JP2006195212A - Hologram recording/reproducing device and hologram recording/reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording/reproducing device obtaining a hologram reproduced signal high in reliability without requiring a complicated signal processing hardware. <P>SOLUTION: The hologram recording/reproducing device has a hologram media moving mechanism controlling positions on a linear scale, and, at the time of hologram reproducing, the reproduced image data of a hologram recording position and the respective positions shifted to the front and rear thereof by optical distance are fetched, and the data in which S/N is the best are extracted from the plurality of reproduced image data, thereby obtaining the reproduced signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hologram recording / reproducing apparatus and a hologram recording / reproducing method for performing recording using a hologram.

  In recent years, photopolymer hologram recording materials have become mainstream as multiholographic recording materials for reasons such as high resolution, high diffraction efficiency, and low cost.

  As one of the methods for holographic multiplex recording, a method called shift multiplex recording that enables high-density recording by shifting (shifting laterally) a smaller distance than the size of the hologram pattern formed on the medium. There is.

In multiplex recording, a method called scheduling recording is employed in order to effectively utilize the dynamic range of the photopolymer hologram recording material. For example, the first time is a method of recording with the power reduced and recording with gradually increasing the recording power.
JP 2001-343215 A JP 2002-56552 A JP 2002-63333 A

  However, if the hologram recording interval is narrowed in shift multiplex recording, at the time of hologram reproduction, the influence of the crosstalk signal from the hologram increases at adjacent positions, which hinders improvement in recording density. This crosstalk is considered to be one of the causes of the occurrence of the volume shrinkage of the hologram medium due to the polymerization during hologram recording, resulting in a deviation in the reproduction signal output direction.

  Further, in order to reduce the reproduction noise with the optical system, it is necessary to make a fine adjustment of the optical system, and there is a problem that it is extremely difficult.

  Known techniques for solving this problem include a method of reducing noise by hologram position control during reproduction (for example, see Patent Document 1), and a method of servoing the position of a hologram medium with a signal of a reproduced image (for example, Patent Documents 2 and 3). See).

  In the case where the servo control of the position of the hologram medium is performed at the time of hologram reproduction, it is difficult to increase the speed because of the mechanical operation, and it is considered difficult to reduce the size and simplify the mechanism for fixing the hologram medium.

  In view of the circumstances as described above, it is an object of the present invention to provide a hologram recording / reproducing apparatus and a hologram recording / reproducing method capable of obtaining a highly reliable hologram reproduction signal without requiring complicated signal processing hardware. .

  In order to solve the above problems, a hologram recording / reproducing apparatus according to the present invention includes a medium moving unit that moves a hologram recording medium along a recording surface and a movement of the hologram recording medium by the medium moving unit during hologram reproduction. The reproduction image reading means for reading out the hologram recording position of the hologram recording medium and the reproduction image data at each position shifted forward and backward from the hologram recording position by the fixed distance, and each reproduction image read by the reproduction image reading means Signal processing means for selecting reproduced image data having the highest signal quality from the data to obtain a reproduced signal. By having this configuration, a highly reliable hologram reproduction signal can be obtained without requiring complicated signal processing hardware.

  The hologram recording / reproducing apparatus according to the present invention further includes movement measurement means for detecting a movement of the hologram recording medium at a certain distance to generate a pulse, and the medium movement means includes a movement measurement means at the time of hologram recording. The hologram recording medium may be moved to a target recording position while correcting the movement amount using the output. Accordingly, the hologram recording medium can be moved to a target recording position with high accuracy during hologram recording without using an expensive servomotor.

  The hologram recording / reproducing apparatus according to the present invention further includes storage means for storing the number of output pulses of the movement measurement means until the hologram recording medium is moved to the target recording position during hologram recording as information on the recorded recording position. Then, the medium moving means shifts the hologram recording medium from the hologram recording position and a certain distance forward and backward from the hologram recording position based on the information of the recorded recording position stored in the storage means at the time of reproducing the hologram. You may comprise so that it may move to a position.

  With such a configuration, the hologram recording medium can be moved with high accuracy to the hologram recording position and each position shifted forward and backward from the hologram recording position during hologram reproduction.

