JP2018101450A - Optical information reproducing device and optical information reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording and reproducing device and a method thereof capable of generating a control signal with good signal quality even if light quantity of a reproduction signal fluctuates in a holographic memory.SOLUTION: The optical information reproducing device reproducing information recorded by using a holography from an optical information recording medium comprises a laser source generating reference light, an optical axis branch part branching the reference light to a plurality of reference light beams having different angles, an angle adjustment part adjusting angles which the plurality of branched reference light beams are incident on the optical information recording medium, a light detection part irradiating the optical information recording medium with the plurality of branched reference light beams and having a plurality of light receiving surfaces detecting a plurality of reproduced diffraction light beams, a signal adjustment part adjusting each signal ratio of a plurality of signals detected at the light detection part, and a control signal calculation part generating a control signal on the basis of a signal output by the signal adjustment part. An angle coordination part controls an angle which the reference light is incident on the optical information recording medium by the angle adjustment part on the basis of the control signal output from the control signal calculation part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus and method for reproducing information using holography.

  As a technique for suppressing an offset in a reproduction signal in a holographic memory, for example, there is JP-A-8-138270 (Patent Document 1). In this publication, “object: an optical head with improved quality is supplied by removing an imbalance of light amounts incident on a plurality of photodetectors. Also, an optical head with improved assemblability is provided. In a unit in which a semiconductor laser light source, a photodetector, and an analyzer are mounted in the same package, the analyzer is adjusted and mounted with respect to the semiconductor laser light. It is possible to suppress the decrease in the amplitude of the magneto-optical signal, the increase in noise across the groove of the optical recording medium, the increase in various initial signal offsets, etc. Also, the assembly of the optical head is improved. It has an effect to make it ".

JP-A-8-138270

  Currently, the Blu-ray Disc (TM) standard using a blue-violet semiconductor laser enables commercialization of an optical disc having a recording density of about 100 GB even for consumer use. In the future, it is desired to increase the capacity of optical disks exceeding 500 GB. However, in order to realize such a high density with an optical disc, a high density technology by a new method different from the conventional high density technology by shortening the wavelength and increasing the NA of the objective lens is necessary.

  In many optical components, the efficiency such as transmittance or reflectance generally changes depending on the incident angle and polarization of light. Therefore, in the optical information recording / reproducing apparatus using holography, there is a problem that the amount of the reproduction signal varies depending on the angle or polarization of the reference light, and the quality of various control signals may be lowered.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical information recording / reproducing apparatus and method capable of generating a control signal with good signal quality even when the light amount of the reproduced signal fluctuates. To do.

  The above problem is solved by, for example, the configuration described below.

  In an optical information reproducing apparatus for reproducing information recorded using holography from an optical information recording medium, a laser light source for generating reference light and an optical axis branching unit for branching the reference light into a plurality of reference lights having different angles An angle adjusting unit that adjusts an angle at which the plurality of branched reference lights are incident on the optical information recording medium, and a plurality of reproduced information by irradiating the optical information recording medium with the plurality of branched reference lights. A light detection unit having a plurality of light receiving surfaces for detecting the diffracted light, a signal adjustment unit for adjusting signal ratios of the plurality of signals detected by the light detection unit, and a signal output by the signal adjustment unit A control signal calculation unit that generates a control signal, and the angle adjustment unit causes the reference light to be incident on the optical information recording medium by the angle adjustment unit based on a control signal output from the control signal calculation unit. The angle To your.

  According to the present invention, it is possible to provide an optical information recording / reproducing apparatus and method capable of generating a control signal having a good signal quality even when the light amount of the reproduced signal varies in the holographic memory.

Schematic showing the optical information recording / reproducing apparatus in a present Example Schematic showing the optical pickup in the present embodiment Schematic showing the optical pickup in the present embodiment Schematic showing the example of an operation | movement flow until the preparation of recording or reproduction | regeneration in the optical information recording / reproducing apparatus of a present Example is completed. Example of operation flow of recording process in optical information recording / reproducing apparatus of embodiment Example of operation flow of reproduction processing in optical information recording / reproducing apparatus of this embodiment Schematic showing the signal generation circuit in the optical information recording / reproducing apparatus in a present Example Schematic showing the signal processing circuit in the optical information recording / reproducing apparatus in a present Example Example of operation flow of signal generation circuit in this embodiment Example of operation flow of signal processing circuit in this embodiment Schematic showing an example of a control signal in the present embodiment Schematic showing the example of the characteristic of the transmittance | permeability of the reference light in a present Example Schematic representing an example of signal strength in the case of the transmittance characteristic of FIG. 9a Schematic showing the example of the fluctuation | variation of the control signal in the optical information recording / reproducing apparatus of a present Example Schematic showing an example of signal ratio adjustment in the optical information recording / reproducing apparatus of the present embodiment Schematic showing an example of signal ratio adjustment in the optical information recording / reproducing apparatus of the present embodiment Example of operation flow of signal ratio adjustment in optical information recording / reproducing apparatus of this embodiment Schematic showing an example of signal intensity in signal ratio adjustment of the present embodiment Example of operation flow of signal ratio adjustment in optical information recording / reproducing apparatus of this embodiment Example of operation flow of signal ratio adjustment in optical information recording / reproducing apparatus of this embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing an optical information recording / reproducing apparatus that records and / or reproduces digital information using holography.

