JP2010009730A - Optical disk device - Google Patents

Abstract

An optical disc apparatus capable of forming a normal recording mark when recording on a high-density optical disc at high speed.
When an ACC unit sends a signal for generating a drive current for driving a semiconductor laser to a laser drive circuit, an auxiliary circuit assists the rise when the drive current rises. A signal for supplying current is sent, and the laser drive circuit receives the signal from the ACC and the signal from the auxiliary circuit to generate the laser drive current Id, so that the recording waveform approaches the desired rectangular wave and normal recording is performed. A mark can be formed.
[Selection] Figure 4

Description

  The present invention relates to an optical disc apparatus that handles optical discs such as CD, DVD, BD, or HD DVD.

  A plurality of types of recording density optical disks called CD (Compact Disc) standards and DVD (Digital Versatile Disk) standards are already widely used. In recent years, by recording information using laser light of a blue-violet wavelength, Furthermore, BD (Blu-ray Disc) standard and HD DVD (High Definition Digital Versatile Disk) standard optical disks, which are ultra-high density optical disks with higher recording density, have been put into practical use.

  When data is recorded on the recordable optical disk among the above optical disks, it is necessary to record with an appropriate recording power. FIG. 6 is a diagram illustrating an example of a recording waveform of laser light. When recording a recording mark on the recording layer of the optical disc, it is recorded by a first pulse, a multi-pulse, and a last pulse. In the case of the shortest mark, recording may be performed with only the first pulse. There are also short marks recorded with the first and last pulses. Generally, recording is performed with a first pulse, a plurality of multi-pulses, and a last pulse.

  As for the magnitude of the pulse, three types of control of peak power (Peak Power) Po, erase power (Erase Power) Pe, and bottom power (Bottom Power) Pb are important. The peak power and the erase power respectively represent the power of the laser beam for setting the recording layer (for example, phase change recording layer) of the optical disc to an amorphous state (recording state) and a crystalline state (erasing state). Used for recording and erasing (or recording of the space portion). A non-crystalline state can be obtained by irradiating the recording layer with a high-power laser light pulse to raise the temperature to the melting point or higher and quenching from the molten state. In addition, a crystalline state can be obtained by irradiating a non-crystalline state with medium power laser light and raising the temperature to a crystallization temperature or higher. By controlling the temperature of the recording layer with the power of the laser light applied to the recording layer, the state of the recording layer can be changed to a crystalline state or an amorphous state. In particular, it is important to control peak power when forming a recording mark.

With the demand for higher recording / reproducing speeds, demands for double speed and quadruple speed are increasing in BD standard and HD DVD standard optical disks, which are ultra-high density optical disks. When recording on a BD standard or HD DVD standard optical disc at high speed, it tends to be difficult to form the vicinity of the mark edge in recording on a short mark. In order to solve this problem, test writing is performed on the PCA (Power calibration area) of the optical disc, and this data is reproduced, and the record mark is recorded based on the data of OPC (Optimum Power Control) processing that determines the optimum recording power. A method for correcting the intensity of the recording pulse for each length is considered. (For example, refer to Patent Document 1.)
JP 2004-062919 A

  When recording at high speed, it tends to be difficult to form the vicinity of the mark edge portion in recording a short mark. As one of the causes, there is a problem that when the speed is high, the interval between the recording pulses becomes short and the case where the recording power does not reach the predetermined peak power Po is likely to occur.

  FIG. 7 shows how the recording power does not reach the peak power Po. The waveform shown by the alternate long and short dash line is the desired recording waveform, but it does not rise sharply as shown by the solid line at the rising part of each pulse, and when it reaches Po after time has passed, or a multi-pulse with a short pulse width Then, Po may not be reached. In this case, the state of forming an amorphous state is not completely achieved, and normal mark recording cannot be performed. In addition to adjusting the magnitude of Po, it is desirable to generate a recording waveform that is the same as or close to the set Po.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an optical disc apparatus capable of forming a normal recording mark when recording on a high-density optical disc at a high speed. .

  In order to achieve the above object, an optical disc apparatus according to the present invention is an optical disc apparatus that records or reproduces information by irradiating an optical disc with laser light, the semiconductor laser that irradiates the optical disc with laser light, and the recording of the optical disc. An optical pickup having an objective lens for condensing the laser beam on a surface and a photodetector having a light receiving unit for receiving reflected light from the optical disc; and a laser power of the laser beam of the semiconductor laser. Control means for controlling is provided, and the control means has auxiliary means for assisting the rising current of the laser beam.

