JP5997583B2 - Two-dimensional code decoding apparatus and program thereof, and hologram recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a two-dimensional code decoding apparatus and program for decoding a two-dimensional code used in a hologram recording / reproducing system, and a hologram recording / reproducing apparatus.

In a general hologram recording / reproducing system, two-dimensional page data (data composed of a plurality of two-dimensional codes) is exchanged with a modulation element and a light receiving element facing each other.
The two-dimensional code used in the hologram recording / reproducing system is a representation of one-dimensional original data on a two-dimensional plane. For example, a 2/4 code is generally used. This 2/4 code expresses 2-bit original data in 4 bits.

  Here, in the hologram recording / reproducing system, in order to obtain the highest recording density, the pixel size of the modulation element and the light receiving element are made the same, and the pixel of the modulation element and the pixel of the light receiving element are accurately positioned. The information (modulation data) recorded on the recording medium through the modulation element is used 100% when it is reproduced through the light receiving element. However, since commercially available modulation elements and light receiving elements are manufactured independently, pixel sizes are often uneven. In addition, it is not practical to newly create a modulation element and a light receiving element having the same pixel size because it requires enormous costs. Therefore, it is extremely difficult to align the pixel size of the modulation element and the pixel size of the light receiving element.

  For this reason, in a general hologram recording / reproducing system, it is possible to accurately read the two-dimensional code in the light receiving element by absorbing the misalignment of the pixel size between the modulation element and the light receiving element and the positional deviation due to the inclination of the light receiving element with respect to the modulation element. As described above, normally, a plurality of pixels are associated with one bit of modulation data. (See Patent Document 2).

  In this case, the recording density is reduced as compared with the case where one pixel of the light receiving element is associated with one bit of the modulation data. Therefore, it is expected to improve the recording density by transferring data from the modulation element to the light receiving element on a one-to-one basis.

JP 2006-65272 A Japanese Patent Laid-Open No. 2007-60098

Here, in a general hologram recording / reproducing system, a CCD (Charge Coupled Device) image sensor is mainly used as a light receiving element. The CCD image sensor is composed of, for example, 2048 × 2048 pixels.
In a general hologram recording / reproducing system, for example, markers are displayed at the four corners of the two-dimensional page data, and the modulation element and the light receiving element are positioned facing each other with reference to the markers at the four corners.

  However, even if the pixel sizes of the modulation element and the light receiving element are the same, if the modulation element and the light receiving element are positioned facing each other with reference to the marker, one pixel is formed in the vertical and horizontal directions of the light receiving element. To the extent, a displacement from the modulation element occurs. That is, in this case, even if the pixel sizes of the modulation element and the light receiving element are the same, the modulation element and the light receiving element are aligned in the upper left pixel, but the modulation element and the light receiving element are 1 in the lower right pixel. It will shift about a pixel. One pixel for 2048 pixels in the vertical and horizontal directions of the light receiving element is 0.028 degrees in angle, which is a very slight error. However, when such an error occurs, the modulation data cannot be transferred from the modulation element to the light receiving element by making the pixel of the modulation element and the pixel of the light receiving element face each other on a one-to-one basis. Further, when the pixel sizes of the modulation element and the light receiving element are not uniform, it is considered that the error is further increased. Therefore, data cannot be exchanged one-on-one.

  Therefore, an object of the present invention is to enable data exchange by allowing a modulation element and a light receiving element to be equivalently opposed to each other in a one-to-one manner regardless of the pixel sizes of the modulation element and the light receiving element.

  The invention according to claim 1, which has solved the above problem, encodes input recording data into a two-dimensional code, arranges the data on a modulation element, and records the recording data in a reproduction region of a light receiving element facing the modulation element. When the modulation data and the light receiving element have the same pixel size and no positional deviation from the reproduction data of the modulation data reproduced by the hologram recording / reproducing apparatus that receives and reproduces the modulation data of the data A two-dimensional code decoding apparatus that estimates and decodes the two-dimensional code to be reproduced in a reproduction region of the light receiving element, comprising a two-dimensional coordinate assignment unit, a conversion formula generation unit, a virtual reproduction data generation unit, and a decoding And a data estimation means.

  According to such a configuration, the two-dimensional code decoding apparatus uses the two-dimensional coordinate assigning unit to each pixel in the virtual modulation display area of the virtual modulation element in which the pattern of the two-dimensional code is arranged in the virtual modulation display area, and the virtual modulation element Each virtual modulation data virtually modulated in the virtual modulation display area is received and reproduced in the virtual reproduction display area, and each pixel in the virtual reproduction display area of the virtual light receiving element is virtually reproduced in a small area of the same size. The two-dimensional coordinates are assigned to each minute region.

  Here, the virtual modulation display area is an area necessary to virtually display one pattern of the two-dimensional code. For example, when the two-dimensional code is a 2/4 code, the virtual modulation element 4 pixels The area of minutes. The virtual reproduction display area is an area necessary for virtually reproducing the modulation data of one two-dimensional code. For example, when the two-dimensional code is 2/4 code, the virtual light receiving element 9 pixels It can be an area of minutes. Note that the number of pixels in the virtual reproduction display area can be changed as appropriate. The virtual modulation display area or virtual reproduction display area corresponds to the display area of the modulation element or the reproduction area of the light receiving element.

  As a result, the pixel in the reproduction area in the light receiving element and the pixel in the display area in the modulation element are virtually divided into minute areas corresponding to the respective virtual division numbers. By assigning a two-dimensional coordinate as an address for each micro area, the pixel in the reproduction area in the light receiving element and the pixel in the display area in the modulation element can be opposed to each other in micro area units.

  Further, the two-dimensional code decoding apparatus uses the conversion formula generation means to convert the two-dimensional coordinate system of each pixel of each virtual modulation display area to the corresponding virtual reproduction display area based on the positional deviation amount of the light receiving element with respect to the modulation element. A conversion formula for converting into a two-dimensional coordinate system of each pixel is generated.

  Further, the two-dimensional code decoding apparatus converts the two-dimensional coordinate system of each pixel of the virtual modulation element to each pixel of the corresponding virtual light receiving element by the conversion formula generated by the conversion formula generation unit by the virtual reproduction data generation unit. Each is converted into a two-dimensional coordinate system, and the virtual modulation data on the minute area of each pixel of the virtual modulation display area is assigned to the minute area of each pixel of the corresponding virtual reproduction display area, and the assigned virtual reproduction is performed. Virtual reproduction data is generated based on virtual modulation data in units of minute areas in the display area.

  The two-dimensional code decoding apparatus compares the plurality of virtual reproduction data generated by the decoded data estimation unit by the number of the two-dimensional code patterns by the virtual reproduction data generation unit and the reproduction data, respectively. Estimated that the closest virtual reproduction data is a two-dimensional code to be reproduced in the reproduction area of the light receiving element corresponding to the virtual reproduction data when the pixel size of the modulation element and the light receiving element are the same and there is no positional deviation. Then, the estimated two-dimensional code is decoded.

  Accordingly, the two-dimensional code decoding apparatus minutely reduces the pixels of the virtual modulation display area of the virtual modulation element corresponding to the display area of the modulation element and the pixels of the virtual reproduction display area of the virtual light reception element corresponding to the reproduction area of the light reception element. Dividing into regions, the pixels of the virtual modulation display area and the pixels of the virtual reproduction display area are opposed to each other in units of minute areas, and the pixels of the virtual modulation display area of the virtual modulation element are changed to the pixels of the virtual reproduction display area of the virtual light receiving element. The modulation data is transferred to the minute area of the virtual playback display area, and the modulation data is summed in units of pixels for all the pixels of the virtual playback display area. Are equivalent to each other in a one-to-one correspondence.

Further, in the two-dimensional code decoding apparatus according to 請 Motomeko 1, wherein the 2-dimensional coordinate allocation means, the size of the micro region, the virtual light-receiving element is divided in small areas, if a certain amount of positional deviation The output amplitude ratio with no deviation is set within a predetermined value according to the number of virtual divisions obtained in advance for each pixel of the virtual reproduction display area in the virtual light receiving element.

  According to such a configuration, the two-dimensional code decoding apparatus divides the pixel of the virtual light receiving element into minute regions, shifts by one minute region in the vertical and horizontal directions, and rotates the virtual light receiving device 1 by 45 degrees. The size of the minute region is set so as to reduce the deviation between the pixel output and the output of one pixel of the virtual light receiving element when there is no shift in the vertical and horizontal directions and there is no rotation.

Furthermore, the invention according to claim 2 is the two-dimensional code decoding device according to claim 1 , wherein the decoded data estimation means performs maximum likelihood decoding between a plurality of the virtual reproduction data and the reproduction data. And the two-dimensional code corresponding to the virtual reproduction data having the smallest code error rate is decoded.

  According to such a configuration, the two-dimensional code decoding apparatus performs strictest two-dimensional code most suitable as reproduction data by performing maximum likelihood decoding between a plurality of virtual reproduction data and reproduction data by the decoded data estimation unit. To estimate.

Further, according to the third aspect of the present invention, the modulation element and the light receiving element are made to face each other, the input recording data is encoded into a two-dimensional code, arranged on the modulation element, and received by the light receiving element. A hologram recording / reproducing apparatus for reproducing is configured to include a two-dimensional code decoding unit including a two-dimensional coordinate assigning unit, a conversion formula generating unit, a virtual reproduction data generating unit, and a decoded data estimating unit.