  The optical information recording / reproducing device 10 is connected to an external control device 91 via an input / output control circuit 90. In the case of recording, the optical information recording / reproducing apparatus 10 receives the information signal to be recorded from the external control device 91 by the input / output control circuit 90. When reproducing, the optical information recording / reproducing apparatus 10 transmits the reproduced information signal to the external control apparatus 91 by the input / output control circuit 90.

  The optical information recording / reproducing apparatus 10 includes a pickup 11, a reproduction reference light optical system 12, a cure optical system 13, a disk rotation angle detection optical system 14, and a rotation motor 50. The optical information recording medium 1 is a rotation motor. 50 can be rotated.

  The pickup 11 plays a role of emitting reference light and signal light to the optical information recording medium 1 and recording digital information on the recording medium using holography. At this time, the signal to be recorded is sent to the spatial light modulator in the pickup 11 by the controller 89 via the signal generation circuit 86, and the signal light is modulated by the spatial light modulator.

  When reproducing the information recorded on the optical information recording medium 1, the reproduction reference light optical system 12 generates a light wave that causes the reference light emitted from the pickup 11 to enter the optical information recording medium in a direction opposite to that during recording. Generate. The reproduction light reproduced by the reproduction reference light is detected by the photodetector in the pickup 11, and the signal is reproduced by the signal processing circuit 85.

  The irradiation time of the reference light and the signal light applied to the optical information recording medium 1 can be adjusted by controlling the opening / closing time of the shutter in the pickup 11 via the shutter control circuit 87 by the controller 89.

  The cure optical system 13 plays a role of generating a light beam used for pre-cure and post-cure of the optical information recording medium 1. Precure is a pre-process for irradiating a predetermined light beam in advance before irradiating the desired position with reference light and signal light when recording information at a desired position in the optical information recording medium 1. Post-cure is a post-process for irradiating a predetermined light beam after recording information at a desired position in the optical information recording medium 1 so that additional recording cannot be performed at the desired position.

  The disk rotation angle detection optical system 14 is used to detect the rotation angle of the optical information recording medium 1. When adjusting the optical information recording medium 1 to a predetermined rotation angle, a signal corresponding to the rotation angle is detected by the disk rotation angle detection optical system 14, and a disk rotation motor control circuit is detected by the controller 89 using the detected signal. The rotation angle of the optical information recording medium 1 can be controlled via 88.

  A predetermined light source driving current is supplied from the light source driving circuit 82 to the light sources in the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14, and each light source emits a light beam with a predetermined light amount. Can do.

  Further, the pickup 11 and the disc cure optical system 13 are provided with a mechanism capable of sliding the position in the radial direction of the optical information recording medium 1, and position control is performed via the access control circuit 81.

  By the way, the recording technique using the principle of angle multiplexing of holography tends to have a very small tolerance for the deviation of the reference beam angle.

  Accordingly, a mechanism for detecting the deviation amount of the reference beam angle is provided in the pickup 11, a signal for servo control is generated by the control signal generation circuit 83, and the deviation amount is corrected via the servo control circuit 84. It is necessary to provide a servo mechanism for this purpose in the optical information recording / reproducing apparatus 10. Here, since the efficiency of the transmittance or reflectance of the optical component may differ depending on the reference light angle and polarization, the signal adjustment circuit 92 adjusts the fluctuation of the light amount of the reproduction signal. This adjustment will be described in detail later with reference to FIG. The signal adjustment circuit 92 includes, for example, a memory, stores an adjustment amount obtained in advance before data reproduction, and adjusts the signal with reference to the adjustment amount at the time of data reproduction.

  Further, the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14 may be simplified by combining several optical system configurations or all optical system configurations.

  FIG. 2 shows a recording principle in an example of a basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. The light beam emitted from the light source 301 passes through the collimator lens 302 and enters the shutter 303. When the shutter 303 is open, after the light beam passes through the shutter 303, the optical element 304 composed of, for example, a half-wave plate or the like causes the light quantity ratio or the light quantity difference between p-polarized light and s-polarized light to be a desired ratio. After the polarization direction is controlled so as to become, it enters a PBS (Polarization Beam Splitter) prism 305.

  The light beam that has passed through the PBS prism 305 functions as signal light 306, and after the light beam diameter is expanded by the beam expander 308, the light beam passes through the phase mask 309, the relay lens 310, and the PBS prism 311 and passes through the spatial light modulator 312. Is incident on.

