WO2015097837A1

WO2015097837A1 - Marker pattern generation method, information recording medium, information reconstruction method, and information recording medium reconstruction device

Info

Publication number: WO2015097837A1
Application number: PCT/JP2013/085031
Authority: WO
Inventors: 純也飯塚
Original assignee: 日立コンシューマエレクトロニクス株式会社
Priority date: 2013-12-27
Filing date: 2013-12-27
Publication date: 2015-07-02

Abstract

The present invention addresses the problem of providing, in reconstruction processing for holographic memory, marker patterns for which sub-pixel position detection is possible even in a data page for which the amount of inter-pixel interference is significant. As an example of means which resolves the problem, a marker pattern generation method is provided with an intermediate pattern generation step and a magnification pattern generation step, wherein: in the intermediate pattern generation step, an intermediate pattern is generated so that, for the intermediate pattern, the covariance value is 0 between the intermediate pattern central portion, which excludes an outer edge comprising pixels adjacent to the boundary of the same, and a partial region, which is inscribed in the boundary of the intermediate pattern; and in the magnification pattern generation step, each recording pixel of the intermediate pattern is substituted with a recording unit in which a plurality of recording pixels of the same polarity as the first-mentioned recording pixel are arrayed in the row-direction and/or the column-direction.

Description

Marker pattern generation method, information recording medium, information reproducing method, and information recording medium reproducing apparatus

The present invention relates to a marker pattern generation method, an information recording medium, an information reproduction method, and an information recording medium reproduction apparatus.

As a hologram reproduction technique, there is JP-T-2008-536158 (Patent Document 1). According to this publication, “a predetermined spare block is allocated over each data page, and each spare block includes a known pixel pattern, an area of the data page, and a predetermined spare block; By determining the data page position error by calculating the best match between and correcting the data pixels according to the corresponding data page position error at the detector. A process for making it possible to distinguish a two-dimensional data page is described.

Also, Japanese Patent Application Laid-Open No. 2010-003358 (Patent Document 2) describes a technique that can reduce the aperture size of the filter disposed in the beam waist and improve the recording density.

Special table 2008-536158 JP 2010-003358 A

In Patent Document 1, as an example of a spare block suitable for determining a position error of a data page, a covariance value between a specific subblock in the spare block and a plurality of other subblocks in contact with the end is 0. The pattern that becomes is described. In addition, regarding the method of determining the position error of the data page using the spare block, the “integer position that most closely matches the spare block pattern” is obtained by covariance calculation, and then the “adjacent value” is linearly determined. An example realized by “interpolating” is described.

On the other hand, when the technique described in Patent Document 2 is applied, the detection image of a single recording pixel detected at the time of reproduction is enlarged due to a reduction in the aperture size of the filter, and inter-pixel interference increases. At this time, when the spare block described in Patent Document 1 was applied, it was found that the covariance value at the integer position that most strongly matches the spare block pattern at the time of detection and the adjacent value thereof approach each other. That is, when noise or the like is added, there is a risk that the “integer position that most closely matches the spare block pattern” is erroneously determined as an adjacent position, and the position error cannot be obtained correctly.

Therefore, an object of the present application is to realize a spare block capable of determining a position error even from a detection image in which inter-pixel interference is increased, and to realize position error determination using the spare block.

For example, the above-described problem is to replace each recording pixel of the intermediate pattern with a recording unit in which recording pixels having the same polarity as each recording pixel are arranged in a number of recording pixels in at least one of the row direction and the column direction. It is solved by.

According to the present invention, it is possible to determine a position error more accurately even from a detection image in which inter-pixel interference is increased.

Flow chart representing an example of marker pattern generation processing Schematic diagram showing an embodiment of an optical information recording / reproducing apparatus Schematic showing an embodiment of a pickup in an optical information recording / reproducing apparatus Schematic showing an embodiment of a pickup in an optical information recording / reproducing apparatus Schematic showing an embodiment of a pickup in an optical information recording / reproducing apparatus Schematic showing an embodiment of the operation flow of the optical information recording / reproducing apparatus Schematic showing an embodiment of the operation flow of the optical information recording / reproducing apparatus Schematic showing an embodiment of the operation flow of the optical information recording / reproducing apparatus Schematic showing the Example of the signal generation part in an optical information recording / reproducing apparatus Schematic showing the Example of the signal processing part in an optical information recording / reproducing apparatus Schematic showing the Example of the operation | movement flow of a signal generation part and a signal processing part Schematic showing the Example of the operation | movement flow of a signal generation part and a signal processing part Schematic showing one configuration example of the image position detection unit Schematic showing the flow of sub-pixel position detection processing during playback Schematic showing an example of intermediate pattern Schematic showing a specific example of the middle part of the intermediate pattern and the inscribed partial area, Schematic diagram showing how to create enlarged patterns Schematic diagram showing the marker pattern center, marker pattern inscribed partial area, and marker pattern intermediate partial area Table showing the covariance value with the surrounding pattern for the center of the marker pattern Schematic diagram showing how to create enlarged patterns Schematic diagram showing the marker pattern center, marker pattern inscribed partial area, and marker pattern intermediate partial area Table showing the covariance value with the surrounding pattern for the center of the marker pattern Schematic diagram of recording unit and table showing covariance values of marker pattern center and surrounding pattern Schematic diagram showing the marker pattern simulation image formed on the pixel surface of the photodetector and the corresponding reference detection pattern Graph showing an example of sub-pixel position detection characteristics by this method

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiments of the present invention will be described with reference to the accompanying drawings. According to the marker pattern described in the present embodiment, it is possible to detect a sub-pixel position with a small influence of a recording pattern outside the marker pattern as in the conventional case, and to ensure the detectability even under a reproduction condition with a large inter-pixel interference. Is obtained.

FIG. 2 is a block diagram showing a recording / reproducing apparatus for an optical information recording medium for recording and / or reproducing digital information using holography.

The optical information recording / reproducing device 10 is connected to an external control device 91 via an input / output control unit 90. In the case of recording, the optical information recording / reproducing apparatus 10 receives the information signal to be recorded from the external control device 91 by the input / output control unit 90. When reproducing, the optical information recording / reproducing apparatus 10 transmits the reproduced information signal to the external control apparatus 91 by the input / output control unit 90.

The optical information recording / reproducing apparatus 10 includes a pickup 11, a reproduction reference light optical system 12, a cure optical system 13, a disk rotation angle detection optical system 14, and a rotation motor 50. The optical information recording medium 1 is a rotation motor. 50 can be rotated.

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

When reproducing the information recorded on the optical information recording medium 1, the reproduction reference light optical system 12 generates a light wave that causes the reference light emitted from the pickup 11 to enter the optical information recording medium in a direction opposite to that during recording. Generate. The reproduction light reproduced by the reproduction reference light is detected by a photodetector described later in the pickup 11, and the signal is reproduced by the signal processing unit 85.

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

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

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

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

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

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

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

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

FIG. 3 shows a recording principle in an example of a basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. The light beam emitted from the light source 301 passes through the collimator lens 302 and enters the shutter 303. When the shutter 303 is open, after the light beam passes through the shutter 303, the optical ratio of the p-polarized light and the s-polarized light becomes a desired ratio by the optical element 304 composed of, for example, a half-wave plate. After the polarization direction is controlled, the light is incident on a PBS (Polarization Beam Splitter) prism 305.

The light beam that has passed through the PBS prism 305 functions as signal light 306, and after the light beam diameter is expanded by the beam expander 308, the light beam passes through the phase mask 309, the relay lens 310, and the PBS prism 311 and passes through the spatial light modulator 312. Is incident on.

The signal light to which information is added by the spatial light modulator 312 reflects the PBS prism 311 and propagates through the relay lens 313 and the spatial filter 314. Thereafter, the signal light is condensed on the optical information recording medium 1 by the objective lens 315.

