JP2000222758A - Semiconductor laser power controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for performing high-speed control with a D/A converter having a small number of bits in a semiconductor laser power controller used for an optical disk recorder/player. SOLUTION: In the control of playing power, by using a bias current control system 150 for executing rough control and a playing current control system 140 for executing fine control, the control of a bias current is performed based on the error of the playing current control system. In a recording current control system 160 for controlling recording power, a means for setting a recording current reference value used to decide a recording current operation point and a recording current table 24 for recording power are provided, and by setting a recording current reference value with reference to the table during the changing of recording power, recording power is controlled at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control device for a semiconductor laser, and more particularly, to a device applied to an optical disk device for performing recording or reproduction using a semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, an APC (Automated Laser) for maintaining the power of a semiconductor laser at a predetermined recording power or reproduction power.
Various systems have been proposed as an atic power control (AIC) circuit.
As a digital control method using the A converter,
For example, there is one disclosed in Japanese Patent Application Laid-Open No. 5-144064.

FIG. 16 shows an APC of this conventional semiconductor laser.
FIG. 2 shows a block diagram of the circuit. This APC circuit converts a part of the optical output of the semiconductor laser (LD) 2 into a photodiode (P
D) It is configured to control the power of the semiconductor laser by monitoring the light output level of the semiconductor laser by making it incident on 1). Here, the configuration will be briefly described.

In FIG. 16, reference numeral 1 denotes a semiconductor laser (L
D) a photodiode (PD) for monitoring a part of the optical output of 2; 3 an IV conversion circuit for converting the photocurrent obtained by the photodiode (PD) 1 into a voltage; A reproduction power detection circuit for detecting a power (hereinafter, referred to as reproduction power) irradiated by the semiconductor laser 2 when reproducing an optical disk based on the voltage obtained by the circuit 3, and a reproduction power detection circuit 6 outputs the output of the reproduction power detection circuit 4 to A A / D converter for performing / D conversion, 8 is a Pr target value register for setting a target value of reproduction power Pr, 101 is a subtracter for subtracting the output of A / D converter 6 from the output of Pr target value register 8, 26 Counts the output of the subtractor 101 up /
The U / D counter for counting down, 25 is the U / D
A D / A converter for D / A converting the output of the counter 26;
9 is a reproduction current Ir based on the output of the D / A converter 25.
Is an Ir current control circuit.

[0005] Reference numeral 5 denotes a recording power detection circuit for detecting the power (hereinafter referred to as recording power) irradiated by the semiconductor laser 2 when recording on the optical disk based on the voltage obtained by the IV conversion circuit 3; Is an A / D converter for A / D converting the output of the recording power detection circuit 5, 9 is a Pw target value register for setting a target value of the recording power Pw, 10
2 is a subtractor for subtracting the output of the A / D converter 7 from the output of the Pw target value register 9, 27 is a U / D counter for counting up / down the output of the subtractor 102, and 18 is this U / D counter. A D / A converter for D / A conversion of the output of 27; 21 an Iw current control circuit for controlling the recording current Iw based on the output of the D / A converter 18;
A switch 2 turns on and off the output current of the Iw current control circuit 21 based on the data signal 23. Also, 1
03 is an adder for adding the output of the Iw current control circuit 21 output through the switch 22 and the output of the Ir current control circuit 19, and 2 is a semiconductor laser driven by the sum current obtained by the adder 103. (LD).

FIG. 17 shows a graph of the light output characteristic with respect to the current of the semiconductor laser. As shown in the figure, the control of the reproduction power Pr is performed by increasing or decreasing the reproduction current Ir, and the control of the recording power Pw is performed by increasing or decreasing the recording current Iw added to the reproduction current Ir. Modulation of the semiconductor laser at the time of recording is performed by turning ON / OFF the addition of the recording current Iw to the reproduction current Ir.

Next, the operation will be described. The semiconductor laser (L) monitored by the photodiode (PD) 1
The light output of D) 2 is converted into a current by the photodiode (PD) 1. This current is supplied to the IV conversion circuit 3
The voltage is converted into a voltage during reproduction, and a constant voltage value based on the optical output during reproduction and an optical output modulated by a recording data signal during recording are output as a voltage waveform. The current-voltage conversion gain of the IV conversion circuit 3 is, for example, 10 m
At the time of W, adjustment is made so that the light output value and the output voltage value become 1 V absolutely.

First, a reproduction power control system 200 for controlling the reproduction current Ir in order to maintain the reproduction power Pr at a predetermined value.
Will be described. The reproduction power control system 200 includes a reproduction power detection circuit 4, an A / D converter 6, a subtractor 101, Pr
It comprises a target value register 8, a U / D (Up / Down) counter 26, a D / A converter 25, and an Ir current control circuit 19. The optical output is maintained at the reproducing power Pr at the time of reproduction, and the optical modulation output is at the time of recording. Of the reproduction power Pr
Control to keep

That is, at the time of reproduction, the optical output detected through the reproduction power detection circuit 4 is converted into a digital value by the A / D converter 6, and at the time of recording, the bottom value of the modulated voltage waveform is converted to the reproduction power detection circuit. The bottom value of the optical output is extracted by sampling and holding at 4, and is converted into a digital value by the A / D converter 6. A digital value corresponding to a predetermined reproduction power Pr is set in the Pr target value register 8, and the output value of the A / D converter 6 is subtracted by the subtractor 101 to compare the magnitudes. 26 Up
Determine the count direction of / Down. If the output value of the A / D converter 6 is smaller than the set value of the Pr target value register 8, the light output is insufficient, so the U / D counter 26 counts in the Up direction, and conversely, the A / D converter The output value of 6 is P
If the value is larger than the value set in the r target value register 8, the light output is too large, and the U / D counter 26 counts down. The timing of this count is A /
D-conversion is performed, subtraction is performed, and the comparison is performed every time a magnitude comparison result is obtained. The digital value of this U / D counter 26 is
The current is converted into an analog voltage by the / A converter 25, and the Ir current control circuit 19 controls the reproduction current Ir of the semiconductor laser (LD) 2 based on the output voltage of the D / A converter 25.

