JP2013171176A - Interleave number calculation device, program thereof, and hologram recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interleave number calculation device that calculates an optimum interleave number based on a characteristic of a hologram recording medium.SOLUTION: An interleave number calculation device 1 includes: characteristic evaluation image writing means 11 that writes a characteristic evaluation image into a hologram recording medium; characteristic evaluation image read-out medium 12 that reads out a reproduced image; evaluation characteristic parameter generation means 13 that generates a parameter such that a shape appearing on the reproduced image is specified in circular shape; binarized image symbol string generation means 14 that generates a symbol string from a pixel value of a binarized image in the shape specified by the parameter; temporary interleave symbol integration means 15 that reads out a symbol for each temporary interleave number from the symbol string and integrates luminance for each error correction block; and interleave number searching means 16 that regards a temporary interleave number such that a difference between a maximum value and a minimum value of a luminance integration value becomes minimum as an interleave number of the hologram recording medium.

Description

  The present invention relates to an interleave number calculation device that calculates the number of interleaves of data to be recorded on a hologram recording medium, a program thereof, and a hologram recording device that records / reproduces digital data using the hologram recording medium.

  In recent years, a hologram recording medium (holographic memory) has attracted attention as a large-capacity and high-speed accessible recording medium. In general, a hologram recording apparatus that records / reproduces digital data using this hologram recording medium generally irradiates the hologram recording medium with object light carrying the digital data together with reference light to form interference fringes formed in the hologram recording medium. Digital data is recorded by writing (hologram) on the medium. On the other hand, the hologram recording apparatus carries object light by irradiating a hologram recording medium on which digital data is recorded with reference light and causing light diffraction by interference fringes written in the medium. Digital data is reproduced (see, for example, Patent Document 1).

Here, an example of a conventional hologram recording apparatus will be briefly described with reference to the drawings.
First, a process for recording digital data on a hologram recording medium will be described with reference to FIG.
As shown in FIG. 12, in the conventional hologram recording apparatus 100 </ b> B, the laser light emitted from the laser light source 101 and passed through the shutter 102 (here, S-polarized light (vertically polarized light)) is transmitted by the half-wave plate 103. After the polarization plane is rotated to 45 degree polarization, the light is divided into transmitted light (P-polarized light) and reflected light (S-polarized light) by a PBS (Polarizing Beam Splitter) 104.

  Here, the P-polarized light transmitted through the PBS 104 passes through the shutter 105 and is irradiated on an SLM (Spatial Light Modulator) 107 made of a reflective liquid crystal element or the like. The irradiated P-polarized light carries digital data (page data) of a two-dimensional image with white and black bit patterns projected on the element surface of the SLM 107 generated by the arithmetic unit 1B and is converted to S-polarized light. (Actually, the light from the element displaying white is converted into S-polarized light) and returned to the PBS 106 as object light. The object light returned from the SLM 107 is reflected by the PBS 106 and irradiated onto the hologram recording medium 114 via an FT (Fourier Transform) lens 108.

  On the other hand, the S-polarized light reflected by the PBS 104 passes through the half-wave plate 109. At this time, the half-wave plate 109 keeps the polarization axis aligned with the polarization axis of the beam and does not rotate the polarization plane of the beam. The S-polarized light that has passed through the half-wave plate 109 enters the PBS 110 and is reflected. The S-polarized light reflected by the PBS 110 is sequentially reflected by the mirror 111 and the galvanometer mirror 112, passes through the relay lens 113, and is irradiated on the hologram recording medium 114 as reference light.

  As described above, since the reference light and the object light irradiated on the hologram recording medium 114 are both S-polarized light, they interfere on the hologram recording medium 114 to form interference fringes, and the interference fringes are recorded on the hologram recording. It will be written on the medium 114.

  In addition, the hologram recording apparatus 100B can perform multiplex recording (angle multiplex recording) of digital data (page data) in the hologram recording medium 114 by switching the incident angle of the reference light to the hologram recording medium 114 by the galvanometer mirror 112. I have to.

Next, processing for reproducing digital data from a hologram recording medium will be described with reference to FIG.
As shown in FIG. 13, when digital data is reproduced, the flow of the laser light emitted from the laser light source 101 to the PBS 104 is the same as in the recording described with reference to FIG. However, the P-polarized light transmitted through the PBS 104 is blocked by the shutter 105.
On the other hand, the S-polarized light reflected by the PBS 104 passes through the half-wave plate 109. At this time, the half-wave plate 109 changes the setting of the polarization axis to 45 degrees with respect to the polarization axis of the beam, and rotates the polarization plane by 90 degrees to change the S-polarized light to P-polarized light. Then, the P-polarized light that has passed through the half-wave plate 109 passes through the PBS 110. The P-polarized light that has passed through the PBS 110 is reflected by the galvanometer mirror 115, passes through the relay lens 116, and is applied to the hologram recording medium 114 as reference light.

  The reference light applied to the hologram recording medium 114 is diffracted by the interference fringes written on the hologram recording medium 114. The diffracted signal light is inversely transformed (Fourier inversely transformed) by the FT lens 108, passes through the PBS 106, and is imaged as object light by the two-dimensional imaging device 117, thereby reproducing digital data and calculating. Decoded by device 1B.

  The hologram recording apparatus 100B enables reading of digital data (page data) multiplexedly recorded on the hologram recording medium 114 by switching the incident angle to the P-polarized hologram recording medium 114 by the galvanometer mirror 115. ing.

  In the hologram recording apparatus as described above, a photopolymer recording medium is promising as a hologram recording medium in terms of recording sensitivity, storage stability, and recording capacity. However, since the photopolymer recording medium is accompanied by a polymerization reaction during recording, volume change such as medium shrinkage occurs. In the recording medium in which the volume change is caused in this way, the recorded interference fringes are distorted, and an area that does not satisfy the Bragg conditional expression (diffraction condition) occurs. Thus, in a region where the Bragg condition is not satisfied, there is a problem that the signal-to-noise ratio (SNR) is poor and the digital data (page data) cannot be read accurately.

  To solve this problem, an error correction code (inner code) is added to the digital data recorded on the hologram recording medium in units of logical pages, and an error correction code (outer code) is added across the pages. Thus, a technique for distributing errors generated by brightness and distortion in a physical page by performing inter-page interleaving that is completed in a logical page is disclosed (see Patent Document 2).

  In addition, a technique for correcting page data detected from a hologram recording medium by restoring an interleaved bright image and a dark image and performing gain compensation using the image is disclosed (Patent Document). 3).

  Further, before generating the page data, the data array is converted (interleaved), recorded on the hologram recording medium, and read out by the light detection means that can be read by random access. A technique for reading signals by deinterleaving so as to form an array is disclosed (see Patent Document 4).

JP 2007-305218 A JP 2007-66375 A Special table 2010-505139 JP 2008-140485 A

In the conventional method of dispersing the reading error of the hologram recording medium, the interleaving regularity and the optimal solution for the number of interleaving are not given, and the reading is performed simply by a predetermined rule and a predetermined number of interleaving. Only.
As described above, even if reading of the hologram recording medium is performed under conditions where regularity and optimum solutions are not given, the characteristics are different depending on the type of the hologram recording medium, so that the optimum effect cannot always be exhibited. There is a problem.

