Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
  • G11B7/0065—Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
  • G11B7/00772—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track on record carriers storing information in the form of optical interference patterns, e.g. holograms
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
  • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
  • G11B7/128—Modulators
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
  • G11C13/04—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using optical elements ; using other beam accessed elements, e.g. electron or ion beam
  • G11C13/042—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using optical elements ; using other beam accessed elements, e.g. electron or ion beam using information stored in the form of interference pattern
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/26—Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
  • G03H1/2645—Multiplexing processes, e.g. aperture, shift, or wavefront multiplexing
  • G03H1/265—Angle multiplexing; Multichannel holograms

Definitions

• the present invention relates to a holographic recording / reproducing apparatus for irradiating a holographic recording medium with object light and reference light, recording information as a hologram using the interference fringes, and reproducing the recorded information.
• the present invention relates to a method for searching for a hologram when reproducing information.
• Holographic recording / reproducing methods and apparatuses are one of large-capacity and high-speed storage technologies capable of storing large-capacity digital information.
• digital information is multiplex-recorded in page units as a data page composed of a two-dimensional bitmap image.
• Such a holographic recording / reproducing method and apparatus is an ultra-high-speed search function for instantly searching for specific data by making use of the volume property of a hologram, not only a high-speed, large-capacity storage function. , "Search playback” called “associative playback”.
• data pages are multiplex-recorded in page units, and spatial light modulation is performed on a holographic recording medium.
• the signal light modulated by the data image to be searched is radiated by a detector to emit diffracted light, and the data image given to the signal light is obtained from the diffracted light having the highest intensity among the obtained diffracted lights.
• the holographic search method in the holographic recording / reproducing method and apparatus described above detects diffracted light for each data page. Therefore, when a small data search is performed, the amount of diffracted light is reduced. There is a problem that the search accuracy (SNR) is reduced.
• the present invention has been made in view of the above-described problems, and has a hologram in which the data size used for search, the search accuracy is not reduced, or the search itself becomes impossible.
• An object of the present invention is to provide a search method and a holographic recording / reproducing apparatus for performing the search method.
• ON pixel and OFF pixel refer to a pixel that transmits light and a pixel that does not transmit light in a spatial light modulator, and the spatial light modulation in a recorded data page. Pixels corresponding to the “ON pixel” and “OFF pixel” displayed on the container!
• the present inventor has found that when recording a data page on a holographic recording medium, the data is recorded as block information for each data block obtained by equally dividing the data page into a plurality.
• the search data is displayed on the spatial light modulator in units of the data block, the signal light is modulated, and the holographic recording medium is irradiated. From the obtained diffracted light, a data page including block information is searched. By doing so, I was able to achieve the above objectives.
• Data block power Further, in each data block, a data image is formed by a coding method so that the number of ON pixels is constant.
• the spatial light modulator at least one search data corresponding to the data block is formed.
• the data image to be searched is coded by the coding method and displayed as block information, and the signal light is modulated from the block information.
• a hologram search method comprising specifying an address of a data block and a data page including a desired data image.
• a part of the data block in the data page is a search-dedicated data block, and the data image of the search-dedicated data block is smaller in the number of ON pixels than the data images in other data blocks.
• the beam diameter and the optical path of the signal light are adjusted so that the signal light substantially passes only the search data block displayed on the spatial modulator.
• the hologram search method according to any one of (1) to (3).
• the block information is simultaneously displayed on all the search data blocks in the spatial light modulator, and the data including the block information is obtained from the diffracted light having the highest intensity among the plurality of obtained diffracted lights.
• Data block power, and each data block has an ON pixel number different for each data block.
• a data image is formed by the method, and in the spatial light modulator, the same data image to be searched is encoded by the encoding method in all of the search data blocks corresponding to the data block.
• the data signal is modulated according to the block information, and the data block including the data image to be searched and the address of the data page are specified based on the amount of the obtained diffracted light.
• Hologram search method for irradiating light, emitting
• the object optical system and the reference optical system for guiding the object light and the reference light to the holographic recording medium, and the digital information to be recorded, which is provided in the object optical system, is a two-dimensional bit map image.
• a spatial light modulator capable of modulating the object light by displaying the data as a data page, and a plurality of holograms recorded on the holographic recording medium when the holographic recording medium is irradiated with signal light from the object optical system.