Therefore, when the light output is less than the predetermined reproduction power Pr, the output value of the A / D converter 6 is smaller than the set value of the Pr target value register 8, so that the U / D counter 2
6 is controlled in a direction in which the reproduction current Ir is increased by counting in the direction of Up, and conversely, the optical output becomes a predetermined reproduction power P
r is too large, the output value of the A / D converter 6 becomes P
Since the value is larger than the value set in the r target value register 8, the U / D counter 26 counts in the Down direction and counts the reproduction current I
r is controlled in a direction to decrease.

Next, a recording power control system for controlling the recording current Iw to maintain the recording power Pw at a predetermined value will be described. The recording power control system 300 includes a recording power detection circuit 5, an A / D converter 7, a Pw target value register 9, a subtractor 102, a U / D counter 27, a D / A converter 18,
It is composed of an Iw current control circuit 21 and a switch 22, and the configuration is almost the same as that of the reproduction power control system.
During recording, control is performed to keep the peak value of the optical modulation output at the recording power Pw.

That is, at the time of recording, the peak value of the modulated voltage waveform is sampled and held by the recording power detection circuit 5 to extract the peak value of the optical output, and this is extracted as A / A
The data is converted into a digital value by the D converter 7. Further, a digital value corresponding to a predetermined recording power Pw is set in advance in the Pw target value register 9, and the output value of the A / D converter 7 is subtracted by the subtracter 102 to compare the magnitudes. / D (Up / Down) Up / D of counter 27
Determine the count direction of own. This U / D counter 2
7 is converted into an analog voltage by the D / A converter 18, and based on the output voltage of the D / A converter 18,
The w current control circuit 21 controls the recording current Iw of the LD 2. Then, based on the data signal 23, the switch 22
The output of the semiconductor laser (LD) 2 is modulated by turning on / off the recording current. As described above, the recording power Pw is also kept constant in the same manner as the reproduction power Pr.

[0013]

The optical disk recording / reproducing apparatus may be used, for example, by being incorporated in a computer as an optical disk drive.
There is a demand for downsizing of the device. A of this semiconductor laser
In a PC circuit, a high-speed recording power control is required in order to compensate for recording power in response to stains such as fingerprints on a disk surface during recording, which is called Running OPC.

The method of speeding up the power control proposed in Japanese Patent Application Laid-Open No. 5-144064 is a method for speeding up the reproduction power control by adding a high-speed control loop using an analog circuit. Although it can be applied to speeding up of power control, adding an analog circuit is expensive, and it is difficult to achieve high integration, which increases the circuit board area and reduces the size of the device. There is a problem that can not be achieved.

In addition, since fluctuations in the reproduction power lead to a deterioration in the error rate of the reproduction data signal, it is necessary to make the control resolution fine.
The D / A converter for controlling the reproduction power has a high resolution,
There is also a problem that an expensive multi-bit D / A converter must be used.

Furthermore, with the increase in the recording data transfer rate, the response speed of the monitoring photodiode is slow, so that accurate recording power cannot be detected and the error in the control of the recording power increases. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide a digitally controlled semiconductor laser power control device capable of controlling recording power at high speed. .

Further, according to the present invention, the D / A having a small number of bits is not deteriorated without deteriorating the error rate of the reproduced data signal.
It is an object of the present invention to provide a digitally controlled semiconductor laser power control device capable of controlling reproduction power by a converter.

Still another object of the present invention is to provide a digitally controlled semiconductor laser power control device capable of controlling recording power with an inexpensive photodiode having a slow response speed without using an expensive high-speed response photodiode. I do.

[0020]

According to a first aspect of the present invention, there is provided a semiconductor laser power control apparatus for controlling the power of a semiconductor laser used in an optical disk recording / reproducing apparatus. A reproduction power control unit for performing digital control using two current control systems, a bias current control system for roughly controlling the power of a semiconductor laser during reproduction and a reproduction current control system for finely controlling the power of the semiconductor laser; It has a recording current reference value setting means for determining a current operating point, and a table of recording current for the recording power of the semiconductor laser. When the recording power is changed, the recording power is set by referring to the table and setting the recording current reference value. Pulses longer than the time constant of the recording current control system that performs digital control and the photodiode that monitors the power of the semiconductor laser are Recording power correction means for causing a semiconductor laser to emit light with a short pulse used for recording and detecting the recording power with a short pulse and storing the attenuation of the power as a correction value, and digitally correcting the recording power during actual recording Is provided.

A semiconductor laser power control apparatus according to a second aspect of the present invention includes a semiconductor laser for irradiating a laser beam to an optical disk capable of recording a data signal;
A laser power detecting means for detecting the power of the laser light emitted from the semiconductor laser; digitally detecting a reproducing power level of the laser light from an output of the laser power detecting means; A reproducing power error calculating means for calculating a reproducing power error with respect to a level; and a recording power level of the laser light is digitally detected from an output of the laser power detecting means to record a recording power target value and the recording power level. Recording power error calculating means for calculating a power error; first filter means for amplifying a low frequency component of the output of the reproducing power error calculating means and attenuating a high frequency component; and among the outputs of the first filter means Second filter means for amplifying the low-frequency component and attenuating the high-frequency component; and a low-frequency component among the outputs of the recording power error calculating means. Amplified third to attenuate the high frequency component
Filter means, first current control means for controlling a first current for controlling reproduction power, and second current control means for controlling a second current for controlling reproduction power by adding to the first current. 2 current control means, third current control means for controlling a third current for controlling recording power, and
First to third current control means driving means for respectively driving the first to third current control means based on the output of the third to third filter means; and first to third current control means driving means. And first to third registers for respectively storing the reference values of the operating points.

According to a third aspect of the present invention, there is provided a semiconductor laser power control device according to the second aspect, wherein the first and second power sources are controlled before the control loop is closed and power control is started. An initialization operation of the second and third registers is performed. In the initialization operation, the set values when the outputs of the first and second current control means driving means are set to be equal to the reproduction power are respectively set to the first and second registers. 1st and 2nd
And the set value when the output of the third current control means driving means is set to be equal to the recording power is stored in the third register.

