WO2012169286A1 - Optical information recording and reproduction device - Google Patents

Optical information recording and reproduction device Download PDF

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Publication number
WO2012169286A1
WO2012169286A1 PCT/JP2012/060542 JP2012060542W WO2012169286A1 WO 2012169286 A1 WO2012169286 A1 WO 2012169286A1 JP 2012060542 W JP2012060542 W JP 2012060542W WO 2012169286 A1 WO2012169286 A1 WO 2012169286A1
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WO
WIPO (PCT)
Prior art keywords
light
recording
phase
signal
recording medium
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PCT/JP2012/060542
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French (fr)
Japanese (ja)
Inventor
秀治 三上
渡辺　康一
Original Assignee
日立コンシューマエレクトロニクス株式会社
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Priority to JP2013519419A priority Critical patent/JP5525657B2/en
Publication of WO2012169286A1 publication Critical patent/WO2012169286A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005—Reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1395—Beam splitters or combiners
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
    • G11B7/013—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track for discrete information, i.e. where each information unit is stored in a distinct discrete location, e.g. digital information formats within a data block or sector
    • G11B2007/0136—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track for discrete information, i.e. where each information unit is stored in a distinct discrete location, e.g. digital information formats within a data block or sector where each location can have more than two values ('multivalue'), for data or prepits

Definitions

  • the present invention relates to a high S / N ratio of a reproduction signal of an optical information recording / reproducing apparatus.
  • Optical discs have reached the limit of the resolution of optical systems as a result of commercialization of blue-ray discs using blue semiconductor lasers and high NA objective lenses.
  • Multi-level recording is a promising method for simultaneously realizing larger capacity and higher data transfer speed.
  • Patent Documents 1 to 6 describe techniques relating to multi-level recording.
  • Patent Documents 1 to 5 enable multilevel recording by providing a medium in which the reflectance of a recording mark continuously changes with respect to the power of the recording light applied to the recording medium.
  • Patent Document 6 provides a method of performing multi-value recording by a reflected light quantity distribution pattern by modulating the length and position of a recording mark in a predetermined cell.
  • JP 2001-184649 A (corresponding to EP 1235210A) JP 58-215735 A (corresponding to GB2122408A) Japanese Patent Laid-Open No. 2-064932 Japanese Patent No. 3559590 JP-A-61-211835 (corresponding to USP471118) Japanese Patent No. 3033864 (corresponding to USP 5555231)
  • Non-Patent Document 1 since reproduction at a high S / N ratio is possible, the multilevel can be easily improved, while two light beams are incident from opposite directions during recording. Therefore, there is a problem that the apparatus configuration is complicated.
  • an object of the present invention is to provide an optical information recording / reproducing apparatus that can easily increase the multivalue level with a simple configuration.
  • a light source a recording medium in which the phase of reflected light is changed by recording while changing the recording light intensity, a control unit for controlling the light emission intensity of the light source, and a light beam from the light source as a first light beam
  • a light splitting means for splitting the second light flux; a light collecting means for condensing the first light flux at a predetermined position on the recording medium; a reflecting means such as a mirror for reflecting the second light flux; and a recording medium.
  • Interference optics that combines the first light beam reflected from the second light beam reflected by the reflecting means and generates three or more types of interference light having different relative phases between the first light beam and the second light beam.
  • the control unit modulates the light emission intensity of the light source in multiple stages, and the first light flux Is recorded on the recording medium as recording light, and information is recorded during playback. It was decided to acquire the phase value of the first light beam reflected from the second recording medium relative to the phase of the light beam in the signal processing unit.
  • the reflected light from the recording medium at the time of reproduction depends on the emission intensity at the time of recording.
  • the phase difference is modulated. That is, the phase of light is recorded as information by modulating the light intensity, and the phase change is acquired at the time of reproduction.
  • a light splitting means for splitting the light into a second light flux, a light collecting means for condensing the first light flux at a predetermined position on the recording medium, a reflecting means such as a mirror for reflecting the second light flux, Phase control means for controlling the relative phase of the second light flux and the second light flux, and the first light flux reflected from the recording medium is combined with the second light flux reflected by the reflection means, and the first light flux and the first light flux are combined.
  • An interference optical system that generates two or more types of interference light having different relative phases between the two light beams, a detector that detects the interference light, and a signal processing unit that generates a reproduction signal from the output of the detector
  • the control unit modulates the light emission intensity of the light source in multiple stages, and the first light flux is used as the recording light.
  • the information is recorded by irradiating on the recording medium, and at the time of reproduction, the phase control means controls the average phase difference between the first light beam and the second light beam to be constant, and the signal processing unit The phase value of the first light beam reflected from the recording medium based on the phase of the second light beam is obtained.
  • the phase value is obtained by using a differential detection signal proportional to the intensity difference between a pair of interference light generated by the interference optical system in the signal processing unit.
  • the signal processing unit obtains the phase value of the first light beam reflected from the recording medium based on the intensity value of the first light beam and the phase of the second light beam.
  • the demodulation is performed based on the intensity value and the phase value.
  • the block diagram which shows one Example of the optical information recording / reproducing apparatus of this invention.
  • the block diagram of the Example which performs closed loop control of the phase difference between signal light and reference light.
  • the block diagram of the Example which performs the closed loop control of a phase difference with a single actuator.
  • the block diagram of the Example which acquires a reproduced signal directly from a differential detection signal.
  • Explanatory drawing of the optical system which acquires three interference lights from which a phase differs 120 degree
  • regenerating a quaternary modulation signal by the intensity change of the interference signal of reflected light and reference light The figure which shows the reproduction signal eye pattern at the time of reproducing
  • FIG. 1 is a schematic cross-sectional view showing an example of a recording medium used in the present invention.
  • the cross-sectional schematic diagram which shows the state after recording of an example of the recording medium used by this invention.
  • FIG. 6 is a schematic plan view showing another example of the recording medium used in the present invention.
  • multi-value information is recorded by irradiating the medium with recording light whose light intensity is subjected to multi-stage modulation, and reproduction is performed by detecting the multi-value information as phase information.
  • a medium suitable for reading information recorded by changing the recording light intensity based on the phase of the reflected light is used as the recording medium.
  • the medium described in Japanese Patent No. 2705330 can be used.
  • This medium includes a substrate 1301 and a recording layer 1302 as shown in the schematic cross-sectional view of FIG. 13A.
  • a cover layer having a refractive index different from that of the recording layer may exist adjacent to the recording layer 1302.
  • the location of the recording pit is different from the location where the recording pit is formed, so the phase change of the reflected light is observed according to the presence or absence of the recording pit.
  • the magnitude of the interface change changes according to the irradiation light intensity at the time of recording. Therefore, by modulating the emission intensity in multiple stages during recording, the phase change that occurs in the recording pits formed according to the respective emission intensity differs, and the phase change during reproduction is modulated in multiple stages. That is, multi-value information recording and reproduction are possible.
  • the recording medium used in the present invention is not limited to the one described above, and any recording medium may be used as long as the phase of the reflected light during reproduction changes according to the light intensity during recording. Therefore, even if the interface is not deformed as described above, for example, a phase change medium similar to that of a conventional optical disk may be used, and a phase difference may be generated in accordance with the phase change.
  • a phase change region 1402 is generated in the recording layer 1401 in the recording medium where light is irradiated. Produces a phase difference. Then, the area of the phase change region is made different according to the light intensity of the recording light.
  • the phase change of the reflected light from the recording medium changes according to the ratio of the area of the phase change area in the area irradiated with light for reproduction, so recording is performed by modulating the light intensity in multiple stages. It is possible to play as.
  • FIG. 1 is a block diagram showing an embodiment of the optical information recording / reproducing apparatus of the present invention.
  • the recording medium described in Japanese Patent No. 2705330 was used.
  • the laser driver 101 gives a modulation signal corresponding to user data sent from the host device 103 to the semiconductor laser 104 in accordance with an instruction from the microprocessor 102.
  • the modulation signal is modulated in four steps, and the emission intensity of the semiconductor laser 104 is modulated in four steps accordingly.
  • the light beam emitted from the semiconductor laser 104 by such modulation passes through the ⁇ / 2 plate 105 and then enters the polarization beam splitter 106.
  • the light beam from the semiconductor laser 104 is vertically polarized light (s-polarized light), and the ⁇ / 2 plate 105 passes the light beam without changing the polarization direction because the optical axis is 0 degrees, that is, the horizontal polarization direction during recording.
  • the polarization beam splitter 106 has the property of reflecting vertically polarized light and transmitting horizontally polarized light (all the polarized beam splitters used in this embodiment have the same property). Reflects light flux.
  • the reflected light beam is converted into parallel light by the first collimating lens 107, and then the relay lens 108 for correcting the spherical aberration and the ⁇ / 4 plate (the optical axis direction is 45 degrees with respect to the horizontal polarization direction) 109.
  • the relay lens 108 for correcting the spherical aberration and the ⁇ / 4 plate (the optical axis direction is 45 degrees with respect to the horizontal polarization direction) 109.
  • the objective lens 111 with NA of 0.85 mounted on the actuator 110
  • data is recorded on the recording medium in accordance with the above four-step modulation.
  • the reflected light from the optical disk 112 follows an optical path opposite to that at the time of irradiation, and passes through the ⁇ / 4 plate 109 in a reciprocating manner, whereby the polarization state is changed to horizontal polarization and is transmitted through the polarization beam splitter 106. Thereafter, the light is incident on a special polarization beam splitter 113 (transmits 50% of the horizontally polarized light and reflects 50% of the light and transmits 100% of the vertically polarized light), and the reflected light passes through the cylindrical lens 114 and is divided into four parts. The light is collected at 115 and detected.
  • a focus error signal and a track error signal are generated from the output signal of the quadrant detector 115 and fed back as a drive current of the actuator 110 via the servo circuit 116.
  • the position of the spot 117 of the light beam condensed by the objective lens 111 is servo-controlled.
  • the astigmatism method is used as the focus servo control
  • the push-pull method is used as the track servo control.
  • Light emitted from the blue semiconductor laser 104 having a wavelength of 405 nm passes through the ⁇ / 2 plate 105.
  • the optical axis direction of the ⁇ / 2 plate 105 is set to 22.5 degrees with respect to the horizontal direction, unlike during recording, and the polarization direction of the light beam is rotated by 45 degrees.
  • the polarized light is split by the polarization beam splitter 106 into a vertically polarized light beam that is reflected and a horizontally polarized light beam that is transmitted. Of these, the reflected light beam is applied to the optical disk 112 in the same manner as during recording.
  • Reflected light from the optical disk 112 (hereinafter referred to as signal light) follows an optical path opposite to that at the time of irradiation, as in recording, and enters the polarization beam splitter 106 in a state of horizontal polarization.
  • the light beam that has passed through the polarizing beam splitter 106 (hereinafter referred to as reference light) is converted into a parallel light beam by the collimator lens 118, and then reflected by the mirror 119 in the opposite direction. , 45 degrees with respect to the horizontal polarization direction), the polarization direction becomes vertical polarization by reciprocating, and enters the polarization beam splitter 106 again.
  • both the signal light and the reference light are emitted from the polarization beam splitter 106 in the direction in which the special polarization beam splitter 113 is disposed, the signal light and the reference light are combined in a state where the polarizations are orthogonal to each other.
  • This combined light beam enters the special polarization beam splitter 113, and only the horizontal polarization component, which is a signal light component, is reflected at a rate of 50% as in the recording, and the rest is transmitted. This reflected light is detected by the quadrant detector 115 as in the recording, and the position of the actuator 110 is controlled by the detection signal.
  • the transmitted light beam from the special polarization beam splitter 113 is divided into two by the non-polarization half beam splitter 121 into transmitted light and reflected light.
  • the transmitted light passes through a ⁇ / 2 plate 122 whose optical axis is set to 22.5 degrees with respect to the horizontal direction, and the polarization is rotated by 45 degrees, and is separated into a p-polarized component and an s-polarized component by the Wollaston prism 123.
  • the separated light beams respectively incident on the photodiode 125 and 126 of the differential detector 124, an electrical signal D 1 that is proportional to the difference in intensity is output from the differential detector 124.
  • the light beam reflected by the non-polarization half-beam splitter 121 passes through a ⁇ / 4 plate 127 whose optical axis is set to 45 degrees with respect to the horizontal direction, and then is p-polarized component and s-polarized component by the Wollaston prism 128. Separated. The separated light beams respectively incident on the photodiode 130, 131 of the differential detector 129, an electrical signal D 2 that is proportional to the difference in intensity is output from the differential detector 129.
  • the light beams after being separated by the Wollaston prisms 123 and 128 are both interference light in which the reproduction light and the reproduction reference light interfere with each other, and the outputs of the differential detectors 124 and 129 are interference components. Is extracted.
  • the outputs of the differential detectors 124 and 129 are sent to the digital signal processing circuit 140, and the phase value recorded here is obtained as a reproduction signal.
  • the obtained phase value is demodulated by the demodulating circuit 141, then sent to the decoding circuit 142, converted into user data, and sent to the host device 103 through the microprocessor 102.
  • the principle of reproducing the phase value by generating the interference light by the operation at the time of reproduction described above will be described. Since the light beam incident on the non-polarization half beam splitter 121 includes reproduction light as a p-polarization component and reproduction reference light as an s-polarization component, this polarization state is represented by a Jones vector.
