JP2007149264A - Optical information processor and verification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information processor capable of executing a verification processing in a short period of time without increasing device cost and circuit scale. <P>SOLUTION: The optical information processor for making information light 206 having image information about two-dimensionally arranged digital information interfere with reference light 205 and recording the pattern of the interference in a hologram disk 216 has a CMOS sensor 219 in which the information light 206 and reproduction light reproduced by emitting the reference light 205 to an area with the interference pattern recorded can be inputted and charge corresponding to input light is stored, and a verification processing part 10 for executing verification processing on the basis of information of first signal charge stored in the CMOS sensor 219 by the information light 206 and information of second signal charge stored in the CMOS sensor 219 by the reproduction light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and method for recording and reproducing information using holography, and more particularly to an apparatus and method for performing a confirmation operation (verification operation) as to whether or not information is accurately recorded on a recording medium.

  An optical information recording / reproducing apparatus that records and reproduces information using holography is known. In this optical information recording / reproducing apparatus, information is recorded by causing information light having image information to interfere with reference light and recording the interference fringes (interference pattern) on a recording medium. Further, information is read out by detecting reproduction light obtained by irradiating the reference light to the portion where the interference fringes are recorded. This type of optical information recording / reproducing apparatus has recently attracted particular attention because it can handle large volumes of data and can read data at high speed, and research for practical application has been actively conducted. Has been done.

  By the way, in a computer system that records information on a recording medium typified by a CD or DVD, normally, when information is recorded, a verify operation for confirming whether or not the information has been recorded accurately is performed. Is called. A similar verify operation is performed in an optical information recording / reproducing apparatus that records information using holography.

Patent Documents 1 and 2 disclose performing a verify operation simultaneously with information recording. In this verify operation, after recording information by irradiating information light and reference light onto the recording medium, the information light is stopped and the recording medium is irradiated with the reference light for a certain period. The reproduction light obtained by the irradiation of the reference light is detected by a sensor, and the read information obtained from the detection result is compared with the data (recording data) given at the time of recording, thereby collating the recorded information.
JP 11-311938 A Japanese Patent Laid-Open No. 2004-134048

  However, the conventional verify methods described in Patent Documents 1 and 2 require two verify memories, that is, a memory for storing recording data and a memory for storing read data. Cause serious problems.

  In an optical information processing apparatus using holography, unlike a normal system using a CD or DVD as a recording medium, information is recorded and reproduced in units of a two-dimensional image related to two-dimensionally arranged digital information (page data information). Is done. For this reason, the amount of information to be recorded at a time is larger than that of a normal system in which information is recorded or reproduced for each bit or sector. Since the amount of information to be recorded at a time is large as described above, the conventional verify method requires a large capacity memory as a verify memory, resulting in an increase in device cost and circuit scale.

  In addition, since it is necessary to acquire original data for comparison with read data from the memory in which the recording data is stored during the verify process, the verify process takes much time.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information processing apparatus that can solve the above-described problems and that can perform a verify process in a short time without increasing the apparatus cost and circuit scale.

  In order to achieve the above object, the present invention provides an optical information processing apparatus that causes information light having image information relating to two-dimensionally arranged digital information to interfere with reference light and records the interference pattern on a hologram recording medium. A photoelectric conversion unit (for example, a CMOS) that allows input of information light and reproduction light reproduced by irradiating the area where the interference pattern is recorded with the reference light and stores charges according to the input light. Sensor), information on the first signal charge accumulated in the photoelectric conversion unit by the information light, and information on the second signal charge accumulated in the photoelectric conversion unit by the reproduction light, A verification processing unit that determines whether or not the reproduced image information included in the reproduced light matches the image information.

  According to the above configuration, the image information corresponding to the recording data is obtained by irradiating the photoelectric conversion unit with the information light, so that a verification memory for storing the recording data is not necessary. Further, there is no need for processing for acquiring original data for comparison with read data from a memory storing recording data.

  According to the present invention, since a verification memory for storing recording data is not required, it is possible to provide an optical information processing apparatus with a smaller circuit scale at a lower cost than the conventional one.

  Further, since the process of reading the original data is not necessary because the comparison with the read data is performed from the verify memory, the time required for the verify process can be reduced accordingly.

Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing an optical system of an optical information recording / reproducing apparatus according to a first embodiment of the present invention. Referring to FIG. 1, this optical system is an optical system of a coaxial type holographic memory (collinear method), and includes a green laser 201 as a light source for recording and reproducing information. A collimator lens 202 and a mirror 203 are sequentially arranged in this order in the traveling direction of the laser light emitted from the green laser 201. The collimator lens 202 is for converting the light beam from the green laser 201 into a parallel light beam. The parallel light beam from the collimator lens 202 enters the mirror 203.

