JP2006318586A - Hologram recording device and recording method of hologram recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording device and a hologram recording method which can shorten processing time for recording and reproducing processing of hologram and can reduce a load of a storage in which data to be recorded or reproduced is stored in recording and reproducing the hologram concerned. <P>SOLUTION: This is a hologram recording device which records data on recording area as a hologram by making coherent data beam and coherent reference beam corresponding to data to be recorded incident on a recording area of hologram medium. It is provided with; a data beam generation section which generates a data beam to be incident on each recording area smaller than recording area divided for each adjacent predetermined width in relative moving direction of a hologram medium; a data beam incident section to make data beam from the data beam generation section incident on each recording area; and a reference beam incident section to make reference beam incident on each recording area together with the data beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hologram recording apparatus and a hologram recording method of the hologram recording apparatus.

  As a hologram medium on which digital data is recorded as a hologram, for example, there is one provided by sealing a photosensitive resin (for example, photopolymer) with a glass substrate.

  When digital data is recorded on the hologram medium as a hologram, first, the laser beam from the laser device is split into two laser beams by a PBS (Polarization Beam Splitter). Then, by irradiating one laser beam (hereinafter referred to as a reference beam) and the other laser beam to an SLM (Spatial Light Modulator) in which digital data is formed as a two-dimensional gray image pattern, the second laser beam is irradiated. By irradiating the hologram medium with a laser beam (hereinafter referred to as a data beam) reflecting the information of the three-dimensional grayscale image pattern at a predetermined angle, digital data is recorded on the hologram medium as a hologram.

  More specifically, the photosensitive resin constituting the hologram medium has a finite number of monomers and is irradiated with a laser beam (hereinafter abbreviated as a laser beam) composed of a reference beam and a data beam. The monomer changes into a polymer according to the energy of the laser beam and the irradiation time. And when this monomer changes to a polymer, an interference fringe made of a polymer corresponding to the energy of the laser beam is formed. Therefore, when this interference fringe is formed in the hologram medium, digital data is recorded as a hologram. Thereafter, the remaining monomer moves (diffuses) to the place where the monomer is consumed. FIG. 2 schematically shows a state in which the monomer changes into a polymer in accordance with the energy of the laser beam in the hologram medium.

  Further, when a large amount of digital data is recorded on the hologram medium, it is possible to perform so-called angle multiplex recording in which a large number of holograms are formed by changing the incident angle of the reference beam to the hologram medium. For example, it is assumed that one hologram formed on the hologram medium is referred to as a page, and a multiplexed hologram including a large number of pages is referred to as a book. FIG. 3 is a diagram schematically showing a book and a page in angle multiplex recording. As shown in FIG. 3, in angle multiplexing recording, for example, a 10-page hologram is formed by changing the incident angle of the reference beam for one book. As described above, the recording of digital data on the hologram medium makes it possible to record a large amount of digital data by angle multiplexing recording.

  Hereinafter, an example of forming a two-dimensional gray image pattern from digital data at the time of hologram recording will be described in detail with reference to FIGS. 4 (a), 5, and 6. FIG.

  For example, digital data to be subjected to hologram recording is sequentially transmitted to the encoder 107 from a host device (not shown) such as a PC (Personal Computer). The encoder 107 is provided to perform encoding processing such as addition of error correction code and modulation on digital data. Since the encoding process by the encoder 107 requires a predetermined processing time, the digital data sequentially transmitted from the host device is temporarily stored in the buffer memory 110. Then, the encoder 107 reads digital data from the buffer memory 110 as needed and performs an encoding process. Data encoded by the encoder 107 (hereinafter referred to as encoder output bit data (FIG. 5)) is transmitted to the mapping processing unit 108.

  The SLM 109 has 4 × 4 spatial light modulation elements (a1 to d4) arranged two-dimensionally as shown in FIG. 6, for example. One spatial light modulator is provided corresponding to 1-bit data. For example, when the logical value of 1-bit data is “1”, it is bright (dark), and when it is “0”, it is dark (light). It is an element that reproduces. Note that the SLM 109 generally has a large amount (for example, 1280 × 1280 = 1638400) of spatial light modulators. However, for the sake of convenience of explanation, the SLM 109 will be described using the SLM 109 having 4 × 4 spatial light modulators. To do.

  The mapping processor 108 is provided to sequentially arrange each 1-bit data constituting the encoder output bit data corresponding to each spatial light modulator (a1 to d4) (hereinafter referred to as mapping process). Since the mapping processing by the mapping processing unit 108 is performed for each bit data, a predetermined processing time is required. For this reason, the encoder output bit data is temporarily stored in the buffer memory 111. Then, the mapping processing unit 108 reads out one bit data at a time from the buffer memory 111 and performs mapping processing.

  As a result, 1-bit data is sequentially arranged in the spatial light modulator of the SLM 109 as shown in the unit page arrangement data in FIG. Then, each spatial light modulation element reproduces light or dark according to the logical value of 1-bit data, whereby the two-dimensional gray image pattern of FIG. 5 is formed on the SLM 109.

  When digital data is reproduced from a hologram medium (hereinafter referred to as hologram reproduction), a reference beam is irradiated onto the hologram indicating the digital data at the same incident angle as when the hologram is formed. A reference beam (hereinafter referred to as a reproduction beam) diffracted by the hologram is received by an image sensor or the like. The reproduction beam received by the image sensor or the like has a two-dimensional gray image pattern indicating the digital data described above. The digital data can be reproduced by demodulating the digital data from the two-dimensional gray image pattern with a decoder or the like. In addition, the light amount of the reproduction beam in such hologram reproduction must be a light amount of a certain level or more that allows the two-dimensional gray image pattern to be reproduced by an image sensor or the like. Therefore, the hologram that diffracts the reference beam must have a diffraction efficiency such that the diffraction efficiency indicating the ratio of the light amount of the reproduction beam to the light amount of the reference beam is equal to or greater than a predetermined value.

  Hereinafter, an example of hologram reproduction from a hologram medium on which the two-dimensional gray image pattern shown in FIG. 5B is recorded will be described in detail with reference to FIGS. 4B, 7 and 8. FIG.

  As shown in FIG. 8, the image sensor 127 includes light receiving cells (a1 to d4) that are the same number 4 × 4 as the spatial light modulators included in the SLM 109 described above and are similarly arranged. The image sensor 127 is provided to output to the filter 129 an analog electric signal corresponding to the light amount of the received reproduction beam in the order of the arrangement of the light receiving cells (a1 to d4). First, the image sensor 127 receives a reproduction beam diffracted by a hologram showing a two-dimensional gray image pattern. Then, each light receiving cell of the image sensor 127 becomes bright or dark depending on the amount of the reproduction beam, and as a result, the two-dimensional gray image pattern shown in FIG. 7 is reproduced on the image sensor 127. The image sensor 127 outputs an analog electrical signal (FIG. 7, image sensor output analog electrical signal) corresponding to the light amount of the reproduction beam to the filter 129 in the order of the arrangement of the light receiving cells (a1 to d4). As described above, the image sensor 127 outputs the analog electric signal of each light receiving cell to the filter 129 in the order of arrangement, so that information indicating the light amount of the reproduction beam of each light receiving cell is temporarily recorded in the buffer memory 131. Become. Then, the image sensor 127 reads information indicating the light amount of one light receiving cell from the buffer memory 131 as needed, and outputs an analog electric signal corresponding to the light amount to the filter 129.

  The filter 129 performs a filtering process on the analog electric signal in order to improve the separability of the binarization process by the decoder 130. As this filtering process, for example, level correction of an analog electric signal is performed.

The decoder 130 performs binarization processing on the analog electric signal based on the reference voltage Vref (FIG. 7). Then, the decoder 130 performs decoding processing such as demodulation and error correction based on the error correction code on the signal indicating the result of the binarization processing (the binarized signal in FIG. 7). Since the decoding process by the decoder 130 requires a predetermined processing time, the binarized signal is temporarily stored in the buffer memory 132. Then, the decoder 130 reads the binarized signal from the buffer memory 132 as needed and performs decoding processing. As a result of the decoding process performed by the decoder 130, the digital data is reproduced.
JP2004-177958 JP 2004-272268 A

  However, in order to record a large amount of digital data at a time, the SLM 109 generally has a large amount of spatial light modulation elements and consumes a large amount of buffer memory for forming a two-dimensional gray image pattern. was there. In addition, a long processing time (for example, mapping processing time) is required to form a two-dimensional gray image pattern, resulting in a problem that the processing time for hologram recording becomes long. In particular, when holographic recording of stream data is performed, the processing time problem may become serious. As means for solving the problem of the processing time, it is possible to shorten the processing time by pipelining the encoding process and the mapping process described above. However, in this case, there is a problem that a large amount of buffer memory is consumed.

  Further, in hologram reproduction accompanying the above-described hologram recording, there is a problem that a large amount of buffer memory is consumed when analog electric signals are output based on the brightness of a two-dimensional grayscale image pattern. Further, it takes a lot of time to output an analog electric signal based on the brightness of the two-dimensional grayscale image pattern, and there is a possibility that the processing time of hologram reproduction becomes long.

