JP2006317781A - Hologram reproducing apparatus and method for reproducing hologram - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram reproducing apparatus and a method for reproducing in a hologram reproducing apparatus which can fast reproduce digital data from a hologram. <P>SOLUTION: The reproducing apparatus is equipped with: a reference beam incident part to enter a coherent reference beam onto a hologram medium in which first data to be reproduced and second data for position adjustment are recorded as a hologram; a first light receiving part to receive a first beam diffracted by the hologram representing the first data; a second light receiving part to receive a second beam diffracted by the hologram representing the second data; a calculating part to calculate a positional error between the received second beam and a second beam to be received if the first light receiving part is at a reference position matching the first beam; a correction driving part to correct the first light receiving part to the reference position based on the calculated positional error; and a reproducing unit to reproduce the first data based on the first beam when no positional error is calculated or on the first beam after correction driving. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hologram reproducing apparatus and a reproducing method for a hologram reproducing 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 recording digital data on this hologram medium as a hologram, first, the laser beam from the laser device is separated 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 Digital data is recorded on the hologram medium by irradiating the hologram medium with a laser beam reflecting the information of the two-dimensional grayscale image pattern (hereinafter referred to as a data beam) at a predetermined angle.

  More specifically, the photosensitive resin constituting the hologram medium has a finite number of monomers and is irradiated with a laser beam composed of a reference beam and a data beam (hereinafter referred to as a laser beam). Depending on the amount of light and energy depending on the irradiation time, the monomer changes into a polymer. Then, when this monomer is changed to a polymer, interference fringes made of a polymer corresponding to the energy of the laser beam are formed. The interference fringes are formed in the hologram medium, so that digital data is recorded as a hologram. Thereafter, the remaining monomer moves (diffuses) to the place where the monomer is consumed. Then, by irradiating the laser beam again, the change of the monomer to the polymer is repeated. FIG. 2 schematically shows a state where the monomer changes into a polymer in the hologram medium in accordance with the energy of the laser beam.

  For example, 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 recorded by changing the incident angle of the reference beam to the hologram medium. For example, one hologram recorded on the hologram medium is referred to as a page, and a multiple hologram composed of 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, 10 pages of holograms can be recorded on one book by changing the incident angle of the reference beam. That is, a large amount of digital data can be recorded on the hologram medium by angle multiplexing recording. Note that angle multiplex recording can be performed by changing the incident angle of the data beam to the hologram medium, and can also be performed by changing the incident angles of both the data beam and the reference beam to the hologram medium.

  Further, when digital data is reproduced from a hologram medium, a reference beam is irradiated onto the hologram indicating the digital data to be reproduced at the same incident angle as the angle at which the hologram was recorded. 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 grayscale image pattern with a decoder or the like.

In order to accurately reproduce the two-dimensional gray image pattern from the reproduction beam, the light amount of the reproduction beam must be a certain level or higher 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 (ratio of the light amount of the reproduction beam to the light amount of the irradiated reference beam) equal to or higher than a predetermined value that makes the light amount of the reproduction beam equal to or higher than a certain level.
JP2002-216359

  Thus, when reproducing digital data from a hologram medium, it is necessary to accurately receive the reproduction beam with an image sensor or the like. However, there is a problem that the reproduction beam cannot be received accurately due to a mechanical error of the system for reproducing digital data, inclination of the system or the hologram medium, and shrinkage of the hologram medium due to hologram recording. As a result, there is a possibility that digital data cannot be accurately reproduced. Or there was a possibility that digital data could not be reproduced.

  Therefore, conventionally, a method called pixel matching has been used to accurately receive the reproduction beam with an image sensor or the like. Hereinafter, pixel matching will be described in detail with reference to FIGS. 4 and 5. FIG. 4A shows a two-dimensional gray image pattern (15 dots × 15 dots) indicated by the reproduction beam. FIG. 4B is a diagram showing a light receiving surface (15 pixels × 15 pixels) of the image sensor that receives the reproduction beam. FIG. 5 is a diagram showing irradiation of the reproduction beam and reception of the reproduction beam by the image sensor.

  In pixel matching, first, for example, A1, A15, O1, and O15 (FIG. 4A) in the two-dimensional gray image pattern indicated by the reproduction beam are determined as target marks. Further, the pixels (FIG. 4 (b) a1, a15, o1, o15) in the light receiving surface with which the target mark matches when the reproduction beam is accurately received by the image sensor are determined as target pixels.

  First, the reproduction beam is irradiated on the light-receiving surface of the image sensor, so that the reproduction beam reaches a light amount of a certain level or more (t1). Then, for example, an image sensor control unit that controls the image sensor determines whether or not the target mark matches the target pixel. When the target mark and the target pixel do not match, that is, when a position error occurs between the target mark and the target pixel, the image sensor control unit corrects the image sensor or the light receiving surface based on the position error ( Send an instruction signal to move. As a result, the image sensor or the light receiving surface is corrected (moved) to a position where the target mark and the target pixel match (between t3 and t4). Then, the reproduction beam is irradiated again on the light receiving surface of the image sensor, and digital data is reproduced based on the reproduction beam (between t5 and t6).

  However, in the pixel matching described above, it is necessary to temporarily receive the reproduction beam on the light receiving surface of the image sensor and determine whether or not the target mark matches the target pixel by the image sensor control unit. When there is a position error between the target mark and the target pixel, it is necessary to correct (move) the image sensor or the light receiving surface based on the position error. Therefore, the processing time for determining whether or not the target mark and the target pixel are matched, the processing time for correcting (moving) the image sensor or the light receiving surface, and the time until the reproduction beam reaches a light level above a certain level. There is a problem that it takes time to reproduce the digital data from the hologram.

  Therefore, an object of the present invention is to provide a hologram reproducing apparatus and a reproducing method for the hologram reproducing apparatus that can perform digital data reproduction processing from a hologram at high speed.

  The invention for solving the above-described problems is directed to a reference beam in which a coherent reference beam is incident on a hologram medium in which second data for adjusting a light receiving position is recorded as a hologram together with first data to be reproduced. An incident part, a first light receiving part for receiving the first reference beam after the reference beam from the reference beam incident part is diffracted by the hologram indicating the first data, and the reference from the reference beam incident part A second light receiving unit for receiving a second reference beam after the beam is diffracted by the hologram indicating the second data, the second reference beam received by the second light receiving unit, and the first light receiving unit. A calculation unit that calculates a position error of the second reference beam to be received by the second light receiving unit when the second reference light beam is at a reference position that matches the first reference beam; Based on the position error when the position error is calculated, a correction drive unit for correcting and driving the first light receiving unit to the reference position, and the first when the position error is not calculated by the calculation unit Based on the first reference beam received by the light receiving unit or the first reference beam received by the first light receiving unit after the correction driving unit corrects and drives the first light receiving unit to the reference position. And a reproducing unit for reproducing the first data.

  Further, a reference beam incident section for injecting a coherent reference beam to a hologram medium in which second data for adjusting a light receiving position is recorded as a hologram together with first data to be reproduced, and the reference beam incident And a light receiving unit that receives the first reference beam after being diffracted by the hologram indicating the first data, the reproduction method of the hologram reproducing apparatus comprising: The second reference beam after the reference beam is diffracted by the hologram indicating the second data is received, and the received second reference beam and the light receiving unit are in a reference position that matches the first reference beam. A position error with respect to the second reference beam to be received is calculated, and the reception error is calculated based on the position error when the position error is calculated. The first reference beam received by the light receiving unit when the position error is not calculated, or the light receiving unit after the light receiving unit is corrected and driven to the reference position. The first data is reproduced based on the received first reference beam.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the hologram reproducing apparatus and the reproducing method of a hologram reproducing apparatus which can perform the reproduction process of digital data from a hologram at high speed.

