USRE39952E1 - Laser power controller and optical disk device - Google Patents

Laser power controller and optical disk device Download PDF

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Publication number
USRE39952E1
USRE39952E1 US11/223,909 US22390999A USRE39952E US RE39952 E1 USRE39952 E1 US RE39952E1 US 22390999 A US22390999 A US 22390999A US RE39952 E USRE39952 E US RE39952E
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Prior art keywords
recording
optical
signal
power
wobble
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US11/223,909
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English (en)
Inventor
Chikashi Inokuchi
Shigeru Furumiya
Yoshiyuki Miyabata
Yuji Hisakado
Atsushi Miyazaki
Toshiya Akagi
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. reassignment MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: AKAGI, TOSHIYA, FURUMIYA, SHIGERU, HISAKADO, YUJI, INOKUCHI, CHIKASHI, MIYABATA, YOSHIYUKI, MIYAZAKI, ATSUSHI
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
    • G11B19/02—Control of operating function, e.g. switching from recording to 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
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/126—Circuits, methods or arrangements for laser control or stabilisation
    • 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
    • G11B7/0053—Reproducing non-user data, e.g. wobbled address, prepits, BCA
    • 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
    • G11B7/006—Overwriting
    • G11B7/0062—Overwriting strategies, e.g. recording pulse sequences with erasing level used for phase-change media
    • 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
    • G11B7/00718—Groove and land recording, i.e. user data recorded both in the grooves and on the lands
    • 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
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/126—Circuits, methods or arrangements for laser control or stabilisation
    • G11B7/1263—Power control during transducing, e.g. by monitoring
    • 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
    • G11B7/0045—Recording
    • 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
    • G11B7/0055—Erasing

Definitions

  • the present invention relates to a laser power control device which is used for recording/reproduction of digital disks and to an optical disk apparatus which uses the laser power control device, and relates to a laser power control device for controlling a laser power and an optical disk apparatus which uses the laser power control device.
  • a recordable/reproducible DVD-RAM disk the inside of the disk is divided into a plurality of zones. The number of rotations is constant within each zone, but is different between different zones. In general, such a system is called a zone CLV.
  • Each zone is divided into a plurality of sectors, and each sector is formed by a data recording region in which information can be recorded and an address region in which the address of the sector has been previously recorded.
  • the data recording region can extend over both a guiding groove region of the disk (hereinafter, referred to as “groove”) and a region between the guiding groove regions (hereinafter, referred to as “land”). Address information is recorded in address portions so that a pair of address portions are offset from each other and each address portion extends over the groove and the land.
  • a single wave corresponding to a divisional component of a clock component (hereinafter, referred to as a “wobble”) is formed in an address region and a data recording region while cutting a disk.
  • the wave component is detected as a tracking error signal.
  • FIG. 11 is a block diagram of a conventional optical disk recording/reproducing device 700 .
  • reference numeral 1 denotes a motor
  • reference numeral 2 denotes an optical disk
  • reference numeral 3 denotes an optical head
  • reference numeral 4 denotes a reproduction signal/servo signal detection circuit for generating a reproduction signal, a focus error signal, and a tracking error signal from an output signal obtained from the optical head 3
  • reference numeral 5 denotes focus/tracking control means for controlling the optical head 3 by using a servo signal from the reproduction signal/servo signal detection circuit 4 and for controlling the motor 2
  • reference numeral 6 denotes a reproduction signal binarizing circuit for binarizing the reproduction signal
  • reference numeral 7 denotes a demodulator for demodulating the binarized reproduction signal to generate reproduction data
  • reference numeral 8 denotes a laser driving circuit for driving a laser which is a light source of the optical head 3
  • reference numeral 9 denotes a recording signal generation circuit for generating
  • An output signal read out from the optical disk 2 by the optical head 3 is supplied to subsequent process circuits as a reproduction signal, a focus error signal, and a tracking error signal by the reproduction signal/servo signal detection circuit 4 .
  • the focus error signal and the tracking error signal are supplied to the focus/tracking control means 5 .
  • the optical head 3 is controlled by the focus/tracking control means 5 so as to follow the wavering of the disk surface and decentration of the disk.
  • the reproduction signal is supplied to the reproduction signal binarizing circuit 6 , and the binarized data sequence and a read clock which is in synchronization with the data are output to the demodulator 7 .
  • the reference clock generator 14 generates a reference clock which is necessary for modulating/demodulating data to be recorded/reproduced by this apparatus.
  • the demodulator 7 performs modulation using the supplied binarized data sequence and the read clock according to a demodulation rule, and outputs the demodulated data to the error correction/address detection device 13 using the reference clock.
  • the output reproduction data is supplied to the subsequent error correction/address detection device 13 , and an address position on a track is detected by the detection device 13 .
  • An address detection signal is supplied to the gate signal generator 12 , and the gate signal generator 12 uses this signal as a position reference on the track to generate, using the gate signal, a signal which is necessary during recording/reproduction.