On the other hand, the light beam reflected from the PBS prism 305 functions as reference light 307 and is set to a predetermined polarization direction according to recording or reproduction by the polarization direction conversion element 316 and then galvano- lated via the mirror 317 and the mirror 318. Incident on the mirror 319. Since the angle of the galvanometer mirror 319 can be adjusted by the actuator 320, the incident angle of the reference light incident on the optical information recording medium 1 after passing through the lens 321 and the lens 322 can be set to a desired angle. In order to set the incident angle of the reference light, an element that converts the wavefront of the reference light may be used instead of the galvanometer mirror.

In this way, the signal light and the reference light are incident on the optical information recording medium 1 so as to overlap each other, whereby an interference fringe pattern is formed in the recording medium, and information is recorded by writing this pattern on the recording medium. To do. In addition, since the incident angle of the reference light incident on the optical information recording medium 1 can be changed by the galvanometer mirror 319, recording by angle multiplexing is possible.

Hereinafter, in holograms recorded in the same area with different reference beam angles, holograms corresponding to each reference beam angle are called pages, and a set of pages angle-multiplexed in the same area is called a book. .

FIG. 4 shows a reproduction principle in an example of a basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. When reproducing the recorded information, the reference light is incident on the optical information recording medium 1 as described above, and the light beam transmitted through the optical information recording medium 1 is reflected by the galvanometer mirror 324 whose angle can be adjusted by the actuator 323. By doing so, the reproduction reference light is generated.

The reproduction light reproduced by the reproduction reference light propagates through the objective lens 315, the relay lens 313, and the spatial filter 314. Thereafter, the reproduction light passes through the PBS prism 311 and enters the photodetector 325, and the recorded signal can be reproduced. As the photodetector 325, for example, an image sensor such as a CMOS image sensor or a CCD image sensor can be used, but any element may be used as long as the data page can be reproduced. In the following, the pixels of the spatial light modulator 312 and the photodetector 325 are distinguished as necessary, and the former pixel is referred to as “recording pixel” and the latter pixel as “reproduction pixel”. The data page is decoded from the detection image oversampled by the photodetector 325 having a reproduction pixel interval smaller than the recording pixel interval of the data page image projected on the pixel surface of the photodetector 325 during reproduction. Further, regarding the ratio of the reproduction pixel interval to the recording pixel interval (the reciprocal of the oversampling ratio), the row direction is αx and the column direction is αy.

The optical system shown in FIG. 5 has an advantage that the size can be greatly reduced by making the signal light and the reference light incident on the same objective lens as compared with the optical system configuration shown in FIG.

FIG. 6 shows an operation flow of recording and reproduction in the optical information recording / reproducing apparatus 10. Here, a flow relating to recording / reproduction using holography in particular will be described.

FIG. 6A shows an operation flow from when the optical information recording medium 1 is inserted into the optical information recording / reproducing apparatus 10 until preparation for recording or reproduction is completed, and FIG. FIG. 6C shows an operation flow until information is recorded on the information recording medium 1, and FIG. 6C shows an operation flow until the information recorded on the optical information recording medium 1 is reproduced from the ready state.

When a medium is inserted as shown in FIG. 6A (601), the optical information recording / reproducing apparatus 10 discriminates whether or not the inserted medium is a medium for recording or reproducing digital information using holography, for example. (602).

As a result of disc discrimination, when it is determined that the optical information recording medium records or reproduces digital information using holography, the optical information recording / reproducing apparatus 10 reads control data provided on the optical information recording medium (603). ), For example, information relating to the optical information recording medium and information relating to various setting conditions during recording and reproduction, for example.

After reading out the control data, various adjustments according to the control data and learning processing (604) related to the pickup 11 are performed, and the optical information recording / reproducing apparatus 10 is ready for recording or reproduction (605).

As shown in FIG. 6B, the operation flow from the ready state to recording information is as follows. First, data to be recorded is received (611), and information corresponding to the data is received from the spatial light modulator in the pickup 11. Send to.

Thereafter, various recording learning processes such as optimization of the power of the light source 301 and optimization of exposure time by the shutter 303 are performed in advance so that high-quality information can be recorded on the optical information recording medium (612). ).

Thereafter, in the seek operation (613), the access control unit 81 is controlled to position the pickup 11 and the cure optical system 13 at predetermined positions on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

Thereafter, a predetermined area is pre-cured using the light beam emitted from the cure optical system 13 (614), and data page generation processing (617) including main data generation (615) and page header addition (616) is performed, and pickup is performed. Data is recorded using the reference light and the signal light emitted from 11 (618). After recording the data, post cure is performed using the light beam emitted from the cure optical system 13 (619). Data may be verified as necessary. Main data is a part that occupies most of the data page, and mainly stores user data. In addition to user data, in a specific data page, a table indicating the correspondence between the logical address handled by the external control device 91 and the position of each data page in the optical information recording medium 1, or the replacement of a data page that has become difficult to reproduce due to a defect You may make it store the replacement position list | wrist showing the response | compatibility of the position of the data page before replacement and the replacement destination in a process. The page header is an area provided on the data page for storing information such as the type and data format of the data recorded on the data page and the address for identifying the multiple recorded pages. Is provided separately from the recording area on the data page.

As shown in FIG. 6C, the operation flow from the ready state to the reproduction of recorded information is as follows. First, in the seek operation (621), the access control unit 81 is controlled, and the pickup 11 and the reproduction reference light are reproduced. The position of the optical system 12 is positioned at a predetermined position on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

Subsequently, the reference light is emitted from the pickup 11, the information recorded on the optical information recording medium is read, the data page is acquired (622), and the reproduction data is obtained after the determination of the page header portion in the data page (623). Detection (624) and transmission (625). If the page data is not identified as the target data page as a result of the page header determination (623), there is a possibility that a data page different from the target is detected, so that the reproduction data is not transmitted (625). Either cancel or re-execute from the processes of (621) and (622).

FIG. 9 shows a data processing flow during recording and reproduction. FIG. 9A shows the two-dimensional data on the spatial light modulator 312 after the recording data reception processing 611 in the input / output control unit 90. FIG. 9B shows a recording data processing flow in the signal generation unit 86 until conversion, and FIG. 9B shows the process up to reproduction data transmission processing 624 in the input / output control unit 90 after the two-dimensional data is detected by the photodetector 325. The reproduction data processing flow in the signal processing unit 85 is shown.

The data processing during recording will be described with reference to FIG. The processing from 901 to 906 corresponds to the internal processing of the main data generation (615) in the processing of FIG. When the signal generator 81 receives the user data (901), it is divided into a plurality of data strings, and each data string is converted to CRC (902) so that error detection during reproduction can be performed, so that the number of on pixels is substantially equal to the number of off pixels. Then, after performing scramble (903) for adding a pseudo-random data sequence to the data sequence for the purpose of preventing repetition of the same pattern, an error correction encoding such as a Reed-Solomon code (904) is performed so that error correction can be performed during reproduction. )I do. Next, the two-dimensional data (905) is configured by arranging the error correction encoded data string according to a predetermined rule. Note that a modulation process such as run-length limited modulation may be added in the process 905. A marker serving as a reference for image position detection and image distortion correction at the time of reproduction is added to the two-dimensional data thus configured (906), and a page header is added (616) to the spatial light modulator 312. Data is transferred (907).

Next, the data processing flow during reproduction will be described with reference to FIG. The processing from 912 to 919 corresponds to the internal processing of data reproduction (624) in the processing of FIG. The image data detected by the photodetector 325 is transferred to the signal processing unit 85 (911), and the page header is determined from the detected image data (623), and the data stored in the page header is acquired. Next, the image position is detected with reference to the marker included in the image data (912), and distortion such as the tilt, magnification, and distortion of the image is corrected (913), and then binarization processing (914) is performed. By removing the marker (915), two-dimensional data for one page is acquired (916). After converting the two-dimensional data obtained in this way into a plurality of data strings, error correction processing (917) is performed to remove the parity data strings. Next, descrambling processing (918) is performed, CRC error detection processing (919) is performed, CRC CRC is deleted, and user data is transmitted (920) via the input / output control unit 90. If it can be expected that the image position detection by the marker (912) can be performed more easily than the determination of the page header (623), the order of these processes is changed, and the image position detection result by the marker is used for the page. A header search may be performed.