According to a fourth aspect of the present invention, there is provided a semiconductor laser power control device according to the second aspect, wherein the laser power detecting means controls a laser beam emitted from the semiconductor laser. A photodiode for receiving light; and an IV conversion circuit for converting a current output obtained from the photodiode to a voltage output, wherein the reproduction power error detection means reproduces a signal from the output of the laser power detection means. Reproducing power detecting means for extracting a power level; first A / D converting means for converting an output of the reproducing power detecting means into a digital value;
First storage means for storing a reproduction power target value;
First subtraction means for subtracting the A / D conversion result of the output of the reproduction power detection means from the reproduction power target value stored in the storage means, and calculating a reproduction power error. The recording power detection means for extracting a recording power level from the output of the laser power detection means; a second A / D conversion means for converting the output of the recording power detection means into a digital value; And a second subtraction for subtracting the A / D conversion result of the output of the recording power detection means from the recording power target value stored in the second storage means to calculate a recording power error. Means for driving the first to third current control means, the first to third current control means driving means controlling the output of the first to third filter means and the contents of the first to third registers. Each of which has first to third addition means for performing addition, and first to third D / A conversion means for respectively performing D / A conversion on the output of the first to third addition means. The first to third registers store reference values of operating points of the first to third D / A converters, respectively.

According to a fifth aspect of the present invention, there is provided a semiconductor laser power control apparatus according to the third aspect, wherein the third D / D controlling the target value of the recording power and the recording power is controlled. A table for storing the set value of the A-converting means in association with the target value of the recording power. D
The setting value of the / A conversion means is read from the table and supplied to the third register.

According to a sixth aspect of the present invention, in the semiconductor laser power control apparatus according to the fourth aspect, the third D / D controlling the target value of the recording power and the recording power is controlled. The table for storing the set values of the A conversion means in association with each other sets the plurality of set values in the third D / A conversion means before recording the actual data signal, and changes the third current. The second A / D converting the output of the recording power detecting means into a digital value when the semiconductor laser is caused to emit light by the recording power.
The output value of the conversion means and the set value of the third D / A conversion means are stored.

According to a seventh aspect of the present invention, there is provided a semiconductor laser power control apparatus according to the fourth aspect, wherein the time constant of the laser power detection means is set before recording an actual data signal. Also, when the semiconductor laser emits light with a long pulse and a pulse used in actual recording, the ratio between the respective recording power detection values is stored as a correction value, and the recording power target value is set in the actual recording power setting. The correction value is calculated, and the calculation result is stored in the second storage unit that stores the recording power target value.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a block diagram of a semiconductor laser power control apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 2 denotes a semiconductor laser (LD), which is a light source for performing recording and reproduction on an optical disk. 1 is a photodiode (P
In D), a part of the light traveling from the semiconductor laser to the optical disk is received, the optical power level applied to the optical disk is monitored, and a current proportional to the incident light is output. 3 is IV
The conversion circuit converts the output current of the PD 1 into a voltage. When reproducing the optical disk, a constant voltage value based on the optical output is used. When recording the optical disk, the optical output modulated by the recording data signal is used. Is output as a voltage waveform. Reference numeral 110 denotes a laser power detection unit that detects the power of the laser light emitted from the semiconductor laser 2, and includes the photodiode 1 and the IV conversion circuit 3.

Here, an example of the circuit configuration of the IV conversion circuit 3 is shown in FIG. In FIG. 3, 28 is an operational amplifier, 2
Reference numeral 9 denotes a reference voltage Vref of the IV conversion circuit 3, which converts an output current of the PD 1 into a voltage by an IV conversion resistor Rm.
The output voltage swings to the lower voltage side at the Vref reference voltage 29. That is, when no light is applied to PD1, the output voltage remains at “Vref”, and when light is applied, if the current of PD1 is Im, the output voltage is “Vref−Rm × I
m ”. The current-voltage conversion gain of the IV conversion circuit 3 is
Determined by the value of the IV conversion resistor Rm.
When the power is 0 mW, the IV conversion resistor Rm is trimmed or provided instead of the IV conversion resistor so that the optical output value and the output voltage value are absolutely determined to be "Vref-1V". Adjust the value by adjusting the semi-fixed resistor.

Returning to FIG. 1, first, the configuration of a reproduction power control system for controlling the reproduction current Ir and the bias current Ib in order to maintain the reproduction power Pr at a predetermined value will be described. The reproduction power control system keeps the optical output at the reproduction power Pr during reproduction, and sets the bottom value of the optical modulation output at the reproduction power P during recording.
r is maintained.

Reference numeral 4 denotes a reproduction power detection circuit in the reproduction power detection system, which amplifies the output of the IV conversion circuit 3 in accordance with the input range of the next-stage A / D converter 6 and performs level shift. During playback, the input signal is output as is,
At the time of recording, the bottom value of the modulated light output is extracted. For example, in the standard speed recording of a CD-R, the reproduction power is 0.5 mW, and the recording power is about 8 mW, depending on the disc. When the output of the IV conversion circuit 3 is adjusted to be "Vref-1V" when the optical output is 10 mW, the IV conversion circuit 3 is turned on when the recording is 8 mW.
Is "Vref-0.8 V" and "Vref-0.05 V" at the time of reproduction of 0.5 mW. On the other hand, since the input range of the A / D converter 6 is set to, for example, 0 to 5 V, I
The output level of the −V conversion circuit 3 is too low, and when operating at a power supply voltage of 5 V, Vref is １ ／ of the power supply voltage.
Of 2.5 V, and the output of the IV conversion circuit 3 is Vr
Since the output is performed at the ef reference voltage, amplification and level shift are performed so as to effectively fall within the input range of the A / D converter 6.

FIG. 4 shows an example of the circuit configuration of the reproduction power detection circuit 4. In FIG. 4, 31 is an operational amplifier, and 36 is a reference voltage VAD on the lower side of the A / D converter 6.
L and 37 are input terminals for inputting the output of the IV conversion circuit 3, and the input voltage is amplified by "R1 / R2" times and Vref
The level is shifted from the reference voltage to the VADL reference voltage.
That is, when the input voltage is Vref, the output of the operational amplifier 31 becomes VADL, and the input voltage becomes “Vref−Rm × I
m, “VADL + (R1 / R2) × (Rm × I
m) ". 33 is a sample hold switch, 34
Is a sample / hold switch control input terminal, 35 is a sample / hold capacitor, 32 is an operational amplifier, and during reproduction, the sample / hold switch control input terminal 34 is always Hi and the sample / hold switch 33 is always ON, and the output signal of the operational amplifier 31 is Is output as it is to the sample hold output 38.