  • E s is the electric field of the signal light, which is the electric field of E r reference light.
  • the first component of this vector represents p-polarized light, and the second component represents s-polarized light. After this light beam passes through the non-polarization half beam splitter 121 and passes through the ⁇ / 2 plate 122, the Jones vector is
  • the signal light and the reference light are superimposed, that is, interference light.
  • the signal light and the reference light are superimposed, that is, interference light.
  • the first term and the second term represent the intensity components of the signal light and the reference light, respectively, and the third term represents the interference between the signal light and the reference light.
  • ⁇ is the phase of the signal light based on the phase of the reference light, which is a modulated signal to be reproduced. Since the outputs of the differential detectors 124 and 129 are proportional to the difference in the intensity of these branched lights,
  • the output is proportional to the term representing the interference.
  • the conversion efficiency of the detector was omitted.
  • the outputs of the differential detectors 124 and 129 are first A / D converted in the digital signal processing circuit 140 and then input to the arithmetic circuit, and the following arithmetic result is output.
  • the phase value of the signal light can be obtained by generating the interference light of the signal light and the reference light and detecting the interference light. It is also possible to obtain a signal proportional to the square root of the intensity value of the signal light by another calculation.
  • the signal is proportional to the intensity value of the signal light.
  • the phase value is estimated from the intensity of the four interference lights, but the parameters that determine the interference light intensity are (1) signal light intensity, (2) reference light intensity, and (3) signal light and reference light.
  • the phase value can be estimated by detecting the interference light intensities of three different phases.
  • the signal light intensity can be estimated. For example, as shown in FIG. 5, the combined light flux of the signal light and the reference light is divided into three by non-polarizing beam splitters 501 and 502, and one of the light fluxes is s-polarized with respect to p-polarized light.
  • Another light beam passes through the phase plate 504 that produces a phase difference of 120 degrees with respect to the p-polarized light, and another light beam passes only the 45-degree polarized light in all three light beams.
  • polarizers 505, 506, and 507 are transmitted through polarizers 505, 506, and 507, and detected by detectors 508, 509, and 510.
  • the outputs D 1 , D 2 , D 3 of these detectors are respectively
  • phase value can be estimated by performing the following calculation.
  • the intensity can be estimated by the following calculation.
  • the above has described an example of detecting the interference light intensity of three different phases.
  • the phase and polarization by adjusting the phase and polarization, the number of three or more phases such as four and five is adjusted.
  • the interference light intensity can be detected.
  • the differential detector is a current in which the difference in photocurrent due to the branched light incident on the two photodiodes 125 and 126 is converted from current to voltage by the transimpedance amplifier 601. It has a differential configuration. With this configuration, even when the intensity of the reproduction reference light is increased in order to obtain a sufficient output level, the photocurrent due to the intensity of the reproduction reference light itself is canceled by the two photodiodes, so that the transimpedance amplifier Therefore, a sufficient output signal level can be obtained, and the relative magnitude of amplifier noise can be effectively suppressed.
  • the differential detector since one transimpedance corresponds to two photodiodes, four outputs obtained by current-voltage conversion of the photocurrent of the photodiode with the transimpedance are used as in a normal detector.
  • the detector noise can be reduced by 3 dB compared to the calculation, and this point is also effective in suppressing the amplifier noise.
  • Non-Patent Document 1 In the method described in Non-Patent Document 1, a high S / N ratio can be obtained in principle for the same reason.
  • the method of Non-Patent Document 1 needs to collect two light beams at the same location on the recording medium during data recording. Therefore, the positioning control mechanism is complicated, and high positioning accuracy is required, so that it is difficult to accurately perform the recording operation. For this reason, the signal level fluctuates during recording, and as a result, the S / N ratio during reproduction can deteriorate.
  • the recording operation may be performed by condensing a single light beam on the recording medium and controlling the light emission intensity, as in the conventional optical disk apparatus. For this reason, the positioning accuracy required for the focused spot is comparable to that of the conventional optical disc, and the configuration is simple.
  • the present embodiment can improve the S / N ratio with a simpler configuration than the prior art. Therefore, the multivalue level can be easily increased, and the recording density and the data transfer speed can be improved. Can do.
  • Japanese Patent No. 4564948 the interference light of the signal light and the reference light is detected with a configuration similar to that of the present embodiment. However, the intensity signal is acquired in the same manner as the conventional optical disc, and the S / N ratio is improved. Since the effect is limited only to the relative reduction of the detection noise, the present embodiment that is not affected by the laser noise can obtain a higher S / N ratio.
  • a reproduction signal eye pattern was simulated.
  • the recording medium shown in Japanese Patent No. 2705330 assumes that the interface of the recording layer is deformed in accordance with the light intensity at the time of recording. Tried to record. That is, a recording medium in which recording pits whose interface of the recording layer is deformed into four sizes according to the recording intensity is arranged in a line is handled.
  • the magnitude of each noise component described above was the same as that of the current optical disc apparatus.
  • the wavelength of the light source for both recording and reproduction was 405 nm, and the NA of the objective lens when condensing light on the recording medium was 0.85.
  • FIG. 7A shows a reproduction signal eye pattern in the case of a reproduction method for detecting a reproduction signal. In this case, it is difficult to identify quaternary modulation due to insufficient S / N ratio.
  • FIG. 7B shows a reproduction signal eye pattern when reproduction is performed by the method of Japanese Patent No. 4564948.
  • the intensity modulated signal amplified by the calculation of Expression (15) instead of Expression (14) are reproduced.
  • the S / N ratio is improved as compared with FIG. 7A by suppressing the relative magnitude of the amplifier noise as described above, an error still occurs in the discrimination of the quaternary level.
  • FIG. 7C shows a reproduction signal eye pattern when reproduction is performed by the method of this embodiment.
  • the S / N ratio is clearly improved compared to the above two cases, and the quaternary level can be easily identified. As described above, this can be explained as not being affected by laser noise when the phase of the reflected light is reproduced.
  • ⁇ s is a phase due to signal modulation
  • ⁇ r is a phase difference corresponding to an optical path length difference (excluding phase modulation) between the signal light and the reference light.
  • ⁇ r is mainly generated by the surface blur of the recording medium (shift in the optical axis direction, on the order of 100 ⁇ m). These change with time.
  • the surface blur speed is about several tens of kHz to several hundreds of kHz
  • data is written at several tens of MHz to several hundreds of MHz
  • ⁇ r is substantially constant at adjacent writing positions (symbols). is there. Therefore by outputting the difference between the adjacent symbols as decoded signals, it is possible to reproduce the signal without undergoing effects of unnecessary phase component phi r above.
  • the reference light is reflected by the mirror 119 in the opposite direction and combined with the signal light.
  • the method of combining is not limited to this, and another reflecting means may be used.
  • the reference light may be reflected twice by the right-angle prism 143 and combined with the signal light by the polarization beam splitter 146.
  • a ⁇ / 2 plate 144 is inserted instead of the ⁇ / 4 plate 120, and the polarization of the reference light is rotated by 90 degrees.
  • a retroreflector and a corner cube prism may be used instead of the right-angle prism 143 in the configuration of FIG.
  • FIG. 2 shows a configuration diagram of an optical information recording / reproducing apparatus according to the present embodiment.
  • the operation during recording is the same as in the first embodiment.
  • the signal light is detected in the same manner as in the first embodiment.
  • the reference light passes through the ⁇ / 4 plate 120, is reflected by the mirror 202 mounted on the piezo element 201, and then is reflected in the opposite direction by the mirror 119 mounted on the actuator 203. After that, the signal light is combined and detected in the same manner as in the first embodiment.
  • the same error signal as that of the actuator 110 is input to the actuator 203 and the same amount of displacement as that of the actuator 110 is performed.
  • the output of the differential detector 124 is not only input to the signal processing circuit 140 as in the first embodiment, but also enters the servo circuit 204 to extract a low frequency component (a component from which the signal modulation component is removed). Then, the amplified voltage signal is fed back as a drive voltage of the piezo element 201 as a phase error signal. As a result, the mirror 202 is displaced, and the closed loop control is performed so that the average phase of the signal light (relative to the reference light) becomes constant.
  • the optical path lengths of the signal light and the reference light are adjusted to the same level by the displacement of the actuator 203 due to the error signal.
  • this adjustment accuracy is on the order of several ⁇ m, and the phase difference between the signal light and the reference light (when the signal modulation component is averaged) still varies.
  • the phase difference is fixed. This is explained as follows. Since the modulated signal light is phase-modulated, if it is not intensity-modulated, the electric field of the modulated light is arranged concentrically as shown in FIG. 8A on the complex plane, The average value (that is, the low frequency component excluding the signal modulation component) also has a predetermined value.
  • the output of the differential detector 124 can be regarded as a real component of these electric fields. Then, the real part component of the average electric field becomes zero as shown in FIG. 8B by performing the closed loop control using the low frequency component as an error signal so that the output becomes zero. In this way, the phase value error ⁇ r due to the surface blur of the optical disc 112 can be kept at zero, the surface blur is large, and ⁇ r has a size that cannot be completely removed by differential encoding. It is also possible to acquire the phase signal stably.
  • the signal processing circuit 140, the demodulation circuit 141, and the decoding circuit 142 are the same as those in the first embodiment. However, the demodulation circuit 141 can be simplified by omitting the differential encoding.
  • the recording pattern needs to have a recording pattern in which the average electric field has a predetermined value other than zero as the recording operation.
  • the combination of the actuator 203 and the piezo element 201 is configured to suppress the phase error ⁇ r to zero.
  • this ensures an adjustment range corresponding to the size of the surface blur by the actuator, and the piezo element has a phase difference.
  • the aim is to ensure the accuracy of maintaining a stable state. With such a configuration, it is not necessary to increase the performance required for each of the actuator and the piezo element, which can be easily realized.
  • the configuration can be simplified as shown in FIG.
  • the reference light is reflected in the opposite direction by the mirror 119 mounted on the actuator 203, and the position of the actuator 203 is closed-loop controlled using an error signal generated from the servo circuit 204.
  • the phase error ⁇ r can be kept at zero.
  • the form for controlling the phase value is not limited to this, and for example, a wedge-shaped prism pair shown in FIG. 9 may be inserted instead of the piezo element 201.
  • the phase value can be adjusted by controlling the insertion amount of one of the wedge prisms 901 and 902 (the direction perpendicular to the incident optical axis, the direction of the arrow in the figure) with an actuator. Therefore, the wedge-shaped prism 901 is mounted on the actuator, and an error signal is input to the actuator, whereby the phase value can be closed-loop controlled.
  • a configuration using a right-angle prism, a corner cube prism, a retroreflector, or the like instead of the mirror 119 may be used.
  • the reproduction signal is directly acquired without performing the arithmetic processing for obtaining the phase value from the output of the differential detector.
  • FIG. 4 shows a configuration diagram of an optical information recording / reproducing apparatus according to the present embodiment.
  • the differential detection signal is only an output from the differential detector 124, and components such as the non-polarization half beam splitter 121 are omitted as compared with the first and second embodiments.
  • the phase of the signal light is closed-loop controlled using the output signal of the differential detector 124.
  • the phase value calculation performed in the first and second embodiments is not performed, and the output signal of the differential detector 124 is A / D converted and output as it is, and the demodulation circuit 141 outputs the modulation level. A determination is made. Note that differential encoding is not performed.
  • each electric field of the signal light modulated by controlling the phase value is fixed in a state as shown in FIG.
  • the output from the differential detector 124 is a real part component of these electric fields as described in the second embodiment
  • four levels of modulation signals corresponding to the four electric fields are output from the differential detector 124. Observed at the output. Therefore, data can be demodulated by performing the determination of four levels without calculating the phase value as in the first and second embodiments.
  • the recording pattern needs to have a recording pattern in which the average electric field has a predetermined value other than zero as an operation during recording.
  • the phase value is not directly calculated.
  • the obtained reproduction signal is nothing but an observation of the real part component accompanying the phase change of the signal light. It can be said that the phase modulation of the signal light is observed.
  • decoding is performed not only by the phase value of the signal light obtained from the output of the differential detector but also by a combination with the intensity value.
  • the configuration of the optical information recording / reproducing apparatus according to the present embodiment is basically as shown in FIG.
  • the digital signal processing circuit 140 outputs not only the phase value of the signal light but also the intensity value from the values of the differential detection signals D 1 and D 2 as shown in the block diagram of FIG.
  • Each of these phase values and intensity values is subjected to level determination in the subsequent decoding circuit, and the levels are identified based on these results.
  • a clear correlation occurs between the phase value and the intensity value in the signal light during reproduction. Therefore, by performing such level determination, it is possible to improve the accuracy of determination compared to the case of performing level determination of only the phase value, and it is possible to reproduce data more accurately.
  • the light intensity or phase does not appear in an explicit form, but the phase value of the signal light (corresponding to the declination on the complex plane) and intensity (complex Demodulation is performed using both information on the absolute value on the plane, that is, corresponding to the distance from the origin), and it is possible to determine the level with higher accuracy than the demodulation based on the phase value alone.