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

=== Overall Configuration of Hologram Reproducing Device ===
A hologram reproducing apparatus according to the present invention will be described with reference to FIGS. 1 and 7 to 10. Further, the hologram medium 24 to be reproduced by the hologram reproducing apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a functional block diagram showing an example of the entire configuration of a hologram reproducing apparatus according to the present invention. FIG. 6 is a diagram showing unit page arrangement data indicated by the hologram recorded on the hologram medium 24 and a two-dimensional gray image pattern. FIG. 7 is a front view of the image sensor 14 shown in FIG. FIG. 8 is a cross-sectional view of the image sensor 14. FIG. 9 is a diagram showing four regions A to D of the four-divided sensors 26 (A) to (D). FIG. 10 is a diagram showing the light intensity of the reproduction beam.

  The hologram reproducing apparatus includes a CPU (Central Processing Unit) 1, a memory 2, a timer 25, an interface 3, a connection terminal 4, a laser device 5 (reference beam incident unit), a shutter 6, a shutter control unit 7, and a galvo mirror 8 (reference beam). Incident unit), galvo mirror control unit 9, servo laser device 10, dichroic mirror 11, scanner lens 12 (reference beam incident unit), Fourier transform lens 13, detector 21, disk control unit 22, disk drive unit 23, image sensor 14 (reproduction unit), image sensor control unit 15, operational amplifier 16, calculation unit 17 (calculation unit), image sensor drive unit 18 (correction drive unit), filter 19 (reproduction unit), and decoder 20 (reproduction unit). .

  The interface 3 is interposed between the host device (not shown) such as a PC (Personal Computer) connected via the connection terminal 4 and the hologram reproducing apparatus for data transmission / reception. A reproduction instruction signal for the hologram reproduction apparatus to perform reproduction processing from the hologram medium 24 is transmitted from the host device to the interface 3.

  The laser device 5 emits a laser beam (hereinafter referred to as a reference beam) excellent in temporal and spatial coherence to the shutter 6. The reference beam emitted from the laser device 5 is, for example, a helium neon laser, an argon neon laser, a helium cadmium laser, a semiconductor laser, a dye, in order to reproduce digital data (first data) from the hologram recorded on the hologram medium 24. A laser, a ruby laser, or the like is used.

  The servo laser device 10 emits a laser beam (hereinafter referred to as a servo laser beam) to the dichroic mirror 11 so as to irradiate a pre-pit described later provided on the hologram medium 24. The servo laser beam emitted from the servo laser device 10 is a beam having a predetermined wavelength that does not affect the hologram recorded on the hologram medium 24. Therefore, in this embodiment, for example, a blue laser beam is used as a reference beam emitted from the laser device 5, and a red laser beam having a longer wavelength than the blue laser beam is used as a servo laser beam. The servo laser beam is emitted from the servo laser device 10 when, for example, the hologram reproducing device starts to be activated and starts emitting, and the servo laser beam is continuously emitted during the period when the hologram reproducing device is activated. .

  The CPU 1 performs overall control of the hologram reproducing device. When the CPU 1 receives the reproduction instruction signal from the host device, the CPU 1 reads the address information of the hologram to be reproduced from the memory 2. Then, the CPU 1 transmits an instruction signal to the disk control unit 22 so as to irradiate the servo laser beam to the prepit indicating the address information read from the memory 2. The CPU 1 determines whether the address information from the detector 21 matches the address information read from the memory 2. Further, the CPU 1 reads out information on the incident angle of the reference beam from the memory 2 when the hologram to be reproduced is recorded. Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 9 so that the reference beam is incident on the hologram medium 24 at the incident angle read from the memory 2.

  When the CPU 1 determines that the address information from the detector 21 matches the address information read from the memory 2, the CPU 1 transmits an instruction signal for opening the shutter 6 to the shutter control unit 7. Then, the CPU 1 starts the timer 25 and determines whether or not the timer 25 has measured a predetermined time. As a result, the reproduction process from the hologram recorded on the hologram medium 24 is started. Note that the predetermined time means that in the reproduction process from the hologram, the image sensor 14 can generate an analog signal to be described later based on a reference beam diffracted by the hologram (hereinafter referred to as a reproduction beam). It shows the time which becomes. When the CPU 1 determines that the timer 25 has counted a predetermined time, the CPU 1 transmits an instruction signal for closing the shutter 6 to the shutter control unit 7. As a result, the reproduction process from the hologram medium 24 is completed. Note that the CPU 1 may end the reproduction process by an instruction signal based on the determination result from the image sensor control unit 15.

  In the memory 2, program data for the CPU 1 to perform the above-described processing is stored in advance. The memory 2 stores in advance address information corresponding to prepits provided in the hologram medium 24. The memory 2 stores address information corresponding to the hologram recorded on the hologram medium 24. The memory 2 stores information on the incident angle of the reference beam when the hologram is recorded on the hologram medium 24. 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 shutter control unit 7 performs control for opening or closing the shutter 6 based on an instruction signal from the CPU 1. Further, the shutter control unit 7 performs control for closing the shutter 6 based on the instruction signal from the image sensor control unit 15. When the shutter controller 7 opens the shutter 6, the shutter controller 7 transmits an open state instruction signal to the shutter 6. Further, when the shutter controller 7 closes the shutter 6, the shutter controller 7 transmits a closed state instruction signal to the shutter 6. The shutter 6 enters an open state based on an open state instruction signal from the shutter control unit 7. Alternatively, the shutter 6 enters the closed state based on the closed state instruction signal from the shutter 7. When the shutter 6 is opened, the reference beam emitted from the laser device 5 is incident on the galvo mirror 8.

  The galvo mirror control unit 9 controls the deflection angle of the galvo mirror 8 so as to determine the incident angle of the reference beam deflected by the galvo mirror 8 with respect to the hologram medium 24 based on the instruction signal from the CPU 1. The galvo mirror 8 deflects the reference beam from the laser device 5 and makes it incident on the dichroic mirror 11.

  The dichroic mirror 11 transmits the reference beam from the galvo mirror 8 and causes the reference beam to enter the scanner lens 12. The dichroic mirror 11 reflects the servo laser beam emitted from the servo laser device 10 and causes the servo laser beam to enter the scanner lens 12. The scanner lens 12 refracts the reference beam so as to reliably irradiate the hologram medium 24 with the reference beam from the dichroic mirror 11. As a result, the reference beam emitted from the laser device 5 enters the hologram at an incident angle when the hologram to be reproduced is recorded on the hologram medium 24. Further, the scanner lens 12 causes the servo laser beam from the dichroic mirror 11 to enter the hologram medium 24.

  The hologram medium 24 is made of a photosensitive resin that can store digital data as a hologram (for example, photopolymer, silver salt emulsion, gelatin dichromate, photoresist, etc.), and the photosensitive resin is sealed with a glass substrate. It is configured. The glass substrate constituting the hologram medium 24 is preliminarily provided with prepits indicating address information corresponding to the hologram to be recorded, as in the land prepit system used in, for example, a DVD (Digital Versatile Disk). Yes. Then, the servo laser beam from the servo laser device 19 is irradiated onto the prepit, and the servo laser beam after irradiating the prepit is incident on the detector 23.

  Hereinafter, the two-dimensional gray image pattern indicated by the hologram recorded on the hologram medium 24 will be described in detail with reference to FIG. When digital data is recorded as a hologram on the hologram medium 24, the digital data is rearranged into a two-dimensional data array as shown in FIG. 6A, and unit page array data is formed in an SLM (not shown). At this time, for example, nine pixels (a1 to a3, b1 to b3, c1 to c3, v1 to v3, w1 to w3, x1 to x3, a22 to a24, b22 to b24, c21 to c24 on each vertex side of the SLM, v22 to v24, w22 to w24, x22 to x24), for example, one logical value '1' is set as position error correction data (second data) in order to correct a position error of the image sensor 14 described later. The That is, the digital data recorded on the hologram medium 24 is arranged in pixels excluding the nine pixels × 4 described above. Then, the SLM forms a two-dimensional gray image pattern from the unit page arrangement data, with one logical value '1' being bright, for example, and the other logical value '0' being dark, for example (FIG. 6B). Then, when the laser beam is reflected by the SLM, the hologram medium 24 is irradiated with a beam reflecting the information of the two-dimensional grayscale image pattern (hereinafter referred to as a data beam) and a reference beam. As a result, a hologram showing a two-dimensional gray image pattern is recorded on the hologram medium 24.