  • Data to be recorded is converted by the modulator 10 into a data sequence to be recorded according to a modulation rule.
  • the data sequence obtained by the conversion is further converted by the recording signal generation circuit 9 into a signal for modulating laser light, and this signal is supplied to the laser driving circuit 8 .
  • the laser driving circuit 8 modulates the laser light which is a light source of the optical head 3 for recording data on the disk.
  • the recording is performed at a recording power predetermined by the CPU 15 .
  • FIG. 12 An operation of the optical disk recording/reproducing device having the above structure when recording is performed in a sector of a DVD-RAM disk is described with reference to FIG. 12 .
  • Each zone of the DVD-RAM disk is divided into a plurality of sectors, and each sector includes a data recording region in which information can be recorded and an address region in which an address of the sector has been recorded.
  • FIG. 12 a reproduction signal from the disk is shown in FIG. 12 (a); a corresponding tracking error signal is shown in FIG. 12 (b); a read gate signal, which is a representative gate signal necessary for reproduction of data/address, is shown in FIG. 12 (c); a detection signal of the address is shown in FIG. 12 (d); a recording gate signal, which is another representative gate signal necessary for recording is shown in FIG. 12 (e); and an operation gate signal of the modulator is shown in FIG. 12 (g).
  • a signal read out through the optical head 3 is output by the reproduction signal/servo signal detection circuit 4 as a reproduction signal shown in FIG. 12 (a) and a tracking error signal shown in FIG. 12 (b).
  • a read gate signal for reading an address of a target sector L is activated at timing (c)- 2 in FIG. 12 (c) using an address detection signal for a sector previous to the target sector L in which data is to be recorded as a reference.
  • the demodulator 7 performs demodulation based on data from the reproduction signal binarizing circuit 6 and the read clock, and reading of an address is performed in the error correction/address detection device 13 .
  • the detection device 13 When the address has been normally read out, the detection device 13 generates a signal as shown in FIG. 12 (d), and the gate signal generator 12 uses this signal as a reference to activate a recording gate signal and a modulator operation start signal at timings (c)- 1 and (f)- 1 , respectively, for recording data.
  • the laser driving circuit 8 is placed into a recording state, and accordingly, the modulator operation start signal is activated, whereby the modulation of data is started, and the recording signal generation circuit 9 generates a recording signal.
  • the power used for recording is generally set through learning.
  • FIG. 13 is a flowchart showing an example of learning of the recording power.
  • learning for a recording power Popt and learning for an erasing power Peopt, are performed for setting the recording power.
  • an interim erasing power Pe 1 an d an interim recording power Pw 1 are provided.
  • the recording power Pw 1 is set to a value sufficiently lower than an optimum recording power
  • the erasing power Pe 1 is set to a value in the vicinity of a value specified in the specification.
  • the apparatus performs recording in any sector at the recording power Pw 1 which is sufficiently lower than an optimum recording power and the erasing power Pe 1 which is in the vicinity of a value specified in the specification, and measurement of the BER (S 105 ).
  • the apparatus determines whether or not the measured BER is smaller than a threshold C 1 (S 106 ). Since the recording power Pw 1 is a low power as described above, it is determined that the measured value is greater than the threshold C 1 (“No” in S 106 ).
  • the apparatus sets the recording power to a value which is equal to the recording power Pw 1 plus a recording power increase Pws (S 107 ), and performs recording (S 104 ), and measures the BER (S 105 ). The apparatus repeats this process and obtains a recording power Pw when the BER becomes smaller than the threshold C 1 .
  • the product of the obtained recording power Pw and a multiplying factor Cw is used as an optimum recording power Pwopt (S 108 ).
  • the apparatus uses the optimum recording power Pwopt determined as described above so as to obtain an optimum erasing power Peopt.
  • the apparatus performs recording at the erasing power Pe 1 which is in the vicinity of a value specified in the specification (S 109 ), and measurement of the BER (S 110 ). Then, it is determined whether or not the BER exceeds a threshold C 2 (S 111 ).
  • the erasing power Pe 1 is reduced by an erasing power decrease Pes (S 112 ), and the steps S 109 and S 110 are repeated. During these steps, the erasing power Pe when the BER exceeds the threshold C 2 is obtained.
  • the obtained erasing power Pe is stored as an erasing power variable PeL (S 113 ).
  • the erasing power Pe is reset to the erasing power Pe 1 .
  • the recording is performed at the erasing power Pe 1 (S 114 ).
  • the BER is measured (S 115 ).
  • a predetermined value Pes is added to the erasing power Pe (S 117 ).
  • the erasing power Pe when the BER exceeds the threshold C 2 is obtained.
  • the central value of the erasing power Pe when the BER exceeds the threshold C 2 and the previously obtained erasing power variable PeL is assigned as an optimum erasing power Peopt (S 118 ).
  • the above process is merely an example of the learning for recording power.
  • the above process is performed between the error correction/address detection device 13 and the power control means 11 , whereby an optimum recording power is determined.