On the other hand, at the time of recording, in order to sample and hold the lower power level of the modulated optical output, the sample-and-hold switch control input terminal 34 is set to a signal which becomes Hi only during the period where the optical output is low. The sample-and-hold switch 33 is turned ON only during the period where the optical output is low, and the level of the output signal of the operational amplifier 31 during the period where the optical output is low is sampled and held.
Output to

Returning to FIG. 1, reference numeral 6 denotes an A / D converter, which converts the output of the reproduction power detection circuit 4 into a digital value. Reference numeral 8 denotes a register for storing a target value of the reproduction power.
The output digital value of the converter 6 is obtained in advance, and the digital value is stored in this. A subtractor 101 subtracts the output of the A / D converter 6 from the contents of the Pr target value register 8. Numeral 120 denotes a reproducing power error calculating means for digitally detecting the reproducing power level of the laser beam from the output of the laser power detecting means 110 and calculating the reproducing power error between the reproducing power target value and the reproducing power level. , Reproduction power detection circuit 4 and A / D converter 6
, A Pr target value register 8, and a subtractor 101.

A loop filter 10 amplifies a low frequency component of an error value from a target value obtained by subtracting the output of the A / D converter 6 from the contents of the Pr target value register 8, and attenuates a high frequency component.

Here, as an example of the loop filter, I
IR (Infinite Impulse Respo)
nse) The block diagram of the filter is shown in FIG. In FIG. 7, 49 is an input of the filter, 51 is a multiplier, and multiplies the input digital value by A. 50 is the filter output, 53 is 1
The unit delay unit operates in synchronization with the A / D converter 6,
Holds the filter output value one sample before. A multiplier 52 multiplies the output value of the one-unit delay unit 53 by B times. 54
Is an adder, and outputs the result of adding the outputs of the multipliers 51 and 52 to a filter output 50.

Here, in general, the level of a low-frequency signal hardly changes for each sample, and the addition result is accumulated steadily to become a large value. Are not averaged to a very large value. By utilizing this fact, the present loop filter amplifies low frequency components and attenuates high frequency components.

Here, the multipliers are divided into two, 51 and 52, but the calculation time of the multiplication is shorter than the sampling time interval of the A / D converter 6, and the next A / D converter 6 Since there is no problem if the multiplication is completed before the sample starts, the multiplication of A times and B times is usually performed by using one multiplier in time division.

Returning to FIG. 1, reference numeral 13 denotes an Ir (reproduction current) reference value register which stores an Ir reference value and determines an Ir operating point. An adder 105 adds the digital output value of the loop filter 10 and the digital value stored in the Ir reference value register 13. Reference numeral 16 denotes a D / A converter, which is a digital output value of the loop filter 10 and an Ir reference value register 1
3 is converted to an analog value. Reference numeral 19 denotes an Ir (reproduction) current control circuit, which controls an LD based on an analog output value of the D / A converter 16.
2 is controlled. 140 is a loop filter 1
0 is a first current control means driving means for driving an Ir (reproduction) current control circuit 19 based on the output of
5 and a D / A converter 16.

A loop filter 11 amplifies a low frequency component of the loop filter 10 and attenuates a high frequency component. The loop filter 11 is configured as shown in FIG. 7 similarly to the loop filter 10, and the description thereof is the same as that of the loop filter 10, and thus the description is omitted. Reference numeral 14 denotes an Ib (bias current) reference value register which stores the reference value of Ib and determines the operating point of Ib. An adder 106 adds the digital output value of the loop filter 11 and the digital value stored in the Ib reference value register 14. Reference numeral 17 denotes a D / A converter, and 106 denotes the digital output value of the loop filter 11 and I
The digital value obtained by adding the digital value stored in the b reference value register 14 is converted into an analog value. Reference numeral 20 denotes an Ib (bias) current control circuit which controls a current value flowing through the LD 2 based on an analog output value of the D / A converter 17. Fifteen
Numeral 0 denotes second current control means driving means for driving the Ib (bias) current control circuit 20 based on the output of the loop filter 11, and is constituted by an adder 106 and a D / A converter 17.

Next, the configuration of a recording power control system for controlling the recording current Iw to maintain the recording power Pw at a predetermined value will be described. The recording power control system performs control to keep the peak value of the optical modulation output at the recording power Pw during recording. In FIG. 1, reference numeral 5 denotes a recording power detection circuit,
The output of the conversion circuit 3 is amplified and level-shifted in accordance with the input range of the A / D converter 7 at the next stage, and the value of the optical output modulated during recording is extracted. For example, in the standard speed recording of a CD-R, the recording power varies depending on the disc, but is about 8 mW.
f-1V ", the output of the IV conversion circuit 3 becomes" Vref-0.8 V "at the time of recording 8 mW. When operating at a power supply voltage of 5 V, Vref is set to 2.5 V, which is の of the power supply voltage, and the IV conversion circuit 3
Is output on the basis of Vref. On the other hand, the input range of the A / D converter is set to, for example, 0 to 5 V, and the output range of the IV conversion circuit 3 cannot be matched. Therefore, A / D
Amplification and level shift are performed so as to be effectively within the input range of the converter. The recording power detection circuit 5 has the same configuration as the reproduction power detection circuit, and FIG. 4 shows an example of a circuit diagram of the recording power detection circuit.