  Furthermore, the hologram recording / reproducing apparatus according to the present invention includes a reference position returning unit that returns the hologram recording medium to the reference position before starting recording, in order to move the hologram recording medium with high accuracy. It is beneficial. In particular, a linear scale can be used as the movement measurement means, and when this linear scale is used, the hologram recording medium is returned to the reference position using a Z-phase signal located at the center of the linear scale. To do.

  In the hologram recording / reproducing apparatus according to the present invention, more specifically, the signal processing means calculates S / N for each reproduced image data at each position, and selects reproduced image data having the best S / N. It can be configured. As a result, it is possible to more accurately select reproduced image data with high signal quality and obtain a highly reliable hologram reproduction signal.

  A hologram recording / reproducing method based on another aspect of the present invention reads a hologram recording position of a hologram recording medium and reproduction image data at each position shifted an arbitrary distance forward and backward from the hologram recording position during hologram reproduction, A reproduction signal is obtained by selecting reproduction image data having the highest signal quality from the read reproduction image data. According to the present invention, a highly reliable hologram reproduction signal can be obtained without requiring complicated signal processing hardware.

  Further, the hologram recording / reproducing method according to the present invention is provided with movement measurement means for detecting a movement of the hologram recording medium at a certain distance and generating a pulse, and using the output of the movement measurement means at the time of hologram recording. The hologram recording medium may be moved to a target recording position while correcting the movement amount. Accordingly, the hologram recording medium can be moved to a target recording position with high accuracy during hologram recording without using an expensive servomotor.

  Furthermore, in the hologram recording / reproducing method according to the present invention, the number of output pulses of the movement measuring means until the hologram recording medium is moved to the recording position at the time of hologram recording is stored as information on the recorded recording position. At the time of reproduction, the hologram recording medium may be moved to the hologram recording position and each position shifted an arbitrary distance forward and backward from the hologram recording position based on the recorded information of the recorded recording position. .

  With this configuration, the hologram recording medium can be moved with high accuracy to the hologram recording position and each position shifted forward and backward from the hologram recording position during hologram reproduction.

  Furthermore, in the hologram recording / reproducing method according to the present invention, it is beneficial to have a procedure for returning the hologram recording medium to a reference position before starting recording in order to move the hologram recording medium with high accuracy. A linear scale can be used as the movement measurement means, and when this linear scale is used, the hologram recording medium may be returned to the reference position using the Z-phase signal located at the center of the linear scale. .

  In the hologram recording / reproducing method according to the present invention, the S / N may be calculated for each reproduced image data at each position, and the reproduced image data having the best S / N may be selected. As a result, it is possible to more accurately select reproduced image data with high signal quality and obtain a highly reliable hologram reproduction signal.

  As described above, according to the present invention, it is possible to provide a hologram recording / reproducing apparatus and a hologram recording / reproducing method capable of obtaining a highly reliable hologram reproduction signal without requiring complicated signal processing hardware.

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

  FIG. 1 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to an embodiment of the present invention.

  A hologram recording / reproducing apparatus according to this embodiment includes a CPU (Central Processing Unit), an analog image frame grabber 2, a pulse counter 3, a pulse motor / servo motor control board (motor control circuit) 4, and a digital image frame grabber 5. , LD (laser diode) power supply device 6, external resonator type LD7 (hereinafter referred to as LD7), isolator 8, mechanical shutter 9, half-wave plate 10, beam splitter 11, wedge prism 12, analog CCD camera 13, mirror 14a , 14b, 14c, 14d, beam splitter 15, diffuser plate 16, compound lens 17, signal light mechanical shutter 18, beam expander 19, mirror 20, band pass filter 21, GLV (Grating Light Valve) 22, recording lens 23, Slit 25 A reproduction lens 26, a cylindrical lens 27, a CCD linear sensor 28, a hologram media stage 29, an X-axis pulse motor 30, a Y-axis pulse motor 31, an X-axis linear scale 32, a Y-axis linear scale 33, and a bus 34 I have.

  The CPU 1 is, for example, a PC (Personal Computer) or the like, and comprehensively controls the hologram recording / reproducing apparatus of this embodiment.

  The analog image frame grabber 2 captures an image of an analog CCD (Charge-Coupled Devices) camera 13.

  The pulse counter 3 reads encoder pulses from an X-axis linear scale 32 and a Y-axis linear scale 33 attached to a hologram media stage 29 described later and notifies the CPU 1 of the encoder pulses.