  A spatial light modulator (SLM) 204 is disposed in the traveling direction of the light beam reflected by the mirror 203. The spatial light modulation element 204 generates information light 206 and reference light 205 having page data information (image pattern) which is two-dimensionally arranged digital information, and is driven by a control unit (not shown). For example, a DMD (Deformable Mirror Device) is used as the spatial light modulator 204. DMD (Trademark of Texas Instruments, Inc.) is composed of a plurality of micromirrors arranged in a matrix, and generates spatial light having desired image information by controlling the angle of each micromirror. The reflected light (spatial light) from the DMD includes information light 206 and reference light 205. In the DMD, in the spot area where the reflected light from the mirror 203 is incident, the area near the center is used to generate the information light 206 and the surrounding area is used to generate the reference light 205. .

  A beam splitter 207, a relay lens 208, and a mirror 209 are sequentially arranged in this order in the traveling direction of the information beam 206 and the reference beam 205 generated by the spatial light modulator 204. The beam splitter 207 is composed of a cross prism having first and second reflecting surfaces. The first reflecting surface is configured to reflect a part of the information light 206 and the reference light 205 from the spatial light modulation element 204 and transmit the rest. The second reflecting surface is configured to transmit one of the first and second linearly polarized lights (P, S) and reflect the other linearly polarized light. The information beam 206 and the reference beam 205 that have passed through the beam splitter 207 are reflected by the mirror 209 after passing through the relay lens 208.

  An aperture member (aperture) 217, a lens 218, and a CMOS sensor 219 are sequentially arranged in this order in the traveling direction of the information light 206 and the reference light 205 reflected by the first reflecting surface of the beam splitter 207. The opening member 217 includes an opening that blocks the reference light 205 and allows only the information light 206 to pass therethrough. The information light 206 that has passed through the opening member 217 enters the CMOS sensor 219 via the lens 218. The output of the CMOS sensor 219 is supplied to the verify processing unit 10.

  A relay lens 210, a dichroic beam splitter 211, a quarter wave plate (QWP) 212, and a mirror 213 are sequentially arranged in this order in the traveling direction of the information light 206 and the reference light 205 reflected by the mirror 209. The dichroic beam splitter 211 has wavelength selectivity so as to transmit the information light 206 and the reference light 205 from the mirror 209. Both the information light 206 and the reference light 205 transmitted through the first and second reflecting films of the dichroic beam splitter 211 are linearly polarized light, and are circularly polarized (for example, clockwise circularly polarized light) by the quarter wavelength plate 212. Is converted to The information light 206 and the reference light 205 converted to circularly polarized light by the quarter wavelength plate 212 are reflected by the mirror 213.

  An objective lens 214 having a focal length F is arranged in the traveling direction of the information beam 206 and the reference beam 205 reflected by the mirror 213. The objective lens 214 condenses the information beam 206 and the reference beam 205 from the mirror 213 on a disc-shaped hologram disc 216 that is rotatably held on a spindle motor 215.

  The two relay lenses 208 and 210 form an intermediate image of an image pattern (page data information) generated on the spatial light modulator 204 at a position that is a focal distance F away from the objective lens 214. A so-called 4F optical system is configured in which the image pattern generation surface of the spatial light modulator 204, the objective lens 214, and the hologram disk 216 are spaced apart by the focal length F in the optical path in which the relay lenses 208 and 210 are inserted. Has been.

  The optical system shown in FIG. 1 further includes a red laser 220 as a servo light source used for focusing and tracking of the objective lens 214. A beam splitter 221, a lens 222, and a mirror 223 are sequentially arranged in this order in the traveling direction of the red laser beam (linearly polarized light) emitted from the red laser 220. The beam splitter 221 reflects a part of the red laser beam from the red laser 220 and transmits the rest. Instead of the beam splitter 221, a polarizing beam splitter that transmits one of the first and second linearly polarized light (P, S) and reflects the other linearly polarized light may be used. The red laser beam transmitted through the beam splitter 221 passes through the lens 222 and is reflected by the mirror 223.

  A dichroic beam splitter 211 is disposed in the traveling direction of the red laser beam reflected by the mirror 223. The dichroic beam splitter 211 has wavelength selectivity that reflects the red laser beam from the mirror 223. The red laser beam reflected by the dichroic beam splitter 211 enters the objective lens 214 via the quarter wavelength plate 212 and the mirror 213. In the quarter wavelength plate 212, the red laser beam (linearly polarized light) from the dichroic beam splitter 211 is converted into circularly polarized light (for example, clockwise circularly polarized light). The red laser beam converted to circularly polarized light by the quarter wavelength plate 212 is reflected by the mirror 213 and condensed on the hologram disk 216 by the objective lens 214.

  The hologram disk 216 is an optical information recording medium, and includes a first gap layer (dielectric layer), a wavelength selective reflection film, a second gap layer (dielectric layer), a recording layer (hologram layer) on a disk substrate. ), And a structure in which cover layers are sequentially laminated. The recording layer of the hologram disc 216 held on the spindle motor 215 is positioned at the focal length F of the objective lens 214. The wavelength selective reflection film has such characteristics that it reflects light (green laser light) that has arrived from the green laser 201 and transmits light (red laser light) that has arrived from the red laser 220. The red laser light transmitted through the wavelength selective reflection film passes through the first gap layer and is reflected by the surface of the disk substrate.