FIG. 7 is a block diagram of the signal generation unit 86 of the information recording / reproducing apparatus 10.

When the input of user data is started to the input / output control unit 90, the input / output control unit 90 notifies the controller 89 that the input of user data has started. Upon receiving this notification, the controller 89 instructs the signal generation unit 86 to record one page of data input from the input / output control unit 90, and provides the header pattern generation unit 710 with information to be stored in the page header. A processing command from the controller 89 is notified to the sub-controller 701 in the signal generation unit 86 via the control line 708. Upon receiving this notification, the sub-controller 701 controls each signal processing unit via the control line 708 so that the signal processing units are operated in parallel.

First, the memory control unit 703 is controlled to store the user data input from the input / output control unit 90 via the data line 709 in the memory 702. In another area of the memory 702, a marker pattern 712 that satisfies a condition that is suitable for detecting a sub-pixel position of an image is stored. The stored marker pattern may be a single pattern or a plurality of patterns. The memory element storing user data and the memory element storing the marker pattern 712 may be a single element or different elements.

When the user data stored in the memory 702 reaches a certain amount, the CRC calculation unit 704 performs control to convert the user data into CRC. Next, the scramble unit 705 scrambles the CRC-converted data to add a pseudo-random data sequence, the error correction encoding unit 706 performs error correction encoding to add the parity data sequence, and the marker adding unit 710 performs the control. A recording marker for the main data portion of the data page is generated by adding a reference marker at the time of reproduction, and stored in the memory 702. On the other hand, the header pattern generation unit 711 generates a page header recording pattern based on the information stored in the page header input from the controller 89 and stores it in the memory 702.

Finally, the pickup interface unit 707 reads the recording pattern of the main data and the recording pattern of the page header from the memory 702 in the arrangement order of the two-dimensional data on the spatial light modulator 312, and causes the spatial light modulator 312 in the pickup 11 to read it. Transfer two-dimensional data.

FIG. 8 is a block diagram of the signal processing unit 85 of the information recording / reproducing apparatus 10.

When the photodetector 325 in the pickup 11 detects the image data, the controller 89 instructs the signal processing unit 85 to reproduce the data for one page input from the pickup 11. A processing command from the controller 89 is notified to the sub-controller 801 in the signal processing unit 85 via the control line 811. In response to this notification, the sub-controller 801 controls each signal processing unit via the control line 811 so that the signal processing units operate in parallel. First, the memory control unit 803 is controlled to store the image data input from the pickup 11 via the pickup interface unit 810 via the data line 812 in the memory 802.

When the data stored in the memory 802 reaches a certain amount, the header pattern decoding unit 813 decodes the data stored in the page header, and the identification information of the detected data page is the data page targeted for reproduction. After the determination, the image position detection unit 809 performs control to detect a marker from the image data stored in the memory 802 and extract an effective data range. In another area of the memory 802, a reference detection pattern 814 that corresponds to the marker pattern 712 of the recorded data page and imitates a pattern imaged at a predetermined reproduction pixel position on the photodetector 325 during reproduction. Stored. The memory element that stores the user data and the memory element that stores the reference detection pattern 814 may be a single element or another element.

Next, using the detected marker, the image distortion correction unit 808 performs distortion correction such as image inclination, magnification, distortion, and the like, and controls to convert the image data into the expected two-dimensional data size. Each bit data of a plurality of bits constituting the size-converted two-dimensional data is binarized by a binarization unit 807 to determine “0” or “1”, and the data is arranged in the memory 802 in the order of the output of the reproduction data. Control to store. Next, the error correction unit 806 corrects an error included in each data sequence, and the scramble release unit 805 releases the scramble to add the pseudo random number data sequence, and then the CRC calculation unit 804 causes an error in the user data on the memory 802. Check not included. Thereafter, the user data is transferred from the memory 802 to the input / output control unit 90.

FIG. 10 shows a configuration example of the image position detection unit 809. The image position detection unit 809 includes a search region pattern acquisition unit 1001, a reference pattern acquisition unit 1002, a covariance calculation unit 1003, a covariance peak position determination unit 1004, and a subpixel position determination unit 1005.

The search area pattern acquisition unit 1001 acquires, from the memory 802, an area including one marker pattern among the data pages detected by the photodetector 325. The reference pattern acquisition unit 1002 acquires the reference detection pattern 814 stored in the memory 802. The covariance calculation unit 1003 applies to all partial regions that have the same number of reproduced pixels as the reference detection pattern 814 acquired by the reference pattern acquisition unit 1002 included in the region acquired by the search region pattern acquisition unit 1001. Thus, the covariance value with the reference detection pattern 814 is calculated. The covariance peak position discriminating unit 1004 discriminates a partial region where the covariance value obtained by the covariance calculation unit 1003 is maximized, and obtains a marker detection position in pixel units. The subpixel position discriminating unit 1005 discriminates a position (subpixel position) of one pixel or less by calculation using a covariance value in the vicinity of the partial region where the covariance value determined by the covariance peak position determining unit 1004 is maximum. To do. The sub-pixel position information obtained in this way is transmitted to the image distortion correction unit 808, and is used for distortion correction such as image inclination, magnification, and distortion.

By the way, in the technique described in Japanese Patent Laid-Open No. 2010-003358 (Patent Document 2), modulation that limits the minimum continuous length of on-pixels and off-pixels to a natural number of 2 or more in at least one of the row direction and the column direction of a data page. On the other hand, by using the spatial filter 314 in which the aperture size in this direction is reduced in inverse proportion to the minimum continuous length, the size of the hologram on the disk is reduced and recording is performed while ensuring the data page detectability. Improve density. It is known that the signal light 306 from the spatial light modulator 312 has an intensity distribution similar to the two-dimensional spatial frequency spectrum of the data page at a position on the optical axis where the spatial filter 314 is inserted at the time of recording. The aperture of the spatial filter 314 acts as a low-pass filter for the two-dimensional data pattern image. For this reason, when reproducing a data page recorded with a reduced aperture size of the spatial filter 314 as in the technique of Patent Document 2, the pixel surface of the photodetector 325 during reproduction with respect to the on-pixel of one recording pixel of the spatial light modulator 312. Since the spread of the signal light 306 irradiated thereon increases, interference between pixels increases. In order to effectively improve the recording density, the spatial frequency component corresponding to the repetition of the on-pixel and off-pixel having the minimum continuous length is allowed to pass, and the on-pixel and off-state having a continuous length 1 smaller than the minimum continuous length are passed. The aperture size of the spatial filter 314 is determined so as to block the spatial frequency component corresponding to the repetition of the pixel.

On the other hand, Japanese Patent Publication No. 2008-536158 (Patent Document 1) describes a marker pattern suitable for detecting a subpixel position. According to this, as a spare block (marker) suitable for determining the position error of the data page, all the covariance values of a specific sub-block in the spare block and other sub-blocks in contact with the end are all A pattern that becomes zero is used. The subpixel position detection using the spare block is a reproduction pixel for obtaining a position where the covariance value is maximum from the image detected by the photodetector 325 with reference to the ideal detection image based on the specific subblock. Subsequent to marker position determination in units, this is performed by arithmetic processing using a covariance value around the position where the covariance value is maximum. This makes it possible to detect the subpixel position while sufficiently reducing the influence from the recording pixel pattern outside the spare block. However, as a result of a search by the author, it was not possible to find a device that satisfies the conditions regarding the covariance values of the spare blocks while limiting the minimum continuous length as in Patent Document 1, and is considered suitable for detecting the pixel position.

Here, when the spare block described in Patent Document 1 is applied to the data page to which the technique of Patent Document 2 is applied, the spare block portion is strongly affected by the inter-pixel interference by the spatial filter 314 and is less than the minimum continuous length. There will be a continuous length pattern. On the other hand, according to the marker pattern generation method of the present application described below, such a pattern can be avoided.

