Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
• • 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
  • G11B7/13—Optical detectors therefor
  • G11B7/131—Arrangement of detectors in a multiple array
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10532—Heads
  • G11B11/10541—Heads for reproducing
  • G11B11/10543—Heads for reproducing using optical beam of radiation
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10595—Control of operating function
  • G11B11/10597—Adaptations for transducing various formats on the same or different carriers
• • 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
  • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
  • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
  • G11B7/0943—Methods and circuits for performing mathematical operations on individual detector segment outputs
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10502—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing characterised by the transducing operation to be executed
  • G11B11/10515—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
  • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
  • G11B7/005—Reproducing

Definitions

• the present invention relates to an optical signal detection circuit for optically reproducing a signal recorded on an optical recording medium such as a disk or a tape, and particularly to a magneto-optical recording circuit.
• the present invention relates to an optical signal detection circuit which is preferably applied to reproduction of a signal recorded on a magneto-optical disk or an optical disk recorded by changing a phase bit or a reflectance.
• a recording signal is recorded by vertically magnetizing a magnetic film in an upward or downward direction in accordance with the recording signal.
• the reproduction of the magneto-optical disk is performed by irradiating the disk with linearly polarized laser light.
• the plane of polarization of the reflected light of the linearly polarized laser light applied to the magneto-optical disk rotates according to the up and down directions of magnetization due to the so-called Kerr effect.
• a change in the plane of polarization of the reflected light is converted into a change in light intensity by an analyzer such as a polarization beam splitter.
• the photodetector detects this variation in light intensity as a photocurrent.
• Photodetectors include, for example, bin (PIN) photodiodes or Photodiodes such as avalanche photodiodes are used. When this photocurrent is passed through the current / voltage converter, a reproduced signal is obtained.
• the S / N ratio is improved by canceling the in-phase noise.
• the reflected light from the magneto-optical disk is rotated, for example, by a 1Z2 wavelength plate, and then converted into two light beams having opposite phase light intensity modulation through a analyzer. Changes in the light intensity of these light beams are detected by photodetectors, respectively, and a magneto-optical reproduction signal is obtained from the differential components.
• Two light beams, intensity-modulated in opposite phases, are incident on the photodiodes 80 and 81 shown in FIG. 1, and current flows because electron-hole pairs are generated in proportion to the amount of incident light.
• Two oppositely-modulated current signals are extracted from each anode (or from each cathode).
• reverse bias is applied to each terminal to increase the response speed and the range of linearity, thereby reducing the capacitance between the electrodes.
• the output current from photodiodes 80 and 81 is converted to voltage signals by current / voltage converters 84 and 85 after the DC component is cut through capacitors 82 and 83, respectively. Is done.
• the current / voltage converters 84, 85 output voltage signals of opposite phases to the inverting terminal (1) and the non-inverting terminal (+) of the differential amplifier 86, respectively.
• the differential amplifier 86 removes the common mode noise component of the supplied signal and extracts the differential component. To obtain a playback signal.
• Fig. 2 shows a conventional single detection method, in which an electron-hole pair generated by light incident on the photodiode 80 is extracted from one end of the photodiode 80, that is, either the anode or the cathode. It is. So this method only extracts one electron-hole pair.
• output currents of opposite phases corresponding to the incident light are taken out from the anode side and the force side of the photodiode 80.
• Output currents of opposite phases are supplied to current / voltage converters 89, 90 via capacitors 87, 88, respectively.
• the current / voltage converters 89, 90 obtain voltage signals of opposite phases.
• the voltage signals having the opposite phases are supplied to the differential amplifier 91, respectively.
• the differential amplifier 91 obtains a reproduced signal by extracting a differential component.
• the signal amount at this time is twice the signal amount by the conventional single detection method.
• two current / voltage converters 89, 90 are used, which is twice that of the single detection method, but the noise generated by the current / voltage converter is random noise.
• the noise generated by the current-to-voltage converter in the final output signal of this circuit is doubled. As a result, the noise level of the current-Z voltage converter with respect to the signal level can be reduced to 12.
• FIG. 4 shows an example of a magneto-optical signal detection circuit to which such a differential detection method is applied.
• the circuit in Fig. 4 has two circuits of the differential detection method in Fig. 3.
• the respective parts of these two differential detection type circuits are denoted by reference numerals a and b for the corresponding reference numerals in FIG. 3 and the description thereof is omitted.
• the noise level of the current Z voltage converter with respect to the signal level can be reduced to 1 / ⁇ 2.
• the noise level of the current / voltage converter with respect to the signal level can be reduced to 1/2, but compared to the circuit configuration shown in FIG. Adding two differential amplifiers will increase the circuit scale. Increasing the circuit size leads to an increase in circuit power consumption and cost.
• the circuit for extracting the differential component of the detection signal from each of the light receiving elements 80 and 81 as shown in FIG. 3 extracts the magneto-optical signal from the reflected light from the magneto-optical disk.
• the phase bits there is a technique for extracting an optical signal from an optical disk recorded by a change in reflectance.
• recording by phase bits is a method of forming and recording concave and convex phase bits formed on an optical disc according to information.
• This recording method is used in read-only optical disks and write-once optical disks.
• information is recorded by changing the physical state of a recording layer irradiated with laser light from, for example, amorphous to crystalline.
