. 13 may be performed for each predetermined number of page data, or may be performed on the entire page data to be reproduced before the reproduction process. Further, the processing as shown in FIG. 13 may be performed, for example, at the time of setting up the playback apparatus, or may be performed after a playback instruction is given to the controller 89 or the like.

  Further, special data for pattern selection such as known data may be recorded in a part of the page data, and SNR and bER may be calculated. As a result, it is possible to select a pattern with higher accuracy than in the case where no known data is used.

  In FIG. 13, the resampling and quality evaluation are illustrated as operations for serially processing the patterns A to D, but the processing may be performed in parallel. When processing is performed in parallel, the processing speed increases, but the number of circuits increases. For this reason, considering the balance, for example, only the resampling part may be processed in parallel, and the quality evaluation part may be processed in series.

  In addition, the page data is not always in an appropriate direction and size with respect to the pixel arrangement of the camera, and may be reproduced obliquely or reproduced with enlargement or reduction. In such a case, the camera may be divided into a plurality of areas, and an optimum pattern may be selected in each area.

  FIGS. 14A to 14E show another example in which four types of pixels are arranged in the camera. Each of the 2 × 2 pixels of the camera has a pattern in which the same arrangement of four types of pixels a, b, c, and d is repeated. FIGS. 1 and 14 show an example in which the pixel a is arranged at the upper left of 2 × 2 pixels, but there are a total of 24 combinations in which a, b, c, and d are arranged in 2 × 2 pixels of the photodetector. In any case, decoding can be performed in the same manner.

  Note that the reproduction image may be enlarged or reduced due to factors such as defocusing of the disc. Therefore, the page data may be divided into predetermined areas and the adopted pattern may be changed for each area.

  In the present embodiment, a total of 9 pixels, 3 pixels per side, is arranged for each pixel of the page data. However, a configuration in which 3 pixels or more are arranged per side is possible, and an integer number is not necessarily required. There is no need for the number of pixels.

  In the above description, the angle multiplexing method in the holographic memory has been described as an example. However, the present invention can be similarly applied to a collinear method in which signal light and reference light are recorded on the same axis.

DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium, 10 ... Optical information recording / reproducing apparatus, 11 ... Pickup,
12 ... Phase conjugate optical system, 13 ... Disc Cure optical system,
14 ... Optical system for detecting the disk rotation angle, 50 ... Rotation motor,
81 ... Access control circuit, 82 ... Light source driving circuit, 83 ... Servo signal generation circuit,
84 ... Servo control circuit, 85 ... Signal processing circuit, 86 ... Signal generation circuit,
87 ... Shutter control circuit, 88 ... Disc rotation motor control circuit,
89 ... Controller,
201 ... light source, 202 ... collimating lens, 203 ... shutter,
204 ... 1/2 wavelength plate, 205 ... polarizing beam splitter,
206: Signal light, 207: Reference light,
208... Beam expander, 209 .. Phase mask,
210 ... relay lens, 211 ... polarizing beam splitter,
212 ... Spatial light modulator, 213 ... Relay lens, 214 ... Spatial filter,
215 ... Objective lens, 216 ... Polarization direction conversion element, 217 ... Mirror,
218 ... mirror, 219 ... mirror, 220 ... actuator,
221 ... lens, 222 ... lens, 223 ... actuator,
224 ... mirror, 225 ... photodetector, 230 ... beam expander,
231: Diffracted light, 250: Optical element, 251: Optical element

Claims (6)

A holographic memory reproducing device for reproducing information from a hologram recording medium on which an interference pattern generated by signal light and reference light is recorded,
Oscillator light generating means for generating oscillator light that overlaps and interferes with diffracted light from the hologram recording medium during reproduction;
Phase modulation means for adding a predetermined phase difference between the oscillator light and the diffracted light from the hologram recording medium;
A light detecting means for detecting interference light in which the oscillator light and the diffracted light from the hologram recording medium are superimposed;
Phase information detection means for detecting phase information added to each pixel of the signal light from information detected by the light detection means;
With
The holographic memory reproducing device, wherein the phase detection means detects phase information using a pixel of the photodetector that is not on a signal light pixel boundary for each pixel of the signal light. The phase modulation means adds at least three different phases to the oscillator light in addition to a predetermined reference phase,
The oscillator light having at least three different phases added to the reference phase and the reference phase is incident on each pixel and is superimposed on the diffracted light from the hologram recording medium. Incident,
2. The holographic memory reproducing device according to claim 1, wherein the phase information detecting means detects phase information added to each pixel of the signal light by using a principle of a fringe scanning method. The light detecting means arranges at least nine pixels for each pixel of the signal light,
2. The holographic memory reproducing device according to claim 1, wherein the phase information detecting means detects phase information using at least four of the nine pixels.   The phase information detection means calculates phase information with a combination of at least four patterns of four pixels among the nine pixels, adopts a good quality pattern from the four patterns of phase information, and obtains phase information. The holographic memory reproducing device according to claim 3 for detection. A reproduction method for reproducing information from a hologram recording medium in which an interference pattern generated by signal light and reference light is recorded,
Generating oscillator light that overlaps and interferes with diffracted light from the hologram recording medium during reproduction; and
Adding a predetermined phase difference between the oscillator light and the diffracted light from the hologram recording medium;
Detecting the interference light by superimposing the oscillator light and the diffracted light from the hologram recording medium;
Detecting phase information added to each pixel of the signal light from the interference light;
With
The step of detecting the phase information is a holographic memory reproducing method in which the phase information is detected using a pixel of the photodetector that is not on a boundary of the pixel of the signal light with respect to each pixel of the signal light. A holographic memory reproducing device for reproducing information from a hologram recording medium on which an interference pattern generated by signal light and reference light is recorded,
An oscillator light generator for generating an oscillator light that overlaps and interferes with the diffracted light from the hologram recording medium during reproduction;
A phase modulation section for adding a predetermined phase difference between the oscillator light and the diffracted light from the hologram recording medium;
A light detection unit that detects interference light in which the oscillator light and the diffracted light from the hologram recording medium are superimposed;
A phase information detector that detects phase information added to each pixel of the signal light from information detected by the light detection means;
With
A holographic memory reproducing device, wherein the number of pixels detectable by the photodetector is larger than the number of pixels in the two-dimensional page data recorded on the hologram recording medium.

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