  The present invention has been made in view of such problems, and it is an object of the present invention to provide an interleaving number calculation device for obtaining an optimal interleaving number based on the characteristics of a hologram recording medium, a program thereof, and a hologram recording device. And

  The present invention was devised to solve the above-mentioned problems. First, the interleave number arithmetic apparatus according to claim 1 records the interleaved digital data as a hologram by interference fringes between object light and reference light. An interleaving number calculation device for calculating an interleaving number suitable for a hologram recording medium, which is provided in a hologram recording apparatus for recording on a medium, characterized by an image writing means for characteristic evaluation, an image reading means for characteristic evaluation, and an evaluation characteristic parameter generation Means, binary image symbol string generation means, provisional interleave symbol integration means, and interleave number search means.

  In such a configuration, the interleave number calculation device uses a characteristic evaluation image writing unit to convert a white image or a pattern image including at least one white pixel for each symbol of an arbitrary modulation method into a characteristic evaluation for a hologram recording medium. An image is written on the hologram recording medium. Note that data modulated by an arbitrary modulation scheme includes at least one white and black pixel for each symbol of the modulation scheme. Thus, by using a white image or a pattern image including white pixels in symbol units as a characteristic evaluation image, a region that does not satisfy the Bragg condition during reproduction and a region that satisfies the Bragg condition Can be distinguished from each other.

  Then, the interleave number calculation device reproduces the hologram recording medium on which the characteristic evaluation image is recorded by the characteristic evaluation image reading unit, and reads the reproduced image of the characteristic evaluation image. Further, the interleaving number calculation device generates, by the evaluation characteristic parameter generation means, a parameter that specifies, in a reproduced image, a shape that occurs on the reproduced image in accordance with the volume change of the hologram recording medium in a circular shape. That is, since the region satisfying the Bragg condition is reproduced as a circular shape, the shape is parameterized as a characteristic of the hologram recording medium.

  Then, the interleave number calculation device generates a binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation unit by the binary image symbol sequence generation unit, and presets the pixel value of the binary image. A symbol string arranged in units of the number of bits of the generated symbols is generated.

  Then, the interleaving number calculation device reads out symbols for each provisional interleaving number from the symbol sequence generated by the binary image symbol string generation means by the provisional interleave symbol accumulation means, and sets an error correction block having a preset number of symbols. The binarized luminance is integrated every time.

  Further, the interleaving number calculation device uses the interleaving number search means to calculate a temporary interleaving number at which the difference between the maximum and minimum binarized luminance integrated values for each error correction block is equal to or less than a predetermined reference value. Search for the interleave number of the hologram recording medium. In this manner, if the difference in luminance integrated value for each error correction block is small, symbol data is distributed and arranged in a region that satisfies the Bragg condition and a region that does not satisfy the Bragg condition in the hologram recording medium in which the volume change has occurred. Become.

  Further, the interleaving number computing device according to claim 2 is the interleaving number computing device according to claim 1, wherein the interleaving number searching means is configured to minimize the difference between the maximum value and the minimum value of the luminance integrated values. The number of interleaves is the interleave number of the hologram recording medium.

  In such a configuration, the interleaving number search means obtains the interleaving number that minimizes the difference between the maximum value and the minimum value of the luminance integration value, thereby optimally distributing the symbol data between the region that satisfies the Bragg condition and the region that does not satisfy Can be made.

  Further, the interleaving number computing device according to claim 3 is the interleaving number computing device according to claim 1, wherein the interleaving number search means is configured such that a difference between the maximum value and the minimum value of the luminance integrated value is predetermined. The interleaving number of the hologram recording medium is searched for within a range of temporary interleaving numbers that continue below the value.

  In such a configuration, the interleaving number search means specifies the interleaving number within a range of temporary interleaving numbers that are continuous when the difference between the maximum value and the minimum value of the luminance integrated value is equal to or less than a predetermined reference value. In addition, in the vicinity of the number of interleaves generated due to the influence of the optical system, it is possible to prevent the appearance of a symbol in which the difference between the maximum value and the minimum value of the luminance integrated value protrudes and becomes large.

  Furthermore, the interleaving number calculation program according to claim 4 is a hologram recording apparatus that records interleaved digital data on a hologram recording medium by interference fringes between object light and reference light, and sets an interleaving number suitable for the hologram recording medium. In order to perform the calculation, the computer is caused to function as a characteristic evaluation image writing unit, a characteristic evaluation image reading unit, an evaluation characteristic parameter generation unit, a binary image symbol string generation unit, a temporary interleave symbol integration unit, and an interleave number search unit. The configuration.

In such a configuration, the interleaving number calculation program uses a characteristic evaluation image writing unit to convert a white image or a pattern image including at least one white pixel for each symbol of an arbitrary modulation method into a characteristic evaluation for a hologram recording medium. An image is written on the hologram recording medium.
Then, the interleave number calculation program reproduces the hologram recording medium on which the characteristic evaluation image is recorded by the characteristic evaluation image reading means, and reads the reproduced image of the characteristic evaluation image.

Further, the interleaving number calculation program generates, by the evaluation characteristic parameter generation means, a parameter in which a shape generated on the reproduced image in accordance with the volume change of the hologram recording medium is specified in a circular shape in the reproduced image.
Then, the interleave number calculation program generates a binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation unit by the binary image symbol sequence generation unit, and presets the pixel value of the binary image. A symbol string arranged in units of the number of bits of the generated symbols is generated.

The interleaving number calculation program reads out symbols for each temporary interleaving number from the symbol sequence generated by the binary image symbol sequence generating means by the temporary interleave symbol integrating means, and sets an error correction block having a preset number of symbols. Accumulate every time.
Further, the interleave number calculation program searches for a temporary interleave number by which the difference between the maximum value and the minimum value of the luminance integrated value for each error correction block is equal to or less than a predetermined reference value by the interleave number search means, The number of media interleaves.

  The hologram recording apparatus according to claim 5 is a hologram recording apparatus that records interleaved digital data on a hologram recording medium by interference fringes between object light and reference light, and calculates an interleaving number suitable for the hologram recording medium. Interleaving number calculating means, and the interleaving number calculating means includes a characteristic evaluation image writing means, a characteristic evaluation image reading means, an evaluation characteristic parameter generating means, a binary image symbol string generating means, and a temporary interleave symbol integration. Means and interleave number search means.

In such a configuration, the interleave number calculation means of the hologram recording apparatus uses the characteristic evaluation image writing means to generate a white image or a pattern image including at least one white pixel for each symbol of an arbitrary modulation method. Is written on the hologram recording medium as a characteristic evaluation image.
Then, the interleave number calculating means reproduces the hologram recording medium on which the characteristic evaluation image is recorded by the characteristic evaluation image reading means, and reads the reproduced image of the characteristic evaluation image.

Further, the interleave number calculating means generates a parameter in which the shape generated on the reproduced image with the volume change of the hologram recording medium in the reproduced image is specified by the evaluation characteristic parameter generating means in a circular shape.
Then, the interleave number calculation means generates a binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation means by the binary image symbol string generation means, and presets the pixel value of the binary image. A symbol string arranged in units of the number of bits of the generated symbols is generated.