  Accordingly, the present invention provides a hologram recording apparatus capable of reducing the processing time for the hologram recording / reproducing process and reducing the load on the buffer memory for storing data to be recorded / reproduced in the hologram recording / reproducing process, An object of the present invention is to provide a hologram recording method for a hologram recording apparatus.

  In order to solve the above-mentioned problems, a coherent data beam corresponding to data to be recorded and a coherent reference beam are incident on a recording area of a hologram medium, and the data is used as a hologram. A hologram recording apparatus for recording in a recording area of the hologram medium, wherein when recording the data, each recording smaller than the recording area, which is divided for each predetermined width in the relative movement direction of the hologram medium A data beam generating unit that generates a data beam incident on the region, and a data beam incident unit that inputs the data beam generated by the data beam generating unit to each recording region of the hologram medium; Together with the data beam from the data beam incident portion, a reference beam is applied to each recording area of the hologram medium. A reference beam incident portion for morphism, characterized by comprising a.

  In addition, a coherent data beam corresponding to data to be recorded and a coherent reference beam are incident on the recording area of the hologram medium, and the data is recorded as a hologram in the recording area of the hologram medium. A hologram recording method of a hologram recording apparatus, wherein, when recording the data, for each recording area smaller than the recording area, divided for each predetermined width adjacent in the relative movement direction of the hologram medium An incident data beam is generated, the generated data beam is incident on each recording area of the hologram medium, and the reference beam is incident on each recording area of the hologram medium together with the data beam. It is characterized by.

  According to the present invention, a hologram recording apparatus capable of shortening the processing time for the hologram recording / reproducing process and reducing the load on the storage device for storing data to be recorded / reproduced in the hologram recording / reproducing process, A hologram recording method of a hologram recording apparatus can be provided.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Overall Configuration of Hologram Recording Device ===
The hologram recording apparatus according to the present invention will be described with reference to FIGS. 1 and 9 to 15. FIG. 1 is a functional block diagram showing an example of the entire configuration of a hologram apparatus to which a hologram recording apparatus according to the present invention is applied. FIG. 9 is a detailed view of the laser beam generator (data beam generator) 26 shown in FIG. FIG. 10 is a detailed view of the reference beam generating unit (reference beam incident unit) 32 shown in FIG. FIG. 11 is a diagram showing the beam shape of the laser beam generated by the laser beam generator 26 shown in FIG. FIG. 12 is a diagram showing the beam shape of the reference beam generated by the reference beam generator 32 shown in FIG. FIG. 13 is a diagram showing the filters 39 (data beam limiting unit) and 40 (reference beam limiting unit) shown in FIG. FIG. 14 is a detailed view of the LCD (Liquid Crystal Display / dot pattern generator) 9 shown in FIG. FIG. 15 is a schematic diagram showing each recording area of the hologram medium 22.

  The hologram medium 22 is made of a photosensitive resin (eg, photopolymer, silver salt emulsion, dichromated gelatin, photoresist, etc.) that can store data as a hologram, and the photosensitive resin is sealed with a glass substrate. Has been. As will be described later, the hologram medium 22 has an area (see FIG. 15; hereinafter referred to as a recording area) where a one-dimensional gray pattern is recorded as a hologram. Each recording area is sequentially arranged in a spiral form, for example, from the inner circumference side to the outer circumference side of the hologram medium 22. Then, when the hologram medium 22 moves in the hologram medium moving direction, for example, holograms are sequentially recorded from the inner peripheral recording area to the outer peripheral recording area. In the present embodiment, the recording area on the innermost circumference side of the hologram medium 22 is referred to as a first recording area, and the recording area on the outermost circumference side is referred to as a final recording area.

  Further, the hologram medium 22 has a reflector 22 (a) that reflects a laser beam (hereinafter referred to as a servo laser beam) from the servo laser device 19. On the reflector 22 (a), prepits indicating address information corresponding to each recording area are formed in advance, as in the land prepit system used in, for example, a DVD (Digital Versatile Disk). In addition, a groove wobble for controlling the moving speed of a hologram medium 22 (to be described later) and the angular velocities of spin mirrors (rotating mirror type optical deflectors) 43 and 48 is formed in advance on the reflecting plate 22 (a).

  The hologram apparatus includes a CPU (Central Processing Unit) 1, a memory 2, a connection terminal 4, an interface 3, buffer memories 5, 33, 34, 37 and 38, a recording / reproduction determination unit 6, an encoder 7, a mapping processing unit 8, and an LCD 9. , Laser device 10, first shutter 11, first shutter control unit 12, half-wave plate 30, PBS (Polarization Beam Splitter) 13, 35 (data beam incident unit), 36, second shutter 14, second shutter control unit 15, laser beam generation unit 26, spin mirror control unit 46, objective lens 21 (data beam incident unit), filters 29, 39, 40, galvo mirror (reference beam changing unit) 16, galvo mirror Control unit (reference beam changing unit) 17, reference beam generating unit 32, scanner lens 20, servo laser device 19, dichroic mirror 18, detector 23, disk control unit 24, disk drive unit 25, PLL (Phase Locked Loop) circuit 51, oscillation circuit 52, line image sensor 27, line image sensor control unit 28, decoder 31 Have

In the servo laser device 19, for example, when the hologram device is started, a servo laser beam is incident on the dichroic mirror 18 so as to irradiate the prepit / groove wobble formed on the reflection plate 22 (a) of the hologram medium 22. The servo laser beam from the servo laser device 19 is a beam having a predetermined wavelength that does not affect the photosensitive resin of the hologram medium 22. For example, in the present embodiment, a blue laser beam is used as the laser beam emitted from the laser apparatus 10, and a red laser beam having a longer wavelength than the blue laser beam is used as the servo laser beam. It is assumed that the servo laser device 19 keeps the servo laser beam incident on the dichroic mirror 18 while the hologram device is activated.
The dichroic mirror 18 reflects the servo laser beam emitted from the servo laser device 19 and makes it incident on the objective lens 21. At this time, the reflection angle of the servo laser beam by the dichroic mirror 18 is set so that the servo laser beam is incident on the hologram medium 22 perpendicularly (direction Y3 in FIG. 1).

The PBS 36 receives the servo laser beam after irradiating the prepit / groove wobble formed on the reflection plate 22 (a) of the hologram medium 22, and causes the servo laser beam to enter the detector 23.
The detector 23 is composed of, for example, a photodetector (not shown) divided into four, and a servo laser beam from the PBS 36 is incident thereon. Then, the detector 23 detects address information based on the servo laser beam irradiated with the prepits and transmits it to the CPU 1. The detector 23 generates a wobble signal corresponding to the frequency of the groove wobble based on the servo laser beam irradiated with the groove wobble, and transmits the wobble signal to the PLL circuit 51.

The oscillation circuit 52 generates a clock with a predetermined frequency and transmits it to the PLL circuit 51. As the oscillation circuit 52, for example, a crystal oscillation circuit or an LC oscillation circuit can be used.
The PLL circuit 51 detects the phase difference between the clock having a predetermined frequency from the oscillation circuit 52 and the wobble signal from the detector 23. The PLL circuit 51 generates a clock (hereinafter referred to as a reference CLK) that is accurately synchronized with the wobble signal by controlling a VCO (Voltage Control Osilator, not shown) and a loop in the circuit. Then, the PLL circuit 51 transmits the generated reference CLK to the disk control unit 24 and the spin mirror control unit 46.

  The disk control unit 24 transmits an instruction signal to the disk drive unit 25 to servo-control the moving speed of the hologram medium 22 based on the reference CLK from the PLL circuit 51. Further, based on the instruction signal from the CPU 1, the disk control unit 24 transmits an instruction signal to the disk drive unit 25 so as to irradiate the servo laser beam to the pre-pits indicating the address information corresponding to the instruction signal. The servo control by the disk control unit 24 is performed so as to record the hologram from the first recording area to the final recording area of the hologram medium 22 shown in FIG.

The interface 3 is interposed between the host device (not shown) such as a PC connected via the connection terminal 4 and the hologram device for transmitting and receiving data.
The buffer memory 5 stores an instruction signal for hologram recording (hereinafter referred to as a recording instruction signal) transmitted from the host device. The buffer memory 5 stores data that is a target of hologram recording. The buffer memory 5 stores an instruction signal for reproducing a hologram (hereinafter referred to as a reproduction instruction signal) transmitted from the host device.

  The recording / reproduction determining unit 6 determines whether or not a recording instruction signal / reproduction instruction signal is recorded in the buffer memory 5 at a predetermined timing. When the recording / reproducing determining unit 6 determines that the recording instruction signal is stored in the buffer memory 5, the recording / reproducing determining unit 6 transmits an instruction signal to the CPU 1 to start hologram recording by the hologram device, and encodes the data to be subjected to hologram recording. 7 is transmitted. Then, the recording / reproducing determination unit 6 transmits information on the amount of data to be recorded on the hologram medium 22 to the CPU 1. When the recording / reproduction determining unit 6 determines that a reproduction instruction signal is stored in the buffer memory 5, the recording / reproduction determining unit 6 transmits an instruction signal for starting hologram reproduction by the hologram device to the CPU 1.