  The Fourier transform lens 13 receives the reproduction beam from the hologram medium 24, performs an inverse Fourier transform on the reproduction beam, and enters the image sensor 14. The reproduction beam is a beam reflecting a two-dimensional gray image pattern (FIG. 6A) indicated by a hologram diffracted from the reference beam.

  The reproduction beam from the Fourier transform lens 13 is incident on the image sensor 14. Hereinafter, the configuration of the image sensor 14 will be described in detail with reference to FIGS. 7 to 9. The image sensor 14 includes a light receiving surface 25 (first light receiving portion), a four-divided sensor 26 (A) to 26 (D) (second light receiving portion), a PCB (Printed Circuit Board: printed circuit board) 27, a solenoid 28 ( X) (first solenoid), 28 (Y) (second solenoid), 28 (Z) (third solenoid), springs 29 (X) to 29 (Z), substrate 30, condenser lens 31 (A) to (D) It is made of glass 32.

  As shown in FIG. 7, the PCB 27 incorporates a light receiving surface 25 and four-divided sensors 26 (A) to 26 (D). Further, as shown in FIG. 8, the PCB 27 is provided with a glass 32 (or an optical filter) to protect the light receiving surface 25 and the four-divided sensors 26 (A) to 26 (D). Further, a reproduction beam (second reference beam) indicating the above-described position error correction data among the reproduction beams from the hologram medium 24 is condensed on the glass 32 on the four-divided sensors 26 (A) to 26 (D). The condensing lenses 31 (A) to (D) are provided as much as possible.

  The PCB 27 is elastically biased by the spring 29 (X), and the position in the X direction (first direction) is corrected and moved by the suction force of the solenoid 28 (X). More specifically, the solenoid 28 (X) is applied with a correction voltage (X) from an image sensor driving unit 18 to be described later, and is attracted according to the level of the correction voltage (X). The PCB 27 is corrected and moved in the −X direction against the elastic biasing in the + X direction by the spring 29 (X) by the suction force from the solenoid 28 (X). Then, the PCB 27 is held at a position where it is corrected and moved by the spring 29 (X) and the solenoid 28 (X).

  The PCB 27 is elastically biased by a spring 29 (Y), and the position in the Y direction (second direction) is corrected and moved by the suction force of the solenoid 28 (Y). More specifically, the solenoid 28 (Y) is applied with a correction voltage (Y) from an image sensor driving unit 18 to be described later, and is attracted according to the level of the correction voltage (Y). The PCB 27 is corrected and moved in the -Y direction against the elastic biasing in the + Y direction by the spring 29 (Y) by the suction force from the solenoid 28 (Y). Then, the PCB 27 is held at a position where it is corrected and moved by the spring 29 (Y) and the solenoid 28 (Y).

  The PCB 27 is configured to rotate in the Z direction (rotating direction) by a rotating shaft determined by the elastic bias from the springs 29 (X) and (Y) and the suction force from the solenoids 28 (X) and (Y). It has become. The PCB 27 is elastically biased by the spring 29 (Z), and the position in the Z direction is corrected and moved by the suction force of the solenoid 28 (Z). More specifically, the solenoid 28 (Z) is applied with a correction voltage (Z) from an image sensor driving unit 18 described later, and is attracted according to the level of the correction voltage (Z). The PCB 27 is corrected and moved in the -Z direction against the elastic biasing in the + Z direction by the spring 29 (Z) by the suction force from the solenoid 28 (Z). Then, the PCB 27 is held at a position where it is corrected and moved by the spring 29 (Z) and the solenoid 28 (Z).

  The light receiving surface 25 is a reproduction beam indicating digital data to be reproduced among the reproduction beams from the hologram medium 24, that is, a reproduction beam indicating digital data arranged in pixels excluding the nine pixels × 4 described above (hereinafter referred to as the first beam). The first reproduction beam is provided to receive the first reproduction beam. Therefore, the light receiving surface 25 is configured to have pixels (each grating shown in FIG. 7) for receiving the first reproduction beam. The shape of the light receiving surface 25 matches the two-dimensional grayscale image pattern (excluding 9 pixels × 4) shown in FIG. 6B. Each dot of the dimensional grayscale image pattern has the same shape. That is, when the first reproduction beam is accurately applied to the light receiving surface 25, the light receiving surface 25 and the two-dimensional gray image pattern are matched, and the two-dimensional gray image pattern is accurately reproduced on the light receiving surface 25. Become. As a result, accurate digital data can be reproduced from the two-dimensional gray image pattern reproduced on the light receiving surface 25. The light receiving unit 25 is composed of, for example, a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide Semiconductor). Then, the image sensor 14 transmits an analog signal, which is obtained as a result of converting the light intensity of the two-dimensional gray image pattern into the strength of the electric signal, based on the instruction signal from the image sensor control unit 15, to the filter 29.

  The condensing lenses 31 (A) to (D) convert a reproduction beam (hereinafter referred to as a second reproduction beam) indicating position error correction data out of the reproduction beam from the hologram medium 24 into four-divided sensors 26 (A) to (26). The second reproduction beam is condensed and emitted to the four-divided sensors 26 (A) to 26 (D) so as to be smaller than the light receiving region of 26 (D).

  The quadrant sensors 26 (A) to 26 (D) are provided on the outer peripheral side of the light receiving surface 25 and on the apex side of the light receiving surface 25 as shown in FIG. Further, the four-divided sensors 26 (A) to 26 (D) have four regions A to D that are each divided into two equal parts in the X direction and the Y direction shown in FIG. 9 (and FIG. 7). That is, the four-divided sensors 26 (A) to 26 (D) have four regions A to D having the same region area. The four-divided sensors 26 (A) to 26 (D) perform second reproduction from the condenser lenses 31 (A) to (D) in order to match the light receiving surface 25 and the two-dimensional gray image pattern. It is provided to receive the beam. More specifically, when the light receiving surface 25 and the two-dimensional gray image pattern are matched, the four divided sensors 26 (A) to 26 (D) irradiate the four regions A to D with the second reproduction beam evenly. It is provided so that. On the other hand, when the light receiving surface 25 and the two-dimensional gray image pattern are not matched, the four divided sensors 26 (A) to 26 (D) irradiate the four regions A to D with the second reproduction beam unevenly. It is provided so that. That is, it can be understood that the light receiving surface 25 and the two-dimensional gray image pattern are not matched by irradiating the four regions A to D with the second reproduction beam unevenly. It can be seen that a position error of the light receiving surface 25 occurs.

  The four-divided sensors 26 (A) to 26 (D) output analog signals corresponding to the light receiving areas of the second reproduction beam received in the four areas A to D to the operational amplifier 16. More specifically, the four-divided sensor 26 (A) has an analog signal AA corresponding to the light receiving area of the area A, an analog signal AB corresponding to the light receiving area of the area B, and an analog signal AC corresponding to the light receiving area of the area C. Then, an analog signal AD corresponding to the light receiving area of the area D is output to the operational amplifier 16. The quadrant sensor 26 (B) includes an analog signal BA corresponding to the light receiving area of the area A, an analog signal BB corresponding to the light receiving area of the area B, an analog signal BC corresponding to the light receiving area of the area C, An analog signal BD corresponding to the light receiving area of the area D is output to the operational amplifier 16. The quadrant sensor 26 (C) includes an analog signal CA corresponding to the light receiving area of the area A, an analog signal CB corresponding to the light receiving area of the area B, an analog signal CC corresponding to the light receiving area of the area C, An analog signal CD corresponding to the light receiving area of the area D is output to the operational amplifier 16. The quadrant sensor 26 (D) includes an analog signal DA corresponding to the light receiving area of the area A, an analog signal DB corresponding to the light receiving area of the area B, an analog signal DC corresponding to the light receiving area of the area C, An analog signal DD corresponding to the light receiving area of the area D is output to the operational amplifier 16. That is, the number of analog signals output from the four-divided sensors 26 (A) to 26 (D) to the operational amplifier 16 is 4 × 4 = 16. In FIG. 1, only one signal line from the image sensor 14 to the operational amplifier 16 is shown, but in actuality, it is the same as the number of signals (16) from the four-divided sensors 26 (A) to 26 (D). Sixteen signal lines are connected between the image sensor 14 and the operational amplifier 16.