• the reproducing apparatus reads information based on a difference in the amount of reflected laser light that reflects a change in the state of the optical disc depending on whether information is recorded.
• This recording method is employed in write-once and rewritable optical disks.
• an adder 87 is provided, and the in-phase optical signal is reproduced by adding the output signals from the current / voltage converters 84 and 85.
• the current output of the same phase is obtained from each anode side (or each force side) of the photodiodes 80 and 81, and these are converted into voltage signals by the current / voltage converters 34 and 35. And sent to the adder 37. At this time, no signal appears at the output terminal of the differential amplifier 86.
• a conventional magneto-optical recording / reproducing apparatus also performs compatible reproduction of a read-only disc recorded with phase bits, for example, to reproduce address information or the like recorded in advance with phase bits on a magneto-optical disc.
• the differential amplifier 86 but also the adder 95 is provided. There is much.
• An optical signal detection circuit optically detects a recording signal recorded on a recording medium by two light detection means, and the one light detection means in these light detection means.
• An output signal from one terminal side of the above-mentioned terminal and an output signal from the terminal side of the other light detection means for outputting an in-phase component to this output signal are added to current and converted into a voltage signal by current / voltage conversion means. It is something to do.
• the optical signal detection circuit optically detects a signal recorded on a recording medium by two light detection means, and from one terminal side of one of the light detection means in these light detection means.
• Output signal The current output is added to the output signal of the other photodetector that outputs an in-phase component from the terminal side of the other photodetector and converted into a voltage signal by the first current / voltage converter.
• the second current / voltage conversion means is obtained by adding current to the output signal from the other terminal of the second light detection means and the output signal from the terminal of the other light detection means for outputting an in-phase component to this output signal.
• the output signal from the first and second current / voltage conversion means is differentially amplified.
• a magneto-optical recording medium is used as the recording medium
• first and second photodiodes are used as the light detecting means
• the first current / voltage converting means is used as the first photo / voltage converting means.
• the current obtained by adding the output current from the anode side of the diode and the output current from the power source side of the second photodiode is converted into a voltage, and the second current / voltage described above is converted.
• the conversion means preferably converts a current obtained by adding the output current from the power source side of the first photodiode and the output current from the anode side of the second photodiode to a voltage.
• a second photodiode that receives incident optical signals having opposite phases with the first and second photodiodes and outputs an in-phase component with an output signal from the anode side of the first photodiode.
• the output signal from the first side that is, the output signal from the force side
• the output signals from these two photodiodes are added together with the in-phase components
• the first current / voltage converter outputs a voltage.
• the output signal from the second photodiode that outputs an in-phase component with the output signal from the cathode of the first photodiode, that is, the output signal from the anode side is extracted.
• the output signals from the two photodiodes are added to the in-phase components and converted into a voltage signal by the second current / voltage converter.
• the output signals of the first and second current-to-voltage converters are differentially amplified by a differential amplifier. /
• the noise from the voltage converter can be suppressed by a factor of 1 to improve the S / N ratio by 6 dB.
• the optical signal detection circuit optically detects a recording signal recorded on a recording medium by two light detection means, and outputs an output current from the anode side of one of the light detection means and the other.
• the current obtained by adding the output current from the light detecting means is converted into a voltage signal by the first current Z voltage converting means, and the output signal from the cathode side of the one light detecting means and the other.
• the current obtained by adding the output currents from the light detecting means is converted into a voltage signal by the second current / voltage converting means, and the output signal from the cathode side of the other light detecting means is converted by the first switching means.
• Is supplied to one of the first current / voltage conversion means and the second current / voltage conversion means, and the output signal from the anode side of the other light detection means is supplied by the second switching means.
• the first current / voltage conversion means and the The first and second current / voltage converters are switched and supplied to one of the second current / voltage converters to differentially amplify the output signals from the first and second current / voltage converters.
• FIG. 1 is a circuit diagram for explaining a conventional magneto-optical signal detection method.
• FIG. 2 is a circuit diagram illustrating a single detection method in the magneto-optical signal detection method.
• FIG. 3 is a circuit diagram illustrating a differential detection method in the magneto-optical signal detection method.
• FIG. 4 is a diagram showing a circuit configuration based on a conventional magneto-optical signal differential detection method.
• FIG. 5 is a diagram showing a schematic configuration of a circuit capable of detecting in-phase / out-phase light in a conventional magneto-optical signal detection method.
• FIG. 6 is a circuit diagram showing a magneto-optical signal detection circuit as an embodiment of the optical signal detection circuit according to the present invention.
• FIG. 7 is a diagram showing a specific example of the current / voltage converter in the magneto-optical signal detection circuit.
• FIG. 8 is a circuit diagram showing a modification of the magneto-optical signal detection circuit.
• FIG. 9 is a diagram showing a circuit configuration in consideration of the phase relationship between signals output from the magneto-optical signal detection circuit.
• FIG. 10 is a diagram showing an example of a circuit in which a configuration for detecting in-phase / out-phase optical signals is added to the magneto-optical signal detection circuit shown in FIG. 6 above.
• FIG. 4 is a diagram illustrating an example of a circuit in which a configuration for detecting in-phase / out-phase optical signals is added to the magneto-optical signal detection circuit illustrated in FIG.
• FIG. 12 is a diagram showing a modification of the circuit of FIG.