In the buffer memory 37, data to be subjected to hologram recording from the buffer memory 5 is stored via the encoder 7.
The encoder 7 sequentially reads data from the buffer memory 37 and performs encoding processing such as addition of error correction codes and modulation. Then, the encoder 7 transmits the encoded data (hereinafter referred to as encoder output bit data) to the mapping processing unit 8.

The buffer memory 33 stores the encoder output bit data from the encoder 7 via the mapping processing unit 8.
The mapping processing unit 8 reads out the encoder output bit data stored in the buffer memory 33 in units of, for example, 10 bits constituting the one-dimensional gray pattern, and transmits it to the LCD 9.

  The LCD 9 is composed of ten liquid crystals (liquid crystals A to J) arranged in the + Y3 direction of FIG. Each liquid crystal composing the LCD 9 contains liquid crystal molecules, and the orientation of the liquid crystal molecules is changed by applying a voltage. Each liquid crystal is provided corresponding to the logical value of 1-bit encoder output bit data. Hereinafter, the operation of the LCD 9 will be described in detail. The LCD 9 applies a voltage to the liquid crystal corresponding to the 1-bit encoder output bit data when the logical value of the 1-bit encoder output bit data is “0”, for example. The orientation of the liquid crystal molecules in the liquid crystal to which the voltage is applied is changed by the voltage, and the laser beam from the laser beam generator 26 is shielded (dark (light)). On the contrary, when the logical value of the 1-bit encoder output bit data is “1”, the LCD 9 does not apply a voltage to the liquid crystal corresponding to the 1-bit encoder output bit data. Therefore, the laser beam from the laser beam generating unit 26 is transmitted (bright (dark)) through the LCD 9. As a result, the laser beam after passing through the LCD 9 becomes a laser beam (hereinafter referred to as a data beam) in which a one-dimensional light (dark) dark (light) pattern is reflected in the + Y3 direction in FIG. The LCD 9 may be a simple matrix type STN (Super Twisted Nematic) type or DSTN (Dual-scan STN) type LCD, or an active matrix type LCD such as a TFT (Thin Film Transistor). In this embodiment, the mapping processing unit 8 and the LCD 9 are provided so as to process the encoder output bit data in units of 10 bits. However, the present invention is not limited to this. In order to further reduce the amount of encoder output bit data stored in the buffer memory 33, processing may be performed in smaller bit units. Further, although the LCD 9 that transmits or blocks the laser beam from the laser beam generator 26 is used, the present invention is not limited to this. For example, the above-described SLM may be used instead of the LCD. In that case, the spatial light modulation elements are provided in the order of the arrangement of the liquid crystals.

  The laser device 10 makes a laser beam excellent in temporal coherence and spatial coherence incident on the first shutter 11. As the laser device 10, for example, a helium neon laser, an argon neon laser, a helium cadmium laser, a semiconductor laser, a dye laser, or a ruby laser is used to form a hologram on the hologram medium 22.

  The CPU 1 performs overall control of the hologram device. When the CPU 1 receives the instruction signal based on the recording instruction signal from the recording / reproduction determining unit 6, the CPU 1 reads out address information corresponding to the recording area where the hologram was last recorded in the previous hologram recording from the memory 2. Then, the CPU 1 calculates a recording area for starting hologram recording (hereinafter referred to as a start recording area), and reads address information corresponding to the start recording area from the memory 2. The CPU 1 transmits an instruction signal for moving the hologram medium 22 to the disk control unit 24 so as to irradiate the servo laser beam from the servo laser device 19 to the pre-pit indicating the address information corresponding to the start recording area. Note that the address information calculated by the detector 23 based on the servo laser beam irradiated with the pre-pits is transmitted to the CPU 1 as needed.

  Further, the CPU 1 reads information on the incident angle of the reference beam (hereinafter referred to as incident angle information) from the memory 2 when the hologram was recorded last in the previous hologram recording. Then, the CPU 1 calculates the incident angle of the reference beam in the hologram recording based on the incident angle information from the memory 2. Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 17 so that the reference beam is incident at the calculated incident angle.

  Further, the CPU 1 calculates the number of holograms to be recorded on the hologram medium 22 in the present hologram recording based on the data amount information from the recording / reproduction determining unit 6. Next, the CPU 1 calculates a recording area in which the hologram is recorded last in the hologram recording. Then, the CPU 1 reads out address information corresponding to the recording area in which the last hologram is recorded from the memory 2. Then, the CPU 1 transmits an instruction signal for opening the first shutter 11 and the second shutter 14 to the first shutter control unit 12 and the second shutter control unit 15, respectively. As a result, hologram recording on the hologram medium 22 is started.

  Further, the CPU 1 determines whether the address information from the detector 23 matches the address information corresponding to the final recording area of the hologram medium 22. When the CPU 1 determines that the address information from the detector 23 matches the address information corresponding to the final recording area, the CPU 1 sends an instruction signal for closing the first shutter 11 to the first shutter control unit 12. Send. Then, the CPU 1 reads out address information corresponding to the first recording area from the memory 2. Next, the CPU 1 transmits an instruction signal for moving the hologram medium 22 to the disk control unit 24 so as to irradiate the servo laser beam to the prepits indicating the address information corresponding to the first recording area. Further, the CPU 1 calculates the incident angle of the reference beam based on the incident angle information from the memory 2 and transmits an instruction signal to the galvo mirror control unit 17 so that the reference beam is incident at the calculated incident angle. Note that the incident angle of the reference beam calculated by the CPU 1 at this time is different from the incident angle of the reference beam used in the previous hologram recording. That is, the incident angle information includes information on the incident angle of the reference beam used in the previous hologram recording.

  When the hologram recording based on the instruction signal from the recording / reproduction determining unit 6 is completed, the CPU 1 performs the first shutter 11 and the second shutter 14 on the first shutter control unit 12 and the second shutter control unit 15. An instruction signal for closing each is transmitted. As a result, hologram recording on the hologram medium 22 is completed.

  In addition, when the CPU 1 receives an instruction signal based on the reproduction instruction signal from the recording / reproduction determination unit 6, the servo laser device is applied to the prepit indicating the address information corresponding to the instruction signal formed on the hologram medium 22. In order to irradiate the servo laser beam from 19, an instruction signal for moving the hologram medium 22 is transmitted to the disk control unit 24. Further, when the CPU 1 receives the instruction signal from the recording / reproduction determination unit 6, the CPU 1 transmits an instruction signal for opening the first shutter 11 to the first shutter control unit 12 and the second shutter control unit 15. An instruction signal for closing the second shutter 14 is transmitted. Further, the CPU 1 transmits an instruction signal to the galvo mirror control unit 17 so that the galvo mirror control unit 17 performs the deflection angle control of the galvo mirror 16 based on the incident angle information from the memory 2. As a result, hologram reproduction from the hologram medium 22 is started. When determining that a predetermined time has elapsed in the hologram reproduction process, the CPU 1 transmits an instruction signal for closing the first shutter 11 to the first shutter control unit 12. As a result, the hologram reproduction from the hologram medium 22 is completed. Note that the CPU 1 may end the reproduction process based on a signal based on the determination result from the line image sensor control unit 28.

  The memory 2 stores in advance program data for the CPU 1 to perform the processing described above. Further, address information corresponding to each recording area of the hologram medium 22 is recorded in the memory 2 in advance. The memory 2 stores address information corresponding to the recording area where the last hologram was recorded in the previous hologram recording. Further, the memory 2 stores the incident angle information of the reference beam when the hologram is recorded last in the previous hologram recording. Further, the incident angle information stored in the memory 2 stores information on the incident angle of the reference beam used in the previous hologram recording. The memory 2 is composed of a nonvolatile memory element (for example, an EEPROM (Electronically Erasable and Programmable Read Only Memory)) that can repeatedly write and read data by electrically erasing the data.

  The first shutter control unit 12 performs control for opening the first shutter 11 or closing the first shutter 11 based on an instruction signal from the CPU 1. Further, the first shutter control unit 12 performs control for closing the first shutter 11 based on the instruction signal from the line image sensor control unit 28. The first shutter control unit 12 transmits an open state instruction signal to the first shutter 11 when opening the first shutter 11. The first shutter control unit 12 transmits a closed state instruction signal to the first shutter 11 when the first shutter 11 is closed.

The first shutter 11 enters an open state based on an open state instruction signal from the first shutter control unit 12. Further, the first shutter 11 enters a closed state based on a closed state instruction signal from the first shutter control unit 12. When the first shutter 11 is closed, the laser beam from the laser device 10 is blocked from entering the half-wave plate 30.
The half-wave plate 30 is provided with a predetermined inclination in order to determine the angle at which the laser beam emitted from the laser device 10 is incident on the PBS 13. The predetermined inclination of the half-wave plate 30 is determined so that the separation ratio when the laser beam is separated into two laser beams by the PBS 13 is a desired ratio.
The PBS 13 separates the laser beam from the half-wave plate 30 into two laser beams. One laser beam separated by the PBS 13 is incident on the second shutter 14. The other laser beam (reference beam) is incident on the galvo mirror 16.