According to such a configuration, the hologram recording / reproducing apparatus has each pixel of the virtual modulation display area of the virtual modulation element in which the two-dimensional code pattern is arranged in the virtual modulation display area by the two-dimensional coordinate assignment unit of the two-dimensional code decoding apparatus. And each pixel in the virtual reproduction display area of the virtual light receiving element that virtually receives and reproduces the virtual modulation data virtually modulated in the virtual modulation display area of the virtual modulation element in the virtual reproduction display area, Virtual regions are divided into minute regions of the same size, and two-dimensional coordinates are assigned to the respective minute regions.
Here, the two-dimensional coordinate allocating means divides the virtual light receiving element into the minute regions so that the size of the minute region is within a predetermined value when the output amplitude ratio between the fixed displacement amount and the non-shifted amount is within a predetermined value. In this manner, each pixel in the virtual reproduction display area in the virtual light receiving element is set according to the virtual division number obtained in advance.
Further, the hologram recording / reproducing apparatus converts the two-dimensional coordinate system of each pixel of the virtual modulation element to each virtual light receiving element based on the positional deviation amount of the light receiving element with respect to the modulation element by the conversion formula generating means of the two-dimensional code decoding apparatus. A conversion expression for converting to a two-dimensional coordinate system of pixels is generated.

  Furthermore, the hologram recording / reproducing apparatus converts the two-dimensional coordinate system of each pixel of the virtual modulation element to the corresponding virtual light reception by the conversion expression generated by the conversion expression generating means by the virtual reproduction data generating means of the two-dimensional code decoding apparatus. Respectively converting the two-dimensional coordinate system of each pixel of the element, and assigning the virtual modulation data on the minute area of each pixel of the virtual modulation display area to the minute area of each pixel of the corresponding virtual reproduction display area, Virtual reproduction data is generated based on virtual modulation data in units of minute areas in the virtual reproduction display area allocated for each pixel.

The hologram recording and reproducing apparatus, the decoded data estimation means of the two-dimensional code decoding apparatus, a plurality of virtual reproduction data generated by the number of 2-dimensional code pattern with virtual reproduction data generating means, and reproducing the data of the modulated data The virtual reproduction data closest to the reproduction data is reproduced in the reproduction area of the light receiving element corresponding to the virtual reproduction data when the pixel size of the modulation element and the light receiving element are the same and there is no positional deviation. The estimated two-dimensional code is estimated, and the estimated two-dimensional code is decoded.

The invention described in claim 4 is a computer comprising hardware resources such as a CPU, a memory, and a hard disk, a conversion formula generating means of the two-dimensional code decoding apparatus according to claim 1, a virtual reproduction data generating means, The decoding data estimation means is realized as a two-dimensional code decoding program for cooperative operation.

According to the present invention, the following excellent effects can be obtained.
According to the first and fourth aspects of the present invention, the two-dimensional code decoding device (two-dimensional code decoding program) is a case where the modulation element and the light receiving element have a pixel size mismatch or a positional deviation. It is possible to accurately estimate and decode the two-dimensional code to be reproduced by the light receiving element. That is, it is possible to exchange data by making the pixels of the modulation element and the pixels of the light receiving element equivalently face each other.
Further, according to according to the invention described in claim 1 and 4, the two-dimensional code decoder, pixels of the pixel and the virtual light-receiving element of the virtual modulation device minute domains to divide the pixels of the virtual light-receiving element and the virtual modulation element pixels The number of virtual divisions obtained in advance for each pixel in the virtual reproduction display area of the virtual light receiving element is set so that the output amplitude ratio between the case of a certain amount of positional deviation and the case of no deviation falls within a predetermined value. By setting accordingly, the pixel of the modulation element and the pixel of the light receiving element can be made to face each other almost accurately.
According to the invention described in claim 2, the two-dimensional code decoding apparatus, it is possible to further improve the estimation accuracy of the two-dimensional code.
According to the third aspect of the present invention, the hologram recording / reproducing apparatus has a pixel of the modulation element and a pixel of the light receiving element even when the modulation element and the light receiving element have a pixel size mismatch or a positional deviation. Can be exchanged in a one-to-one manner equivalently.

It is a block diagram for demonstrating the structure of the hologram recording / reproducing apparatus which concerns on embodiment of this invention. It is a conceptual diagram which shows the structure of the light receiving element with which the photodetector of the hologram recording / reproducing apparatus which concerns on embodiment of this invention is provided, and has shown the magnitude | size of the light-receiving surface with respect to the pixel of a light receiving element. (A) is a conceptual diagram which shows the size of the modulation element with which the spatial light modulator of the hologram recording / reproducing apparatus which concerns on embodiment of this invention is provided, (b) is the hologram recording / reproducing apparatus which concerns on embodiment of this invention. It is a conceptual diagram which shows the size of the light receiving element with which this photodetector is equipped. It is a conceptual diagram which shows the position shift of the modulation element with which the spatial light modulator of the hologram recording / reproducing apparatus which concerns on embodiment of this invention is equipped, and the light receiving element with which a photodetector is provided. It is a block diagram for demonstrating the structure of the two-dimensional code decoding means of the hologram recording / reproducing apparatus which concerns on embodiment of this invention. (A) assigns two-dimensional coordinates associated with a predetermined number of virtual divisions to the pixels of the light receiving element by the two-dimensional code decoding means of the hologram recording / reproducing apparatus according to the embodiment of the present invention. (B) shows a virtually subdivided state in which a pixel of a modulation element is virtually subdivided into a microregion of the same size as the subregion of the pixel of the light receiving element. It is a conceptual diagram which shows a mode that the two-dimensional coordinate was allocated. (A) is the simulation result which shows the error at the time of changing the virtual division | segmentation number of the pixel of a light receiving element by the conversion type production | generation means of the two-dimensional code decoding means of the hologram recording / reproducing apparatus which concerns on embodiment of this invention. (B) is a graph of the simulation results of (a). It is a schematic diagram showing an outline of processing performed by the virtual reproduction data generation means and the decoded data estimation means of the two-dimensional code decoding means of the hologram recording / reproducing apparatus according to the embodiment of the present invention. It is a flowchart which shows operation | movement of the hologram recording / reproducing apparatus which concerns on embodiment of this invention. (A) is a conceptual diagram which shows a mode that two 2/4 codes | symbols are contained in four continuous pixels of a modulation element, (b) is 4 pixels in the case shown to (a). 6 is a table showing the calculation result of the occurrence probability of “1”. (A) is a conceptual diagram showing a state in which one 2/4 code is included in four consecutive pixels of a modulation element, and the front and back thereof are surrounded by other 2/4 codes, (b) ) Is a table showing the calculation result of the probability of occurrence of “1” out of the four pixels in the case shown in (a). (A)-(d) is a figure which shows the positional relationship of the modulation data whose peripheral data of 2/4 code | symbol are all "0", and the reproduction | regeneration area | region of a light receiving element. (A)-(d) is a figure which shows the positional relationship of the modulation data in case the peripheral data of 2/4 code | symbol has values other than "0", and the reproduction | regeneration area | region of a light receiving element. FIG. 10 shows a simulation result for confirming the influence of the peripheral data of the two-dimensional code on the estimation of the decoded data, and (a) shows the reproduction data of the modulated data in which the peripheral data of the 2/4 code is all “0”; The calculation result of the likelihood with virtual reproduction data is shown, (b) is the calculation result of the likelihood between the reproduction data of the modulation data in which the peripheral data of the 2/4 code has a value other than “0” and the virtual reproduction data. Indicates.

[Configuration of hologram recording / reproducing apparatus]
Hereinafter, the configuration of the hologram recording / reproducing apparatus of the present invention will be described with reference to FIG. In the following, a case where the recording data input to the hologram recording / reproducing apparatus is “00” will be described.
As shown in FIG. 1, a hologram recording / reproducing apparatus 1 receives a beam 1 and a beam 2 obtained by splitting an outgoing beam from a laser device (not shown) in advance with a beam splitter (not shown) or the like. An optical modulator 2, a lens 3, a lens 4, a photodetector 5, and a calculator 6 are provided. Further, the hologram recording / reproducing apparatus 1 includes a recording medium K that records the two-dimensional page data displayed on the spatial light modulator 2 as modulation data. Further, in the hologram recording / reproducing apparatus 1, the computer 6 includes a two-dimensional code decoding means 10.

  The spatial light modulator 2 is a two-dimensional code inputted from the outside on a modulation element 20 (see FIG. 3A) having a plurality of pixels 20a (see FIG. 3A) arranged two-dimensionally. By displaying the converted recording data, the beam 1 is two-dimensionally modulated to obtain modulation data of the recording data.

  Here, the two-dimensional code is a modulation code generally used in the hologram recording / reproducing system, and represents one-dimensional original data in a two-dimensional plane. In a general hologram recording / reproducing system, a 2/4 code, a 5/9 code, or the like is often used as a two-dimensional code. Here, the spatial light modulator 2 inputs the result obtained by modulating the 2-bit recording data “00” into 4-bit data using a 2/4 code in the external two-dimensional code encoder 40, and performs modulation. It is displayed on the element 20. The modulated data of the recording data is generated by transmitting or reflecting the beam 1 through the modulation element 20. The modulation data generated in this way is output to the lens 3.