• FIG. 13 is a diagram showing a first specific example of an optical beakup to which the optical signal detection circuit is applied.
• FIG. 14 is a diagram showing patterns and equivalent circuits of the light receiving elements 24 and 26 used in the optical big-up of FIG.
• FIG. 15 is a diagram showing a pattern and an equivalent circuit of the light receiving element 20 used in the optical big-up of FIG. 13 described above.
• FIG. 16 is a diagram illustrating a second specific example of an optical pickup to which the above-described optical signal detection circuit is applied.
• FIG. 17 is a diagram showing a pattern and an equivalent circuit of a conventional light receiving element used for the optical big-up of FIG.
• FIG. 18 is a diagram showing a pattern and an equivalent circuit of a light receiving element used in the optical big-up of FIG. 16 to realize the above embodiment.
• FIG. 19 is a diagram showing a third specific example of an optical big-up to which the above-described magneto-optical signal detection circuit is applied.
• FIG. 20 is a diagram showing the structure of the optical element 46 used for the optical big-up shown in FIG. 19, the pattern of the light receiving element, and the equivalent circuit.
• FIG. 21 is a diagram showing a pattern and an equivalent circuit of a light-receiving element used in the optical big-up of FIG. 19 to realize the above embodiment.
• FIG. 22 is a diagram illustrating an example of a magneto-optical signal detection circuit when the light receiving element of FIG. 21 is used.
• FIG. 23 is a diagram showing a schematic configuration of an optical disk reproducing apparatus to which the above-described optical big-up is applied.
• FIG. 24 is a flowchart for explaining the operation procedure of the optical disk reproducing apparatus. It is a chart.
• FIG. 25 is a diagram for explaining a method of generating an address window for performing in-phase / out-phase light detection in the optical disk reproducing apparatus.
• FIG. 26 is a diagram showing a more simplified circuit configuration of the optical disc reproducing apparatus.
• BEST MODE FOR CARRYING OUT THE INVENTION a photodiode is used as a photodetector or a photodetector.
• FIG. 6 shows a magneto-optical signal detection circuit according to a first embodiment of the present invention.
• the magneto-optical signal detection circuit shown in FIG. 6 includes two photodiodes PD 1 and PD 1 for detecting an optical signal. It is composed of a PD 2 and a current / voltage converter 1 for adding currents of the output signals from the photodiodes PD 1 and PD 2 and converting the signals into a voltage.
• a positive + V bias voltage is applied to the cathode side of the photodiode PD1.
• a negative bias voltage of 1 V is applied to the anode side of the photodiode PD1 via the resistor R2.
• a positive + V bias voltage is applied to the force source side of the photodiode PD2 via the resistor R3.
• the anode side of the photodiode PD 2 has a negative polarity 1 V bias voltage. Pressure is being applied.
• the output from the anode side which is one terminal of one photodiode PD 1 of the two photodiodes PD 1 and PD 2, and the other photo diode that outputs an in-phase component to this output signal
• the output from the cathode side which is the terminal of the diode PD2
• Supplying This is because such a connection has a low input impedance at the input terminal of the current-to-Z voltage converter 1, so that the current can be added by directly connecting the output currents via the capacitors C1 and C2, respectively. .
• the current / voltage converter 1 is, for example, as shown in FIG. 8 (a), a negative feedback amplifier 1 a having an inverting input and a negative feedback resistor R, or as shown in FIG. 8 (b), It can be configured by the amplifier 1 b and the negative feedback resistor R.
• the current / voltage converter 1 has a current signal having the same amplitude as the conventional magneto-optical signal detection circuit by combining the current signals as described above. Will be input. Also, since only one current / voltage converter 1 is required, the current / voltage converter 1 reduces the amount of noise generated to half that of a conventional magneto-optical signal detection circuit. Can be reduced. As a result, the S / N ratio is improved by 3 dB, and a current / voltage converter and a differential amplifier are not required one by one, as compared with the conventional circuit configuration. be able to.
• the magneto-optical signal detection circuit for example, as shown in FIG. Of the photodiode PD1 and PD2 of the other photodiode PD1 and the terminal of the other photodiode PD2 that outputs an in-phase component to the output signal from the cathode side, which is one terminal of PD1, and this output signal.
• the output from the anode side is defined as the output current from which the DC component has been removed via the capacitors C 3 and C 4, respectively, and these output currents are added to the current and supplied to the current / voltage converter 2.
• a current signal having the same amplitude as that of the conventional magneto-optical signal detection circuit is input to the current / voltage converter 2 by combining the current signals.
• the noise due to the current-to-voltage converter becomes 1/2 times that of the conventional magneto-optical signal detection circuit, the S / N ratio is improved by 3 dB, and the circuit size is reduced. be able to.
• the phases of the output signals from the current / voltage converters 1 and 2 are opposite to each other. Focusing on this, as shown in Fig. 9, each of the two current / voltage converters 1 and 2 and the current / voltage converters 1 and 2 supplied to the terminal side considering the output phase are
• the magneto-optical signal detection circuit may include the differential amplifier 3 for differentially amplifying the output.
• common parts are given the same reference numerals, and description thereof is omitted.
• In-phase output signals from the anode of the photodiode PD1 and the force source of the photodiode PD2 are supplied to the current / voltage converter 1 via the capacitors C1 and C2.
