Patent Grant
9087522
This application claims the priority of Japanese Patent Application No. 2013-190001, filed on Sep. 13, 2013, which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an optical information reproducing device to reproduce information recorded on an optical information recording medium using interference of a signal beam and a reference beam and a reference beam adjusting method.
2. Description of the Related Art
Hologram recording technology for recording digital information using holography has attracted attention during making a study of next-generation storage technology.
The hologram recording technology is technology for overlapping a signal beam having information of page data modulated two-dimensionally by a spatial light modulator to a reference beam in a recording medium, generating refractive index modulation in the recording medium by a fringe pattern generated at that time, and recording information on the recording medium.
At the time of reproducing information, if the recording medium is irradiated with the reference beam used at the time of recording, a hologram recorded on the recording medium acts like a diffraction grating to generate diffracted light. The diffracted light is reproduced as the same light as the recorded signal beam, including phase information.
The reproduced signal beam is detected two-dimensionally using a light detector such as a CMOS or a CCD. As such, the hologram recording technology enables two-dimensional information to be recorded/reproduced on the optical recording medium at one time by one hologram and enables a plurality of page data to be overwritten to the same place of the recording medium by changing an angle of the reference beam radiated to the recording medium at the time of recording, thereby enabling large-capacity and high-speed information to be recorded/reproduced.
In the reproduction of the hologram, if the recording medium is contracted/expanded according to a temperature, an angle and an interval of a grating recorded as the diffraction grating change, so that a signal quality of reproduction light is deteriorated. In order to compensate for the deterioration in the signal quality, it is necessary to adjust an incidence angle and a wavelength of the reference beam radiated to the recording medium. A method of detecting a characteristic of the reproduction light and adjusting the incidence angle and the wavelength of the reference beam has been suggested (for example, refer to WO 2011/018836 A).
In the method disclosed in WO 2011/018836 A, the radiation angle and the wavelength of the reference beam are individually adjusted and a step of performing feedback control on the radiation angle of the reference beam and adjusting the radiation angle and a step of performing the feedback control on the wavelength and adjusting the wavelength are included. In addition, in a hologram recording/reproducing device, an external cavity laser diode (ECLD) having an external resonator with a variable wavelength is used as a light source of the reference beam. When the wavelength changes, it takes several seconds to stabilize the wavelength. For this reason, when the feedback control is performed on the wavelength, the feedback control needs to be performed in a low control band of 1 Hz or less and it takes a long time to converge light of the wavelength.
An object of the present invention is to provide an optical information reproducing device and a reference beam adjusting method that can adjust an angle of a reference beam and a wavelength of the reference beam in short time.
In order to resolve the above-described problems, for example, configurations described in claims may be adopted. For example, the above object can be achieved by including: a light source that emits light to the optical information recording medium; a light source control unit that controls a wavelength of the light emitted from the light source; a reference beam angle control unit that controls an incidence angle of the reference beam to the optical information recording medium; a light detector that detects a reproduction image from the optical information recording medium or a brightness distribution of the reproduction image; a reproduction image processing unit that detects a bright line of the reproduction image on the basis of a detection result of the light detector and outputs a detection result of the bright line; and a control unit that controls the wavelength of the light emitted from the light source through the light source control unit, on the basis of an output of the reproduction image processing unit, and controls the incidence angle of the reference beam through the reference beam angle control unit.
According to the present invention, an optical information reproducing device and a reference beam adjusting method that can adjust an angle of a reference beam and a wavelength of the reference beam in short time can be provided.
Hereinafter, embodiments of the present invention will be described using the drawings.
Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating an example of a recording/reproducing device of an optical information recording medium that records/reproduces digital information using holography.
An optical information recording/reproducing device 10 is connected to an external control device 30 through an input/output control unit 27. When recording is performed, the optical information recording/reproducing device 10 receives a recorded information signal from the external control device 30 by the input/output control unit 27. When reproduction is performed, the optical information recording/reproducing device 10 transmits the reproduced information signal to the external control device 30 by the input/output control unit 27.
