JP2005116049A - Device,method and program for adjusting laser power, optical disk, recording medium with the program recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the control of laser power by eliminating the conventional necessity of monitoring the laser driving currents of at least two points, and calculating efficiency to decide laser power or the like. <P>SOLUTION: A control signal from a CPU 22 is inputted to a laser control circuit 13 and, according to this input signal, a laser control circuit 13 sets the WDAC values of WDAC's 12c and 12d or the WDAC value of the WDAC 12d to a predetermined value, and outputs set power to a timing control circuit 12f for a predetermined time. In this state, the CPU 22 detects a signal from a photodetector 38 via the laser control circuit 13, and adjusts the FSDAC value of an FSDAC 12b to set predetermined power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is applied to a recordable / reproducible optical disc drive using an optical disc as an information recording medium, a laser power adjusting device, an optical disc device, a laser power adjusting method, a laser power adjusting program, and a recording medium recording the program About.

  In recent years, optical disks (CD-R / CD-RW / DVD-R / DVD-RW / DVD + R / DVD + RW) have begun to spread as information recording media in place of magnetic tape. An optical disk is less likely to deteriorate due to repeated reproduction like a magnetic tape and is convenient. Recently, devices for recording information on optical disks (music recording, DVD recorder, PC recording drive) have been widely used. These apparatuses perform recording on a disk using a laser beam, and the recording quality is maintained by using a correctly controlled laser power.

  However, the intensity of light emitted from the laser light changes due to self-heating and the like, and there is a risk that the recording quality may be impaired. Therefore, it is necessary to maintain an optimized laser power. As means for maintaining laser power, APC (Automatic Power Control) control is generally performed. In this APC control, a part of the laser beam is incident on a photodetector (PD), and the laser drive current is controlled using a monitor current generated in proportion to the laser power.

By the way, in a device that emits laser light, for example, an optical pickup device, a D / A converter (DAC) is provided to emit light, and a current necessary to emit laser light is output by the D / A converter. Is done. In a digitally controlled system, the maximum drive current amount of the D / A converter may be set by a separately provided D / A converter. This D / A converter may be referred to as a full-scale DAC. By adjusting the maximum amount of current required to drive the laser by the full-scale DAC, the setting resolution of the DAC that drives the laser can be set optimally.
Japanese Patent Laid-Open No. 11-250459 Japanese Patent No. 3233094

  FIG. 12 is a block diagram showing an example of an LD driver that controls the light emission amount of the light source unit based on a control signal from the laser control circuit. In FIG. 12, conventionally, the gain of the FSDAC (Full-Scale DAC) 50 is fixed, and the gain of the WDAC (Write DAC) 51, 52 is made variable to adjust the laser power.

  As described above, conventionally, the concept of efficiency calculation has been used to determine the laser power to emit light with the Full-Scale DAC fixed. However, in this case, in order to calculate the efficiency, it is necessary to monitor at least two laser drive currents.

  It is an object of the present invention to provide a laser power adjustment device, an optical disk device, a laser power adjustment method, a laser power adjustment program, and a recording medium on which this program is recorded, which realizes a simplified laser power control. And

  To achieve the above object, the invention according to claim 1 provides a first signal for varying the magnitude of an output signal for causing a semiconductor laser to emit light with a first power with respect to an input signal with an arbitrary gain. And a second signal variable unit that varies the magnitude of an output signal for causing the semiconductor laser to emit light with a second power smaller than the first power with respect to an input signal with an arbitrary gain. A laser power adjustment apparatus comprising: a third signal variabler that varies the magnitude of a signal input to the first signal variabler and the second signal variabler with an arbitrary gain; Setting means for setting the gain of the first signal variable device and the second signal variable device, and after setting the gain by the setting device, the power of the laser emitted from the semiconductor laser becomes a predetermined power. The third signal transformer And having an adjusting means for adjusting the obtained. With this configuration, if the laser power is determined by adjusting the gains of the first signal variable device and the second signal variable device, the laser power is determined by the third signal variable device in the previous stage. This eliminates the need for the conventional efficiency calculation, thereby simplifying the laser power control.

  According to a second aspect of the present invention, in the first aspect of the present invention, the setting means sets a gain for at least the first signal converter of the first signal transformer and the second signal transformer. An increase rate calculating means for calculating a gain increase rate with respect to a value; a power setting value corresponding to the power to be set from a power to be set in the semiconductor laser and a gain increasing rate calculated by the increase rate calculating means; And a gain setting means for setting the gain of the first signal variable device based on the setting value calculated by the setting value calculating means.

  The invention according to claim 3 is an optical disc apparatus that records at least one of reproduction, recording, and erasing of information by irradiating the optical disc with a laser emitted from a semiconductor laser, and a rotation motor that rotates the optical disc; A laser power adjustment device according to claim 1 or 2, wherein information is recorded on the optical disk rotated by the rotary motor using the laser power adjusted by the laser power adjustment device.

  The invention according to claim 4 is the invention according to claim 3, wherein the predetermined power is a minimum power necessary for recording information on an optical disc.