  • the present embodiment can be realized with the configuration of FIG. 1 similar to that of the first embodiment by applying the differential encoding to omit the phase control mechanism including the piezo element 201 and the actuator 203. Also in this case, the demodulation circuit 141 performs demodulation based on the phase value and intensity value of the signal light. In this case, the differential encoding may be performed only on the phase value, and it is not always necessary to perform on the intensity value that is not accompanied by the fluctuation of the value due to the surface shake of the optical disk 112.
  • this invention is not limited to the above-mentioned Example, Various modifications are included.
  • 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.
  • 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.
  • the present invention makes it possible to provide an optical information recording / reproducing apparatus having both a large capacity and a high transfer speed, and a wide range of industrial applications such as a large capacity video recorder, a hard disk data backup device, and a stored information archive device can be expected.

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Abstract

Provided is an optical information recording and reproduction device capable of easily increasing the number of levels with a simple configuration. Data is recorded by modulating the emission intensity of a light source at multiple levels, and the phase of light reflected from a recording medium is detected at the time of reproduction.

Description

光情報記録再生装置Optical information recording / reproducing device
　本発明は、光情報記録再生装置の再生信号の高Ｓ／Ｎ化に関する。 The present invention relates to a high S / N ratio of a reproduction signal of an optical information recording / reproducing apparatus.
　光ディスクは、青色半導体レーザと、高ＮＡ対物レンズを用いるブルーレイディスクの製品化に至って、光学系の分解能としてはほぼ限界に達している。更なる大容量化とデータ転送速度の高速化を同時に実現する方法としては、多値記録が有力である。多値記録に関する技術は、例えば特許文献１～６に述べられている。 Optical discs have reached the limit of the resolution of optical systems as a result of commercialization of blue-ray discs using blue semiconductor lasers and high NA objective lenses. Multi-level recording is a promising method for simultaneously realizing larger capacity and higher data transfer speed. For example, Patent Documents 1 to 6 describe techniques relating to multi-level recording.
　特許文献１～５は、記録媒体へ照射される記録光のパワーに対して記録マークの反射率が連続的に変化する媒体を提供することにより、多値レベルでの記録を可能にしている。特許文献６は、所定のセル内における記録マークの長さと位置を変調することにより、反射光量分布のパターンによる多値記録を行う方式を提供している。 Patent Documents 1 to 5 enable multilevel recording by providing a medium in which the reflectance of a recording mark continuously changes with respect to the power of the recording light applied to the recording medium. Patent Document 6 provides a method of performing multi-value recording by a reflected light quantity distribution pattern by modulating the length and position of a recording mark in a predetermined cell.
　別の多値記録の方法として、対向する２つの光を同一箇所に集光することで、集光点付近での２つの光の干渉縞（定在波）を記録する方法が検討されている（非特許文献１参照）。この方式では、記録時に２つの光の一方の位相を変調し、光の干渉縞の位相として情報を記録する。本方式により、高いＳ／Ｎ比での再生信号取得が可能となり、多値レベルを容易に識別することが可能である。 As another multi-value recording method, a method of recording interference fringes (standing waves) of two lights near the condensing point by condensing two opposing lights at the same location has been studied. (Refer nonpatent literature 1). In this system, one phase of two lights is modulated at the time of recording, and information is recorded as a phase of light interference fringes. With this method, it is possible to acquire a reproduction signal with a high S / N ratio, and it is possible to easily identify a multilevel level.
特開２００１－１８４６４９号公報（ＥＰ１２３５２１０Ａに対応）JP 2001-184649 A (corresponding to EP 1235210A) 特開昭５８－２１５７３５号公報（ＧＢ２１２２４０８Ａに対応）JP 58-215735 A (corresponding to GB2122408A) 特開平２－０６４９３２号公報Japanese Patent Laid-Open No. 2-064932 特許第３５５９５９０号Japanese Patent No. 3559590 特開昭６１－２１１８３５号公報（ＵＳＰ４７１１８１５に対応）JP-A-61-211835 (corresponding to USP471118) 特許第３０３３８６４号（ＵＳＰ５５５５２３１に対応）Japanese Patent No. 3033864 (corresponding to USP 5555231)
　上記特許文献１～５においては、反射光量レベルの大きさによって多値データを判別するが、これは、通常の光ディスクのように２値レベルで記録、再生する場合に比べて判別すべきレベルの差が近接し、実質的に信号レベルが低下するのと同じ状況になる。すなわち、多値度（多値レベルの数）に比例して信号のＳ／Ｎ比が低下するため、大幅な多値化は実質的に困難であるという本質的な問題がある。特許文献６においても、多数の検出器を用いて信号光を検出するため、各検出器当たりの光量が低下し、上記と同様にＳ／Ｎ比の不足によって多値度を大幅に増やすのは困難である。更に、多数の検出器と、それらの出力に対する複雑な信号処理が必要になることから、装置の複雑化、高コスト化が課題である。 In the above Patent Documents 1 to 5, multi-value data is discriminated based on the magnitude of the amount of reflected light. This is a level that should be discriminated compared to the case of recording and reproducing at a binary level as in an ordinary optical disc. The situation is the same as the difference is close and the signal level is substantially reduced. That is, since the S / N ratio of the signal decreases in proportion to the multi-value level (number of multi-value levels), there is an essential problem that a large multi-value is practically difficult. Also in Patent Document 6, since signal light is detected using a large number of detectors, the amount of light per detector is reduced, and the multi-level is greatly increased due to a lack of S / N ratio as described above. Have difficulty. Furthermore, since a large number of detectors and complicated signal processing for their outputs are required, the complexity and cost of the apparatus are problems.
　非特許文献１の方法では、高いＳ／Ｎ比での再生が可能であるために多値度を容易に向上できる一方で、記録時に２つの光を対向方向から入射するという、従来の光ディスク装置と大きく異なる構成を要するため、装置構成が複雑になるという課題を有する。 In the method of Non-Patent Document 1, since reproduction at a high S / N ratio is possible, the multilevel can be easily improved, while two light beams are incident from opposite directions during recording. Therefore, there is a problem that the apparatus configuration is complicated.
　上記課題に鑑み、本発明の目的は、簡素な構成で多値度を高めることが容易な、光情報記録再生装置を提供することである。 In view of the above problems, an object of the present invention is to provide an optical information recording / reproducing apparatus that can easily increase the multivalue level with a simple configuration.
　本発明の目的を達成するために以下の手段を用いた。 In order to achieve the object of the present invention, the following means were used.
（１）光源と、記録光強度を変化させて記録することにより反射光の位相に変化が生じる記録媒体と、光源の発光強度を制御する制御部と、光源からの光束を第一の光束と第二の光束とに分割する光分割手段と、第一の光束を記録媒体上の所定の位置に集光する集光手段と、第二の光束を反射させるミラー等の反射手段と、記録媒体から反射された第一の光束を反射手段によって反射された第二の光束と合波し、第一の光束と第二の光束間の相対位相が異なる３種類以上の干渉光を生成する干渉光学系と、干渉光を検出する検出器と、検出器の出力から再生信号を生成する信号処理部と、を有し、記録時には、制御部により光源の発光強度を多段に変調し第一の光束を記録光として記録媒体上に照射することで情報の記録を行い、再生時には、信号処理部において第二の光束の位相を基準とした記録媒体から反射された第一の光束の位相値を取得することとした。 (1) A light source, a recording medium in which the phase of reflected light is changed by recording while changing the recording light intensity, a control unit for controlling the light emission intensity of the light source, and a light beam from the light source as a first light beam A light splitting means for splitting the second light flux; a light collecting means for condensing the first light flux at a predetermined position on the recording medium; a reflecting means such as a mirror for reflecting the second light flux; and a recording medium. Interference optics that combines the first light beam reflected from the second light beam reflected by the reflecting means and generates three or more types of interference light having different relative phases between the first light beam and the second light beam. System, a detector for detecting interference light, and a signal processing unit for generating a reproduction signal from the output of the detector. During recording, the control unit modulates the light emission intensity of the light source in multiple stages, and the first light flux Is recorded on the recording medium as recording light, and information is recorded during playback. It was decided to acquire the phase value of the first light beam reflected from the second recording medium relative to the phase of the light beam in the signal processing unit.
　ここで、記録媒体として記録光強度を変化させて記録することにより反射光の位相に変化が生じる記録媒体を用いるため、記録時の発光強度に応じて、再生時の記録媒体からの反射光の位相差が変調される。すなわち、光強度の変調により光の位相を情報として記録することを行い、その位相変化を再生時に取得する。 Here, since a recording medium in which the phase of the reflected light is changed by recording with changing the recording light intensity is used as the recording medium, the reflected light from the recording medium at the time of reproduction depends on the emission intensity at the time of recording. The phase difference is modulated. That is, the phase of light is recorded as information by modulating the light intensity, and the phase change is acquired at the time of reproduction.
　このような構成とすることで、従来よりも簡素な構成で高いＳ／Ｎ比でのデータの記録・再生が可能となり、容易に多値レベルを向上させることができる。 By adopting such a configuration, it becomes possible to record / reproduce data with a higher S / N ratio with a simpler configuration than before, and the multi-level can be easily improved.
（２）光源と、記録光強度を変化させて記録することにより反射光の位相に変化が生じる記録媒体と、光源の発光強度を制御する制御部と、光源からの光束を第一の光束と第二の光束とに分割する光分割手段と、第一の光束を記録媒体上の所定の位置に集光する集光手段と、第二の光束を反射させるミラー等の反射手段と、第一の光束と第二の光束の相対位相を制御する位相制御手段と、記録媒体から反射された第一の光束を反射手段によって反射された第二の光束と合波し、第一の光束と第二の光束間の相対位相が異なる２種類以上の干渉光を生成する干渉光学系と、干渉光を検出する検出器と、検出器の出力から再生信号を生成する信号処理部と、を有し、記録時には、制御部により光源の発光強度を多段に変調し第一の光束を記録光として記録媒体上に照射することで情報の記録を行い、再生時には、位相制御手段により第一の光束と第二の光束の平均的な位相差が一定になるように制御し、信号処理部において第二の光束の位相を基準とした記録媒体から反射された第一の光束の位相値を取得することとした。 (2) a light source, a recording medium in which the phase of the reflected light is changed by recording while changing the recording light intensity, a control unit for controlling the light emission intensity of the light source, and a light beam from the light source as a first light beam. A light splitting means for splitting the light into a second light flux, a light collecting means for condensing the first light flux at a predetermined position on the recording medium, a reflecting means such as a mirror for reflecting the second light flux, Phase control means for controlling the relative phase of the second light flux and the second light flux, and the first light flux reflected from the recording medium is combined with the second light flux reflected by the reflection means, and the first light flux and the first light flux are combined. An interference optical system that generates two or more types of interference light having different relative phases between the two light beams, a detector that detects the interference light, and a signal processing unit that generates a reproduction signal from the output of the detector During recording, the control unit modulates the light emission intensity of the light source in multiple stages, and the first light flux is used as the recording light. The information is recorded by irradiating on the recording medium, and at the time of reproduction, the phase control means controls the average phase difference between the first light beam and the second light beam to be constant, and the signal processing unit The phase value of the first light beam reflected from the recording medium based on the phase of the second light beam is obtained.
　このような構成とすることで、従来よりも簡素な構成のまま記録媒体の面ぶれが大きい場合にも安定して位相値の取得が可能となり、高精度な記録・再生動作が可能となる。 By adopting such a configuration, it is possible to stably acquire a phase value even when the recording medium has a large surface shake while maintaining a simpler configuration than before, and a highly accurate recording / reproducing operation is possible.
（３）（２）において、干渉光学系で生成される干渉光は２種類とした。 (3) In (2), there are two types of interference light generated by the interference optical system.
　これにより、より簡素な構成で高いＳ／Ｎ比でのデータの記録・再生が可能となる。 This makes it possible to record / reproduce data at a high S / N ratio with a simpler configuration.
（４）（１）もしくは（２）において、信号処理部において干渉光学系で生成される干渉光の対の強度差に比例する差動検出信号を用いて位相値を取得することとした。 (4) In (1) or (2), the phase value is obtained by using a differential detection signal proportional to the intensity difference between a pair of interference light generated by the interference optical system in the signal processing unit.
　これにより、簡素な信号処理過程により高いＳ／Ｎ比でのデータの記録・再生を行うことができ、装置の簡素化と低コスト化に寄与することができる。 Thereby, data can be recorded / reproduced at a high S / N ratio by a simple signal processing process, which can contribute to simplification and cost reduction of the apparatus.
（５）（１）もしくは（２）において、信号処理部において、第一の光束の強度値と第二の光束の位相を基準とした記録媒体から反射された第一の光束の位相値を取得し、その強度値と位相値に基づき復調を行うこととした。 (5) In (1) or (2), the signal processing unit obtains the phase value of the first light beam reflected from the recording medium based on the intensity value of the first light beam and the phase of the second light beam. The demodulation is performed based on the intensity value and the phase value.
　これにより、簡素な構成を維持したまま、より高精度にデータの記録・再生を行うことが可能となり、多値レベルの向上によりデータ記録密度とデータ転送速度の向上に寄与することができる。 This makes it possible to record / reproduce data with higher accuracy while maintaining a simple configuration, and contribute to the improvement of data recording density and data transfer speed by improving the multi-level.