• a search imaging device that receives diffracted light, a signal processing circuit that processes an output signal of the search imaging device, and a reproduction device that receives diffracted light generated when the reference optical system irradiates with reproduction reference light.
• a spatial light modulator wherein the spatial light modulator encodes the digital information for each data block obtained by equally dividing the data page into a plurality of data blocks.
• the data image to be searched can be encoded by the same encoding method as the data image, and can be displayed as block information.
• a holographic recording / reproducing apparatus wherein an address of a data page including the data image is specified based on a diffracted light having a maximum intensity.
• the spatial light modulator sets a part of the data block in the data page as a search-only data block, and converts a data image of the search-only data block into a data image in another data block.
• the holographic recording / reproducing apparatus according to (9) or (10), wherein the holographic recording / reproducing apparatus can be formed by a coding method having a larger number of ON pixels.
• the object optical system can adjust a beam diameter and an optical path of the signal light so that the signal light substantially passes only a search data block displayed on the spatial modulator.
• the holographic recording / reproducing apparatus according to any one of (9) to (11), wherein
• the spatial light modulator can simultaneously display the block information in all search data blocks in the spatial light modulator, and the signal processing circuit obtains the image sensor power for search.
• An object optical system and a reference optical system for guiding the object light and the reference light to the holographic recording medium, and a two-dimensional bit map image provided in the object optical system and for recording digital information to be recorded. This is displayed when the holographic recording medium is displayed as a powerful data page, thereby modulating the object light and the hologram is recorded, and the holographic recording medium is irradiated with the signal light from the object optical system.
• a search imaging device for receiving a plurality of diffracted lights, a signal processing circuit for processing an output signal of the search imaging device, and a diffracted light generated when the reference optical system is irradiated with reproduction reference light.
• a spatial light modulator wherein the spatial light modulator converts the digital information for each data block obtained by equally dividing the data page into a plurality of data pages.
• the data image to be searched can be displayed as a data image encoded by an encoding method having a different number of ON pixels, and the data image to be searched is encoded by the same encoding method as the data image to block information.
• the signal processing circuit is configured to specify a data block including a data image to be searched and an address of the data page from the amount of diffracted light obtained by the search imaging device.
• FIG. 1 is an optical system diagram showing a holographic recording / reproducing apparatus according to Embodiment 1 of the present invention.
• FIG. 2 is a plan view schematically showing a relationship between a data page displayed on a spatial light modulator or recorded on a holographic recording medium and data blocks constituting the same in the first embodiment.
• FIG. 3 is a plan view schematically showing a recorded data page and a search data block at the time of a search in Example 1;
• FIG. 4 is a plan view schematically showing a recorded data page and a search data block for searching the same in Example 2.
• FIG. 5 is a plan view schematically showing a recorded data page and a search data block for searching the same in Example 3.
• FIG. 6 is an optical system diagram showing a holographic recording / reproducing apparatus according to Embodiment 4.
• FIG. 7 is a plan view schematically showing a recorded data page in Example 5.
• FIG. 8 is a plan view schematically showing a search data block at the time of a search according to the fifth embodiment.
• FIG. 9 shows a clock signal output from a control device, a laser beam at the time of search, an operating state of a spatial light modulator and an image sensor for search, and a detection signal in relation to a signal level and time according to the fifth embodiment.
• FIG. 10 is a plan view schematically showing recorded data pages and search data blocks in Example 6.
• FIG. 11 is a plan view schematically showing a recorded data page in Example 7.
• FIG. 12 is a plan view schematically showing an image for each data block in the same data page.
• the digital information is multiplex-recorded in page units as a data page consisting of a two-dimensional bitmap image.
• the data page in the holographic recording medium is equally divided into a plurality of data blocks, and Is formed with a data image encoded by an encoding method such that the number of ON pixels in each data block is constant, and a data image to be searched is obtained by the spatial light modulator using the data image.
• the search data block corresponding to the block is encoded by the encoding method and displayed as block information, thereby modulating the signal light. From the diffracted light having the highest intensity among the obtained diffracted lights, The data image and the address of the reference light to be obtained are detected.