The second shutter control unit 15 performs control for opening or closing the second shutter 14 based on an instruction signal from the CPU 1. The second shutter control unit 15 transmits an open state instruction signal to the second shutter 14 when the second shutter 14 is opened. The second shutter control unit 15 transmits a closed state instruction signal to the second shutter 14 when the second shutter 14 is closed.
The second shutter 14 is in an open state based on the open state instruction signal from the second shutter control unit 15. Further, the second shutter 14 is closed based on a closed state instruction signal from the second shutter control unit 15. When the second shutter 14 is closed, one laser beam from the PBS 13 is blocked from entering the laser beam generator 26.

  The laser beam generator 26 includes a beam expander 46 (beam generator), a collimator lens 47 (first collimator lens), a spin mirror 48, a spin mirror driver 49, and a collimator lens shown in FIGS. 9 (a) to 9 (c). 50 (second collimator lens). The beam expander 46 expands one laser beam from the second shutter 14 in the X1 direction and the Y1 direction as indicated by broken lines in FIGS. 9 (a) and 9 (b). The collimator lens 47 deflects the laser beam from the beam expander 46 into a parallel beam and makes the deflected laser beam incident on the spin mirror 48. As a result, the beam shape of the laser beam incident on the spin mirror 48 from the collimator lens 47 becomes the beam shape shown in FIG. Note that the length of the laser beam in the Y1 direction in FIG. 11 is substantially the same as the length of each recording area in the hologram medium moving direction, for example. The spin mirror drive unit 49 rotates the spin mirror 48 at a predetermined angular velocity in the spin mirror rotation direction (FIG. 9C) based on the instruction signal from the spin mirror control unit 46.

  The spin mirror 48 has eight incident surfaces (FIG. 9 (a)) on which the laser beam is incident. When viewed from the front shown in FIGS. 9 (b) and 9 (c), the spin mirror 48 has a regular octagonal shape. ing. The spin mirror 48 is rotated at a predetermined angular velocity in the spin mirror rotation direction by the spin mirror driving unit 49, and sequentially deflects the incident laser beam. The rotation and deflection of the spin mirror 48 are performed so that the laser beam emitted from the spin mirror 48 repeatedly irradiates the recording area in the direction of FIG. The collimator lens 50 deflects the laser beam from the spin mirror 48 into a parallel beam and makes the deflected laser beam enter the LCD 9. As a result, the laser beam from the collimator lens 50 scans the LCD 9 in the direction of FIG. 9C and FIG. 14 + Y3, and a data beam reflecting a one-dimensional light / dark pattern is generated.

The galvo mirror 16 deflects the reference beam from the PBS 13 and makes the reference beam incident on the reference beam generator 32.
The galvo mirror control unit 17 controls the deflection angle of the galvo mirror 16 so as to determine the incident angle of the reference beam deflected by the galvo mirror 16 to the hologram medium 22 based on the instruction signal from the CPU 1. The deflection angle control of the galvo mirror 16 by the galvo mirror control unit 17 is also performed in the hologram recording from the final recording area to the first recording area of the hologram medium 22 described above. A large number of holograms are recorded on the hologram medium 22 by angle multiplex recording based on the result of the deflection angle control.

  Further, at the time of reproduction from the hologram medium 22, the carbo mirror controller 17 controls the deflection angle of the galvo mirror 16 so that the reference beam is incident on the hologram formed on the hologram medium 22. The deflection angle control of the carbo mirror 16 at the time of hologram reproduction by the carbo mirror control unit 17 is performed by using the reference beam at the same angle as the incident angle of the reference beam when the data to be reproduced is recorded on the hologram medium 22 as a hologram. It is executed so as to be incident on the hologram medium 22.

  The reference beam generator 32 includes a beam expander 41 (beam generator), a collimator lens 42 (first collimator lens), a spin mirror 43, a spin mirror driver 44, and a collimator lens shown in FIGS. 10 (a) to 10 (c). 45 (second collimator lens). The beam expander 41 expands the reference beam from the galvo mirror 16 in the X2 direction and the Y2 direction, respectively, as indicated by broken lines in FIGS. 10 (a) and 10 (b). The collimator lens 42 deflects the reference beam from the beam expander 41 into a parallel beam, and makes the deflected reference beam incident on the spin mirror 43. As a result, the beam shape of the reference beam incident on the spin mirror 43 from the collimator lens 42 becomes the beam shape shown in FIG. Incidentally, the length of the reference beam in the direction Y2 in FIG. 12 is substantially the same as the length of each recording area in the moving direction of the hologram medium, for example, as in the beam shape of the laser beam in FIG. The spin mirror drive unit 44 rotates the spin mirror 43 at a predetermined angular velocity in the spin mirror rotation direction (FIG. 10C) based on the instruction signal from the spin mirror control unit 46.

  The spin mirror 43 has eight incident surfaces (FIG. 10 (a)) on which the reference beam is incident, and has a regular octagonal shape when viewed from the front shown in FIGS. 10 (b) and 10 (c). ing. The spin mirror 43 is rotated at a predetermined angular velocity in the spin mirror rotation direction by the spin mirror driving unit 44 and sequentially deflects the incident reference beam. The rotation and deflection of the spin mirror 43 are performed so that the reference beam emitted from the spin mirror 43 repeatedly irradiates the recording area in the direction of FIG. 10 (c) + Z1. The collimator lens 45 deflects the reference beam from the spin mirror 43 into a parallel beam, and causes the deflected reference beam to enter the scanner lens 20.

  Based on the reference CLK from the PLL circuit 51, the spin mirror control unit 46 transmits an instruction signal to the spin mirror driving units 44 and 49 to rotate the spin mirrors 43 and 48 at a predetermined angular velocity, respectively. The rotation control of the spin mirrors 43 and 48 by the spin mirror control unit 46 includes a period in which the reference beam / laser beam is incident on one incident surface and a reference beam and a data beam on one recording area of the hologram medium 22. The incident period is set to be the same period. That is, the rotation control of the spin mirrors 43 and 48 by the spin mirror control unit 46 and the movement speed control of the hologram medium 22 by the disk control unit 24 are in a relative relationship.

  The PBS 35 reflects the data beam from the LCD 9 and causes the data beam to enter the objective lens 21 via the PBS 36 and the dichroic mirror 18. At this time, the reflection angle of the data beam by the PBS 35 is set so that the data beam is incident on the hologram medium 22 perpendicularly (direction Y3 in FIG. 1).

  The objective lens 21 collects the data beam from the dichroic mirror 28 and makes it incident on the filter 39. Further, the objective lens 21 receives a beam (hereinafter referred to as a reproduction beam), which is obtained by diffracting the reference beam incident on the recording area by the hologram, from the filter 39 during hologram reproduction. Then, the objective lens 21 expands the reproduction beam from the filter 39 and makes it incident on the line image sensor 27 via the dichroic mirror 18 and the PBSs 36 and 35.

  The filter 39 has a beam hole 39 (a) through which the data beam passes as shown in FIG. 13 (a). The size of the beam hole 39 (a) is, for example, the same size as the recording area. If the length of the beam shape of the data beam in the moving direction of the hologram medium (the length in the Y1 direction in FIG. 9) is longer than the length of the recording area, the portion of the data beam exceeding the length of the recording area (FIG. 13 ( a) The shaded area) is shielded by the filter 39. As a cause of the beam shape of the data beam exceeding the length of the recording area, for example, an angle error of the incident angle of the data beam with respect to the hologram medium 22, a design error of the installation location of the objective lens 21 and the like can be considered. Further, there may be a case where the data beam is not accurately incident on the recording area because the moving speed of the hologram medium 22 in the moving direction of the hologram medium is faster than the angular speed of the spin mirror 48 described above. Therefore, by providing the filter 39, it is possible to prevent the influence of the angle error or the like on the recording area (for example, the data beam is incident on a plurality of recording areas). As a result, the beam shape of the data beam after passing through the filter 39 has the same length as the recording area in the moving direction of the hologram medium.

  Further, as shown in FIG. 13 (b), the filter 39, when reproducing the hologram, when the length of the beam shape of the reproduction beam is longer than the length of the recording area, the portion of the reproduction beam exceeding the length of the recording area (see FIG. 13 (b) is shaded. More specifically, the beam hole 39 (a) prevents an influence from a hologram adjacent to a hologram to be reproduced in hologram reproduction (so-called reproduction beam crosstalk). For example, when a reference beam is incident to reproduce data from a hologram recorded in the recording area (a) shown in FIG. 13 (b), the reference beam is adjacent to the recording area (a). In some cases. In this case, not only the reproduction beam from the hologram recorded in the recording area (a) but also the reproduction beam from the hologram recorded in the recording area (b) enters the filter 39. When the line image sensor 27 receives the reproduction beam from the hologram recorded in the recording areas (a) and (b), the one-dimensional gray pattern indicated by the hologram recorded in the recording area (a) cannot be accurately reproduced. there is a possibility. Therefore, a beam hole 39 (a) is provided to shield the reproduction beam from the hologram recorded in the recording area (b).