The interleave number calculation means reads out symbols for each temporary interleave number from the symbol sequence generated by the binary image symbol string generation means by the temporary interleave symbol integration means, and sets an error correction block having a preset number of symbols. The binarized luminance is integrated every time.
Further, the interleaving number calculating means calculates a temporary interleaving number at which a difference between the maximum value and the minimum value of the binarized luminance integrated value for each error correction block is equal to or less than a predetermined reference value by the interleaving number search means. Search for the interleave number of the hologram recording medium.

The present invention has the following excellent effects.
According to the first and fourth aspects of the present invention, errors can be efficiently dispersed according to the characteristics of the hologram recording medium even when a volume change such as medium shrinkage of the hologram recording medium occurs. The number of interleaving can be obtained.

  According to the second aspect of the present invention, even when a volume change such as medium shrinkage of the hologram recording medium occurs, an optimum error can be efficiently dispersed according to the characteristics of the hologram recording medium. The number of interleaving can be obtained.

  According to the third aspect of the present invention, even in an environment where noise and optical system shift occur, the luminance in the hologram changes greatly when a volume change such as medium shrinkage of the hologram recording medium occurs. The number of interleaves that can prevent this can be obtained.

  According to the fifth aspect of the present invention, even when a volume change such as medium shrinkage of the hologram recording medium occurs, errors can be efficiently dispersed according to the characteristics of the hologram recording medium. As a result, burst errors can be dispersed, and errors can finally be suppressed to the maximum by the error correction function of the hologram recording apparatus.

It is the schematic which shows the structure of the hologram recording apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the calculating device (interleave number calculating device) of the hologram recording device which concerns on embodiment of this invention. It is a figure which shows the reproduced image (reproduction image for evaluation characteristics) reproduced after recording the image for evaluation characteristics on the hologram recording medium. It is explanatory drawing for demonstrating the parameter which specifies the reproduction image for evaluation characteristics with a circle. It is explanatory drawing for demonstrating the mechanism which produces | generates the symbol sequence in the binary image symbol sequence production | generation means of an interleave number arithmetic unit. It is explanatory drawing for demonstrating the luminance integration value per error correction block by interleaving with the temporary interleave number in the temporary interleave symbol integration means of the interleave number arithmetic unit. It is explanatory drawing for demonstrating the process of the surplus and deficiency of the symbol which arises when interleaving by the temporary interleave number in the temporary interleave symbol integration means of the interleave number arithmetic unit. It is explanatory drawing for demonstrating the flow of the data which displays a recording signal on SLM in a recording signal calculating means. It is a flowchart which shows operation | movement of the characteristic evaluation means of the interleave number calculating apparatus which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the interleave number specific | specification means of the interleave number calculating apparatus which concerns on embodiment of this invention. It is a graph which shows the relationship between the number of interleaving in the interleaving number calculating apparatus which concerns on embodiment of this invention, and the difference of an integrated luminance value. It is the schematic which shows the structure of the conventional hologram recording apparatus, Comprising: It is a figure for demonstrating the operation | movement of hologram recording especially. It is the schematic which shows the structure of the conventional hologram recording apparatus, Comprising: It is a figure for demonstrating especially the operation | movement of hologram reproduction.

Embodiments of the present invention will be described below with reference to the drawings.
[Hologram recording device]
Initially, with reference to FIG. 1, the structure of the hologram recording apparatus provided with the interleave number calculating apparatus (interleave number calculating means) which concerns on embodiment of this invention is demonstrated. The hologram recording apparatus 100 in FIG. 1 can have the same configuration as the hologram recording apparatus 100B described in FIG. 12 and FIG. 13 except for the arithmetic apparatus 1 (including the interleave number arithmetic apparatus). The same reference numerals are given. Hereinafter, a configuration similar to the conventional one will be briefly described.

  As shown in FIG. 1, the hologram recording apparatus 100 performs hologram recording and reproduction of digital data by an angle multiplexing method. Here, the hologram recording apparatus 100 includes an arithmetic unit 1, a laser light source 101, a shutter 102, a half-wave plate 103, a PBS (polarization beam splitter) 104, a shutter 105, a PBS 106, and an SLM (space. Optical modulator) 107, FT (Fourier transform) lens 108, half-wave plate 109, PBS 110, mirror 111, galvano mirror 112, relay lens 113, hologram recording medium 114, and galvano mirror 115. And a relay lens 116 and a two-dimensional image sensor 117.

The calculation device 1 performs various calculations necessary for hologram recording and reproduction. This computing device 1 computes digital data (page data) to be recorded on the hologram recording medium 114 from a recording signal inputted from the outside, and outputs it from the digital data reproduced from the hologram recording medium 114 to the outside. Calculate the playback signal to be played.
The arithmetic device 1 also has a function of calculating an optimum interleave number in consideration of a volume change such as medium contraction that occurs when a hologram (interference fringe) is recorded on the hologram recording medium 114.

  Here, when recording a hologram, the arithmetic unit 1 receives a recording signal such as a video signal or data to be recorded on the hologram recording medium 114 from the outside. Then, the arithmetic device 1 adds or corrects an error correction code to the recording signal, and converts (interleaves) the data array in accordance with the number of interleaves, thereby converting the digital data (pages) as a two-dimensional bit pattern. Data) is generated and output to the SLM 107.

  Further, when reproducing the hologram, the arithmetic unit 1 receives reproduction digital data (page data) from the two-dimensional image sensor 117. Then, the arithmetic unit 1 performs reverse conversion (deinterleaving) on the reproduced digital data according to the number of interleaves, and generates a reproduction signal such as a video signal and data by performing demodulation and error correction. Output to the outside. Details of the arithmetic device 1 (including the interleave number arithmetic device) will be described later.

  The laser light source 101 emits laser light serving as object light or reference light. The laser light source 101 can be composed of, for example, an external resonator type blue-violet semiconductor laser that emits blue-violet laser light. Laser light emitted from the laser light source 101 enters the shutter 102. Here, the laser light source 101 emits S-polarized laser light (parallel light).

  The shutter 102 controls the irradiation or blocking of the laser beam on the hologram recording medium 114. Here, the shutter 102 allows the laser beam to pass when recording or reproducing the hologram, and blocks the laser beam otherwise. The laser light that has passed through the shutter 102 is incident on the half-wave plate 103.

  The half-wave plate 103 rotates the polarization plane of the laser light that has passed through the shutter 102. Here, the half-wave plate 103 rotates the plane of polarization to 45-degree polarized light. The light whose polarization plane has been rotated 45 degrees is incident on the PBS 104.

  A PBS (polarized beam splitter) 104 separates incident light according to its polarization component. Here, the PBS 104 transmits the P-polarized light out of the light incident from the half-wave plate 103 and irradiates the shutter 105. On the other hand, the s-polarized light is reflected and applied to the half-wave plate 109.