The optical information recording/reproducing device 10 includes a pickup 11, a reproducing reference beam optical system 12, a cure optical system 13, a disk rotation angle detecting optical system 14, and a rotation motor 15 and an optical information recording medium 1 is rotatable by the rotation motor 15. A controller unit 16 is configured with a central processing unit (CPU). The controller unit 16 exchanges a signal with individual units configuring the optical information recording/reproducing device 10, according to a program or data stored in a storage unit 26, and wholly controls the optical information recording/reproducing device 10.
The pickup 11 performs a function of radiating a reference beam and a signal beam to the optical information recording medium 1 and recording digital information using holography. At this time, the recorded information signal is transmitted to a spatial light modulator to be described below in the pickup 11 through a signal generating unit 17 by the controller unit 16 and the signal beam is modulated by the spatial light modulator.
When the information recorded on the optical information recording medium 1 is reproduced, a light wave to cause the reference beam emitted from the pickup 11 to be incident on the optical information recording medium in a direction opposite to an incidence direction at the time of recording is generated by the reproducing reference beam optical system 12. Reproduction light reproduced by the reproducing reference beam is detected by the light detector to be described below in the pickup 11 and a signal is reproduced by the signal processing unit 18. In addition, an output of the light detector is also input to the reproduction image processing unit 23 and a processing result corresponding to the reproduction image on the light detector or a brightness distribution of the reproduction image is output to the controller unit 16. A place where a portion having high brightness in the reproduction image is linear is defined as a bright line. In this embodiment, the case in which a bright line angle formed by a bright line of the reproduction image when an incidence angle of the reference beam and the wavelength of the wavelength variable light source are optimal and a bright line of the reproduction image on the light detector is detected in the reproduction image processing unit 23 will be described.
In the controller unit 16, a deviation of the incidence angle of the reference beam to the optical information recording medium 1 and a deviation of the wavelength of the reference beam are detected on the basis of the bright line angle of the reproduction image. In the controller unit 16, a mechanism provided in the optical pickup 11 is controlled by the reference beam angle control unit 25, so that the incidence angle of the reference beam to the optical information recording medium 1 is adjusted and the wavelength of the light source of the reference beam mounted to the optical pickup 11 is adjusted by the light source control unit 21.
The shutter control unit 19 controls an opening/closing time of a shutter in the pickup 11, on the basis of a command from the controller unit 16, to adjust radiation times of the reference beam and the signal beam radiated to the optical information recording medium 1 at the time of recording.
The cure optical system 13 performs a function of generating light beams used for precure and postcure of the optical information recording medium 1. The precure is a preprocess for radiating a predetermined light beam in advance before radiating the reference beam and the signal beam to a desired position, when information is recorded on the desired position in the optical information recording medium 1. The postcure is a postprocess for radiating a predetermined light beam to disable additional recording on the desired position, after the information is recorded on the desired position in the optical information recording medium 1.
The disk rotation angle detecting optical system 14 is used to detect a rotation angle of the optical information recording medium 1. When the rotation angle of the optical information recording medium 1 is adjusted to a predetermined rotation angle, a signal according to the rotation angle is detected by the disk rotation angle detecting optical system 14 and the disk rotation motor control unit 20 performs control using the detected signal, such that the rotation angle of the optical information recording medium 1 becomes the rotation angle commanded by the controller unit 16.
In the light source control unit 21, each of the light sources of the signal beam and the reference beam mounted to the pickup 11 is driven to emit a light beam at a predetermined light amount and a predetermined wavelength and each of the light sources in the cure optical system 13 and the disk rotation angle detecting optical system 14 is driven to emit a light beam at a predetermined light amount.
In addition, in the pickup 11 and the cure optical system 13, mechanisms (not illustrated in the drawings) for enabling sliding in a radial direction of the optical information recording medium 1 are provided and position control is performed through the access control unit 22.
The light beam having transmitted the PBS prism 205 functions as a signal beam 206 and a light beam diameter thereof is increased by a beam expander 208. Then, the light beam transmits a phase mask 209, a relay lens 210, and a PBS prism 211 and is incident on a spatial light modulator 212.
The signal beam to which information has been added by the spatial light modulator 212 is reflected on the PBS prism 211 and propagates through a relay lens 213 and a spatial filter 214. Then, the signal beam is condensed on the optical information recording medium 1 by an objective lens 215.