  In the present embodiment, the four-divided sensors 26 (A) to 26 (D) are provided on the outer peripheral side of the light receiving surface 25 and on the apex side of the light receiving surface 25, but the present invention is not limited to this. The four-divided sensors 26 (A) to 26 (D) are provided at the positions in the present embodiment because the reproduction beam from the hologram medium 24 is usually circular as shown in FIG. The light intensity of the reproduction beam becomes small. For this reason, the portion where the reproduction beam is smaller than the reference (Vref) (that is, the portion where the four-divided sensors 26 (A) to 26 (D) in this embodiment are provided) is generally not used. Therefore, in the present embodiment, in order to effectively use this unused portion, it is provided on the outer peripheral side of the light receiving surface 25 and on the apex side of the light receiving surface 25.

  The operational amplifier 16 amplifies each analog signal (AA to AD, BA to BD, CA to CD, DA to DD) from the four-divided sensors 26 (A) to 26 (D) at a predetermined amplification factor and performs the calculation. To the unit 17. In the present embodiment, for convenience of explanation, the signal amplified by the operational amplifier 16 is also referred to as an analog signal (AA to AD, BA to BD, CA to CD, DA to DD).

  The arithmetic unit 17 is based on analog signals (AA to AD, BA to BD, CA to CD, DA to DD) from the operational amplifier 16 in the X direction, Y direction, and Z direction (FIGS. 7 and 9). Calculate the error. Hereinafter, the calculation of the position error by the calculation unit 17 will be described in detail.

  First, the position error (X) in the X direction will be described in detail. The computing unit 17 calculates a position error A (X) = (AA + AD) − (AB + AC) in the X direction of the four-divided sensor 26 (A) based on the analog signals AA to AD output from the operational amplifier 16. Further, the arithmetic unit 17 calculates a position error B (X) = (BA + BD) − (BB + BC) in the X direction of the quadrant sensor 26 (B) based on the analog signals BA to BD output from the operational amplifier 16. To do. Further, the arithmetic unit 17 calculates a position error C (X) = (CA + CD) − (CB + CC) in the X direction of the quadrant sensor 26 (C) based on the analog signals CA to CD output from the operational amplifier 16. To do. Further, the arithmetic unit 17 calculates a position error D (X) = (DA + DD) − (DB + DC) in the X direction of the quadrant sensor 26 (D) based on the analog signals DA to DD output from the operational amplifier 16. To do. Then, the calculation unit 17 calculates the position error (X) in the X direction from A (X) + B (X) + C (X) + D (X).

  Next, the position error (Y) in the Y direction will be described in detail. The calculation unit 17 calculates a position error A (Y) = (AD + AC) − (AA + AB) in the Y direction of the four-divided sensor 26 (A) based on the analog signals AA to AD output from the operational amplifier 16. In addition, the arithmetic unit 17 calculates a position error B (Y) = (BD + BC) − (BA + BB) in the Y direction of the four-divided sensor 26 (B) based on the analog signals BA to BD output from the operational amplifier 16. To do. Further, the arithmetic unit 17 calculates a position error C (Y) = (CD + CC) − (CA + CB) in the Y direction of the four-divided sensor 26 (C) based on the analog signals CA to CD output from the operational amplifier 16. To do. Further, the arithmetic unit 17 calculates a position error D (Y) = (DD + DC) − (DA + DB) in the Y direction of the quadrant sensor 26 (D) based on the analog signals DA to DD output from the operational amplifier 16. To do. Then, the computing unit 17 calculates a position error (Y) in the Y direction from A (Y) + B (Y) + C (Y) + D (Y).

  Next, the position error (Z) in the Z direction will be described in detail. Based on the calculated position errors B (X), D (X), C (Y), and A (Y), the arithmetic unit 17 calculates (C (Y) −A (Y)) − (B (X) − The position error (Z) in the Z direction is calculated from D (X)).

  The image sensor drive unit 18 generates a correction voltage (X) corresponding to the position error (X) from the calculation unit 17 and applies the correction voltage (X) to the solenoid 28 (X) in order to correct the position error in the X direction. Further, the image sensor driving unit 18 generates a correction voltage (Y) corresponding to the position error (Y) from the calculation unit 17 and applies it to the solenoid 28 (Y) in order to correct the position error in the Y direction. Further, the image sensor driving unit 18 generates a correction voltage (Z) corresponding to the position error (Z) from the calculation unit 17 and applies the correction voltage (Z) to the solenoid 28 (Z) in order to correct the position error in the Z direction.

  When the image sensor control unit 17 determines that the light amount of the two-dimensional gray image pattern reproduced on the light receiving surface 25 has reached a certain level or more, the image sensor control unit 17 transmits an instruction signal to generate the analog signal described above. To do. Further, the image sensor control unit 15 transmits an instruction signal indicating the determination result to the CPU 1 and the shutter control unit 7.

  The filter 19 performs a filtering process so as to improve the separability of the binarization process for the analog signal from the image sensor 14. For example, the two-dimensional gray image pattern reproduced by the image sensor 14 is clearer than the light and dark of the two-dimensional gray image pattern formed on the SLM (not shown) due to noise received by the data beam, reproduction beam, or the like. May not be reproduced. Therefore, it is not clear whether the level of the analog signal from the image sensor 14 is a level indicating 'bright' or a level indicating 'dark', and the binarization process may not be performed appropriately. Therefore, the level correction of the analog signal is performed by the filtering process by the filter 19. Note that a binarization processing unit (not shown) is provided between the filter 19 and the decoder 20, and the following description will be made assuming that the binarization processing is performed on the analog signal from the filter 19. A digital signal obtained as a result of the binarization processing by the binarization processing unit is transmitted to the decoder 20.

  The decoder 20 performs a decoding process on the digital signal from the binarization processing unit based on, for example, a data format of a predetermined standard. Decoding processing based on the data format of the predetermined standard includes, for example, demodulation of modulated data and error correction based on an error correction code. As a result of the decoding process performed by the decoder 20, digital data from the hologram to be reproduced is reproduced.

  The detector 21 is composed of, for example, a four-divided photodetector (not shown), and a servo laser beam after irradiating a prepit indicating address information of the hologram medium 24 is incident thereon. The detector 21 detects address information based on the received servo laser beam and transmits it to the CPU 1. The detector 21 transmits light amount information corresponding to the light amount of the received servo laser beam to the disk control unit 22. In FIG. 1, the detector 21 is provided to receive the servo laser beam transmitted through the hologram medium 24 after irradiating the pre-pits, but is not limited thereto. For example, when the servo laser beam after irradiating the prepit is reflected by the hologram medium 24, it may be provided to receive the reflected servo laser beam.

  The disk control unit 22 servo-controls the disk drive unit 23 based on the light amount information of the servo laser beam from the detector 21. In addition, the disk control unit 22 instructs the holographic medium 24 to move (hereinafter referred to as rotational driving) so as to irradiate the servo laser beam to the pre-pits indicating desired address information based on the instruction signal from the CPU 1. Is transmitted to the disk drive unit 23. The disk drive unit 23 rotates the hologram medium 24 based on the instruction signal from the disk control unit 22.