  The modulation data of 2/4 code may be recorded on the recording medium K in a square shape by arranging two pixels in the vertical and horizontal directions, or may be recorded in a rectangular shape (straight line) by arranging four pixels in the vertical direction. You may record it freely. However, when data for 4 pixels are arranged in a square shape close to a circle and recorded on the recording medium K, since each pixel is close, deterioration in signal transmission is almost equal, which is advantageous from the viewpoint of signal equalization. Become. Here, it is assumed that the modulated data converted from the beam 1 by the spatial light modulator 2 is recorded on the recording medium K in a square shape by four pixels 20a arranged in two vertical and horizontal directions. .

  The lens 3 irradiates the recording medium K with the signal light modulated by the spatial light modulator 2 using the two-dimensional modulation code from the two-dimensional code encoder 40. Here, the lens 3 irradiates the recording medium K with the signal light modulated with the modulation data in the spatial light modulator 2. At the same time, the reference light is irradiated in an overlapping manner on the area of the recording medium K where the signal light is irradiated. Due to the signal light and the reference light, interference fringes (interference fringe patterns) are generated in the recording medium K, and the recording of the modulation data is completed by changing the refractive index of the recording medium K according to the light brightness / darkness pattern.

  The lens 4 emits, to the photodetector 5, reproduction light obtained by diffracting the reference light applied to the recorded area of the recording medium K during reproduction by a change in refractive index corresponding to the interference fringe pattern in the already recorded area. To do.

The light detector 5 reproduces the reproduction light emitted from the lens 4 in a reproduction region 33 (see FIG. 4) in which a plurality of pixels 30a (see FIG. 2 and FIG. 3 (b)) of the light receiving element 30 are arranged two-dimensionally. Light is received (photographed) and converted into data, and this reproduction data is output to the computer 6, and a CCD image sensor or a CMOS image sensor is used.
In addition, the photodetector 5 uses a marker (not shown) displayed at, for example, four corners of the reproduction light, and the modulation element 20 (see FIG. 3A) and the light receiving element 30 (see FIG. 3B). Is calculated by calculation. When the photodetector 5 receives the reproduction light of the modulation data obtained by the spatial light modulator 2 by the reproduction region 33 (see FIG. 4) of the light receiving element 30, the modulation element 20 and the light receiving element are received with respect to the modulation data. Reproduced data whose position is shifted by the amount of 30 positional shifts is obtained. The reproduced data and the positional deviation amount are output to the two-dimensional code decoding means 10 of the computer 6.

Here, the 2/4 code displayed on the four pixels 20a of the modulation element 20 is received and reproduced by the nine pixels 30a of the light receiving element 30 arranged in three vertical and horizontal directions. It shall be. Hereinafter, as shown in FIG. 4, an area including the four pixels 20 a of the modulation element 20 that displays the 2/4 code is referred to as a “display area 23”, and the light receiving element 30 that reproduces the 2/4 code. An area including nine pixels 30a may be referred to as a “reproduction area 33”.
As the spatial light modulator 2, the lens 3, the lens 4, and the photodetector 5, those similar to a general hologram recording / reproducing device can be used as appropriate.

As shown in FIG. 1, the computer 6 restores data by signal processing the reproduction data input from the photodetector 5 during reproduction.
The computer 6 extracts a position detection image group called a marker outside or inside the recording data to be displayed on the display area 23 of the modulation element 20 of the spatial light modulator 2 in order to extract a data area from the reproduction data and perform signal processing. A data area to be cut out is specified by displaying in advance. As described above, this marker is generated when the optical detector 5 makes the modulation element 20 (see FIG. 3A) and the light receiving element 30 (see FIGS. 2 and 3B) face each other. It is also used to calculate the amount of displacement.

  The computer 6 includes a two-dimensional code decoding means 10 as means for restoring data. The two-dimensional code decoding means 10 receives the reproduction data and the positional deviation amount from the photodetector 5, estimates a 2/4 code from the reproduction data and the positional deviation amount, decodes the estimated 2/4 code, The same 2-bit data (estimated decoded data) as the recording data input to the external two-dimensional code encoder 40 is generated.

  Here, prior to the description of the two-dimensional code decoding means 10, the modulation element 20 of the spatial light modulator 2 (see FIG. 3A) and the light receiving element 30 of the photodetector 5 (see FIGS. 2 and 3B). ).

[Structure of light receiving element]
First, the structure of the light receiving element 30 will be described with particular reference to FIG. In FIG. 2, the pixel 30a of the light receiving element 30 is illustrated in an enlarged manner.
As illustrated in FIG. 2, the pixel 30 a includes a light receiving surface 31 and a wiring portion 32 displayed along the outside of the light receiving surface 31. The aperture ratio indicating the ratio of the width of the light receiving surface 31 to the entire pixel 30a is expressed by an x-direction aperture ratio a and a y-direction aperture ratio b. The x direction aperture ratio a is the ratio of the length ax1 of one side of the light receiving surface 31 to the length x1 of one side of the entire pixel 30a in the x direction, and the y direction aperture ratio b is the pixel 30a in the y direction. This is the ratio of the length by1 of one side of the light receiving surface 31 to the length y1 of one side. Both the x-direction aperture ratio a and the y-direction aperture ratio b are usually about 0.8 to 0.9, but here, in order to simplify the explanation, the x-direction aperture ratio a and the y-direction aperture ratio b Both are set to 1.

  As shown in FIG. 2, the light receiving element 30 is configured by arranging a plurality of pixels 30a two-dimensionally in the x direction and the y direction. The light receiving element 30 is assumed to be a general CCD. Hereinafter, the pixel 30a refers to only the light receiving surface 31.

[Structure of modulation element]
Next, the structure of the modulation element 20 will be described with reference to FIG. In FIG. 3A, the pixel 20a of the modulation element 20 is illustrated in an enlarged manner.
As shown in FIG. 3A, the modulation element 20 is configured by displaying a plurality of pixels 20a two-dimensionally in the x direction and the y direction. Although not shown here, the pixel 20a includes a light receiving surface and a wiring portion in the same manner as the pixel 30a of the light receiving element 30. Hereinafter, the pixel 20a refers only to the light receiving surface.

[Relationship between size of modulation element and light receiving element]
Next, the size relationship between the modulation element 20 and the light receiving element 30 will be described with particular reference to FIGS. 3 (a) and 3 (b).
The hologram recording / reproducing apparatus 1 performs modulation data exchange, that is, data transmission, with the modulation element 20 and the light receiving element 30 facing each other. There are two methods of data transmission: a method that satisfies the sampling theorem and a sample value transmission method.
First, a method that satisfies the sampling theorem is that data transmission in the hologram recording / reproducing apparatus 1 is equivalent to sampling the two-dimensional code represented by the modulation element 20 in the light receiving element 30. FIG. The positional relationship between the pixel 20a of the modulation element 20 shown in FIG. 3A and the pixel 30a of the light receiving element 30 shown in FIG. 3B needs to satisfy the sampling theorem in both the vertical direction and the horizontal direction. That is, since the pixel size of the light receiving element 30 needs to be ½ or less in both the vertical direction and the horizontal direction of the pixel size of the modulation element 20, the number of pixels of the light receiving element 30 is at least four times the number of pixels of the modulation element 20. This is necessary. This directly reduces the recording density.

  Next, sample value transmission is a method of transmitting data by matching the pixel sizes of the modulation element 20 and the light receiving element 30. Although this method can save the number of pixels of the light receiving element 30 and there is no reduction in recording density, it is necessary to accurately match the pixel size and positional relationship between the modulation element 20 and the light receiving element 30. And cause the result of SNR degradation. Therefore, increasing the pixel size to increase the SNR leads to a decrease in recording density.

In the present invention, a sample value transmission method is employed to save the number of pixels of the light receiving element 30, and the pixel sizes of the modulation element 20 and the light receiving element 30 are selected to be substantially the same. The influence (error) was removed by signal processing, so that the SNR degradation was reduced and the reduction in recording density was suppressed.
In this description, the pixels of the light receiving element 30 are set to be square, and the pixels of the modulation element 20 are set to 1.1 times both vertically and horizontally.

[Position deviation between modulation element and light receiving element]
Next, the alignment of the modulation element 20 and the light receiving element 30 by the photodetector 5 and the calculation of the amount of displacement will be described with particular reference to FIG. Hereinafter, the coordinate system of the modulation element 20 (virtual modulation element 120) is represented as (x, y), and the coordinate system of the light receiving element 30 (virtual light receiving element 130) is represented as (x ′, y ′). To distinguish.
Here, the photodetector 5 indicates the relative positional relationship between the modulation element 20 and the light receiving element 30 by using markers (not shown) written at the four corners of the modulation data generated by the spatial light modulator 2. Use to adjust. This marker (not shown) is written in advance in the four corners of the two-dimensional page data displayed on the modulation element 20 of the spatial light modulator 2 by the computer 6 as described above.