  The signal light to which information is added by the spatial light modulator 312 reflects the PBS prism 311 and propagates through the relay lens 313 and the spatial filter 314. Thereafter, the signal light is condensed on the optical information recording medium 1 by the objective lens 315.

  On the other hand, the light beam reflected from the PBS prism 305 functions as reference light 307 and is set to a predetermined polarization direction according to recording or reproduction by the polarization direction conversion element 316 and then galvano- lated via the mirror 317 and the mirror 318. Incident on the mirror 319.

  At this time, the polarization direction of the servo light is generated in addition to the polarization component of the hologram reproduction light by slightly changing the polarization direction by the wave plate 333 during reproduction. In the example of this figure, the p-polarized light is the polarization component of the reproduction light, and the s-polarization is the polarization component of the servo light. Hereinafter, the reproduction light is referred to as reference light, and the servo light is referred to as servo light.

  Thereafter, the propagation angle of the p-polarized light and the s-polarized light is separated by a desired angle by a polarization separation element 334 such as a Wollaston prism. At this time, the direction in which the angle difference is given is the Bragg direction, that is, the direction of the angle at which the reference light is scanned during multiple recording. At the time of recording, the rotation angle of the wave plate 333 is set to an angle at which no polarization component of servo light is generated. In this specification, the method of generating servo light is described using an example using polarized light. However, as long as an angle difference can be given between the reference light and the servo light, a configuration without using polarized light may be used.

  Since the angle of the galvanometer mirror 319 can be adjusted by the actuator 320, the incident angle of the reference light incident on the optical information recording medium 1 after passing through the lens 321 and the lens 322 can be set to a desired angle. In order to set the incident angle of the reference light, an element that converts the wavefront of the reference light may be used instead of the galvanometer mirror.

  In this specification, for example, the reference light angle is defined as a positive direction for a counterclockwise direction and a negative direction for a clockwise direction, with the direction perpendicular to the optical information recording medium being 0 degrees as shown in the figure.

  In this way, the signal light and the reference light are incident on the optical information recording medium 1 so as to overlap each other, whereby an interference fringe pattern is formed in the recording medium, and information is recorded by writing this pattern on the recording medium. To do. In addition, since the incident angle of the reference light incident on the optical information recording medium 1 can be changed by the galvanometer mirror 319, recording by angle multiplexing is possible.

  Hereinafter, in holograms recorded in the same area with different reference beam angles, holograms corresponding to each reference beam angle are called pages, and a set of pages angle-multiplexed in the same area is called a book. .

  FIG. 3 shows the principle of reproduction in an example of the basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. When reproducing the recorded information, the reference light is incident on the optical information recording medium 1 as described above, and the light beam transmitted through the optical information recording medium 1 is reflected by the galvanometer mirror 324 whose angle can be adjusted by the actuator 323. By doing so, the reproduction reference light is generated.

  The reproduction light reproduced by the reproduction reference light propagates through the objective lens 315, the relay lens 313, and the spatial filter 314. Thereafter, the reproduction light passes through the PBS prism 311 and enters the photodetector 325, and the recorded signal can be reproduced. As the photodetector 325, for example, an image sensor such as a CMOS image sensor or a CCD image sensor can be used. However, any element may be used as long as page data can be reproduced. At this time, when the light is reflected by the galvanometer mirror 324, the reference light angle is reflected vertically, for example.

  A control signal for controlling the galvanometer mirror 319 for setting the reference light angle is generated by an optical system below the optical information recording medium 1 as shown in the figure, for example. During reproduction, since the reference light and the servo light are simultaneously irradiated onto the optical information recording medium, both the p-polarized reproduction light by the reference light and the s-polarized reproduction light by the servo light are simultaneously diffracted. Both the reference light and the reproduction light by the servo light are converted into parallel light by the lens 326, and then, for example, the light is converged by the lens 327, and then the p-polarized light and the s-polarized light are separated by the PBS prism 328, and each light is detected. Detectors 329 and 330 detect. The servo control signal is calculated, for example, by performing a differential operation on the signals obtained by the photodetectors 329 and 330.

  FIG. 4 shows an operation flow of recording and reproduction in the optical information recording / reproducing apparatus 10. Here, a flow relating to recording / reproduction using holography in particular will be described.

  FIG. 4a shows an operation flow from when the optical information recording medium 1 is inserted into the optical information recording / reproducing apparatus 10 until preparation for recording or reproduction is completed, and FIG. 4b shows information from the ready state to the optical information recording medium 1. FIG. 4C shows an operation flow until the information recorded on the optical information recording medium 1 is reproduced from the ready state.

  When a medium is inserted as shown in FIG. 4a (401), the optical information recording / reproducing apparatus 10 discriminates whether or not the inserted medium is a medium for recording or reproducing digital information using holography, for example (see FIG. 4a). 402).