• the output signal from the photodiode PD 1 force node and the photodiode PD 2 anode is The current is supplied to the Z-voltage converter 2 via the capacitors C 3 and C 4.
• a current signal having a double amplitude is supplied by current addition of signals having the same phase.
• the phases of the signals output from the current / voltage converters 1 and 2 are opposite to each other, for example, when the output of the current / voltage converter 2 is used as a reference, the current / voltage The output from the converter 2 is supplied to the non-inverting terminal side, and the output from the current / voltage converter 1 is supplied to the inverting terminal side of the differential amplifier 3.
• the differential amplifier 3 outputs the output signal as a reproduced signal having the same phase amplitude twice as that of FIG. 6 or FIG.
• the noise of the current / voltage converter with respect to the reproduced signal is 12. Therefore, the SZN ratio for the reproduced signal can be improved by 6 dB.
• the circuit scale can be reduced while suppressing the noise of the current / voltage converter.
• the S / N ratio of the reproduced signal can be improved, and for example, the error rate in a digital system can be significantly improved, improving reliability, information density, and transmission speed.
• the optical path to reduce the amount of light incident on the light receiving element and increase the optical path efficiency from the laser light emitting element to the surface of the magneto-optical disk, the output power of the laser light emitting element is also kept low and the system life is extended.
• Can be planned By reducing the circuit scale, power consumption can also be reduced.
• FIG. 10 shows an example of an optical signal detecting circuit for reproducing a signal recorded by magneto-optical recording as described above and a signal recorded by a phase bit or a change in reflectance.
• the optical signal detection circuit shown in FIG. 10 is a switch for turning on / off the output current obtained via the capacitor C2 from the force source of the other photodiode PD2 of the magneto-optical signal detection circuit of FIG. It is configured with SW.
• the optical signal detection circuit of FIG. 10 includes two photodiodes PD 1 and PD 2 for detecting an optical signal, and a switching circuit provided between the photodiode PD 2 and the current-Z voltage converter 1.
• a current / voltage converter 1 that adds current to the output signal supplied from the photodiode PD 2 via the switch sw, the photodiode PD 1 and the switching switch SW, and converts the output signal into a voltage.
• the current / voltage converter 1 can have the configuration shown in FIGS. 8A and 8B described above. Other configurations are the same as those in FIG. 6 described above, and corresponding portions are denoted by the same reference symbols and description thereof is omitted.
• FIG. 10 (a) shows a case where an optical signal of opposite phase is supplied from a magneto-optical disk or the like
• FIG. 10 (b) shows the same from an optical disk recorded with a phase bit or a change in reflectance. This shows a case where a phase optical signal is supplied.
• the photodiodes PD1 and PD2 When reproducing the magneto-optical signal, as shown in FIG. 10 (a), the photodiodes PD1 and PD2 receive optical signals that are intensity-modulated in opposite phases to each other, thereby forming a photodiode.
• Photodiode PD 1 The output current from the node side and the output current from the cathode side of the photodiode PD2 are output in the same phase.
• the switch SW is turned on, that is, closed, so that the current / voltage converter 1 is connected via the capacitors C 1 and C 2 to the current / voltage converter 1.
• the signal from which the DC component has been removed is supplied by current addition.
• Such a connection is because the input impedance at the input terminal of the current-to-voltage converter 1 is low, and the current can be added by directly connecting the outputs via the capacitors C1 and C2, respectively. is there.
• current / voltage converter 1 outputs a voltage signal corresponding to twice the signal obtained from photodiodes PD 1 and PD 2 as a reproduction signal.
• this optical signal detection circuit requires only one current / voltage converter 1, the current / voltage converter 1 is smaller than the conventional magneto-optical signal detection circuit in the amount of noise generated.
• the current-to-voltage converter 1 receives a current signal having the same amplitude as that of the conventional magneto-optical signal detection circuit by combining the current signals as described above.
• the S / N ratio is improved by 3 dB, as compared with the conventional circuit configuration, the current / voltage converter and the differential amplifier are no longer required.
• the circuit scale can be reduced.
• This light detection signal is half the amplitude of the reproduced signal in FIG. 10 (a).
• the switch SW may be provided on the photodiode PD1 side. Further, a switch for turning on / off the output current from one of the photodiodes P D1 and P D2 of the magneto-optical detection circuit shown in FIG. 8 may be provided.
• an optical signal detection circuit provided with switching switches SW 1 and SW 2 in the magneto-optical signal detection circuit of FIG. 9 to reproduce a magneto-optical signal and a phase bit or a reflectance change recording signal. This will be described with reference to FIG.
• the optical signal detection circuit shown in FIG. 11 can output reproduced signals of the same signal level regardless of the phase relationship of the incident optical signals.
• the output current on the cathode side of the other photodiode PD 2 is switched to the current / voltage converter 1 or the current / voltage converter 2.
• the output current on the anode side of the switching switch SW 1 to be supplied and the photodiode PD 2 A switching switch SW2 for switching and supplying the current / voltage converter 1 or the current Z voltage converter 2 is provided. That is, the selected terminal 1a of the switching switch SW1 connected to the capacitor C2 on the cathode side of the photodiode PD2 is connected to the current-voltage converter 1, and the selected terminal 1b of the switching switch SW1 is connected to the current / Connected to voltage converter 2.