  According to the present invention, normal recording marks can be formed when recording on an optical disc at high speed at a high speed.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an optical disc apparatus according to an embodiment of the present invention. The optical disc 2 is a CD-type, DVD-type, BD-type, or HD DVD-type read-only or recordable optical disc. For example, the DVD system includes a read-only DVD-Video, a DVD-ROM (Read Only Memory), a recordable DVD-R (Recordable) / RW (Rewritable) / RAM (Random Access Memory), and the like. The optical disk 2 is rotationally driven by a disk motor 3. The disk motor 3 is controlled by a disk motor control circuit 4.

  Information recording and reproduction with respect to the optical disc 2 are performed by the optical pickup 5. The optical pickup 5 is provided with an objective lens 6. The objective lens 6 can be moved in the focusing direction (the optical axis direction of the lens) by driving a focusing actuator 7, and tracking can be performed by driving a tracking actuator 8. It is possible to move in the direction (the direction perpendicular to the optical axis of the lens and the radial direction of the optical disk).

  The recording data generation circuit 9 adds an error correction code to the data supplied from the host device 26 via the interface circuit 25 at the time of information recording, adds a synchronization code, etc. to change to a recording format, further modulates, and modulates Provided data to the laser control circuit 10. The laser control circuit 10 supplies a writing signal to the laser diode 11 in the optical pickup 5 based on the data supplied from the recording data generation circuit 9 during information recording (mark formation). Details of the laser control circuit 10 will be described later.

  The laser diode 11 includes a laser diode 11a for CD having a wavelength of about 780 nm (nano meter), a laser diode 11b for DVD having a wavelength of about 650 nm, and a laser diode 11c for BD or HD DVD having a wavelength of about 405 nm. Depending on the type of optical disc loaded in the optical disc apparatus, the laser beam is selected and emitted according to the signal supplied from the laser control circuit 10.

  Laser light emitted from the laser diode 11 is irradiated onto the optical disc 2 through the optical unit 12 and the objective lens 6. The reflected light from the optical disk 2 of the laser light emitted from the laser diode 11 is guided to the photodetector 13 through the objective lens 6 and the optical unit 12. An output signal from the photodetector 13 is supplied to the RF amplifier 15.

  The laser light monitor detector 14 branches a part of the laser light generated by the semiconductor laser diode 11 from a half mirror (not shown) in the optical component 12 by a certain ratio, and detects a light reception signal substantially proportional to the irradiation power, The detected light reception signal is supplied to the laser control circuit 10. The laser control circuit 10 acquires the light reception signal supplied from the laser light monitor detector 14 and is preset by a CPU (Central Processing Unit) 22 which is a control unit of the entire optical disc apparatus 1 based on the acquired light reception signal. The semiconductor laser diode 11 is controlled to emit light with the reproduction power (irradiation power) during reproduction, the recording power during recording, and the erasing power during erasure.

  The RF amplifier 15 processes the detection signal from the light detector 13, a focus error signal (FE signal) indicating an error from just focus, and a tracking error signal (error indicating the error between the laser beam spot center and the track center). TE signal) and a reproduction signal (RF signal) are generated, and the generated FE signal, TE signal, and RF signal are supplied to the A / D converter 16. When the detection signal from the photodetector 13 is processed, the RF amplifier 15 sets the parameters for generating the signal according to the type of the laser diode 11 used to an appropriate value and generates the signal. To do. A signal output from the A / D converter 16 is supplied to the CPU 22 and the like via the bus 21.

  The focus / tracking control circuit 17 generates a focus control signal and a tracking control signal according to the FE signal and the TE signal supplied from the A / D converter 16, and outputs them to the focusing actuator 7 and the tracking actuator 8 to output the objective lens 6. Drive. As a result, focusing servo in which the laser beam is always just focused on the information recording surface of the optical disc 2 and tracking servo in which the laser beam is always traced on the track formed on the optical disc 2 are performed.

  The RF signal is converted into a digital signal by the A / D converter 16 and supplied to the PLL circuit 18 as channel bit data. The PLL circuit 18 generates a clock synchronized with data from the data supplied from the A / D converter 16 and a channel data signal in units of channel bits, and outputs the data to the data reproduction circuit 19. The data reproduction circuit 19 decodes the format, demodulates the channel data signal to reproduce the byte data, and the reproduced data is output to the error correction circuit 20. The error correction circuit 20 performs error correction using the error correction code to which the reproduction data is given, and then outputs it to the host device 26 via the interface circuit 25.

  The disk motor control circuit 4, recording data generation circuit 9, laser control circuit 10, A / D conversion circuit 17, focus / tracking control circuit 17, PLL circuit 18, data reproduction circuit 19, error correction circuit 20, etc. Via the CPU 22 which is a control unit.