  As a result of disc discrimination, when it is determined that the optical information recording medium records or reproduces digital information using holography, the optical information recording / reproducing apparatus 10 reads control data provided on the optical information recording medium (403). ), For example, information relating to the optical information recording medium and information relating to various setting conditions during recording and reproduction, for example.

  After reading out the control data, various adjustments according to the control data and learning processing (404) related to the pickup 11 are performed, and the optical information recording / reproducing apparatus 10 is ready for recording or reproduction (405).

  As shown in FIG. 4B, the operation flow from the ready state to recording of information first receives data to be recorded (411), and sends information corresponding to the data to the spatial light modulator in the pickup 11.

  Thereafter, various recording learning processes such as optimization of the power of the light source 301 and optimization of exposure time by the shutter 303 are performed in advance so that high-quality information can be recorded on the optical information recording medium (412). ).

  Thereafter, in the seek operation (413), the access control circuit 81 is controlled to position the pickup 11 and the cure optical system 13 at predetermined positions on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

  Thereafter, a predetermined region is pre-cured using a light beam emitted from the cure optical system 13 (414), and data is recorded using reference light and signal light emitted from the pickup 11 (415).

  After the data is recorded, post cure is performed using the light beam emitted from the cure optical system 13 (416). Data may be verified as necessary.

  As shown in FIG. 4C, the operation flow from the ready state to the reproduction of recorded information is as follows. First, in the seek operation (421), the access control circuit 81 is controlled, and the pickup 11 and the reproduction reference light optical system 12 are controlled. Is positioned at a predetermined position on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

  Thereafter, the reference light is emitted from the pickup 11, the information recorded on the optical information recording medium is read (422), and the reproduction data is transmitted (423).

  Next, signal generation and processing during recording / reproduction will be described with reference to FIGS.

  First, the configuration of the signal generation circuit 86 of the optical information recording / reproducing apparatus 10 and the recording data processing during data recording will be described with reference to FIGS. 5 and 7a. FIG. 5 is a block diagram of the signal generation circuit 86 of the optical information recording / reproducing apparatus 10, and FIG. 7a is a flow of data processing at the time of recording in the signal generation circuit 86, mainly two-dimensional data to be recorded on the medium from user data. The flow to generate is shown.

  The two-dimensional data includes a plurality of pixels arranged in a grid, and is represented by pixels having a bright (white) pixel and dark (black) luminance. Henceforth, a pixel with a bright brightness | luminance is set to an on pixel, and a pixel with a brightness | luminance is a dark pixel.

  When the input of user data is started to the output control circuit 90, the input / output control circuit 90 notifies the controller 89 that the input of user data has started. In response to this notification, the controller 89 instructs the signal generation circuit 86 to record data for one page input from the input / output control circuit 90.

  When the signal processing circuit 86 receives the user data (701), a processing command from the controller 89 is notified to the sub-controller 501 in the signal generation circuit 86 via the control line 508.

  The sub-controller 501 receives this notification, and the sub-controller 501 controls each signal processing circuit via the control line 508 so that the signal processing circuits are operated in parallel.

  First, the memory control circuit 503 controls to store user data input from the input / output control circuit 90 via the data line 509 in the memory 502.

  When the user data stored in the memory 502 reaches a certain amount, the CRC calculation circuit 504 divides the user data into a plurality of data strings and converts each data string into a CRC so that error detection can be performed during reproduction (702). ).

  The scramble circuit 505 scrambles the pseudo-random data sequence by adding the pseudo-random data sequence to the CRC-encoded data sequence for the purpose of making the number of on-pixels and the number of off-pixels substantially equal and preventing repetition of the same pattern (703).

  The error correction encoding circuit 506 performs error correction encoding by adding a parity data string such as a Reed-Solomon code so that error correction during reproduction can be performed (704).

  Finally, the pickup interface circuit 507 converts the data into M × N two-dimensional data, and repeats it for one page data to construct one page of two-dimensional data (705). On the other hand, a reference marker for image position detection and image distortion correction at the time of reproduction is added (706), and the data is transferred to the spatial light modulator 312 (707).

  Next, the configuration of the signal processing circuit 85 of the optical information recording / reproducing apparatus 10 and the reproduction data processing during data reproduction will be described with reference to FIGS. 6 and 7b.

  FIG. 6 is a block diagram of the signal processing circuit 85 of the optical information recording / reproducing apparatus 10, and FIG. 7B is a data processing flow during reproduction by the signal processing circuit 85.

  When the photodetector 325 in the pickup 11 detects image data (711), the controller 89 instructs the signal processing circuit 85 to reproduce the data for one page input from the pickup 11.

  A processing command from the controller 89 is notified to the sub-controller 601 in the signal processing circuit 85 via the control line 611. Upon receiving this notification, the sub-controller 601 controls each signal processing circuit via the control line 611 so that each signal processing circuit operates in parallel.

  The memory control circuit 603 controls the image data input from the pickup 11 via the pickup interface circuit 610 via the data line 612 to be stored in the memory 602.