• the selected terminal 2a of the switching switch SW2 connected to the capacitor C4 on the anode side of the photodiode PD 2 is connected to the current / voltage converter 2, and the selected terminal 2b of the switching switch SW2 is connected to the current / voltage converter 2. It is connected to the current / voltage converter 1.
• Other configurations are the same as those in FIG. 9 described above, and corresponding portions are denoted by the same reference symbols and description thereof is omitted.
• two photodiodes PD1 and PD2 receive optical signals that are intensity-modulated in opposite phases to each other, and The output current on the node side of PD 1 and the output current on the cathode side of the photodiode PD 2 have the same phase, and these output currents are added to form a voltage signal by the current / voltage converter 1. The signal is converted and sent to the inverting input terminal of the differential amplifier 3.
• the output current of the photodiode PD1 on the power source side and the output current of the photodiode PD2 on the anode side have the same phase, and these output currents are added to form a current / voltage.
• the voltage signal is converted by the converter 2 into a voltage signal, and this voltage signal has an opposite phase to the voltage signal from the current / voltage converter 1 and the non-inversion of the differential amplifier 3 Input terminal.
• the signal level can be doubled, and the S / N ratio can be doubled, that is, the signal level can be improved by 6 dB.
• the switching switches SW1 and SW2 are connected to the selected terminal lb, 2 Switch to the b side.
• an optical signal whose intensity is modulated in phase with the two photodiodes PD 1 and PD 2 is incident on the photodiodes PD 1 and PD 2, and the output current on the anode side of the photodiode PD 1 and the photodiode PD 2.
• the output current on the first side has the same phase as the output current, and these output currents are summed, converted into a voltage signal by the current / voltage converter 1, and sent to the inverting input terminal of the differential amplifier 3.
• the output current on the cathode side of the photodiode PD1 and the output current on the cathode side of the photodiode PD2 have the same phase. These output currents are added, and the current / voltage converter 2 outputs a voltage signal. This voltage signal has an opposite phase to the voltage signal from the current / voltage converter 1 and is sent to the non-inverting input terminal of the differential amplifier 3.
• FIG. 12 shows a modified example of the optical signal detection circuit of FIG. 11 described above, in which each of the selected terminals 1 b and 2 b of each of the switching switches SW 1 and SW 2 in FIG.
• an example of an open state is shown.
• a simple on / off switch may be used instead of the changeover switches SW1 and SW2.
• the switching switches SW1 and SW2 are respectively connected to the selected terminals 1a and 2a by switching connection.
• the configuration is the same as that of 11 (a), and the same operation and effect can be obtained.
• the switching switches SW1 and SW2 are connected to the selected terminals lb and 2b. Side, but nothing is connected to these selected terminals lb, 2b, which is equivalent to a simple on / off switch off state.
• the output current from the anode and cathode of the photodiode PD 2 is cut off, and the current / voltage converter 1 receives only the output current from the anode side of the photodiode PD 1 and the current / voltage converter 2 Only the output current from the cathode side of the photodiode PD 1 is supplied to each of these, and voltage signals having phases opposite to each other are output from these current / voltage converters 1 and 2 and sent to the differential amplifier 3.
• the amplified signal is differentially amplified and output as a double amplitude reproduced signal.
• the differential amplifier 3 can obtain only half the amplitude of the reproduced signal obtained from the circuit shown in FIG. 11 (b), for example. It is possible to provide a circuit capable of reproducing a signal without connection and without depending on the type of the optical disc.
• FIG. 13 shows an optical system of an optical pickup using two independent light receiving elements for detecting a magneto-optical signal (corresponding to the photodiodes PD 1 and PD 2 of the above embodiment).
• the return signal is separated optically, so that the service signal and the magneto-optical signal are detected by separate light-receiving elements, and a polarization beam splitter is used as an analyzer.
• Two independent light receiving elements are used for signal detection.
• a total of four light receiving elements are used by providing light receiving elements for monitoring light.
• This optical pickup is closest to the principle of magneto-optical disk playback, but is not often used in products due to its complicated configuration.
• the focus servo error signal detection For this reason, the critical aberration method is used, and the differential Bushbull method is used to detect tracking servo error signals.
• the light emitted from the laser light emitting element 11 is collimated by the collimating lens 12 and supplied to the grating 13.
• Grating 13 separates the incident light into three beams for tracking error detection by the differential bush-pull method.
• Some of these beams are beam splitters 14
• the reflected light is incident on the light receiving element 15 for optical power monitoring, and is used for controlling the optical power of the laser light emitting element 11.
• the light transmitted through the beam splitter 14 is focused on the signal surface or the recording surface of the magneto-optical disk D SK by the objective lens 16.
• the return light reflected from the signal surface of the magneto-optical disk DSK is magnetized to the N and S poles on the magneto-optical disk DSK, and the polarization plane slightly changes in the positive and negative directions according to the information recorded magnetically. It is spinning.
• This return light is converted into parallel light again by the objective lens 16 and is incident on the beam splitter 14.
• a part of this return light is reflected by the beam splitter 14, the optical path is bent by 90 °, and enters the beam splitter 17.
• a part of the return light incident on the beam splitter 17 is again bent by 90 ° in the optical path, and is incident on the light receiving element 20 for servo signal detection via the condenser lens 18 and the cylindrical lens 19.
• a part of the return light that has entered the beam splitter 17 is transmitted, enters the half-wavelength plate 21, rotates the polarization by 45 °, and enters the polarization beam splitter 22.