  The invention according to claim 5 is the invention according to claim 3 or 4, characterized in that the adjusting means adjusts the gain of the third signal variable device in a state of being out of focus.

  The invention according to claim 6 is the invention according to claim 3 or 4, wherein the adjusting means adjusts the gain of the third signal variable device in a state in which the focus is set on the test writing area of the optical disc. It is characterized by.

  According to a seventh aspect of the present invention, in the invention according to any one of the third to sixth aspects, the adjusting means is configured to apply the laser when the semiconductor laser irradiates a laser for recording user data on the optical disc. The gain adjustment of the third signal variable device is performed.

  The invention according to claim 8 is the invention according to claim 3, 5, 6 or 7, wherein the first power is used as the predetermined power for an optical disk on which information is recorded by irradiating a laser in pulses. Predetermined power irradiation means that continues to irradiate for a certain period at a power smaller than the second power and greater than the second power, and the adjusting means within the irradiation period of the predetermined power by the predetermined power irradiation means The gain adjustment of the signal variable device is performed.

  According to a ninth aspect of the invention, there is provided a first signal variable device for varying the magnitude of an output signal for causing the semiconductor laser to emit light at a first power with respect to an input signal, with an arbitrary gain. A second signal variable unit for varying the magnitude of an output signal for causing the semiconductor laser to emit light with a second power smaller than the first power with respect to a signal, and the first signal; A laser power adjustment method for a laser power adjustment apparatus, comprising: a third signal variabler that varies the magnitude of a signal input to the variable signal and the second signal variabler with an arbitrary gain; A setting step for setting the gain of the signal variable device and the second signal variable device, and after setting the gain by the setting step, the power of the laser emitted from the semiconductor laser becomes a predetermined power. 3 signal transformers And having an adjusting step of adjusting the resulting.

  According to a tenth aspect of the present invention, in the invention according to the ninth aspect, the setting step sets a gain for at least the first signal converter of the first signal transformer and the second signal transformer. An increase rate calculating step for calculating a gain increase rate with respect to the value, a power to be set in the semiconductor laser, and a gain setting value corresponding to the power to be set from the gain increase rate calculated in the increase rate calculating step And a gain setting step for setting the gain of the first signal variable device based on the setting value calculated by the setting value calculation step.

  According to an eleventh aspect of the present invention, there is provided a first signal variable device for varying the magnitude of an output signal for causing the semiconductor laser to emit light with a first power with respect to an input signal with an arbitrary gain. A second signal variable unit for varying the magnitude of an output signal for causing the semiconductor laser to emit light at a second power smaller than the first power with respect to a signal, and the first signal variable And a third signal variator for varying the magnitude of the signal input to the second signal variator with an arbitrary gain, a computer used in the laser power adjustment apparatus, the first signal variator And setting means for setting the gain of the second signal variable device, and after setting the gain by the setting means, the third signal variable so that the power of the laser emitted from the semiconductor laser becomes a predetermined power. The gain of the vessel Is a program for functioning as an adjustment means for settling.

  The invention according to claim 12 is the invention according to claim 11, wherein the setting means sets a gain for at least the first signal converter of the first signal transformer and the second signal transformer. An increase rate calculating means for calculating a gain increase rate with respect to a value; a power setting value corresponding to the power to be set from a power to be set in the semiconductor laser and a gain increasing rate calculated by the increase rate calculating means; And a gain setting means for setting the gain of the first signal variable device based on the setting value calculated by the setting value calculation means.

  The invention according to claim 13 is a computer-readable recording medium in which the program according to claim 11 or 12 is recorded.

  According to the present invention, since conventional efficiency calculation is not required, laser power control can be simplified.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an optical disk apparatus provided with an embodiment of a laser power adjustment apparatus of the present invention. Reference numeral 1 indicates an optical disk, and 10 indicates an optical disk apparatus. In the present embodiment, description will be made assuming that the optical disc 1 is a DVD + R.

  The optical disk device 10 includes a spindle motor 11 for rotating the optical disk 1, an optical pickup device 12, a laser control circuit 13, an encoder 14, a motor driver 15, a reproduction signal processing circuit 16, a servo controller 17, a buffer RAM 18, and a buffer manager 19. , An interface 20, a ROM 21 comprising a flash memory, a CPU 22, a RAM 23, a flash memory 24 as a storage means, and the like.

  The optical pickup device 12 emits a laser beam having a wavelength of 660 nm, guides the light beam emitted from the semiconductor laser to the recording surface of the optical disc 1, and sends the return light beam reflected by the recording surface to a predetermined light receiving position. The optical system is configured to include a guiding optical system, a light receiving device arranged at the light receiving position and receiving a return light beam, and a driving system such as a focusing actuator, a tracking actuator, and a seek motor (all not shown). Then, a current (current signal) corresponding to the amount of received light is output from the light receiver to the reproduction signal processing circuit 16.

  The optical pickup device 12 is a device for irradiating a recording surface on which a spiral or concentric track of the optical disc 1 is formed with laser light and receiving reflected light from the recording surface.