  When the data stored in the memory 602 reaches a certain amount, the image position detection circuit 609 detects the image position based on the marker from the image data stored in the memory 602 (712).

  The image distortion correction circuit 608 uses the detected markers to perform distortion correction such as image tilt, magnification, and distortion in the image distortion correction circuit 608 (713), and the image data is converted into the expected two-dimensional data size. Convert.

  The binarization circuit 607 binarizes each bit data of a plurality of bits constituting the size-converted two-dimensional data in the binarization circuit 607 to determine “0” and “1” (715), and stores them on the memory 602. Control to store the data in the output data output sequence.

  The error correction circuit 606 converts the two-dimensional data obtained in this way into a plurality of data strings, and then performs error correction processing (717) included in each data string to remove the parity data string.

  The scramble release circuit 605 releases the scramble to add the pseudo random number data string (718). The CRC calculation circuit 604 performs error detection processing by CRC (719), deletes the CRC parity, confirms that no error is included in the user data on the memory 602, and sends the user data to the input / output control circuit 90 from the memory 602. Data is transferred (720).

  FIG. 8 is a schematic diagram illustrating an example of a control signal in the optical information recording / reproducing apparatus. The horizontal axis indicates the reference light angle, and the vertical axis indicates the signal intensity in (a) and the control signal intensity in (b).

  The diffracted light when reproduced with s-polarized light and the diffracted light when reproduced with p-polarized light have peaks at positions shifted by an angle corresponding to the separation angle of a polarization separation element such as a Wollaston prism, as shown. At this time, the signal obtained by taking the difference between the output values from the detector that receives the p-polarized light and the s-polarized diffracted light has an s-shaped waveform as shown in FIG. Since the control signal is different in sign when it is on the minus side and when it is on the minus side, it becomes an index indicating the control direction.

  Therefore, this s-shaped waveform signal can be used as a reference light control signal to control an element that changes the reference light angle, such as a galvanomirror. When controlling the galvanometer mirror 319, for example, first, the control signal is controlled to the first control target point θ1 so that the control signal crosses zero. Thereafter, in order to maximize the amount of diffracted light in the reference light, the reference light is moved by an angle amount that is half the separation angle, and moved to the second control target point θ2.

  FIG. 9 is a schematic diagram illustrating an example of fluctuations in a reproduction signal and a control signal in the optical information recording / reproducing apparatus.

  In general, the efficiency of the optical component such as transmittance or reflectance varies depending on the incident angle as shown in FIG. 9a. In the angle multiplexing type holographic memory, the reference light angle range is used within a range of several tens of degrees, and therefore, it is easily affected by the difference in efficiency according to the angle.

  Further, the efficiency and the angle dependency of efficiency generally vary depending on the vibration direction of light such as s-polarized light and p-polarized light. For example, in the case of the transmittance characteristics of s-polarized light and p-polarized light as shown in FIG. 9a, the light quantity of the reproduction signal is relatively lower than that of s-polarized light as shown in FIG. 9b.

  When the ratio differs from the design value depending on the angle, a DC offset is generated in the vertical direction as shown in FIG. 9c in the control signal of the galvano mirror, and the control target point to be controlled as shown in FIG. Since an angle difference occurs at the zero cross point, a control error of the reference beam angle occurs. Therefore, in the present invention, the DC offset of the control signal is calculated by calculating the control signal by performing a differential operation after adjusting the gain so that the peak values of the signal intensities of the s-polarized light and the p-polarized light are always substantially matched according to the angle. For this reason, the control error of the reference light is reduced.

  Here, the signal ratio adjustment method will be described with reference to FIGS. 10 and 11.

  FIG. 10 is a schematic diagram showing an example of signal ratio adjustment in the optical information recording / reproducing apparatus, and FIG. 11 is a diagram showing an operation flow of signal ratio adjustment.

  First, a method for learning the gain amount of s / p polarization will be described with reference to FIG.

  For example, the gain amount is learned after receiving a reproduction command or when a large reproduction error occurs. At the time of learning, first, the optical information recording medium is positioned on a learning book or a book in which predetermined data is recorded, and the angle dependency of the signal light quantity of s-polarized light and p-polarized light is measured.

  The reproduction error is estimated using, for example, a known area in the page. After that, a gain amount is calculated such that the signal light amount for each angle is approximately the same for s-polarized light and p-polarized light. At this time, not only the peak value but also the adjustment amount that matches the bottom value of the signal may be learned. The correction amount learning will be described in detail with reference to FIG.

  The amount of gain for adjustment obtained by learning is stored in a memory. Of course, if optical characteristics such as transmittance and reflectance of the optical information recording medium are known in advance, the gain amount may be calculated using the information.

  At the time of data reproduction, the gain amount for adjustment stored in the memory is referred to, and at least one of p-polarized light or s-polarized light gain is adjusted for each reference light angle, the signal ratio is substantially matched, and then differential calculation is performed. To generate a control signal. This adjustment eliminates the angular deviation of the zero cross point.