Meanwhile, the light beam having reflected on the PBS prism 205 functions as a reference beam 207 and a polarization direction thereof is set to a predetermined polarization direction according to a recording mode or a reproduction mode, by a polarization direction converting element 216. Then, the light beam is reflected on mirrors 217 and 218 and is incident on an angle correcting element 219. The angle correcting element 219 is a mechanism for rotating a wedge prism and is an element to correct an angle of a direction almost vertical to an angle multiple recording direction in the optical information recording medium 1. Here, an angle of an angle multiple direction is set as an angle θB on bragg direction and an angle of a direction almost vertical to the angle on bragg direction is set as an angle θP on pitch direction. The light beam emitted from the angle correcting element 219 is incident on a galvano-mirror 220. The galvano-mirror 220 can adjust the angle θB on bragg direction by an actuator 221. As such, the angle correcting element 219 and the galvano-mirror 220 operate as a mechanism for correcting an incidence angle of the reference beam on the optical information recording medium 1 and can set the incidence angle θB on bragg direction and the incidence angle θP on pitch direction in the reference beam incident on the optical information recording medium 1 after passing through a scanner lens 222, to desired angles.
By the operation described above, the signal beam and the reference beam are made to be incident to overlap each other in the optical information recording medium 1 to form a fringe pattern in the recording medium and information is recorded by writing the pattern to the recording medium. In addition, because the angle θB on bragg direction in the reference beam incident on the optical information recording medium 1 can be changed by the galvano-mirror 220, angle multiple recording is enabled.
Hereinafter, holograms corresponding to individual reference beam angles in holograms recorded by changing the incidence angle θB on bragg direction in the reference beam in the same region are called pages and a set of pages subjected to angle multiple recording in the same region is called a book.
The reproduction light reproduced by the reference beam for the reproduction propagates through the objective lens 215, the relay lens 213, and the spatial filter 214. Then, the reproduction light transmits the PBS prism 211, is incident on a light detector 225, and can reproduce a recorded signal. As the light detector 225, an imaging element such as a CMOS image sensor or a CCD image sensor can be used. However, if page data can be reproduced, any element may be used.
As described above, in reproduction of the hologram, if the optical information recording medium 1 is contracted/expanded according to the temperature, a quality of the reproduced signal beam is deteriorated. In addition, in recording technology using an angle multiple principle of holography, an allowance error with respect to a deviation of a reference beam angle tends to greatly decrease and a deviation of an angle of the reference beam radiated to the optical information recording medium 1 by a mounting error of the mechanism such as the disk rotation motor 15 or the pickup 11 greatly affects the quality of the signal beam. For this reason, it is necessary to adjust the angle and the wavelength of the reference beam radiated to the recording medium with respect to a deviation of the temperature with the temperature at the time of recording of the optical information recording medium 1 and a mounting error of a mechanism for each device, at the time of reproduction.
As illustrated in
As a result of the disk determination, when it is determined that the inserted medium is the optical information recording medium recording or reproducing the digital information using the holography, the optical information recording/reproducing device 10 reads control data recorded on the optical information recording medium (403) and acquires information regarding the optical information recording medium or information regarding various setting conditions at the time of recording or reproduction.
After the control data is read, various adjustments according to the control data or a learning process (404) regarding the pickup 11 is executed and the optical information recording/reproducing device 10 completes the preparation for the recording or reproduction (405).
In the operation flow until the information is recorded after the preparation is completed, as illustrated in
Then, various learning processes for recording such as power optimization of the light source 201 or optimization of an exposure time by the shutter 203 are executed in advance according to necessity, such that information of a high quality can be recorded on the optical information recording medium (412).
Then, in a seek operation (413), the access control unit 22 is controlled and a position of each of the pickup 11 and the cure optical system 13 is arranged to a predetermined position of the optical information recording medium. When the optical information recording medium 1 has address information, the address information is reproduced and it is confirmed whether the position is arranged to a target position. When the position is not arranged to the target position, an operation for calculating a deviation amount with the predetermined position and arranging the position again is repeated.
Then, the precure of a predetermined region is performed by using the light beam emitted from the cure optical system 13 (414) and data is recorded using the reference beam and the signal beam emitted from the pickup 11 (415).