  The photodetector 5 aligns the modulation element 20 and the light receiving element 30 with an error of about one pixel by aligning the positions of the modulation element 20 and the light receiving element 30 with reference to this marker (not shown). be able to. However, since the size of the pixel 20a of the modulation element 20 and the size of the pixel 30a of the light receiving element 30 are different from each other, even if one of four markers (not shown) is accurately aligned, the other three are The position will shift.

When the position of one marker (not shown) is accurately aligned, the photodetector 5 is, for example, 4 in the display area 23 of the modulation element 20 on which a 2/4 code is displayed as shown in FIG. of pieces of pixel 20a, the x-direction position of the upper left pixel 20a, determined by calculation horizontal shift amount x _a is the position displacement amount in the x direction of the upper left pixel 30a of the regeneration zone 33 of the light receiving element 30. Similarly, the photodetector 5 is the amount of displacement in the y direction of the upper left pixel 30a of the reproduction area 33 of the light receiving element 30 with respect to the y direction position of the upper left pixel 20a of the display area 23 of the modulation element 20. together by calculation the vertical movement amount y _a, determined by calculation the rotation angle θ is the slope of the upper left pixel 30a of the regeneration zone 33 of the light receiving element 30 to the upper-left pixel 20a in the display area 23 of the modulation element 20.

In this way, the positional deviation amount obtained, that is, horizontal shift amount x _a of the light receiving element 30 with respect to the modulation element _20, a vertical movement amount y _a, and, the rotation angle theta, the 2-dimensional code decoding means 10 of the computer 6 Is output. Note that it is not necessary for the photodetector 5 to determine the amount of positional deviation each time the reproduction light is incident from the lens 4, and it may be determined at an appropriate interval. When the reproduction light is incident from the lens 4 between the time of obtaining the positional deviation amount and the time of obtaining it next, the photodetector 5 can appropriately use the positional deviation amount obtained in advance.

[Configuration of two-dimensional code decoding means]
Hereinafter, the configuration of the two-dimensional code decoding means 10 will be described with reference to FIG. 5 in addition to FIGS.
As shown in FIG. 5, the two-dimensional code decoding unit 10 includes a two-dimensional coordinate assignment unit 11, a conversion formula generation unit 12, a virtual reproduction data generation unit 13, and a decoded data estimation unit 14.

As shown in FIG. 6, the two-dimensional coordinate assigning unit 11 divides each pixel 120 a in the virtual modulation display area 123 of the virtual modulation element 120 and each pixel 130 a in the virtual reproduction display area of the virtual light receiving element 130 into predetermined virtual divisions. Virtual division is performed according to the number n ² .

Here, the virtual modulation element 120 is obtained by virtually arranging a two-dimensional code pattern in the virtual modulation display area 123. Here, since the two-dimensional code is a 2/4 code, four types of virtual modulation elements 120 are assumed. The virtual modulation display area 123 is an area for virtually displaying each two-dimensional code pattern. Here, it corresponds to a 2 × 2 pixel area corresponding to the display area 23 (see FIG. 4) of the modulation element 20.
The virtual light receiving element 130 reproduces virtual modulation data virtually modulated by the virtual modulation display area 123 of the virtual modulation element 120 by the virtual reproduction display area 133. Here, four types of virtual modulation elements are used. Corresponding to the element 120, four virtual light receiving elements 130 are assumed. The virtual reproduction display area 133 is an area where virtual modulation data is virtually reproduced. Here, the virtual reproduction display area 133 indicates a 3 × 3 pixel area corresponding to the reproduction area 33 (see FIG. 4) of the light receiving element 30.

  The two-dimensional coordinate assigning means 11 assigns an (x, y) coordinate system to the virtual modulation display area 123 as shown in FIG. 6A, and the virtual light receiving element 130 is virtually shown in FIG. 6B. The (x ′, y ′) coordinate system is assigned to the reproduction display area 133.

  Here, since the light receiving element 30 outputs each pixel 30a corresponding to the average of the optical power entering the light receiving surface 31 (see FIG. 2), the size of the pixel 20a of the modulation element 20 and the size of the pixel 30a of the light receiving element 30 Are different from each other, the pixel 30a of the light receiving element 30 cannot be simply associated with an integer bit with respect to 1 bit (pixel 20a) of the modulation data represented by the modulation element 20. Therefore, here, each pixel 120a of the virtual modulation display area 123 of the virtual modulation element 120 and each pixel 130a of the virtual reproduction display area 133 of the virtual light receiving element 130 are virtually divided into minute areas of the same size, respectively. These are made to correspond in units of minute regions.

Here, as shown in FIG. 6 (b), since the virtual division number ^{n 2} of each pixel 130a of the virtual reproduction display area 133 of the virtual light-receiving element 130 is set to n = 10, 2-dimensional coordinate allocating means 11, virtual Each pixel 130a in the virtual reproduction display area 133 of the light receiving element 130 is virtually subdivided into 10 × 10 minute areas.
Further, as described above, the two-dimensional coordinate assigning means 11 is a minute area having the same size as each minute area obtained by virtually subdividing each pixel 120a in the virtual modulation display area 123 from each pixel 130a in the virtual reproduction display area 133. Virtually subdivide by area. Here, each pixel 120a in the virtual modulation display area 123 is set to be 1.1 times larger in size than each pixel 130a in the virtual reproduction display area 133.
Therefore, when each pixel 120a of the virtual modulation display area 123 is virtually subdivided into a micro area having the same size as the micro area where each pixel 130a of the virtual reproduction display area 133 is virtually subdivided, FIG. As shown in FIG. 4, the virtual region is virtually subdivided into 11 × 11 minute regions.

The following describes settings of a virtual division number ^{n 2} of each pixel 130a of the virtual reproduction display area 133 of the virtual light-receiving element 130. Here, in the case where one pixel is virtually divided into minute regions, the necessary virtual division number n ² is examined from the relationship between the virtual division number n ² and the output error.
It is assumed that the output of the minute area obtained by dividing one pixel is “0” or “1”, and the output of one pixel is obtained by dividing the total output of the virtual minute area by the number of virtual divisions. The influence of noise can be ignored.

  First, in the one-dimensional case, one pixel is virtually divided into several minute areas, and the output amplitude of one pixel when the position is shifted by one minute area and one pixel when there is no position shift. The amplitude ratio with the output amplitude is examined.

  For example, when one pixel is divided into two, when the position is shifted by one minute region (1/2 of one pixel), the output of one minute region is “1” and the output of the other minute region is “0”. Therefore, the output of one pixel is “0.5”. On the other hand, when one pixel is divided into two, when there is no position shift, the outputs of both cells are “1”, so the output of one pixel is “1”. Therefore, when one pixel is divided into two, the amplitude ratio between the output amplitude of one pixel when the position is shifted by one minute region and the output amplitude of one pixel when there is no position shift is “0.5”. It becomes. When this is expressed in decibels, it is -6.02 dB (= 20 log (0.5)).

  For example, when one pixel is divided into three, when the position is shifted by one minute region, the output of two cells in the pixel is “1” and the output of the remaining one cell is “0”. Therefore, the output of one pixel is “2/3”. Therefore, when one pixel is divided into three, the amplitude ratio between the output amplitude of one pixel when the position is shifted by one minute region and the output amplitude (= “1”) of one pixel when there is no position shift is , “2/3” (−3.52 dB). Hereinafter, the same calculation can be performed.

Next, this idea is extended to two dimensions. The pixels are assumed to be square, and the microregions are assumed to be square. Here, a simulation was performed on the amplitude ratio between the output amplitude when the position is shifted by one minute region in each of the horizontal and vertical directions and the output amplitude when there is no position shift in one pixel. FIG. 7A shows a table of simulation results, and FIG. 7B shows a graph of simulation results.
In general, it is said that a significant difference occurs when the amplitude ratio exceeds -3 dB. Therefore, from the graph shown in FIG. 7B, the number of n of the virtual division number n ² where the amplitude ratio is −3 dB is about 6.29. Since the virtual division number n ² is an integer, from the results described above, if n is 7 or more, it can be said that it is possible to suppress the amplitude ratio within -3 dB.

Here, since only the parallel movement of the virtual light receiving element 130 with respect to the virtual modulation element 120 in the horizontal direction and the vertical direction is considered, rotation is considered next. By rotating the virtual light receiving element 130 with respect to the virtual modulation element 120, the division interval by the minute region becomes longer. Here, since the minute region is assumed to be a square, the interval becomes the longest when tilted by 45 degrees, and the division interval is expanded by √2. Therefore, since it is necessary to multiply the number of virtual divisions by √2, the number of virtual divisions is required to be 9 or more (8.90≈6.29 × √2). Actually, the rotation angle θ is considered to be only a few (about several degrees). However, in the present embodiment, it is assumed that the rotation angle θ of the virtual light receiving element 130 with respect to the virtual modulation element 120 is 45 degrees. Furthermore, the virtual division number n ² of each pixel 130a in the virtual reproduction display area 133 of the virtual light receiving element 130 is set to n = 10 with a margin.

  Information on the two-dimensional coordinates assigned to each pixel 120 a of the virtual modulation element 120 and each pixel 130 a of the virtual light receiving element 130 in this way is output to the conversion formula generation unit 12. The two-dimensional coordinate assigning unit 11 can assign two-dimensional coordinates to each pixel 120a of the virtual modulation element 120 and each pixel 130a of the virtual light receiving element 130 at an appropriate timing.