• Example 1 Example 1
• the holographic recording / reproducing apparatus 10 includes a laser light source 12, a beam splitter 14 for splitting laser light from the laser light source 12 into transmitted light as object light and reflected light as reference light, Object optical system 18 for guiding the light to a holographic recording medium (hereinafter referred to as a recording medium) 16, a reference optical system 20 for guiding the reference light to the recording medium 16, and reproduction from the reference optical system 20 to the recording medium 16.
• An imaging optical system 22 for receiving the diffracted light generated when the reference light is irradiated and reproducing the information, and a signal light emitted from the object optical system 18 to the recording medium 16 during the search.
• a search optical system 24 for receiving the generated diffracted light.
• the object optical system 18 includes a beam expander 18A for expanding the beam diameter of the object light transmitted through the beam splitter 14 in order with respect to the beam splitter 14 side force, and further increases the beam diameter by the beam expander 18A.
• a mirror 18B that reflects the enlarged object light at a right angle, and a two-dimensional bitmap image that is encoded according to the digital information to be recorded is displayed.
• a spatial light modulator 26 that modulates the object light or the signal light reflected by the mirror 18, and performs a Fourier transform on the object light to which the bitmap image is added by the spatial light modulator 26, and And a Fourier lens 18C for condensing and entering the holographic recording medium 16.
• the reference optical system 20 reflects the reference light reflected by the beam splitter 14 in the direction of the recording medium 16 in the order of the beam splitter 14 side force, and deflects the reflection angle in a plurality of steps. And a rotating mirror 20A rotatable so that the reference light can selectively travel to any one of a plurality of optical paths 35A, 35B, 35C, and so on. And a lens group 20B for refracting the reference light so that the reference light is incident on the intersection with the object light in the vicinity of the recording medium 16.
• the imaging optical system 22 is configured to emit light when the reproduction reference light is irradiated from the optical path of the reference light.
• the image pickup device includes a reproducing image sensor 28 disposed on the optical path extending the folded light, and an imaging lens 22A disposed between the reproducing image sensor 28 and the recording medium 16.
• the search optical system 24 is provided on an optical path of diffracted light generated when the recording medium 16 is irradiated with signal light from the object optical system 18, and a search optical system for receiving the diffracted light is provided.
• the imaging device 30 includes: an imaging device 30; and an imaging lens 24A disposed on an optical path of diffracted light between the search imaging device 30 and the recording medium 16.
• reference numeral 32 indicates a control device
• reference numeral 34 indicates a signal processing circuit.
• the control device 32 displays the digital information to be recorded on the spatial light modulator 26 as a data page having a two-dimensional bitmap image capability.
• control device 32 causes the spatial light modulator 26 to divide a data page DP into a plurality of equally divided data blocks DB11 to DB33 (see FIG. 2). Are collectively referred to as a data block DB), and digital information to be recorded can be displayed as an encoded data image!
• the data image to be searched can be encoded by the same encoding method as the data image at the time of recording, and can be displayed as block information in a part or the front of the data blocks DB11 to DB33. It has been.
• a data block in which a data image to be searched is displayed as block information is referred to as a search data block DBS (see FIG. 3B).
• the data blocks DB11 to DB33 are each composed of a total of 16 pixels, 4 pixels in each of the vertical and horizontal directions. At the time of recording, the data blocks DB11 to DB33 correspond to the data page DP shown in FIG. Thus, the number of ON pixels in all the data blocks DB11 to DB33 is set to 6.
• the spatial light modulator 26 is controlled by the control device 32, for example, as shown in FIG. 3B, to a data other than the search data block DBS displaying the block information. All pixels in the data block DB can be set as OFF pixels!
• the signal processing circuit 34 is provided for each of the data blocks DB11 to DB33 in the diffracted light received by the search imaging device 30 when the data page DP recorded on the recording medium 16 is irradiated with the signal light.
• the intensity of the diffracted light that is, the amount of light, to detect the amount of light and Z or the data block of the maximum amount of light for each of the data blocks DB11 and DB33, and
• the data block DB including the search information, the data page DP, and the address of the reference beam when recording the data page DP can be specified!
• the data page DP is angularly multiplex-recorded on the recording medium 16 by rotating the rotating mirror 20A stepwise.
• the data block DB22 center data block in the data page DP as shown in FIG. A description will be given when searching for the data page DP.