  The shutter 105 controls the irradiation or blocking of the laser beam on the hologram recording medium 114. Here, the shutter 105 allows laser light (P-polarized light) to pass when recording a hologram, and blocks the laser light when reproducing the hologram. The laser light (P-polarized light) that has passed through the shutter 105 is incident on the PBS 106.

The PBS 106 separates incident light according to its polarization component. Here, the PBS 106 transmits the P-polarized light incident from the shutter 105 and irradiates the SLM 107. Further, the PBS 106 reflects and irradiates the FT lens 108 with respect to the object light (S-polarized light) returning from the SLM 107.
Note that the PBS 106 transmits the object light (P-polarized light) emitted from the hologram recording medium 114 via the FT lens 108 and irradiates the two-dimensional image sensor 117 when reproducing the hologram.

The SLM (spatial light modulator) 107 modulates the plane of polarization of light for each element corresponding to a pixel of digital data (page data) using optical elements arranged in a two-dimensional array. Here, with respect to the P-polarized light irradiated from the PBS 106, the page data of the image by the white and black bit patterns displayed on the element surface (not shown) of the SLM 107, which is digital data input from the arithmetic unit 1, is displayed. Among them, the light irradiated to the element displaying white is reflected by being converted to S-polarized light by the rotation of the vibration surface (not shown) in the element displaying white, and the P-polarized light is reflected for the element displaying black. Reflect as it is.
The reflected P-polarized light is transmitted through the PBS 106, while the S-polarized light is reflected by the PBS 106 and used as object light carrying digital data (page data).

The FT lens 108 collects object light (S-polarized light) and irradiates the hologram recording medium 114. That is, the FT lens 108 converts object light into light on the recording surface of the hologram recording medium 114 by optical Fourier transform at the time of hologram recording.
In addition, the FT lens 108 converts light incident from the hologram recording medium 114 into object light (P-polarized light). In other words, the FT lens 108 converts light incident from the hologram recording medium 114 into object light (P-polarized light) by optical inverse Fourier transform when reproducing the hologram.

The half-wave plate 109 controls the polarization plane of the laser light (S-polarized light) reflected by the PBS 104. That is, at the time of hologram recording, the half-wave plate 109 maintains the S polarization without rotating the polarization plane of the laser light (S polarization) reflected by the PBS 104 by aligning the polarization axis with the polarization axis of the beam. Pass through. The half-wave plate 109 rotates the polarization plane of the laser beam (S-polarized light) reflected by the PBS 104 by 90 degrees by setting the polarization axis to 45 degrees with respect to the polarization axis of the beam during hologram reproduction. And converted to P-polarized light.
The PBS 110 is irradiated with the S-polarized light that has passed through the half-wave plate 109 or the P-polarized light whose polarization plane has been rotated by the half-wave plate 109.

The PBS 110 separates incident light according to its polarization component. Here, the PBS 110 reflects the S-polarized light out of the light incident from the half-wave plate 109 and irradiates the mirror 111 with it. This S-polarized light becomes reference light at the time of hologram recording.
The PBS 110 transmits P-polarized light out of the light incident from the half-wave plate 109 and irradiates the galvanometer mirror 115. This P-polarized light becomes reference light when reproducing the hologram.

  The mirror 111 reflects the reference light (S-polarized light) reflected by the PBS 110 and guides it to the galvanometer mirror 112.

  The galvanometer mirror 112 switches the irradiation angle of the reference light (S-polarized light) (corresponding to the incident angle on the hologram recording medium 114) during recording of the hologram. Recording the digital data on the hologram recording medium 114 can be multiplexed by rotating the irradiation angle of the galvanometer mirror 112 by a minute angle via a rotation driving means (not shown). Here, the galvanometer mirror 112 reflects the reference light (S-polarized light) reflected by the mirror 111 to the relay lens 113.

  The relay lens 113 forms an image of the reference light (S-polarized light) reflected by the galvanometer mirror 112 on the hologram recording medium 114 via a plurality of lens systems. For example, the relay lens 113 includes a convex lens group in which a plurality of convex lenses are arranged.

The hologram recording medium 114 is a general holographic memory that records interference fringes (holograms) generated by irradiation of object light and reference light having the same polarization. For example, the hologram recording medium 114 is a photopolymer recording medium.
Here, the hologram recording medium 114 includes object light (S-polarized light) carried as digital data of a two-dimensional image by the SLM 107 and reference light (S-polarized light) generated from laser light by the PBS 110 at the time of hologram recording. Interference fringes generated by irradiating are recorded.

  In addition, the hologram recording medium 114 emits light diffracted by the recorded interference fringes by irradiating the reference light (P-polarized light) generated from the laser light by the PBS 110 when reproducing the hologram. This diffracted light is Fourier-transformed by the FT lens 108 to become object light (P-polarized light).

  The galvanometer mirror 115 switches the irradiation angle of the reference light (P-polarized light) (corresponding to the incident angle on the hologram recording medium 114) during reproduction of the hologram. By rotating the irradiation angle of the galvanometer mirror 115 by a minute angle via a rotation driving means (not shown), it becomes possible to read digital data multiplexed and recorded on the hologram recording medium 114. . Here, the galvanometer mirror 115 reflects the reference light (P-polarized light) transmitted through the PBS 110 to the relay lens 116.

  The relay lens 116 images the reference light (P-polarized light) reflected by the galvanometer mirror 115 on the hologram recording medium 114 through a plurality of lens systems. For example, the relay lens 116 includes a convex lens group in which a plurality of convex lenses are arranged.

  The two-dimensional image sensor 117 captures object light (P-polarized light) emitted from the hologram recording medium 114 via the FT lens 108. The two-dimensional image sensor 117 is, for example, a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like. The two-dimensional image sensor 117 outputs the captured luminance signal (reproduced digital data) to the arithmetic device 1.

[Configuration of arithmetic unit (interleave number arithmetic unit)]
Next, the configuration of the arithmetic device 1 will be described in detail with reference to FIG. As shown in FIG. 2, the computing device 1 includes an interleave number computing means 10, a recording signal computing means 20, and a reproduction signal computing means 30.

  The interleave number calculation means (interleave number calculation device) 10 calculates the number of interleaves of digital data recorded on the hologram recording medium 114. The interleave number calculating means 10 operates at the stage when an interleave number calculation instruction is input from the outside. Here, the interleave number calculation means 10 includes a characteristic evaluation means 10A and an interleave number identification means 10B.

  The characteristic evaluation unit 10A performs characteristic evaluation of the hologram recording medium 114. This characteristic evaluation means 10A quantifies the volume change characteristic that occurs when a hologram is recorded on the hologram recording medium 114 as an evaluation characteristic parameter. Here, the characteristic evaluation unit 10 </ b> A includes a characteristic evaluation image writing unit 11, a characteristic evaluation image reading unit 12, and an evaluation characteristic parameter generation unit 13.

The characteristic evaluation image writing unit 11 outputs the characteristic evaluation image to the SLM 107 as digital data (page data), and writes a hologram on the hologram recording medium 114 with object light corresponding to the image. Here, the characteristic evaluation image is an entire white image (white image) or a pattern image in which two-dimensional digital data modulated by an arbitrary modulation method is arranged. Since the two-dimensional digital data is data modulated by a modulation method, at least one pixel of white and black is included for each symbol constituting the code. Here, two-dimensional digital data (pattern image) is used as the characteristic evaluation image.
Note that the characteristic evaluation image writing unit 11 may store the characteristic evaluation image in a storage unit (not shown) in advance, or may generate the characteristic evaluation image when an interleave number calculation instruction is input. Good.