  The red laser light (reflected light) folded back on the surface of the disk substrate enters the condenser lens 214 again, and reaches the beam splitter 221 through the same optical path as the forward path. The beam splitter 221 reflects a part of the reflected light from the disk substrate. A photodetector 224 is arranged in the traveling direction of the reflected light from the disk substrate reflected by the beam splitter 221. The output of the photodetector 224 is supplied to a control unit (not shown) that controls driving of the spatial light modulator 204 and the spindle motor 215.

  On the other hand, the green laser light (reproduced light) reflected by the wavelength selective reflection film again enters the condenser lens 214 and reaches the beam splitter 207 through the same optical path as the forward path. For example, if the reflected light from the wavelength selective reflection film is in a clockwise circularly polarized state before being incident, the reflected state is in a counterclockwise circularly polarized state. Therefore, when the information light 206 and the reference light 205 from the spatial light modulation element 204 that have passed through the beam splitter 207 are the first linearly polarized light, the reproduction light that reaches the beam splitter 207 becomes the second linearly polarized light. Therefore, the reproduction light is reflected in the direction of the CMOS sensor 219 by the second reflecting film of the beam splitter 207.

  The CMOS sensor 219 functions as a reproduction light detection unit and also functions as a verification signal acquisition unit. The CMOS sensor 219 has a plurality of pixels arranged in a matrix. These pixels have a one-to-one correspondence with the pixels (micromirrors) used to generate the information light 206 of the spatial light modulation element 204, and receive light beams from the corresponding pixels (micromirrors).

  FIG. 2 shows the configuration of the CMOS sensor 219. Referring to FIG. 2, a plurality of signal lines φSEL, φRES, and φTX from the vertical scanning circuit 910 are wired so as to intersect with the vertical output line 906, and a pixel is formed in a region partitioned by these wirings. In the pixel, a photodiode 901 that functions as a photoelectric conversion element, a transfer switch 911, a reset switch 902, an amplification switch 903 that functions as a pixel amplifier, and a row selection switch 904 are provided. The gate of the transfer switch 911 is connected to the signal line ΦTX. The gate of the reset switch 902 is connected to the signal line ΦRES. The gate of the row selection switch 904 is connected to the signal line ΦSEL.

  During the period in which the photodiode 901 is irradiated with light, the transfer switch 911 is turned off, and charges are accumulated in the photodiode 901. During this accumulation period, the charge accumulated in the photodiode 901 is not transferred to the gate of the amplification switch 903. Before starting accumulation, the reset switch 902 is turned on, and the voltage at the gate of the amplification switch 903 is set to an appropriate voltage. This set voltage becomes a dark level.

  When the row selection switch 904 is turned on, the source follower circuit composed of the load current source 905 and the amplification switch 903 enters an operating state. When the transfer switch 911 is turned on in this state, the charge accumulated in the photodiode 901 is transferred to the gate of the amplification switch 903. As a result, the output of the selected row is generated on the vertical output line 906. This output is stored in the signal storage unit 907 via the transfer gates 909a and 909b.

  The output temporarily stored in the signal storage unit 907 is sequentially read out to the output unit V0 by the horizontal scanning circuit 908. In this way, two-dimensional image information is read from the CMOS sensor 219 to the external information reproducing unit or the like or the verification processing unit 10.

  Next, the operation of the optical system shown in FIG. 1 will be specifically described.

  First, the focusing and tracking operations of the objective lens 214 using the red laser light from the red laser 220 will be briefly described.

  A red laser beam (linearly polarized light) emitted from the red laser 220 passes through the beam splitter 221 and is converted into a parallel beam by the lens 222. The parallel light beam from the lens 222 is sequentially reflected by the mirror 223 and the dichroic beam splitter 211 and then reaches the quarter-wave plate 212. In the quarter wavelength plate 212, the parallel light beam from the dichroic beam splitter 211 is converted into circularly polarized light (for example, clockwise circularly polarized light). The parallel light beam (red laser light) converted into circularly polarized light by the quarter-wave plate 212 is reflected by the mirror 313 and then minutely applied to the surface (reflective surface) of the disk substrate on the hologram disk 216 by the objective lens 214. Focused as a light spot. The red laser light collected by the objective lens 214 reaches the surface of the disk substrate and is reflected there.

  The red laser light reflected on the surface of the disk substrate becomes circularly polarized light (for example, counterclockwise circularly polarized light) reverse to that before being reflected. The reflected light (red laser light) from the surface of the disk substrate is incident on the objective lens 214 again to be a parallel light beam. The parallel light flux from the objective lens 214 is reflected by the mirror 213 and passes through the quarter wavelength plate 212. The parallel light beam is converted by the quarter wavelength plate 212 into a linearly polarized light beam having a polarization plane perpendicular to the polarization plane of the parallel light beam in the forward path. The linearly polarized light beam that has passed through the quarter-wave plate 212 reaches the beam splitter 221 via the dichroic beam splitter 211, the mirror 223, and the lens 222, as in the forward path. In the beam splitter 221, a part of the linearly polarized light beam that has reached is reflected in the direction of the photodetector 224. The photodetector 224 has a plurality of light receiving surfaces, and detects position information of the reflecting surface of the disk substrate by a known method.