  The scanner lens 20 refracts the reference beam from the collimator lens 45 and makes it incident on the filter 40 so as to irradiate the recording area of the hologram medium 22 with certainty.

  The filter 40 has a beam hole 40 (a) through which the reference beam passes as shown in FIG. 13 (a). The size of the beam hole 40 (a) is, for example, the same size as the recording area. When the length of the beam shape of the reference beam (the length in the Y2 direction in FIG. 10 in FIG. 10) in the moving direction of the hologram medium is longer than the length of the recording area, the portion of the reference beam that exceeds the length of the recording area (see FIG. a) The shaded portion) is shielded from light by the filter 40. The cause of the beam shape of the reference beam exceeding the length of the recording area can be the same as that of the filter 39 described above. As a result, the beam shape of the reference beam after passing through the filter 40 has the same length as the recording area in the moving direction of the hologram medium.

  In the line image sensor 27, the reproduction beam expanded by the objective lens 21 is incident through the dichroic mirror 18 and the PBSs 36 and 35. The line image sensor 27 has a light receiving surface (not shown) corresponding to the beam shape of the reproduction beam. The light receiving surface is composed of, for example, 10 light receiving cells. The line image sensor 27 reproduces a one-dimensional gray pattern based on the received reproduction beam. The line image sensor 27 stores light / dark level information for each light receiving cell in the buffer memory 34 in order to generate an analog electric signal corresponding to the light / dark (light / dark) level for each light receiving cell from the reproduced one-dimensional light / dark pattern. Let The line image sensor 27 sequentially reads light and dark level information for each light receiving cell from the buffer memory 34, generates an analog electric signal, and transmits the analog electric signal to the filter 29. As the line image sensor 27, for example, a CCD (Charge Coupled Devices) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used. In the present embodiment, the LCD 9 and the line image sensor 27 are both provided by the same number of liquid crystal / light receiving cells, but the present invention is not limited to this. For example, the number of light receiving cells of the line image sensor 27 may be larger than the number of liquid crystals of the LCD 9. As a result, the reproduction beam from the objective lens 21 is reliably irradiated to the line image sensor 27, and the one-dimensional gray pattern can be reliably reproduced. In addition, it is possible to reduce the requirement for the process of moving the line image sensor 27 to a predetermined position by the line image sensor control unit 28 with high accuracy.

  The line image sensor control unit 28 performs overall control of the line image sensor 27. Then, the line image sensor control unit 28 moves and rotates the line image sensor 27 so that the one-dimensional gray pattern is accurately reproduced at a predetermined position of the line image sensor 27. For example, a light receiving cell in the one-dimensional gray pattern reproduced by the line image sensor 27 is used as a target mark, and it is determined whether or not the target mark is collated with a predetermined position. When the line image sensor control unit 28 determines that the target mark does not collate with the predetermined position, the line image sensor control unit 28 moves and rotates the line image sensor 27. Alternatively, when the line image sensor control unit 28 determines that the target mark is collated with a predetermined position, the line image sensor 27 causes the line image sensor 27 to generate an analog electric signal having a level corresponding to the brightness of the one-dimensional gray pattern as described above. A signal based on the determination result is transmitted to the CPU 1. Further, the line image sensor control unit 28 determines whether or not the light amount of the reproduction beam of the line image sensor 27 has reached a predetermined light amount for reproducing the one-dimensional gray pattern by the line image sensor 27. When the line image sensor control unit 28 determines that the line image sensor 27 has been irradiated with a reproduction beam having a predetermined light amount or more, the line image sensor control unit 28 sends an instruction signal for closing the first shutter 11 to the first shutter control unit 12. Send.

  The filter 29 filters the analog electrical signal from the line image sensor 27 in order to improve the separation of the binarization process. For example, the one-dimensional gray pattern reproduced by the line image sensor 27 does not reproduce clear light and dark compared to the light and darkness of the one-dimensional gray pattern generated by the LCD 9 due to noise received by the data beam, reproduction beam, and the like. There is a case. For this reason, it is not clear whether the level of the analog electric signal based on the brightness of the one-dimensional gray pattern reproduced by the line image sensor 27 is a level indicating “bright” or a level indicating “dark”. In some cases, the conversion process is not performed properly. Therefore, the level correction of the analog electric signal by the filtering of the filter 29 is performed. Note that a binarization processing unit (not shown) is provided between the filter 29 and the decoder 31, and binarization processing is performed on the analog electric signal from the filter 29. A digital signal obtained as a result of the binarization process is transmitted to the decoder 31.

  The decoder 31 stores the digital signal from the binarization processing unit in the buffer memory 38. Then, the decoder 31 sequentially reads out the digital signals from the buffer memory 38 and performs decoding processing such as demodulation on the modulated digital signals and error correction based on the error correction code, for example. As a result, the hologram reproduction from the hologram recorded in the recording area of the hologram medium 22 is completed.

=== Operation of Hologram Recording Device (Hologram Recording) ===
The operation of the hologram recording apparatus according to the present invention will be described with reference to FIGS. 1 and 9 to 17. FIG. 16 is a flowchart showing an example of the operation of the CPU 1 of the hologram apparatus to which the hologram recording apparatus according to the present invention is applied. FIG. 17 is a schematic diagram showing a hologram recorded in each recording area of the hologram medium 22.

  For example, when a recording instruction signal is stored in the buffer memory 5 from a host device such as a PC via the connection terminal 4 and the interface 3, the recording / reproduction determining unit 6 stores the recording instruction signal in the buffer memory 5. Is determined. Then, the recording / reproduction determining unit 6 transmits an instruction signal to the CPU 1 to start hologram recording by the hologram device. Thereafter, the buffer memory 5 stores data to be subjected to hologram recording. The data stored in the buffer memory 5 is sequentially transmitted to the encoder 7 by the recording / reproduction determining unit 6. Then, the recording / reproducing determination unit 6 transmits information on the amount of data to be recorded on the hologram medium 22 to the CPU 1.

  When the CPU 1 receives the instruction signal from the recording / reproduction determining unit 6 (YES in S101), the CPU 1 reads out address information corresponding to the recording area where the hologram was last recorded in the previous hologram recording from the memory 2 (S102). Then, the CPU 1 calculates a start recording area for starting hologram recording in the hologram recording based on the address information from the memory 2 (S103). Next, the CPU 1 reads out address information corresponding to the calculated start recording area from the memory 2 (S104). Then, the CPU 1 transmits an instruction signal for moving the hologram medium 22 to the disk control unit 24 in order to irradiate the servo laser beam from the servo laser device 19 to the pre-pit indicating the address information from the memory 2 (S105). ). Then, the CPU 1 determines whether or not the address information from the detector 23 is address information corresponding to the start recording area (S106).

  The servo laser device 19 emits a servo laser beam as the hologram device starts to start. The servo laser beam from the servo laser device 19 is reflected by the dichroic mirror 18 and enters the hologram medium 22 perpendicularly via the objective lens 21 and the filter 39.

  Based on the instruction signal from the CPU 1, the disk control unit 24 transmits an instruction signal to the disk drive unit 25 in order to irradiate the servo laser beam to the prepit corresponding to the address information of the start recording area. Then, the disk drive unit 25 moves the hologram medium 22 in the hologram medium moving direction based on the instruction signal from the disk control unit 24.

  The servo laser beam after irradiating the prepit / groove wobble formed on the reflection plate 22 (a) of the hologram medium 22 is incident on the PBS 36 via the objective lens 21 and the dichroic mirror 36. Then, the servo laser beam reflected by the PBS 36 is incident on the detector 23.

  The detector 23 on which the servo laser beam is incident detects address information based on the servo laser beam and transmits it to the CPU 1. Further, the detector 23 generates a wobble signal and transmits it to the PLL circuit 51. Then, the PLL circuit 51 detects the phase difference between the wobble signal from the detector 23 and the clock having a predetermined frequency from the oscillation circuit 52. Then, the reference CLK from the PLL circuit 51 is transmitted to the disk control unit 24 and the spin mirror control unit 46.

  If the CPU 1 determines that the address information from the detector 23 corresponds to the start recording area (YES in S106), the CPU 1 reads the incident angle information from the memory 2 (S107). Then, the CPU 1 calculates the incident angle of the reference beam in the hologram recording based on the incident angle information from the memory 2 (S108). Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 17 so that the reference beam is incident on the hologram medium 22 at the calculated incident angle (S109). The galvo mirror control unit 17 that has received the instruction signal from the CPU 1 controls the deflection angle of the galvo mirror 16 based on the instruction signal. As a result, the reference beam from the PBS 13 is incident on the hologram medium 22 at the incident angle calculated by the CPU 1.