  The CPU 22 comprehensively controls the optical disc recording / reproducing apparatus 1 in accordance with an operation command supplied from the host device 26 via the interface circuit 25. Further, the CPU 22 uses a RAM (Random Access Memory) 23 as a work area such as a buffer memory at the time of recording and reproduction, and performs predetermined control according to a program stored in a ROM (Read Only Memory) 24.

  The CPU 22 records the data by changing the recording power of the laser beam in the trial writing area of the optical disc 2 by the recording means constituted by the recording data generating circuit 9, the laser control circuit 10, the optical pickup 5, and the like. The optimum recording power is recorded on the data recorded by changing the recording power of the laser light on the basis of the reproduction signal obtained by the reproducing means constituted by the optical pickup 5, the RF amplifier 15, the A / D conversion circuit 17, and the like. Has a function to determine.

  When the CPU 22 receives a command including a recording operation from the host device 26, the CPU 22 executes OPC. Alternatively, OPC may be executed if the optical disk 2 is loaded in the optical disk apparatus 1 and the optical disk 2 is a recording type after the determination of the optical disk 2 as an initial operation.

  FIG. 2 is a block diagram showing the internal configuration of the laser control circuit 10. The laser control circuit 10 includes a laser drive circuit 41, an S / H unit 42, an APC unit 43, an ACC unit 44, an auxiliary circuit 45, and a control unit 46.

  The laser drive circuit 41 receives a voltage signal from the APC unit 43 or the ACC unit 44 based on control from the control unit 46, and outputs a drive current Id to the semiconductor laser 11. The S / H (sample / hold) unit 42 samples the optical power detection current Ip (monitor signal) from the laser light monitor detector 14, holds (holds) it for a predetermined time, and outputs it as a sampling signal.

  An APC (Automatic Power Control) unit 43 and an ACC (Automatic Current Control) unit 44 are used when the semiconductor laser 11 is driven by APC (Automatic Power Control) and ACC (Automatic Current Control). The APC unit 43 and the ACC unit 44 are switched by the control unit 46.

  The APC unit 43 is an automatic power constant value control circuit that controls the laser driving circuit 41 based on the sampling signal from the S / H unit 42 so that the optical power from the semiconductor laser 11 becomes constant. The APC unit 43 sends a voltage signal that makes the optical power from the semiconductor laser 11 constant to the laser drive circuit 41. The laser drive circuit 41 receives the voltage signal and supplies a drive current Id to the semiconductor laser 11. At this time, the drive current Id is not necessarily constant. The APC unit 43 includes a peak APC unit and an erase APC unit (not shown). The peak APC unit and the erase APC unit drive the semiconductor laser 11 by APC so that the peak power and the erase power are obtained, respectively.

  The ACC unit 44 is an automatic current constant value control circuit that controls the laser drive circuit 41 so that the drive current Id to the semiconductor laser 11 becomes constant. A voltage signal is sent to the laser drive circuit 41 so that the drive current Id to the semiconductor laser 11 is constant. The laser drive circuit 41 receives the voltage signal and supplies a drive current Id to the semiconductor laser 11. At this time, the optical power from the semiconductor laser 11 is not necessarily constant. The ACC unit 44 includes a peak ACC unit and an erase ACC unit (not shown). The peak ACC unit and the erase ACC unit ACC drive the semiconductor laser 11 so that the peak power and the erase power are obtained, respectively.

  When the ACC unit 44 is operating and driving the semiconductor laser 11, the auxiliary circuit 45 generates a drive current for the pulse signal of the drive current sent by the laser drive circuit 41 according to the signal sent by the ACC unit 44. When starting up, a signal for supplying a current to assist this current is sent to the laser drive circuit 41. The laser drive circuit 41 receives the voltage signal from the ACC 44 and the voltage signal from the auxiliary circuit 45 and generates a laser drive current Id.

  FIG. 3 is a diagram illustrating an example of the waveform of the drive current Id. A rectangular waveform having a pulse width (time) Tp rising from the bottom current Ipb to the peak power current Ipo is a desired current waveform. However, in practice, a delay of Td occurs until Ipo is reached. If this delay is small and Td / Tp is small, the adverse effect on the recording is small, but if the ratio is large, it will have an adverse effect. In the case of high-speed recording, in APC control, the signal transmission of the laser light monitor detector 14, the sampling of the optical power detection current Ip (monitor signal) from the laser light monitor detector 14, the S / H unit 52 to the APC unit 43. In the sampling signal or the like, the operation band is over and the delay ratio is increased.