Also, as the interference between pixels increases, the covariance value at the peak position and the covariance value for positions close to this position approach each other. This is because the spread of the signal light 306 irradiated on the pixel surface of the photodetector 325 with respect to one recording pixel of the spatial light modulator 312 has an intensity distribution similar to the pattern of the original spatial light modulator 312 (that is, This can be explained intuitively by being able to model the pattern with a large covariance value). At this time, in the marker position determination processing in units of reproduction pixels for obtaining the position where the covariance value is maximized from the image detected by the photodetector 325, the adjacent position of the position where the covariance value should originally be determined is determined. There is an increased risk of misjudging that the position has the maximum covariance value.

に対して There are two main measures for this problem. The first is to reduce the covariance value of the position adjacent to the peak position. Second, even when the peak position is misidentified as an adjacent position, an appropriate detection result can be obtained in the subsequent subpixel position detection processing. In the present application, based on the latter measure, sub-pixel position detection is possible even in a detection image with large inter-pixel interference. The inter-pixel interference depends on the product of the aperture size of the spatial filter 312 and the recording pixel pitch of the spatial light modulator 312 along this direction, and is recorded in the same manner as when the aperture size of the spatial filter 312 is reduced. Even when the pixel pitch is reduced, the inter-pixel interference increases. More specifically, the product of the recording pixel pitch in the row direction of the spatial light modulator 312 and the aperture size of the spatial filter 314 along this direction, the product of the pixel pitch in the column direction and the aperture size along this direction, In the smaller direction, the inter-pixel interference increases, in other words, the ratio of the recording pixel pitch to the size of the detected image corresponding to a single recording pixel increases.

Next, the method for generating the marker pattern will be described in detail. FIG. 1 is a flowchart of marker pattern generation processing. The marker pattern generation process is roughly divided into an intermediate pattern generation step 101 and an enlarged pattern generation step 102. In the intermediate pattern generation step 101, the intermediate pattern center area excluding the outer edge part composed of the recording pixels in contact with the boundary and the partial area inscribed in the boundary of the intermediate pattern having the same two-dimensional pixel arrangement as the intermediate pattern central part To obtain a characteristic intermediate pattern in which the covariance value with all of is zero.

The intermediate pattern generation step 101 includes, for example, an intermediate pattern candidate acquisition step 103, an intermediate pattern center acquisition step 1104, an inscribed partial region acquisition step 105, a covariance value calculation step 106, and a covariance condition determination step 107. I do.

The intermediate pattern candidate acquisition step 103 is a step of acquiring an intermediate pattern candidate that is a two-dimensional pattern having the same number of recording pixels in the column direction and the row direction as the intermediate pattern to be obtained. The intermediate pattern center portion acquisition step 104 is a step of acquiring an intermediate pattern center portion excluding an outer edge portion composed of recording pixels in contact with the boundary from the intermediate pattern candidates. The inscribed partial area acquisition step 105 selects all of the inscribed partial areas from the intermediate pattern candidates, which are partial areas inscribed in the boundary of the intermediate pattern while the number of recording pixels in the column direction and the row direction is the same as the intermediate pattern center. It is a step to acquire. In the covariance value calculation step 106, the covariance with the intermediate pattern center acquired in the intermediate pattern center acquisition step 104 for all of the partial regions inscribed in the boundary of the intermediate pattern acquired in the inscribed partial region acquisition step 105. This is a step for obtaining a value. The covariance condition determining step 107 is a step for determining whether or not all the covariance values obtained in the covariance value calculating step 106 are all 0. If all the covariance values are 0, the intermediate pattern candidate at that time is determined as the intermediate pattern candidate. On the other hand, if it is determined that all the patterns are not 0, the intermediate pattern candidate acquisition step 103 is performed again to update the intermediate pattern candidates, and the processes 103 to 107 described above are performed.

In the enlarged pattern generation step 102, each recording pixel of the intermediate pattern has Nx pixels in the row direction and Ny pixels in the column direction (Nx, Ny is a positive integer, at least one is 2 or more). Replace with the same polarity pattern. Here, Nx and Ny are the same as or larger than the minimum continuous length of the user data portion in the corresponding direction. In the enlargement pattern generation step 102, for example, a row direction enlargement step 108 and a column direction enlargement step 109 are performed. In the row direction enlargement step 108, each recording pixel of the intermediate pattern is replaced with a recording unit having the same polarity as these pixels, and having the size of one recording pixel in the column direction and Nx recording pixels in the row direction. As a result, a row direction enlarged pattern obtained by multiplying the intermediate pattern by Nx in the row direction is obtained. In the column direction enlargement step 109, similarly, each recording pixel of the enlarged row direction pattern is changed to a recording unit having the same polarity as these pixels, the size of Ny recording pixels in the column direction, and the size of one recording pixel in the row direction. Replace all. Through the row direction enlargement step 108 and the column direction enlargement step 109, an enlargement pattern is finally obtained that is enlarged Nx times in the row direction and Ny times in the column direction with respect to the intermediate pattern. In the present embodiment, the enlarged pattern obtained in this way is applied as a marker pattern. Note that the larger the magnifications Nx and Ny in the enlarged pattern generation step 102, the smaller the influence of inter-pixel interference. Therefore, according to the generation method having the two steps of the intermediate pattern generation step 101 and the enlarged pattern generation step 102, the position detection accuracy and reliability required for reproducing the page data to be recorded, and the tolerance By switching Nx and Ny in consideration of the occupancy rate of the marker pattern to be performed, it is possible to easily provide an appropriate marker pattern according to the case.

Next, actual examples of the intermediate pattern and the marker pattern that have been described above with respect to the generation method will be shown.

FIG. 12 is an example of an intermediate pattern. Hatched squares represent off pixels, and white squares represent on pixels. In this embodiment, the number of recorded pixels is 8 pixels in both the row direction and the column direction, and the outer edge surrounding this is the boundary. FIG. 13 shows an intermediate pattern central portion (1401) and an inscribed partial region (1402) in the intermediate pattern shown in FIG. In FIG. 13 (e), the dotted line portion represents the intermediate pattern central portion 1401, and specifically, the recording pixels in contact with the boundary are excluded from the intermediate patterns that form a square of 8 recording pixels in the row direction and the column direction. This is a square area having 6 recording pixels per side. 13 (a) to 13 (d) and FIGS. 13 (g) to 13 (i), the area surrounded by a thick line represents the inscribed

partial area

1402, and 6 recording pixels per side having the same intermediate pattern. It is inscribed in the boundary of the intermediate pattern while forming a square. Note that different values (for example, 1 for the on pixel and −1 for the off pixel) are given to the on pixel and the off pixel, and the intermediate pattern center portion 1401 shown in FIG. 13 (e) and FIGS. 13 (a) to (d) ), Calculating the covariance values between the inscribed partial areas 1402 shown in each of FIGS. 13G to 13I, all the covariance values are zero. Further, the intermediate pattern in FIG. 12 is a pattern that is point-symmetric with respect to the center point and has a polarity reversed with respect to the center line in both the row direction and the column direction. Thereby, the number of on pixels and off pixels can be made the same. In addition, if the 1/4 recording pixel is determined in the intermediate pattern and the enlarged pattern, the other 3/4 recording pixels can be determined in conjunction with each other. Therefore, the information amount of the marker pattern 712 stored in the memory 702 Can be saved.

FIG. 14 shows an example of an intermediate pattern and an enlarged pattern that has undergone an enlarged pattern generation step 1102, and FIG. 14 shows an example in which Nx = 2 times in the row direction and Ny = 1 times in the column direction. FIG. 14A shows an example of a recording unit for generating an intermediate pattern and an enlarged pattern. The recording unit is a rectangle composed of Nx = 2 recording pixels in the row direction and Ny = 1 recording pixel in the column direction. The polarity (on pixel or off pixel) of all the recording pixels in the recording unit is the same as the intermediate pattern of the replacement source. FIG. 14B shows an enlarged pattern obtained by the intermediate pattern and the replacement shown in FIG. The enlarged pattern has a recording pixel number that is Nx = 2 times in the row direction and Ny = 1 times in the column direction with respect to the intermediate pattern. Further, the continuous number of on-pixels and off-pixels in the enlargement pattern is an integer multiple of Nx = 2 in the row direction and only an integer multiple of Ny = 1 in the column direction. In particular, the minimum continuous number is Nx in the row direction. = 2 and Ny = 1 in the column direction. When the enlarged pattern as shown in FIG. 14B is used as the marker pattern, for example, by applying the technique of Patent Document 2, modulation is performed so that the minimum continuous number of on pixels and off pixels is 2 in the row direction. On the other hand, even when the spatial frequency component corresponding to the pattern in which the on-pixel and the off-pixel of one recording pixel are repeated in the row direction is blocked by the opening of the spatial filter 314, the continuous number in the row direction is included in the marker pattern. The effect of ensuring the detectability can be obtained by not including one pattern.