After the data is recorded, the postcure is performed using the light beam emitted from the cure optical system 13 (416). According to the necessity, the data may be verified.
In the operation flow until the recorded information is reproduced after the preparation is completed, as illustrated in
Then, the reference beam 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).
A data process at the time of recording will be described using
Next, the data process flow at the time of reproduction will be described using
If the user data starts to be input to the input/output control unit 27, the input/output control unit 27 notifies the controller unit 16 that the user data starts to be input. The controller unit 16 receives the notification and commands the signal generating unit 17 to execute a recording process on data corresponding to one page input from the input/output control unit 27. The process command from the controller unit 16 is notified to a subcontroller 601 in the signal generating unit 17 through a control line 608. The subcontroller 601 receives the notification and performs control of each signal processing circuit through the control line 608 to operate each signal processing circuit in parallel. First, the subcontroller 601 performs control such that a memory control circuit 603 stores user data input from the input/output control unit 27 through a data line 609 in a memory 602. If an amount of the user data stored in the memory 602 reaches a constant amount, the subcontroller 601 performs control to subject the user data to the CRC by a CRC operation circuit 604. Next, the subcontroller 601 performs scramble to add the pseudo random number data string to the data subjected to the CRC by a scramble circuit 605 and performs control to perform error correcting encoding adding the parity data string by the error correcting encoding circuit 606. Finally, the subcontroller 601 reads error correcting encoding data from the memory 602 to a pickup interface circuit 607 in arrangement order of the two-dimensional data on the spatial light modulator 212, adds the marker becoming the basis at the time of reproduction, and transmits the two-dimensional data to the spatial light modulator 212 in the pickup 11.
If the light detector 225 in the pickup 11 detects image data, the controller unit 16 commands the signal processing unit 18 to execute a reproduction process on data corresponding to one page input from the pickup 11. The process command from the controller unit 16 is notified to a subcontroller 701 in the signal processing unit 18 through a control line 711. The subcontroller 701 receives the notification and performs control of each signal processing circuit through the control line 711 to operate each signal processing circuit in parallel. First, the subcontroller 701 performs control such that a memory control circuit 703 stores image data input from the pickup 11 through a data line 712 via a pickup interface circuit 710 in a memory 702. If an amount of the data stored in the memory 702 reaches a constant amount, the subcontroller 701 performs control to detect the marker from the image data stored in the memory 702 by the image position detecting circuit 709 and extract a valid data range. Next, the subcontroller 701 performs control to correct the inclination, the magnification, and the distortion of the image by an image distortion correcting circuit 708 using the detected marker and convert a size of the image data into a size of two-dimensional data to be expected. The subcontroller 701 performs control to binarize each bit data of a plurality of bits configuring the size converted two-dimensional data to determine each bit data as “0” or “1” in a binarization circuit 707 and store data in arrangement order of outputs of the reproduction data on the memory 702. Next, the subcontroller 701 corrects an error included in each data string by an error correcting circuit 706, descrambles the scramble to add the pseudo random number data string by a descramble circuit 705, and checks whether an error is not included in the user data on the memory 702, by a CRC operation circuit 704. Then, the subcontroller 701 transmits the user data from the memory 702 to the input/output control circuit 70.
A method of adjusting an angle and a wavelength of the reference beam at the time of reproduction will be described in detail with reference to
In
In 801, the angle correcting element 219 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25 and an angle on pitch direction in the reference beam incident on the optical information recording medium 1 is changed by ΔθP.
In 802, the galvano-mirror 220 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25 and the brightness of the reproduction light detected by the reproduction image processing unit 23 is measured while an angle θB on bragg direction in the reference beam incident on the optical information recording medium 1 is changed. Thereby, the relation of the angle θB on bragg direction and the brightness of the reproduction light, illustrated in
In 803, a deviation ΔθPE from an optimal reference beam angle on pitch direction is calculated from the half-value width θBW of the reference beam angle on bragg direction, detected by 802.
In 804, the galvano-mirror 220 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25 and the angle θB on bragg direction in the reference beam incident on the optical information recording medium 1 is set to the angle θBM at which the brightness of the reproduction light is maximized, detected by 802.