  Data from the buffer memory 5 is stored in the buffer memory 37 via the encoder 7. Then, the encoder 7 sequentially reads data from the buffer memory 37 and performs an encoding process. Then, the encoder output bit data that is the result of the encoding process is transmitted to the mapping processing unit 8. The encoder output bit data is stored in the buffer memory 33 via the mapping processing unit 8. The mapping processing unit 8 reads the encoder output bit data in units of 10-bit data from the buffer memory 33 and transmits it to the LCD 9. When the logical value of the 10-bit encoder output data from the mapping processing unit 8 is “0”, the LCD 9 applies a voltage to each liquid crystal (liquid crystal A to liquid crystal J (FIG. 14)) corresponding to the encoder output data. To do. When the logical value of the encoder output data is “1”, no voltage is applied to each liquid crystal corresponding to the encoder output data.

  The CPU 1 calculates the number of holograms to be recorded on the hologram medium 22 in this hologram recording based on the data amount information from the recording / reproduction determining unit 6 (S110). Then, the CPU 1 calculates a recording area in which the hologram is finally recorded based on the calculated number of holograms (S111). Then, the CPU 1 reads the address information of the recording area where the hologram is finally recorded from the memory 2 (S112). Then, the CPU 1 transmits an instruction signal for opening the first shutter 11 and the second shutter 14 to the first shutter control unit 12 and the second shutter control unit 15 (S113, S114). The first shutter control unit 12 transmits an open state instruction signal to the first shutter 11 based on the instruction signal from the CPU 1 to set the first shutter 11 to the open state. Further, the second shutter control unit 15 transmits an open state instruction signal to the second shutter 14 based on the instruction signal from the CPU 1 to set the second shutter 14 in the open state.

  The laser beam from the laser device 10 is incident on the PBS 13 through the half-wave plate 30 provided with a predetermined inclination. The laser beam is separated into one laser beam and a reference beam by the PBS 13. One laser beam is incident on the laser beam generator 26 via the second shutter 14. The reference beam is incident on the galvo mirror 16.

  One laser beam is expanded by a beam expander 46 constituting the laser beam generator 26 (in the direction of X1Y1 in FIG. 9). The laser beam from the beam expander 46 is deflected into a parallel beam by the collimator lens 47. As a result, the beam shape of the laser beam emitted from the collimator lens 47 becomes the size shown in FIG.

  The reference beam is deflected by the galvo mirror 16 whose deflection angle is controlled by the galvo mirror control unit 17 described above, and is incident on the reference beam generation unit 32. Then, the reference beam is expanded by the beam expander 41 constituting the reference beam generating unit 32 (in the direction of X2Y2 in FIG. 10). The reference beam from the beam expander 41 is deflected into a parallel beam by the collimator lens 42. As a result, the beam shape of the reference beam emitted from the collimator lens 42 has the size shown in FIG.

  Based on the reference CLK from the PLL circuit 51, the spin mirror control unit 46 transmits an instruction signal to the spin mirror drive units 49 and 44 in order to rotate the spin mirrors 48 and 43 at a predetermined angular velocity. The spin mirror drive unit 49 rotates the spin mirror 48 in the spin mirror rotation direction based on the instruction signal from the spin mirror control unit 46. As a result, the laser beam from the collimator lens 47 is deflected by the spin mirror 48 that rotates at a predetermined angular velocity. The laser beam from the spin mirror 48 is deflected to a parallel beam by the collimator lens 50. As a result, the laser beam from the collimator lens 50 scans the LCD 9 in the direction of FIG. 9 + Y3 (refer to FIG. 9 (c), start to end), and a data beam reflecting a one-dimensional gray pattern is generated. . Further, by scanning the LCD 9 in the direction of FIG. 9 + Y3, the recording area is scanned in the direction of FIG. 9 (c) + Z. Further, the spin mirror driving unit 44 rotates the spin mirror 43 in the spin mirror rotation direction based on the instruction signal from the spin mirror control unit 46. As a result, the reference beam from the collimator lens 42 is deflected by the spin mirror 43 that rotates at a predetermined angular velocity. The reference beam from the spin mirror 43 is deflected to a parallel beam by the collimator lens 45. As a result, the reference beam from the collimator lens 45 scans the recording area in the + Z direction of FIG.

  The data beam from the LCD 9 is reflected by the PBS 35 and enters the objective lens 21 through the PBS 36 and the dichroic mirror 18. The data beam is collected by the objective lens 21 and enters the filter 39. When the length of the beam shape of the data beam is longer than the length of the recording area in the moving direction of the hologram medium, the data beam portion exceeding the recording area is shielded by the filter 39. As a result, a data beam having the same length as the recording area is incident on the recording area in the moving direction of the hologram medium. Further, as described above, when the spin mirror 48 is rotated, all data beams reflecting the one-dimensional gray pattern are incident on the recording area.

  The reference beam from the collimator lens 45 is refracted by the scanner lens 20 and enters the filter 40. If the length of the beam shape of the reference beam is longer than the length of the recording area in the moving direction of the hologram medium, the portion of the reference beam that exceeds the recording area is shielded by the filter 40. As a result, a reference beam having the same length as the recording area is incident on the recording area in the moving direction of the hologram medium. Further, as described above, when the spin mirror 43 is rotated, the reference beam is incident on the recording area together with the data beam.

  As a result, the data beam and the reference beam reflecting the one-dimensional gray pattern are incident on the recording area. Then, by irradiating the recording area with the data beam and the reference beam for a predetermined period, a hologram is recorded in the recording area of the hologram medium 22 as shown in FIG. That is, a hologram showing a one-dimensional gray pattern is recorded in the recording area. In this way, the bits for forming the one-dimensional gray pattern without storing the encoder output bit data in the buffer memory 33 until the encoder output bit data reaches the number of bits for forming the two-dimensional gray image pattern. Hologram recording can be performed sequentially when the number (10 bits in the present embodiment) is stored in the buffer memory 33.

  Then, when the hologram apparatus repeats the above-described hologram recording, a hologram is recorded in each recording area as shown in FIG. Note that the holograms (a) -1, (a) -2,..., (B) -1,..., (C) -1 shown in FIG. This shows a state in which hologram recording is performed from the area to the recording area on the outer peripheral side. Hereinafter, a case where a hologram is recorded in the final recording area of the hologram medium 22 in the hologram recording will be described.

  If the CPU 1 determines that the address information from the detector 23 corresponds to the final recording area (YES in S116), the CPU 1 transmits an instruction signal for closing the first shutter 11 to the first shutter control unit 12. (S117). Based on the instruction signal from the CPU 1, the first shutter control unit 12 transmits a closed state instruction signal to the first shutter 11 to place the first shutter 11 in the closed state. As a result, the laser beam from the laser device 10 is shielded by the first shutter 11 and the hologram recording is interrupted.

  Next, the CPU 1 reads out address information corresponding to the first recording area from the memory 2 (S118). Then, the CPU 1 transmits an instruction signal for moving the hologram medium 22 to the disk control unit 24 so as to irradiate the servo laser beam to the pre-pit indicating the first recording area (S119).

  Based on the instruction signal from the CPU 1, the disk control unit 24 transmits an instruction signal to the disk drive unit 25 in order to irradiate the servo laser beam to the prepit corresponding to the address information of the first recording area. Then, the disk drive unit 25 moves the hologram medium 22 in the hologram medium moving direction based on the instruction signal from the disk control unit 24. As a result, the servo laser beam is applied to the prepit corresponding to the first recording area and is incident on the detector 23.

  If the CPU 1 determines that the address information from the detector 23 corresponds to the first recording area (YES at S120), the CPU 1 reads the incident angle information from the memory 2 and calculates the incident angle of the reference beam (S121). . Note that the incident angle of the reference beam calculated by the CPU 1 at this time is different from the incident angle of the reference beam used in the previous hologram recording as described above. As a result, a large amount of holograms by angle multiplex recording is recorded in each recording area of the hologram medium 22. Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 17 so that the reference beam is incident on the hologram medium 22 at the calculated incident angle (S122). The galvo mirror control unit 17 that has received the instruction signal from the CPU 1 controls the deflection angle of the galvo mirror 16 based on the instruction signal. Therefore, the reference beam from the PBS 13 is incident on the hologram medium 22 at the incident angle calculated by the CPU 1. Further, the CPU 1 transmits an instruction signal for opening the first shutter 11 to the first shutter control unit 12 (S123). The first shutter control unit 12 transmits an open state instruction signal to the first shutter 11 based on the instruction signal from the CPU 1 to set the first shutter 11 to the open state. As a result, hologram recording is performed again in the hologram apparatus. Further, the CPU 1 stores the calculated incident angle in the memory 2 as incident angle information (S124).

  As a result, the hologram of the data beam and the reference beam reflecting the one-dimensional gray pattern is recorded in each recording area by angle multiplex recording. FIGS. 17B, 17C, and 17D are views showing the state of a hologram recorded by angle multiplex recording in each recording area of the hologram medium 22. FIG. In the present embodiment, hologram recording is performed from the first recording area to the final recording area, and then the incident angle of the reference beam is changed and hologram recording is performed again from the first recording area to the final recording area. It is not limited to. For example, after performing angle multiplex recording on a certain recording area, the hologram medium 22 may be moved to perform angle multiplex recording again on another recording area.