• control device 32 displays the block information to be searched at the position of the central data block DB22 of the spatial light modulator 26, and uses this as a search data block DBS and other data blocks. All pixels of DB are turned off, and the state is as shown in Fig. 3 (B).
• the signal light emitted from the laser light source 12 and incident on the object optical system 18 is modulated by the spatial light modulator 26, passes through the Fourier lens 18 C, and converts the signal light into the recording medium 16. Irradiation.
• diffracted light corresponding to the reference light at the time of recording is emitted from the recording medium 16.
• a plurality of diffraction lights are generated from the recording medium 16. This enters the search imaging device 30 via the imaging lens 24A.
• the signal processing circuit 34 detects the maximum intensity diffracted light out of the plurality of incident diffracted lights, thereby identifying and recording the data page DP including the block information shown in Fig. 3 (B). Can be determined. Further, when the diffracted light incident on the search imaging element 30 has the maximum light intensity, the reference optical system 20 enters the recording medium 16 with the reproduction reference light incident on the recording medium 16 at the same incident angle as the detected reference light. From the medium 16, diffracted light corresponding to the data page DP containing the information of the data block DB22 is emitted, and is received by the imaging element for reproduction 28, whereby the information of the target data page DP is subjected to signal processing. It can be obtained from circuit 34.
• the noise component can be reduced and the search accuracy can be improved.
• Block information is simultaneously displayed on a plurality of data blocks, and “AND search is performed. "Or” OR search ".
• the data page DP2 uses one or more of the data blocks DB11 and DB33 to search-only data blocks in which (possible) block information used for search is displayed. DBO.
• the number of ON pixels is larger than that of the block information of other data blocks, and information obtained by image encoding by an encoding method is recorded.
• the number of ON pixels in the search-dedicated data block DBO is 10, whereas in other data blocks DB, the number of ON pixels is The number is six.
• the strength of a detection signal in a search is proportional to the number of ON pixels included in a search image. Therefore, in this embodiment, compared with a case where all surrounding data blocks are set to OFF pixels, , A large detection signal intensity can be obtained.
• the strength of the search signal that is, the SNR is improved
• the intensity of the detection signal can be increased.
• the number of ON pixels of the data-to-be-searched block DB0 is set to 10; therefore, as shown in FIGS. 3 (A) and 3 (B).
• the retrieval accuracy or the diffracted light amount is 10Z6 1.67 times on average on average.
• FIG. 5 Next, a third embodiment of the present invention shown in FIG. 5 will be described.
• the data page DP3 of the third embodiment is different from the data page DP2 of FIG. 4A in that the search-dedicated data block DB0 is an ON image in the search data block DBS of FIG. 3B.
• This method is different from that of the first embodiment in that the code and the OFF pixel are inverted.
• the same search signal strength and search accuracy as those in the second embodiment of FIGS. 4A and 4B are used.
• An advantage is that the amount of signal processing required for encoding the data block DB0 is reduced.
• the holographic recording / reproducing apparatus 40 according to the fourth embodiment differs from the holographic recording / reproducing apparatus 10 shown in FIG. 1 in that a beam expander 42 having a different configuration is used instead of the beam expander 18A. Except for this, the configuration is the same as that of the first embodiment.
• FIG. 6 the same components as those of the holographic recording / reproducing device 10 are denoted by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.
• the beam expander 42 in the fourth embodiment enlarges the beam diameter of the signal light so that the beam diameter of the signal light passes through only the center data block DB22 in the spatial light modulator 26. It is like that.
• the focal length of the lens 42B on the 8B side is shorter than the lens on the mirror 18B side in the beam expander 18A in the first embodiment.
• the search can be performed even if the beam diameter of the signal light at the time of the search is reduced, and the optical power density of the signal light used for the search is increased. Since the exposure time (determined by the sensitivity of the search imaging device 30) is reduced, the search speed can be improved.
• the block information of the data block DB22 is used as a search data block, as shown in FIG. ) —As shown in (I), the block information is sequentially displayed in the data blocks DB11 to DB33, that is, transmitted to the recording medium 16 as the sequentially searched data block DBS. It irradiates light.
• the timing of the emission of the laser beam, the switching of the frame in the spatial light modulator 26, and the detection of the light amount of the imaging element for search 30 are performed by the control device 32 as shown in FIG.