  Based on the detection result of the photodetector 224, a control unit (not shown) performs focusing and tracking of the objective lens 214. According to the focusing and tracking control, it is possible to detect the displacement of the hologram disc 216 with high accuracy using the surface of the disc substrate as a reference plane. Therefore, even if surface blurring or eccentricity occurs in the hologram disc 216, the recording spot can be dynamically followed by the recording surface of the hologram disc 216, and information can be recorded and reproduced on the recording layer with high accuracy. It can be carried out.

  Next, an operation for recording and reproducing information on the hologram disk 216 using the green laser 201 and a verify operation will be specifically described.

(1) Information recording:
When recording information on the hologram disc 216, first, the spatial light modulator 204 generates information light 206 and reference light 205 having page data information (image pattern) corresponding to information to be recorded (digital information). . In the spatial light modulation element 204, the incident light is reflected in the direction toward the hologram disk 216 in the pixel (micromirror) representing the information “1”. On the other hand, the incident light is not reflected in the direction of the hologram disk 216 in the pixel (micromirror) representing the information of “0”. In this way, information light 206 having page data information is generated.

  Information light 206 and reference light 205 generated by the spatial light modulation element 204 are incident on a beam splitter 207. In the beam splitter 207, a part of the information light 206 and the reference light 205 is reflected in the direction of the CMOS sensor 219 by the first reflection film, and the polarization direction of the transmitted light is aligned by the second reflection film. Here, it is assumed that the second reflective film transmits the first linearly polarized light and reflects the second linearly polarized light having a polarization plane perpendicular to the first linearly polarized light.

  The information light 206 and the reference light 205 (all of which are the first linearly polarized light) transmitted through the beam splitter 207 sequentially pass through the relay lens 208, the mirror 209, the relay lens 210, and the dichroic beam splitter 211, and then the quarter wavelength plate 212. To reach. In the quarter-wave plate 212, the incident information light 206 and reference light 205 are converted into clockwise circularly polarized light. The information light 206 and the reference light 205 converted to circularly polarized light by the quarter wavelength plate 212 are reflected by the mirror 213 and condensed on the hologram disk 216 by the objective lens 214.

  The information light 206 and the reference light 205 collected by the objective lens 214 interfere, and the interference fringes are recorded on the recording layer of the hologram disk 216 as a refractive index distribution. By recording the interference fringes in the recording layer as a refractive index distribution in this way, a digital volume hologram is formed.

(2) Verify processing:
(2-1) Signal charge accumulation:
During the signal charge accumulation period, in the CMOS sensor 219, the transfer switch 911 is turned off in each pixel, and the signal charge is accumulated in the photodiode 901 in the following procedure.

  In the operation of “(1) Information recording”, the beam splitter 207 reflects a part of the information light 206 and the reference light 205 generated by the spatial light modulation element 204 in the direction of the CMOS sensor 219. Of the information light 206 and the reference light 205 reflected by the beam splitter 207, the reference light 205 is blocked by the aperture member 217, and only the information light 206 enters the light receiving surface of the CMOS sensor 219 via the lens 218. The lens 218 forms an image of the image pattern (information light 206) generated on the spatial light modulator 204 on the light receiving surface of the CMOS sensor 219. In the CMOS sensor 219, the first signal charge corresponding to the incident information light 206 is generated by the photodiode 901 in the pixel to which the information light 206 is incident.

  When the first signal charge is accumulated in the photodiode 901, subsequently, only the reference light 205 is generated in the spatial light modulation element 204. Specifically, information “1” is displayed only in a region where the reference light 205 on the spatial light modulator 204 is modulated, and information “0” is displayed in all regions where the information light 206 is modulated. By doing so, only the reference light 205 is generated in the spatial light modulation element 204.

  The reference light 205 generated by the spatial light modulation element 204 is incident on the beam splitter 207. In the beam splitter 207, a part of the reference light 205 is reflected in the direction of the CMOS sensor 219 by the first reflection film, and the polarization direction of the transmitted light is aligned by the second reflection film. Since the reference light 205 reflected by the first reflective film is blocked by the opening member 217, it does not reach the CMOS sensor 219.

  The reference light 205 (first linearly polarized light) transmitted through the beam splitter 207 sequentially passes through the relay lens 208, the mirror 209, the relay lens 210, and the dichroic beam splitter 211, and reaches the quarter wavelength plate 212. In the quarter-wave plate 212, the incident reference light 205 is converted into clockwise circularly polarized light. The reference light 205 converted into circularly polarized light by the quarter wavelength plate 212 is reflected by the mirror 213 and condensed on the hologram disk 216 by the objective lens 214.

  When the reference light 205 collected by the objective lens 214 is applied to the area of the recording layer of the hologram disk 216 where the interference fringes are recorded by the operation of “(1) Information recording”, the reference light 205 is applied to the information light 206. Reproduced light including the included page data information is generated. The reproduction light is reflected by the wavelength selective reflection film below the recording layer of the hologram disk 216, becomes counterclockwise circularly polarized light, enters the objective lens 214, and becomes a parallel light beam. The reproduction light that has become a parallel light beam is reflected by the mirror 213 and passes through the quarter-wave plate 212. The quarter-wave plate 212 converts the reproduction light into second linearly polarized light having a polarization plane perpendicular to the polarization plane of the parallel light flux in the forward path. At this time, an intermediate image of the reproduced image pattern is formed at a focal length F from the objective lens 214.