  When the CPU 1 determines that the address information from the detector 23 corresponds to the recording area in which the hologram is recorded last in the hologram recording (S115 YES), the first shutter control unit 12 and the second shutter control unit 12 Instruction signals for closing the first shutter 11 and the second shutter 14 are transmitted to the shutter control unit 15 (S125, S126). The first shutter control unit 12 transmits a closed state instruction signal to the first shutter 11 based on an instruction signal from the CPU 1 to set the first shutter 11 in the closed state. Further, the second shutter control unit 15 transmits a closed state instruction signal to the second shutter 14 based on the instruction signal from the CPU 1, and sets the second shutter 14 in the closed state. Further, the CPU 1 rewrites the address information recorded last in the hologram recording stored in the memory 2 to the address information of the recording area in which the hologram was last recorded in the hologram recording (S127). As a result, hologram recording by the hologram device is completed.

=== Operation of hologram recording device (hologram reproduction) ===
Hereinafter, the hologram reproduction from the hologram medium 22 in which the hologram is recorded in each recording area as described above will be described. Note that a description of the same parts as those described above will be omitted.

  For example, when a reproduction instruction signal is stored in the buffer memory 5 from a host device such as a PC via the connection terminal 4 and the interface 3, the recording / reproduction determination unit 6 stores the reproduction instruction signal in the buffer memory 5. Is determined. Then, the recording / reproduction determining unit 6 transmits an instruction signal to the CPU 1 in order to start hologram reproduction by the hologram apparatus.

  When the CPU 1 receives the instruction signal from the recording / reproduction discriminating unit 6, the CPU 1 reads out address information corresponding to a recording area (hereinafter referred to as a reproduction recording area) where a hologram to be reproduced in this hologram reproduction is recorded from the memory 2. Then, the CPU 1 transmits an instruction signal for moving the hologram medium 22 to the disk control unit 24 so that the pre-pits indicating the address information from the memory 2 are irradiated with the servo laser beam from the servo laser device 19. Then, the CPU 1 determines whether or not the address information from the detector 23 is address information corresponding to the reproduction / recording area.

  When the CPU 1 determines that the address information from the detector 23 corresponds to the reproduction / recording area, the CPU 1 reads the incident angle information from the memory 2. The incident angle information read from the memory 2 by the CPU 1 at this time indicates the incident angle of the reference beam when the hologram is recorded in the reproduction recording area. Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 17 so that the reference beam is incident on the hologram medium 22 at the aforementioned incident angle. The galvo mirror control unit 17 that has received the instruction signal from the CPU 1 controls the deflection angle of the galvo mirror 16 based on the instruction signal. As a result, the reference beam from the PBS 13 is incident on the hologram medium 22 at the incident angle calculated by the CPU 1. At this time, the reference beam generator 32 rotates the spin mirror 43 as described above to deflect the reference beam so that the reference beam scans the reproduction recording area.

As a result, the reference beam is incident on the hologram recorded in the reproduction recording area. Then, the reference beam incident on the hologram recorded in the reproduction recording area is diffracted by the hologram to become a reproduction beam reflecting the information of the one-dimensional gray pattern (see FIG. 13B). Then, this reproduction beam is incident on the filter 39. Of the reproduction beam incident on the filter 39, the reproduction beam from the recording area adjacent to the reproduction recording area is shielded by the filter 39. As a result, the reproduction beam diffracted only by the hologram recorded in the reproduction recording area is transmitted through the beam hole 39 (a).
The reproduction beam from the filter 39 is expanded by the objective lens 21 and received by the line image sensor 27 via the dichroic mirror 18 and the PBSs 36 and 35.

  The line image sensor control unit 28 moves and rotates the line image sensor 27 in order to accurately reproduce the one-dimensional gray pattern at a predetermined position of the line image sensor 27. The line image sensor 27 on which the reproduction beam is incident reproduces a one-dimensional gray pattern based on the reproduction beam. Then, the line image sensor 27 stores light / dark level information for each light receiving cell in the buffer memory 34 in order to generate an analog electric signal corresponding to the light / dark (light / dark) level for each light receiving cell from the reproduced one-dimensional light / dark pattern. Remember. The line image sensor 27 sequentially reads the light / dark level information for each light receiving cell from the buffer memory 34, generates an analog electrical signal, and transmits it to the filter 29.

  The analog electrical signal transmitted to the filter 29 is filtered by the filter 29 in order to improve the separability of the binarization process. The analog electrical signal is binarized by a binarization processing unit (not shown) to become a digital signal. The digital signal is stored in the buffer memory 38 via the decoder 31. The decoder 31 sequentially reads out the digital signal from the buffer memory 38 and performs decoding processing such as demodulation on the modulated digital signal and error correction based on the error correction code.

  As a result, it is possible to perform hologram reproduction from a hologram showing a one-dimensional gray pattern. In the generation of the analog electric signal by the line image sensor 27, the amount of data stored in the buffer memory 34 can be reduced as compared with the hologram reproduction from the two-dimensional gray image pattern. Further, since the amount of data for generating the analog electric signal is reduced, the hologram can be reproduced quickly.

  According to the above-described embodiment, the data beam and the reference beam reflecting the one-dimensional shading pattern are incident on the recording area for recording the hologram showing the one-dimensional shading pattern, and the hologram is placed in each recording area of the hologram medium 22. It becomes possible to record. As a result, it is possible to reduce the burden on the buffer memory 33 as compared with the case where a two-dimensional gray image pattern is recorded on the hologram medium 22. In addition, hologram recording can be performed sequentially without requiring time for hologram recording.

  Further, the laser beam from the second shutter 14 is made substantially the same length as the recording area in the hologram medium moving direction by the beam expander 46 and the collimator lens 47 and shorter than the recording area in the direction crossing the hologram medium moving direction. It becomes possible to make it a long beam shape. As a result, it is possible to generate a data beam having a higher light intensity than the data beam when recording a two-dimensional gray image pattern, and to reliably record a hologram in the recording area. Become.

  Further, the laser beam from the collimator lens 47 can be reliably incident on the recording area by the spin mirror 48 and the collimator lens 50.

  In addition, by providing the LCD 9 in substantially the same shape as the recording area, it is possible to reduce the size of the hologram device. In addition, a one-dimensional gray pattern can be formed on the LCD 9, and the burden on the buffer memory 33 can be reliably reduced.

  In addition, the reference beam from the galvo mirror 16 is set to be approximately the same length as the recording area in the hologram medium moving direction by the beam expander 41 and the collimator lens 42 and shorter than the recording area in the direction intersecting the hologram medium moving direction. It becomes possible to have a beam shape. As a result, it is possible to generate a reference beam having a higher light intensity than the light intensity of the reference beam when recording a two-dimensional grayscale image pattern, and reliably record a hologram in the recording area. Is possible.

  Further, the reference beam from the collimator lens 42 can be reliably incident on the recording area by the spin mirror 43 and the collimator lens 45.

  Further, the filter 39 makes it possible to reliably make the data beam having the same shape as the recording area enter the recording area. Further, the filter 39 can reliably prevent the influence of the reproduction beam from the recording area adjacent to the reproduction recording area.

  Further, the filter 40 can surely make the reference beam having the same shape as the recording area enter the recording area.

  In addition, a large number of holograms can be recorded on the hologram medium 22 by sequentially inputting the data beam and the reference beam to each recording area. In addition, the time for hologram recording can be shortened. Further, with this hologram recording, it is possible to shorten the time for hologram reproduction.

  In hologram recording, angle multiplex recording can be performed by changing the incident angle of the reference beam to the hologram medium 22. In addition, since hologram recording is performed on all the recording areas of the hologram medium 22 at a certain incident angle, and then the incident angle of the reference beam is changed, it is possible to continuously move the hologram medium 22 and perform hologram recording. Become. As a result, hologram recording can be performed in a shorter time.

=== Other Embodiments ===
The hologram recording / reproduction in the hologram recording apparatus according to the present invention has been described above. However, the above description is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof.

<Shape of data beam and reference beam>
According to the embodiment described above, the laser beam from the second shutter 14 has the beam shape shown in FIG. 11 by the laser beam generator 26, but is not limited thereto. For example, a beam shape having the same shape as each recording area may be used. In this case, for example, the beam shape of the laser beam from the second shutter 14 is expanded by the beam expander (beam generator) 46 so as to have the same shape as each recording area. The collimator lens 47 converts the laser beam from the beam expander 46 into a parallel beam. And you may provide so that the laser beam from the collimator lens 47 may be irradiated to LCD9. As a result, it is possible to record a one-dimensional gray pattern with a data beam having a higher light intensity compared to the light intensity of the data beam when recording a hologram showing a two-dimensional gray image pattern.