  The motor control circuit 4 is a controller that controls an X-axis pulse motor 30 and a Y-axis pulse motor 31 that move a hologram media stage 29, which will be described later, in two axes. The amount of movement is determined by the number of output pulses. It is a controller that can control the moving speed by frequency.

  The digital image frame grabber 5 converts the hologram reproduction signal output from the CCD linear sensor 28 into digital data with a resolution of 8 bits, and transfers the data to the memory in the CPU 1 at high speed.

  The LD power supply device 6 and the LD 7 are elements constituting a laser light source. In this embodiment, a blue LD having a wavelength of 410 nm is used as the LD 7.

  The isolator 8 is an optical component that allows light to travel only in one direction and not in the reverse direction. In this embodiment, the isolator 8 has a role of blocking light returned to the LD 7.

  The mechanical shutter 9 is a shutter that also serves to control the exposure time during hologram recording. The exposure time for forming the hologram pattern on the hologram medium 24 is determined by the opening time of the mechanical shutter 9.

  The half-wave plate 10 is an optical component that adjusts the laser power.

  The beam splitter 11 is an optical component that divides laser light into a hologram recording optical path and an LD stable state monitoring optical path.

  The wedge prism 12 is an optical component that forms interference fringes for laser monitoring from the light split by the beam splitter 11 into the LD stable state monitoring optical path.

  The analog CCD camera 13 captures the interference fringe image formed by the wedge prism 12 and transfers it to the CPU 1. The CPU 1 can confirm the oscillation state of the LD 7 by visual observation, for example, by displaying the interference fringe image captured by the analog CCD camera 13 on the monitor.

  The mirror 14 a is an optical component that reflects the light on the hologram recording optical path and enters the beam splitter 15.

  The beam splitter 15 is an optical component that separates incident light into signal light and reference light.

  The mirror 14 b is a mirror that reflects the reference light incident from the beam splitter 15 and enters the diffusion plate 16.

  The diffusion plate 16 is an optical component that diffuses the reference light separated by the beam splitter 15 and enters the compound lens 17.

  The compound lens 17 is an optical component that collects the diffused light from the diffuser plate 16 and emits it as a reference light laser beam.

  The signal light mechanical shutter 18 is opened only during hologram recording, and the signal light separated by the beam splitter 15 enters the beam expander 19 when opened. The signal light mechanical shutter 18 is closed during hologram reproduction.

  The mirror 14 c and the mirror 14 d are optical components that reflect the signal light incident from the beam expander 19 and enter the bandpass filter 21.

  The band-pass filter 21 is an optical component that reflects the signal light incident from the mirror 14 d upward, enters the GLV 22, transmits the signal light reflected from the GLV 22, and enters the recording lens 23.

  The GLV 22 is a reflective one-dimensional spatial modulator. In this GLV 22, 1088 pixels are arranged in a line. The size of one pixel is 25.5 μm. The GLV 22 pattern-modulates signal light by setting ON / OFF of each pixel during hologram recording.

  The mirror 20 is a mirror that reflects the reference light laser beam incident from the compound lens 17 downward and enters the recording lens 23.

  The recording lens 23 is an optical component for forming a hologram pattern by irradiating the reference light from the mirror 20 and the signal light from the band pass filter 21 to substantially the same location of the hologram medium 24 through the slit 25.

  The reproduction lens 26 is an optical component that collects light (reproduction light) transmitted through the hologram medium 24 during hologram reproduction.

  The cylindrical lens 27 is an optical component that focuses the reproduction light collected by the reproduction lens 26 on each element of the CCD linear sensor 28.

  The CCD linear sensor 28 is a sensor that receives reproduction light, converts it into an electrical signal, and outputs it to the digital image frame grabber 5.

  The hologram media stage 29 is a stage on which the hologram medium 24 is mounted and moves in the biaxial direction. The hologram media stage 29 is driven by the X-axis pulse motor 30 and the Y-axis pulse motor 31 with high resolution in the biaxial direction. The driving of the X-axis pulse motor 30 and the Y-axis pulse motor 31 is controlled by the motor control circuit 4 to position the hologram medium 24 in the two-axis directions. The hologram media stage 29 is provided with an X-axis linear scale 32 and a Y-axis linear scale 33 so that the stage position can be strictly managed.