  FIG. 2 is an explanatory view showing the configuration of the optical pickup device in FIG.

  The optical pickup device 12 includes a light source unit 30, a collimator lens 31, a beam splitter 32, an objective lens 35, two detection lenses 33 and 37, two light receivers 34 and 38, a reflection mirror 36, and a drive system (focusing actuator, tracking). Actuators and seek motors (both not shown) are provided.

  The light source unit 30 includes a semiconductor laser 30a as a light source that emits laser light having a wavelength of about 660 nm. In the present embodiment, the maximum intensity emission direction of the light beam of the laser light emitted from the light source unit 30 (hereinafter abbreviated as “light beam”) is defined as the + X direction.

  The collimating lens 31 is disposed on the + X side of the light source unit 30, and the light beam emitted from the light source unit 30 by the collimating lens 31 becomes substantially parallel light. The reflection mirror 36 is disposed in the vicinity of the collimator lens 31, and a part of the light beam emitted from the light source unit 30 is reflected by the reflection mirror 36 in the −Z direction as a monitor light beam.

  The beam splitter 32 is disposed on the + X side of the collimating lens 31, and the light beam that has been made substantially parallel light by the collimating lens 31 passes through the beam splitter 32 as it is. Further, a light beam reflected by the optical disc 1 and incident via the objective lens 35 (return light beam) is branched in the −Z direction by the beam splitter 32.

  The objective lens 35 is disposed on the + X side of the beam splitter 32, and the light beam transmitted through the beam splitter 32 is condensed on the recording surface of the optical disc 1 by the objective lens 35.

  The detection lens 33 is disposed on the −Z side of the beam splitter 32, and the return light beam branched in the −Z direction by the beam splitter 32 is condensed on the light receiving surface of the light receiver 34 by the detection lens 33. As the light receiver 34, for example, a four-divided light receiving element divided into four partial light receiving elements is used as in the case of a normal optical disk device. In the present embodiment, the Y-axis direction substantially coincides with the track tangential direction on the optical disc 1. Further, each partial light receiving element of the light receiver 34 generates a current signal corresponding to the amount of received light by photoelectric conversion and outputs it to the reproduction signal processing circuit 16.

  The detection lens 37 is disposed on the −Z side of the reflection mirror 36 and condenses the monitoring light beam reflected in the −Z direction by the reflection mirror 36 on the light receiving surface of the light receiver 38. The light receiver 38 generates a current signal corresponding to the amount of received light by photoelectric conversion, and outputs the current signal to the laser control circuit 13 as a power monitor signal.

  As will be described later, the optical pickup device 12 includes an LD (laser diode: semiconductor laser) driver for generating a laser beam emitted from the semiconductor laser of the light source unit 30.

  The reproduction signal processing circuit 16 converts a current signal that is an output signal from the optical pickup device 12 into a voltage signal corresponding to the type of the optical disc 1, and based on this voltage signal, a wobble signal, a reproduction signal, and a servo signal (focus signal). Error signal, track error signal) and the like. Then, the reproduction signal processing circuit 16 extracts address information, a synchronization signal, and the like from the wobble signal. The address information extracted here is output to the CPU 22, and the synchronization signal is output to the encoder 14. Further, the reproduction signal processing circuit 16 performs error correction processing or the like on the reproduction signal and then stores it in the buffer RAM 18 via the buffer manager 19. The servo signal is output from the reproduction signal processing circuit 16 to the servo controller 17. In the reproduction signal processing circuit 16, servo parameters (for example, signal level adjustment gain) corresponding to the type of the optical disk are set according to an instruction from the CPU 22.

  A control signal for controlling the optical pickup device 12 is generated by the servo controller 17 based on the servo signal and is output to the motor driver 15. Input / output of data to / from the buffer RAM 18 is managed by the buffer manager 19, and when the accumulated data amount reaches a predetermined value, the CPU 22 is notified of that fact.

  Based on the control signal from the servo controller 17 and the instruction from the CPU 22, the optical pickup device 12 and the spindle motor 11 are controlled by the motor driver 15.

  Data stored in the buffer RAM 18 is taken out by the encoder 14 via the buffer manager 19 based on an instruction from the CPU 22, and an error correction code is added to create write data to the optical disk 1. Then, based on an instruction from the CPU 22, write data is output to the laser control circuit 13 by the encoder 14 in synchronization with the synchronization signal from the reproduction signal processing circuit 16.

  The laser light output from the optical pickup device 12 is controlled by the laser control circuit 13 based on the write data from the encoder 14. That is, the laser driver 13a drives and controls the LD driver 12a.

  The interface 20 is a bidirectional communication interface with a host (for example, a personal computer) 25 and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).

  The ROM 21 stores various programs including a program for discriminating the type of the optical disk, which is described by a code readable by the CPU 22. The flash memory 24 is a non-volatile memory, can be written to and read from the CPU 22, and retains recorded contents even when the power is turned off.