　本発明によると、記録レベルの多値度を高めることが容易で、簡素な構成で実現可能な、光情報記録再生装置を提供することができる。 According to the present invention, it is possible to provide an optical information recording / reproducing apparatus that can easily increase the multilevel of the recording level and can be realized with a simple configuration.
　上記した以外の、課題、構成及び効果は、以下の実施形態の説明により明らかにされる。 Issues, configurations, and effects other than those described above will be clarified by the following description of the embodiments.
本発明の光情報記録再生装置の一実施例を示すブロック図。The block diagram which shows one Example of the optical information recording / reproducing apparatus of this invention. 信号光と参照光の間の位相差を閉ループ制御する実施例の構成図。The block diagram of the Example which performs closed loop control of the phase difference between signal light and reference light. 単一のアクチュエータで位相差の閉ループ制御をする実施例の構成図。The block diagram of the Example which performs the closed loop control of a phase difference with a single actuator. 差動検出信号から直接再生信号を取得する実施例の構成図。The block diagram of the Example which acquires a reproduced signal directly from a differential detection signal. １２０度ずつ位相の異なる３つの干渉光を取得する光学系の説明図。Explanatory drawing of the optical system which acquires three interference lights from which a phase differs 120 degree | times. 差動検出器の詳細構成図。The detailed block diagram of a differential detector. ４値変調信号を反射光の強度変化によって再生した場合の再生信号アイパターンを示す図。The figure which shows the reproduction signal eye pattern at the time of reproducing | regenerating a quaternary modulation signal by the intensity change of reflected light. ４値変調信号を反射光と参照光の干渉信号の強度変化によって再生した場合の再生信号アイパターンを示す図。The figure which shows the reproduction signal eye pattern at the time of reproducing | regenerating a quaternary modulation signal by the intensity change of the interference signal of reflected light and reference light. ４値変調信号を反射光と参照光の干渉信号の位相変化によって再生した場合の再生信号アイパターンを示す図。The figure which shows the reproduction signal eye pattern at the time of reproducing | regenerating a quaternary modulation signal by the phase change of the interference signal of reflected light and reference light. 位相閉ループ制御の原理を説明する図。The figure explaining the principle of phase closed loop control. 位相閉ループ制御の原理を説明する図。The figure explaining the principle of phase closed loop control. 楔形プリズムによる位相調整を行う場合の構成図。The block diagram in the case of performing phase adjustment with a wedge-shaped prism. 差動検出信号から直接再生信号を取得する原理を説明する図。The figure explaining the principle which acquires a reproduction signal directly from a differential detection signal. 差動検出信号から信号光の位相と強度を出力する場合のデジタル信号処理回路のブロック図。The block diagram of a digital signal processing circuit in the case of outputting the phase and intensity of signal light from a differential detection signal. ２つの差動検出信号から変調信号が取得されることを説明する図。The figure explaining that a modulation signal is acquired from two differential detection signals. 本発明で用いる記録媒体の一例を示す断面模式図。1 is a schematic cross-sectional view showing an example of a recording medium used in the present invention. 本発明で用いる記録媒体の一例の記録後の状態を示す断面模式図。The cross-sectional schematic diagram which shows the state after recording of an example of the recording medium used by this invention. 本発明で用いる記録媒体の他の例を示す平面模式図。FIG. 6 is a schematic plan view showing another example of the recording medium used in the present invention. 参照光の反射手段として直角プリズムを用いた実施形態の構成図。The block diagram of embodiment using the right-angle prism as a reflection means of reference light.
　本発明では、媒体に光強度を多段変調した記録光を照射することによって多値情報を記録し、その多値情報を位相情報として検出することにより再生する。 In the present invention, multi-value information is recorded by irradiating the medium with recording light whose light intensity is subjected to multi-stage modulation, and reproduction is performed by detecting the multi-value information as phase information.
　最初に、本発明の記録・再生の原理について説明する。本発明では、記録媒体として、記録光強度を変化させて記録した情報を反射光の位相をもとに読み出すのに適した媒体を用いる。一例として、特許第２７０５３３０号に記載された媒体を用いることができる。この媒体は、図１３Ａの断面模式図に示すように、基板１３０１と記録層１３０２からなる。なお、記録層１３０２に隣接して、記録層と屈折率の異なるカバー層が存在していても構わない。媒体への光照射により、図１３Ｂに示すように、記録層１３０２が膨張して記録層の界面１３０３が変形を引き起こし、記録ピットを形成する。ここで低パワーの光を記録後の媒体に照射すると、記録ピットが形成されている場所はそうでない場所に比べて界面の位置が異なるため、記録ピットの有無に従って反射光の位相変化が観測される。すなわち、光照射によってデータ記録を行い、記録されたデータを記録媒体からの反射光の位相変化として取得することが可能である。ここで、当然のことながら、記録時の照射光強度に応じて上記の界面変化の大きさは変化する。したがって、記録時に発光強度を多段に変調することにより、それぞれの発光強度に応じて形成された記録ピットで生じる位相変化は異なり、再生時の位相変化が多段に変調される。すなわち、多値の情報記録、再生が可能である。 First, the recording / reproducing principle of the present invention will be described. In the present invention, a medium suitable for reading information recorded by changing the recording light intensity based on the phase of the reflected light is used as the recording medium. As an example, the medium described in Japanese Patent No. 2705330 can be used. This medium includes a substrate 1301 and a recording layer 1302 as shown in the schematic cross-sectional view of FIG. 13A. Note that a cover layer having a refractive index different from that of the recording layer may exist adjacent to the recording layer 1302. By irradiating the medium with light, as shown in FIG. 13B, the recording layer 1302 expands and the interface 1303 of the recording layer is deformed to form recording pits. Here, if the medium after recording is irradiated with low-power light, the location of the recording pit is different from the location where the recording pit is formed, so the phase change of the reflected light is observed according to the presence or absence of the recording pit. The That is, it is possible to perform data recording by light irradiation and acquire the recorded data as a phase change of reflected light from the recording medium. Here, as a matter of course, the magnitude of the interface change changes according to the irradiation light intensity at the time of recording. Therefore, by modulating the emission intensity in multiple stages during recording, the phase change that occurs in the recording pits formed according to the respective emission intensity differs, and the phase change during reproduction is modulated in multiple stages. That is, multi-value information recording and reproduction are possible.
　なお、本発明に用いる記録媒体としては上に述べたものに限られず、記録時の光強度に応じて再生時の反射光の位相が変化するものであればよい。従って、上述のような界面の変形を伴わずとも、例えば従来の光ディスクと同様な相変化媒体で、相変化に伴って位相差を生じるものであっても構わない。この場合、図１４の平面模式図に示すごとく、記録媒体中の記録層１４０１の、光が照射される箇所に相変化領域１４０２が生じ、この相変化が生じる領域と生じない領域とで反射光に位相差が生じる。そして記録光の光強度に応じて相変化領域の面積を異ならしめる。記録媒体からの反射光の位相変化は、再生のために光が照射される領域における相変化領域の面積の割合に応じて変化するため、光強度を多段に変調して記録を行い、位相変化として再生することが可能である。 The recording medium used in the present invention is not limited to the one described above, and any recording medium may be used as long as the phase of the reflected light during reproduction changes according to the light intensity during recording. Therefore, even if the interface is not deformed as described above, for example, a phase change medium similar to that of a conventional optical disk may be used, and a phase difference may be generated in accordance with the phase change. In this case, as shown in the schematic plan view of FIG. 14, a phase change region 1402 is generated in the recording layer 1401 in the recording medium where light is irradiated. Produces a phase difference. Then, the area of the phase change region is made different according to the light intensity of the recording light. The phase change of the reflected light from the recording medium changes according to the ratio of the area of the phase change area in the area irradiated with light for reproduction, so recording is performed by modulating the light intensity in multiple stages. It is possible to play as.
　以下、図面を参照して本発明の実施の形態を説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[実施例１]
　図１は、本発明の光情報記録再生装置の一実施例を示すブロック図である。本実施例では記録媒体として特許第２７０５３３０号に記載のものを用いた。 [Example 1]
FIG. 1 is a block diagram showing an embodiment of the optical information recording / reproducing apparatus of the present invention. In this embodiment, the recording medium described in Japanese Patent No. 2705330 was used.
　まず、記録時の動作について説明する。レーザドライバ１０１は、マイクロプロセッサ１０２の指示により、上位装置１０３から送られてくるユーザデータに対応した変調信号を半導体レーザ１０４に与える。ここでデータは一例として４値で記録されるため、変調信号は４段階に変調され、これに応じて半導体レーザ１０４の発光強度は４段階に変調される。このような変調により半導体レーザ１０４から出射した光束は、λ／２板１０５を通過したのち、偏光ビームスプリッタ１０６に入射する。ここで半導体レーザ１０４からの光束は垂直偏光（ｓ偏光）であり、λ／２板１０５は記録時には光学軸が０度すなわち水平偏光方向を向いているため、偏光方向を変えることなく光束を通過させる。偏光ビームスプリッタ１０６は垂直偏光を反射し、水平偏光を透過する性質を有している（本実施例に用いられるいずれの偏光ビームスプリッタも同一の性質を有する）ため、記録時には半導体レーザ１０４からの光束を反射する。次に、反射した光束は第一のコリメートレンズ１０７によって平行光とされたのち、球面収差を補正するリレーレンズ１０８とλ／４板（光学軸方向は、水平偏光方向に対して４５度）１０９を通過し、アクチュエータ１１０に搭載されたＮＡ０．８５の対物レンズ１１１によって光ディスク１１２の内部の記録層に集光される。ここで、上記の４段階の変調に応じて、記録媒体にデータが記録される。 First, the operation during recording will be described. The laser driver 101 gives a modulation signal corresponding to user data sent from the host device 103 to the semiconductor laser 104 in accordance with an instruction from the microprocessor 102. Here, since the data is recorded with four values as an example, the modulation signal is modulated in four steps, and the emission intensity of the semiconductor laser 104 is modulated in four steps accordingly. The light beam emitted from the semiconductor laser 104 by such modulation passes through the λ / 2 plate 105 and then enters the polarization beam splitter 106. Here, the light beam from the semiconductor laser 104 is vertically polarized light (s-polarized light), and the λ / 2 plate 105 passes the light beam without changing the polarization direction because the optical axis is 0 degrees, that is, the horizontal polarization direction during recording. Let The polarization beam splitter 106 has the property of reflecting vertically polarized light and transmitting horizontally polarized light (all the polarized beam splitters used in this embodiment have the same property). Reflects light flux. Next, the reflected light beam is converted into parallel light by the first collimating lens 107, and then the relay lens 108 for correcting the spherical aberration and the λ / 4 plate (the optical axis direction is 45 degrees with respect to the horizontal polarization direction) 109. , And is condensed on the recording layer inside the optical disk 112 by the objective lens 111 with NA of 0.85 mounted on the actuator 110. Here, data is recorded on the recording medium in accordance with the above four-step modulation.
　なお、光ディスク１１２からの反射光は照射時と逆の光路を辿り、λ／４板１０９を往復で通過することにより偏光状態が水平偏光に変化され、偏光ビームスプリッタ１０６を透過する。その後、特殊偏光ビームスプリッタ１１３（水平偏光の光を５０％透過、５０％反射し、垂直偏光の光を１００％透過する）に入射し、反射光がシリンドリカルレンズ１１４を通過して４分割検出器１１５に集光され、検出される。４分割検出器１１５の出力信号から、フォーカスエラー信号、トラックエラー信号が生成され、サーボ回路１１６を介してアクチュエータ１１０の駆動電流としてフィードバックされる。これにより、対物レンズ１１１により集光された光束のスポット１１７の位置をサーボ制御する。本実施例では、フォーカスサーボ制御として非点収差法を、トラックサーボ制御としてプッシュプル法を用いた。 The reflected light from the optical disk 112 follows an optical path opposite to that at the time of irradiation, and passes through the λ / 4 plate 109 in a reciprocating manner, whereby the polarization state is changed to horizontal polarization and is transmitted through the polarization beam splitter 106. Thereafter, the light is incident on a special polarization beam splitter 113 (transmits 50% of the horizontally polarized light and reflects 50% of the light and transmits 100% of the vertically polarized light), and the reflected light passes through the cylindrical lens 114 and is divided into four parts. The light is collected at 115 and detected. A focus error signal and a track error signal are generated from the output signal of the quadrant detector 115 and fed back as a drive current of the actuator 110 via the servo circuit 116. Thus, the position of the spot 117 of the light beam condensed by the objective lens 111 is servo-controlled. In this embodiment, the astigmatism method is used as the focus servo control, and the push-pull method is used as the track servo control.