Returning to FIG. 5 again, the conversion formula generating means 12 will be described.
Conversion formula generating means 12, the positional deviation amount of the light receiving element 30 with respect to the modulation device 20 determined by calculation by the light detector 5 (in this case, the horizontal shift amount x _a, the vertical movement amount y _a and the rotation angle theta: 4 2), and the two-dimensional coordinates of each pixel 120a of the virtual modulation display area 123 of the virtual modulation element 120 shown in FIG. A conversion formula for converting the system into the two-dimensional coordinate system of each pixel 130a in the virtual reproduction display area 133 of the corresponding virtual light receiving element 130 shown in FIG. 6B is generated.

First, the two-dimensional coordinate of each pixel 120a in the virtual modulation display area 123 of the virtual modulation element 120 is (x, y), and the two-dimensional coordinate of each pixel 130a in the virtual reproduction display area 133 of the virtual light receiving element 130 is (x ′ , Y ′), the two-dimensional coordinates (x ′, y ′) of each pixel 130 a of the virtual reproduction display area 133 of the virtual light receiving element 130 are the same as those of the pixels 120 a of the virtual modulation display area 123 of the virtual modulation element 120. two-dimensional coordinates (x, y), can be represented as shown with horizontal shift amount x _a, and the vertical shift amount y _a, in equation (1) follows by the rotation angle theta.

  When the formula (1) is combined into one matrix, the following formula (2) is obtained.

  In this way, the conversion formula generation unit 12 uses the two-dimensional coordinate system of each pixel 120a of the virtual modulation display area 123 of the virtual modulation element 120 based on the positional deviation amount, and the virtual reproduction display area of the corresponding virtual light receiving element 130. A conversion formula (formula (2)) for converting to the two-dimensional coordinate system of each pixel 130a of 133 is generated. The conversion formula generated here is output to the virtual reproduction data generation means 13. The conversion formula generation unit 12 may generate the conversion formula at the timing when the positional deviation amount is received from the photodetector 5, or generates the conversion formula at the timing when the conversion formula generation instruction is input from the outside. May be.

Based on the conversion formula generated by the conversion formula generation unit 12, the virtual reproduction data generation unit 13 sets the corresponding two-dimensional coordinate system of each pixel 120 a of the virtual modulation display area 123 including the plurality of virtual modulation elements 120. Are converted into a two-dimensional coordinate system of each pixel 130a in the virtual reproduction display area 133 composed of the virtual light receiving element 130. At the same time, the virtual reproduction data generation means 13 converts the virtual modulation data virtually modulated in the virtual modulation display area 123 of the plurality of virtual modulation elements 120 in the virtual reproduction display area 133 of the corresponding plurality of virtual light receiving elements 130. Virtual reproduction data when virtually received is generated.
Hereinafter, an outline of processing performed by the virtual reproduction data generation unit 13 and the decoded data estimation unit 14 of the two-dimensional code decoding unit 10 will be described with reference to FIG. 8 as appropriate.

  As shown in FIG. 5, the virtual reproduction data generation unit 13 inputs the conversion formula from the conversion formula generation unit 12, and sets the two-dimensional coordinate system of each pixel 120 a of the virtual modulation display area 123 of the virtual modulation element 120 to the above formula ( Based on the conversion formulas shown in 1) and (2), conversion into the two-dimensional coordinate system of each pixel 130a in the virtual reproduction display area 133 of the virtual light receiving element 130 is performed.

  Further, as shown in FIG. 8, the virtual reproduction data generation unit 13 assumes a plurality of virtual modulation elements 120 each displaying two-dimensional code patterns in the virtual modulation display area 123. Then, the virtual reproduction data generation means 13 converts the virtual modulation data on the two-dimensional coordinates of each pixel 120a in the virtual modulation display area 123 into the two-dimensional coordinates of each pixel 130a in the virtual reproduction display area 133 of the virtual light receiving element 130. By assigning each, virtual modulation data is virtually reproduced.

  As described above, since 2/4 code is assumed as the two-dimensional code here, four types of virtual modulation elements 120 in which four patterns of 2/4 code are arranged in the virtual modulation display area 123 are assumed. To do. Then, the virtual reproduction data generation means 13 uses the data on the minute area of each pixel 120a of the virtual modulation display area 123 of the four types of virtual modulation elements 120 as the data of each pixel 130a of the virtual reproduction display area 133 of the virtual light receiving element 130. Assign to each small area. As a result, the four types of virtual modulation data on the virtual modulation display area 123 of the four types of virtual modulation elements 120 are virtually reproduced in the virtual reproduction display area 133 of the virtual light receiving element 130, respectively.

  Here, since each pixel 130a of the virtual light receiving element 130 is virtually divided into 10 × 10 minute regions, the virtual reproduction data generating unit 13 performs virtual reproduction of the virtual light receiving element 130. Assume that the minute area data of each pixel 120a of the virtual modulation display area 123 of the corresponding virtual modulation element 120 is assigned to the minute area of each pixel 130a of the display area 133.

  Here, each pixel 123a of the virtual modulation display area 123 of the virtual modulation element 120 is virtually divided into 11 × 11 minute areas, and each pixel of the virtual modulation display area 123 of the virtual modulation element 120 is here. Since the data of the minute area 120a is “0” or “1”, “0” or “1” data is also assigned to each minute area of each pixel 130a of the virtual reproduction display area 133 of the virtual light receiving element 130. It is done. The output of each pixel 130a in the virtual reproduction display area 133 is obtained by dividing the total number of data “1” assigned to the minute area of each pixel 130a in the virtual reproduction display area 133 by the virtual division number.

Therefore, the virtual reproduction data generation means 13 counts the number of minute areas to which “1” is assigned for each pixel 130a in the virtual reproduction display area 133 of the virtual light receiving element 130, and this number is divided into the number of divisions of the pixel 130a (here, , 100) to calculate the output. The virtual reproduction data generating unit 13 generates virtual reproduction data that is an output of the entire virtual reproduction display area 133 of the virtual light receiving element 130 by performing this for nine pixels.
In this way, the virtual reproduction data generation unit 13 generates four types of virtual reproduction data that can be compared with the reproduction data output from the reproduction region 33 of the light receiving element 30 in the decoded data estimation unit 14 described later. For example, if virtual display data is displayed in a matrix, it becomes numerical data such as [0.5 0.7 0.1; 0.6 0.5 0.1; 0.1 0.2 0.1]. . Numerical data such as 1.2. The four types of virtual reproduction data generated here are output to the decoded data estimation means 14.

  As shown in FIG. 5, the decoded data estimation unit 14 includes a plurality of virtual reproduction data generated by the virtual reproduction data generation unit 13, reproduction data reproduced in the reproduction region 33 of the light receiving element 30 of the photodetector 5, and In contrast, the virtual reproduction data closest to the reproduction data is estimated to be reproduction data reproduced in the reproduction region 33 of the light receiving element 30 when there is no positional deviation between the modulation element 20 and the light receiving element 30. The decoded data estimation unit 14 further decodes the estimated two-dimensional code of the virtual reproduction data, converts the decoded two-dimensional code into 2-bit data, and generates estimated decoded data.

  Here, as shown in FIG. 8, the decoded data estimation means 14 generates reproduction data obtained by reproducing certain 2/4 code modulation data in the reproduction region 33 of the light receiving element 30 of the photodetector 5, and virtual reproduction data generation. The means 13 compares the four types of virtual reproduction data obtained by virtually reproducing the four types of virtual modulation data in the virtual reproduction display area 133 of the virtual light receiving element 130, respectively. The decoded data estimation unit 14 reproduces the virtual reproduction data closest to the reproduction data among the four types of virtual reproduction data in the reproduction area 33 when there is no positional deviation between the modulation element 20 and the light receiving element 30. It is estimated that the data should be reproduced.

In addition, the decoded data estimation unit 14 here estimates a two-dimensional code to be reproduced by the pixel 30a by maximum likelihood decoding.
Maximum likelihood decoding is a decoding method that estimates the most probable code by maximizing the likelihood function when the code is estimated and decoded.
The relationship between the maximum likelihood decoding and the code error rate of the decoded data can be expressed as follows.
According to Bayes' theorem, a relationship of “posterior probability∝likelihood function × prior probability” is established between the posterior probability of the code and the likelihood function.

  When the hologram recording / reproducing apparatus 1 is considered as a model, the prior probability corresponds to the probability of occurrence of a recording codeword, the likelihood function corresponds to the probability that the transmission path is not erroneous, and the posterior probability corresponds to the probability that the decoding code is not erroneous. Therefore, for a code with a fixed prior probability (a code generated with equal probability = random code), the posterior probability is highest when the likelihood is the highest, and the error rate of the two-dimensional code of the decoded data is minimized. . In the case of a hologram recording / reproducing apparatus, the modulation data is pre-randomized and converted to pseudo-random data, so that the prior probability is almost constant and the likelihood function is maximized, so that the code error rate of the decoded data is minimized. Become.