=== Operation of hologram reproducing apparatus ===
Hereinafter, the operation of the hologram reproducing apparatus according to the present invention will be described with reference to FIGS. 1, 7, 8, 11, and 12. FIG. 11 is a diagram showing irradiation of the reproduction beam and reception of the reproduction beam by the image sensor 14. FIG. 12 is a diagram schematically showing position errors of the four-divided sensors 26 (A) to 26 (D) shown in FIG.

  For example, when a reproduction instruction signal from a host device (not shown) such as a PC is transmitted to the hologram reproduction apparatus, the CPU 1 receives the reproduction instruction signal via the connection terminal 4 and the interface 3.

  The CPU 1 that has received the reproduction instruction signal reads out the address information of the hologram to be reproduced from the memory 2. Then, the CPU 1 transmits an instruction signal to the disk control unit 22 so as to irradiate the servo laser beam to the prepit indicating the address information read from the memory 2. Further, the CPU 1 reads out information on the incident angle of the reference beam from the memory 2 when the hologram to be reproduced is recorded. Then, the CPU 1 transmits an instruction signal to the galvo mirror control unit 9 so that the reference beam is incident on the hologram medium 24 at the incident angle read from the memory 2.

  The laser device 5 emits a reference beam to the shutter 6. The servo laser device 10 emits a servo laser beam to the dichroic mirror 11. The servo laser beam is reflected by the dichroic mirror 11 and enters the scanner lens 12. The servo laser beam from the scanner lens 12 irradiates a prepit provided on the hologram medium 24 and is received by the detector 21.

  The disk control unit 22 that has received the instruction signal from the CPU 1 transmits an instruction signal to the disk drive unit 23 so as to irradiate the servo laser beam to the pre-pits indicating desired address information based on the instruction signal. The disk drive unit 23 that has received the instruction signal from the disk control unit 22 rotates the hologram medium 24 based on the instruction signal. The detector 21 that has received the servo laser beam after irradiating the pre-pits indicating the address information of the hologram medium 24 detects the address information based on the servo laser beam and transmits it to the CPU 1.

  Further, the galvo mirror control unit 9 that has received the instruction signal from the CPU 1 controls the deflection angle of the galvo mirror 8 so as to determine the incident angle of the reference beam with respect to the hologram medium 24 based on the instruction signal. That is, by controlling the deflection angle of the galvo mirror 8, the reference beam is incident on the hologram medium 24 at the incident angle read from the memory 2 by the CPU 1.

  When the CPU 1 receives the address information from the detector 21 and determines that the address information matches the address information read from the memory 2, the CPU 1 transmits an instruction signal for opening the shutter 6 to the shutter control unit 7. To do. Then, the CPU 1 starts the timer 25 and determines whether or not the timer 25 has measured a predetermined time. And the shutter control part 7 which received the instruction | indication signal from CPU1 transmits an open state instruction | indication signal to the shutter 6 based on the said instruction | indication signal. The shutter 6 enters an open state based on the open state instruction signal. As a result, the reference beam from the laser device 5 enters the galvo mirror 8 through the shutter 6. The galvo mirror 8 deflects the reference beam in a state where the deflection angle is controlled by the galvo mirror controller 9 described above. The reference beam deflected by the galvo mirror 8 is refracted by the scanner lens 12 and enters the hologram medium 24. As a result, the reference beam is irradiated to the hologram to be reproduced.

  The reference beam incident on the hologram medium 24 is diffracted by the hologram to be reproduced to become the first reproduction beam and the second reproduction beam, and the first reproduction beam and the second reproduction beam are incident on the Fourier transform lens 13. The The first reproduction beam and the second reproduction beam are subjected to inverse Fourier transform by the Fourier transform lens 13. The first reproduction beam is incident on the light receiving surface 25 of the image sensor 14, and the second reproduction beam is incident on the condenser lenses 31 (A) to (D) (t0). The second reproduction beam is condensed by the condenser lenses 31 (A) to (D) and is incident on the four-divided sensors 26 (A) to 26 (D). The light receiving surface 25 reproduces a two-dimensional gray image pattern based on the received first reproduction beam.

  Hereinafter, a case where the light receiving surface 25 and the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25 are not matched will be described. That is, a case where a position error of the four-divided sensors 26 (A) to 26 (D) as shown in FIG. 12 occurs will be described.

  The four-divided sensor 26 (A) that receives the second reproduction beam in the four areas A to D includes an analog signal AA corresponding to the light receiving area of the area A, an analog signal AB corresponding to the light receiving area of the area B, The analog signal AC corresponding to the light receiving area in the area C and the analog signal AD corresponding to the light receiving area in the area D are output to the operational amplifier 16. The four-divided sensor 26 (B) that has received the second reproduction beam in the four areas A to D has an analog signal BA corresponding to the light receiving area of the area A and an analog signal BB corresponding to the light receiving area of the area B. The analog signal BC corresponding to the light receiving area in the area C and the analog signal BD corresponding to the light receiving area in the area D are output to the operational amplifier 16. The four-divided sensor 26 (C) that has received the second reproduction beam in the four areas A to D has an analog signal CA corresponding to the light receiving area of the area A and an analog signal CB corresponding to the light receiving area of the area B. Then, an analog signal CC corresponding to the light receiving region in region C and an analog signal CD corresponding to the light receiving region in region D are output to the operational amplifier 16. The four-divided sensor 26 (D) that has received the second reproduction beam in the four areas A to D has an analog signal DA corresponding to the light receiving area of the area A and an analog signal DB corresponding to the light receiving area of the area B. The analog signal DC corresponding to the light receiving area in the area C and the analog signal DD corresponding to the light receiving area in the area D are output to the operational amplifier 16.

  The operational amplifier 16 to which the analog signal AA from the quadrant sensor (A) is input amplifies the analog signal AA at a predetermined amplification factor and outputs the amplified analog signal AA to the arithmetic unit 17. The operational amplifier 16 to which the analog signal AB from the quadrant sensor (A) is input amplifies the analog signal AB at a predetermined amplification factor and outputs the amplified analog signal AB to the calculation unit 17. The operational amplifier 16 to which the analog signal AC from the quadrant sensor (A) is input amplifies the analog signal AC at a predetermined amplification factor and outputs the amplified analog signal AC to the arithmetic unit 17. The operational amplifier 16 to which the analog signal AD from the quadrant sensor (A) is input amplifies the analog signal AD at a predetermined amplification factor and outputs the amplified analog signal AD to the arithmetic unit 17.

  Similarly, the operational amplifier 16 to which the analog signal BA from the quadrant sensor (B) is input amplifies the analog signal BA at a predetermined amplification factor and outputs the amplified analog signal BA to the arithmetic unit 17. The operational amplifier 16 to which the analog signal BB from the quadrant sensor (B) is input amplifies the analog signal BB at a predetermined amplification factor and outputs the amplified analog signal BB to the calculation unit 17. The operational amplifier 16 to which the analog signal BC from the quadrant sensor (B) is input amplifies the analog signal BC at a predetermined amplification factor and outputs the amplified analog signal BC to the arithmetic unit 17. The operational amplifier 16 to which the analog signal BD from the quadrant sensor (B) is input amplifies the analog signal BD at a predetermined amplification factor and outputs the amplified analog signal BD to the arithmetic unit 17.

  Similarly, the operational amplifier 16 to which the analog signal CA from the quadrant sensor (C) is input amplifies the analog signal CA at a predetermined amplification factor and outputs the amplified analog signal CA to the arithmetic unit 17. The operational amplifier 16 to which the analog signal CB from the quadrant sensor (C) is input amplifies the analog signal CB at a predetermined amplification factor and outputs the amplified signal to the arithmetic unit 17. The operational amplifier 16 to which the analog signal CC from the quadrant sensor (C) is input amplifies the analog signal CC at a predetermined amplification factor and outputs the amplified analog signal CC to the calculation unit 17. The operational amplifier 16 to which the analog signal CD from the quadrant sensor (C) is input amplifies the analog signal CD at a predetermined amplification factor and outputs the amplified analog signal CD to the arithmetic unit 17.