　次に、再生時の動作について説明する。波長４０５ｎｍの青色半導体レーザ１０４から出射した光は、λ／２板１０５を透過する。ここで、再生時にはλ／２板１０５の光学軸方向は記録時と異なり水平方向に対して２２．５度に設定されており、光束の偏光方向が４５度回転させられる。偏光の回転した光は偏光ビームスプリッタ１０６によって反射する垂直偏光の光束と透過する水平偏光の光束とに分割される。このうち反射された光束は、記録時と同様にして光ディスク１１２に照射される。光ディスク１１２からの反射光（以後信号光と呼ぶ）は、記録時と同様に、照射時と逆の光路を辿り、偏光ビームスプリッタ１０６に水平偏光の状態で入射する。一方、偏光ビームスプリッタ１０６を透過した光束（以後参照光と呼ぶ）は、コリメートレンズ１１８で平行光束とされた後、ミラー１１９で正反対の方向に反射され、λ／４板１２０（光学軸方向は、水平偏光方向に対して４５度）を往復で通過することにより偏光方向を垂直偏光とされ、偏光ビームスプリッタ１０６に再び入射する。信号光と参照光ともに、偏光ビームスプリッタ１０６から特殊偏光ビームスプリッタ１１３が配置されている方向に出射されるため、ここで信号光と参照光が、偏光が直交した状態で合波される。 Next, the operation during playback will be described. Light emitted from the blue semiconductor laser 104 having a wavelength of 405 nm passes through the λ / 2 plate 105. Here, during reproduction, the optical axis direction of the λ / 2 plate 105 is set to 22.5 degrees with respect to the horizontal direction, unlike during recording, and the polarization direction of the light beam is rotated by 45 degrees. The polarized light is split by the polarization beam splitter 106 into a vertically polarized light beam that is reflected and a horizontally polarized light beam that is transmitted. Of these, the reflected light beam is applied to the optical disk 112 in the same manner as during recording. Reflected light from the optical disk 112 (hereinafter referred to as signal light) follows an optical path opposite to that at the time of irradiation, as in recording, and enters the polarization beam splitter 106 in a state of horizontal polarization. On the other hand, the light beam that has passed through the polarizing beam splitter 106 (hereinafter referred to as reference light) is converted into a parallel light beam by the collimator lens 118, and then reflected by the mirror 119 in the opposite direction. , 45 degrees with respect to the horizontal polarization direction), the polarization direction becomes vertical polarization by reciprocating, and enters the polarization beam splitter 106 again. Since both the signal light and the reference light are emitted from the polarization beam splitter 106 in the direction in which the special polarization beam splitter 113 is disposed, the signal light and the reference light are combined in a state where the polarizations are orthogonal to each other.
　この合波光束は特殊偏光ビームスプリッタ１１３に入射し、信号光成分である水平偏光成分のみが記録時と同様に５０％の割合で反射され、残りは透過する。この反射光は記録時と同様に４分割検出器１１５で検出され、検出信号によりアクチュエータ１１０の位置が制御される。特殊偏光ビームスプリッタ１１３からの透過光束は、無偏光ハーフビームスプリッタ１２１によって透過光、反射光に２分割される。透過光は光学軸が水平方向に対して２２．５度に設定されたλ／２板１２２を通過して偏光が４５度回転し、ウォラストンプリズム１２３によってｐ偏光成分とｓ偏光成分に分離される。分離された光束は差動検出器１２４のフォトダイオード１２５，１２６にそれぞれ入射し、強度の差に比例した電気信号Ｄ1が差動検出器１２４から出力される。同様に、無偏光ハーフビームスプリッタ１２１を反射した光束は、光学軸が水平方向に対して４５度に設定されたλ／４板１２７を通過した後にウォラストンプリズム１２８によってｐ偏光成分とｓ偏光成分に分離される。分離された光束は差動検出器１２９のフォトダイオード１３０，１３１にそれぞれ入射し、強度の差に比例した電気信号Ｄ2が差動検出器１２９から出力される。後で述べるように、ウォラストンプリズム１２３，１２８で分離された後の光束はいずれも再生光と再生用参照光とが干渉した干渉光であり、差動検出器１２４，１２９の出力は干渉成分を抽出したものになっている。 This combined light beam enters the special polarization beam splitter 113, and only the horizontal polarization component, which is a signal light component, is reflected at a rate of 50% as in the recording, and the rest is transmitted. This reflected light is detected by the quadrant detector 115 as in the recording, and the position of the actuator 110 is controlled by the detection signal. The transmitted light beam from the special polarization beam splitter 113 is divided into two by the non-polarization half beam splitter 121 into transmitted light and reflected light. The transmitted light passes through a λ / 2 plate 122 whose optical axis is set to 22.5 degrees with respect to the horizontal direction, and the polarization is rotated by 45 degrees, and is separated into a p-polarized component and an s-polarized component by the Wollaston prism 123. The The separated light beams respectively incident on the photodiode 125 and 126 of the differential detector 124, an electrical signal D 1 that is proportional to the difference in intensity is output from the differential detector 124. Similarly, the light beam reflected by the non-polarization half-beam splitter 121 passes through a λ / 4 plate 127 whose optical axis is set to 45 degrees with respect to the horizontal direction, and then is p-polarized component and s-polarized component by the Wollaston prism 128. Separated. The separated light beams respectively incident on the photodiode 130, 131 of the differential detector 129, an electrical signal D 2 that is proportional to the difference in intensity is output from the differential detector 129. As will be described later, the light beams after being separated by the Wollaston prisms 123 and 128 are both interference light in which the reproduction light and the reproduction reference light interfere with each other, and the outputs of the differential detectors 124 and 129 are interference components. Is extracted.
　差動検出器１２４，１２９の出力はデジタル信号処理回路１４０に送られ、ここで記録されていた位相値が再生信号として得られる。得られた位相値は復調回路１４１で復調された後、復号回路１４２に送られてユーザデータに変換され、マイクロプロセッサ１０２を通して上位装置１０３に送られる。 The outputs of the differential detectors 124 and 129 are sent to the digital signal processing circuit 140, and the phase value recorded here is obtained as a reproduction signal. The obtained phase value is demodulated by the demodulating circuit 141, then sent to the decoding circuit 142, converted into user data, and sent to the host device 103 through the microprocessor 102.
　ここで、上に述べた再生時の動作により干渉光が生成され、これによって位相値を再生する原理について述べる。無偏光ハーフビームスプリッタ１２１に入射する光束は、ｐ偏光成分として再生光を、ｓ偏光成分として再生用参照光を含んでいるため、この偏光状態をジョーンズベクトルで表すと
Figure JPOXMLDOC01-appb-M000001
 Here, the principle of reproducing the phase value by generating the interference light by the operation at the time of reproduction described above will be described. Since the light beam incident on the non-polarization half beam splitter 121 includes reproduction light as a p-polarization component and reproduction reference light as an s-polarization component, this polarization state is represented by a Jones vector.
Figure JPOXMLDOC01-appb-M000001
となる。ここでＥsは信号光の電場、Ｅr参照光の電場である。また、このベクトルの第一成分はｐ偏光を、第二成分はｓ偏光を表す。この光束が無偏光ハーフビームスプリッタ１２１を透過し、λ／２板１２２を通過した後のジョーンズベクトルは
Figure JPOXMLDOC01-appb-M000002
 It becomes. Here E s is the electric field of the signal light, which is the electric field of E r reference light. The first component of this vector represents p-polarized light, and the second component represents s-polarized light. After this light beam passes through the non-polarization half beam splitter 121 and passes through the λ / 2 plate 122, the Jones vector is
Figure JPOXMLDOC01-appb-M000002
となる。次にウォラストンプリズム１２３によってｐ偏光成分とｓ偏光成分に分離されるため、分離された光束の電場はそれぞれ
Figure JPOXMLDOC01-appb-M000003
 It becomes. Next, since the wollaston prism 123 separates the p-polarized component and the s-polarized component, the electric fields of the separated light beams are respectively
Figure JPOXMLDOC01-appb-M000003
となり、信号光と参照光の重ね合わせ、すなわち干渉光となっている。 Thus, the signal light and the reference light are superimposed, that is, interference light.
　一方、無偏光ハーフビームスプリッタ１２１を反射した光がλ／４板１２７を通過した後のジョーンズベクトルは
Figure JPOXMLDOC01-appb-M000004
 On the other hand, the Jones vector after the light reflected by the non-polarization half beam splitter 121 passes through the λ / 4 plate 127 is
Figure JPOXMLDOC01-appb-M000004
となる。次にウォラストンプリズム１２８によってｐ偏光成分とｓ偏光成分に分離されるため、分離された光束の電場はそれぞれ
Figure JPOXMLDOC01-appb-M000005
 It becomes. Next, since the wollaston prism 128 separates the p-polarized component and the s-polarized component, the electric field of the separated luminous flux is respectively
Figure JPOXMLDOC01-appb-M000005
となり、やはり信号光と参照光の重ね合わせ、すなわち干渉光となっている。 Thus, the signal light and the reference light are superimposed, that is, interference light.
　従って、４つの干渉光の強度はそれぞれ、
Figure JPOXMLDOC01-appb-M000006
 Therefore, the intensity of each of the four interference lights is
Figure JPOXMLDOC01-appb-M000006
となり、それぞれ第１項、第２項が信号光、参照光の強度成分を表し、第３項が信号光と参照光の干渉を表す項である。Δφは参照光の位相を基準とした信号光の位相であり、これが再生されるべき変調信号である。差動検出器１２４，１２９の出力はこれらの分岐光の強度の差分に比例するため、それぞれ
Figure JPOXMLDOC01-appb-M000007
 The first term and the second term represent the intensity components of the signal light and the reference light, respectively, and the third term represents the interference between the signal light and the reference light. Δφ is the phase of the signal light based on the phase of the reference light, which is a modulated signal to be reproduced. Since the outputs of the differential detectors 124 and 129 are proportional to the difference in the intensity of these branched lights,
Figure JPOXMLDOC01-appb-M000007
と表され、上記の干渉を表す項に比例した出力となっている。検出器の変換効率は省略した。 The output is proportional to the term representing the interference. The conversion efficiency of the detector was omitted.
　上記の差動検出器１２４，１２９の出力はデジタル信号処理回路１４０においてまずＡ／Ｄ変換された後、演算回路に入力され、下記の演算結果が出力される。
Figure JPOXMLDOC01-appb-M000008
 The outputs of the differential detectors 124 and 129 are first A / D converted in the digital signal processing circuit 140 and then input to the arithmetic circuit, and the following arithmetic result is output.
Figure JPOXMLDOC01-appb-M000008
　以上のように、信号光と参照光の干渉光を生成し、これを検出することによって信号光の位相値を得ることができる。また、別の演算により、信号光の強度値の平方根に比例した信号を得ることも可能である。
Figure JPOXMLDOC01-appb-M000009
 As described above, the phase value of the signal light can be obtained by generating the interference light of the signal light and the reference light and detecting the interference light. It is also possible to obtain a signal proportional to the square root of the intensity value of the signal light by another calculation.
Figure JPOXMLDOC01-appb-M000009
　式(15)の平方根を省略すれば、信号光の強度値に比例した信号となる。 If the square root of equation (15) is omitted, the signal is proportional to the intensity value of the signal light.
　なお、本実施例では４つの干渉光の強度から位相値を推定したが、干渉光強度を決めるパラメータは、（１）信号光強度、（２）参照光強度、（３）信号光と参照光の位相差、の３つであるため、原理的には３つの異なる位相の干渉光強度を検出することにより、位相値が推定可能である。加えて信号光強度も推定可能である。たとえば図５に示すように、信号光と参照光の合波光束に対し、入射光束を無偏光ビームスプリッタ５０１，５０２によって３つに分割し、そのうち１つの光束はｓ偏光がｐ偏光に対して１２０度の位相差を生じる位相板５０３を、別の光束はｓ偏光がｐ偏光に対して２４０度の位相差を生じる位相板５０４を通過させ、３つの光束のいずれも４５度偏光のみを透過する偏光子５０５，５０６，５０７を透過させ、検出器５０８，５０９，５１０によって検出する。これらの検出器の出力Ｄ1，Ｄ2，Ｄ3はそれぞれ
Figure JPOXMLDOC01-appb-M000010
 In the present embodiment, the phase value is estimated from the intensity of the four interference lights, but the parameters that determine the interference light intensity are (1) signal light intensity, (2) reference light intensity, and (3) signal light and reference light. In principle, the phase value can be estimated by detecting the interference light intensities of three different phases. In addition, the signal light intensity can be estimated. For example, as shown in FIG. 5, the combined light flux of the signal light and the reference light is divided into three by non-polarizing beam splitters 501 and 502, and one of the light fluxes is s-polarized with respect to p-polarized light. Another light beam passes through the phase plate 504 that produces a phase difference of 120 degrees with respect to the p-polarized light, and another light beam passes only the 45-degree polarized light in all three light beams. Are transmitted through polarizers 505, 506, and 507, and detected by detectors 508, 509, and 510. The outputs D 1 , D 2 , D 3 of these detectors are respectively
Figure JPOXMLDOC01-appb-M000010
と表される。検出器の変換効率は省略した。これらの出力から、下記の演算を行うことにより位相値を推定できる。
Figure JPOXMLDOC01-appb-M000011
 It is expressed. The conversion efficiency of the detector was omitted. From these outputs, the phase value can be estimated by performing the following calculation.
Figure JPOXMLDOC01-appb-M000011
　また、下記の演算によって強度も推定可能である。
Figure JPOXMLDOC01-appb-M000012
 Also, the intensity can be estimated by the following calculation.