Here, the likelihood function between codes will be described. Let p _{i be} the element of the code P and q _i be the element of the code Q (p _i ∈P, q _i ∈Q). The likelihood regarding the code P and the code Q is a numerical value indicating the degree of similarity between P and Q, and a conditional probability indicating the probability that the transmission signal word _Pr is transmitted when the reception signal word _Qr is received. It is represented by When expressed in terms of information theory, the cross entropy of P and Q is a negative log likelihood. Here, the cross entropy is expressed by the following equation (3).

  In the maximum likelihood decoding, in addition to the cross-entropy as described above, a Cullback-Ribler distance, an Euclidean distance, or the like may be used. This Cullback-Riller distance has a close relationship with the cross entropy as shown in the following equation (4).

In Expression (4), H (P, Q) indicates the cross entropy of the code P and the code Q, H (P) indicates the entropy of the code P, and D _KL (P || Q) is the code P And the Cullback-Ribler distance of Q.

As shown in FIG. 8, the decoded data estimation means 14 calculates likelihoods for each of the reproduction data and the four types of virtual reproduction data as a result of the maximum likelihood decoding as described above, and performs the virtual reproduction with the highest likelihood. The data is estimated to be data to be reproduced in the reproduction area 33 of the light receiving element 30, the 2/4 code corresponding to the estimated virtual reproduction data is decoded, and the 2/4 code is converted into 2-bit data. Estimated decoded data is generated.
The hologram recording / reproducing apparatus 1 is configured as described above.

[Operation of hologram recording / reproducing apparatus]
Next, the operation of the hologram recording / reproducing apparatus 1 according to the embodiment of the present invention will be described with reference to FIG. 9 and FIGS. 1 to 8 as appropriate. Here, it is assumed that the hologram recording / reproducing apparatus 1 previously calculates the amount of positional deviation of the light receiving element 30 with respect to the modulation element 20 by the photodetector 5 and notifies the two-dimensional code decoding means 10 thereof.

  As shown in FIG. 9, the hologram recording / reproducing apparatus 1 inputs recording data “00” that is two-dimensionally encoded by the spatial light modulator 2 in the external two-dimensional code encoder 40, and this recording data “ A two-dimensional code corresponding to 00 ″ is displayed on the modulation element 20 in which a plurality of pixels 20a are arranged, and the beam 1 is transmitted in a two-dimensional code by transmitting or reflecting the display surface of the spatial light modulator 2. Modulation data of recording data “00” is generated by modulation (step S101).

Next, the hologram recording / reproducing apparatus 1 irradiates the recording medium K with the modulated data generated by the spatial light modulator 2 as signal light and irradiates the recording medium K with the beam 2 as reference light by the lens 3. (Step S102).
Further, the hologram recording / reproducing apparatus 1 records modulation data by using the recording medium K (step S103).
Subsequently, the hologram recording / reproducing apparatus 1 emits reproduction light to the photodetector 5 by the lens 4 (step S104).

  Further, the hologram recording / reproducing apparatus 1 receives the reproduction light emitted from the lens 4 by the photodetector 5 in the reproduction region 33 of the light receiving element 30 configured by arranging a plurality of pixels 30a in a two-dimensional manner ( Shooting), and output (reproduction data) of the reproduction area 33 is generated (step S105). The hologram recording / reproducing apparatus 1 outputs the generated reproduction data to the two-dimensional code decoding means 10 of the computer 6 by the photodetector 5.

Then, the hologram recording / reproducing apparatus 1 virtually subdivides the pixel 30a of the light receiving element 30 into a small area of the virtual division number n ² by the two-dimensional coordinate assigning means 11 of the two-dimensional code decoding means 10, and the virtual light receiving element 130. And the pixel 20a of the modulation element 20 is virtually subdivided into a micro area having the same size as the micro area obtained by subdividing the pixel 30a of the light receiving element 30 to generate the virtual modulation element 120 (step S106). In the present embodiment, each pixel 130a of the virtual light receiving element 130 is configured with a minute area of 100 (10 × 10), and each pixel 120a of the virtual modulation element 120 is configured with a minute area of 121 (11 × 11). . The hologram recording / reproducing apparatus 1 outputs the information of the allocated two-dimensional coordinates to the conversion formula generating unit 12 by the two-dimensional coordinate assigning unit 11 of the two-dimensional code decoding unit 10.

  Then, the hologram recording / reproducing apparatus 1 uses each of the virtual modulation elements 120 based on the positional deviation amount of the light receiving element 30 with respect to the modulation element 20 calculated in advance by the conversion formula generation means 12 of the two-dimensional code decoding means 10. A conversion formula for converting the two-dimensional coordinate system of the pixel 120a into the two-dimensional coordinate system of the corresponding pixel 130a of the virtual light receiving element 130 is generated (step S107). The hologram recording / reproducing apparatus 1 outputs the generated conversion expression to the virtual reproduction data generation means 13 by the conversion expression generation means 12 of the two-dimensional code decoding means 10.

Next, the hologram recording / reproducing apparatus 1 inputs a conversion formula from the conversion formula generation means 12 by the virtual reproduction data generation means 13 of the two-dimensional code decoding means 10, and each pixel of the virtual modulation element 120 according to this conversion formula. The two-dimensional coordinate system of 120 a is converted into the two-dimensional coordinate system of the corresponding pixel 130 a of the virtual light receiving element 130.
Subsequently, in the hologram recording / reproducing apparatus 1, four types of virtual modulation elements 120 in which four patterns of 2/4 codes are respectively arranged in the virtual modulation display area 123 by the virtual reproduction data generation unit 13 of the two-dimensional code decoding unit 10. For each virtual modulation element 120, “0” or “1” virtual modulation data on the minute area of each pixel 120 a in the virtual modulation display area 123 is converted into the minute value of the corresponding pixel 130 a in the virtual light receiving element 130. The area is allocated (step S108). That is, the virtual modulation data virtually displayed by the four types of virtual modulation elements 120 is virtually received by the corresponding four virtual light receiving elements 130, respectively.

  Further, subsequently, the hologram recording / reproducing apparatus 1 is assigned to each pixel 130a by the virtual reproduction data generating unit 13 of the two-dimensional code decoding unit 10 for each pixel 130a of the virtual reproduction display area 133 of the virtual light receiving element 130. The number of “1” is counted, and the total number of “1” is divided by the total number of minute areas, that is, the number of divisions (here, 100 (10 × 10)), and each pixel 130a of the virtual reproduction display area 133 is obtained. Find the output of. Then, by calculating outputs for the number of pixels 130a constituting the virtual reproduction display area 133 (here, nine), virtual reproduction data that is an output of the virtual reproduction display area 133 is generated (step S109). This is performed for all four virtual light receiving elements 130. Then, the hologram recording / reproducing apparatus 1 outputs the four types of virtual reproduction data generated by the virtual reproduction data generation unit 13 of the two-dimensional code decoding unit 10 to the decoded data estimation unit 14.

  Then, the hologram recording / reproducing apparatus 1 inputs four types of virtual reproduction data from the virtual reproduction data generation unit 13 and the reproduction data from the photodetector 5 by the decoded data estimation unit 14 of the two-dimensional code decoding unit 10. To do. Then, the hologram recording / reproducing apparatus 1 compares the four types of virtual reproduction data and reproduction data with the decoded data estimation unit 14 of the two-dimensional code decoding unit 10. Further, the hologram recording / reproducing apparatus 1 corresponds to the virtual reproduction data closest to the reproduction data as a result of comparing the four types of virtual reproduction data and the reproduction data by the decoded data estimation means 14 of the two-dimensional code decoding means 10. The two-dimensional code is estimated to be data to be reproduced in the reproduction area 33 of the light receiving element 30 that has reproduced the reproduction data (step S110).

Then, the hologram recording / reproducing apparatus 1 decodes the estimated two-dimensional code by the decoded data estimation unit 14 of the two-dimensional code decoding unit 10, and the decoded two-dimensional code is input to the spatial light modulator 2 and the recorded data It converts into the same 2-bit data, and presumed decoding data are produced | generated (step S111).
The hologram recording / reproducing apparatus 1 operates as described above.

  According to the hologram recording / reproducing apparatus 1 described above, each pixel of the virtual modulation display area 123 of the virtual modulation element 120 corresponding to the display area 23 of the modulation element 20 of the spatial light modulator 2 is obtained by the two-dimensional code decoding means 10. 120a and each pixel 130a of the virtual reproduction display area 133 of the virtual light receiving element 130 corresponding to the reproduction area 33 of the light receiving element 30 of the photodetector 5 can be made to correspond on a two-dimensional coordinate. Further, according to the hologram recording / reproducing apparatus 1, the reproduction data reproduced in the reproduction area 33 of the light receiving element 30 and the virtual reproduction display area 133 of the virtual light receiving element 130 are virtually reproduced by the two-dimensional code decoding means 10 4. By comparing the types of virtual reproduction data with each other, when the pixel size of the modulation element 20 and the light receiving element 30 are the same and there is no positional deviation, the reproduction area 33 of the light receiving element 30 should be originally reproduced. A dimensional code can be estimated. Therefore, according to the hologram recording / reproducing apparatus 1, by providing the two-dimensional code decoding means 10, the pixel 20a of the modulation element 20 and the pixel 30a of the light receiving element 30 are equivalently opposed one-on-one, and data is exchanged. Can be performed.