  The characteristic evaluation image reading means 12 reproduces the characteristic evaluation image hologram written on the hologram recording medium 114 by the characteristic evaluation image writing means 11 and reads it from the two-dimensional image sensor 117. The reproduction image (characteristic evaluation reproduction image) read by the characteristic evaluation image reading unit 12 is output to the evaluation characteristic parameter generation unit 13.

  In hologram recording, the reproduction state of a reproduction image is determined depending on whether or not the Bragg condition is met in k (wave vector) space. That is, when a photopolymer recording medium is used as the hologram recording medium 114, when a volume change such as medium contraction occurs in the hologram recording medium 114, the reproduced image read by the characteristic evaluation image reading means 12 is as shown in FIG. It becomes a circular arc shape. FIG. 3 shows that the inner and outer portions of the arc shape do not meet the Bragg condition. This phenomenon is described in the literature “K. Curtis, L. Dhar, A. Hill, W. Wilson, M. Ayres,“ Holographic Data Storage ”, John Wiley & Sons, Inc., p.342, 2010”. ing.

  Further, depending on the volume change of the hologram recording medium 114, the reproduction condition (tilt or the like) varies. If this reproduction condition is not optimized, the error rate of the reproduced digital data will increase. Therefore, the hologram recording medium 114 is placed on a two-axis rotation stage (not shown), and the characteristic evaluation image reading means 12 reproduces the arc-shaped center (that is, the arc-shaped center of gravity) that is the reproduced image and the reproduced image. It is preferable to perform tilt control so that the distance from the center of the image is the shortest (below a predetermined threshold).

The evaluation characteristic parameter generation unit 13 uses, as an evaluation characteristic parameter, a characteristic when a hologram is recorded on the hologram recording medium 114 based on the reproduction image (characteristic evaluation reproduction image) read by the characteristic evaluation image reading unit 12. It is to be quantified.
Here, the evaluation characteristic parameter generating unit 13 includes a binarizing unit 13a and a circular shape specifying unit 13b.

The binarizing means 13a binarizes the reproduced image read by the characteristic evaluation image reading means 12. That is, when the reproduced image captured by the two-dimensional image sensor 117 is a multi-valued image, the binarizing unit 13a binarizes the reproduced image with a predetermined reference value as a boundary.
This binarized reproduced image is output to the circular shape specifying means 13b.

The circular shape specifying unit 13b specifies the reproduced image read by the characteristic evaluation image reading unit 12 with a circular shape. Here, the circular shape specifying unit 13b specifies the circular arc shape on the reproduced image binarized by the binarizing unit 13a by the circular shape and parameterizes it.
Since the reproduced image read by the characteristic evaluation image reading means 12 is a reproduced image in k (wave vector) space, the arc shape on the reproduced image is precisely an elliptic arc shape. However, the major and minor radii of this elliptical arc shape are approximately equal and may be considered as a circular shape. Here, the circular shape specifying unit 13b fits a circular shape (center [coordinate], Radius and width) are used as evaluation characteristic parameters.

Specifically, the circular shape specifying unit 13b generates a circular image in which the center C, the radius R, and the width W are arbitrarily changed as shown in FIG. 4, and is most similar to the binarized reproduced image. The center C, radius R, and width W are specified. Alternatively, the circular shape specifying unit 13b may perform the similarity determination by setting the center C as the center of gravity in the reproduced image and changing only the radius R and the width W. Note that the image similarity determination may be performed using a general method. For example, the similarity determination may be performed based on a mean square error obtained by taking a difference for each pixel.
Further, the evaluation characteristic parameter does not necessarily need to be the center, radius, and width as long as the shape of the circle can be specified. For example, it may be the center of the circle, the radius of the inner circle, or the radius of the outer circle.

  The evaluation characteristic parameters (circle center, radius, width) generated by the evaluation characteristic parameter generation means 13 can be regarded as the same because the characteristics are almost the same if the type of the hologram recording medium 114 is the same. . Therefore, the evaluation characteristic parameter generation unit 13 stores the generated evaluation characteristic parameter in association with the type of the hologram recording medium 114 in a storage unit such as a semiconductor memory (not shown).

The interleaving number specifying means 10B specifies the optimum interleaving number in the data interleaving method set from the outside, using the characteristic evaluation parameters of the hologram recording medium 114 specified by the characteristic evaluation means 10A.
That is, the interleaving number specifying means 10B disperses errors in the error correction block when data is recorded by a predetermined encoding method with a predetermined number of interleaved pages between pages (the number of interleaved pages in multiple directions). Specify the number of interleaves for

This interleaving number specifying means 10B uses the number of bits per symbol (s bits) in the encoding method and the number of symbols to be displayed on the SLM 107 as parameters for specifying the interleaving method of data set from outside (interleaving method specifying parameter). Assume that (horizontal h symbols × vertical v symbols), the number of symbols per error correction block (t symbols), and the number of interleaved pages between pages (p pages) are set.
Here, the interleave number specifying means 10B includes a binary image symbol string generation means 14, a temporary interleave symbol accumulation means 15, and an interleave number search means 16.

The binary image symbol sequence generation unit 14 generates a symbol sequence in which pixel values of a binary image having a shape specified by the characteristic evaluation parameter generated by the characteristic evaluation unit 10A are arranged in units of the number of bits of a set symbol. To do.
That is, the binary image symbol string generation means 14 first generates a circular binary image having a width whose shape is specified by the characteristic evaluation parameters (center, radius, width) shown in FIG. At this time, the inside of the circle is white, and the other is black (for example, in the two-dimensional image sensor 117, if one pixel is 1 bit, white is “1”, black is “0”, and 8-bit display is used. , White is “255” and black is “0”).

Then, the binary image symbol sequence generation unit 14 generates an array for each set number of bits s per symbol. The binary image symbol string generation unit 14 generates the same array by the number of pages p if there are a plurality of set interpage page numbers p.
Symbol sequences corresponding to the number of interleaved pages generated by the binary image symbol sequence generation unit 14 are output to the temporary interleave symbol integration unit 15.

Here, with reference to FIG. 5, the symbol sequence generated by the binary image symbol sequence generation means 14 will be schematically described.
As shown in FIG. 5, the binary image symbol string generation means 14 generates a circular image P ₁ having a width whose shape is specified by the characteristic evaluation parameters (center, radius, width). Then, the binary image symbol sequence generation means 14 generates a numerical sequence for each bit number per symbol in the direction of the arrow (horizontal direction) in FIG. Also, if the number of interleaved pages between pages p is plural, the binary image symbol sequence generation means 14 duplicates and concatenates the numerical sequence generated with the black and white image P ₁ , so that p pages (P _{1 to} P _p ) Minutes of symbol strings are generated. That is, the last symbol columns of the image P _1, the beginning of the symbol string image P ₂ is connected.
Returning to FIG. 2, the description of the configuration of the arithmetic device 1 will be continued.