Figure JPOXMLDOC01-appb-M000012
　上記は、３つの異なる位相の干渉光強度を検出する例を説明したが、このように、位相、偏光を調整するようにして、４つ、５つなどの、３つ以上の複数の位相の干渉光強度を検出することができる。 The above has described an example of detecting the interference light intensity of three different phases. Thus, by adjusting the phase and polarization, the number of three or more phases such as four and five is adjusted. The interference light intensity can be detected.
　ここで、本実施例の記録・再生方法により従来に比べて簡素な構成で高いＳ／Ｎ比を得られることについて説明する。特許文献１やＣＤ，ＤＶＤなどの市販の光ディスクなど、ほとんどの従来技術においては、再生時に記録媒体から反射される光強度の変化を信号として読み取る。このため、光源の発光強度の揺らぎであるレーザーノイズは再生信号にノイズとして加算され、Ｓ／Ｎ比不足の原因となりうる。これに対し、本実施例では式(14)のごとく、光源の強度に無関係な出力が得られるため、レーザーノイズの影響を受けない。ここで重要なことは、４つの分岐光が同時に生成され、差動検出器の出力が（時間的に）同時に得られていることである。これにより、再生光や再生用参照光の強度が変動したとしても、分岐光が一様に変動するため、式(14)のごとく、演算において差動検出器の出力Ｄ1，Ｄ2の比が含まれており、上記の強度変動を常にキャンセルし、レーザーノイズの影響を受けない出力となる。検出器ノイズは、検出される光に関係なく検出器が持つノイズであり、記録媒体の反射率が小さいなどの原因により、検出される光の光量が小さいときに問題となる。これに対し、本実施例では再生用参照光の光量を十分大きくすることで検出器ノイズの影響を抑圧することができる。このことは、式(12)、式(13)を見ることで容易に理解できる。検出器ノイズは式(12)、式(13)で表される差動検出器の出力に加算される形で現れる。しかし、再生用参照光の強度を大きくすることで、式(12)、式(13)の値を大きくすることができ、検出器ノイズの大きさを相対的に小さくすることができる。 Here, it will be described that a high S / N ratio can be obtained with a simpler structure than the conventional one by the recording / reproducing method of the present embodiment. In most conventional techniques such as Patent Document 1 and commercially available optical discs such as CD and DVD, a change in light intensity reflected from a recording medium during reproduction is read as a signal. For this reason, laser noise, which is a fluctuation in the light emission intensity of the light source, is added to the reproduction signal as noise, which may cause a shortage of the S / N ratio. On the other hand, in the present embodiment, an output irrelevant to the intensity of the light source can be obtained as shown in Expression (14), and therefore, it is not affected by laser noise. What is important here is that four branched lights are generated simultaneously and the outputs of the differential detector are obtained simultaneously (in time). As a result, even if the intensity of the reproduction light or the reference light for reproduction fluctuates, the branched light fluctuates uniformly. Therefore, the ratio of the outputs D 1 and D 2 of the differential detector in the calculation is obtained as shown in equation (14). Is included, and the above intensity fluctuation is always canceled, and the output is not affected by laser noise. The detector noise is noise that the detector has regardless of the detected light, and becomes a problem when the amount of detected light is small due to a low reflectance of the recording medium. In contrast, in this embodiment, the influence of the detector noise can be suppressed by sufficiently increasing the amount of the reference light for reproduction. This can be easily understood by looking at equations (12) and (13). Detector noise appears in the form of being added to the output of the differential detector expressed by the equations (12) and (13). However, by increasing the intensity of the reproduction reference light, the values of the equations (12) and (13) can be increased, and the magnitude of the detector noise can be relatively reduced.
　なお、本実施例では、差動検出器は図６のように、２つのフォトダイオード１２５，１２６に入射した分岐光による光電流の差が、トランスインピーダンスアンプ６０１によって電流－電圧変換される、電流差動型の構成となっている。本構成により、十分な出力レベルを得るために再生用参照光の強度を高めた場合でも、再生用参照光自身の強度による光電流は２つのフォトダイオードで等しく、キャンセルされるため、トランスインピーダンスアンプでの飽和が起きないため、十分な出力信号レベルを得ることができ、効果的にアンプノイズの相対的な大きさを抑圧することができる。また、上記の差動検出器の構成においては、フォトダイオード２つにつきトランスインピーダンス１つが対応するため、通常のディテクタのごとくフォトダイオードの光電流をトランスインピーダンスで電流－電圧変換した出力を４つ用いて演算を行うよりも検出器ノイズを３ｄＢ低減することができ、この点においてもアンプノイズの抑圧に効果的である。 In this embodiment, as shown in FIG. 6, the differential detector is a current in which the difference in photocurrent due to the branched light incident on the two photodiodes 125 and 126 is converted from current to voltage by the transimpedance amplifier 601. It has a differential configuration. With this configuration, even when the intensity of the reproduction reference light is increased in order to obtain a sufficient output level, the photocurrent due to the intensity of the reproduction reference light itself is canceled by the two photodiodes, so that the transimpedance amplifier Therefore, a sufficient output signal level can be obtained, and the relative magnitude of amplifier noise can be effectively suppressed. Further, in the configuration of the differential detector described above, since one transimpedance corresponds to two photodiodes, four outputs obtained by current-voltage conversion of the photocurrent of the photodiode with the transimpedance are used as in a normal detector. Thus, the detector noise can be reduced by 3 dB compared to the calculation, and this point is also effective in suppressing the amplifier noise.
　なお、非特許文献１に記載の方法においても、原理的には同様の理由により高Ｓ／Ｎ比を得ることが可能である。しかし、非特許文献１の方法では、従来の光ディスク装置と異なり、データ記録時に２つの光束を記録媒体上の同一箇所に集光する必要がある。そのための位置決めの制御機構が複雑であり、かつ高い位置決め精度が要求されることから、記録動作を正確に行うことが困難である。このため、記録時に信号レベルの揺らぎが生じ、結果的に再生時のＳ／Ｎ比を劣化させる要因となりうる。これに対して本実施例においては、記録時の動作は従来の光ディスク装置と同様、単一の光束を記録媒体上に集光し、発光強度を制御すればよい。このため、集光スポットに対して要求される位置決め精度は従来の光ディスクと同程度であり、構成も簡素である。 In the method described in Non-Patent Document 1, a high S / N ratio can be obtained in principle for the same reason. However, unlike the conventional optical disc apparatus, the method of Non-Patent Document 1 needs to collect two light beams at the same location on the recording medium during data recording. Therefore, the positioning control mechanism is complicated, and high positioning accuracy is required, so that it is difficult to accurately perform the recording operation. For this reason, the signal level fluctuates during recording, and as a result, the S / N ratio during reproduction can deteriorate. On the other hand, in this embodiment, the recording operation may be performed by condensing a single light beam on the recording medium and controlling the light emission intensity, as in the conventional optical disk apparatus. For this reason, the positioning accuracy required for the focused spot is comparable to that of the conventional optical disc, and the configuration is simple.
　このように、本実施例は、従来技術に比べて簡素な構成でＳ／Ｎ比の向上が可能となるため、容易に多値度を高めることでき、記録密度とデータ転送速度を向上させることができる。なお、特許第４５６４９４８号において本実施例と類似の構成で信号光と参照光の干渉光を検出しているが、従来の光ディスクと同様に強度信号を取得しており、Ｓ／Ｎ比向上の効果は検出ノイズの相対的な低減のみにとどまるため、レーザーノイズの影響を受けない本実施例の方が高いＳ／Ｎ比を取得可能である。 As described above, the present embodiment can improve the S / N ratio with a simpler configuration than the prior art. Therefore, the multivalue level can be easily increased, and the recording density and the data transfer speed can be improved. Can do. In Japanese Patent No. 4564948, the interference light of the signal light and the reference light is detected with a configuration similar to that of the present embodiment. However, the intensity signal is acquired in the same manner as the conventional optical disc, and the S / N ratio is improved. Since the effect is limited only to the relative reduction of the detection noise, the present embodiment that is not affected by the laser noise can obtain a higher S / N ratio.
　本実施例の効果を検証するために、再生信号アイパターンのシミュレーションを実施した。記録媒体としては前述のように特許第２７０５３３０号に示される、記録時の光強度に応じて記録層の界面が変形するものを仮定し、記録時の発光強度を４段階に変調して４値記録を試みた。すなわち、記録層の界面が記録強度に応じて４通りの大きさに変形した記録ピットが１列に整列して配置される記録媒体を扱う。なお、上に述べたノイズの各成分の大きさとしては現行の光ディスク装置と同程度の値を用いた。また、記録、再生ともに光源の波長を４０５ｎｍとし、記録媒体に光を集光する際の対物レンズのＮＡは０．８５とした。 In order to verify the effect of this example, a reproduction signal eye pattern was simulated. As described above, the recording medium shown in Japanese Patent No. 2705330 assumes that the interface of the recording layer is deformed in accordance with the light intensity at the time of recording. Tried to record. That is, a recording medium in which recording pits whose interface of the recording layer is deformed into four sizes according to the recording intensity is arranged in a line is handled. The magnitude of each noise component described above was the same as that of the current optical disc apparatus. The wavelength of the light source for both recording and reproduction was 405 nm, and the NA of the objective lens when condensing light on the recording medium was 0.85.
　上述のごとく記録が行われた記録媒体に対し、従来の光ディスク装置と同一の方法、すなわち、記録媒体に光を集光して照射して上記記録ピット上を走査し、反射光の強度変化を検出して再生信号とする再生方法の場合の再生信号アイパターンを図７Ａに示す。この場合は、Ｓ／Ｎ比の不足により４値の変調を識別することが困難である。次に、特許第４５６４９４８号の方法で再生した場合の再生信号アイパターンを図７Ｂに示す。この再生方法は、本実施例と同様に記録媒体からの反射光を参照光と干渉させた光を検出したのち、式(14)の代わりに式(15)の演算により増幅された強度変調信号を再生したものである。この場合には、上述のごとくアンプノイズの相対的な大きさを抑圧したことにより、図７Ａに比べてＳ／Ｎ比の改善が見られるが、依然として４値レベルの識別にはエラーが生じる。これに対し、本実施例の方法で再生した場合の再生信号アイパターンを図７Ｃに示す。上述の２つの場合に比べて明らかにＳ／Ｎ比が改善しており、４値レベルの識別が容易である。これは上述のごとく、反射光の位相を再生する場合にはレーザーノイズの影響を受けないためであると説明できる。 The recording medium on which the recording is performed as described above is performed in the same manner as the conventional optical disk apparatus, that is, the recording medium is focused and irradiated with light to scan the recording pits, and the reflected light intensity changes. FIG. 7A shows a reproduction signal eye pattern in the case of a reproduction method for detecting a reproduction signal. In this case, it is difficult to identify quaternary modulation due to insufficient S / N ratio. Next, FIG. 7B shows a reproduction signal eye pattern when reproduction is performed by the method of Japanese Patent No. 4564948. In this reproduction method, as in the present embodiment, after detecting the light reflected from the recording medium and interfering with the reference light, the intensity modulated signal amplified by the calculation of Expression (15) instead of Expression (14) Are reproduced. In this case, although the S / N ratio is improved as compared with FIG. 7A by suppressing the relative magnitude of the amplifier noise as described above, an error still occurs in the discrimination of the quaternary level. In contrast, FIG. 7C shows a reproduction signal eye pattern when reproduction is performed by the method of this embodiment. The S / N ratio is clearly improved compared to the above two cases, and the quaternary level can be easily identified. As described above, this can be explained as not being affected by laser noise when the phase of the reflected light is reproduced.
　次に、式(14)で表される演算出力が、復号回路１４２に入力され、差分符号化されていた信号が復号化される原理について説明する。演算回路によって得られた位相Δφは、実際は再生信号成分以外の成分を含んでおり、正確には
Figure JPOXMLDOC01-appb-M000013
 Next, the principle by which the calculation output represented by Expression (14) is input to the decoding circuit 142 and the differentially encoded signal is decoded will be described. The phase Δφ obtained by the arithmetic circuit actually includes components other than the reproduction signal component.
Figure JPOXMLDOC01-appb-M000013
と表される。ここでφsは信号変調による位相、φrは信号光と参照光の光路長差（位相変調分は除く）に対応する位相差、である。 It is expressed. Here, φ s is a phase due to signal modulation, and φ r is a phase difference corresponding to an optical path length difference (excluding phase modulation) between the signal light and the reference light.
　φrは主に記録媒体の面ぶれ（光軸方向の変移、１００μｍオーダ）によって発生する。そして、これらは時刻とともに変動する。しかし、本実施例においては面ぶれの速度が数１０ｋＨｚ～数１００ｋＨｚ程度であるのに対し、データは数１０ＭＨｚ～数１００ＭＨｚで書き込まれるため、隣接する書き込み位置（シンボル）ではφrはほぼ一定である。従って隣接シンボル間の差を復号信号として出力することにより、上記の不要な位相成分φrの影響を受けることなく信号を再生することができる。 φ r is mainly generated by the surface blur of the recording medium (shift in the optical axis direction, on the order of 100 μm). These change with time. However, in the present embodiment, the surface blur speed is about several tens of kHz to several hundreds of kHz, whereas data is written at several tens of MHz to several hundreds of MHz, so φ r is substantially constant at adjacent writing positions (symbols). is there. Therefore by outputting the difference between the adjacent symbols as decoded signals, it is possible to reproduce the signal without undergoing effects of unnecessary phase component phi r above.