  Further, the hologram recording / reproducing apparatus 1 reproduces the reproduction actually performed in the reproduction area 33 of the light receiving element 30 when the two-dimensional code decoding means 10 estimates the two-dimensional code to be reproduced in the reproduction area 33 of the light receiving element 30. Since maximum likelihood decoding is performed between the data and the four types of virtual reproduction data virtually reproduced in the virtual reproduction display area 133 of the virtual light receiving element 130, a two-dimensional code to be reproduced in the reproduction area 33 of the light receiving element 30 is obtained. Can be estimated more accurately.

[simulation]
In the hologram recording / reproducing apparatus 1 according to the present embodiment described above, as shown in FIG. 4, the light receiving element 30 of the photodetector 5 is inclined by the rotation angle θ with respect to the modulation element 20 of the spatial light modulator 2. ing. In order to absorb such a displacement, the 2/4 code displayed in the 2 × 2 pixel display area 23 of the modulation element 20 is received and reproduced by the 3 × 3 pixel reproduction area 33 of the light receiving element 30. Yes. Since the reproduction area 33 of the light receiving element 30 is larger than the display area 23 of the modulation element 20 in this way, not only the 2/4 code displayed on the display area 23 of the modulation element 20 but also its peripheral data is received. Become.

Therefore, the reproduction data of the modulation data including the peripheral data of 2/4 code reproduced in the reproduction area 33 of the light receiving element 30 and the virtual reproduction / reproduction data in the virtual reproduction display area 133 of the virtual light receiving element 130 When the 2/4 code is estimated based on the likelihood of the virtual reproduction data of all the patterns of the 4 codes, the influence of the surrounding data may appear in the estimation result. Therefore, it was decided to perform a simulation to investigate the influence of the peripheral data appearing in the estimation result of the two-dimensional code on the likelihood.
Specifically, the display area 23 of the modulation element 20 is set to 4 × 4 pixels including not only the display area of data corresponding to 2/4 code (2 × 2 data) but also peripheral data. A simulation was performed in which 2/4 codes were mapped to the 3 × 3 reproduction area 33 of the light receiving element and the 2/4 code was estimated from the data of the reproduction area 33 of the light receiving element 30.

Here, when the continuous region 24 including four pixels continuous in the horizontal direction on the modulation element 20 is cut out, the modulation element 20 converts the 2/4 code into 2 in the continuous region 24 as shown in FIG. 11 and a case where the modulation element 20 includes one 2/4 code in the continuous region 24 and is surrounded by another 2/4 code before and after that, as shown in FIG. Conceivable.
As described above, in the 2/4 code, in 2 × 2 pixels adjacent to each other, one pixel is ON “1”, the remaining three pixels are OFF “0”, and 2-bit data is four pixels. It is the code | symbol expressed by. Therefore, four “1” s do not continue in the continuous area 24 due to the nature of the 2/4 code. That is, as shown in FIG. 10A, when two 2/4 codes are included in the continuous region 24, “1” in any of four pixels is one of 0 to 2. Further, as shown in FIG. 11A, when one 2/4 code is included in the continuous area 24 and the front and back thereof are surrounded by other 2/4 codes, “1” is 0 in 4 pixels. It will be one of ~ 3. Therefore, the probability of occurrence of “1” in the cases as shown in FIGS. 10 (a) and 11 (a) is obtained by calculation, and the result is shown in Table 1 of FIG. 10 (b) and FIG. 11 (b). These are shown in Table 2, respectively.

  As shown in Table 1 of FIG. 10B, when the modulation element 20 includes two 2/4 codes in the continuous region 24, the probability that one pixel in four pixels in the continuous region 24 is “1” is , 50 percent (1/2), and the probability that 0 or 2 of the 4 pixels in the continuous region 24 is “1” was confirmed to be 25 (1/4) percent.

  On the other hand, as shown in Table 2 of FIG. 11B, when the modulation element 20 includes one 2/4 code in the continuous region 24 and is surrounded by another 2/4 code before and after that, it is continuous. The probability that 1 out of 4 pixels in the region 24 is “1” is about 50 percent (30/64), and the probability that 0 or 2 pixels in the continuous region 24 are “1” is about 24. The percentage (18/64 or 14/64) was confirmed, and the probability that 3 out of 4 pixels in the continuous region 24 was “1” was confirmed to be about 3 percent (2/64).

Next, on the modulation element 20, the light receiving element 30 for each of the case where the peripheral data of the display area 23 of the 2/4 code is all “0” and the case where the peripheral data of the display area 23 includes “1”. The likelihood of the reproduction data reproduced in the reproduction area 33 and the virtual reproduction data was obtained by calculation.
First, in the case where all the peripheral data of the 2/4 code display area 23 on the modulation element 20 is “0”, the data shown in FIG. 12 was used. In FIG. 12, it is assumed that the data of 4 × 4 pixels on the virtual modulation element 120 is [0000; 0100; 0000; 0000]. In this data, the second and third numbers “10” in the two items “0100” and the second and third numbers “00” in the three items “0000” represent the 2/4 code.

  12A to 12D, 2 × 2 pixels within the thick frame of the modulation element 20 are the display area 23. In FIG. 12A, a 2/4 code indicating “00” is displayed in the display area 23, and a 2/4 code indicating “01” is displayed in the display area 23. (C) assumes that a 2/4 code indicating “10” is displayed in the display area 23, and (d) indicates that a 2/4 code indicating “11” is displayed in the display area 23. . In FIGS. 12A to 12D, it is assumed that all the peripheral data of the display area 23 is “0”.

Next, in the case where “1” is included in the peripheral data of the display area 23 of the 2/4 code on the modulation element 20, the data shown in FIG. 13 was used. Here, in consideration of the characteristics of the 2/4 code, the peripheral data is set such that any one of 0 to 3 “1” is included in four pixels continuously in the horizontal direction.
That is, in FIG. 13, the data of 4 × 4 pixels on the modulation element 20 is [0010; 1101; 0000; 1000]. In this data, the second and third numbers “10” in the two items “1101” and the second and third numbers “00” in the three items “0000” represent the 2/4 code.

  13A to 13D, 2 × 2 pixels within the thick frame of the modulation element 20 are the display area 23. In FIG. 13A, a 2/4 code indicating “00” is displayed in the display area 23, and in FIG. 13B, a 2/4 code indicating “01” is displayed in the display area 23, (C) assumes that a 2/4 code indicating “10” is displayed in the display area 23, and (d) indicates that a 2/4 code indicating “11” is displayed in the display area 23. . Further, in FIGS. 13A to 13D, the condition that the probability of “1” in four pixels continuous to the peripheral data of the display area 23 is the condition described with reference to FIGS. 10B and 11B. “1” is arranged so as to satisfy.

In each case shown in FIGS. 12 and 13, the results of the likelihood calculation are shown in Table 3 in FIG. 14A and Table 4 in FIG. 14B, respectively. The likelihood was calculated by the above equation (3) and normalized by the maximum value. The parameter is the horizontal shift amount x _a, in addition to the vertical movement amount y _a and the rotation angle theta, added a SNR to approximate to the actual situation. Here, the horizontal shift amount x _a and the vertical shift amount y _a, a minute area unit, in the present simulation were set in tenths of pixel width of the light receiving element 30.

  As shown in FIGS. 12A to 12D, when the recording data is “00” and all the peripheral data is “0”, the positional deviation amount and the SNR are changed, and the likelihood for each recording data is changed. The results of calculating the degrees are shown in Table 1 of FIG. In any of the results, when the data is “00”, the likelihood is the highest, and it was confirmed that the data “00” is selected as the estimated value.

  Also, as shown in FIGS. 13A to 13D, when the recording data is “00” and the surrounding data includes “1”, the amount of positional deviation and the SNR are changed to change each recording data. The result of calculating the likelihood for is shown in Table 2 of FIG. Although the ratio is lower than the result in the case where all the peripheral data shown in Table 1 of FIG. 14A are all “0”, the likelihood is obtained when all the results are data “00”. It was confirmed that data “00” was selected as the estimated value.

  From the above, when the 2/4 code decoding means 10 of the hologram recording / reproducing apparatus 1 according to the first embodiment of the present invention estimates 2/4 code from the reproduced data, the reproduced data reproduced in the reproduction area 33 of the light receiving element 30. However, even if the peripheral data of the display area 23 of the modulation element 20 is included, it has been confirmed that the estimation result of the 2/4 code is hardly affected.

  As mentioned above, although embodiment of this invention was described, the meaning of this invention is not limited to these description, and should be interpreted widely based on description of a claim. Needless to say, various changes and modifications based on these descriptions are also included in the spirit of the present invention.

  For example, in the above-described embodiment, the two-dimensional code decoding means 10 included in the hologram recording / reproducing apparatus 1 may be configured as a two-dimensional code decoding apparatus including each means of the two-dimensional code decoding means 10. Thus, by adopting an independent configuration as a two-dimensional code decoding device, for example, a hologram including the spatial light modulator 2, the lens 3, the recording medium K, the lens 4, and the photodetector 5 on the ground. A recording / reproducing device is provided. On the other hand, a two-dimensional code decoding device is provided on a marine vessel or the like, and reproduction data is transferred from the photodetector 5 of the hologram recording / reproducing device to the two-dimensional code decoding device via a space or an optical fiber. It becomes possible to transmit.