  The X-axis linear scale 32 and the Y-axis linear scale 33 are movement measurement means for detecting a movement of the hologram media stage 29 at a certain distance and generating pulses. The mechanism for strictly managing the position of the hologram media stage 29 is provided in addition to the X-axis pulse motor 30 and the Y-axis pulse motor 31 being open-loop control, and the hologram recording of the present embodiment. In the reproducing apparatus, the hologram media 24 is read from the recording position and each position shifted by a minute distance before and after the recording position during hologram reproduction, whereas the guide rail that supports the hologram media stage 29 is caused by distortion due to thermal deformation or the like. This is because the sliding ability fluctuates and accurate positioning control is predicted to be impossible.

  The CPU 1, the analog image frame grabber 2, the pulse counter 3, the motor control circuit 4, and the digital image frame grabber 5 are connected through a bus 34 so that they can communicate with each other.

  Next, the operation of this hologram recording / reproducing apparatus will be described.

  First, the operation during hologram recording will be described.

  FIG. 2 is a flowchart showing the operation of hologram recording in the hologram recording / reproducing apparatus of this embodiment.

  First, in step S1, it is necessary to irradiate the hologram medium 24 with incoherent light such as an LED at a recording position on the hologram medium 24 before recording to perform a process for improving sensitivity and diffraction efficiency. This is called pre-exposure.

  Next, in step S2, the laser power of the LD 7 is set. In this system, the laser power is adjusted by changing the rotation angle of the half-wave plate 10 without changing the power output of the LD 7.

  The motor shafts of the X-axis pulse motor 30 and the Y-axis pulse motor 31 of the hologram media stage 29 are moved when the power is not turned on or when the control software is stopped. In this case, the CPU 1 cannot obtain the correct position information of the hologram media stage 29. Therefore, in step S3, before executing the recording sequence, origin detection processing (origin return) is performed so that the position information of each motor shaft can be obtained. That is, this process is for realizing management in the machine coordinate system with the reference position set on the hologram recording / reproducing apparatus of the present embodiment as the origin, and in the hologram recording / reproducing apparatus of the present embodiment, Origin detection processing (origin return) is performed using a Z-phase signal located at the center of each of the linear scales 32 and 33.

  In step S4, a recording schedule parameter is created to effectively use the dynamic range of the hologram medium 24. The recording schedule parameters include, for example, the recording pitch, the opening time (exposure time) of the mechanical shutter 9, and the rotation angle (recording power) of the half-wave plate 10.

  Subsequently, in step S5, whether or not the LD 7 is oscillating in a stable state is confirmed by, for example, visually checking the interference fringe image captured from the wedge prism 12 by the analog CCD camera 13 on the monitor of the CPU 1. .

  In step S6, the CPU 1 sends a data pattern from the flash memory of the CPU 1 to a GLV controller (not shown) so as to transfer the data to the GLV 22 for the next hologram recording.

  Next, in step S7, the hologram media stage 29 is moved to the hologram recording position. At this time, the CPU 1 inputs a positioning pulse corresponding to the amount of movement to the motor control circuit 4.

  Subsequently, in step S8, the CPU 1 checks the encoder pulse of the X-axis linear scale 32 and the Y-axis linear scale 33 in order to confirm whether or not the target recording position has been reached accurately after the hologram media stage 29 is stopped. Is read by the pulse counter 3.

  If there is a difference between the stop position of the hologram media stage 29 and the target recording position, the CPU 1 checks the encoder pulses of the X-axis linear scale 32 and the Y-axis linear scale 33 in step S9. However, a pulse corresponding to the above difference amount is calculated, and a movement amount correction process is performed.

  After completing the correction of the movement amount, in step S10, the apparatus waits for a settling time set in consideration of the adverse effect on the hologram recording caused by the mechanical vibration caused by the movement of the hologram media stage 29.

  After the settling time has elapsed, in step S11, the CPU 1 reads the encoder pulses of the X-axis linear scale 32 and the Y-axis linear scale 33 at the stop position of the hologram media stage 29 with the pulse counter 3, and uses this as the recording position. Store in memory.

  Next, in step S12, the mechanical shutter 9 is opened and exposure for hologram recording is started.

  In step S13, the exposure time is monitored by a timer. When a predetermined exposure time has elapsed, the mechanical shutter 9 is closed in step S14.