• the polarization beam splitter 22 converts the change in the plane of polarization of the return light into a change in intensity and at the same time splits it into two beams, which are converged by condensing lenses 23 and 25, respectively.
• a light spot 29 is irradiated on a light receiving surface 28 as shown in FIG. It is represented by an equivalent circuit as shown in (b).
• the light receiving element 20 has, for example, a light receiving surface pattern as shown in FIG. 15A, and an equivalent circuit is as shown in FIG. 15B.
• the light-receiving surface in the center of the light-receiving surface pattern in Fig. 15 (a) is divided into four, and the respective nodes are A to D.
• the light-receiving surfaces on both sides are each divided into two, and one of the light-receiving surfaces is The anodes are F and E, the anodes on the other light receiving surface are H and G, and the cathode is K in common.
• the focus error signal FE is obtained by the astigmatism method.
• the tracking error signal TE is calculated by the differential push-pull method.
• T E ((a + d)-(c + d)) -k ((f-e) + (h-g))
• a magneto-optical signal is obtained by taking the difference between the output signals from the respective nodes.
• the anode output current of the light receiving element 24 (corresponding to PD 1) and the cathode output current of the light receiving element 26 (corresponding to PD 2) are added. By doing so, a magneto-optical signal is obtained.
• a magneto-optical signal can be obtained by using the configuration of the example of FIG. 8 or the example of FIG.
• FIG. 10 in the case of extracting a signal recorded by the change of the phase bit ⁇ ⁇ reflectance, FIG. 10, FIG. 11 or FIG.
• FIG. 15 (a) showing the light receiving surface pattern of the light receiving element 20
• a + b + c + d The signal recorded by the above-mentioned phase bit / reflectance change may be reproduced by obtaining the following equation.
• a three-beam Wollaston prism 35 is used as an analyzer that converts the rotation of the polarization plane of light obtained by the force effect into light intensity.
• the astigmatism method is used for focus error detection
• the differential Bushbull method is used for tracking error detection.
• the light emitted from the laser light emitting element 11 is collimated by the collimating lens 12 and supplied to the grating 13.
• the grating 13 has the tracking error by the differential push-pull method.
• the light transmitted through the beam splitter 32 is focused by the objective lens 34 on the signal surface or the recording surface of the magneto-optical disk DSK.
• the return light reflected from the signal surface of the magneto-optical disk DSK is magnetized to the N and S poles on the magneto-optical disk DSK and magnetically recorded.
• the plane of polarization is rotated according to the information. This return light is
• the light becomes parallel again by 3 4, and is again incident on the beam splitter 32.
• a part of this return light is reflected by the beam splitter 32 and travels 90 in the optical path. It is bent and incident on a so-called Wollaston prism 35.
• This returned light is further divided into three beams by the Wollaston prism 35, while the change in the rotation direction of the polarization plane is converted into a change in intensity.
• These beams are condensed by a condenser lens 36 and a cylindrical lens 37 for focus error detection by the astigmatism method, and are incident on a light receiving element 38.
• the light-receiving surface pattern of the light-receiving element 38 is as shown in FIG. 17 (a) in the case of a conventionally used light-receiving element, and is shown in FIG. 18 (a) in the case of the above-described embodiment. Become like
• the nodes A to D which are light receiving areas divided into four at the center, are provided at the center, and the leading beams of the three beams divided by the above-mentioned grating 13 are provided.
• anodes E and F of a two-part light receiving area are provided, and anodes G and H of a two-part light receiving area are provided corresponding to the succeeding beam.
• anodes I and J in a light receiving area for detecting a magneto-optical signal are provided at the left and right positions of the central portion of the light receiving surface pattern corresponding to the three beams split by the Wollaston prism.
• An equivalent circuit of a configuration including each of the anodes A to J and the common cathode K in these light receiving regions is represented by 10 photodiodes as shown in FIG. 17 (b).
• FIG. 18 (a) showing a light receiving surface pattern for realizing the above embodiment
• output currents are also taken out from the respective cathode sides of the light receiving regions I and J for detecting a magneto-optical signal. Need Therefore, independent force sword regions K (I) and K (J) are provided around these light receiving regions I and J, respectively. Therefore, as shown in Fig. 18 (b), the equivalent circuit is composed of eight photodiodes with the light receiving areas A to H as anodes and a common power source K, and each of the light receiving areas I and J as anodes. , Consisting of two photodiodes, each with independent power swords K (I) and K (J).
• the focus error signal FE is obtained by the astigmatism method.
• the tracking error signal TE is calculated by the differential Bush-Pull method.
• the light receiving element PD 1 may be used in accordance with the circuit configuration of FIG. 6 of the above-described embodiment.
• the output current of the anode is taken out from the node in the light receiving area I
• the force output current of the light receiving element PD 2 is taken out from the cathode K (J) in the light receiving area J, and these output currents are added.
• a magneto-optical signal may be obtained.
• a magneto-optical signal can be obtained by using the configuration of the example of FIG. 8 or the configuration of the example of FIG. Sa
• the configuration shown in FIG. 10, FIG. 11, or FIG. 12 of the above-described embodiment may be used.
• the anode output current of the light-receiving region I and the output current of the cathode K (I) are defined as the anode output current and the cathode output current from the light-receiving element PD1 in FIGS.