FIG. 17 shows an example of an intermediate pattern and another enlarged pattern that has undergone an enlarged pattern generation step 1102. FIG. 17 shows an example in which Nx = 2 times in the row direction and Ny = 2 times in the column direction. Yes. FIG. 17A shows an example of a recording unit for generating an intermediate pattern and an enlarged pattern. The recording unit is a square composed of Nx = 2 recording pixels in the row direction and Ny = 2 recording pixels in the column direction. The polarity (on pixel or off pixel) of all the recording pixels in the recording unit is the same as the intermediate pattern of the replacement source. FIG. 17B shows an enlarged pattern obtained by the intermediate pattern and the replacement shown in FIG. The enlarged pattern has a recording pixel number Nx = 2 times in the row direction and Ny = 2 times in the column direction with respect to the intermediate pattern. Further, the continuous number of on-pixels and off-pixels in the enlargement pattern is only an integer multiple of Nx = 2 in the row direction and only an integer multiple of Ny = 2 in the column direction. In particular, the minimum continuous number is Nx in the row direction. = 2 and Ny = 2 in the column direction. When an enlarged pattern as shown in FIG. 17 (b) is used as a marker pattern, modulation is performed such that the minimum continuous number of on-pixels and off-pixels is 2 in both the row direction and the column direction by applying the technique of Patent Document 2. On the other hand, even if the spatial frequency component corresponding to the pattern in which the on-pixel and the off-pixel of one recording pixel are repeated in the row direction and the column direction is blocked by the opening of the spatial filter 314, it is continuously included in the marker pattern. The effect of ensuring the detectability can be obtained by not including the pattern of Formula 1.

More generally, when the enlarged pattern obtained by the generation method of FIG. 1 is used as a marker pattern, the minimum continuous number of on-pixels and off-pixels in the row direction is Nx and the column direction is applied by applying the technique of Patent Document 2. While Ny modulation is applied, the spatial filter 314 has an opening that repeats the on pixel and the off pixel of the (NxＮ-1) recording pixel in the row direction and (Ny -1) recording pixel in the column direction. Even when the corresponding spatial frequency component is cut off, it is possible to ensure detectability by not including a continuous number of patterns less than (Nx-1) in the row direction and (Ny-1) in the column direction in the marker pattern. Is obtained.

Next, the characteristics of the enlarged pattern (applied as a marker pattern) obtained in this way will be described. Here, for easy understanding, as a specific example, an example of Nx = 2 and Ny = 1 and an example of Nx = 2 and Ny = 2 are shown, and then a generalized example is shown.

The enlarged pattern obtained in this way is composed only of patterns in which the continuous number of on-pixels and off-pixels is a multiple of predetermined integers Nx and Ny in the row direction and the column direction of each recording pixel. The marker pattern center excluding the outer edge corresponding to the range of distances within the same number of pixels as the predetermined integers Nx and Ny and the marker pattern center have the same number of pixels in the row direction and the column direction. The covariance value with all of the marker pattern inscribed partial areas inscribed in the marker pattern boundary is zero.

In addition, the marker pattern middle part region having the same number of pixels in both the row direction and the column direction as the marker pattern center part and existing in the marker pattern but not inscribed in the boundary of the marker pattern, and the marker pattern center part The covariance value with (Nx ′ |) Ny ′) is (Nx− | Nx ′ |) / (Ny− | Ny ′ |) / (Nx Ny) The size is proportional to.

FIG. 15 shows each of the marker pattern center portion, the marker pattern inscribed partial region, and the marker pattern intermediate partial region, taking the enlarged pattern when Nx = 2 and Ny = 1 shown in FIG. 14B as an example. ing. Reference numeral 1601 denotes a marker pattern central part, 1602 denotes a marker pattern inscribed partial area, and 1603 denotes a marker pattern intermediate partial area. The number of recorded pixels in the row direction 12 and the column direction 6 is obtained by subtracting twice the Nx = 2 and Ny = 1 corresponding to the outer edge portion from the row direction 16 and the column direction 8 that are the number of pixels of the marker pattern. This is the number of recording pixels. FIGS. 15 (a) to 15 (o) show all the positional relationships of the area of the recording pixels in the row direction 12 and the column direction 6 that can exist in the enlarged pattern, and FIGS. 15 (a) and 15 (b) in contact with the outer edge. , (C), (d), (f), (g), (i), (j), (l), (m), (n), (o), the marker pattern internal partial area 1602, In FIG. 15H existing at the center, the marker pattern central portion 1601 is formed, and in the remaining FIGS. 15E and 15K, the marker pattern intermediate portion region 1603 is formed. FIG. 16 shows a covariance value between the marker pattern central portion 1601 and a pattern at a position shifted by Nx recording pixels in the row direction and Ny recording pixels in the column direction. Here, the covariance value is normalized so that the covariance value between the pattern of Nx ′ = 0 and Ny ′ = 0 (that is, the marker pattern central portion 1601 itself) is 1. (Nx ′, Ny ′) = (− 1, 0) and (Nx ′, Ny ′) = (1, 0) corresponding to the marker pattern intermediate partial area 1603
The covariance value is 0.5 for this pattern. Further, Ny ′ = ± 1 corresponding to the marker pattern inscribed partial region 1602 and any position of Nx ′ = − 2, −1, 0, 1, 2 and (Nx ′, Ny ′) = (− 2, The covariance value is 0 for the patterns at the positions (0) and (Nx ′, Ny ′) = (2, 0).

FIG. 18 shows each of the marker pattern center portion, the marker pattern inscribed partial region, and the marker pattern intermediate partial region, taking the enlarged pattern when Nx = 2 and Ny = 2 as an example. Reference numeral 1901 denotes a marker pattern central portion, 1902 denotes a marker pattern inscribed partial area, and 1903 denotes a marker pattern middle partial area. The number of recorded pixels in the row direction 12 and the column direction 12 is obtained by subtracting twice the Nx = 2 and Ny = 2 corresponding to the outer edge from the row direction 16 and the column direction 16 that are the number of pixels of the marker pattern. This is the number of recording pixels. FIGS. 18 (a) to (y) show all the positional relationships of the recording pixels in the row direction 12 and the column direction 12 that can exist in the enlarged pattern. FIGS. 18 (a) and 18 (b) are in contact with the outer edge. , (C), (d), (e), (f), (j), (k), (o), (p), (t), (u), (v), (w), ( In (x) and (y), the marker pattern internal partial region 1902, in FIG. 18 (m) existing at the center, the marker pattern central portion 1901, and the remaining FIG. 18 (g), (h), (i), (l ), (N), (q), (r), and (s), the marker pattern intermediate partial region 1903 is obtained. FIG. 19 shows a covariance value between the marker pattern center portion 1901 and the pattern at a position shifted by Nx recording pixels in the row direction and Ny recording pixels in the column direction. The covariance value here is normalized so that the covariance value between the pattern of Nx ′ = 0 and Ny ′ = 0 (that is, the marker pattern central portion 1901 itself) is 1. (Nx ′, Ny ′) = (− 1,0), (Nx ′, Ny ′) = (1,0), (Nx ′, Ny ′) = (0, −) corresponding to the marker pattern intermediate partial region 1903 1), (Nx ′, Ny ′) = (0, 1), (Nx ′, Ny ′) = (− 1,0), (Nx ′, Ny ′) = (1,0) Has a covariance value of 0.5, and (Nx ′, Ny ′) = (− 1, 1), (Nx ′, Ny ′) = (1, 1), (Nx ′, Ny ′) = (1 , -1) and (Nx ', Ny') = (-1, -1), the covariance value is 0.25. The covariance value is 0 for the pattern at the position of Nx ′ = ± 2 or Ny ′ = ± 2 corresponding to the marker pattern inscribed partial region 1902.