  FIG. 4 is a diagram illustrating a state where an auxiliary current is added by the auxiliary circuit 45. FIG. 4A is a diagram showing an example of the waveform of the drive current Id sent by the laser drive circuit 41 based on the drive signal sent by the ACC unit 44 and the drive signal sent by the auxiliary circuit 45. A rising portion indicated by a broken line corresponds to a waveform in which a delay of Td shown in FIG. 3 occurs. It can be seen that the addition of the auxiliary current shortens the rise time delay to Td1 and approaches a rectangular wave.

  FIG. 4B is a diagram illustrating a Po control signal transmitted by the peak ACC unit of the ACC unit 44. Based on this signal, the laser drive circuit 41 generates a laser drive current that is the basis of the peak power. FIG. 4D is a diagram showing a Pe control signal transmitted by the erase ACC unit. This indicates that the erase power is not transmitted at this timing.

  FIG. 4C is a diagram showing an auxiliary current signal sent from the auxiliary circuit 45. The auxiliary circuit 45 sends a signal for supplying an auxiliary current over a total time of the first time T1 before the rising time of the Po control signal and the second time T2 after the rising time. As a result, a signal for supplying an assisting current is transmitted over a total time of the first time T1 before the rise time of the semiconductor laser drive current by the ACC and the second time T2 after the rise time. become. The delay time Td1 is appropriately set by adjusting T1 and T2. The first time T1 may be 20% or less of Tp, and may be in the range of 10 to 20%. The second time T2 is desirably set to 50% or less of the pulse width Tp. Further, the magnitude of the drive current based on the signal of the auxiliary circuit 45 is desirably 20% or less of the peak power current generated by the ACC unit 44 and is equal to or less than the following.

  FIG. 5 is a diagram showing a recording waveform of the laser beam when an auxiliary current is added by the auxiliary circuit 45. Compared with FIG. 7, each pulse approaches a desired rectangular wave, and normal and stable recording can be performed.

  As described above, when the ACC unit 44 sends a signal for generating a drive current for driving the semiconductor laser to the laser drive circuit 41, the auxiliary circuit 45 causes the time for the drive current to rise. The laser driving circuit 41 sends a signal for supplying a current for assisting the rising over the total time of the first time before the rising time and the second time after the rising time, and the laser driving circuit 41 receives the signal from the ACC 44 and the auxiliary circuit 45. The laser drive current Id is generated in response to the signal from. By doing so, the recording waveform approaches a desired rectangular wave, a normal recording mark can be formed, and normal and stable recording can be performed when recording at a high speed on a high-density recording medium. it can.

Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

1 is a block diagram showing an optical disc apparatus according to an embodiment of the present invention. The block diagram showing the internal structure of a laser control circuit. The figure which shows the example of the waveform of the drive current Id. The figure which shows the state in which the auxiliary current by the auxiliary circuit was added. The figure which shows the recording waveform of a laser beam when the auxiliary current by the auxiliary circuit 45 is added. The figure which shows the example of the recording waveform of a laser beam. The figure which showed a mode that recording power did not reach | attain peak power Po.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Optical disk 5 Optical pick-up 6 Objective lens 10 Laser control circuit 11 Laser diode 22 CPU
41 Laser Drive Circuit 42 S / H Unit 43 APC Unit 44 ACC Unit 45 Auxiliary Circuit 46 Control Unit

Claims (5)

An optical disc apparatus for recording or reproducing information by irradiating an optical disc with laser light,
Light having a semiconductor laser for irradiating an optical disk with laser light, an objective lens for condensing the laser light on a recording surface of the optical disk, and a photodetector having a light receiving portion for receiving reflected light from the optical disk With a pickup,
Control means for controlling the laser power of the laser beam of the semiconductor laser;
The optical disc apparatus, wherein the control means includes auxiliary means for assisting a rising current of the laser light. The control means includes a laser driving circuit for supplying a current for driving the semiconductor laser to the semiconductor laser, and an automatic current constant value control circuit for controlling a current value for driving the semiconductor laser to be constant,
2. The auxiliary means sends out a signal for supplying a current for assisting the current when the driving current of the semiconductor laser rises when the automatic current constant value control circuit is operating. Optical disk device.   The auxiliary means sends out a signal for supplying an auxiliary current over a total time of a first time before the rise time of the drive current of the semiconductor laser and a second time after the rise time. 3. The optical disk apparatus according to claim 2, wherein   4. The optical disk apparatus according to claim 2, wherein the auxiliary means sets the magnitude of the current to be supplemented to 20% or less of the magnitude of the driving current of the semiconductor laser.   5. The optical disk apparatus according to claim 3, wherein the auxiliary means sets the second time to 50% or less of a driving time of the driving current of the semiconductor laser.

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