In 805, the inclination of the bright line of the reproduction image is detected by the reproduction image processing unit 23.
In 806, deviation amounts from optimal values of the reference beam angle on bragg and the reference beam wavelength are calculated from the pitch direction angle deviation ΔθPE detected by 803 and the bright line angle α of the reproduction image detected by 805.
In 807, the galvano-mirror 220 and the light source 201 are controlled according to the commands from the controller unit 16 to the reference beam angle control unit 25 and the light source control unit 21 and the reference beam angle on bragg and the reference beam wavelength are set to correct the deviation amounts ΔθBE and ΔπE of the reference beam angle on bragg and the reference beam wavelength calculated by 806.
In 808, the angle correcting element 219 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25, the angle on pitch direction is set to correct the deviation ΔθPE of the angle on pitch direction, which is detected by 803, and an adjustment process ends.
By the process described above, the reference beam angle on pitch direction, the reference beam angle on bragg direction, the reference beam wavelength are set in a state in which information can be reproduced.
Next, a method of calculating the deviation ΔθPE from the optimal reference beam angle on pitch direction from the half-value width θBW of the reference beam angle on bragg direction in the process of 803 will be described.
The width of the reference beam angle on bragg direction at which the brightness becomes a predetermined level or more depends on the magnitude (absolute value) of the deviation ΔθPE from the optimal pitch direction angle. For example, the half-value width θBW of the reference beam angle on bragg direction with respect to the magnitude of the pitch direction angle deviation ΔθPE becomes almost a linear relation as illustrated in
For example, when the variation of the reference beam angle on pitch direction by the mounting error of the mechanism for each device such as the disk rotation motor 15 or the pickup 11 is set to ±ΔθPO, a change amount ΔθP of the angle on pitch direction in 801 is set to ΔθP>Δθpo. Thereby, an angle θP on pitch direction after the angle on pitch direction is changed has a mark corresponding to the change amount ΔθP of the angle on pitch direction and the magnitude and the polarity of the deviation ΔθPE from the optimal angle on pitch direction can be detected from the half-value width θBW of the reference beam angle on bragg direction.
In general, because the disk-shaped optical information recording medium 1 is mounted to the disk rotation motor 15 at the inner circumference position, the variation of the angle on pitch direction at the outer circumference is more than that at the inner circumference. Therefore, first, in the process for adjusting the angle and the wavelength of the reference beam, it is preferable to execute the process after moving the position to the adjustment position of the inner circumference of the optical information recording medium 1 by 800.
Next, a method of calculating deviation amounts from optimal values of the reference beam angle on bragg and the reference beam wavelength in 806 will be described using
Here, if the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength are set to ΔθBE and ΔλE, the bright line detected by the light detector 225 may become a circular arc and have curvature, in the case in which deviation amounts of ΔθBE and ΔλE are large in particular. This aspect is illustrated in
For example, when the deviation ΔθPE of the angle on pitch direction detected by 803 is 20 [mdeg] and the bright line angle α of the reproduction image detected by 805 is −20 [deg] (point P1), the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength become ΔθBE=−40 [mdeg] and ΔλE=−0.2 [nm], respectively. Meanwhile, when the deviation ΔθPE of the angle on pitch direction detected by 803 is 80 [mdeg] and the bright line angle α of the reproduction image detected by 805 is −20 [deg] (point P2), the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength become ΔθBE=−80 [mdeg] and ΔλE=−0.4 [nm], respectively. In addition, at the point P3 at which the polarity of the deviation θΔPE of the angle on pitch direction is opposite to that at the point P1 and the reproduction image bright line angle α is the same as that at the point P1, the polarities of the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength are opposite to those at the point P1 and the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength become ΔθBE=40 [mdeg] and ΔλE=0.2 [nm], respectively.
Therefore, the relation of the bright line angle α and the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength, corresponding to the deviation ΔθPE of the angle on pitch direction, is previously stored in the storage unit 26 and the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength can be calculated from the deviation ΔθPE of the angle on pitch direction detected by 803 and the bright line angle α of the reproduction image detected by 805.