• the output current and the output current of the power source K (J) may be used as the anode output current and the cathode output current from the light receiving element PD2 in FIGS.
• the signals recorded based on the phase pits and the change in reflectivity can be extracted by adding all the output signals a to d from each of the divided areas A to D on the central light receiving surface in Fig. 18 (a). It may be performed by obtaining a + b + c + d.
• a so-called microprism detector 46 in which a polarizing beam splitter, a mirror, and a photodetector are integrated is used.
• the concentric circle method is used, and the busple method is used for tracking error detection.
• a cylindrical lens is not used because the differential concentric circle method is used for focus error detection, and the Bushbull method is used for tracking error signal detection. Therefore, the grating that divides the beam into three beams is not used.
• the light emitted from the laser light emitting element 11 is collimated by the collimator lens 12 and supplied to the beam splitter 41. Part of the supplied light beam is reflected at the beam splitter 4 1 Then, the light is incident on the light receiving element 42 for optical power monitoring, and is used for controlling the optical power of the laser light emitting element 11.
• the light transmitted through the beam spot 41 is focused by the objective lens 43 on the signal surface or the recording surface of the magneto-optical disk DSK.
• Return light obtained by being reflected on the signal surface of the magneto-optical disk DSK becomes parallel light again by the objective lens 43 and is incident on the beam splitter 41. A part of this return light is reflected by the beam splitter 41, the optical path is bent 90 °, and it is incident on the 12-wavelength plate 21 and the polarization is rotated 45 ° and converged by the condenser lens 45. After being converted into light, the light enters the microphone aperture prism detector 46.
• the microprism detector 46 is configured by integrating a polarizing beam splitter 47, a reflecting surface 48, and a light detecting element 49, and
• the light receiving surface pattern of the element 49 is, for example, as shown in FIG. 20 (b). That is, the return light from the condenser lens 45 in Fig. 19 is incident on the polarization beam splitter 47 of the microbism detector 46, and the change in the polarization plane of the return light changes in intensity. Simultaneously, the light is converted into two beams and is incident on two partial patterns of the light receiving element 49.
• each of the two partial patterns has a substantially square shape, and is horizontally divided into three horizontally long light receiving regions.
• the light receiving area on the middle side is further divided into two, and the four light receiving areas A, Bl, B2, and C are shown in FIG. It is formed as the anode of the photodiode of the equivalent circuit of c).
• the three light receiving regions D, E, and F of the other partial pattern are also the photodiodes of the equivalent circuit in Fig. 20 (c). It is the anode.
• the power sword of these photodiodes is referred to as the common sword K.
• FIG. 21 (a) shows a light receiving surface pattern of a photodetector that can be used in the embodiment described with reference to FIG. 6 and FIGS. ) Shows the equivalent circuit.
• the equivalent circuit in Fig. 21 (b) is almost the same as the light-receiving surface pattern in Fig. 20 (b) ⁇ Fig. 20 (c).
• independent cathodes K1 and K2 are provided for every two partial patterns. ⁇ That is, one partial pattern of the light-receiving surface pattern in Fig. 21 (a).
• a common force sword K 2 is provided independently of each other.
• FIG. 22 shows an example in which, for example, the circuit configuration shown in FIG. 9 is realized using the photodetector shown in FIG.
• the four photodiodes composed of the anode regions A, B1, B2, and C and the common force node K1 correspond to the photodiode PD1 in FIG.
• Three photodiodes consisting of D, E, F and the common force sword K2 correspond to the photodiode PD2 in FIG.
• the focus error signal FE is expressed by the differential concentric circle method.
• FIGS. 10 to 12 which can perform compatible reproduction of the signal recorded by the optical bit-up as described above, particularly, the phase bit and the like, and the signal recorded by the magneto-optical recording.
• the system configuration and operation of an optical disk playback device configured using an optical big-box will be described with reference to FIGS.
• the optical system 10 having the configuration shown in FIGS. 13, 16, and 19 described above, and the magneto-optical signal reproduction described with these drawings and the related light-receiving surface pattern, etc.
• the optical disk reproducing device shown in FIG. 23 has an optical system 10 and photodiodes PD 1 and PD 2 constituting an optical big-up, and a signal subjected to signal processing based on an output from the optical big-up.
• the signal processing unit 50 performs signal processing on a signal reproducing unit 51 and a magneto-optical information signal processing for extracting magneto-optical information by performing signal processing on an output signal from the signal reproducing unit 50.
• Section 52 a phase pit information signal processing section 53 that performs signal processing on the same signal supplied to the magneto-optical information signal processing section 52 to extract phase bit information, and a photodiode as a light receiving element.
• a light amount detection unit 54 for detecting the amount of light received by PD 1 and PD 2.
• the return light of the laser beam irradiated on the optical disk DSK on the optical disk DSK surface is incident on the photodiodes PD1 and PD2, which are light receiving elements.
• the light received by the photodiodes PD 1 and PD 2 is supplied to the signal reproducing unit 51 of the signal processing unit 50.
• the signal reproducing unit 51 converts the current signal obtained by the photoelectric conversion by the current addition detection method into a voltage signal and converts the current signal into a magneto-optical information signal processing unit, as in the circuit configurations of FIGS. 10 to 12 described above.
• the output signal is supplied to 52, the phase signal, and the sort information signal processing section 53.