  • FIG. 14 is a diagram for illustrating recording by the apparatus on a disk whose optimum recording power is 10 mW.
  • the recording is performed while the laser power is controlled so that the output of the object lens is 10 mW.
  • the transmissivity of a substrate layer is ideally 1 , and accordingly, an effective recording power on a recording layer is 10 mW.
  • the effective recording power on the recording layer is decreased according to the decrease in transmissivity due to the attachment. For example, when the transmissivity is decreased to 0.8, the recording power is decreased to 8 mW. As a result, optimum recording cannot be performed.
  • the apparatus performs recording of data at the recording power determined by the above-described method.
  • control for data recording is the control achieved by keeping the amount of laser light constant.
  • This malfunction is described with reference to FIG. 16 . Since the recording operation is performed as described above, the description thereof is omitted. In a sector in which recording is to be performed, when dirt, such as a fingerprint or the like, is present on the substrate as shown by the slanted lines in FIG. 16 , the effective recording power in that portion is reduced. At this time, when a wobble signal is observed, the signal amplitude thereof is decreased in a portion on which dirt, such as a fingerprint, is present. Typically, the recording power margin of a rewritable optical disk is 10% to 30%. If the light amount is decreased to be smaller than the reduced effective recording power, recording cannot be correctly performed on the disk. Observing the reproduction signal waveform after the recording, the amplitude of the reproduction signal after the recording is reduced in a portion on which dirt, such as a fingerprint, is present. As a result, it becomes difficult to correctly reproduce data.
  • a power control device for controlling a power of a light source of an optical beam directed to an optical medium, includes: a reflected light detector for detecting reflected light from the optical medium when irradiated by an optical beam which is following a track; an arithmetic unit for calculating from the reflected light a transmissivity of light transmitted from a disk surface to a recording layer or an amount of directed light on the recording layer of the medium; and power control means for controlling the power of the light source for emission based on a calculation result produced by the arithmetic unit, whereby the above object is achieved.
  • the optical medium may have a recording track which has been wobble-processed in a disk radius direction; the reflected light detector may extract the wobble signal component from a tracking error signal during recording; and the power control means may control laser power so as to keep an amplitude value of the wobble signal component substantially constant.
  • the reflected light detector may detect an amplitude of the wobble signal component from a tracking error signal obtained when the optical beam follows the track; the arithmetic unit may use the amplitude value of the wobble signal in a calculation; and the power control means may control a single-value control power or a multiple-value control power based on the calculation result of the arithmetic unit.
  • the power control means may control a duration of a recording pulse during recording.
  • the arithmetic unit may calculate a reference value from the detected wobble signal amplitude, and may use the reference value and the wobble signal amplitude in a calculation process.
  • the arithmetic unit may calculate the reference value for each of the attributes of a track, presence/absence of data in the track, recording/reproduction states of an apparatus, and combinations thereof, and may selectively use the reference value according to conditions such as the attributes of a track followed by the optical beam, presence/absence of data in the track, recording/reproduction states of the apparatus, and combinations thereof.
  • the arithmetic unit may correct the reference value and the detected wobble signal amplitude according to the different power and performs a calculation process.
  • the power control means may determine whether control is performed, not performed, or stopped, or changes control modes according to a time period during which control works or an amount of a power to be controlled.
  • the power to be controlled may be used for reproducing data contained in the track.
  • the power to be controlled may be used for recording or erasing data in the track.
  • An optical disk apparatus for recording or reproduction on an optical disk including a track in which a recording region is wobble-processed, comprising: optical means for reading information from the optical disk or recording information in the optical disk: control means for controlling the optical means; signal generation means for generating a tracking error signal indicating a scanning state of the optical means on the track of the optical disk; extraction means for extracting a wobble signal component from the tracking error signal; amplitude detection means for detecting an amplitude of the wobble signal component extracted by the extraction means; a bias generation circuit for generating a bias voltage based on an output of the amplitude detection means; an arithmetic unit for outputting a calculation result obtained from the bias voltage generated by the bias generation circuit and an output voltage of the amplitude detection means according to a predetermined calculation rule; and recording power control means for controlling recording power during recording data, wherein during recording, the recording power is controlled based on the calculation result obtained by the arithmetic unit, whereby the above object is achieved.
  • the optical disk apparatus may be capable of recording data in a guiding groove portion and an inter-guiding groove portion of the optical disk; the optical disk apparatus may further include identification means for identifying whether a track scanned by the optical means is in the guiding groove portion or the inter-guiding groove portion: and the bias generation circuit may generate two types of bias voltages, a bias voltage for recording in the guiding groove portion and a bias voltage for recording in the inter-guiding groove portion, based on an output signal of the identification means.
  • the bias generation circuit may include a low-pass filter and may generate an average value of an output of the amplitude detection means or a bias voltage corresponding to a gradual change in amplitude on the order of a rotational component of a disk.