  Further, for example, the two-dimensional code decoding means 10 is a computer having hardware resources such as a CPU, a memory and a hard disk, a two-dimensional coordinate assigning means 11, a conversion formula generating means 12, a virtual reproduction data generating means 13, and a decoding. It is also possible to use a program (two-dimensional code decoding program) in which the processing in the data estimation means 14 is described so as to be executable. In this case, the two-dimensional code decoding program has the same effect as the corresponding two-dimensional code decoding means 10. This two-dimensional code decoding program may be distributed via a network, or may be distributed by writing in a recording medium such as a CD-ROM or a flash memory.

  Further, for example, the two-dimensional code decoding program may be implemented as hardware by using a general-purpose computing on graphics processing unit (GPGPU), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like. In this way, the calculation can be executed at a practical speed.

DESCRIPTION OF SYMBOLS 1 Hologram recording / reproducing apparatus 2 Spatial light modulator 3 Lens 4 Lens 5 Photodetector 10 Two-dimensional code decoding means 11 Two-dimensional coordinate allocation means 12 Conversion formula production | generation means 13 Virtual reproduction data generation means 14 Decoded data estimation means 20 Modulation element 23 Display area 30 Light receiving element 33 Reproduction area 120 Virtual modulation element 123 Virtual modulation display area 130 Virtual light reception element 133 Virtual reproduction display area

Claims (4)

In a hologram recording / reproducing apparatus that encodes input recording data into a two-dimensional code, arranges it on a modulation element, and receives and reproduces the modulation data of the recording data in a reproduction area of a light receiving element facing the modulation element The two-dimensional code to be reproduced in the reproduction region of the light receiving element when the pixel size of the modulation element and the light receiving element is the same and there is no positional deviation from the reproduced data of the modulated data reproduced. A two-dimensional code decoding apparatus that estimates and decodes,
Each pixel of the virtual modulation element when all the patterns of the two-dimensional code are virtually arranged in the virtual modulation display area, and virtual modulation data virtually modulated in the virtual modulation display area of the virtual modulation element When the virtual light receiving display area is virtually received and reproduced, each pixel of the virtual light receiving display area of the virtual light receiving element is virtually divided by a micro area of the same size and is divided for each micro area. Two-dimensional coordinate assigning means for assigning two-dimensional coordinates;
Based on the amount of positional deviation of the light receiving element with respect to the modulation element, the two- dimensional coordinate system of each pixel of each virtual modulation display area assigned by the two-dimensional coordinate assignment unit is assigned to the corresponding virtual reproduction display area. Conversion equation generating means for generating a conversion equation for conversion into a two- dimensional coordinate system of each pixel;
The two- dimensional coordinate system of each pixel of the virtual modulation display area of the virtual modulation element is converted into each pixel of the virtual reproduction display area of the corresponding virtual light receiving element by the conversion formula generated by the conversion formula generation means. And the virtual modulation data on the minute area of each pixel of the virtual modulation display area is assigned to the minute area of each pixel of the corresponding virtual reproduction display area, respectively. Virtual reproduction data generation means for generating virtual reproduction data based on the virtual modulation data assigned to the minute area of each pixel of the virtual reproduction display area;
The virtual reproduction data generated by the virtual reproduction data generation means by the number of patterns of the two-dimensional code is compared with the reproduction data, and the virtual reproduction data closest to the reproduction data is compared with the modulation element. When the pixel size is the same as that of the light receiving element and there is no positional deviation, the two-dimensional code to be reproduced in the reproduction area of the light receiving element corresponding to the virtual reproduction data is estimated and estimated e Bei and a decoded data estimation means for decoding the 2-dimensional code,
The two-dimensional coordinate allocating unit divides the virtual light receiving element into small regions so that the size of the minute region is within a predetermined value when an output amplitude ratio between a certain amount of positional deviation and no deviation is obtained. The two-dimensional code decoding apparatus characterized by setting according to the virtual division | segmentation number calculated | required beforehand about each pixel of the said virtual reproduction display area in the said virtual light receiving element . The decoded data estimation means includes:
A plurality of the virtual reproduction data, performs maximum likelihood decoding between said reproduction data, in claim 1, characterized in that decoding the 2-dimensional code a code error rate corresponding to the smallest the virtual reproduction data The two-dimensional code decoding apparatus described. A hologram recording / reproducing apparatus that encodes input recording data into a two-dimensional code, arranges it on a modulation element, and receives and reproduces the modulation data of the recording data in a reproduction area of a light receiving element facing the modulation element. There,
Each pixel of the virtual modulation element when all the patterns of the two-dimensional code are virtually arranged in the virtual modulation display area, and virtual modulation data virtually modulated in the virtual modulation display area of the virtual modulation element When the virtual light receiving display area is virtually received and reproduced, each pixel of the virtual light receiving display area of the virtual light receiving element is virtually divided by a micro area of the same size and is divided for each micro area. Two-dimensional coordinate assigning means for assigning two-dimensional coordinates;
Based on the amount of positional deviation of the light receiving element with respect to the modulation element, the two- dimensional coordinate system of each pixel of each virtual modulation display area assigned by the two-dimensional coordinate assignment unit is assigned to the corresponding virtual reproduction display area. Conversion equation generating means for generating a conversion equation for conversion into a two- dimensional coordinate system of each pixel;
The two- dimensional coordinate system of each pixel of the virtual modulation display area of the virtual modulation element is converted into each pixel of the virtual reproduction display area of the corresponding virtual light receiving element by the conversion formula generated by the conversion formula generation means. And the virtual modulation data on the minute area of each pixel of the virtual modulation display area is assigned to the minute area of each pixel of the corresponding virtual reproduction display area, respectively. Virtual reproduction data generation means for generating virtual reproduction data based on the virtual modulation data assigned to the minute area of each pixel of the virtual reproduction display area;
The virtual reproduction data generated by the number of the two-dimensional code patterns by the virtual reproduction data generation means and the reproduction data of the modulation data are respectively compared, and the virtual reproduction data closest to the reproduction data is When the pixel size of the modulation element and the light receiving element are the same and there is no positional deviation, it is estimated that the two-dimensional code is to be reproduced in the reproduction area of the light receiving element corresponding to the virtual reproduction data. , e Bei decoded data estimating means for decoding the estimated the two-dimensional code, a,
The two-dimensional coordinate allocating unit divides the virtual light receiving element into small regions so that the size of the minute region is within a predetermined value when an output amplitude ratio between a certain amount of positional deviation and no deviation is obtained. The hologram recording / reproducing apparatus, wherein each pixel of the virtual reproduction display area in the virtual light receiving element is set according to a virtual division number obtained in advance . In a hologram recording / reproducing apparatus that encodes input recording data into a two-dimensional code, arranges it on a modulation element, and receives and reproduces the modulation data of the recording data in a reproduction area of a light receiving element facing the modulation element The two-dimensional code to be reproduced in the reproduction region of the light receiving element when the pixel size of the modulation element and the light receiving element is the same and there is no positional deviation from the reproduced data of the modulated data reproduced. To estimate and decode the computer,
Each pixel of the virtual modulation element when all the patterns of the two-dimensional code are virtually arranged in the virtual modulation display area, and virtual modulation data virtually modulated in the virtual modulation display area of the virtual modulation element When the virtual light receiving display area is virtually received and reproduced, each pixel of the virtual light receiving display area of the virtual light receiving element is virtually divided by a micro area of the same size and is divided for each micro area. 2D coordinate assigning means for assigning 2D coordinates,
Based on the amount of positional deviation of the light receiving element with respect to the modulation element, the two- dimensional coordinate system of each pixel of each virtual modulation display area assigned by the two-dimensional coordinate assignment unit is assigned to the corresponding virtual reproduction display area. Conversion expression generation means for generating a conversion expression for conversion into a two- dimensional coordinate system of each pixel;
The two- dimensional coordinate system of each pixel of the virtual modulation display area of the virtual modulation element is converted into each pixel of the virtual reproduction display area of the corresponding virtual light receiving element by the conversion formula generated by the conversion formula generation means. And the virtual modulation data on the minute area of each pixel of the virtual modulation display area is assigned to the minute area of each pixel of the corresponding virtual reproduction display area, respectively. Virtual reproduction data generating means for generating virtual reproduction data based on the virtual modulation data allocated to the minute area of each pixel of the virtual reproduction display area;
The virtual reproduction data generated by the virtual reproduction data generation means by the number of patterns of the two-dimensional code is compared with the reproduction data, and the virtual reproduction data closest to the reproduction data is compared with the modulation element. When the pixel size is the same as that of the light receiving element and there is no positional deviation, the two-dimensional code to be reproduced in the reproduction area of the light receiving element corresponding to the virtual reproduction data is estimated and estimated A two-dimensional code decoding program for functioning as decoded data estimating means for decoding the two-dimensional code ,
The two-dimensional coordinate allocating unit divides the virtual light receiving element into small regions so that the size of the minute region is within a predetermined value when an output amplitude ratio between a certain amount of positional deviation and no deviation is obtained. A two-dimensional code decoding program characterized in that each pixel of the virtual reproduction display area in the virtual light receiving element is set according to the virtual division number obtained in advance.

Images