  If the signal ratio of s-polarized light and p-polarized light is substantially the same within the scanning range of the reference light angle, the angle error at the zero cross point is eliminated even if the signal light amount varies for each angle within the same polarized light. However, in order to effectively use the dynamic range of the number of calculation bits, it is desirable that the signal light amount for each angle within the same polarized light is substantially matched.

  In the following embodiments, the reference light angle scanning range refers to a range of all angles that can be taken by the reference light when recording and reproduction is performed by changing the angle of the reference light with a device such as a galvano mirror.

  FIG. 11 shows an example of an operation flow of signal ratio adjustment in the optical information recording / reproducing apparatus described in FIG.

  FIG. 11a shows an operation flow of signal ratio adjustment.

  First, the Bragg selectivity of s-polarized light and p-polarized light to be reproduced for gain adjustment amount learning is detected (1101).

  Next, as shown in FIG. 11b, the peak light amount and the bottom light amount of each page are calculated by s-polarized light and p-polarized light (1102). As the peak light amount and the bottom light amount, for example, the detection signal is divided into a plurality of signals, and the maximum light amount in the divided signal is the peak light amount and the minimum light amount is the bottom light amount.

  Here, when the peak light amounts are substantially matched, when the peak light amount for s-polarized light of the i-th page at learning is Psi and the peak light amount for P-polarized light is Ppi, the p-polarized i-th page at the time of data reproduction. Correction is made, for example, by multiplying the reproduction light amount Ipi in the vicinity of the peak by Psi / Ppi to obtain αi = Ipi × Psi / Ppi. As an example, the case of adjusting the amount of reproduction light with p-polarized light has been described. Of course, the amount of light reproduced with s-polarized light, or both s-polarized light and p-polarized light may be adjusted.

  The reproduction light amount Ipi near the peak of the i-th page is obtained, for example, by dividing the detection signal into a plurality of signals for the page. As the control signal for the i-th page, the reproduction light amount in the vicinity of the peak of the i-th page of s-polarized light can be calculated as, for example, αi−βi. The point of this adjustment is that the signal is adjusted with a different gain amount for each page within the range of the scanning angle of the reference light.

  Also, when the peak light amount and the bottom light amount are substantially matched, the peak light amount for s-polarized light of page i at the time of learning is Psi, the bottom light amount is Bsi, the peak light amount for p-polarized light is Ppi, and the bottom light amount is Bpi. For example, correction is performed by setting the reproduction light amount Ipi near the peak of the i-th page of p-polarized light at the time of data reproduction to α′i = (Ipi−Bpi) × (Psi−Bsi) / (Ppi−Bpi) + Bsi.

  As an example, the case of adjusting the amount of reproduction light with p-polarized light has been described. Of course, the amount of light reproduced with s-polarized light, or both s-polarized light and p-polarized light may be adjusted. For example, when adjusting both s-polarized light and p-polarized light, the reproduction light amount Ipi near the peak of the i-th page of p-polarized light at the time of data reproduction is expressed as α′i = (Ipi−Bpi) / (Ppi−Bpi). And the reproduction light amount Isi near the peak of the s-polarized i-th page during data reproduction is β′i = (Isi−Bsi) / (Psi−Bsi). The control signal for the i-th page can be calculated by, for example, α′i−β′i.

A gain correction amount is learned so that the peak value and / or the bottom value of s-polarized light and p-polarized light substantially coincide with each reference light angle, and stored in the memory (1103).
At the time of data reproduction, after correcting the detection signal of each page using the learning value, a control signal for the reference beam angle is generated to obtain a corrected control signal (1104).

  The method according to the present embodiment has an advantage that the reference light angle can be controlled with higher accuracy by suppressing the fluctuation of the control signal caused by the difference in the reproduction light quantity between the s-polarized light and the p-polarized light.

  In the following description, description of parts common to the present embodiment will be omitted.

  A second embodiment of the present invention will be described with reference to FIG. The apparatus configuration can be realized with the same configuration as that of the first embodiment, and thus the description thereof is omitted. FIG. 12 is a schematic diagram showing an example of an operation flow of signal ratio adjustment in the optical information recording / reproducing apparatus.

  The black selectivity of s-polarized light and p-polarized light of several pages in the book to be reproduced for gain adjustment amount learning is acquired (1201). The peak light amount and the bottom light amount of each acquired page are detected (1202). As a detection method, for example, the same method as in the first embodiment is performed. In each page, a gain correction amount is learned so that the peak light amount and the bottom light amount of s-polarized light and p-polarized light substantially coincide with each other (1203). The gain correction amount of all pages in the book is calculated by interpolation calculation from the reference light angle and the gain correction amount obtained by learning (1204). As interpolation, linear interpolation may be used, or nonlinear interpolation calculation may be performed. At the time of data reproduction, a corrected control signal is obtained by generating a control signal for the reference beam angle after correcting the detection signal of each page (1205).