  • the calculation rule of the arithmetic unit may obtain a difference by subtracting the bias voltage generated by the bias generation circuit from the output voltage of the amplitude detection means; may assume the voltage generated by the bias generation circuit as being “1” and obtains a ratio of the difference to the voltage generated by the bias generation circuit, and according to the result, a current laser emission value is output as it is, or a value equivalent to the ratio of the difference is added to or subtracted from the current laser emission value which is assumed as being “1”, and a value obtained by the addition/subtraction is output as a result.
  • the optical disk apparatus may further include optimum power detection means for detecting an optimum power during recording, wherein an amplitude of a wobble signal component may be detected while recording is performed at the optimum power determined by the optimum power detection means, and power control is performed based on the calculation result of the arithmetic unit.
  • recording may be performed only with the optimum power determined by the optimum power detection means, and an average value of a wobble signal amplitude voltage during the recording may be used as an optimum bias voltage or an initial value of the bias voltage.
  • power control may be conducted based on the calculation result of the arithmetic unit so as to perform a recording operation again.
  • the apparatus may provide a cautionary alarm about such being an abnormality of the optical disk or the apparatus.
  • the apparatus may provide a cautionary alarm about such being as an abnormality of the optical disk or the apparatus.
  • the calculation rule of the arithmetic unit may be a difference between the bias voltage generated by the bias generation circuit and the output voltage of the amplitude detection means.
  • the calculation rule of the arithmetic unit may assume that the bias voltage generated by the bias generation circuit is “1”, may calculate a positive square root of the output voltage generated by the amplitude detection means, and may provide a difference between a value of the positive square root and “1” as a calculation result.
  • the calculation rule of the arithmetic unit may assume that the bias voltage generated by the bias generation circuit as being “1”, may calculate a positive square root of the output voltage generated by the amplitude detection means, and may provide a reciprocal of the positive square root as a calculation result.
  • the arithmetic unit may generate a calculation result when a difference between the bias voltage generated by the bias generation circuit and the output voltage generated by the amplitude detection means exceeds a predetermined range; and the recording power control means may conduct power control based on the calculation result of the arithmetic unit.
  • the optical disk apparatus may further include optimum power detection means for detecting an optimum recording power during recording, wherein the recording power control means may detect an amplitude of a wobble signal component while recording is performed at an optimum power determined by the optimum power detection means, and may conduct power control based on the calculation result of the arithmetic unit.
  • a threshold may be provided for the calculation result obtained based on the detected wobble signal amplitude and the apparatus may detect that the calculation result exceeds the threshold or that the calculation result exceeds the threshold for a predetermined time period, whereby the apparatus may detect an abnormal state in the control means for controlling the optical means and changes its operation state.
  • the optical disk apparatus may read information from or records information in multiple types of disks; the optical disk apparatus may include detection means for detecting the type of disk; and the optical disk apparatus may conduct/may not conduct power control for the light source of the optical beam based on the calculation result, or may change an operation mode according to the type of disk detected by the detection means or a duration of recording/reproduction of data or a duration of power control.
  • a wobble signal included in a tracking signal is extracted to detect a signal amplitude thereof, whereby dirt on a disk substrate or a focusing state of the apparatus is detected.
  • power control is conducted according to the amplitude, information, whereby reliability of the apparatus during recording of data can be improved.
  • an operation for checking recorded data is performed. Only when there is an error in the written data, power control is conducted based on amplitude information of a wobble signal component, and a rewriting operation is performed.
  • the present invention is applied to the minimum of data that the apparatus failed to write and that need to be rewritten, whereby reliability of recorded data can be improved.
  • the apparatus when a recording operation is performed at a power exceeding a predetermined range, the apparatus provides a cautionary alarm, whereby a user of the apparatus is informed of an abnormality of the apparatus or disk.
  • a portion recorded at the power is treated as being inappropriate for recording, and a verifying operation is omitted, whereby a processing speed can be increased.
  • FIG. 1 is a block diagram of an optical disk recording/reproducing device according to embodiment 1.
  • FIG. 2 is a chart for describing an operation of the optical disk recording/reproducing device according to embodiment 1.
  • FIG. 3 is a block diagram of an optical disk recording/reproducing device according to embodiment 2.
  • FIG. 4 is a diagram for illustrating a recording principle according to embodiment 2.
  • FIG. 5 is a block diagram of an example of an arithmetic unit according to embodiment 2.
  • FIG. 6 is a block diagram of an example of another arithmetic unit according to embodiment 2.
  • FIG. 7 is a graph showing a laser emission waveform in a case where the set power is a single value according to embodiment 2.
  • FIG. 8 is a graph showing a laser emission waveform in a case where the set power is a multiple value according to embodiment 2.
  • FIG. 9 is a graph showing a laser emission waveform in a case where the pulse width is controlled according to embodiment 2.
  • FIG. 10 is a diagram for illustrating recording tracks of a DVD-RAM according to embodiment 2.
  • FIG. 11 is a block diagram of a conventional optical disk recording/reproducing device.
  • FIG. 12 is a chart for describing an operation of the conventional optical disk recording/reproducing device.