  Thereafter, in step S15, the CPU 1 confirms whether or not all hologram recording has been completed. If not, the process returns to step S5. If completed, step S16 is executed.

  In hologram recording using a photopolymer, if there is an unreacted monomer due to insufficient recording, an additional recording state is caused by irradiation of reference light during reproduction, which causes recorded hologram reproduction noise. For this reason, in step S16, the unreacted monomer is changed to a polymer by irradiating the hologram medium 24 with incoherent light as in the pre-exposure. This is called post-exposure.

  Next, the operation at the time of hologram reproduction will be described.

  FIG. 3 is a flowchart showing the hologram reproducing operation in the hologram recording / reproducing apparatus of this embodiment.

  In this hologram recording / reproducing apparatus, a hologram recording position and a reproduced image at each position shifted a predetermined distance forward and backward from the recording position are read. Therefore, the reproduced image is read a total of three times for one hologram. In the recording sequence, the LD 7 needs to confirm the stable oscillation. However, from the experimental result, the hologram can be reproduced even if the LD 7 does not oscillate stably.

  First, in step S21, the output power of the LD 7 is set. As with the recording sequence, the laser power is adjusted by changing the rotation angle of the half-wave plate 10 without changing the power output of the LD 7. The laser power during reproduction is set higher than that during recording.

  Next, in step S22, as in the recording sequence, origin detection processing (origin return) is performed. In step S23, since no recording light is required during reproduction, the signal light mechanical shutter 18 for shielding the signal light is closed.

  Next, in step S24, the mechanical shutter 9 is opened.

  In step S25, the CPU 1 reads the hologram recording position from the internal memory, and calculates a recording position shifted from the position by a bias (an arbitrary distance) for each of the front and rear.

  In step S26, the hologram media stage 29 is moved from the recording position to the forward shift recording position calculated in step S25. Also at this time, a positioning pulse corresponding to the amount of movement is input from the CPU 1 to the motor control circuit 4.

  In step S27, after the hologram media stage 29 is stopped, the CPU 1 pulses encoder pulses of the X-axis linear scale 32 and the Y-axis linear scale 33 in order to confirm whether or not the front shift recording position has been reached accurately. Read with the counter 3.

  If there is a difference between the stop position of the hologram media stage 29 and the forward shift recording position, the CPU 1 checks the encoder pulses of the X-axis linear scale 32 and the Y-axis linear scale 33 in step S28. While calculating the pulse according to the difference amount, the movement amount is corrected.

  After completing the correction of the movement amount, in step S29, the apparatus waits for a settling time set in consideration of the adverse effect on the hologram recording due to the mechanical vibration caused by the movement of the hologram media stage 29.

  After the settling time has elapsed, in step S30, the CPU 1 acquires reproduced image data by the CCD linear sensor 28, and transfers the data to the memory in the CPU 1.

  Next, in step S31, the hologram recording position stored in the memory in the CPU 1 is read, and the hologram media stage 29 is moved to the hologram recording position. After the stop of the hologram media stage 29, in step S32 again, in order to confirm whether or not the hologram media stage 29 has accurately reached the hologram recording position, the CPU 1 sets the X-axis linear scale 32 and the Y-axis linear scale 33. The encoder pulse is read by the pulse counter 3.

  If there is again a difference between the stop position of the hologram media stage 29 and the hologram recording position, the CPU 1 outputs encoder pulses of the X-axis linear scale 32 and the Y-axis linear scale 33 in step S33. While checking, a pulse corresponding to the above-described difference amount is calculated, and a movement amount correction process is performed.

  Thereafter, the CPU 1 waits for a predetermined settling time in step S34, and after the settling time has elapsed, in step S35, the CPU 1 obtains reproduced image data again by the CCD linear sensor 28 and transfers the data to the memory in the CPU 1. .

  Next, in step S36, the hologram media stage 29 is moved from the recording position to the rear shift recording position calculated in step S25.

  In step S37, after the hologram media stage 29 is stopped, as in step S32, the CPU 1 checks whether or not the hologram media stage 29 has accurately reached the rear shift recording position and the X-axis linear scale 32 and The encoder pulse of the Y-axis linear scale 33 is read by the pulse counter 3.