Temporary interleave symbol integration means 15 reads the value of the symbol sequence generated by binary image symbol sequence generation means 14 for each provisional interleave number, and integrates the luminance for each set error correction block symbol number t. To do. This luminance integrated value indicates the luminance sum in units of error correction blocks.
The provisional interleave symbol accumulating unit 15 sequentially changes the provisional interleave number A within a range not less than 1 and not more than the total number of symbols (h × v × p) within the interpage interleaved page number p. The integrated luminance value is obtained for each error correction block with the number of interleaves.

However, when obtaining the luminance integrated value for each error correction block, the temporary interleave symbol integrating means 15 does not necessarily have to calculate all the values that the temporary interleave number A can take. For example, the optimal number of interleavings exists in the vicinity of a value (h × v × p / t) obtained by dividing the total number of symbols (h × v × p) by the number of symbols t per error correction block t. Therefore, the provisional interleaving number A is set within a predetermined numerical range before and after the value of h × v × p / t, and the luminance integrated value for each error correction block may be obtained. .
The luminance integrated value for each symbol number t integrated by the provisional interleave symbol integration means 15 is output to the interleave number search means 16 together with the provisional interleaving number at the time of integration.

Here, with reference to FIG. 6, the processing content of the temporary interleave symbol integrating means 15 will be schematically described.
As shown in FIG. 6 (a), the temporary interleave symbol accumulating unit 15 reads all the symbol sequence values generated by the binary image symbol sequence generation unit 14 for each temporary interleave number A. Symbols S (h × v × p) are two-dimensionally arranged in A rows (h × v × p / A) columns, and the two-dimensional matrix is read in the vertical direction as shown in FIG. It corresponds to. As a result, after a certain symbol, a symbol at a position separated by the temporary interleaving number A is read out.
Then, the temporary interleaved symbol integrating means 15 performs the luminance integrated value (B _{1 to} B _n) for each number of symbols t per error correction block as shown in FIG. 6C in the reading order of FIG. )

As shown in FIG. 6A, when symbol strings are two-dimensionally arranged, a complete two-dimensional matrix may not be obtained depending on the provisional interleaving number A.
For example, as shown in FIG. 7A, when a symbol string is two-dimensionally arranged, a remainder is generated, or as shown in FIG. 7B, when a symbol string is two-dimensionally arranged, a shortage occurs. There is. However, as shown in FIG. 7A, even if a remainder is generated in the two-dimensional array, the temporary interleave symbol integrating means 15 sequentially reads out the remaining symbols after sequentially reading out in the vertical direction. What is necessary is just to obtain | require the brightness | luminance integrated value for every correction block. Further, as shown in FIG. 7B, even when a shortage occurs in the two-dimensional array, only the symbols present in the vertical direction are sequentially read out to obtain the luminance integrated value for each error correction block.
Returning to FIG. 2, the description of the configuration of the arithmetic device 1 will be continued.

  The interleave number search means 16 searches for the interleave number that minimizes the difference between the maximum value and the minimum value in the luminance integrated value for each error correction block in the temporary interleave number integrated by the temporary interleave symbol integration means 15. Is.

Usually, in hologram recording, there is a tendency that a bright part has a high SNR (signal to noise intensity ratio) and a dark part has a low SNR. Therefore, the interleave number search means 16 calculates a difference (B _max −B _min ) from the maximum value (B _max ) and the minimum value (B _min ) in the luminance integrated value for each error correction block, and the difference Is determined as the optimum interleaving number A ′.
The interleave number searched by the interleave number search means 16 is stored in a storage means such as a semiconductor memory (not shown) and is referred to by a recording signal calculation means 20 and a reproduction signal calculation means 30 described later.

Depending on the noise and the influence of the optical system, the difference may increase in a spike manner in the vicinity of the number of interleaves where the difference between the maximum value and the minimum value of the luminance integrated value is minimum. In this case, even when the number of interleaves that minimizes the difference is employed, the difference in luminance integrated value (B _max −B _min ) may increase due to the influence of noise or the like.
As described above, when the system is unstable, the interleave number search means 16 determines that the difference between the maximum value and the minimum value of the integrated luminance value is not more than a predetermined reference value when searching for the interleave number. From the range of the number of interleavings, the number of interleavings that minimizes the difference may be selected.

  The configuration of the interleave number calculation means (interleave number calculation device) 10 has been described above. However, when the type of the hologram recording medium 114 is the same and the interleave method is changed, for example, per symbol according to the change of the encoding method. When the number of bits is changed, the characteristics of the hologram recording medium 114 are the same. Therefore, the operation of the characteristic evaluation unit 10A is omitted and stored in advance in association with the type of the hologram recording medium 114. Using the evaluation characteristic parameter, the interleave number specifying means 10B may specify the interleave number.

  The recording signal calculation means 20 calculates digital data for recording on the hologram recording medium 114 from a recording signal such as a video signal and data input from the outside. Here, the recording signal calculation unit 20 includes an error correction code addition unit 21, a modulation unit 22, an interleaving unit 23, and a data writing 24.

  The error correction code adding means 21 adds an error correction code to the recording signal for each number of bits of a predetermined modulation method. The error correction code adding means 21 outputs the recording signal with the error correction code added to the modulation means 22.

  The modulation means 22 modulates the recording signal to which the error correction code is added with a preset modulation method. For example, the modulation means 22 modulates the recording signal by a general modulation method such as 2-4 modulation. As a result, data (symbol data string) in the symbol unit of the modulation method is generated from the recording signal. The modulation means 22 outputs the generated symbol data string to the interleaving means 23.

  The interleaving unit 23 interleaves the symbol data sequence generated by the modulation unit 22 with the interleave number calculated by the interleave number calculation unit 10 and rearranges the symbol data sequence into an array of two-dimensional images. That is, the interleaving means 23 reads the symbol data string for each interleave number, and rearranges the symbol data string into a two-dimensional data array corresponding to the SLM 107. The interleaving means 23 outputs the generated two-dimensional data array to the data writing means 24.

The data writing unit 24 outputs the two-dimensional data array input from the interleaving unit 23 to the SLM 107 as digital data (page data). In this way, by outputting the two-dimensional data array to the SLM 107, the two-dimensional image is displayed on the SLM 107 and recorded on the hologram recording medium 114 as a hologram.
In addition, when recording a plurality of two-dimensional images on the hologram recording medium 114, the data writing unit 24 performs multiplex recording by switching the incident angle of the reference light to the hologram recording medium 114 by the galvanometer mirror 112.

Here, with reference to FIG. 8, a data flow in which the recording signal calculation unit 20 displays the recording signal on the SLM 107 using the calculated number of interleaves will be described.
As shown in FIG. 8A, when a bit string recording signal is input, the error correction code adding means 21 adds an error correction code every predetermined number of bits as shown in FIG. 8B.
Then, as shown in FIG. 8C, the modulation means 22 modulates with a preset modulation method, and converts data of a predetermined number of bits into data of the symbol S.