• the laser light may be continuously emitted during a series of searches, or may be turned ON / OFF for each search. However, it is preferable that both the laser light source 12 and the spatial light modulator 16 be ON when the detection window of the search imaging device 30 is ON (light amount detection state)! /.
• a clock signal corresponding to each of the data blocks DB11 to DB33 is generated from the control device 32.
• the laser light from the laser light source 12 is immediately emitted, and the spatial light modulator 16 Is displayed.
• the light amount detection window of the search imaging device 30 is opened.
• a detection signal as shown in FIG. 9 is obtained for a pixel (group) corresponding to the target data page in the search imaging device 30, and its signal intensity is obtained. It can be seen that the maximum value of is in data block DB22, and as a result, the search information is recorded in data block DB22. In the data blocks at other positions, the peak of the detection signal as shown in FIG. 9 does not appear! / ,.
• the information is reproduced by a normal reproduction method, that is, by irradiating the target data page DP with the reproduction reference light.
• Information can be reproduced from the reproduction image sensor 28.
• the number N of data pages is 9 when the number of data pages DP to be multiplexed is N.
• a faster search operation becomes possible.
• many hundreds and thousands of data pages are often multiplex-recorded. In this case, retrieval information can be found in a much shorter time than when these data pages are reproduced.
• the same data image to be retrieved is retrieved, for example, as shown in FIG.
• the data image is simultaneously displayed on all data blocks in the spatial light modulator 26 at the time of retrieval. That is, all of the data pages DP6 displayed on the spatial light modulator 26 at the time of the search are used as the search data block DBS.
• an image composed of all the same search data blocks DBS as shown in FIG. 10A is displayed on the spatial light modulator 26, and the signal light is modulated by this image to record on the recording medium.
• the object 16 is irradiated, only the hologram containing the image to be searched shown in FIG. 10B strongly diffracts the signal light and emits the reference light used for recording as diffracted light. If detected by 30, it is possible to specify the data page DP in which the image to be searched is included.
• the information of the retrieved data page DP is transmitted from the imaging optical system 22. Can be played.
• the information amount per data page is about several hundred kBytes. For example, if 1000 data pages are multiplexed, the information amount is about several hundred MB. .
• the information to be searched is narrowed down to one page (several hundred kBytes) of the 1000 data pages by the search operation for only one second. Even if the search is performed, the search time can be greatly reduced.
• the fifth embodiment requires optical search operations as many times as the number of data blocks in a data page. In addition, there is an advantage that even a data block can be specified.
• the sixth embodiment although data processing after decryption is required, only one optical search operation is required for a series of multiplex-recorded data pages.
• the former is often faster than the latter in terms of decoding, CPU processing speed, and optical system operation. Therefore, in the case where the number of data blocks in a data page is relatively small, the fifth embodiment is more advantageous.
• Embodiment 6 is more advantageous when the number of data blocks is large.
• the data page D recorded on the recording medium 16 is
• each data block DB includes a code block in which the number of ON pixels differs for each data block as shown in FIG.
• the data image is formed by the method.
• the same block information to be retrieved is displayed on all the data blocks in the spatial light modulator 26, and the signal light is modulated and irradiated onto the recording medium 16, as in the sixth embodiment. .
• the block information displayed in each search data block DBS is the same bitmap image due to the same difference in the power code.
• the search image sensor 30 detects the reference light corresponding to the data page containing the information to be searched, as in the sixth embodiment.
• the amount of light detected by the search image sensor 30, that is, the signal output indicates “in which data block the information to be searched is It depends on what power you belong to. That is, it is possible to determine not only which data page has the corresponding information but also which data block has a force in one search operation.
• the optical search operation in the same area (the area where a series of data pages is multiplexed) of the recording medium 16 is performed only once, and the search operation for decoding is performed. This eliminates the need for an operation, and enables faster retrieval than in any of the fifth and sixth embodiments. However, since the amount of encoding is different for each data block, the amount of operation required for encoding and decoding data is slightly increased.
• the hologram search method and holographic recording / reproducing apparatus of the present invention can input search data and detect diffracted light in data block units obtained by equally dividing a data page into a plurality of data pages.
• High-capacity storage that can be performed without a decrease in data size and that does not impair the search accuracy or make the search itself impossible even if the data size is small. Can be.

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• 2004
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