  The operation of each unit is controlled by the CPU 22 according to the program stored in the ROM 21, and data necessary for the control is temporarily stored in the RAM 23. Further, the CPU 22 outputs a signal for selecting one of the above-described units when the circuit system is divided into a CD circuit system and a DVD circuit system. When the optical disk apparatus 10 is turned on, the program stored in the ROM 21 is loaded into the main memory (not shown) of the CPU 22.

  FIG. 3 is a functional block diagram of the laser power adjustment apparatus according to the embodiment of the present invention. The laser power adjustment device includes a CPU 22, an optical pickup device 12, and a laser control circuit 13. The optical pickup device 12 includes an LD driver (LD: laser diode) 12a, a light source unit 30, and a light receiver 38 for monitoring.

  As described with reference to FIG. 2, a part of the laser light emitted from the light source unit 30 is received by the light receiver 38. The light receiver 38 generates a current corresponding to the amount of light received. The generated current signal is once input to the laser control circuit 13 and then input to the CPU 22 through a current-voltage converter and an AD (analog / digital) converter (not shown).

  A control signal for adjusting the laser power is output from the CPU 22 to the laser control circuit 13 in accordance with the input value. The laser control circuit 13 adjusts the laser power by driving the LD driver 12a based on the write data from the encoder 14 and changing the magnitude of the current input to the light source unit 30 based on the control signal from the CPU 22. . The light emission power value corresponding to the input value to the CPU 22 is obtained in advance, and the ROM 21 stores a correspondence table between the input value and the light emission power value. By referring to this correspondence table, the CPU 22 can derive the current emission power from the input value or an input value corresponding to the emission power value to be set.

  Although this laser power adjustment device is described and explained for each functional block, the laser control circuit 13 may be configured as an LSI together with the encoder 14, the reproduction signal processing circuit 16, and the like when mounted.

  FIG. 4 is a block diagram showing a circuit configuration of the LD driver of FIG. The LD driver 12a includes a current source 12g, an FSDAC (Full-Scale DAC) 12b, a WDAC (Write DAC) 12c and 12d, an adder 12e, and a timing control circuit 12f, and the laser power determined by the laser control circuit 13 Is converted into a current for actually emitting light.

  The current source 12g supplies a constant current to the circuit. The FSDAC 12b is a DA converter that can adjust an output current value for an input in 256 stages. Now, when increasing by one step, the FSDAC value is increased by one. When the FSDAC value is m, the gain (amplification or attenuation factor) of the current can be set at 1.0 × (m / 255), for example. The FSDAC value is changed / set by a command from the laser control circuit 13 based on a control signal from the CPU 22.

  The WDACs 12c and 12d are DA converters that can adjust output current values Iout1 and Iout2 with respect to inputs in 256 stages. Here, when the level is increased by one step, the WDAC value is increased by one. When the WDAC value is n, the current gain (amplification or attenuation factor) can be set to 1.0 × (n / 255), for example. This WDAC value is set by a command from the laser control circuit 13 based on a control signal from the CPU 22. The adder 12e adds Iout1 and Iout2 and generates a current for driving the light source unit 30.

  For example, Iout1 is a current value for the light source unit 30 to emit light with the bias power Pb or the read power Pr, and Iout2 is a current value for emitting light with the write power Pw by adding to Iout1. Note that Iout2 may be a current value for causing the semiconductor laser 51 to emit light with the bias power Pb or the read power Pr, and Iout1 may be a current value for emitting light with the write power Pw by adding Iout2.

  Also, Iout1 (or Iout2) is a current value for causing the light source unit 30 to emit light with the bias power Pb or read power Pr, and Iout2 (or Iout1) is a current value for causing the light source unit 30 to emit light with the write power Pw. There may be. In this case, instead of the adder 12e, a switch 12e 'that selectively outputs Iout1 or Iout2 and is switched by a command from the CPU 22 or the like may be used.

  The timing control circuit 12f outputs a current signal from the WDAC 12c or / and the WDAC 12d (or stops outputting the current signal) according to the synchronous clock (channel clock) and the 8-16 modulation signal input from the laser control circuit 13. A timing signal is generated and output to the WDAC 12c and / or 12d. Note that a switch 12e 'that outputs one or both of Iout1 and Iout2 to the light source unit 30 may be provided, and the timing signal may be controlled to switch the switch 12e' instead of the WDAC 12c or / and the WDAC 12d.

  By the way, as a general recording waveform for recording information on a dye-type medium, for example, there is a single-pulse semiconductor laser emission waveform generated based on an 8-16 modulation code or the like. However, there is a problem that the recording mark is distorted like a tear due to animal fever. For this reason, as shown in FIG. 5, as the LD emission waveform rule (strategy) for recording information on the dye-based medium, the multi-pulse waveform laser light based on the recording data such as the EFM modulation code is used for the dye-based medium. A method for forming a mark has been proposed.

  Here, a recording method using a laser power control method when an FSDAC (Full-Scale DAC) is used will be described.