FIG. 20 (a) shows, as a more general form, when the number of recording pixels of one recording unit is Nx recording pixels in the row direction and Ny recording pixels in the column direction, the recording pixel の of the intermediate pattern and the enlarged pattern As described above, the recording unit has the same polarity as each recording image of the intermediate pattern, and has a size of Ny recording pixels in the column direction and Nx recording pixels in the row direction. By this replacement, the obtained enlarged pattern (applied as a marker pattern) has the number of recording pixels Ny times in the column direction and Nx times in the row direction with respect to the original intermediate pattern. The center portion of the marker pattern has a smaller number of recording pixels by 2Nx recording pixels in the row direction and 2Ny recording pixels in the column direction than the enlarged pattern. FIG. 20B shows the covariance value between the pattern at the position shifted from the marker pattern central portion 1901 by Nx recording pixels in the row direction and Ny recording pixels in the column direction. The covariance value here is normalized so that the covariance value between the pattern of Nx ′ = 0 and Ny ′ = 0 (that is, the marker pattern central portion 1901 itself) is 1. The covariance value is 0 for the pattern at the position of Nx ′ = ± Nx or Ny ′ = ± Ny corresponding to the marker pattern inscribed partial region. In addition, the covariance value of the pattern at the position corresponding to the marker pattern intermediate partial region changes depending on the relative position (Nx ′, Ny ′) with respect to the marker pattern center, and the value is (Nx− | Nx ′ |) ( Ny− | Ny ′ |) / {Nx Ny), which is a value proportional to the product of the relative distance in the row direction and the relative distance in the column direction.

If the enlarged pattern of the present embodiment described above is adopted as a marker pattern, a reference detection pattern having a reproduction pixel number that imitates a detection image corresponding to the recording pixel area at the center of the marker pattern is provided during reproduction. And the center of gravity from the covariance value acquired for the reproduction pixel area located in the vicinity and the area corresponding to the recording pixel area of the marker pattern. By using a similar calculation, it is possible to obtain an effect of enabling sub-pixel position detection with a small influence of the recording pattern outside the marker pattern. In particular, by applying the technique of Patent Document 2, modulation is performed such that the minimum continuous numbers of on-pixels and off-pixels in the row direction and the column direction become Nx and Ny, respectively, while the spatial filter 314 opens the row. Even when the spatial frequency component corresponding to the pattern in which the on-pixel and the off-pixel of one recording pixel are repeated in the direction and the column direction is cut off, the pattern or column that is not more than Nx−1 in the row direction in the marker pattern The effect of ensuring the detectability can be obtained by not including a pattern with a large inter-pixel interference that is equal to or less than the continuous number Ny−1 in the direction.

In the present embodiment, a method for detecting the sub-pixel position of the reproduction pixel at the time of reproducing the data page using the marker pattern described in the first embodiment will be described. By performing the subpixel position detection of the present embodiment using the marker pattern described in the first embodiment, the subpixel is correctly detected even if the covariance peak position is misidentified as the adjacent position under the reproduction condition where the inter-pixel interference is large. The effect that the position can be obtained is obtained.

The subpixel position is detected according to the flow shown in FIG. In FIG. 11, reference numeral 1101 denotes a step of acquiring a partial detection image, 1102 denotes a reference detection pattern generation step, 1103 denotes a covariance value calculation step, 1104 denotes a pixel unit position determination step, and 1105 denotes a subpixel position determination step.

In step 1101 of acquiring a partial detection image, a partial detection image of a part including only one marker pattern is acquired from page data detected by the photodetector 325. Even in the case where the position of the data page imaged on the pixel surface of the photodetector 325 shifts, a certainly large reproduction pixel area is necessary for the marker pattern to exist inside. It is necessary to reduce the reproduction pixel area to such an extent that a plurality of marker patterns do not exist in the partial detection image. Further, the larger the partial detection image, the larger the calculation amount of processing. Therefore, the size of the partial detection image should be within the minimum necessary range that allows for the detection position shift.

In a reference detection pattern generation step 1102, a reference detection pattern used for a covariance calculation performed in a later stage is generated. The reference detection pattern is a pattern simulating a detection image corresponding to the recording pixel area at the center of the marker pattern, and the number of reproduced pixels is about 1 / αx times in the row direction and 1 / αy in the column direction. The number of recording pixels at the center of the marker pattern is set to be about twice as large (αx and αy are the ratio of the reproduction pixel interval to the recording pixel interval in the row direction and the column direction, respectively, and the reciprocal of the oversampling ratio). For example, an apparatus for detecting a data page using a photodetector 325 having a reproduction pixel interval of αx = 3/4 times in the row direction and αy = 3/4 times in the column direction with respect to the recording pixel interval, as shown in FIG. When the sub-pixel detection is performed using the marker pattern having the marker pattern central portion 1601 of 12 recording pixels in the row direction and 8 recording pixels in the column direction, the number of reproduced pixels of the reference detection pattern is 16 in the row direction and the column direction. Eight. More specifically, since it is calculated that a marker pattern detection image having an intensity distribution as shown in FIG. 21A is formed on the pixel surface of the photodetector 325, a corresponding figure is obtained. A reference detection pattern as shown in 21 (b) is provided. Further, when the reference detection pattern is created, the signal light 306 irradiated on the pixel surface of the photodetector 325 at the time of reproduction with respect to the difference between the recording pixel interval and the reproduction pixel interval or the on-pixel of one recording pixel of the spatial light modulator 312. The pattern with multi-valued luminance is taken into consideration. The reference detection pattern generation step 1102 needs to be performed before the covariance value calculation step 1103, but is not performed every time a data page is detected, but is created by a simulator or the like provided outside the apparatus in advance. The stored pattern may be stored in the memory 802 or the like.

In the covariance value calculation step 1103, all detection image portions having the same size as the reference detection pattern obtained in the reference detection pattern generation step 1102 included in the range of the partial detection image acquired in step 1101 of acquiring the partial detection image. Find the covariance value for the region. In the pixel unit position determination step 1104, the position of the marker pattern in the reproduction pixel unit from the maximum covariance value obtained in the covariance value calculation step 1103 and the corresponding position of the detected image partial region. Is determined. In the sub-pixel position determining step 1105, the reproduction pixels of only the integer N1 that does not exceed Nx / αx in the row direction with respect to the outside of the detected image partial region where the covariance value determined in the pixel unit position determining step 1104 is maximum. Based on the covariance value obtained in the covariance value calculation step with respect to the detected image partial region included in the region enlarged by the reproduction pixel of the integer N2 not exceeding Ny / αy in the column direction, the subpixel position Is determined. The calculation of Equation 1 or Equation 2 can be applied to the subpixel position determination from the covariance value.

In these, Δx is a sub-pixel position in the row direction, Δy is a sub-pixel position in the column direction, and is based on the position in the reproduction pixel (integer) unit obtained in the pixel unit position determination step 1104 and the actually generated reproduction pixel. Represents the difference from the position with fine accuracy. N1 is an integer not exceeding Nx / αx, N2 is an integer not exceeding Ny / αy, βx is a scale factor in the row direction, and βy is a scale factor in the column direction. Further, the covariance value for the detection image partial area shifted by p reproduction pixels in the row direction and q reproduction pixels in the column direction from the detection image partial area where the covariance value is maximum is represented by Cov [p] [ q]. In Equation 1, the detection image partial area in a range shifted by ± N1 reproduction pixels in the row direction and ± N2 in the column direction with respect to the outside of the detection image partial area where the covariance value determined in the pixel unit position determination step 1104 is maximum. The calculation is performed using the covariance value with all. In Equation 2, the processing of Equation 1 is simplified, and the same reproduction pixel position is fixed in the column direction around the detected image partial region where the covariance value determined in the pixel unit position determination step 1104 is the maximum. The sub-pixel position in the row direction is determined using the covariance value in the range shifted by ± N1 playback pixels in the direction, fixed to the same playback pixel position in the row direction, and the range shifted by ± N2 playback pixels in the column direction The sub-pixel position in the column direction is determined using the covariance value. Since the effect of the present technology can be obtained by applying either Equation 1 or Equation 2, it is preferable that the selection is made in consideration of the amount of calculation processing load and subpixel position detection accuracy.