Here, because the polarities of the bright line angle α and the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength are changed according to the polarity of the deviation ΔθPE of the angle on pitch direction, a relation of the bright line angle α and the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength, corresponding to the positive polarity of the deviation ΔθPE, is stored. With respect to the deviation ΔθPE of the negative polarity, the polarities of ΔθBE and ΔλE stored for the positive polarity may be inverted, thereby decreasing an amount of data to be stored.
In addition, the deviation ΔθPE of the angle on pitch direction and the bright line angle α [deg] may be thinned out and stored and a supplementary process may be executed according to the deviation ΔθPE of the angle on pitch direction and the bright line angle α of the reproduction image, which have been detected. For example, deviation amounts ΔθBE(60) and ΔλE(60) from optimal conditions of a reference beam angle on bragg and a reference beam wavelength in the deviation ΔθPE=60 [mdeg] of the angle on pitch direction and the bright line angle α=−20[deg] of the reproduction image, which are illustrated at the point P4 of
ΔθBE(60)=ΔθBE(20)+(ΔθBE(80)−ΔθBE(20))·(60−20)/(80−20)=−40+(−80+40)·40/60=−67 [mdeg] (Mathematical Formula 1)
ΔλE(60)=ΔλE(20)+(ΔλE(80)−ΔλE(20))·(60−20)/(80−20)=−0.2+(−0.4+0.2)·40/60=−0.33 [nm] (Mathematical Formula 2)
In the above process, the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength are detected, so that the reference beam wavelength is changed at one time with respect to the method to change the reference beam wavelength several times to converge the reference beam wavelength to the optimal value, as in the feedback control. Therefore, the reference beam angle on bragg and the reference beam wavelength can be adjusted in short time.
In this embodiment, the case in which the position of the bright line of the reproduction image is detected in the reproduction image processing unit 23 illustrated in
The reproduction image processing unit 23 in
In
In 804, the galvano-mirror 220 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25 and an angle θB on bragg direction in the reference beam incident on the optical information recording medium 1 is set to an angle θBM at which the brightness of the reproduction light is maximized, detected by 802.
In 8052, a position error BE of the bright line of the reproduction image is detected on the basis of an output of the reproduction image processing unit 23.
In 8062, deviation amounts from optimal values of the reference beam angle on bragg and the reference beam wavelength are calculated from the position error BE of the bright line of the reproduction image detected by 8052.
In 807, the galvano-mirror 220 and the light source 201 are controlled according to commands from the controller unit 16 to the reference beam angle control unit 25 and the light source control unit 21 and the reference beam angle on bragg and the reference beam wavelength are set to correct the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength, calculated by 8062.
In 8082, the angle correcting element 219 is controlled according to the command from the controller unit 16 to the reference beam angle control unit 25, the angle on pitch direction is set to correct the deviation ΔθPADJ of the angle on pitch direction, set by 8032, and the adjustment process ends.
By the above process, the reference beam angle on pitch direction, the reference beam angle on bragg direction, and the reference beam wavelength are set in a state in which information can be reproduced.
Next, a method of detecting the bright line position error BE in 8052 and a method of calculating deviation amounts from optimal values of the reference beam angle on bragg and the reference beam wavelength from the bright line position error BE in 8062 will be described.
BE=X0−X1 (Mathematical Formula 3)
At this time, at the point b at which the optimal reference beam angle on bragg is θBO and the optimal reference beam wavelength is λO, the bright line position error BE becomes almost 0. Meanwhile, at the points a and c at which the reference beam angle on bragg and the reference beam wavelength are deviated from the optimal states, the polarity of the bright line position error BE is different according to a deviation direction. In addition, the magnitude of the bright line position error BE corresponds to the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength. From this, the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength and the directions thereof can be detected from the bright line position error BE of the reproduction image.
When the light detector is arranged to rotate around an optical axis, the scanning direction of the brightness scanning line is not orthogonal to the bright line direction at the point b at which the optimal reference beam angle on bragg is θBO and the optimal reference beam wavelength is λO. In this case, the scanning direction of the brightness scanning line may be defined according to a rotation angle around the optical axis, on the basis of the bright line direction of the reproduction image at the point b.