  FIG. 7 shows the laser power adjustment process of the present embodiment, and is an example of the process executed by the CPU 22 in accordance with the program stored in the ROM 21. The laser power adjustment process of the present invention is roughly divided into four processes: an initial process S1, a pre-recording adjustment process S2, an OPC adjustment process S3, and a recording adjustment process S4. Details of these processes will be described later. In the present embodiment, the initial process S1 is an essential process, but the pre-recording adjustment process S2, the OPC adjustment process S3, and the recording adjustment process S4 are optional processes, and at least one of them is performed. It is possible to adjust the laser power.

(Initial processing)
First, the initial process S1 will be described with reference to FIG. This process is a process executed by the CPU 22 in accordance with a program stored in the ROM 21. First, the type of recording medium is discriminated from the magnitude of the reflectance, etc., and the CPU 22 determines the minimum laser power necessary for recording on the recording medium according to the type and / or recording speed of the recording medium. (S1-1). Actually, the value input to the CPU 22 in accordance with the current value detected by the light receiver 38 is the minimum necessary laser power. The CPU 22 obtains the power per 1 LSB (per 1 LSB (= least significant bit)) of the WDAC value based on the determined laser power (S1-2) and stores it (S1-3). In this initial processing, setting of the current value by the FSDAC 12b is not considered.

  As an example, consider a case where the CPU 22 determines that a laser power of 30 mW is required (S1-1). In this case, since the setting range of the WDACs 12c and 12d is 0 to 255, if 1 is entered in the WDAC value, the light source unit 30 emits light at 0.12 mW (≈30 mW / 255) (S1-2). That is, ideally, the WDACs 12c and 12d whose WDAC value is set to 1 in response to a command from the CPU 22 inputs a predetermined current value (current value 255 times the output current value of the WDAC) output from the FSDAC 12b. Thus, a current value that causes the light source unit 30 to emit light at 0.12 mW is output. The CPU 22 stores the value of 0.12 mW itself as a reference value in the RAM 23 in order to perform subsequent processing using this 0.12 mW (S1-3 in FIG. 8). The reference value may be a value that is received by the light receiver 39 when the light source unit 30 emits light at 0.12 mW and is input to the CPU 22. This ends the process.

  When the bias power Pb or read power Pr to be set is set to 1 mW using such a reference value, the CPU 22 sets the WDAC value 8 (≈1 mW / 0.12 mW) to the WDAC 12c via the laser control circuit 13. It will be. Further, when the write power Pw to be set is 20 mW, the CPU 22 sets 159, which is obtained by subtracting 8 from 167 (≈20 mW / 0.12 mW), as the WDAC 12d via the laser control circuit 13.

  In addition, when the current input to the light source unit 30 is switched between Iout1 and Iout2 by using the switch 12e ′ without using the adder 12e, for example, only Iout1 is emitted to emit Pb or Pr, and Pw is emitted. When only Iout2 is used, 167 is set as the WDAC value in the WDAC 12d via the laser control circuit 13 in accordance with a command from the CPU 22.

(Adjustment process before recording)
Next, the pre-recording adjustment process S2 for determining the FSDAC value will be described with reference to FIG. This process is a process executed by the CPU 22 in accordance with a program stored in the ROM 21 before starting recording.

  After the optical disk is inserted and the initial process S1 shown in FIG. 8 is performed, the CPU 22 sends a control signal to the WDAC 12c or WDAC 12d in a ready state, for example, to send a control signal to the laser control circuit 13, and is necessary for recording on the optical disk. As a minimum emission power, a value of 30 mW (in the above example, 255 as the WDAC value) is set (S2-1), an FSDAC value is set (S2-2), and the laser drive current (sample in FIG. 1) is set. The FSDAC value corresponding to 30 mW is determined by monitoring the power output (S2-3-5).

  That is, the CPU 22 obtains the WDAC value (255) to be set in the WDAC 12c or WDAC 12d from the light emission power of the light source unit 30 per WDAC value 1 obtained in the initial process S1 and the light emission power to the optical disc (30 mW / 0.12 mW). The CPU 22 outputs a control signal to the laser control circuit 13 so that the calculated WDAC value is obtained. The laser control circuit 13 sets the WDAC value of the WDAC 12c or WDAC 12d of the LD driver 12a according to this control signal. When the adder 12e is used, the sum of the WDAC values set in the WDAC 12c and the WDAC 12d is set to 255. When the switch 12e 'is used, the WDAC value of the WDAC 12d is set to 255 (S2-1).

  Next, the CPU 22 sends a control signal to the laser control circuit 13 to set the FSDAC value of the FSDAC 12b to a predetermined initial value. This initial value is set to a sufficiently small value in order to prevent a current exceeding the rated value of the light source unit 30 from being input to the light source unit 30 (S2-2).

  In this state, the CPU 22 causes the light source unit 30 to emit light to the optical disc 1 rotating at a predetermined rotation speed. In this case, it is possible to prevent the recording layer of the optical disc 1 from being damaged by causing the light source unit 30 to emit light with the focus off (S2-3).