Then, as shown in (d-1) of FIG. 8D, the interleaving means 23 uses the interleaving number A ′ specified by the interleaving number calculating means 10 to generate all symbols S (h × v × p ) Are two-dimensionally arranged in (h × v × p / A ′) rows and A ′ columns, and as shown in (d-2), the two-dimensional matrix is read in the vertical direction and horizontally displayed on the SLM 107 in the horizontal direction. Display for each number of pixels. As a result, the symbol sequence is interleaved by the optimum interleave number A ′ and displayed on the SLM 107 as a two-dimensional image (digital data).
Returning to FIG. 2, the description of the configuration of the arithmetic device 1 will be continued.

  The reproduction signal calculation means 30 reproduces a signal from reproduction digital data obtained by imaging the hologram object light recorded on the hologram recording medium 114 with the two-dimensional imaging element 117. Here, the reproduction signal calculation means 30 includes data reading means 31, deinterleaving means 32, demodulation means 33, and error correction means 34.

The data reading unit 31 reads digital data (reproduced digital data) imaged by the two-dimensional image sensor 117. The data reading unit 31 outputs the read digital data to the deinterleaving unit 32.
In addition, when reading the data recorded in multiple recording, the data reading unit 31 reads the individual data recorded in multiple recording by switching the incident angle of the reference light to the hologram recording medium 114 by the galvanometer mirror 115.

  The deinterleave means 32 interleaves the digital data read by the data read means 31 with the number of interleaves calculated by the interleave number calculation means 10 and rearranges it into a one-dimensional data string. That is, the deinterleaving unit 32 performs a reverse process of the interleaving unit 23 to generate a one-dimensional symbol sequence. The deinterleaving means 32 outputs the rearranged one-dimensional symbol sequence to the demodulation means 33.

  The demodulator 33 demodulates the symbol sequence rearranged by the deinterleaver 32 by a preset demodulation method. That is, the demodulating unit 33 generates a bit string by performing reverse processing of the modulation method performed by the modulating unit 22. The demodulating unit 33 outputs the generated bit string to the error correcting unit 34.

  The error correction unit 34 performs error correction on the bit string demodulated by the demodulation unit 33 to generate a reproduction signal and output it to the outside. That is, the error correction means 34 uses the error correction code added by the error correction code addition means 21 to correct errors in consecutive bit strings and generate a reproduction signal.

The arithmetic device 1 (interleave number arithmetic device 10) described above can be realized by a program for causing a general computer to function as each means described above.
By configuring the arithmetic device 1 (interleave number arithmetic device 10) in this way, the hologram recording device 100 can optimally interleave digital data with respect to the distortion of the hologram accompanying the volume change of the hologram recording medium 114. it can. As a result, the hologram recording apparatus 100 can disperse burst errors, and can make maximum use of error correction by error correction codes.

[Operation of interleave number calculation means (interleave number calculation device)]
Next, the operation of the interleave number calculation means (interleave number calculation device) 10 will be described with reference to FIGS. 9 and 10 (refer to FIGS. 1 and 2 as appropriate). The operations of the recording signal calculation means 20 and the reproduction signal calculation means 30 are general hologram recording / reproduction operations except that the interleaving number obtained by the interleaving number calculation means 10 is used. To do.

  Here, with reference to FIG. 9, the operation of evaluating the characteristics of the hologram recording medium 114 in the characteristic evaluation means 10A of the interleave number calculation means 10 will be described, and with reference to FIG. An operation for specifying the optimum number of interleaves in the number specifying means 10B will be described.

First, as shown in FIG. 9, the interleave number calculation means 10 arranges a white image (white image) or two-dimensional digital data modulated by an arbitrary modulation method by the characteristic evaluation image writing means 11. The pattern image thus recorded is recorded on the hologram recording medium 114 as a characteristic evaluation image (step S10). At this stage, the hologram recording medium 114 undergoes a volume change such as medium shrinkage.
Then, the interleave number calculation means 10 reproduces the hologram of the characteristic evaluation image written in the hologram recording medium 114 by the characteristic evaluation image reading means 12, and obtains a reproduction image (reproduction image for characteristic evaluation) (step). S11). The reproduction image for characteristic evaluation is an image having an arc shape as shown in FIG.

Then, the interleave number calculating means 10 binarizes the reproduced image acquired in step S11 by the binarizing means 13a of the evaluation characteristic parameter generating means 13 (step S12). Further, the interleaving number calculation means 10 performs circle fitting on the reproduced image binarized in step S12 by the circle shape specifying means 13b of the evaluation characteristic parameter generation means 13 so that the circle shape (center [coordinate], Radius and width) are generated as evaluation characteristic parameters (step S13).
With the above operation, the characteristics of the hologram recording medium 114 when the hologram is recorded can be specified.

  Next, as shown in FIG. 10, the interleave number calculation unit 10 performs the binary image symbol sequence generation unit 14 on the binary image having the shape specified by the evaluation characteristic parameter generated in step S <b> 13 (FIG. 9). A symbol string in which pixel values are arranged in units of the number of bits of the set symbol is generated (step S20). That is, the binary image symbol sequence generation means 14 generates a symbol sequence as the pixel value of a circular binary image (an image in which pixels on the circle are white and others are black) specified by the evaluation characteristic parameter. To do.

  Then, the interleave number calculation means 10 reads (rearranges) the value of the symbol string generated in step S20 by the provisional interleave symbol accumulation means 15 for each of a plurality of provisional interleave numbers, and sets the error correction. Integration is performed for each number of symbols in the block (step S21). As a result, a luminance value sum is obtained for each error correction block for each provisional interleaving number.

Then, the interleave number calculation means 10 calculates a temporary interleave number that minimizes the difference between the maximum value and the minimum value in the luminance integrated value for each error correction block calculated by the interleave number search means 16 in step 21. Search is performed as the optimum number of interleaves (step S22). At this time, the interleaving number search means 16 may specify the interleaving number at which the difference between the maximum value and the minimum value of the luminance integrated value is equal to or less than the reference value as the optimum interleaving number. Alternatively, the interleaving number that minimizes the difference may be specified from among the continuous interleaving numbers that have a difference between the maximum value and the minimum value of the luminance integrated values that are equal to or less than a predetermined reference value.
With the above operation, the interleave number calculating means 10 can obtain the interleave number that can disperse the burst error with respect to the distortion of the hologram accompanying the volume change caused by the hologram recording.

[Evaluation results]
Finally, with reference to FIG. 11, the evaluation result when the interleave number calculation means (interleave number calculation device) 10 selects the interleave number will be described.
Here, data in which the number of horizontal symbols h of 1SLM data is 1421 symbols, the number of vertical symbols v is 1891, the number of symbols t per error correction block is 250, and the number of interleaved pages between pages p is 8 is used.

At this time, the interleave number calculation means (interleave number calculation device) 10 finds the difference (B) between the searched interleave number A and the maximum value (B _max ) and minimum value (B _min ) of the luminance integrated value for each error correction block. FIG. 11 shows the graph of ( _max− B _min ).
Note that the difference (B _max −B _min ) between the maximum value (B _max ) and the minimum value (B _min ) when the luminance integrated value for each error correction block is simply obtained without performing symbol rearrangement or the like is , “63,621”.