The circuit configuration of the recording power detection circuit is the same as the circuit configuration of the reproduction power detection circuit described above.
The only difference is that the gain of the stage of the operational amplifier 31 and the timing of the signal input to the sample and hold switch control input terminal 34 are different. The gain of the stage of the operational amplifier 31 is the resistance ratio R
Since the recording power is determined by 1 / R2, and the recording power is one or more digits higher than the reproduction power, the value of R1 / R2 of the recording power detection circuit is smaller by one or more digits than the value of R1 / R2 of the reproduction power detection circuit. Regarding the sample hold timing, in order to sample and hold the higher power level of the optical output modulated at the time of recording, the sample hold switch control input terminal 34 is set to a signal which becomes Hi only during a high optical output period during the recording data signal. Then, the sample hold switch 33 is turned on only during the period where the optical output is high, and the level of the output signal of the operational amplifier 31 during the period where the optical output is high is output to the sample hold output 38.

Returning to FIG. 1, reference numeral 7 denotes an A / D converter, which converts the output of the recording power detection circuit 5 into a digital value. Reference numeral 9 denotes a register for storing a target value of the recording power.
Is obtained in advance, and the digital value is stored. A subtractor 102 subtracts the output of the A / D converter 7 from the output of the Pw target value register 9.
130 is a recording power error calculating means for digitally detecting the recording power level of the laser beam from the output of the laser power detecting means 110 and calculating the recording power error between the target recording power value and the recording power level. , A recording power detection circuit 5, an A / D converter 7, a Pw target value register 9, and a subtractor 102.

A loop filter 12 amplifies a low frequency component of an error value from a target value obtained by subtracting the output of the A / D converter 7 from the contents of the Pw target value register 9, and amplifies a high frequency component.

The loop filter 12 is configured as shown in FIG. 7 similarly to the loop filter 10, and the description thereof is omitted because it is the same as that of the loop filter 10. Here, the multipliers of the loop filters 10, 11, and 12 will be described separately, and FIG.
In the above, the multipliers are separately described as 51 and 52.
The calculation time of the multiplication is shorter than the sampling time interval of the A / D conversion, and there is no problem if the multiplication of all the loop filters is completed before the next A / D conversion sample starts. Using the multipliers in a time-division manner, multiplications of A times and B times of the loop filters 10, 11, and 12, respectively, are performed.

Returning to FIG. 1, reference numeral 15 denotes an Iw (recording current) reference value register which stores a reference value of Iw and determines an operating point of Iw. Reference numeral 24 denotes a table of an Iw (recording current) reference value for a Pw (recording power) target value. A table of an Iw reference value for a Pw target value is obtained prior to actual recording, and stored in advance. When the target value of the recording power is determined, the target value of the recording power is set in a Pw (recording power) target value register 9, and the reference value of the recording current for the target value of the recording power is set in the Iw reference value register 15. . An adder 107 adds the digital output value of the loop filter 12 and the digital value stored in the Iw reference value register 15. 18 is a D / A converter,
The digital value obtained by adding the digital output value of the loop filter 12 and the digital value stored in the Iw reference value register 15 is converted into an analog value. Reference numeral 21 denotes an Iw (recording) current control circuit which controls a current value flowing to the LD 2 based on an analog output value of the D / A converter 18. Reference numeral 160 denotes an Iw (recording) current control circuit 21 based on the output of the loop filter 12.
, Which is a third current control unit driving unit that drives Reference numeral 22 denotes a current switch for turning on / off a recording current Iw based on a data signal 23 to be recorded and modulating the LD 2.

FIG. 5 shows an example of the circuit configuration of the Ir current control circuit 19, Ib current control circuit 20, Iw current control circuit 21, and current switch 22. First, the Ir current control circuit system will be described. 39 is an input terminal of Ir (reproduction current) control, 44 is a PNP transistor, and Ri is
r is a resistor, and these circuit elements constitute an Ir current control circuit 19. The voltage of the Ir control input terminal 39 is V (D / A1), and the base-emitter voltage of the PNP transistor 44 is Vbe. (Ir), the reproduction current Ir becomes “｛Vcc−Vbe (Ir) −V (D / A
1)｝ / Rir ”and Vbe (Ir) is a substantially constant voltage, so Ir increases as V (D / A1) decreases. Thus, the reproduction current Ir becomes I
It is controlled by the voltage of the r control input terminal 39.

Next, the Ib current control circuit system has the same configuration as the Ir current control circuit system. Reference numeral 40 denotes an input terminal for controlling Ib (bias current), 45 denotes a PNP transistor,
Rib is a resistor, and by these circuit elements, Ib
The current control circuit 20 is configured, and the voltage of the input terminal 40 for Ib control is set to V (D / A2), and the PNP transistor 45
Let Vbe (Ib) be the base-emitter voltage of
The bias current Ib is expressed as “｛Vcc−Vbe (Ib) −V
(D / A2)｝ / Rib ”, and Vbe (Ib)
Is a substantially constant voltage, so that Vb increases as V (D / A2) decreases. Thus, the bias current Ib is controlled by the voltage of the Ib control input terminal 40.

Further, the Iw current control circuit system will be described. Reference numeral 41 denotes an input terminal for Iw (recording current) control, 46
Is a PNP transistor, and Riw is a resistor. These circuit elements constitute an Iw current control circuit 21.
The voltage of the input terminal 41 of the Iw control is set to V (D / A3), PN
The base-emitter voltage of P transistor 46 is Vbe
(Iw), the recording current Iw becomes “｛Vcc−Vb
e (Iw) −V (D / A3)｝ / Riw ”,
Since Vbe (Iw) is a substantially constant voltage, V (D / A
Iw increases as 3) decreases.

As described above, the recording current Iw is controlled by the voltage of the Iw control input terminal 41. Also, 47,
48 is a PNP transistor, and 42 and 43 are control terminals of the PNP transistors 47 and 48. These circuit elements constitute the current switch 22, and / data and data are inputted to the control terminals 42 and 43. Switches between flowing the current of the PNP transistor 46 to the LD2 and flowing to the GND with the inverted differential signal. When data is Hi and data is Lo, PN
The P transistor 47 is turned on, the PNP transistor 48 is turned off, and the recording current Iw controlled by the PNP transistor 46 flows to the LD 2. Conversely, if the data is Lo,
When the data is Hi, the PNP transistor 47 is OFF,
When the PNP transistor 48 is turned ON, the recording current Iw controlled by the PNP transistor 46 flows to GND without flowing to LD2.