  The reproduction light that has passed through the quarter-wave plate 212 reaches the beam splitter 207 via the dichroic beam splitter 211, the relay lens 210, the mirror 209, and the relay lens 208 in this order. In the beam splitter 207, the reproduction light is reflected in the direction of the CMOS sensor 219 by the second reflection film. The reproduction light reflected by the beam splitter 207 passes through the aperture member 217 and is condensed on the light receiving surface of the CMOS sensor 219 by the lens 218. At this time, the intermediate image of the reproduced image pattern is re-imaged by the relay lenses 208 and 210 at a position conjugate with the spatial light modulation element 204. An opening member 217 is disposed at this position, and unnecessary light (such as reference light) located around the information light is shielded. The lens 218 forms the re-imaged intermediate image on the light receiving surface of the CMOS sensor 219. The intermediate image of the image pattern based on the reproduction light corresponds to the image of the image pattern (information light 206) generated on the spatial light modulation element 204. In the CMOS sensor 219, the second signal charge corresponding to the incident reproduction light is generated and accumulated by the photodiode 901 in the pixel where the reproduction light is incident.

(2-2) Reading of signal charge:
As described above, when the first signal charge corresponding to the information light 206 and the second signal charge corresponding to the reproduction light are accumulated in the photodiode 901, the row selection switch 904 is turned on in the CMOS sensor 219. It is said. When the row selection switch 904 is turned on, the source follower circuit including the load current source 905 and the amplification switch 903 is activated. In this state, the transfer switch 911 is turned on. When the transfer switch 911 is turned on, the signal charge accumulated in the photodiode 901 (charge obtained by adding the second signal charge to the first signal charge) is transferred to the gate of the amplification switch 903. As a result, the output of the selected row is generated on the vertical output line 906. This output is stored in the signal storage unit 907 via the transfer gates 909a and 909b. The selected row output signal accumulated in the signal accumulation unit 907 is sequentially read out to the output unit V0 by the horizontal scanning circuit 908. The output signal (two-dimensional image information) read out in this way is supplied to the verify processing unit 10 as an output signal of the CMOS sensor 219.

  The verify processing unit 10 compares the level of the output signal of the CMOS sensor 219 with the reference level, and information is accurately recorded on the hologram disk 216 in the “(1) information recording” operation based on the comparison result. It is determined whether or not (Verify processing). The principle of this determination will be specifically described below.

  When the information is recorded accurately, the image information included in the reproduction light matches the image information included in the information light 206. Therefore, the pixel receiving the information light 206 and the pixel receiving the reproduction light are always Will match. For this reason, in all the light receiving pixels, the photodiode 901 always stores a charge obtained by adding the second signal charge to the first signal charge. In this case, all the levels of the output signals from the light receiving pixels are levels corresponding to the charge obtained by adding the second signal charge to the first signal charge.

  On the other hand, when the information is not accurately recorded, the image information included in the reproduction light is partly different from the image information included in the information light 206. For this reason, the pixel that has received the information light 206 and the pixel that has received the reproduction light do not completely match, and only one of the information light 206 and the reproduction light is received by some pixels. In this case, the level of the output signal from the pixel receiving the information light 206 and the reproduction light is a level corresponding to the charge obtained by adding the second signal charge to the first signal charge. However, the level of the output signal from the pixel that receives one of the information light 206 and the reproduction light is a level corresponding to the first or second signal charge.

  The reference level L is set between a level L1 corresponding to the first or second signal charge and a level L2 corresponding to a charge obtained by adding the second signal charge to the first signal charge. When the level of the output signal of the CMOS sensor 219 is higher than the dark level and lower than the reference level L, it is an output signal from a pixel that has received one of the information light 206 and the reproduction light, and thus information is accurately recorded. It can be judged that there is not. When the level of the output signal of the CMOS sensor 219 is equal to or higher than the reference level L, it can be determined that the information is accurately recorded because it is an output signal from the pixel that has received the information light 206 and the reproduction light.

  According to the above-described verify processing, it is not necessary to separately store the two-dimensional image information at the time of recording in the memory, so that the scale of the data processing circuit can be reduced.

  In the above verify process, the output signal (analog) of the CMOS sensor 219 is compared with a reference level, but a digital signal obtained by AD converting the output signal of the CMOS sensor 219 is used as a reference value (corresponding to the reference level). You may compare.

(3) Information reproduction:
When reproducing information recorded on the hologram disk 216, only the reference light 205 is generated in the spatial light modulation element 204. Then, similarly to the generation of the reproduction light in the above “(2) verification process”, the generated reference light 205 is irradiated to the area where the interference fringes are recorded by the operation of “(1) information recording”. And the reproduction light is detected by the CMOS sensor 219. In the CMOS sensor 219, signal charges corresponding to the incident reproduction light are generated and accumulated by the photodiode 901 in the pixel where the reproduction light is incident.