  When using the detection signal of the light receiver 38 in a state where it is assumed to emit light at a constant period of 30 mW, that is, when the adder 12e is used, the switch 12e ′ is used in a state where Iout1 is output from the WDAC 12c and Iout2 is output from the WDAC 12d. In this case, the CPU 22 acquires a detection signal of the light receiver 38 in a state where the switch 23e ′ is closed via the laser control circuit. Further, it is determined whether or not the acquired signal value is a value corresponding to the set light emission power (30 mW) (S2-4). If the acquired value and the set value are different, the CPU 22 issues a command to the laser control circuit 13 to adjust the FSDAC value according to the magnitude of the signal, and adjusts the FSDAC value (S2-5). Then, the CPU 22 adjusts the FSDAC value until it becomes a value corresponding to the detection signal from the light receiver 38 when the light source unit 30 outputs the light emission power of 30 mW (S2-3 to 5). This ends the process.

  When other values are set as the light emission power, for example, 1 mW as Pb or Pr, and 20 mW as Pw, the CPU 22 sends a control signal to the laser control circuit 13, the DAC value is 8 for the WDAC 12c, and the DAC value is for the WDAC 12d. 159 (when the adder 12e is used) or 167 (when the switch 12e ′ is used) is set. After making this setting, the CPU 22 adjusts the FSDAC value of the FSDAC 12b by the same method as described above.

(Adjustment process during OPC)
When recording is started, OPC (Optimum Power Control) is performed to determine the optimum laser power for the recording disk. In general, since dye media and phase change media vary depending on the ambient temperature, the type of recording media, the linear velocity, etc., recording power is optimized by trial writing. In OPC, predetermined information is recorded in a predetermined area called a PCA (Power Calibration Area) of a recording medium, and an optimum recording power is obtained by reproducing the recorded portion. In this operation, a laser is actually emitted and a recording operation is involved. Therefore, when OPC is executed, it is determined whether or not the set laser power is as set, and if the laser drive current is monitored and different, an OPC adjustment process S3 for changing / correcting the FSDAC value is performed. Next, the OPC adjustment process S3 will be described with reference to FIG. This process is a process executed by the CPU 22 in accordance with a program stored in the ROM 21.

  The steps S3-1 and S2 are the same as the steps S2-1 and S2 in FIG. 7, and are as described in the pre-recording adjustment process S2. After setting the initial value to the FSDAC value (S3-2), the CPU 22 issues a command to each block of the optical disk apparatus and moves the optical pickup apparatus 12 to move the optical pickup to a predetermined position in the PCA area of the optical disk 1. A spot of light emitted from the device 12 is made to come. At this time, the focus is ON (S3-3).

  When the light spot reaches a predetermined position, the CPU 22 drives the light source unit 30 and outputs a control signal to the laser control circuit 13 so as to emit a laser. As a result, the laser control circuit 13 controls the LD driver 12a to cause the light source unit 30 to emit light according to the DAC values set in S3-1 and S3-1 (S3-4).

  S3-5 and 6 are the same as S2-4 and S5 in the pre-recording adjustment process S2 of FIG. 7 except that the light source unit 30 emits light in the on-focus state, and are as described above. Therefore, the CPU 22 repeats the processes of S3-4 to S6 until the value corresponding to the light emission power matches the value corresponding to the set light emission power.

  When the value corresponding to the actual light emission power matches the value corresponding to the set light emission power in S3-5, the CPU 22 performs normal OPC processing to obtain the optimum recording power and sets it as the subsequent recording power. (S3-7). This ends the process.

(Adjustment process during recording)
After recording starts, there is a possibility that light is not emitted at the set laser power due to factors such as self-heating. Therefore, the recording adjustment process S4 is performed to monitor the laser drive current to determine whether light is emitted with the optimum laser power. When it is determined that light is not emitted, the FSDAC value is changed / corrected. Such a recording adjustment process S4 will be described with reference to FIG. This process is a process executed by the CPU 22 in accordance with a program stored in the ROM 21.

  First, the CPU 22 calculates a value set in the WDAC value according to the recording speed, the type of the optical disk to be recorded, and the like from the value obtained in the initial process S1, and sets the value as the WDAC value (S4-1). Alternatively, when the method described later with reference to FIG. 6 is used, a preset value can be used as the WDAC value.

  Next, the CPU 22 sets a predetermined value as the FSDAC value (S4-2). As this predetermined value, a value determined by the OPC operation executed before recording is normally used. Alternatively, a predetermined value corresponding to a method described later with reference to FIG.

  Note that S4-1 and S2 are processes performed before actual user data recording, but are essential processes when the pre-recording adjustment process S2 and the OPC adjustment process S3 are not performed. Here is an explanation.

  Next, the CPU 22 detects a part of the laser power of the light source unit 30 during normal recording with the monitor light receiver 38. As described above, this detection is performed via the laser control circuit 13 (S4-3). When using the method described later with reference to FIG. 6, a predetermined power is emitted.