An example of the characteristics of the sub-pixel position detection method according to the present method described above is shown in FIGS. 22 (a) and 22 (b). These determine the aperture size of the spatial filter 314 so as to limit a spatial frequency of about 1.1 times the spatial frequency corresponding to the repetition pattern of on-pixel and off-pixel of one recording pixel in the column direction. On the other hand, in the row direction, the aperture size of the spatial filter 314 is determined so as to limit the spatial frequency of about 0.55 times the spatial frequency corresponding to the repeated pattern of on-pixel and off-pixel of one recording pixel. This was obtained by simulation simulating the condition that increased the amount of inter-pixel interference with respect to the direction. Here, as the marker pattern of this system, the recording unit size Nx = 2 recording pixels and Ny = 1 recording pixels shown in FIGS. 14 and 15 was applied. Further, the intermediate pattern of FIG. 14 was applied as a marker pattern to the plot of the characteristic of the conventional method shown for comparison. This pattern satisfies the covariance condition required for the marker pattern described in Patent Document 1. Also, at the time of reproduction, a data page is detected by using a photodetector 325 having a reproduction pixel interval of αx = 3/4 times in the row direction and αy = 3/4 times in the column direction with respect to the recording pixel interval. Assuming that the number of reproduced pixels of the reference detection pattern is 16 in the row direction and 8 in the column direction. Furthermore, the outside of the detection image partial area where the covariance value is maximum, the sub-pixel position using the covariance value of the detection image partial area in the range shifted ± 2 pixels in the row direction and ± 1 in the column direction The operation for obtaining was performed.

FIG. 22A shows an application when the relative position between the received light image and the reproduction pixel is shifted in the row direction with reference to the position where the same image as the reference detection pattern is detected by the reproduction pixel of the photodetector 325. The relationship between the shift amount and the detected shift amount is shown. FIG. 22B shows the detection error amount (difference between the detection shift amount and the applied shift amount) at this time. Here, if it can be expected that the maximum covariance value can be correctly detected at the marker pattern position in the reproduction pixel unit obtained in the pixel unit position determination step 1104, the applied shift amount is within the range of 0.5 reproduction pixels. As long as the accuracy of the detected shift amount can be ensured. However, in the case where the inter-pixel interference is large as in the present embodiment, the position where the same image as the reference detection pattern having the maximum covariance value is detected by the reproduction pixel of the photodetector 325 and the vicinity thereof are detected. There is a possibility that the covariance value approaches and the covariance value detected for the adjacent position is maximized. In such a case, it is required to ensure the accuracy of the detection shift amount within the range of 1.5 reproduction pixels, to which the applied shift amount for one reproduction pixel is further added. The scale factor βx is given so that the average detection error amount in the range of the shift amount 0 to 1.5 reproduction pixels is minimized. At this time, as shown in FIG. 22A, according to this method, sub-pixel position detection characteristics with better linearity than the conventional method can be obtained, and as shown in FIG. In the conventional method, a detection error amount in the range of -0.18 reproduction pixel to 0.47 reproduction pixel is seen, whereas in this method, from about-1/6 to 1/4 of -0.06 reproduction pixel. As a result, the detection error amount in the range of 0.12 reproduced pixels was reduced. Note that evaluation was made for each of the case where the shift amount in the column direction was 0 reproduction pixels and 0.5 reproduction pixels, but no significant difference was observed. If the recording unit size is larger than the recording unit size (Nx = 2, Ny = 1) shown here, the same or higher effect can be obtained. However, since the occupation rate of the marker pattern to be closed in the data page increases, The recording unit size may be determined so that the repeated spatial frequency of the on-pixel pattern and the off-pixel pattern has a minimum size that is not blocked by the opening of the spatial filter 314.

As shown by this result, according to the sub-pixel detection method of the present embodiment using the marker pattern described in the first embodiment, the covariance peak position is misidentified as the adjacent position under the reproduction condition where the inter-pixel interference is large. Even if it occurs, it is possible to obtain the effect of correctly obtaining the subpixel position.

Needless to say, the present invention can be applied not only to the angle multiplexing method but also to other methods such as a shift multiplexing method. Furthermore, the two-dimensional data page need not be recorded as a hologram, and may be recorded in another form.

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

In addition, each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them by, for example, an integration means. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function can be stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

Also, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium, 10 ... Optical information recording / reproducing apparatus, 11 ... Pickup,
12 ... Reference light optical system for reproduction, 13 ... Disc Cure optical system,
14: Optical system for detecting the disk rotation angle,
81 ... access control unit,
82: Light source drive unit, 83: Servo signal generation unit,
84 ... Servo control unit, 85 ... Signal processing unit, 86 ... Signal generation unit,
87: shutter control unit, 88 ... disk rotation motor control unit,
89 ... Controller, 90 ... Input / output control unit, 91 ... External control device,
101 ... Intermediate pattern generation step,
102 ... Expansion pattern generation step,
103 ... Intermediate pattern candidate update step,
104 ... Intermediate pattern center acquisition step,
105 ... inscribed partial region acquisition step,
106 ... covariance value calculation step,
107 ... covariance condition determination step,
108 ... row direction enlargement step,
109 ... Column direction enlargement step,
301: Light source, 303: Shutter, 306: Signal light, 307: Reference light,
308 ... Beam expander, 309 ... Phase mask,
310 ... Relay lens, 311 ... PBS prism,
312 ... Spatial light modulator, 313 ... Relay lens, 314 ... Spatial filter,
315: Objective lens, 316: Polarization direction conversion element, 320 ... Actuator,
321 ... Lens, 322 ... Lens, 323 ... Actuator,
324 ... Mirror, 325 ... Photodetector 501 ... Light source, 502 ... Collimating lens, 503 ... Shutter, 504 ... Optical element,
505 ... PBS prism, 506 ... signal light, 507 ... PBS prism, 508 ... spatial light modulator,
509 ... Angle filter, 510 ... Objective lens, 511 ... Objective lens actuator,
512 ... Reference light, 513 ... Mirror, 514 ... Mirror, 515 ... Lens,
516 ... Galvano mirror, 517 ... Actuator, 518 ... Photo detector,
519: Polarization direction conversion element, 520: Driving direction, 521: Optical block 1101 ... Step of acquiring a partial detection image,
1102 ... reference detection pattern generation step,
1103 ... Covariance value calculation step,
1104: Pixel unit position determining step,
1105 ... Subpixel position determination step,
1401 ... middle pattern center,
1402 ... inscribed partial area,
1601 ... Marker pattern center,
1602 ... Marker pattern inscribed partial area,
1603 ... Marker pattern middle partial area,
1901 ... Marker pattern center,
1902: Marker pattern inscribed partial area,
1903: Marker pattern middle part area