The operation of the semiconductor laser power control device configured as described above will be described below.
FIG. 2 shows the relationship between the current and the optical power of the semiconductor laser. The reproduction power Pr is determined by the sum of Ir (reproduction current) and Ib (bias current), and maintains the reproduction power Pr at a target value by controlling Ir and Ib. By broadening the current range of Ib and reducing the current range of Ir to high resolution, the current is roughly set by Ib, and I
It is configured to perform fine current adjustment with r. On the other hand, the recording power Pw is obtained by adding Iw (recording current) to the sum of Ir (reproduction current) and Ib (bias current) for determining the reproduction power Pr.
, And the recording power Pw is maintained at the target value by controlling the magnitude of Iw to be added.
At the time of recording, modulation is performed between two optical powers, a recording power Pw and a reproduction power Pr, depending on whether Iw is turned on or off based on a data signal to be recorded.

FIG. 6 shows the A / D of the semiconductor laser power control device according to the first embodiment of the present invention after the optical output is obtained.
The signal waveform of each part until conversion is performed is shown. In FIG. 6, the waveforms will be described in order from the one described above the paper. The LD light output is modulated based on the data signal 23, and a recording pit is formed in a section with a high light output, and no recording pit is formed in a section with a low light output. The IV conversion output is output in a low voltage direction on the basis of Vref, and has a phase opposite to that of the LD light output. A section of strong light output has a lower voltage, and a section of weak light output has a voltage close to Vref. Also, since the bandwidth of the photodiode or the IV conversion circuit is not so wide, the rise and fall of the waveform of the LD light output waveform is dull.

The waveform of the reproduction power detection is a waveform obtained by inverting and amplifying the output of the IV conversion circuit 3 in the reproduction power detection circuit 4 and level-shifting the same. VADL, VAD
H is a reference voltage of the A / D converter, and indicates that a voltage value during this period is effectively converted to a digital value. In order to make effective use of the resolution of the A / D conversion, the level of the weak light section is set to VA.
The signal is amplified with a large gain near the center between DL and VADH, and the level in the section of strong light is saturated. The level of the weak light section is determined by the reproduction power S / H.
The signal is sampled and held by the control signal, and is converted into a digital value by the A / D converter 6. Similarly, the recording power detection waveform is a waveform obtained by inverting and amplifying the output of the IV conversion circuit 3 in the recording power detection circuit 5 and level-shifting the inverted output.
DL and VADH are reference voltages for A / D conversion, and indicate that voltage values during this period are effectively converted to digital values.
In order to make effective use of the resolution of the D converter, the level in the section of strong light at the maximum recording power is amplified with a gain close to but not exceeding VADH. The signal is sampled and held by the S / H control signal, and is converted into a digital value by the A / D converter 7. In this way, the weak reproduction level is greatly amplified, and the strong recording level is slightly amplified, and the level is shifted to perform analog signal processing so as to be optimal for A / D conversion.

The output of the IV conversion circuit 3 is adjusted, for example, to Vref-1V when the optical power is 10 mW, and the gains of the reproduction power detection circuit 4 and the recording power detection circuit 5 are fixed values. The values digitized by the devices 6 and 7 are uniquely determined for the optical power. For example, assuming that the reproducing power is 0.5 mW, the digital value of the A / D converter 6 in that case is calculated in advance and stored in the Pr target value register 8. The input of the loop filter 10 is
(Pr target value) − (digital value of A / D converter 6), which is an error value from the target value.

The output of the loop filter 10 amplifies the low-frequency component of the error value and attenuates the high-frequency component. Therefore, when the optical power error is large in DC, it is amplified more than the loop filter 10. It operates so that the output optical power is largely corrected, and when pulse-like disturbance noise is added, the noise is attenuated by the loop filter 10 and does not affect the optical power.

In the conventional example shown in FIG. 16, since the loop filter is constituted by an up / down counter, even if a large error occurs, only one count is corrected. There was a risk of mis-correction if added. Therefore, by providing the loop filter 10 which amplifies the low frequency component of the error from the target value and attenuates the high frequency component, when the error is large in DC, the optical power is largely corrected, so that the higher speed is achieved. When a pulse-like disturbance noise is added, the noise component is attenuated and a control system that does not affect the optical power can be realized. While the above description has been given of the reproduction power control system, the recording power control system has the same advantages.

Next, in order to set the operating point of each current of the semiconductor laser, it is necessary to initialize each current reference value register before starting the APC operation. FIG. 9 shows an initialization flowchart of the semiconductor laser power control device.

First, at step 91, Ir
The reference value register 13 is set to the center value of the D / A converter 16. At this time, the APC operation has stopped, and Ib,
The outputs of the D / A converters 17 and 18 for controlling Iw are both zero. That is, the loop filter 10 is stopped, its output is zero, the outputs of the D / A converters 17 and 18 are zero, and the current switch 22 is off. The specific procedure is, for example, that the D / A converter 16 has an 8-bit D / A
In the case of the converter, since the range of the input digital value is 0x00 to 0xFF in hexadecimal notation, the center value is 0x
80, and 0x80 is stored in the Ir reference value register 13.

Next, in step 92, the Ib reference value is set so that the light output becomes the reproduction power. At this time,
The APC operation is stopped, the D / A converter 16 for controlling Ir is at the center value by the setting of the Ir reference value register, and the output of the D / A converter 18 for controlling Iw is zero. That is, the loop filters 10 and 11 are stopped, the output is zero, the output of the D / A converter 17 is a voltage based on the input 0x80, the output of the D / A converter 18 is zero, and the current switch 22 is OFF. State. The specific procedure is, for example, when the D / A converter 17 has an 8-bit input, increments one bit at a time starting from 0x00, and stops incrementing when the optical output reaches the reproduction power. The value of the / A converter 17 is stored in the Ib reference value register 14. To determine whether the optical output has reached the reproduction power, the digital value of the A / D converter 6 corresponding to the reproduction power is stored in the Pr target value register 8, and the Pr target value register 8 reads the A / D converter This is performed when the result of subtracting the output value of No. 6 becomes negative. At this time, if the optical output does not reach the reproduction power even if the output of the D / A converter 18 reaches the maximum value of 0xFF, the laser circuit has failed, and the initialization sequence is stopped as an error. The Ib reference value is set so that the light output becomes the reproduction power. After the setting is normally completed, the light power is equal to the reproduction power.