  • FIG. 13 is a flowchart of a method for determining a suitable recording power of the optical disk recording/reproducing device.
  • FIG. 14 is a diagram for illustrating a recording operation of the conventional optical disk recording/reproducing device.
  • FIG. 15 is a diagram for illustrating a reproducing operation of the conventional optical disk recording/reproducing device.
  • FIG. 16 is a chart for describing an operation of the conventional optical disk recording/reproducing device.
  • FIGS. 1 and 2 embodiments of the present invention will be described with reference to FIGS. 1 and 2 .
  • FIG. 1 shows a block diagram of an optical disk recording/reproducing apparatus of the present invention.
  • elements 1 to 15 have the same structures as the conventional structures, and accordingly, the description thereof is omitted.
  • Reference numeral 16 denotes an amplifier/filter for extracting a wobble signal component from a tracking error signal output from the reproduction signal/servo signal detection circuit 4 ;
  • reference numeral 17 denotes an envelope detection circuit for detecting the amplitude of a wobble signal which is an output signal of the amplifier/filter 16 ;
  • reference numeral 18 denotes a bias generation circuit for using an output of the envelope detection circuit to generate a target voltage;
  • reference numeral 19 denotes an arithmetic unit for outputting an operation result obtained from voltages generated by the bias generation circuit 18 and the envelope detection circuit 17 according to a predetermined algorithm;
  • reference numeral 20 denotes recording power setting means capable of setting a power in the laser driving circuit 8 based on the set power of a CPU 22 and an operation result of the arithmetic unit 19 .
  • a signal read out through the optical head 3 is output by the reproduction signal/servo signal detection circuit 4 as a reproduction signal shown in FIG. 2 (a) and a tracking error signal shown in FIG. 2 (b).
  • the amplifier/filter 16 extracts only a wobble signal component from the tracking error signal.
  • FIG. 2 (c) shows a wobble signal.
  • the arithmetic unit 19 receives an envelope signal of the wobble (solid line of FIG. 2 (d)) and an output voltage of the bias generation circuit 18 (broken line of FIG. 2 (d)). As a result, the arithmetic unit 19 outputs a voltage as shown in FIG. 2 (e).
  • an operation in the arithmetic unit 19 is a simple difference detection.
  • the difference between an output voltage of the bias generation circuit 18 and an output voltage of the envelope detection circuit 17 is calculated, and what percentage of the output voltage of the bias generation circuit 18 , which is assumed as being “1”, is equal to the difference is calculated and output as a calculation result.
  • a peak value of the wobble envelope signal a direct voltage which has been obtained by processing the wobble envelope signal with a filter having a large time constant and which varies according to the rotation of the disk, or the like, can be used.
  • the recording power is controlled by adding the output of the arithmetic unit 19 to the recording power.
  • recording is performed at an increased recording power as shown in FIG. 2 (f). Since it is a matter of course that, in an address portion, the emission power of a laser is forcibly reduced to a reproduction level, the output of the arithmetic unit 19 exhibits a large voltage value; however, the power of the laser is at a reproduction level.
  • FIG. 2 (g) shows a wobble envelope signal which is actually detected at the controlled power. During recording of data, the recording power is controlled so that this level is substantially equal to the output of the bias generator.
  • FIG. 2 (h) a reproduction signal of data recorded under the above control is shown in FIG. 2 (h).
  • the present embodiment has been described with a calculation in the arithmetic unit 19 being a simple difference detection. However, it is possible to construct an arithmetic unit such that in the case where the amplitude variation of the wobble signal is large even during a normal recording operation, the calculation result is output only when the difference between the inputs of the arithmetic unit 19 exceeds a threshold, and when the difference is below the threshold, the “100% (no control)” value is output.
  • the operation in the arithmetic unit 19 is not limited to a simple difference detection.
  • the output of the bias generation circuit 18 is assumed as being “1”, the square root of an output value of the envelope detection circuit 17 is obtained, a subtraction of this square root from “1” is added to “100%”, and the result of this addition is used as an output.
  • the present invention provides an apparatus in which the amplitude of a wobble signal is detected during a recording operation at a set optimum recording power, the signal is compared with a level recognized as being optimum, and a recording power is controlled using the difference as an increase of the recording power, whereby highly reliable recording can be performed even when dirt is attached on the substrate of the disk.
  • the amplitude voltage of the wobble signal can be recognized as constant among various apparatuses.
  • the amplitude voltage can be used as a target value to constantly control the optimum recording power.
  • the description has been focused on dirt on a substrate of the disk, such as a fingerprint or the like.
  • the amplitude of the wobble signal can be decreased due to defocusing or off-tracking of an optical disk or due to tilting caused when mounting an optical head or tilting caused by a curvature of the disk.
  • the wobble signal malfunction of the apparatus can be detected as well as dirt on the substrate of the disk, etc.
  • the CPU 22 may read from the power control means 20 power added by the power control based on the amplitude of the wobble signal. In this way, it is possible to inform a user of a malfunction of an optical disk or an apparatus when the value of the power exceeds a threshold.