  Similarly, the operational amplifier 16 to which the analog signal DA from the quadrant sensor (D) is input amplifies the analog signal DA at a predetermined amplification factor and outputs the amplified analog signal DA to the arithmetic unit 17. The operational amplifier 16 to which the analog signal DB from the quadrant sensor (D) is input amplifies the analog signal DB at a predetermined amplification factor and outputs the amplified analog signal DB to the arithmetic unit 17. The operational amplifier 16 to which the analog signal DC from the quadrant sensor (D) is input amplifies the analog signal DC at a predetermined amplification factor and outputs the amplified analog signal DC to the arithmetic unit 17. The operational amplifier 16 to which the analog signal DD from the quadrant sensor (D) is input amplifies the analog signal DD at a predetermined amplification factor and outputs the amplified analog signal DD to the arithmetic unit 17.

The arithmetic unit 17 to which analog signals (AA to AD, BA to BD, CA to CD, DA to DD) from the operational amplifier 16 are input is positioned in the X direction (FIGS. 7 and 9) based on the analog signal. The error (X) is calculated.
That is, the calculation unit 17
Position error (X) = A (X) + B (X) + C (X) + D (X) = {(AA + AD)-(AB + AC)} + {(BA + BD)-(BB + BC)} + {(CA + CD)-(CB + CC) )} + {(DA + DD)-(DB + DC)}
Position error (X) is calculated. As a result, the position errors of the four-divided sensors 26 (A) to 26 (D) in the X direction are calculated. That is, the position error in the X direction between the light receiving surface 25 and the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25 is calculated. When the light receiving surface 25 matches the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25, the position error (X) is zero.

Moreover, the calculating part 17 calculates the position error (Y) in a Y direction (FIG. 7, FIG. 9) based on an analog signal (AA-AD, BA-BD, CA-CD, DA-DD).
That is, the calculation unit 17
Position error (Y) = A (Y) + B (Y) + C (Y) + D (Y) = {(AD + AC)-(AA + AB)} + {(BD + BC)-(BA + BB)} + {(CD + CC)-(CA + CB) )} + {(DD + DC)-(DA + DB)}
The position error (Y) is calculated from As a result, the position errors of the four-divided sensors 26 (A) to 26 (D) in the Y direction are calculated. That is, the position error in the Y direction between the light receiving surface 25 and the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25 is calculated. When the light receiving surface 25 matches the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25, the position error (Y) is zero.

Moreover, the calculating part 17 calculates the position error (Z) in a Z direction (FIG. 7, FIG. 9) based on an analog signal (AA-AD, BA-BD, CA-CD, DA-DD).
That is, the calculation unit 17
Position error (Z) = (C (Y) −A (Y)) − (B (X) −D (X)) = [{(CD + CC) − (CA + CB)} − {(AD + AC) − (AA + AB)} ]-[{(BA + BD)-(BB + BC)}-{(DA + DD)-(DB + DC)}]
Position error (Z) is calculated. As a result, the position errors of the four-divided sensors 26 (A) to 26 (D) in the Z direction are calculated. That is, the position error in the Z direction between the light receiving surface 25 and the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25 is calculated. When the light receiving surface 25 and the two-dimensional gray image pattern indicated by the first reproduction beam received by the light receiving surface 25 are matched, the position error (Z) is zero.

  The image sensor driving unit 18 generates a correction voltage (X) corresponding to the position error (X) from the calculation unit 17 and applies it to the solenoid 28 (X). The solenoid 28 (X) to which the correction voltage (X) is applied attracts according to the level of the correction voltage (X). As a result, the PCB 27 is corrected and moved in the −X direction by the suction force of the solenoid 28 (X), and is held at the corrected and moved position by the spring 29 (X) and the solenoid 28 (X). That is, the light receiving surface 25 and the four-divided sensors 26 (A) to 26 (D) are corrected in the X direction. Further, the image sensor driving unit 18 generates a correction voltage (Y) corresponding to the position error (Y) from the calculation unit 17 and applies it to the solenoid 28 (Y). The solenoid 28 (Y) to which the correction voltage (Y) is applied attracts according to the level of the correction voltage (Y). As a result, the PCB 27 is corrected and moved in the −Y direction by the suction force of the solenoid 28 (Y), and is held at the corrected and moved position by the spring 29 (Y) and the solenoid 28 (Y). That is, the light receiving surface 25 and the four-divided sensors 26 (A) to 26 (D) are corrected in the Y direction. Further, the image sensor driving unit 18 generates a correction voltage (Z) corresponding to the position error (Z) from the calculation unit 17 and applies the correction voltage (Z) to the solenoid 28 (Z) in order to correct the position error in the Z direction. The solenoid 28 (Z) to which the correction voltage (Z) is applied attracts according to the level of the correction voltage (Z). As a result, the PCB 27 is corrected and moved in the −Z direction by the suction force of the solenoid 28 (Z), and is held at the corrected and moved position by the spring 29 (Z) and the solenoid 28 (Z). That is, the light receiving surface 25 and the four-divided sensors 26 (A) to 26 (D) are corrected in the Z direction. As described above, in the correction in the Z direction, the PCB 27 rotates on the rotation axis determined by the elastic bias from the springs 29 (X) and (Y) and the suction force from the solenoids 28 (X) and (Y). Correction in the direction to be performed (Z direction). As a result, it is possible to correct the position errors (X), (Y), and (Z) based on the second reproduction beam received by the four-divided sensors 26 (A) to (D) during t0t1. Become. That is, it is possible to perform reproduction processing based on the first reproduction beam without reproducing the first reproduction beam received by the light receiving surface 25 and correcting the position error.

  When the light receiving surface 25 receives the first reproduction beam for t0t1, the image sensor control unit 17 determines that the light quantity of the two-dimensional gray image pattern reproduced on the light receiving surface 25 has reached a certain level or more. Discriminate (t1). Then, the image sensor control unit 17 transmits an instruction signal to the image sensor 14 in order to generate an analog signal obtained as a result of converting the light intensity of the received two-dimensional gray image pattern into the strength of the electric signal. As a result, the correction in the case where there is the above-described position error between t0t1 is performed, and an analog signal is generated in a state where the light receiving surface 25 and the two-dimensional gray image pattern match. Next, the image sensor control unit 17 transmits an instruction signal indicating the determination result to the CPU 1 and the shutter control unit 7.

  Then, the image sensor 14 generates an analog signal from the two-dimensional gray image pattern based on the instruction signal from the image sensor control unit 15 and transmits the analog signal to the filter 29. The image sensor control unit 15 stops the generation of the analog signal by the image sensor 14 when the light receiving unit 25 reproduces a two-dimensional grayscale image pattern having a light amount of a certain level or more for a predetermined period (t1t2) (t2). ). Further, the shutter control unit 7 that has received the instruction signal from the image sensor control unit 15 transmits a closed state instruction signal to the shutter 6 based on the instruction signal. The shutter 6 is closed based on the closed state instruction signal. As a result, the reference beam from the laser device 5 is blocked by the shutter 6, and the first reproduction beam and the second reproduction beam are not incident on the image sensor 14 (t3). As a result, the reproduction process from the hologram is completed. In the present embodiment, the reproduction process is ended based on the instruction signal from the image sensor control unit 15, but the CPU 1 determines that the timer 25 has counted the predetermined time (at least the time between t0t2). In some cases, the reproduction process may be terminated.

  The filter 29 performs a filtering process on the analog signal from the image sensor 14. The analog signal from the filter 29 is subjected to binarization processing by a binarization processing unit (not shown) to become a digital signal, which is transmitted to the decoder 20. The decoder 20 performs a decoding process on the digital signal. As a result, digital data from the hologram to be reproduced is reproduced.