  Here, as in step S33, if there is again a difference between the stop position of the hologram media stage 29 and the rear shift recording position, the CPU 1 in step S38, the X-axis linear scale 32 and the Y-axis While confirming the encoder pulse of the linear scale 33, a pulse corresponding to the above-described difference amount is calculated, and a movement amount correction process is performed.

  Thereafter, the CPU 1 waits for a predetermined settling time in step S39 as in step S33, and after the settling time has elapsed, in step S40, as in step S35, the CPU 1 again acquires reproduced image data by the CCD linear sensor 28. Then, the data is transferred to the memory in the CPU 1.

  As described above, the reproduction image data is read three times for one hologram.

  Next, in step S41, the CPU 1 confirms whether or not all hologram reproduction has been completed. If not completed, the process returns to step S25. If completed, step S42 is executed to start signal processing.

  In step S42, the CPU 1 reads out three reproduced image data corresponding to the hologram position from the memory, performs clock reproduction in units of data, and performs data sampling.

  In step S43, the CPU 1 develops an 8-bit gray scale value and appearance frequency graph on the memory of the CPU 1 using the sampling data, and calculates an S / N for each image data.

  In step S44, the CPU 1 obtains the best S / N data among the three data, and stores the data in the memory as data used for decoding.

  Thereafter, in step S45, the CPU 1 decodes the extracted good S / N data.

  Next, the pixel sizes of the CCD linear sensor 28 and the GLV 22 will be described.

  FIG. 4 is an explanatory diagram regarding the pixel sizes of the CCD linear sensor 28 and the GLV 22 in the hologram recording / reproducing apparatus of the present embodiment.

  The cell size of the CCD linear sensor 28 is 7 μm, and the pixel size of the GLV 22 is 25.5 μm. Therefore, in the hologram recording / reproducing apparatus of this embodiment, the oversampling is 2.64 (= 25.5 / 7) times. The output of the CCD linear sensor 28 is an 8-bit gray scale digital output. The line graph in the figure plots the output of each CCD cell with the cell number of the CCD linear sensor 28 on the horizontal axis and the gray scale value on the vertical axis (actually, quantized data obtained at intervals of 7 μm). As shown in FIG. 4, the hologram recording / reproducing apparatus of this embodiment demodulates the data pattern (1 and 0, that is, light and dark) of the GLV 22 from the hologram reproduction image data obtained from the CCD linear sensor 28.

  Next, signal processing in the hologram recording / reproducing apparatus of the present embodiment will be described.

  FIG. 5 is a schematic diagram of signal processing in the hologram recording / reproducing apparatus of this embodiment. Assuming that the hologram position recorded at the Nth time is reproduced, a hologram reproduction image is obtained by moving the hologram media stage 29 to a position shifted by a bias (an arbitrary distance) before and after the recording position. That is, three reproduced image data are obtained for one hologram position. Each of these three reproduced image data is equalized, a clock is reproduced for each data, data sampling is performed using this clock, S / N is calculated for each sampled data, and S / N is the best. Data is decoded and stored in memory.

  Next, the S / N calculation of the hologram will be described.

  S / N is quantified by the following equation.

  When using only the dark part (OFF) of dispersion,

により、

By

  When using only the bright part (ON) of dispersion,

により、Ｓ／Ｎを定量化することができる。

Thus, S / N can be quantified.

  FIG. 6 shows an example of a histogram of gray scale values. Here, the horizontal axis of the graph is the gray scale value, and the vertical axis is the appearance frequency for each gray scale. The point of the S / N pass / fail judgment is that the dark and bright peaks are clearly separated.

  Next, a first experimental result relating to crosstalk during hologram reproduction will be shown.

  FIG. 7 shows a first experimental result relating to crosstalk during hologram reproduction in the hologram recording / reproducing apparatus of the present embodiment. As shown in FIG. 7A, oscilloscope waveforms at the respective observation positions are shown in FIG. 7B, where the recording positions of two holograms with a pitch of 5 μm are a and c, and the intermediate position is b. ing. From this experimental result, it was confirmed that there is no influence of both hologram reproduction signals at the intermediate position (position 2.5 μm away from the hologram recording position).

  Next, a second experimental result regarding crosstalk during hologram reproduction will be shown.

  FIG. 8 shows a second experimental result regarding crosstalk during hologram reproduction in the hologram recording / reproducing apparatus of the present embodiment.