  • Embodiment 2 of the present invention is shown in FIG. 3 .
  • reference numeral 101 denotes a motor
  • reference numeral 102 denotes an optical disk
  • reference numeral 103 denotes an optical head for converting reflected light from the disk into an electric signal and outputting the signal to a reproduction signal/servo signal detection circuit 104
  • reference numeral 104 denotes the reproduction signal/servo signal detection circuit for generating a reproduction signal, a focus error signal, a tracking error signal 1 , and a tracking error signal 2 from an output signal obtained from the optical head 103
  • reference numeral 105 denotes focus/tracking control means for controlling the optical head 103 by using a servo signal from the reproduction signal/servo signal detection circuit 104 , for controlling the motor 101 , and for notifying a reference value generator 117 about the polarity of a track presently being scanned
  • reference numeral 106 denotes a reproduction signal detecting/binarizing circuit for detecting the presence/absence of data and notifying the reference value generator 117 of such and for binarizing the reproduction signal
  • An output signal read out from the optical disk 102 by the optical head 103 is supplied by the reproduction signal/servo signal detection circuit 104 to a subsequent processing circuit as a reproduction signal, a focus error signal, a tracking error signal 1 , and a tracking error signal 2 .
  • the focus error signal and the tracking error signal 1 are supplied to the focus/tracking control means 105 , and the focus/tracking control means 105 controls the optical head 103 so as to follow the wavering of the disk surface and decentration of the disk.
  • tracking of the optical head 103 is controlled so as to be in one of the guiding groove portion and the inter-guiding groove portion.
  • a signal indicating the guiding groove portion or the inter-guiding groove portion is supplied to the reference value generator 117 as one of the attributes of the track.
  • the reproduction signal is supplied to the reproduction signal detecting/binarizing circuit 106 , and a binarized data sequence and a read clock synchronized with the data are output to the demodulator 107 .
  • the presence/absence of a signal is detected and supplied to the reference value generator 117 as one of the attributes of a track being reproduced.
  • the reference clock generator 114 generates a reference clock which is necessary to modulate/demodulate data to be recorded/reproduced in this apparatus.
  • the demodulator 107 performs conversion using the supplied binarized data sequence and the read clock according to a demodulation rule, and outputs the converted data to the error correction/address detection device 113 using the reference clock.
  • the output reproduction data is supplied to the subsequent error correction/address detection device 113 , and the subsequent error correction/address detection device 113 detects an address position on the track.
  • An address signal detection signal is supplied to the gate signal generator 112 , and the gate signal generator 112 uses this signal as a position reference on the track so as to generate a gate signal which is necessary in recording/reproducing using the reference clock.
  • data to be recorded is converted into a data sequence to be recorded by the modulator 110 according to a modulation rule.
  • the data sequence obtained by the conversion is further converted by the recording signal generation circuit 109 into a signal for modulating laser light, and the signal is supplied to the laser driving circuit 108 .
  • the laser driving circuit 108 modulates the laser light which is a light source of the optical head 103 for recording data on the disk.
  • the recording is performed at a recording power determined by the arithmetic unit 118 .
  • the reference value generator 117 receives a polarity signal of the above track, a data presence/absence detection signal, and a recording gate indicating a recording/reproduction state of the apparatus.
  • the reference value generator 117 generates respective reference values from a wobble signal amplitude which is input for each of the combinations of the above three signals, and supplies the respective reference values to the arithmetic unit 118 .
  • the arithmetic unit 118 calculates the transmissivity of the disk, and generates a control signal for adjusting a recording power on a recording layer of the disk to be the recording power set by the CPU 115 . In the calculation of the arithmetic unit 118 , a wobble signal amplitude from the disk which is output from the amplifier/bandpass filter/amplitude detection circuit 116 and a value from the reference generator 117 are used.
  • recording power control in a conventional apparatus is to control the emission power of the laser. Therefore, in a portion where an attachment, such as a fingerprint or dust, is present on the disk surface, an effective recording power is insufficient. As a result, an appropriate recording cannot be performed.
  • a wobble signal amplitude is detected from the disk during recording, and the transmissivity of a fingerprint or dust attached on the disk surface is calculated, whereby the irradiation amount of the laser actually illuminating the recording layer is controlled.
  • Pw (mW) denotes the laser recording power at the output of an object lens
  • Tf denotes the transmissivity of an attachment on the disk surface
  • Krw denotes the wobble modulation factor including reflectance
  • T (Wrw/(Pw ⁇ Krw)) 0.5 (3) where Krw is a constant value determined for each disk which is obtained by experiment, and Pw is a known value for an output power.
  • the transmissivity of the disk substrate is obtained. Accordingly, Pw is obtained by expression (1)′ in order to control the required effective power Pwr to be constantly set to the optimum effective recording power Pwrs.
  • a wobble signal amplitude Wrws obtained when recording is performed in a portion with no attachment at an optimum recording power Pws is used as a reference value.