  According to the above-described embodiment, the light receiving surface 25 is two-dimensionally formed based on the second reproduction beam diffracted by the hologram indicating the position error correction data received by the four-divided sensors 26 (A) to 26 (D). It is possible to drive the correction to a position matching the grayscale image pattern. Then, it becomes possible to reproduce digital data based on the first reproduction beam received by the light receiving surface 25 that is corrected and driven to the matching position. As a result, it is possible to quickly generate an analog signal based on the two-dimensional gray image pattern by the image sensor 14. That is, it becomes possible to quickly perform the reproduction process of digital data from the hologram.

  Further, the position at which the light receiving surface 25 is matched by the image sensor driving unit 18 and the solenoids 28 (X) to (Z) until the two-dimensional grayscale image pattern reaches the amount of light that allows the image sensor 14 to generate an analog signal. Since the correction drive to the end is completed, digital data can be reproduced at high speed.

  In addition, if the second reproduction beam is larger than the light receiving area of the four-divided sensors 26 (A) to (D), the calculation unit 17 may not be able to calculate position errors in the X, Y, and Z directions. . However, the second reproduction beam is condensed by the condensing lenses 31 (A) to (D), and the condensed second reproduction beam is received by the four-divided sensors 26 (A) to (D). The calculation unit 17 can reliably calculate the position error in the X direction, the Y direction, and the Z direction. Further, since the second reproduction beam is condensed, the areas of the four-divided sensors 26 (A) to (D) can be reduced.

  Further, with respect to the hologram medium 24 in which the position error correction data is recorded as two or more (four in the present embodiment) holograms, the number of quadrant sensors 26 corresponding to the number of holograms indicating the position error correction data ( By providing A) to (D), the light receiving surface 25 can be corrected and driven to a position that more reliably matches. Further, by providing two or more four-divided sensors 26, not only the position error in the X direction and the Y direction but also the position error in the Z direction can be calculated by the calculation unit 17, and the position error Based on this, it becomes possible to perform correction driving in the Z direction of the light receiving surface 25.

  Further, by providing both the light receiving surface 25 and the four-divided sensors 26 (A) to (D) on the PCB 27, when the position error is calculated by the arithmetic unit 17, the light receiving surface 25 is displaced from the matching position. I can see that Further, by using the four-divided sensors 26 (A) to (D), the correction driving of the light receiving surface 25 in the X direction and the Y direction is surely performed based on the position error calculated by the calculation unit 17. Is possible.

  Further, when the PCB 27 is square and the reproduction beam is circular, the four-divided sensors 26 (A) to (D) can be provided at the four vertices of the PCB 27 where the light intensity of the reproduction beam becomes small. Become. As a result, the PCB 27 can be corrected and driven to a matching position by using the PCB 27 more effectively.

  Further, it becomes possible to correct and drive the position error in the X direction by the solenoid 28 (X). In addition, the position error in the Y direction can be corrected and driven by the solenoid 28 (Y). Further, it becomes possible to correct and drive the position error in the Z direction by the solenoid (Z).

  According to the above-described embodiment, the position error in the X direction, the Y direction, and the Z direction is calculated using the calculation unit 17 that is hardware. However, the present invention is not limited to this. For example, as shown in FIG. 13, an AD (Analog Digital) converter 33, a DSP (Digital Signal Processor) 34, and a DA (Digital Analog) converter 35 may be provided, and the arithmetic processing of the arithmetic unit 17 may be processed by software. In the following, the same components as those described above are denoted by the same reference numerals and description thereof is omitted, and the operation of the hologram reproducing device shown in FIG. 13 will be described.

  The AD converter 33 is a digital signal (AA-AD, BA-BD, CA-CD, DA) obtained by analog-digital conversion of the analog signal (AA-AD, BA-BD, CA-CD, DA-DD) from the operational amplifier 16. ~ DD) to DSP 34. The DSP 34 reads the program data from a memory (not shown) in which program data for performing the arithmetic processing of the arithmetic unit 17 is stored in advance. The DSP 34 performs arithmetic processing on the digital signals (AA to AD, BA to BD, CA to CD, DA to DD) from the AD converter based on the program data, and performs the X direction, the Y direction, and the Z direction. Position errors (X), (Y), and (Z) are calculated. The DA converter 35 sends the position errors (X), (Y), (Z) of the analog signals obtained by digital-analog conversion of the position errors (X), (Y), (Z) from the DSP 34 to the image sensor driving unit 18. Send. As a result, the same processing as the correction of the light receiving surface 25 and the four-divided sensors 26 (A) to (D) described above is performed.

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

<< Other Forms of Quadrant Sensor 26 >>
In the present embodiment, the four light sensors 26 are provided to correct the light receiving surface 25 and the four light sensors 26 (A) to (D), but the present invention is not limited to this. For example, as shown in FIG. 14, two quadrant sensors 26 (E) and (F) can be provided. Hereinafter, the processing operation of the hologram reproducing apparatus when a position error as shown in FIG. 15 occurs in the four-divided sensors 26 (E) and (F) shown in FIG. 14 will be described. The four-divided sensors 26 (E) and (F) have four areas A to D as in the four-divided sensors 26 (A) to (D).

  The four-divided sensor 26 (E) that has received the second reproduction beam in the four areas A to D includes an analog signal EA corresponding to the light receiving area of the area A, an analog signal EB corresponding to the light receiving area of the area B, An analog signal EC corresponding to the light receiving area of area C and an analog signal ED corresponding to the light receiving area of area D are output to the operational amplifier 16. The four-divided sensor 26 (F) that has received the second reproduction beam in the four areas A to D has an analog signal FA corresponding to the light receiving area of the area A and an analog signal FB corresponding to the light receiving area of the area B. The analog signal FC corresponding to the light receiving area of the area C and the analog signal FD corresponding to the light receiving area of the area D are output to the operational amplifier 16.

  The operational amplifier 16 amplifies each analog signal (EA to ED, FA to FD) from the four-divided sensors 26 (E) and (F) at a predetermined amplification factor and outputs the amplified signal to the arithmetic unit 17. In the present embodiment as well, for convenience of explanation, the signal amplified by the operational amplifier 16 will be referred to as analog signals (EA to ED, FA to FD) and will be described below.

The arithmetic unit 17 to which the analog signals (EA to ED, FA to FD) from the operational amplifier 16 are input calculates a position error (X) in the X direction based on the analog signals.
That is, the calculation unit 17
Position error (X) = E (X) + F (X) = {(EA + ED)-(EB + EC)} + {(FA + FD)-(FB + FC)}
Position error (X) is calculated.

The computing unit 17 calculates a position error (Y) in the Y direction based on the analog signals (EA to ED, FA to FD). That is, the calculation unit 17
Position error (Y) = E (Y) + F (Y) = {(ED + EC)-(EA + EB)} + {(FD + FC)-(FA + FB)}
The position error (Y) is calculated from

Moreover, the calculating part 17 calculates the position error (Z) in a Z direction based on analog signals (EA-ED, FA-FD). That is, the calculation unit 17
Position error (Z) = (F (Y) −E (Y)) − (F (X) −E (X)) = [{(FD + FC) − (FA + FB)} − {(ED + EC) − (EA + EB)} ]-[{(FA + FD)-(FB + FC)}-{(EA + ED)-(EB + EC)}]
Position error (Z) is calculated.

  Then, the position errors (X), (Y), and (Z) calculated by the calculation unit 17 are transmitted to the image sensor driving unit 18 to correct the position errors in the X direction, the Y direction, and the Z direction. Can be done. As a result, even when two quadrant sensors are provided, it is possible to correct the light receiving surface 25 in the X direction, the Y direction, and the Z direction. Therefore, the configuration of the hologram reproducing apparatus can be further simplified. In addition, it is possible to reduce the burden on the calculation processing by the calculation unit 17. That is, it is possible to provide the number of four-divided sensors 26 according to the accuracy of calculating the position error in the X direction, the Y direction, and the Z direction. Note that the number of the four-divided sensors 26 is not limited to two or four. By providing two or more quadrant sensors 26, position errors in the X direction, the Y direction, and the Z direction can be corrected.