  When signal charges corresponding to the reproduction light are accumulated in the photodiode 901, the row selection switch 904 is turned on in the CMOS sensor 219. When the row selection switch 904 is turned on, the source follower circuit including the load current source 905 and the amplification switch 903 is activated. In this state, the transfer switch 911 is turned on. When the transfer switch 911 is turned on, the signal charge accumulated in the photodiode 901 is transferred to the gate of the amplification switch 903. As a result, the output of the selected row is generated on the vertical output line 906. This output is stored in the signal storage unit 907 via the transfer gates 909a and 909b. The selected row output signal accumulated in the signal accumulation unit 907 is sequentially read out to the output unit V0 by the horizontal scanning circuit 908. The output signal (two-dimensional image information) read out in this way is supplied to the verification processing unit 10 as an output signal of the CMOS sensor 219.

According to the reproduction of the information described above, unnecessary light such as reference light is blocked by the aperture member 217 and does not enter the CMOS sensor 219, so that a reproduction signal with good S / N can be obtained.
(Second Embodiment)
The optical system of the optical information recording / reproducing apparatus of this embodiment is the same as the optical system shown in FIG. 1 except that the configuration of the CMOS sensor and the verification processing by the verification processing unit are different.

  FIG. 3 shows the configuration of a CMOS sensor used in the optical system of the optical information recording / reproducing apparatus of this embodiment. Referring to FIG. 3, the CMOS sensor includes a pixel region 300, a frame memory 301, vertical shift registers 302 and 303, and a horizontal shift register 304.

  The pixel region 300 is a region where pixels having the photodiode 901 illustrated in FIG. 2 are arranged in a matrix. The configuration of each pixel in the pixel region 300 is the same as that shown in FIG. 2, and is arranged corresponding to each of the two-dimensionally arranged digital information (image information). The vertical shift register 302 is for selectively transferring the signal charge accumulated in the photodiode of each pixel in the pixel region 300. The vertical shift register 302 selects pixels in the row direction.

  The frame memory 301 is arranged corresponding to each pixel in the pixel region 300 and includes a plurality of memories to which charges accumulated in the photodiode are transferred. The vertical shift register 303 is for selectively transferring a signal held in the frame memory 301. The vertical shift register 303 selects a memory in the row direction. The horizontal shift register 304 selects the output of the row selected by the vertical shift registers 301 and 302.

  The information recording and reproducing operations are the same as those in the first embodiment described above, but the verify process is different from that in the first embodiment. In the first embodiment, the first signal charge corresponding to the information light is accumulated in the photodiode, and further the second signal charge corresponding to the reproduction light is accumulated. In contrast, in the present embodiment, after the first signal charge corresponding to the information light is accumulated in the photodiode, the first signal based on the accumulated signal charge is transferred to the frame memory 301 and held. Thereafter, the second signal charge corresponding to the reproduction light is accumulated in the photodiode. Then, the verify processing unit 10 compares the first signal held in the frame memory with the second signal based on the second signal charge accumulated in the photodiode, and based on the comparison result, the hologram disk 216 is compared. It is determined whether or not the information has been recorded correctly.

  When the information is recorded accurately, the image information included in the reproduction light matches the image information included in the information light, so the pixels receiving the information light and the pixels receiving the reproduction light always match. It will be. Therefore, the first signal matches the second signal for all light receiving pixels. The verify processing unit 10 determines that information is accurately recorded when the first signal and the second signal match for all pixels.

On the other hand, when the information is not accurately recorded, the image information included in the reproduction light is partially different from the image information included in the information light. For this reason, the pixel that has received the information light and the pixel that has received the reproduction light do not completely match, and only one of the information light and the reproduction light is received by some pixels. In this case, the first signal matches the second signal for the pixels that have received the information light and the reproduction light, but the first signal for the pixels that have received either the information light or the reproduction light has the first signal. The signal does not match the second signal. The verify processing unit 10 determines that information is not accurately recorded when a pixel in which the first signal and the second signal do not match is detected.
(Third embodiment)
The optical system of the optical information recording / reproducing apparatus of this embodiment is the same as the optical system shown in FIG. 1 except that the driving method of the CMOS sensor and the verification processing by the verification processing unit are different. The configuration of the CMOS sensor is the same as that described in FIG.

  The information recording and reproducing operations are the same as those in the first embodiment described above, but the verify process is different from that in the first embodiment. In the first embodiment, the first signal charge corresponding to the information light is accumulated in the photodiode, and further the second signal charge corresponding to the reproduction light is accumulated. In contrast, in the present embodiment, FD (Floating Diffusion) is used to hold the first signal charge corresponding to the information light accumulated in the photodiode by the FD. Thereafter, the second signal charge corresponding to the reproduction light is accumulated in the photodiode. Then, the verify processing unit 10 obtains a differential between the signal based on the first signal charge accumulated in the FD and the signal based on the second signal charge accumulated in the photodiode. Here, FD is a small-capacitance capacitor formed at a portion serving as an output destination of the transfer switch of each pixel (pixels arranged in a matrix having the photodiode 901 shown in FIG. 2).