At this time, when the interleaving number calculation means 10 selects the interleaving number that minimizes the difference (B _max −B _min ) as the optimum interleaving number, the interleaving number is “52,948”, and the difference (B _max− B _min ) was “1,544”.
That is, when the optimum interleaving number is selected by the interleaving number calculating means 10, the difference between the maximum value and the minimum value of the luminance integrated value is reduced by about 1/41.

Thus, for example, when an error correction code of LDPC (Low Density Parity Check) is added at an error rate of 10 ⁻³ , error correction was impossible in the past, but according to the present invention, error correction is possible Became.

Further, when the data area fluctuates due to noise or the optical system and the uncertainty of the characteristics of the hologram recording medium is large, when interleaving is performed with the optimum interleaving number “52,948”, as shown in FIG. Occasionally, the difference (B _max −B _min ) may become large (X in FIG. 11). In that case, the difference (B _max −B _min ) is set to 1 with respect to the maximum value of the difference by obtaining the number of interleaves in a region (Y in FIG. 11) in which the difference (B _max −B _min ) is small. / 3 to 1/2. Note that this method can be used when the SNR is relatively good because the difference (B _max −B _min ) is larger than the minimum difference.

1 arithmetic unit 10 interleave number arithmetic means (interleave number arithmetic unit)
11 Characteristic evaluation image writing means 12 Characteristic evaluation image reading means 13 Evaluation characteristic parameter generating means 13a Binarizing means 13b Circular shape specifying means 14 Binary image symbol string generating means 15 Temporary interleaved symbol integrating means 16 Interleave number searching means 20 Recording signal calculating means 21 Error correcting code adding means 22 Modulating means 23 Interleaving means 24 Data writing means 30 Reproduction signal calculating means 31 Data reading means 32 Deinterleaving means 33 Demodulating means 34 Error correcting means 100 Hologram recording apparatus 101 Laser light source 102 Shutter 103 Half-wave plate 104 PBS (polarization beam splitter)
105 Shutter 106 PBS (Polarized beam splitter)
107 SLM (Spatial Light Modulator)
108 FT (Fourier transform) lens 109 Half-wave plate 110 PBS (polarization beam splitter)
111 mirror 112 galvanometer mirror 113 relay lens 114 hologram recording medium 115 galvanometer mirror 116 relay lens 117 two-dimensional image sensor

Claims (5)

An interleave number calculation device that is provided in a hologram recording device that records interleaved digital data on a hologram recording medium by interference fringes between object light and reference light, and calculates an interleave number suitable for the hologram recording medium,
Characteristic evaluation image writing means for writing a pattern image including at least one white pixel for each symbol of a white image or an arbitrary modulation method to the hologram recording medium as a characteristic evaluation image of the hologram recording medium;
Reproduction of the hologram recording medium on which the characteristic evaluation image is recorded, and characteristic evaluation image reading means for reading a reproduction image of the characteristic evaluation image;
In the reproduced image read by the characteristic evaluation image reading unit, an evaluation characteristic parameter generating unit that generates a parameter specifying a circular shape that occurs on the reproduced image with a volume change of the hologram recording medium;
A binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation unit is generated, and a symbol string in which pixel values of the binary image are arranged in units of a predetermined number of symbols is generated. A value image symbol string generation means;
Temporary interleaved symbol integration means for reading out symbols for each temporary interleave number from the symbol sequence generated by the binary image symbol sequence generation means, and integrating the luminance for each error correction block having a preset number of symbols;
A temporary interleave number in which the difference between the maximum value and the minimum value of the luminance integrated value for each error correction block integrated by the temporary interleave symbol integrating means is equal to or less than a predetermined reference value is searched for, and the interleaving of the hologram recording medium is performed. An interleave number search means as a number;
An interleave number arithmetic apparatus comprising:   2. The interleaving number search unit according to claim 1, wherein the interleaving number that minimizes the difference between the maximum value and the minimum value of the luminance integrated values is the interleaving number of the hologram recording medium. Number arithmetic unit.   The interleaving number search means searches for the interleaving number of the hologram recording medium within a range of temporary interleaving numbers that are continuous when the difference between the maximum value and the minimum value of the luminance integrated values is equal to or less than a predetermined reference value. The interleave number arithmetic apparatus according to claim 1, wherein: In a hologram recording apparatus for recording interleaved digital data on a hologram recording medium by interference fringes between object light and reference light, in order to calculate an interleaving number suitable for the hologram recording medium, a computer is provided.
A characteristic evaluation image writing means for writing a pattern image including at least one white pixel for each symbol of a white image or an arbitrary modulation method onto the hologram recording medium as a characteristic evaluation image of the hologram recording medium;
Characteristic evaluation image reading means for reproducing the hologram recording medium on which the characteristic evaluation image is recorded and reading the reproduced image of the characteristic evaluation image;
In the reproduced image read by the characteristic evaluation image reading unit, an evaluation characteristic parameter generating unit that generates a parameter specifying a shape generated on the reproduced image in a circular shape with a volume change of the hologram recording medium,
A binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation unit is generated, and a symbol string in which pixel values of the binary image are arranged in units of a predetermined number of symbols is generated. Value image symbol sequence generation means,
Temporary interleave symbol integration means for reading out symbols for each temporary interleave number from the symbol sequence generated by the binary image symbol string generation means, and integrating the luminance for each error correction block having a preset number of symbols;
A temporary interleave number in which the difference between the maximum value and the minimum value of the luminance integrated value for each error correction block integrated by the temporary interleave symbol integrating means is equal to or less than a predetermined reference value is searched for, and the interleaving of the hologram recording medium is performed. Interleave number search means,
Interleave number calculation program to function as In a hologram recording apparatus for recording interleaved digital data on a hologram recording medium by interference fringes between object light and reference light, the interleave number calculating means for calculating the number of interleaves suitable for the hologram recording medium,
The interleave number calculation means includes:
Characteristic evaluation image writing means for writing a pattern image including at least one white pixel for each symbol of a white image or an arbitrary modulation method to the hologram recording medium as a characteristic evaluation image of the hologram recording medium;
Reproduction of the hologram recording medium on which the characteristic evaluation image is recorded, and characteristic evaluation image reading means for reading a reproduction image of the characteristic evaluation image;
In the reproduced image read by the characteristic evaluation image reading unit, an evaluation characteristic parameter generating unit that generates a parameter specifying a circular shape that occurs on the reproduced image with a volume change of the hologram recording medium;
A binary image having a shape specified by the parameter generated by the evaluation characteristic parameter generation unit is generated, and a symbol string in which pixel values of the binary image are arranged in units of a predetermined number of symbols is generated. A value image symbol string generation means;
Temporary interleaved symbol integration means for reading out symbols for each temporary interleave number from the symbol sequence generated by the binary image symbol sequence generation means, and integrating the luminance for each error correction block having a preset number of symbols;
A temporary interleave number in which the difference between the maximum value and the minimum value of the luminance integrated value for each error correction block integrated by the temporary interleave symbol integrating means is equal to or less than a predetermined reference value is searched for, and the interleaving of the hologram recording medium is performed. An interleave number search means as a number;
A hologram recording apparatus comprising:

Images