  Similarly, according to the above-described embodiment, the reference beam from the galvo mirror 16 has the beam shape shown in FIG. 12 at the reference beam generator 32, but the present invention is not limited to this. For example, a beam shape having the same shape as each recording area may be used. In this case, for example, the beam shape of the reference beam from the galvo mirror 16 is expanded by the beam expander (beam generator) 41 so as to have the same shape as each recording area. Then, the collimator lens 42 converts the reference beam from the beam expander 41 into a parallel beam. Then, a reference beam from the collimator lens 42 may be provided to irradiate each recording area. As a result, it is possible to record a one-dimensional gray pattern with a reference beam having a higher light intensity than the light intensity of the reference beam when recording a hologram showing a two-dimensional gray image pattern.

It is a figure which shows an example of the whole structure of the hologram recording apparatus which concerns on this invention. It is the figure which modeled a mode when a monomer changes to a polymer according to the energy of a laser beam. It is the figure which showed typically the book and page in angle multiplexing recording. It is a figure showing the operation in hologram recording / reproduction. It is the figure which showed formation of the two-dimensional grayscale image pattern in hologram recording. It is the figure which showed the spatial light modulation element of SLM. It is the figure which showed the hologram reproduction | regeneration of a two-dimensional gray image pattern. It is the figure which showed the light reception cell of the image sensor. It is the figure which showed the laser beam generation part 26 shown in FIG. It is the figure which showed the reference beam generation part 32 shown in FIG. It is the figure which showed the beam shape of the laser beam formed in the laser beam generation part 26 shown in FIG. It is the figure which showed the beam shape of the reference beam formed in the reference beam generating part 32 shown in FIG. It is the figure which showed the filters 39 and 40 shown in FIG. It is the figure which showed the liquid crystal of LCD9 shown in FIG. FIG. 3 is a diagram showing each recording area of the hologram medium 22. It is a timing chart which shows an example of operation | movement of the hologram recording apparatus which concerns on this invention. It is the figure which showed the hologram recording by the hologram recording apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CPU 2 Memory 3 Interface 4 Connection terminal 5 Buffer memory 6 Recording / playback discrimination | determination part 7 Encoder 8 Mapping process part 9 LCD 10 Laser apparatus 11 1st shutter 12 1st shutter control part 13 PBS
14 Second shutter 15 Second shutter control unit 16 Galvo mirror 17 Galvo mirror control unit 18 Dichroic mirror 19 Servo laser device 20 Scanner lens 21 Objective lens 22 Hologram medium 23 Detector 24 Disc control unit 25 Disc drive unit 26 Laser beam generation unit 27 Line Image Sensor 28 Line Image Sensor Control Unit 29 Filter 30 Half Wave Plate 31 Decoder 32 Reference Beam Generation Units 33 and 34 Buffer Memory 35 and 36 PBS
37, 38 Buffer memory 39, 40 Filter 41, 46 Beam expander 42, 45 Collimator lens 43, 48 Spin mirror 44, 49 Spin mirror driver 47, 50 Collimator lens 51 PLL circuit 52 Oscillator circuit 107 Encoder 108 Mapping processor 109 SLM 110, 111 Buffer memory 127 Image sensor 129 Filter 130 Decoder 131, 132 Buffer memory

Claims (15)

A hologram in which a coherent data beam corresponding to data to be recorded and a coherent reference beam are incident on a recording area of the hologram medium, and the data is recorded as a hologram in the recording area of the hologram medium A recording device,
When recording the data, a data beam generating unit that generates a data beam incident on each recording area smaller than the recording area, divided for each predetermined width adjacent in the relative movement direction of the hologram medium; ,
A data beam incident unit that makes the data beam generated by the data beam generation unit incident on each recording area of the hologram medium;
A reference beam incident part that makes a reference beam incident on each recording area of the hologram medium together with the data beam from the data beam incident part,
A holographic recording apparatus comprising: The data beam generator is
A laser beam generator configured so that the shape of the laser beam when irradiated to each recording area is substantially the same shape as each recording area;
A dot pattern generator for generating a light and dark dot pattern corresponding to the logical value of the data,
A laser beam from the laser beam generator generates a data beam incident on each recording area by irradiating the dot pattern generated on the dot pattern generator.
The hologram recording apparatus according to claim 1. The laser beam generator is
A beam generator that makes the shape of the laser beam when irradiated to each recording area substantially the same shape as each recording area;
A collimator lens that collimates the laser beam from the beam generator,
The hologram recording apparatus according to claim 2, wherein: The data beam generator is
The shape of the laser beam when irradiated to each recording area is substantially the same as the predetermined width in the moving direction, and is shorter than the length of each recording area in the direction intersecting the moving direction. A laser beam generator,
A dot pattern generator for generating a light and dark dot pattern corresponding to the logical value of the data,
A laser beam from the laser beam generator generates a data beam incident on each recording region by sequentially irradiating the dot pattern generated on the dot pattern generator.
The hologram recording apparatus according to claim 1. The laser beam generator is
The shape of the laser beam when irradiated to each recording area is substantially the same as the predetermined width in the moving direction, and is shorter than the length of each recording area in the direction intersecting the moving direction. A beam generator,
A first collimator lens that makes the laser beam from the beam generator a parallel beam,
The data beam generator is
Rotating mirror type optical deflection that rotates to deflect the laser beam so that the laser beam after being collimated by the first collimator lens is sequentially incident on the dot pattern generated by the dot pattern generator And
A second collimator lens that makes the laser beam deflected by the rotating mirror type optical deflector a parallel beam,
The laser beam from the second collimator lens sequentially irradiates the dot pattern generated on the dot pattern generator, thereby generating a data beam incident on each recording area.
The hologram recording apparatus according to claim 4. The dot pattern generator is
Substantially the same shape as each recording area of the hologram medium,
A dot pattern that is one dot in the movement direction and a plurality of dots in a direction intersecting the movement direction is generated.
6. The hologram recording apparatus according to claim 2, wherein the hologram recording apparatus is characterized in that: The reference beam incident part is
A reference beam generator that makes the shape of the reference beam irradiated to each recording area substantially the same shape as each recording area;
7. The hologram recording apparatus according to claim 1, wherein The reference beam generator is
A beam generator having a shape of the reference beam substantially the same as each recording area;
A collimator lens that collimates the reference beam from the beam generator,
The hologram recording apparatus according to claim 7. The reference beam incident part is
The length of the reference beam in the moving direction is substantially the same as the predetermined width, and the length of the reference beam in the direction intersecting the moving direction is the recording area in the direction intersecting the moving direction. A reference beam generator having a length shorter than
The reference beam from the reference beam generator is sequentially incident in a direction intersecting the moving direction for each recording area.
7. The hologram recording apparatus according to claim 1, wherein The reference beam generator is
The length of the reference beam in the moving direction is substantially the same as the predetermined width, and the length of the reference beam in the direction intersecting the moving direction is the recording area in the direction intersecting the moving direction. A beam generator with a length shorter than the length of
A first collimator lens that makes the reference beam from the beam generator a parallel beam,
The reference beam incident part is
Rotating mirror-type light that rotates to deflect the reference beam so that the reference beam, which has been converted into a parallel beam by the first collimator lens, sequentially enters each recording area in a direction that intersects the moving direction. A deflector;
A second collimator lens that makes the reference beam deflected by the rotating mirror type optical deflector a parallel beam;
The hologram recording apparatus according to claim 9. A data beam restricting section for restricting transmission of the data beam from the data beam incident section so that the shape of the data beam when irradiated to each recording area is the same as that of each recording area. Provided between the portion and the hologram medium,
11. The hologram recording apparatus according to claim 1, wherein the hologram recording apparatus is characterized in that: A reference beam limiting unit that limits transmission of the reference beam from the reference beam incident unit so that the shape of the reference beam when irradiated to each recording region is the same as that of each recording region. Provided between the portion and the hologram medium,
12. The hologram recording apparatus according to claim 1, wherein the hologram recording apparatus is characterized in that: The data beam incident section sequentially enters the data beam to each recording area of the hologram medium,
The reference beam incident section sequentially enters the reference beam to each recording area of the hologram medium together with the data beam from the data beam incident section.
The hologram recording apparatus according to claim 1, wherein the hologram recording apparatus is a hologram recording apparatus. A reference beam changing unit that changes an incident angle of the reference beam from the reference beam incident unit with respect to the hologram medium;
The reference beam changing unit changes the incident angle of the reference beam with respect to the hologram medium when the movement of the hologram medium in the movement direction is completed again after all movement of the hologram medium in the movement direction is completed. To
14. The hologram recording apparatus according to claim 1, wherein the hologram recording apparatus is characterized in that: A hologram in which a coherent data beam corresponding to data to be recorded and a coherent reference beam are incident on a recording area of the hologram medium, and the data is recorded as a hologram in the recording area of the hologram medium A hologram recording method for a recording apparatus,
When recording the data, generate a data beam incident on each recording area smaller than the recording area, divided for each predetermined width adjacent in the relative movement direction of the hologram medium,
The generated data beam is incident on each recording area of the hologram medium,
A reference beam is incident on each recording area of the hologram medium together with the data beam.
A hologram recording method for a hologram recording apparatus.

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