  In order to reduce the amount of error, it is desirable to select a page to be reproduced for learning in a scanning range with a wide reference light angle, such as the first page, the intermediate page, and the last page.

  The method of the present embodiment has an advantage that the time required for learning can be shortened compared with the method of the first embodiment because the number of pages to be reproduced for learning the adjustment amount is reduced and interpolation calculation is performed.

  A third embodiment of the present invention will be described with reference to FIG. The apparatus configuration can be realized with the same configuration as that of the first embodiment, and thus the description thereof is omitted. FIG. 13 is a schematic diagram showing an example of an operation flow of signal ratio adjustment in the optical information recording / reproducing apparatus.

  The black selectivity of s-polarized light and p-polarized light is acquired in several books on the disk to be reproduced for learning the gain adjustment amount (1301). The peak light amount and the bottom light amount are detected in each page of each detected book (1302). As a detection method, for example, the same method as in the first embodiment is performed. In each page, a gain correction amount is learned so that the peak light amount and the bottom light amount of s-polarized light and p-polarized light substantially coincide with each other (1303). The gain correction amount of all books is calculated by interpolation calculation from the position on the disc and the learning amount (1304). As interpolation, linear interpolation may be used, or nonlinear interpolation calculation may be performed. At the time of data reproduction, a corrected control signal is obtained by generating a control signal for the reference beam angle after correcting the detection signal of each page (1305).

  In order to reduce the amount of error, it is desirable to select a wide range such as the innermost circumference, the outermost circumference, and the middle of the book to be reproduced for learning. Further, some learning books may be selected within a wide range of the disk rotation angle.

  Further, in order to reduce the influence of noise received in the detection of the peak light amount and the bottom light amount, detection may be performed a plurality of times, and the peak light amount and the bottom light amount may be calculated using average values.

  Further, the reproduction with each book at the time of learning may reproduce only a few pages as in the method of the second embodiment, and the correction amount for each page of the book may be calculated by interpolation calculation.

  The method of the present embodiment has an advantage that it is possible to generate a control signal with good quality even when the characteristics of the transmittance for each angle fluctuate depending on the position on the disk.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

1 ... Optical information recording medium,
10: Optical information recording / reproducing apparatus, 11: Pickup,
12 ... Reference light optical system for reproduction, 13 ... Disc Cure optical system,
14 ... Optical system for detecting disk rotation angle, 81 ... Access control circuit,
82... Light source drive circuit, 83... Control signal generation circuit,
84 ... Servo control circuit, 85 ... Signal processing circuit, 86 ... Signal generation circuit,
87 ... Shutter control circuit, 88 ... Disc rotation motor control circuit,
89 ... Controller, 90 ... Input / output control circuit, 91 ... External control device, 92 ... Signal adjustment circuit,
301 ... Light source, 302 ... Collimating lens, 303 ... Shutter,
304 ... 1/2 wavelength plate, 305 ... PBS prism, 306 ... signal light,
307: Reference beam, 308: Beam expander, 309: Phase mask,
310 ... relay lens, 311 ... PBS prism, 312 ... spatial light modulator,
313 ... Relay lens, 314 ... Spatial filter, 315 ... Objective lens,
316: Polarization direction conversion element, 317 ... Mirror, 318 ... Mirror, 319 ... Mirror,
320 ... Actuator, 321 ... Lens, 322 ... Lens,
323 ... Actuator, 324 ... Mirror, 325 ... Photodetector,
326 ... lens, 327 ... lens, 328 ... PBS prism,
329 ... Photodetector, 330 ... Photodetector, 333 ... Wave plate, 334 ... Polarization separation element,

Claims (16)