It is a figure which shows an example of the whole structure of the hologram reproduction 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 which shows a two-dimensional grayscale image pattern and a light-receiving surface. It is a figure which shows irradiation of the reproduction | regeneration beam, and light reception of the said reproduction | regeneration beam by an image sensor. It is a figure which shows the unit page arrangement | sequence data of a hologram recorded on the hologram medium 24, and a two-dimensional gray image pattern. 2 is a front view of the image sensor 14. FIG. 2 is a cross-sectional view of the image sensor 14. FIG. It is the figure which showed four area | region AD of 4 division | segmentation sensor 26 (A)-(D). It is a figure which shows the optical intensity of a reproduction beam. It is a figure which shows irradiation of the reproduction | regeneration beam, and light reception of the said reproduction | regeneration beam by the image sensor. It is the figure which showed typically the position error of 4-part dividing sensor 26 (A)-26 (D) shown in FIG. It is a figure which shows the other form of the hologram reproduction apparatus which concerns on this invention. It is a figure which shows the other form of the 4-part dividing sensor. It is the figure which showed typically the position error of 4-part dividing sensor 26 (E) and (F) shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CPU 2 Memory 3 Interface 4 Connection terminal 5 Laser apparatus 6 Shutter 7 Shutter control part 8 Galvo mirror 9 Galvo mirror control part 10 Servo laser apparatus 11 Dichroic mirror 12 Scanner lens 13 Fourier transform lens 14 Image sensor 15 Image sensor control part 16 Operational amplifier 17 Operation unit 18 Image sensor drive unit 19 Filter 20 Decoder 21 Detector 22 Disk control unit 23 Disk drive unit 24 Hologram medium 25 Timer 26 Quadrant sensor 27 PCB 28 Solenoid 29 Spring 30 Substrate 31 Condensing lens 32 Glass 33 AD converter 34 DSP
35 DA converter

Claims (10)

A reference beam incident section for injecting a coherent reference beam to a hologram medium in which second data for adjusting a light receiving position is recorded as a hologram together with first data to be reproduced;
A first light receiving unit for receiving the first reference beam after the reference beam from the reference beam incident unit is diffracted by the hologram indicating the first data;
A second light receiving unit that receives the second reference beam after the reference beam from the reference beam incident unit is diffracted by the hologram indicating the second data;
The second reference beam received by the second light receiving unit and the second reference beam to be received by the second light receiving unit when the first light receiving unit is at a reference position matching the first reference beam. And a calculation unit for calculating the position error of
A correction driving unit that correctively drives the first light receiving unit to the reference position based on the position error when the position error is calculated by the calculating unit;
The first reference beam received by the first light receiving unit when the calculation unit does not calculate the position error, or the correction driving unit after the first light receiving unit is corrected and driven to the reference position. A reproducing unit for reproducing the first data based on the first reference beam received by the first light receiving unit,
A hologram reproducing apparatus characterized by that. The playback unit
When the light amount of the first reference beam received by the first light receiving unit reaches a predetermined value, a processing operation is started to reproduce the first data based on the first reference beam,
The correction drive unit
The correction driving of the first light receiving unit to the reference position is completed until the light amount of the first reference beam received by the first light receiving unit reaches the predetermined value;
The hologram reproducing apparatus according to claim 1, wherein: The second reference beam provided between the hologram medium and the second light receiving unit, and condensing the second reference beam from the hologram medium into a beam smaller than a region for receiving the beam in the second light receiving unit. 2 with a condenser lens that emits light to the light receiving part
The hologram reproducing apparatus according to claim 1, wherein the hologram reproducing apparatus is characterized in that: The second light receiving unit is provided on an outer peripheral side of the first light receiving unit.
4. The hologram reproducing apparatus according to claim 1, wherein the hologram reproducing apparatus is characterized in that: In the hologram medium, the second data is recorded as two or more holograms,
The second light receiving units are provided in a number corresponding to the hologram indicating the second data in a one-to-one relationship.
The calculating unit includes the second reference beam received by the second light receiving unit, a second reference beam to be received by the second light receiving unit when the first light receiving unit is at the reference position, To calculate the position error of
5. The hologram reproducing apparatus according to claim 1, wherein the hologram reproducing apparatus is characterized in that: The second light receiving unit includes:
A four-divided sensor having four regions formed by dividing a region for receiving the second reference beam into a first direction and a second direction orthogonal to the first direction. Because
The first light receiving unit and the four-divided sensor are provided at positions that can be corrected in the first direction and the second direction on the same substrate,
The calculation unit includes:
When the quadrant sensor receives the second reference beam,
A position error in the first direction is calculated from a difference between the light receiving region in the two regions on one side and the light receiving region in the two regions on the other side divided into two equal parts in the first direction;
A position error in the second direction is calculated from a difference between the light receiving region in the two regions on one side and the light receiving region in the two regions on the other side divided into two equal parts in the second direction;
The correction drive unit
Based on the position error when the position error in the first direction is calculated by the calculation unit, the substrate is corrected and driven in the first direction,
Based on the position error when the position error in the second direction is calculated by the calculation unit, the substrate is corrected and driven in the second direction.
6. The hologram reproducing apparatus according to claim 1, wherein the hologram reproducing apparatus is characterized in that: The substrate is
Two quadrant sensors are provided,
The calculation unit includes:
The difference between the position error of one quadrant sensor in the second direction and the position error of the other quadrant sensor in the second direction, the position error of the one quadrant sensor in the first direction, and the A position error in a direction in which the substrate rotates on a plane determined by the first direction and the second direction is calculated from the difference between the position error in the first direction of the other four-divided sensor. ,
The correction drive unit
Based on the position error when the position error in the rotation direction is calculated by the calculation unit, the substrate is corrected and driven in the rotation direction.
The hologram reproducing apparatus according to claim 6. The substrate is
A quadrangular shape, and the four-divided sensors are provided on the four vertex sides,
The calculation unit includes:
A position error in the second direction of the first four-divided sensor and a difference in position error in the second direction of the second four-divided sensor on the same diagonal as the first four-divided sensor;
The difference between the position error in the first direction of the third quadrant sensor and the difference in position error in the first direction of the fourth quadrant sensor on the same diagonal as the second quadrant sensor. From the difference, a position error in a direction in which the substrate rotates on a plane determined by the first direction and the second direction is calculated.
The correction drive unit
Based on the position error when the position error in the rotation direction is calculated by the calculation unit, the substrate is corrected and driven in the rotation direction.
The hologram reproducing apparatus according to claim 6. The correction drive unit
A first solenoid that correctively drives the substrate in the first direction;
A second solenoid that correctively drives the substrate in the second direction;
A third solenoid that correctively drives the substrate in the rotating direction;
The first solenoid corrects and drives the substrate in the first direction based on a position error in the first direction from the calculation unit;
The second solenoid corrects and drives the substrate in the second direction based on a position error in the second direction from the calculation unit,
The third solenoid corrects and drives the substrate in the rotation direction based on a position error in the rotation direction from the calculation unit.
9. The hologram reproducing apparatus according to claim 7, wherein the hologram reproducing apparatus is characterized in that: A reference beam incident part for injecting a coherent reference beam to a hologram medium in which second data for adjusting a light receiving position is recorded as a hologram together with first data to be reproduced, and from the reference beam incident part And a light receiving unit for receiving the first reference beam after the reference beam is diffracted by the hologram indicating the first data,
Receiving the second reference beam after the reference beam from the reference beam incident part is diffracted by the hologram indicating the second data;
Calculating a position error between the received second reference beam and the second reference beam to be received when the light receiving unit is at a reference position matching the first reference beam;
Based on the position error when the position error is calculated, the light receiving unit is corrected and driven to the reference position,
Based on the first reference beam received by the light receiving unit when the position error is not calculated, or the first reference beam received by the light receiving unit after the light receiving unit is corrected and driven to the reference position. And reproducing the first data,
A reproducing method for a hologram reproducing apparatus.

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