Claims

A method for generating a marker pattern recorded on a two-dimensional data page,
An intermediate pattern generating step for generating an intermediate pattern for generating the marker pattern;
An enlarged pattern generating step for generating a pattern obtained by enlarging the generated intermediate pattern;
With
In the intermediate pattern generation step, the intermediate pattern has a covariance value of 0 between the central portion of the intermediate pattern excluding the outer edge portion composed of pixels in contact with the boundary and the partial region inscribed in the boundary of the intermediate pattern. Generate an intermediate pattern,
In the enlarged pattern generation step, each recording pixel of the intermediate pattern is replaced with a recording unit in which recording pixels having the same polarity as each recording pixel are arranged in at least one of the row direction and the column direction by a plurality of recording pixels. A marker pattern generation method characterized by the above.
It is a marker pattern production | generation method of Claim 1, Comprising:
The two-dimensional data page is reproduced by a photodetector having reproduction pixels arranged two-dimensionally,
The number of recording pixels in the row direction and the number of recording pixels in the column direction of the recording unit are different,
Detection that forms an image on the photodetector corresponding to a single recording pixel as compared to the size of the interval between the recording pixels in the detection image of the two-dimensional data page imaged on the photodetector. A marker pattern generation method, wherein a plurality of recording pixels of the recording unit are arranged in a direction in which an image size is large.
It is a marker pattern production | generation method of Claim 1, Comprising:
In the two-dimensional data page, a pattern in which an on-pixel and an off-pixel are continuous by at least one of a natural number greater than 2 is recorded in at least one of a row direction and a column direction of a recording pixel,
The marker pattern generation method according to claim 1, wherein the recording unit has a recording pixel number equal to or greater than a minimum continuous number in each direction in the row direction and the column direction.
An information recording medium on which a two-dimensional data page, which is reproduced by a photodetector having two-dimensionally arranged reproduction pixels and is composed of two-dimensionally arranged recording pixels, is recorded,
A marker pattern is arranged at a predetermined position on the two-dimensional data page,
The marker pattern is a recording composed of recording pixels having the same polarity with the number of recording pixels of integers Nx and Ny in which the number of consecutive on pixels and off pixels is constant in each direction in the row direction and the column direction of each recording pixel. Composed of units,
An intermediate pattern obtained by replacing the recording unit with a single recording pixel having the same polarity as the recording unit pixel includes an intermediate pattern central portion excluding an outer edge portion of the intermediate pattern, and an intermediate pattern central portion that is the same as the intermediate pattern central portion. An information recording medium on which a two-dimensional data page having a covariance value of 0 with a partial area inscribed in a boundary of the intermediate pattern having a two-dimensional pixel arrangement is recorded.
An information recording medium according to claim 4, wherein
The number of recording pixels in the row direction and the number of recording pixels in the column direction of the recording unit are different,
Detection that forms an image on the photodetector corresponding to a single recording pixel as compared to the size of the interval between the recording pixels in the detection image of the two-dimensional data page imaged on the photodetector. An information recording medium, wherein a plurality of recording pixels of the recording unit are arranged in a direction in which an image size is large.
An information recording medium according to claim 4, wherein
In the two-dimensional data page, a data pattern is recorded such that the number of on-pixels and off-pixels is at least greater than 2 in at least one of the row direction and the column direction of the recorded pixels, and the integer Nx , Ny has a number of pixels equal to or greater than the minimum continuous number in each direction.
An information recording medium reproducing device for reproducing the information recording medium according to claim 4,
A pickup having the photodetector;
A signal processing unit for reproducing a signal based on a detection image of a two-dimensional data page from the pickup;
A memory for storing a reference detection pattern;
An image position detection unit that reads out the detection image and the reference detection pattern stored in the memory and detects a position of the detection image on the photodetector;
A search area pattern acquisition unit that acquires an area including the marker pattern from the memory in the detection image;
A reference pattern acquisition unit for acquiring the reference detection pattern from the memory;
Covariance calculation for calculating a covariance value with the reference detection pattern for a partial region having the same number of reproduced pixels as the reference detection pattern included in the region acquired by the search region pattern acquisition unit A covariance peak position determination unit that determines a partial region where the covariance value obtained by the covariance calculation unit is maximized, and obtains a marker detection position in pixel units;
Reproduction pixels of only integer N1 that do not exceed Nx / αx in the row direction and reproduction pixels of integer N2 that do not exceed Ny / αy in the column direction with respect to the partial region position that is the peak determined by the covariance peak position determination unit A sub-pixel position determination unit that determines a sub-pixel position based on the covariance value obtained by the covariance value calculation unit for the detection image partial region included in the region that is enlarged only;
An information recording medium reproducing apparatus comprising:
The information recording medium reproducing device according to claim 7,
The sub-pixel position determination unit
An integer N1 not exceeding Nx / αx;
An integer N2 not exceeding Ny / αy;
The scale factor βx in the row direction,
Scale factor βy in the column direction,
The covariance value Cov [p for the detection increase partial area shifted by p reproduction pixels in the row direction and q reproduction pixels in the column direction from the detection image partial area where the covariance value is maximum. ] [q]
Sub-pixel position is detected according to the number 1 expressed using

8. The information recording medium playback device according to claim 7, wherein
The information recording medium reproducing device according to claim 7,
The sub-pixel position determination unit
An integer N1 not exceeding Nx / αx;
An integer N2 not exceeding Ny / αy;
The scale factor βx in the row direction,
Scale factor βy in the column direction,
The covariance value Cov [p for the detection increase partial area shifted by p reproduction pixels in the row direction and q reproduction pixels in the column direction from the detection image partial area where the covariance value is maximum. ] [q]
Sub-pixel position is detected according to the number 2 expressed using

8. The information recording medium playback device according to claim 7, wherein
An information reproduction method for reproducing a two-dimensional data page including a marker pattern using a photodetector,
The marker pattern is a recording composed of recording pixels having the same polarity with the number of recording pixels of integers Nx and Ny in which the number of consecutive on pixels and off pixels is constant in each direction in the row direction and the column direction of each recording pixel. Composed of units,
An intermediate pattern obtained by replacing the recording unit with a single recording pixel having the same polarity as the pixel inside the recording unit is the same as the intermediate pattern central portion excluding the outer edge of the intermediate pattern, and the intermediate pattern central portion. The two-dimensional data page is configured such that a covariance value with a partial area inscribed in the boundary of the intermediate pattern having the two-dimensional pixel arrangement is 0,
Obtaining a partial detection image of a portion including the marker pattern;
A reference detection pattern generation step for generating a reference detection pattern;
A covariance value calculating step for obtaining a covariance value for a detection image partial area having the same size as the reference detection pattern included in the range of the partial detection image; and the detection image partial area having the maximum covariance value. A pixel unit position determination step for determining and determining a position in pixel units;
With respect to the outside of the detected image partial area where the covariance value determined in the pixel unit position determining step is maximum, the reproduction pixels of integer N1 not exceeding Nx / αx in the row direction and Ny / αy in the column direction A sub-pixel position for determining a sub-pixel position based on the covariance value obtained in the covariance value calculation step for the detected image partial area included in the area enlarged by the reproduction pixel of the integer N2 not exceeding N2. Detection step,
An information reproducing method characterized by comprising:
The information reproduction method according to claim 9,
In the sub-pixel position detecting step,
An integer N1 not exceeding Nx / αx;
An integer N2 not exceeding Ny / αy;
The scale factor βx in the row direction,
Scale factor βy in the column direction,
The covariance value Cov [p for the detection increase partial area shifted by p reproduction pixels in the row direction and q reproduction pixels in the column direction from the detection image partial area where the covariance value is maximum. ] [q] to detect the sub-pixel position according to the number 1 expressed by

An information recording medium reproducing method characterized by the above.
The information reproduction method according to claim 9,
The sub-pixel position detecting step includes an integer N1 not exceeding Nx / αx,
An integer N2 not exceeding Ny / αy;
The scale factor βx in the row direction,
Scale factor βy in the column direction,
The covariance value Cov [p] for the detection increase partial region in which p reproduction pixels are shifted in the row direction and q reproduction pixel positions are shifted in the column direction from the detection image partial region where the covariance value is maximum. sub-pixel position is detected according to Equation 2 using [q].

It is characterized by
The information recording medium reproducing method according to claim 9.
A method for generating a marker pattern recorded on a two-dimensional data page,
The marker pattern has a marker pattern center portion and a partial region inscribed in a boundary of the marker pattern excluding the marker pattern center portion,
Configuring the marker pattern so that the minimum connection length of the recording pixels is N pixels (N: a natural number of 2 or more) in at least one direction;
The covariance between the marker pattern center and the marker pattern shifted by N pixels in the one direction from the marker pattern center is zero, and there is no pixel shift from the marker pattern center and the marker pattern center. Generating a marker pattern so that the covariance value with the marker pattern of the case is maximized;
A marker pattern generation method characterized by the above.