Finally, in step 93, a table of the Iw reference value for the Pw target value is created. At this time,
The APC operation is stopped, the D / A converter 17 for controlling Ir has the center value by the setting of the Ir reference value register 13, and the D / A converter 18 for controlling Ib has the center value. This is a value that becomes the reproduction power according to the setting of the Ib reference value register 14. That is, the loop filter 1
0 and 11 are stopped, the output is zero, the output of the D / A converter 17 is a voltage based on the input 0x80, the output of the D / A converter 18 is a voltage value serving as reproduction power, and the current switch 22 is ON. It is a state of.

The specific procedure is, for example, the D / A converter 1
When 8 is 8 bits, the input data is
Increments are sequentially made one bit at a time, and the increment is stopped when the light output reaches the maximum recording power.
In the meantime, the recording power detection circuit 5 detects the optical power,
The values of the / D converter 7 and the D / A converter 18 are stored in the Iw reference value table 24 for the Pw target value.

FIG. 10 shows an example of the Iw reference value table 24 for the Pw target value. In the actual table, the Pw target value and the Iw reference value are stored as a pair, and an example of the recording power is described for reference. This table is D /
The input data of the A converter 18 is 0x00, 0x01, 0x
.., And the value of the D / A converter 18 is stored in the item of the Iw reference value, and the corresponding A / D at that time is stored.
This is created by storing the value of the converter 7 in the item of the Pw target value. For example, when the maximum recording power is 10 m
If W is set, the output will not exceed 10 mW. Conversely, if the output exceeds 10 mW, the semiconductor laser may be damaged. Stop incrementing.

As described above, since the optical power and the conversion result of the A / D converter 7 are uniquely determined, the output of the A / D converter 7 is compared to find that the optical power reaches 10 mW. Can be detected. The created table is used by calculating and setting the set value of the Pw target value register 9 based on the target recording power, and referring to the Iw reference value table 24 for the Pw target value based on the set value and referring to the Iw reference value register 15. Set. After setting the Ir reference value register 13, the Ib reference value register 14, the Iw reference value register 15, the Pr target value register 8, and the Pw target value register 9, A
Start the PC operation.

As described above, the Ir reference value register 13, I
By providing the b reference value register 14 and the Iw reference value register 15, even if the outputs of the loop filters 10, 11, and 12 before the APC is operated are zero, almost the target reproduction power and recording power are output. Therefore, the correction amount in the APC loop can be reduced. That is, since the loop gain of the APC can be further reduced, the control system can be further stabilized.

FIG. 8 shows the characteristics of the current and the optical output of the semiconductor laser when the temperature changes. As semiconductor lasers become hotter, more current must be passed to obtain the same optical power as at lower temperatures. When the temperature rises, the optical power becomes insufficient with the current values set in the Ir reference value register 13, the Ib reference value register 14, and the Iw reference value register 15, and the outputs of the A / D converters 6 and 7 decrease. The error input to the filters 10 and 12 increases. When the error is amplified by the loop filters 10 and 12, the output of the loop filter 11 increases in response to the output of the loop filter 10. Thereby, the D / A converters 16, 17, 18
Increases, and the current values of Ir, Ib, Iw become Ir ′,
Ib 'and Iw' are increased, the characteristic change of the semiconductor laser due to the temperature rise is corrected, and the reproducing power and the recording power are kept constant.

As described above, Ir, Ib, I
w indicates the value of the Ir reference value register 13, Ib reference value register 14, and Iw reference value register 15, and the value indicating the amount corrected by the temperature rise is the loop filter 1.
Output values of 0, 11, and 12. A temperature change is detected by a temperature sensor or the loop filters 10, 11, 12
Is detected, and the previous Ir reference value register 13, I
For example, when the b reference value register 14 and the Iw reference value register 15 are changed by 10 ° C. or more or when the outputs of the loop filters 10, 11, and 12 exceed a certain level, the initialization is performed again. In addition, it is possible to correct an error due to a temperature change and control the reproducing power and the recording power with higher accuracy.

In a CD-R drive, an OPC
PCA (Power Calibration) called (Optimum Power Control)
In the area (Area), a sequence for obtaining the optimum recording power is performed prior to the actual recording.

The standard OPC method is to use PC
Using the 15 frames of A, the recording power is increased step by step for each frame and recorded, and then the recorded portion is reproduced to detect the envelope of the reproduced signal, and its peak, center, and bottom are detected. , The upper and lower symmetry of the envelope is calculated, and the recording power when the symmetry becomes substantially symmetric is determined as the optimum recording power, so that the subsequent data recording is performed with this optimum recording power. However, the area of PCA is finite and standard O
In the PC method, 15 frames are used to obtain the optimum power once, so OPC can be performed only 100 times. In addition, since the CD-R disc is a write-once medium, the portion allocated to OPC is erased. Is impossible, and cannot be reused. As described above, if OPC is performed every time data is recorded, only up to 100 additional recordings can be performed.

Therefore, in order to increase the number of times of additional writing and the number of times of OPC, one frame is divided into
It is conceivable to reduce the number of frames used in one OPC. For example, one frame is divided into four and one O
If OPC is performed by changing the recording power to a PC in 12 steps, only three frames are used in one OPC, so that it is possible to perform additional recording 500 times five times that of the standard OPC.

FIG. 11 shows an example in which one frame is divided into four. The waveform of the recording power indicates that recording is performed with the recording power increased stepwise four times in one frame, and the post-recording reproduction signal envelope is designed so that pits are strongly recorded as the recording power increases. To become
The bottom value and the center value are gradually decreasing.

Here, it is important that the recording power be switched stepwise at high speed. If the recording power is switched gently, the post-recording reproduction signal envelope also changes gently, causing a problem that the optimum recording power cannot be detected accurately. In standard speed recording, the time for one frame is 13.3 ms, and when divided into four, the time for one step of recording power is reduced to 1/4 of that, and when quadruple speed recording is performed, the time is further reduced to 1/4 of this. In this case, the time for one step of the recording power is 0.83 ms.