  4A to 4I conceptually show potential state transitions of the photodiode 401, the transfer switch 402, and the FD region 403 in the verify operation using the FD. Here, the photodiode 401 and the transfer switch 402 correspond to the photodiode 901 and the transfer switch 911 shown in FIG. 2, respectively.

  In the verify process, when information light is irradiated to the CMOS sensor, signal charges are accumulated in the photodiode 401. The state where the signal charges are accumulated is the state shown in FIG. Next, when the transfer switch 402 is turned on, the signal charge accumulated in the photodiode 401 is transferred to the FD region 403 as shown in FIG. Thereafter, as shown in FIG. 4C, the transfer switch 402 is turned off.

  Next, when the reproduction light is irradiated to the CMOS sensor, charges are accumulated in the photodiode 401 as shown in FIG. After the signal charge due to the reproduction light is accumulated in the photodiode, a pixel is selected by a selection switch (corresponding to the selection switch 904 shown in FIG. 2), and the first charge corresponding to the accumulated charge in the FD region 403 is selected. The signal is read (see FIG. 4E). Then, the read first signal is stored in a first capacitor (not shown). This first signal corresponds to the signal generated by the information light, and becomes the original data for comparison when performing the verification. As the first capacitor, a capacitor provided for each column for holding a noise signal used in a normal CMOS sensor can be used.

  Next, in FIG. 4F, the charge in the FD region 403 is discharged to the power supply Vdd via a reset switch (not shown). When the transfer switch 402 is turned on after discharging the charge, the charge stored in the photodiode 401 is transferred to the FD region 403 as shown in FIG. Then, a pixel is selected by a selection switch (not shown), and a second signal corresponding to the accumulated charge in the FD region 403 is read out to the second capacitor (see FIG. 4H). As the second capacitor, a capacitor provided for each column for holding an image signal including a noise signal used in a normal CMOS sensor can be used. Thereafter, in FIG. 4I, the charge in the FD region 403 is discharged to the power supply Vdd via a reset switch (not shown).

  After the charge is discharged, the difference between the first signal accumulated in the first capacitor (see FIG. 4E) and the second signal accumulated in the second capacitor (see FIG. 4H) by the verification processing unit. By determining the movement, it is determined whether or not information is correctly recorded on the hologram disk.

  When the information is recorded accurately, the image information included in the reproduction light matches the image information included in the information light, so the pixels receiving the information light and the pixels receiving the reproduction light always match. It will be. Therefore, the first signal matches the second signal for all light receiving pixels. The verify processing unit determines that the information is accurately recorded when the first signal and the second signal match for all pixels.

  On the other hand, when the information is not accurately recorded, the image information included in the reproduction light is partially different from the image information included in the information light. For this reason, the pixel that has received the information light and the pixel that has received the reproduction light do not completely match, and only one of the information light and the reproduction light is received by some pixels. In this case, the first signal matches the second signal for the pixels that have received the information light and the reproduction light, but the first signal for the pixels that have received either the information light or the reproduction light has the first signal. The signal does not match the second signal. The verify processing unit determines that information is not accurately recorded when a pixel in which the first signal and the second signal do not match is detected.

  The apparatus of each embodiment described above is an example of the present invention, and the configuration and operation thereof can be changed as appropriate without departing from the spirit of the present invention. For example, in each embodiment, a CMOS sensor is used, but an image sensor using a CCD may be used instead.

  Further, although an optical system of a coaxial type holographic memory (collinear method) is used as an optical system, other optical systems can be used. For example, an optical system may be used in which the light beam from the green laser is divided into two light beams and one is used as information light and the other is used as reference light.

  In addition, by providing a non-polarized BS in the optical path, the information light before recording is guided to the CMOS sensor, but the present invention is not limited to this. Any structure may be used as long as it can directly irradiate the CMOS sensor with the information light at the time of recording instead of the reproduction light according to the recording information of the recording medium.

  Moreover, it is good also as a structure which combined suitably each structure of the 1st-3rd embodiment mentioned above.

  The optical information processing apparatus of the present invention can be applied to both a recording apparatus that records information using holography and a recording / reproducing apparatus that records and reproduces information using holography.

It is a block diagram which shows the optical system of the optical information recording / reproducing apparatus which is the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the CMOS sensor shown in FIG. It is a schematic diagram which shows the structure of the CMOS sensor used for the optical system of the optical information recording / reproducing apparatus which is the 2nd Embodiment of this invention. (A) to (i) conceptually show potential state transitions of the photodiode, the transfer switch, and the FD region in the verify operation performed in the optical information recording / reproducing apparatus according to the third embodiment of the present invention. It is a schematic diagram shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Verify processing part 201 Green laser 202 Collimator 203, 209, 213, 223 Mirror 204 Light spatial modulation element (SLM)
205 Reference Light 206 Information Light 207 Beam Splitter 208, 210 Relay Lens 211 Dichroic Beam Splitter 212 1/4 Wave Plate (QWP)
214 Objective lens 215 Spindle motor 216 Hologram disk 217 Opening member 218, 222 Lens 219 CMOS sensor 220 Red laser 221 Beam splitter 224 Photo detector