  • the detected wobble amplitude Wrw′ is varied by the power, which is controlled as described above. Therefore, when control formed by a control loop is repeatedly performed, the amplitude of the detected wobble signal or the reference value should be corrected during calculation according to a scaling factor of the power used for determining the reference value for the controlled power.
  • the recording power Pw is the optimum recording power Pws multiplied by 1/Tf, i.e., 1.25.
  • a subsequently detected wobble signal amplitude is 1.25 times greater than the previous signal, and the ratio of the detected wobble signal amplitude to the reference wobble signal amplitude value is 0.64 ⁇ 1.25, i.e., 0.8.
  • the recording power is corrected with the square root of 0.8, such that the recording power becomes 1.12 times greater than the optimum recording power Pws. In this way, the recording power gradually changes without changing the transmissivity of a fingerprint Tf.
  • the recording sensitivity is different between an outer track and an inner track of the disk because of any reason, and an actual recording power Pw is different from an optimum recording power Pws on a track in which a reference value Wrws has been obtained.
  • the reference value Wrws is obtained using an optimum recording power Pws on the inner track.
  • the apparatus performs a retrieving operation, and performs control in the outer track.
  • the scaling factor of an optimum recording power in this track is Cp (Cp ⁇ 1), and other parameters such as Krw, etc., are the same
  • the detected wobble signal amplitude is Cp times greater than the reference wobble signal amplitude, and accordingly, the power correction is performed by a factor of 1/(the square root of Cp).
  • the power correction is performed by a factor of 1/(the square root of Cp).
  • recording cannot be performed at optimum power.
  • a value obtained by multiplying the reference value by a scaling factor of a control power used for actual recording with respect to the power used for obtaining the reference value can be used in another track as a reference value.
  • FIG. 5 shows an example of an arithmetic unit for controlling the recording power while performing the above correction.
  • the reference value obtained using a recording power Pws is input and multiplied by a correction factor Cp (Pw/Pws) for the above recording power Pw to be controlled.
  • Cp correction factor
  • a detected wobble signal amplitude is multiplied by a detected value of a wobble amplitude (Pw ⁇ 1/Tf n ⁇ 1 ⁇ Tf ⁇ ⁇ Krw) which corresponds to the current laser power (Pw ⁇ 1/Tf n ⁇ 1 ) determined based on the transmissivity of the previous attachment (Tf n ⁇ 1 ), whereby a wobble amplitude corresponding to the recording power Pw is obtained.
  • the normalization is performed by dividing the product of the detected wobble amplitude and the corrected value of the recording power by a correct reference value obtained after the optimum recording power has been modified.
  • Cp ⁇ Pws ⁇ Tf ⁇ ⁇ Krw/Cp ⁇ Pws ⁇ Krw Tf ⁇
  • the transmissivity of the disk is constantly obtained based on the wobble amplitude, whereby the optimum recording power can be successively controlled.
  • a portion on which a recording operation is to be performed is first reproduced at a constant power, and a wobble signal obtained at this time is stored. Then, when the recording operation is actually performed, a target value for a recording power is calculated from the stored wobble amplitude.
  • the calculation is performed solely with a detected wobble amplitude, otherwise, a reference value is determined from the detected wobble signal, and a calculation of the reference value and a wobble amplitude when a fingerprint or dust is present on a disk surface is performed, whereby power can be controlled.
  • the reference value may be varied according to differences in attributes of a track, e.g., differences between a guiding groove portion and an inter-guiding groove portion, a difference in reflectance among disks, a difference in reflectance due to the presence/absence of recorded data in a track, etc.
  • the reference value it is sometimes necessary to change the reference value by determining a reference signal according to information in guiding groove/inter-guiding groove portions of a track which is being scanned by control means, a data record presence/absence signal in a reproduction signal processing circuit, or attributes of each track which are determined according to the recording/reproduction state of the apparatus.
  • a reference signal As possible means for changing the reference value, there is a method in which an A/D converter is used for obtaining a reference value, digital outputs of the converter for the respective attributes are averaged, and this averaged value is adjusted for each of the combinations of the attributes.
  • control has been described with an example of recording power control. However, it is needless to say that the above control can be applied to power control during reproduction.
  • a problem which occurs in a conventional apparatus during reproduction is that when reproduction is performed at a constant laser power, the transmissivity of light on a disk surface is partially varied due to a fingerprint, dust, or the like, attached thereon, and accordingly, variation in a DC component or an amplitude of a reproduction signal is caused.
  • a method for controlling the power by stabilizing the amplitude of the reproduction signal is described.
  • Vrfs Pps ⁇ Krf ⁇ T ⁇
  • Pps denotes an optimum laser power for reproduction in the portion with no attachment
  • T denotes the transmissivity of a disk substrate in the portion with no attachment
  • Tf denotes the transmissivity of the attachment
  • Krf denotes a modulation factor
  • Vrfs Pps ⁇ Krf (8)
  • Vrf′ Pps ⁇ Krf ⁇ Tf ⁇ (9)
  • the power can be controlled.