• the signal reproducing section 51 supplies an electric signal based on the light received by the photodiodes PD 1 and PD 2 to the light quantity detecting section 54.
• the light amount detection unit 54 is required to be distinguished from a magneto-optical disk when the optical disk reproducing apparatus configured as described above actually reproduces a read-only optical disk recorded with phase bits or the like. It is known that a normal read-only optical disk has a reflectivity about 5 times higher than a normal magneto-optical disk.
• the light quantity detection unit 54 regards the difference in the reflectance between the magneto-optical disc and the read-only optical disc on which, for example, a phase pit has been formed, as the difference in the light quantity, and determines the difference with respect to a predetermined threshold value. The type of the optical disk is determined. This optical disc discrimination signal is supplied from the light quantity detection unit 54 to the system control unit 55.
• the system control unit 55 switches the switch SW of FIG. 10 or the switch SW of FIGS. 11 and 12 so as to correspond to whether the light of the same phase / opposite phase is detected according to the optical disk discrimination signal. 1.
• SW2 is switched.
• a switching selection signal is sent to the signal reproducing unit 51. Since the output timing of the switching selection signal differs depending on the type of the optical disc, the processing described later is performed by the system control unit 55.
• the switching selection signal in the optical disk reproducing apparatus, information recorded regardless of the type of the optical disk is obtained via the magneto-optical information signal processing section 52 and the phase bit information signal processing section 53.
• the optical disk reproducing apparatus is operated by the system control unit 55 in accordance with the procedure shown in FIG. 24, for example.
• step S1 a disc as a recording medium is inserted into the optical disc reproducing apparatus.
• step S2 the control of the system control section 55 operates the servo circuits of the respective sections to set a state in which information from the optical disk DSK can be detected, and then proceeds to step S3.
• step S3 address information recorded on the optical disk DSK is reproduced, and an address window described later is generated.
• step S4 the switching selection signal is changed as to whether the address information or the information from the optical disc DSK to be reproduced according to the generated address window is in the address / data area, and the process proceeds to step S5.
• step S5 it is determined whether signal reproduction from the optical disk DSK has been completed. To determine If the signal reproduction has not been completed yet (NO), the process returns to step S3 and repeats the processing of steps S3 and S4 described above. When the signal reproduction is completed (Yes), the signal reproduction of the optical disk DSK is completed.
• one track is divided into a plurality of tracks.
• the unit of each divided area is called a sector.
• an address indicating a sector position on the optical disk is recorded in advance by a phase bit.
• Magneto-optical discs can be managed and searched overnight by such sector division and addressing.
• both the information area recorded in advance by the phase bit, ie, the address area AD, and the information area recorded by the direction of magnetization, ie, both the data area D, are read.
• an optical signal having the same phase / opposite phase is applied to two photodiodes.
• the incident light makes it impossible to detect, for example, a phase bit in principle. Therefore, the system control unit 55 controls the switching of the switching switches SW1 and SW2 of the signal reproducing unit 51 in accordance with the disc discrimination signal that distinguishes one of the mixed areas.
• an address window is generated so as to extract only the address area AD.
• the signal reproducing unit 51 is set to a mode for detecting the light having the same phase, and the address information is reproduced. .
• the timing of the address area AD and the data area D becomes clear.
• the system control unit 55 uses this timing relationship to generate an address window shown in FIG. If this evening is used as a control signal for the switching switch, it becomes possible to switch between the in-phase / out-phase light detection modes.
• the signal processing unit 50 can be configured without providing the light amount detection unit 54.
• the system control unit 55 supplies a switching selection signal to the signal reproduction unit 51 using the address information reproduced from the phase bit information signal processing unit 53. .
• the type of the optical disc is generally provided with a lead-in area in which the disc identification information is recorded at the innermost peripheral portion of the optical disc, the type of the optical disc can be known from the information reproduced from the lead-in area. Therefore, it can be seen that it is better for the optical disk reproducing apparatus to perform reading in the same-phase light detection mode when a disk is inserted. In this method, not only a read-only optical disk, but also a write-once optical disk recorded by a change in reflectance, for example, can be discriminated as a magneto-optical disk.
• the lead-in portion describes the address range of a read-only area and the address range of a recording / reproducing area.
• the magneto-optical disk is recorded by the phase bit recording or the reflectance change, and the optical disk is distinguished from the optical disk. Corresponding playback can be performed.
• the circuit scale can be reduced while suppressing the noise of the current / voltage converter.
• the noise of the current / voltage converter By reducing the noise of the current / voltage converter, the S / N ratio of the reproduced signal can be improved, and for example, the error rate in digital systems can be significantly improved, improving reliability, information density, and transmission speed. Can be achieved.
• the optical path to reduce the amount of light incident on the light-receiving element and increase the optical path efficiency from the laser light-emitting element to the magneto-optical disk surface, the emission power of the laser light-emitting element is also suppressed and the system life is extended. be able to. By reducing the circuit scale, power consumption can also be reduced.
• optical discs irrespective of the type of magneto-optical discs, such as optical discs that perform recording by phase bits or reflectivity changes.
• degree of freedom of the format of the optical disc can be improved, and the added value of the apparatus can be further increased.

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• 1996
  • 1996-01-31 KR KR1019960705157A patent/KR100406477B1/ko not_active Expired - Fee Related
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