  Then, the CPU 22 determines whether the value corresponding to the actually emitted power matches the value corresponding to the power set by OPC (predetermined power in the case of the method described later with reference to FIG. 6) (S4). -4). If it is determined that they do not match, the CPU 22 sends a control signal to the laser control circuit 13 to change the FSDAC value (S4-5). Until the value corresponding to the actually emitted power matches the value corresponding to the power set by OPC (predetermined power in the case of the method described later using FIG. 6), S4-3-5. Repeat the process. When the value corresponding to the emitted power matches the value corresponding to the power set by OPC (predetermined power in the case of the method described later with reference to FIG. 6), this processing ends. In addition, you may make it perform the process of S4-3, 5 for every predetermined period progress.

  As described above, S1 to S4 are laser power adjustment processing in laser emission using the FSDAC value.

  Next, a specific example of a method for monitoring the laser drive current will be described below. Note that the operating principle of the FSDAC value determination method is the same before and during recording.

  When APC is performed at the time of recording, the recording power changes at a high speed in order to form a mark / space. Therefore, by providing a period in which the laser emission waveform is appropriately driven in a non-pulse state, for example, the amorphization level (peak power) and the read level (bottom power) are controlled during recording of the phase change medium. Furthermore, there is a method of recording using a pulsed recording waveform even for a dye medium that can be recorded only once. In addition, a recording mark is not formed well by continuous heating in a portion recorded in a non-pulse state, and becomes a defective portion, but is hardly affected by the error correction function of the reproduction drive device.

  FIG. 6 shows a monitor waveform in the case where laser is emitted while providing a period for driving in a non-pulse state. A point indicates a set power output for laser power adjustment. As a method for correcting the FSDAC value, if the set power at the point A in FIG. 6A is determined in advance, this value is monitored. If the set power is different from the set power, the FSDAC value is changed. change. In this case, the CPU 22 inputs a control signal to the laser control circuit 13, and in accordance with this input signal, the laser control circuit 13 uses the WDAC values of the WDAC 12c and WDAC 12d and the switch 12e ′ when the adder 12e is used. In this case, the WDAC value of the WDAC 12d is set to a predetermined value, and the set power is output to the timing control circuit 12f for a predetermined period. In this state, the CPU 22 detects the signal from the light receiver 38 via the laser control circuit 13 and adjusts the FSDAC value so that the predetermined power corresponding to the set power at the point A is obtained. After adjusting the FSDAC value, the CPU 22 returns all WDAC values to the values before performing this process.

  In the above description, among the pre-recording adjustment process S2, the OPC adjustment process S3, and the recording adjustment process S4, only the recording adjustment process S4 uses the method for monitoring the laser drive current described with reference to FIG. However, in the other pre-recording adjustment processing S2 and OPC adjustment processing S3, the method for monitoring the laser drive current described with reference to FIG. 6 can be used. By repeating this cycle using a method such as controlling at regular time intervals, the optimum laser power during recording can always be maintained at the set power (see FIG. 6B).

  As described above, according to the present embodiment, processing such as two-point measurement can be omitted as in the conventional efficiency calculation, and processing can be simplified.

  In addition, according to the above-described embodiment, the optical disk apparatus including the light source unit 30 having a wavelength of 660 nm has been described. However, the present invention is not limited to this, and the light source unit 30 may have a wavelength of 780 nm. The semiconductor laser may include both or more of them. When a plurality of semiconductor lasers are provided, the DAC value for the DAC differs depending on the semiconductor laser used.

  INDUSTRIAL APPLICABILITY The present invention can be used in the field of optical disc apparatuses that record / reproduce information using information recording media such as CD-R / RW, DVD + R / RW, and DVD-R / RW.

Explanatory drawing which shows schematic structure of the optical disk apparatus provided with one Embodiment of the laser power adjustment apparatus of this invention Explanatory drawing which shows the structure of the optical pick-up apparatus in FIG. Functional block diagram of the laser power adjustment apparatus of this embodiment The block diagram which shows the circuit structure of the LD driver of FIG. The figure which shows the multipulse waveform based on recording data, such as an EFM modulation code The figure which shows the monitor waveform at the time of providing the period driven in a non-pulse state and emitting laser Flowchart showing laser power adjustment processing of the present embodiment Flow chart showing details of initial processing S1 Flowchart showing details of pre-recording adjustment processing S2 The flowchart which shows the detail of adjustment process S3 at the time of OPC Flowchart showing details of adjustment process S4 during recording Configuration diagram showing an example of an LD driver that controls the light emission amount of a light source unit based on a control signal from a laser controller circuit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 10 Optical disk apparatus 11 Spindle motor 12 Optical pick-up apparatus 12a LD driver 12b Full-Scale DAC (FSDAC)
12c, 12d WDAC (Write DAC)
12e Adder 12e 'Switch 12f Timing control circuit 12g Current source 13 Laser control circuit 14 Encoder 15 Motor driver 16 Reproduction signal processing circuit 17 Servo controller 18 Buffer RAM
19 Buffer manager 20 Interface 21 ROM
22 CPU
23 RAM
24 flash memory 30 light source unit 30a semiconductor laser 31 collimating lens 32 beam splitters 33 and 37 detection lenses 34 and 38 light receiver 35 objective lens 36 reflecting mirror