　なお、本実施例では参照光をミラー１１９によって正反対の方向に反射して信号光と合波させたが、合波させる方法はこの限りではなく、別の反射手段を用いても構わない。たとえば、図１５のごとく、参照光を直角プリズム１４３によって２回反射させ、偏光ビームスプリッタ１４６によって信号光と合波してもよい。この場合、λ／４板１２０の代わりにλ／２板１４４が挿入されており、参照光の偏光が９０度回転するようにしている。このほか、図１５の構成で直角プリズム１４３の代わりにレトロリフレクタ、コーナーキューブプリズムを用いてもよい。 In this embodiment, the reference light is reflected by the mirror 119 in the opposite direction and combined with the signal light. However, the method of combining is not limited to this, and another reflecting means may be used. For example, as shown in FIG. 15, the reference light may be reflected twice by the right-angle prism 143 and combined with the signal light by the polarization beam splitter 146. In this case, a λ / 2 plate 144 is inserted instead of the λ / 4 plate 120, and the polarization of the reference light is rotated by 90 degrees. In addition, a retroreflector and a corner cube prism may be used instead of the right-angle prism 143 in the configuration of FIG.
[実施例２]
　本実施例は、信号光と参照光の間の位相差を閉ループ制御する実施例である。本実施例による光情報記録再生装置の構成図を図２に示す。記録時の動作は実施例１と同様である。再生時には、信号光は基本的に実施例１と同様に検出される。一方参照光は、λ／４板１２０を通過したのち、ピエゾ素子２０１に搭載されたミラー２０２で反射され、その後アクチュエータ２０３に搭載されたミラー１１９によって正反対の方向に反射される。その後は実施例１と同様に信号光と合波されて検出される。なお、アクチュエータ２０３にはアクチュエータ１１０と同一のエラー信号が入力され、アクチュエータ１１０と同一量の変位がなされる。また、差動検出器１２４の出力は実施例１と同様に信号処理回路１４０に入力されるだけでなく、サーボ回路２０４に入射され、低周波成分（信号変調成分が除かれた成分）が抽出され、これを増幅した電圧信号が位相エラー信号としてピエゾ素子２０１の駆動電圧としてフィードバックされる。これによりミラー２０２の変位が生じ、信号光の（参照光に対する）平均的な位相が一定となるよう閉ループ制御される。 [Example 2]
In this embodiment, the phase difference between the signal light and the reference light is controlled in a closed loop. FIG. 2 shows a configuration diagram of an optical information recording / reproducing apparatus according to the present embodiment. The operation during recording is the same as in the first embodiment. At the time of reproduction, the signal light is detected in the same manner as in the first embodiment. On the other hand, the reference light passes through the λ / 4 plate 120, is reflected by the mirror 202 mounted on the piezo element 201, and then is reflected in the opposite direction by the mirror 119 mounted on the actuator 203. After that, the signal light is combined and detected in the same manner as in the first embodiment. Note that the same error signal as that of the actuator 110 is input to the actuator 203 and the same amount of displacement as that of the actuator 110 is performed. Further, the output of the differential detector 124 is not only input to the signal processing circuit 140 as in the first embodiment, but also enters the servo circuit 204 to extract a low frequency component (a component from which the signal modulation component is removed). Then, the amplified voltage signal is fed back as a drive voltage of the piezo element 201 as a phase error signal. As a result, the mirror 202 is displaced, and the closed loop control is performed so that the average phase of the signal light (relative to the reference light) becomes constant.
　以上の動作をより詳細に説明する。まず、アクチュエータ２０３のエラー信号による変位により、信号光と参照光との光路長が同程度に調整される。但しこの調整精度は数μｍ程度のオーダであり、依然として信号光と参照光の（信号変調成分を平均化した時の）位相差は変動している。ここでピエゾ素子を用いた閉ループ制御を用いると、上記位相差が固定される。これは、次のようにして説明される。変調された信号光は、位相変調がなされているため、仮に強度変調がなされていないとすると、変調された光の電場を複素平面上に図示すると図８Ａのように、同心円状に配置され、その平均値（すなわち信号変調成分を除いた低周波成分）も所定の値を持つ。ここで差動検出器１２４の出力は、これらの電場の実部成分とみなせる。すると、この出力がゼロとなるよう、低周波成分をエラー信号として閉ループ制御することにより、図８Ｂのように平均電場の実部成分がゼロとなる。このようにして、光ディスク１１２の面ぶれに伴う位相値の誤差φrをゼロに保つことができ、面ぶれが大きく、φrが差分符号化で完全に除去できない程度の大きさを持つ場合にも安定して位相信号を取得することが可能である。また、本実施例では信号処理回路１４０、復調回路１４１、復号回路１４２は実施例１と同一としたが、差分符号化を省略して復調回路１４１の簡略化をはかることも可能である。 The above operation will be described in more detail. First, the optical path lengths of the signal light and the reference light are adjusted to the same level by the displacement of the actuator 203 due to the error signal. However, this adjustment accuracy is on the order of several μm, and the phase difference between the signal light and the reference light (when the signal modulation component is averaged) still varies. Here, when closed-loop control using a piezo element is used, the phase difference is fixed. This is explained as follows. Since the modulated signal light is phase-modulated, if it is not intensity-modulated, the electric field of the modulated light is arranged concentrically as shown in FIG. 8A on the complex plane, The average value (that is, the low frequency component excluding the signal modulation component) also has a predetermined value. Here, the output of the differential detector 124 can be regarded as a real component of these electric fields. Then, the real part component of the average electric field becomes zero as shown in FIG. 8B by performing the closed loop control using the low frequency component as an error signal so that the output becomes zero. In this way, the phase value error φ r due to the surface blur of the optical disc 112 can be kept at zero, the surface blur is large, and φ r has a size that cannot be completely removed by differential encoding. It is also possible to acquire the phase signal stably. In this embodiment, the signal processing circuit 140, the demodulation circuit 141, and the decoding circuit 142 are the same as those in the first embodiment. However, the demodulation circuit 141 can be simplified by omitting the differential encoding.
　上に述べた動作原理から明らかなように、記録時の動作として、平均電場がゼロ以外の所定の値となるような記録パターンとする必要がある。 As is apparent from the operation principle described above, the recording pattern needs to have a recording pattern in which the average electric field has a predetermined value other than zero as the recording operation.
　また、本実施例ではアクチュエータ２０３、ピエゾ素子２０１の組み合わせにより位相誤差φrをゼロに抑える構成としたが、これはアクチュエータで面ぶれの大きさに対応した調整範囲を確保し、ピエゾ素子で位相を安定に保つ精度を確保することを狙ったものである。このような構成によりアクチュエータとピエゾ素子それぞれに対して要求される性能を高くする必要がないため、簡易に実現可能である。一方で、例えば十分な調整範囲と調整精度を備えたアクチュエータを用いることで、図３のように構成を簡略化することも可能である。この場合、参照光はアクチュエータ２０３に搭載されたミラー１１９で正反対の方向に反射される構成となっており、サーボ回路２０４から生成されるエラー信号を用いてアクチュエータ２０３の位置を閉ループ制御することで位相誤差φrをゼロに保つことができる。 In this embodiment, the combination of the actuator 203 and the piezo element 201 is configured to suppress the phase error φ r to zero. However, this ensures an adjustment range corresponding to the size of the surface blur by the actuator, and the piezo element has a phase difference. The aim is to ensure the accuracy of maintaining a stable state. With such a configuration, it is not necessary to increase the performance required for each of the actuator and the piezo element, which can be easily realized. On the other hand, for example, by using an actuator having a sufficient adjustment range and adjustment accuracy, the configuration can be simplified as shown in FIG. In this case, the reference light is reflected in the opposite direction by the mirror 119 mounted on the actuator 203, and the position of the actuator 203 is closed-loop controlled using an error signal generated from the servo circuit 204. The phase error φ r can be kept at zero.
　さらに、位相値を制御する形態はこの限りではなく、例えばピエゾ素子２０１の代わりに図９に示される楔形プリズム対を挿入してもよい。この場合、楔形プリズム９０１，９０２の一方の挿入量（入射光軸に垂直な方向、図の矢印の向き）をアクチュエータで制御することにより、位相値の調整が可能である。従って楔形プリズム９０１をアクチュエータに搭載し、これにエラー信号を入力することで位相値の閉ループ制御が可能である。 Furthermore, the form for controlling the phase value is not limited to this, and for example, a wedge-shaped prism pair shown in FIG. 9 may be inserted instead of the piezo element 201. In this case, the phase value can be adjusted by controlling the insertion amount of one of the wedge prisms 901 and 902 (the direction perpendicular to the incident optical axis, the direction of the arrow in the figure) with an actuator. Therefore, the wedge-shaped prism 901 is mounted on the actuator, and an error signal is input to the actuator, whereby the phase value can be closed-loop controlled.
　本実施例の場合も実施例１と同様、ミラー１１９の代わりに直角プリズム、コーナーキューブプリズム、レトロリフレクタ等を用いた構成としても構わない。 In the case of this embodiment as well, similarly to the first embodiment, a configuration using a right-angle prism, a corner cube prism, a retroreflector, or the like instead of the mirror 119 may be used.
[実施例３]
　本実施例は、差動検出器の出力から位相値を得るための演算処理を行わず、直接再生信号を取得する実施例である。本実施例による光情報記録再生装置の構成図を図４に示す。本実施例では、差動検出信号は差動検出器１２４からの出力のみであり、実施例１、実施例２と比べて無偏光ハーフビームスプリッタ１２１等の部品が省略されている。また、実施例２と同様に差動検出器１２４の出力信号を用いて信号光の位相を閉ループ制御する。信号処理回路１４０では、実施例１、実施例２で行う位相値の演算を行わず、差動検出器１２４の出力信号をＡ／Ｄ変換したものがそのまま出力され、復調回路１４１で変調レベルの判定が行われる。なお、差分符号化は行われない。 [Example 3]
In this embodiment, the reproduction signal is directly acquired without performing the arithmetic processing for obtaining the phase value from the output of the differential detector. FIG. 4 shows a configuration diagram of an optical information recording / reproducing apparatus according to the present embodiment. In this embodiment, the differential detection signal is only an output from the differential detector 124, and components such as the non-polarization half beam splitter 121 are omitted as compared with the first and second embodiments. Similarly to the second embodiment, the phase of the signal light is closed-loop controlled using the output signal of the differential detector 124. In the signal processing circuit 140, the phase value calculation performed in the first and second embodiments is not performed, and the output signal of the differential detector 124 is A / D converted and output as it is, and the demodulation circuit 141 outputs the modulation level. A determination is made. Note that differential encoding is not performed.
　この復調の原理を、図１０を用いて説明する。実施例２で説明したとおり、位相値の制御によって変調された信号光の各電場は、図１０のような状態で固定される。ここで差動検出器１２４からの出力は実施例２で述べたように、これらの電場の実部成分であるため、４つの電場に対応して４レベルの変調信号が差動検出器１２４の出力において観測される。従って、実施例１、実施例２のように位相値の演算を行うことなく、４つのレベルの判定を行うことによりデータの復調が可能である。なお、この場合も実施例２と同様に、記録時の動作として、平均電場がゼロ以外の所定の値となるような記録パターンとする必要がある。 The principle of this demodulation will be described with reference to FIG. As described in the second embodiment, each electric field of the signal light modulated by controlling the phase value is fixed in a state as shown in FIG. Here, since the output from the differential detector 124 is a real part component of these electric fields as described in the second embodiment, four levels of modulation signals corresponding to the four electric fields are output from the differential detector 124. Observed at the output. Therefore, data can be demodulated by performing the determination of four levels without calculating the phase value as in the first and second embodiments. In this case as well, as in the second embodiment, the recording pattern needs to have a recording pattern in which the average electric field has a predetermined value other than zero as an operation during recording.
　なお、本実施例では位相値を直接演算していないが、図１０より明らかなように、得られる再生信号は信号光の位相変化に伴う実部成分を観測したものに他ならないため、間接的に信号光の位相変調を観測していると言える。 In the present embodiment, the phase value is not directly calculated. However, as is clear from FIG. 10, the obtained reproduction signal is nothing but an observation of the real part component accompanying the phase change of the signal light. It can be said that the phase modulation of the signal light is observed.
[実施例４]
　本実施例は、差動検出器の出力から得られる信号光の位相値だけでなく、強度値との組み合わせにより復号を行う実施例である。本実施例による光情報記録再生装置の構成は基本的に実施例２と同じく、図２に示されるとおりである。ただし、デジタル信号処理回路１４０において、図１１に示すブロック図のように、差動検出信号Ｄ1，Ｄ2の値から信号光の位相値のみでなく、強度値も出力する。これらの位相値と強度値それぞれに対して後に続く復号回路においてレベル判定を行い、これらの結果よりレベルの識別を行う。本実施例に示すような光強度の変調によるデータ記録を行った場合、再生時の信号光における位相値と強度値には明確な相関が生じる。従って、このようなレベル判定を行うことにより、位相値のみのレベル判定を行う場合に比べて判定の精度を向上させることがで、より正確にデータを再生することが可能となる。 [Example 4]
In the present embodiment, decoding is performed not only by the phase value of the signal light obtained from the output of the differential detector but also by a combination with the intensity value. The configuration of the optical information recording / reproducing apparatus according to the present embodiment is basically as shown in FIG. However, the digital signal processing circuit 140 outputs not only the phase value of the signal light but also the intensity value from the values of the differential detection signals D 1 and D 2 as shown in the block diagram of FIG. Each of these phase values and intensity values is subjected to level determination in the subsequent decoding circuit, and the levels are identified based on these results. When data recording is performed by modulation of light intensity as shown in this embodiment, a clear correlation occurs between the phase value and the intensity value in the signal light during reproduction. Therefore, by performing such level determination, it is possible to improve the accuracy of determination compared to the case of performing level determination of only the phase value, and it is possible to reproduce data more accurately.