  • the wobble signal amplitude Wrps is output as a reference value for reproduction from the reference value generator 117 to the arithmetic unit 118 .
  • the arithmetic unit 118 performs the above calculations to control the power control during reproduction, whereby a reproduction amplitude can be kept constant.
  • a reproduction signal amplitude it is possible to use a reproduction signal amplitude for power control.
  • a wobble signal amplitude is preferable because when the power control is performed based on the reproduction signal, if an unrecorded sector is present among the recorded sectors, a problem where the control cannot be performed, or the like, may be caused.
  • FIG. 6 An example of a calculation block for performing the above power control calculations for reproduction is shown in FIG. 6 .
  • this structure (details thereof are omitted)
  • a subsequent recording power is calculated while correcting a current emission power.
  • Control for keeping the amplitude of a reproduction signal constant can be achieved based on the above calculations.
  • such a control for keeping the amplitude of a reproduction signal constant may produce an excessive emission power on a recording face of a disk.
  • the apparatus it is easy to change operation modes between power control for recording and power control for reproduction according to a command received by the CPU 115 . Furthermore, it is needless to say that the operation mode can be changed according to the state of the apparatus, a type of a disk with which the apparatus is performing recording/reproduction, the length or time of data to be recorded/reproduced by the apparatus in response to the received command, and the amount of power to be controlled, whereby the reliability of the apparatus can be improved.
  • a pseudo focus error signal or a pseudo tacking error signal caused by such an attachment may make a control operation of optical means or control means thereof unstable.
  • the transmissivity obtained by calculation based on a detected wobble is monitored; when the value of this transmissivity exceeds a predetermined value, or when the value of this transmissivity exceeds a predetermined value for a predetermined time period, an attachment is detected on a disk surface, and the operation state of the control means is changed, e.g., an operation range of the control means is narrowed, the control state is held, etc.
  • FIG. 7 is a graph showing a laser emission waveform in the case where the set power is a single value.
  • FIG. 8 is a graph showing a laser emission waveform in the case where the set power assumes multiple values.
  • the power control means 111 controls a single-value or multiple-value control power based on a calculation result or the arithmetic unit 118 .
  • FIG. 9 is a graph showing a laser emission waveform in the case where the pulse width is controlled.
  • the power control means 111 controls the duration of a recording pulse during recording as shown in FIG. 9 .
  • FIG. 10 is a diagram for illustrating recording tracks of a DVD-RAM.
  • the optical disk has a guiding groove track and an inter-guiding groove track.
  • An optical disk apparatus can record data in both the guiding groove track and the inter-guiding groove track.
  • the optical disk apparatus includes identification means for identifying whether a track scanned by optical means is a guiding groove track or an inter-guiding groove track.
  • a bias generation circuit generates a bias voltage for recording in a guiding groove track and a bias voltage for recording in an inter-guiding groove track.
  • the present invention provides the following effects:
  • a wobble signal amplitude detected during recording of data is compared with a wobble signal amplitude detected during normal recording at an optimum power, the difference therebetween is used for controlling recording power, whereby optimum recording can be performed even when dirt, such as a fingerprint, is present on a disk surface. Furthermore, an effective, optimum recording is possible even when decrease in effective recording power is caused by defocusing, off-tracking, or tilting due to external factors outside the apparatus.
  • the amplitude voltage of a wobble signal is controlled to be a target voltage, whereby an optimum recording power can be constantly controlled.
  • a desired power for recording/reproduction is calculated from an amount of reflected light, whereby the power can be controlled. Therefore, influence of a fingerprint or dust on performance of the apparatus for recording/reproducing data can be minimized. Moreover, a calculation result exceeding a predetermined threshold is detected, and an abnormality on a disk surface is then detected, whereby operation of optical means and control means thereof can be kept stable.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Optical Head (AREA)
US11/223,909 1998-08-20 1999-08-20 Laser power controller and optical disk device Expired - Fee Related USRE39952E1 (en)

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PCT/JP1999/004506 WO2000011668A1 (fr) 1998-08-20 1999-08-20 Unite de commande de puissance laser et dispositif a disque optique

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DE69923014T2 (de) 2006-04-13
EP1109161A4 (de) 2002-07-31
KR100423824B1 (ko) 2004-03-22
EP1109161B1 (de) 2004-05-12
KR20010072820A (ko) 2001-07-31
US6621779B1 (en) 2003-09-16
CN1324480A (zh) 2001-11-28
DE69923014D1 (de) 2005-02-03
DE69917291T2 (de) 2004-09-09
WO2000011668A1 (fr) 2000-03-02
EP1403858B1 (de) 2004-12-29
EP1109161A1 (de) 2001-06-20
DE69917291D1 (de) 2004-06-17
EP1403858A3 (de) 2004-05-06
EP1403858A2 (de) 2004-03-31
JP4413432B2 (ja) 2010-02-10
CN1206631C (zh) 2005-06-15

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