Claims (13)

  A first signal variator for varying the magnitude of an output signal for causing the semiconductor laser to emit light at a first power with respect to an input signal, and an arbitrary gain; and the semiconductor laser for the input signal. A second signal variable device for varying the magnitude of an output signal for emitting light with a second power smaller than the first power by an arbitrary gain, the first signal variable device and the second signal variable device; And a third signal variable device that varies the magnitude of the signal input to the signal at an arbitrary gain, wherein the gains of the first signal variable device and the second signal variable device are adjusted. Setting means for setting; and adjusting means for adjusting the gain of the third signal variable device so that the power of the laser emitted from the semiconductor laser becomes a predetermined power after the gain is set by the setting means. It is characterized by having Laser power adjustment device.   The setting means includes an increase rate calculating means for calculating a gain increase rate with respect to a gain setting value for at least the first signal converter of the first signal variabler and the second signal variabler; A setting value calculating means for calculating the set value of the gain corresponding to the power to be set from the power to be set in the semiconductor laser and the gain increasing rate calculated by the increasing rate calculating means, and the setting value calculating means 2. The laser power adjusting device according to claim 1, further comprising gain setting means for setting a gain of the first signal variable device based on the set value.   3. A laser according to claim 1, wherein the optical disk device performs at least recording of information reproduction, recording, and erasing by irradiating the optical disk with a laser emitted from a semiconductor laser, and a rotation motor that rotates the optical disk. An optical disc apparatus comprising: a power adjustment device, wherein information is recorded on the optical disc rotated by the rotary motor using the laser power adjusted by the laser power adjustment device.   4. The optical disc apparatus according to claim 3, wherein the predetermined power is a minimum power necessary for recording information on the optical disc.   5. The optical disc apparatus according to claim 3, wherein the adjusting means adjusts the gain of the third signal variable device in a state where the focus is removed.   5. The optical disc apparatus according to claim 3, wherein the adjusting unit adjusts the gain of the third signal variable unit in a state where a focus is set on a test writing area of the optical disc.   7. The adjustment unit according to claim 3, wherein the adjustment unit adjusts the gain of the third signal variable unit when the semiconductor laser irradiates a laser beam for recording user data on the optical disc. 2. An optical disk device according to claim 1.   Predetermined power irradiating means for continuously irradiating an optical disc that records information by irradiating laser in pulses with a power smaller than the first power and larger than the second power as the predetermined power The adjusting means adjusts the gain of the third signal variable device within the irradiation period of the predetermined power by the predetermined power irradiation means. The optical disk device described.   A first signal variator for varying the magnitude of an output signal for causing the semiconductor laser to emit light at a first power with respect to an input signal, and an arbitrary gain; and the semiconductor laser for the input signal. A second signal variable device for varying the magnitude of an output signal for emitting light with a second power smaller than the first power by an arbitrary gain, the first signal variable device and the second signal variable device; A laser power adjustment method for a laser power adjustment apparatus comprising: a third signal variable device that varies the magnitude of a signal input to the signal at an arbitrary gain, wherein the first signal variable device and the second signal A setting step for setting the gain of the variable device, and after the gain is set by the setting step, the gain of the third signal variable device is adjusted so that the power of the laser emitted from the semiconductor laser becomes a predetermined power Adjustment process to Laser power adjusting method characterized in that it comprises.   The setting step includes an increase rate calculating step of calculating a gain increase rate with respect to a set value of gain for at least the first signal converter of the first signal variabler and the second signal variabler; A setting value calculating step for calculating a setting value of the gain corresponding to the power to be set from a power to be set for the semiconductor laser and a gain increasing rate calculated by the increasing rate calculating step, and calculating by the setting value calculating step The laser power adjustment method according to claim 9, further comprising a gain setting step of setting a gain of the first signal variable device based on the set value.   A first signal variator for varying the magnitude of an output signal for causing the semiconductor laser to emit light at a first power with respect to an input signal, and an arbitrary gain; and the semiconductor laser for the input signal. A second signal variable device for varying the magnitude of an output signal for emitting light with a second power smaller than the first power by an arbitrary gain, the first signal variable device and the second signal variable device; A computer for use in a laser power adjustment apparatus having a third signal variabler that varies the magnitude of a signal input to the signal with an arbitrary gain is used for the first signal variabler and the second signal variabler. Setting means for setting the gain, and adjusting means for adjusting the gain of the third signal variable device so that the power of the laser emitted from the semiconductor laser becomes a predetermined power after setting the gain by the setting means As machine Program to be.   The setting means includes an increase rate calculating means for calculating a gain increase rate with respect to a gain setting value for at least the first signal converter of the first signal variabler and the second signal variabler; A setting value calculating means for calculating the set value of the gain corresponding to the power to be set from the power to be set in the semiconductor laser and the gain increasing rate calculated by the increasing rate calculating means, and the setting value calculating means 12. The program according to claim 11, further comprising gain setting means for setting a gain of the first signal variable device based on the set value.   The computer-readable recording medium which recorded the program of Claim 11 or 12.

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