　なお、強度値の情報を組み合わせる方法はこの限りではない。例えば、２つの差動検出信号は図１２に示すように、それぞれ信号光電場の実部成分と虚部成分に対応付けることができる。従って、各差動検出信号の判定レベルの組み合わせより、復調を行ってもよい。さらに、上記実部成分と虚部成分より、信号光の複素電場振幅が得られたことになるため、この値と所望の複素電場振幅との複素平面上の距離を算出することにより、レベル判定を行ってもよい。このような場合も、光強度や位相が陽な形で表れないが、複素平面上でのレベル判定を行うという点において信号光の位相値（複素平面上の偏角に対応）と強度（複素平面上の絶対値、すなわち原点からの距離に対応）の双方の情報を用いて復調を行っており、やはり位相値のみによる復調に比べて高精度なレベル判定が可能となっている。 Note that this is not the only way to combine strength value information. For example, as shown in FIG. 12, two differential detection signals can be associated with the real part component and the imaginary part component of the signal photoelectric field, respectively. Therefore, demodulation may be performed based on a combination of determination levels of the differential detection signals. Furthermore, since the complex electric field amplitude of the signal light is obtained from the real part component and the imaginary part component, the level determination is performed by calculating the distance on the complex plane between this value and the desired complex electric field amplitude. May be performed. Even in such a case, the light intensity or phase does not appear in an explicit form, but the phase value of the signal light (corresponding to the declination on the complex plane) and intensity (complex Demodulation is performed using both information on the absolute value on the plane, that is, corresponding to the distance from the origin), and it is possible to determine the level with higher accuracy than the demodulation based on the phase value alone.
　さらに、本実施例は差分符号化を適用することにより、ピエゾ素子２０１やアクチュエータ２０３等からなる位相制御の機構を省略し、実施例１と同様の図１の構成でも実現可能である。この場合も、復調回路１４１において信号光の位相値と強度値に基づき復調を行う。なお、この場合の差分符号化は位相値のみに対して行えばよく、光ディスク１１２の面ぶれによる値の変動を伴わない強度値に対しては必ずしも行う必要がない。 Further, the present embodiment can be realized with the configuration of FIG. 1 similar to that of the first embodiment by applying the differential encoding to omit the phase control mechanism including the piezo element 201 and the actuator 203. Also in this case, the demodulation circuit 141 performs demodulation based on the phase value and intensity value of the signal light. In this case, the differential encoding may be performed only on the phase value, and it is not always necessary to perform on the intensity value that is not accompanied by the fluctuation of the value due to the surface shake of the optical disk 112.
　なお、本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 In addition, this invention is not limited to the above-mentioned 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.
　本発明により、大容量と高い転送速度を両立した光情報記録再生装置の提供が可能となり、大容量ビデオレコーダや、ハードディスクデータバックアップ装置、保存情報アーカイブ装置など、幅広い産業応用が期待できる。 The present invention makes it possible to provide an optical information recording / reproducing apparatus having both a large capacity and a high transfer speed, and a wide range of industrial applications such as a large capacity video recorder, a hard disk data backup device, and a stored information archive device can be expected.
１０１　レーザドライバ
１０２　マイクロプロセッサ
１０３　上位装置
１０４　半導体レーザ
１０５　λ／２板
１０６　偏光ビームスプリッタ
１０７　コリメートレンズ
１０８　リレーレンズ
１０９　λ／４板
１１０　アクチュエータ
１１１　対物レンズ
１１２　光ディスク
１１３　特殊偏光ビームスプリッタ
１１４　シリンドリカルレンズ
１１５　４分割検出器
１１６　サーボ回路
１１７　スポット
１１８　コリメートレンズ
１１９　ミラー
１２０　λ／４板
１２１　無偏光ハーフビームスプリッタ
１２２　λ／２板
１２３　ウォラストンプリズム
１２４　差動検出器
１２５，１２６　フォトダイオード
１２７　λ／４板
１２８　ウォラストンプリズム
１２９　差動検出器
１３０，１３１　フォトダイオード
１４０　デジタル信号処理回路
１４１　復調回路
１４２　復号回路
１４３　直角プリズム
１４４　λ／２板
１４５　集光レンズ
１４６　偏光ビームスプリッタ
２０１　ピエゾ素子
２０２　ミラー
２０３　アクチュエータ
２０４　サーボ回路
５０１，５０２　無偏光ビームスプリッタ
５０３，５０４　位相板
５０５，５０６，５０７　偏光子
５０８，５０９，５１０　検出器
６０１　トランスインピーダンスアンプ
９０１，９０２　楔形プリズム 101 Laser Driver 102 Microprocessor 103 Host Device 104 Semiconductor Laser 105 λ / 2 Plate 106 Polarizing Beam Splitter 107 Collimating Lens 108 Relay Lens 109 λ / 4 Plate 110 Actuator 111 Objective Lens 112 Optical Disc 113 Special Polarizing Beam Splitter 114 Cylindrical Lens 115 Quadrant Detector 116 Servo circuit 117 Spot 118 Collimate lens 119 Mirror 120 λ / 4 plate 121 Non-polarization half beam splitter 122 λ / 2 plate 123 Wollaston prism 124 Differential detector 125, 126 Photodiode 127 λ / 4 plate 128 Wollaston Prism 129 Differential detector 130, 131 Photo diode 140 Digital signal processing circuit 141 Demodulation circuit 142 Decoding circuit 143 Right angle pre 144 λ / 2 plate 145 Condensing lens 146 Polarizing beam splitter 201 Piezo element 202 Mirror 203 Actuator 204 Servo circuit 501, 502 Non-polarizing beam splitter 503, 504 Phase plate 505, 506, 507 Polarizer 508, 509, 510 Detector 601 Transimpedance amplifiers 901 and 902 Wedge prism

Claims (5)

  1. 　記録光強度を変化させて記録することにより反射光の位相に変化が生じる記録媒体を用いて記録再生を行う光情報記録再生装置であって、
    　光源と、
    　前記光源の発光強度を制御する制御部と、
    　前記光源からの光束を第一の光束と第二の光束とに分割する光分割手段と、
    　前記第一の光束を前記記録媒体上の所定の位置に集光する集光手段と、
    　前記第二の光束を反射させる反射手段と、
    　前記記録媒体から反射された前記第一の光束を前記反射手段によって反射された前記第二の光束と合波し、前記第一の光束と前記第二の光束間の相対位相が異なる３種類以上の干渉光を生成する干渉光学系と、
    　前記干渉光を検出する検出器と、
    　前記検出器の出力から再生信号を生成する信号処理部と、を有し、
    　記録時には、前記制御部により前記光源の発光強度を多段に変調し前記第一の光束を記録光として前記記録媒体上に照射することで情報の記録を行い、
    　再生時には、前記信号処理部において前記第二の光束の位相を基準とした前記記録媒体から反射された前記第一の光束の位相値を取得することを特徴とする光情報記録再生装置。     An optical information recording / reproducing apparatus that performs recording / reproduction using a recording medium in which the phase of reflected light changes when recording is performed by changing the recording light intensity,
    A light source;
    A control unit for controlling the emission intensity of the light source;
    A light splitting means for splitting a light beam from the light source into a first light beam and a second light beam;
    Condensing means for condensing the first light flux at a predetermined position on the recording medium;
    Reflecting means for reflecting the second light flux;
    Three or more kinds of the first light flux reflected from the recording medium and the second light flux reflected by the reflecting means, and having different relative phases between the first light flux and the second light flux An interference optical system for generating interference light of
    A detector for detecting the interference light;
    A signal processing unit that generates a reproduction signal from the output of the detector,
    At the time of recording, information is recorded by modulating the emission intensity of the light source in multiple stages by the control unit and irradiating the recording medium with the first light beam as recording light,
    At the time of reproduction, the signal processing unit acquires the phase value of the first light beam reflected from the recording medium based on the phase of the second light beam.
  2. 　記録光強度を変化させて記録することにより反射光の位相に変化が生じる記録媒体を用いて記録再生を行う光情報記録再生装置であって、
    　光源と、
    　前記光源の発光強度を制御する制御部と、
    　前記光源からの光束を第一の光束と第二の光束とに分割する光分割手段と、
    　前記第一の光束を前記記録媒体上の所定の位置に集光する集光手段と、
    　前記第二の光束を反射させる反射手段と、
    　前記第一の光束と前記第二の光束の相対位相を制御する位相制御手段と、
    　前記記録媒体から反射された前記第一の光束を前記反射手段によって反射された前記第二の光束と合波し、前記第一の光束と前記第二の光束間の相対位相が異なる２種類以上の干渉光を生成する干渉光学系と、
    　前記干渉光を検出する検出器と、
    　前記検出器の出力から再生信号を生成する信号処理部と、を有し、
    　記録時には、前記制御部により前記光源の発光強度を多段に変調し前記第一の光束を記録光として前記記録媒体上に照射することで情報の記録を行い、
    　再生時には、前記位相制御手段により前記第一の光束と前記第二の光束の平均的な位相差が一定になるように制御し、前記信号処理部において前記第二の光束の位相を基準とした前記記録媒体から反射された前記第一の光束の位相値を取得することを特徴とする光情報記録再生装置。     An optical information recording / reproducing apparatus that performs recording / reproduction using a recording medium in which the phase of reflected light changes when recording is performed by changing the recording light intensity,
    A light source;
    A control unit for controlling the emission intensity of the light source;
    A light splitting means for splitting a light beam from the light source into a first light beam and a second light beam;
    Condensing means for condensing the first light flux at a predetermined position on the recording medium;
    Reflecting means for reflecting the second light flux;
    Phase control means for controlling the relative phase of the first light flux and the second light flux;
    Two or more types in which the first light flux reflected from the recording medium is combined with the second light flux reflected by the reflecting means, and the relative phases between the first light flux and the second light flux are different. An interference optical system for generating interference light of
    A detector for detecting the interference light;
    A signal processing unit that generates a reproduction signal from the output of the detector,
    At the time of recording, information is recorded by modulating the emission intensity of the light source in multiple stages by the control unit and irradiating the recording medium with the first light beam as recording light,
    At the time of reproduction, the phase control means controls the average phase difference between the first light beam and the second light beam to be constant, and the signal processing unit uses the phase of the second light beam as a reference. An optical information recording / reproducing apparatus for acquiring a phase value of the first light beam reflected from the recording medium.
  3. 　請求項２に記載の光情報記録再生装置において、前記干渉光学系で生成される干渉光は２種類であることを特徴とする光情報記録再生装置。 3. The optical information recording / reproducing apparatus according to claim 2, wherein there are two types of interference light generated by the interference optical system.
  4. 　請求項１又は２に記載の光情報記録再生装置において、前記信号処理部において前記干渉光学系で生成される干渉光の対の強度差に比例する差動検出信号を用いて前記位相値を取得することを特徴とする光情報記録再生装置。 3. The optical information recording / reproducing apparatus according to claim 1, wherein the phase value is obtained by using a differential detection signal proportional to a difference in intensity of a pair of interference light generated by the interference optical system in the signal processing unit. An optical information recording / reproducing apparatus.
  5. 　請求項１又は２に記載の光情報記録再生装置において、前記信号処理部において前記第一の光束の強度値と前記第二の光束の位相を基準とした前記記録媒体から反射された前記第一の光束の位相値を取得し、前記強度値と前記位相値に基づき復調を行うことを特徴とする光情報記録再生装置。 3. The optical information recording / reproducing apparatus according to claim 1, wherein the first signal reflected from the recording medium on the basis of an intensity value of the first light beam and a phase of the second light beam in the signal processing unit. An optical information recording / reproducing apparatus characterized in that a phase value of the luminous flux is acquired and demodulated based on the intensity value and the phase value.
PCT/JP2012/060542 2011-06-07 2012-04-19 Optical information recording and reproduction device WO2012169286A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6190339A (en) * 1984-10-08 1986-05-08 Nec Corp Optical pick-up
JPH0520712A (en) * 1990-09-12 1993-01-29 Ricoh Co Ltd Recording medium, recording method and recorder
JP2008065961A (en) * 2006-09-11 2008-03-21 Hitachi Ltd Optical information-detecting method, optical head, and optical disk device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6190339A (en) * 1984-10-08 1986-05-08 Nec Corp Optical pick-up
JPH0520712A (en) * 1990-09-12 1993-01-29 Ricoh Co Ltd Recording medium, recording method and recorder
JP2008065961A (en) * 2006-09-11 2008-03-21 Hitachi Ltd Optical information-detecting method, optical head, and optical disk device

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