  As in FIG. 7, three holograms were recorded at 5 μm intervals. The hologram media stage 29 was operated in 1 μm steps from the first recorded hologram recording position (a), and the observed waveform of the oscilloscope was shown. From this experimental result, as shown in FIG. 7, it was confirmed that there was no crosstalk at the intermediate position (d) (i) of the recording pitch.

  From the above experimental results, if the distance from the 2.5 μm recording position is not obtained, a signal necessary for hologram reproduction cannot be obtained. Therefore, the bias amount (arbitrary distance) at each hologram recording position is within ± 1 to 1.5 μm of the recording position. I found that it should be set. In the present embodiment, three data are captured by shifting the same bias (arbitrary distance) before and after the hologram recording position. However, in the resolution of the hologram media stage 29, bias (arbitrary distance) is set. By further finely feeding the hologram media stage 29 within the range, it is possible to extract better data by increasing the number of data acquisition.

  According to the hologram recording / reproducing apparatus of the present embodiment described above, it is possible to obtain a highly reliable hologram reproducing signal without requiring complicated signal processing hardware. Even without using an expensive servo motor, the hologram media 24 is moved to a recording position and each position shifted from the recording position to the front and rear by an arbitrary distance with a simple positioning precision positioning stage using a linear scale. The cost of the mechanism can be reduced.

  In the above embodiment, the hologram optical system using the GLV which is a one-dimensional reflection type SLM (Spatial Light Modulator) is shown, but the present invention is not limited to this and is a two-dimensional reflection type. Alternatively, the present invention can be applied to a hologram optical system using a transmission type SLM.

  In the above embodiment, the case where the CCD linear sensor 28 is used has been described. However, the present invention can also be applied to a case using a CCD area sensor or a CMOS sensor.

  Furthermore, although the embodiment using the card-type hologram medium 24 has been shown, the present invention can also be applied to the case where the optical disk-type hologram medium 24 is used. In this case, instead of the X-axis linear scale 32 and the Y-axis linear scale 33 in the above-described embodiment, encoder pulses of a rotating mechanism system are used.

  In the above embodiment, the pulse counter 3 is provided with a plurality of comparison registers that can be freely rewritten by the CPU 1, and when a pulse is input, the number of input pulses is compared with the comparison register, and the input pulse is stored in the register. If the data matches, a signal may be output to the CPU 1.

  Furthermore, the pulse counter 3 is provided with a plurality of comparison registers that can be freely rewritten by the CPU 1, and when a pulse is input, the pulse counter 3 compares the number of input pulses with the comparison register, and the input pulse is stored in the register. If the data matches, a signal may be output to the CPU 1. In the comparison register of the pulse counter 3, by setting the values of the encoder pulse numbers of the X-axis linear scale 32 and the Y-axis linear scale 33, which are stored as recording position information in the memory, the hologram is reproduced during hologram reproduction. The hologram media stage 29 can be positioned without correcting the amount of movement of the media stage 29, and higher-speed hologram reproduction is possible.

  In addition, if the input pulse number coincidence signal of the pulse counter 3 is used as an image capture trigger of the CCD linear sensor 28, reproduction data can be obtained while operating the hologram medium 24. High-speed data capture is possible.

  In addition, an external storage device is connected to the hologram recording / reproducing apparatus of the above embodiment, and a high-speed image sensing device such as a CMOS sensor is employed as an image capturing device, and a large amount of data is acquired centering on one hologram recording position. Thus, it is possible to obtain a hologram reproduction signal with higher accuracy.

It is a block diagram which shows the structure of the hologram recording / reproducing apparatus concerning embodiment of this invention. It is a flowchart which shows the operation | movement of the hologram recording in the hologram recording / reproducing apparatus of this embodiment. It is a flowchart which shows the operation | movement of hologram reproduction in the hologram recording / reproducing apparatus of this embodiment. It is explanatory drawing regarding the pixel size of CCD linear sensor and GLV in the hologram recording / reproducing apparatus of this embodiment. It is the schematic of the signal processing in the hologram recording / reproducing apparatus of this embodiment. It is a graph which shows the example of the histogram of a gray scale value. It is a figure which shows the 1st experimental result regarding the crosstalk at the time of hologram reproduction | regeneration with the hologram recording / reproducing apparatus of this embodiment. It is a figure which shows the 2nd experimental result regarding the crosstalk at the time of hologram reproduction | regeneration with the hologram recording / reproducing apparatus of this embodiment.