In an optical information reproducing apparatus for reproducing information recorded using holography from an optical information recording medium,
A laser light source for generating reference light;
An optical axis branching section that branches the reference light into a plurality of reference lights having different angles;
An angle adjusting unit for adjusting an angle at which the plurality of branched reference lights are incident on the optical information recording medium;
A light detection unit having a plurality of light receiving surfaces for irradiating the optical information recording medium with the plurality of branched reference lights and detecting a plurality of reproduced diffracted lights;
A signal adjustment unit that adjusts signal ratios of a plurality of signals detected by the light detection unit;
A control signal calculation unit that generates a control signal based on a signal output from the signal adjustment unit,
The angle adjusting unit controls an angle at which the reference light is incident on the optical information recording medium by the angle adjusting unit based on a control signal output from the control signal calculating unit. The optical information reproducing apparatus according to claim 1,
The signal adjustment unit adjusts the signal ratio so that the peak signal ratio, the peak signal difference, or the peak signal of the plurality of diffracted light signals output from the light detection unit substantially match within the scanning range of the reference light angle. adjust,
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 1,
The signal adjustment unit adjusts the signal ratio so that the offset signal ratio, the offset signal difference, or the offset signal of the plurality of diffracted light signals output from the light detection unit substantially match within the scanning range of the reference light angle. adjust,
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 1,
The signal adjustment unit adjusts the signal ratio so that the peak signals substantially match within the scanning range of the reference light angle in each of the plurality of diffracted lights output from the light detection unit,
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 1,
The signal adjustment unit adjusts the signal ratio so that the offset signals substantially match within the scanning range of the reference light angle in each of the plurality of diffracted lights output from the light detection unit,
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 1,
The signal adjustment unit includes a memory, calculates a signal ratio adjustment amount for adjustment, stores the calculated signal ratio adjustment amount in the memory, and adjusts the signal when adjusting the signal. Adjust the signal ratio based on the ratio adjustment amount,
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 6,
In holograms recorded in the same area of the optical information recording medium by changing the reference light angle, a hologram corresponding to each reference light angle is set as a page, and a set in which the pages are angle-multiplexed by a plurality of pages in the same area. If it is a book,
When calculating the signal ratio adjustment amount, the signal adjustment unit calculates the signal ratio adjustment amount of a part of pages included in the book, and interpolates the calculated signal ratio adjustment amount, so that the book Calculate the signal ratio adjustment amount of all pages included in the
An optical information reproducing apparatus characterized by the above. The optical information reproducing apparatus according to claim 6,
In holograms recorded in the same area of the optical information recording medium by changing the reference light angle, a hologram corresponding to each reference light angle is set as a page, and a set in which the pages are angle-multiplexed by a plurality of pages in the same area. If it is a book,
When the signal adjustment unit calculates the signal ratio adjustment amount, the signal adjustment unit calculates the signal ratio adjustment amount of a part of the books recorded on the optical information recording medium, and supplements the calculated signal ratio adjustment amount. Then, the signal ratio adjustment amount of all the books included in the optical information recording medium is calculated.
An optical information reproducing apparatus characterized by the above. In an optical information reproducing method for reproducing information recorded using holography from an optical information recording medium,
A reference light generation step for generating the reference light;
An optical axis branching step of branching the reference light into a plurality of reference lights having different angles;
An angle adjusting step of adjusting an angle of the plurality of branched reference lights;
A light detecting step having a plurality of light receiving surfaces for irradiating the optical information recording medium with the branched reference lights and detecting a plurality of reproduced diffracted lights;
A signal adjustment step of adjusting the signal ratio of each of the plurality of signals detected in the light detection step;
A control signal calculation step of generating a control signal based on the signal output by the signal adjustment step,
In the optical information reproducing method, the angle adjusting step controls an angle at which the reference light is incident on the optical information recording medium by the angle adjusting unit based on a control signal output from the control signal calculating step. The optical information reproducing method according to claim 9, wherein
In the signal adjustment step, the signal ratio is adjusted so that the peak signal ratio, the peak signal difference, or the peak signal of the plurality of diffracted light signals output from the light detection step substantially match within the scanning range of the reference light angle. adjust,
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 9, wherein
In the signal adjustment step, the signal ratio is set so that the offset signal ratio, the offset signal difference, or the offset signal of the plurality of diffracted light signals output from the light detection step substantially match within the scanning range of the reference light angle. adjust,
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 9, wherein
The signal adjustment step adjusts the signal ratio so that the peak signals substantially match within the scanning range of the reference light angle in each of the plurality of diffracted lights output from the light detection step.
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 9, wherein
The signal adjustment step adjusts the signal ratio so that the offset signals substantially match within the scanning range of the reference light angle in each of the plurality of diffracted lights output from the light detection step.
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 9, wherein
The signal adjustment step calculates a signal ratio adjustment amount for adjustment, stores the calculated signal ratio adjustment amount, and adjusts the signal ratio based on the stored signal ratio adjustment amount when adjusting the signal. adjust,
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 14,
In holograms recorded in the same area of the optical information recording medium by changing the reference light angle, a hologram corresponding to each reference light angle is set as a page, and a set in which the pages are angle-multiplexed by a plurality of pages in the same area. If it is a book,
In the signal adjustment step, when calculating the signal light ratio adjustment amount, the signal ratio adjustment amount of a part of pages included in the book is calculated, and the calculated signal ratio adjustment amount is interpolated. Calculate the signal ratio adjustment amount of all pages included in the
An optical information reproducing method characterized by the above. The optical information reproducing method according to claim 14,
In holograms recorded in the same area of the optical information recording medium by changing the reference light angle, a hologram corresponding to each reference light angle is set as a page, and a set in which the pages are angle-multiplexed by a plurality of pages in the same area. If it is a book,
When calculating the signal ratio adjustment amount, the signal adjustment step calculates the signal ratio adjustment amount of a part of the books recorded on the optical information recording medium, and complements the calculated signal ratio adjustment amount. Then, the signal ratio adjustment amount of all the books included in the optical information recording medium is calculated.
An optical information reproducing method characterized by the above.

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