In the above process, because the angle is set to the predetermined angle ΔθPADJ in 8032, only the relation of the bright line position error BE and the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength, corresponding to ΔθPADJ, may be stored and an amount of data to be stored can be decreased. In addition, data of a minimum of two brightness scanning lines is read only when the deviation amounts ΔθBE and ΔλE from the optimal values of the reference beam angle on bragg and the reference beam wavelength are detected and it is not necessary to read data of all scanning lines of the light detector. Therefore, a processing time can be greatly decreased.
The position of the brightness scanning line is not limited to the position of
In addition, an enlargement example of the bright line portion is illustrated in
Instead of using all data of the taken brightness scanning lines, the data may be thinned out and the process may be executed.
In
In this embodiment, the case in which the reproduction image processing unit 23 in
The reproduction image processing unit 23 in
Different from the first and second embodiments, in this embodiment, because it is not necessary to search the reference beam angle on bragg direction, an adjustment time can be shortened by using high-speed image processing technology. In addition, in the case in which a reproduction image is obtained from angle multiple holograms, if the deviation ΔθPE of the angle on pitch direction increases, a plurality of pages may be detected as a plurality of bright lines. Even in this case, the bright lines crossing each other are not detected on the detector in principle. For this reason, if the bright line width Wd of each bright line is detected, the deviation ΔθPE of the angle on pitch direction can be detected.
In this embodiment, the case in which the optical information recording/reproducing device 10 in
In addition, the configuration of the pickup 11 included in the optical information reproducing device 2500 can be realized by removing the beam expander 208, the phase mask 209, the relay lens 210, the PBS prism 211, and the spatial light modulator 212 from the configuration of
If the configuration of the optical information reproducing device 2500 according to this embodiment is used, all the reproduction operations of the operations included in the first, second, third, and fourth embodiments other than the recording operation can be executed. That is, in the device having only the reproduction function, the incidence angle of the reference beam and the wavelength of the reference beam can be adjusted by using the methods according to the first, second, third, and fourth embodiments. If the above configuration is used, a reproduction dedicated device in which the number of components is decreased can be configured. Therefore, the device can be manufactured at a low cost as compared with the configuration illustrated in
In the embodiments described above, when the deviation amounts from the optimal values of the reference beam angle on bragg and the reference beam wavelength are large and the reference beam angle on bragg and the reference beam wavelength cannot be sufficiently adjusted at one time, the adjustment process may be executed two times. In addition, the example of the case in which the angle correcting element 219 is used as the mechanism for correcting the reference beam incidence angle on pitch direction has been described. However, the present invention is not limited thereto and a mechanism for changing the inclination of the pitch direction of the optical information recording medium 1 may be used. In addition, the pickup 11, the cure optical system 13, and the disk rotation angle detecting optical system 14 can be simplified by integrating some optical system configurations or all optical system configurations. In addition, in the reproduction image processing unit 23, the brightness is detected from the output of the light detector 225 to reproduce the page data. However, the present invention is not limited thereto and the reproduction light may be received by a photodiode and a signal corresponding to a total amount of light may be detected.
The present invention is not limited to the embodiments described above and various modifications are included in the present invention. For example, the embodiments are described in detail to facilitate the description of the present invention and are not limited to embodiments in which all of the described configurations are included. In addition, a part of the configurations/processes of the certain embodiment can be replaced by the configurations/processes of another embodiment or the configurations/processes of another embodiment can be added to the configurations/processes of the certain embodiment. In addition, for a part of the configurations/processes of the individual embodiments, other configurations/processes can be added, deleted, and replaced.
In addition, a part or all of the individual configurations, functions, processing units, and processing mechanisms may be designed by integrated circuits and may be realized by hardware. In addition, the individual configurations and functions may be realized by software by analyzing programs for realizing the functions by a CPU and executing the programs by the CPU. Information such as the programs for realizing the individual functions and the data may be stored in a recording device such as a memory, a hard disk, and a solid state drive (SSD).
In addition, only control lines or information lines necessary for explanation are illustrated and the control lines or information lines do not mean all control lines or information lines necessary for a product. In actuality, almost all configurations may be connected to each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-190001 | Sep 2013 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20120008476 | Kuroda et al. | Jan 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 2011018836 | Feb 2011 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20150078149 A1 | Mar 2015 | US |