Explanation of symbols

1 CPU
2 Analog image frame grabber 3 Pulse counter 4 Motor control circuit 5 Digital image frame grabber 6 LD power supply 7 LD
8 Isolator 9 Mechanical shutter 10 Half wave plate 11 Beam splitter 12 Wedge prism 13 Analog CCD camera 14a, 14b, 14c, 14d Mirror 15 Beam splitter 16 Diffuser plate 17 Compound lens 18 Signal light mechanical shutter 19 Beam expander 20 Mirror 21 Band pass Filter 22 GLV
23 Recording Lens 24 Hologram Media 25 Slit 26 Playback Lens 27 Cylindrical Lens 28 CCD Linear Sensor 29 Hologram Media Stage 30 X-axis Pulse Motor 31 Y-axis Pulse Motor 32 X-axis Linear Scale 33 Y-axis Linear Scale

Claims (12)

Medium moving means for moving the hologram recording medium along the recording surface;
During hologram reproduction, the hologram recording position of the hologram recording medium and the reproduction image data at each position shifted forward and backward from the hologram recording position by a certain distance are read across the movement of the hologram recording medium by the medium moving means. Reconstructed image reading means;
A hologram recording / reproducing apparatus comprising: signal processing means for selecting reproduced image data having the highest signal quality from the reproduced image data read by the reproduced image reading means and obtaining a reproduced signal. . Further comprising movement measurement means for detecting a movement of the hologram recording medium at a certain distance and generating a pulse;
2. The hologram recording according to claim 1, wherein the medium moving unit moves the hologram recording medium to a target recording position while correcting a moving amount using an output of the movement actual measuring unit during hologram recording. Playback device. Storage means for storing the number of output pulses of the movement actual measurement means until the hologram recording medium is moved to the target recording position at the time of hologram recording as recorded recording position information;
The medium moving means shifts the hologram recording medium by a predetermined distance forward and backward from the hologram recording position and from the hologram recording position based on information of a recorded recording position stored in the storage means at the time of hologram reproduction. The hologram recording / reproducing apparatus according to claim 2, wherein the hologram recording / reproducing apparatus is moved to each position.   4. The hologram recording / reproducing apparatus according to claim 3, further comprising reference position returning means for returning the hologram recording medium to a reference position before starting recording. The movement measurement means is a linear scale,
5. The hologram recording / reproducing apparatus according to claim 4, wherein the reference position returning means returns the hologram recording medium to a reference position using a Z-phase signal located at the center of the linear scale.   2. The hologram recording / reproducing apparatus according to claim 1, wherein the signal processing means calculates S / N for each reproduced image data at each position, and selects reproduced image data having the best S / N.   During hologram reproduction, the hologram recording position of the hologram recording medium and reproduction image data at each position shifted forward and backward from the hologram recording position are read out, respectively, and the highest signal quality is obtained from the read out reproduction image data. A hologram recording / reproducing method, comprising: selecting reproduced image data to obtain a reproduced signal There is provided movement measurement means for detecting a movement of the hologram recording medium at a certain distance and generating a pulse,
8. The hologram recording / reproducing method according to claim 7, wherein at the time of hologram recording, the hologram recording medium is moved to a target recording position while correcting a movement amount using an output of the movement actual measuring means. At the time of hologram recording, the number of output pulses of the movement actual measurement means until the hologram recording medium is moved to a recording position is stored as recorded recording position information,
When reproducing the hologram, the hologram recording medium is moved to the hologram recording position and each position shifted forward and backward from the hologram recording position by a predetermined distance based on the stored information of the recorded recording position. The hologram recording / reproducing method according to claim 8, wherein:   The hologram recording / reproducing method according to claim 9, wherein the hologram recording medium is returned to a reference position before starting recording. The movement measurement means is a linear scale,
The hologram recording / reproducing method according to claim 10, wherein the hologram recording medium is returned to a reference position by using a Z-phase signal located at the center of the linear scale.   9. The hologram recording / reproducing method according to claim 8, wherein S / N is calculated for each reproduced image data at each position, and reproduced image data having the best S / N is selected.

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