Claims (8)

In an optical information processing apparatus for causing information light having image information relating to two-dimensionally arranged digital information to interfere with reference light and recording the interference pattern on a hologram recording medium,
A photoelectric conversion unit capable of inputting the information light and the reproduction light reproduced by irradiating the area where the interference pattern is recorded with the reference light, and storing a charge corresponding to the input light;
Included in the reproduction light based on the information on the first signal charge accumulated in the photoelectric conversion unit by the information light and the information on the second signal charge accumulated in the photoelectric conversion unit by the reproduction light An optical information processing apparatus comprising: a verification processing unit that determines whether or not reproduced image information matches the image information. The photoelectric conversion unit has a plurality of pixels including photodiodes arranged corresponding to each of the two-dimensionally arranged digital information,
The verify processing unit is larger than a signal level corresponding to a larger one of the first and second signal charges, and corresponds to a charge obtained by adding the second signal charge to the first signal charge. The reference level smaller than the signal level is preset, and when the signal level corresponding to the charge accumulated in the photodiode is lower than the reference level, it is determined that the reproduced image information is different from the image information. Item 4. The optical information processing apparatus according to Item 1. The photoelectric conversion unit is arranged corresponding to each of the two-dimensionally arranged digital information, a plurality of pixels including photodiodes, and a plurality of pixels arranged corresponding to these pixels and stored in the photodiodes. A frame memory composed of a plurality of memories to which one signal charge is transferred,
The verify processing unit compares the first information based on the first signal charge stored in the frame memory and the second information based on the second signal charge stored in the photodiodes of the plurality of pixels. The optical information processing apparatus according to claim 1, wherein when the first information and the second information are different, the reproduction image information is determined to be different from the image information. The photoelectric conversion unit is arranged corresponding to each of the two-dimensionally arranged digital information, a plurality of pixels including photodiodes, and stored in the photodiodes provided corresponding to the pixels. A plurality of floating diffusion regions to which the first signal charge is transferred,
The verification processing unit includes first information based on first signal charges stored in the plurality of floating diffusion regions and second information based on second signal charges stored in photodiodes of the plurality of pixels. The optical information processing apparatus according to claim 1, wherein when the first and second information are different, the reproduction image information is determined to be different from the image information. A verification method performed in an apparatus for causing information light having image information relating to two-dimensionally arranged digital information to interfere with reference light and recording the interference pattern on a hologram recording medium,
A first step of irradiating the photoelectric conversion unit with the information light to accumulate a first signal charge;
A second step of irradiating the reference light with an area where the interference pattern is recorded to generate reproduction light, irradiating the generated reproduction light to the photoelectric conversion unit, and accumulating a second signal charge;
Included in the reproduction light based on the information of the first signal charge accumulated in the photoelectric conversion unit by the information light and the information of the second signal charge accumulated in the photoelectric conversion unit by the reproduction light And a third step of determining whether or not reproduced image information to be matched with the image information. The first step is a step of irradiating the information light to a plurality of pixels including photodiodes arranged corresponding to each of the two-dimensionally arranged digital information,
The second step is a step of irradiating the plurality of pixels with the reproduction light in a state where the first signal charge is accumulated in the photodiode.
The third step is greater than a signal level corresponding to the larger one of the first and second signal charges, and corresponds to a charge obtained by adding the second signal charge to the first signal charge. The method of claim 5, further comprising the step of determining that the reproduced image information is different from the image information when a signal level corresponding to the charge accumulated in the photodiode is lower than a reference level smaller than a reference level. The verification method described. The first step includes
Irradiating the information light to a plurality of pixels including photodiodes arranged corresponding to each of the two-dimensionally arranged digital information;
Transferring a first signal charge accumulated in the photodiode to a frame memory consisting of a plurality of memories arranged corresponding to the plurality of pixels,
The second step is a step of irradiating the plurality of pixels with the reproduction light after the first signal charge is transferred to the frame memory.
In the third step, the first information based on the first signal charges stored in the frame memory and the second information based on the second signal charges stored in the photodiodes of the plurality of pixels are stored. 6. The verification method according to claim 5, further comprising a step of comparing and determining that the reproduced image information is different from the image information when the first and second information are different. The first step includes
Irradiating the information light to a plurality of pixels including photodiodes arranged corresponding to each of the two-dimensionally arranged digital information;
Transferring the first signal charge accumulated in the photodiode to a charge accumulation region comprising a plurality of floating diffusion regions provided corresponding to the plurality of pixels,
The second step is a step of irradiating the plurality of pixels with the reproduction light after the first signal charge is transferred to the charge storage region,
The first information based on the first signal charge accumulated in the charge accumulation region is compared with the second information based on the second signal charge accumulated in the photodiodes of the plurality of pixels, and the first information is compared. The verification method according to claim 5, further comprising: determining that the reproduced image information is different from the image information when the second information is different from the second information.

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