The semiconductor laser power control device according to the first embodiment of the present invention includes a table 24 of the Iw reference value for the Pw target value, and stores the Iw reference value for the predetermined recording power in the Iw reference value register 1 when the recording power is switched.
By sequentially setting to 5, it is possible to obtain a predetermined recording power at the same time as setting to the Iw reference value register 15 without being limited by the control band of the APC loop, and to advantageously change the recording power at high speed.

FIG. 12 shows the response of the optical output at the time of additional recording in the first embodiment of the present invention. Conventional semiconductor laser AP
In the C circuit, there is a problem that a transient response of recording power occurs in the first section at the time of additional writing, and the recording quality of the first part at the time of additional writing deteriorates. To allow a transient response of the recording power.

The semiconductor laser power control device according to the first embodiment of the present invention includes a table 24 for an Iw reference value for a Pw target value, and sets an Iw reference value for a predetermined recording power in an Iw reference value register 15. ,
Since a predetermined recording power can be obtained from the beginning of additional recording, there is an advantage that the initial recording quality at the time of additional recording can be improved,
Since a useless area of dummy data can be omitted in the first portion at the time of additional recording, the recordable capacity can be increased.

In the case of a CD-R drive, Runnin
g OPC (Running Optimum Pow)
er Control), which is a dynamic control of the recording power during recording. This is because if there is dirt such as dust or fingerprints on the medium surface, the optical power to the recording surface is attenuated, and pits cannot be formed sufficiently with a constant recording power. This is a method of detecting recording and dirt and dynamically correcting the recording power.

FIG. 13 shows the recording power and reflected light level with / without Running OPC when there is dust or dirt on the disk. This FIG.
It shows that the reflected light level fluctuates when the recording power is constant without PC,
This indicates that the recording power is dynamically controlled so that the reflected light level becomes constant when the PC is present.

The semiconductor laser power control device according to the first embodiment of the present invention includes a table 24 of the Iw reference value for the Pw target value.
5, the predetermined recording power can be obtained simultaneously with the setting in the Iw reference value register 15 without being limited by the control band of the APC loop. Therefore, the recording power can be controlled at a high speed, and R that can respond to
It has the advantage of realizing unning OPC,
This has the advantage that higher recording quality can be maintained even when there is dust or dirt.

Further, as is well known, in the reproduction of an optical disk, data is read by the intensity of reflected light, so that when the reproduction power fluctuates, noise appears in the reproduced signal,
Since the error rate at the time of data reading is deteriorated, the reproduction light used for the reproduction needs to have low noise and good S / N. When the reproduction power is controlled using a D / A converter, if the input data of the D / A converter changes by one bit, the optical power changes by one bit. Since the fluctuation of the optical power becomes a noise for the data reproducing system, it is necessary to reduce the fluctuation of the optical power of 1 bit. The D / A converter for reproducing power control of the conventional semiconductor laser control circuit shown in FIG. It was necessary to use a high-resolution multi-bit D / A converter for the device 25.

On the other hand, in the first embodiment of the present invention,
By performing two-stage control in which coarse control is performed by the bias current Ib and fine control is performed by the read current Ir, the reproduction power can be controlled by a smaller-bit D / A converter. For example, D / for controlling the read current Ir
An 8-bit D / A converter having the same output range is used for the A converter 16 and the D / A converter 17 for controlling the bias current Ib, and the current value for the control amount of the read current Ir in FIG. 5 is determined. And the value of Rib that determines the current value with respect to the control amount of the bias current Ib is set so that Rir = 16Rib, so that the current range of Ir becomes 1/16 of that of Ib, and the resolution is substantially 16 times. Become.

The output of the loop filter 10 is a correction value of Ir, and the control system of Ib is configured to amplify the low-frequency component of the correction value of Ir by the loop filter 11 and to correct Ib. The operation of Ib is performed to reduce the amount of correction of Ir. That is, when the correction amount of Ir increases, Ib is corrected, so that the narrow current range of Ir can be covered. In this example, the resolution of Ir is 16
Since the setting is doubled, the resolution is improved by 4 bits, which is equivalent to performing control using a 12-bit D / A converter.

In general, in a D / A converter, when the resolution increases by n bits, the circuit scale becomes 2 n times. Therefore, to improve the resolution by 4 bits, a circuit scale as large as 16 times is required. However, according to the first embodiment of the present invention, only two 8-bit D / A converters are provided,
That is, there is an advantage that the performance equivalent to that of the D / A converter whose circuit scale is equivalent to 16 times can be realized only by increasing the circuit scale twice.

It is desirable to use a photodiode PD1 for monitoring the optical power of the LD2, which is sufficiently fast with respect to the transfer rate of the recording data signal. Is increasing year by year, and the demand for higher speed of photodiodes is becoming more and more severe.

FIG. 14 shows an example of the output waveform of the photodiode. The time constant of the response characteristic of the photodiode is 2
There are several types, one of which is τ1 due to the junction capacitance in the PN junction, and the other is τ2 due to the diffusion time of carriers outside the depletion layer. In order to increase the speed of the photodiode, the light receiving area for reducing the junction capacitance and the semiconductor process have been improved to reduce τ1. In addition, since it is difficult to shorten τ2 itself as a countermeasure for τ2, the generation of carriers outside the depletion layer is reduced and the semiconductor process is improved so that τ2 does not occur.
As disclosed in Japanese Patent Application Laid-Open No. H11-163, light incident on the photodiode is condensed or masked so that light does not enter the surface other than the junction surface. Since all of these measures are improvements in the photodiode itself, it leads to an increase in the cost of the photodiode, and in turn, an increase in the cost of the optical disk recording / reproducing apparatus.

On the other hand, in the configuration of the first embodiment of the present invention, by applying a correction value to the value stored in the Pw target value register 9, the recording power can be accurately determined by using an inexpensive and slow response photodiode. Can be controlled.

FIG. 15 shows a waveform of the output compensation operation of the photodiode. Prior to the actual recording, a value Peak (long) in which the photodiode emits light with a pulse longer than τ2 to detect the recording power, and a value Peak in which the recording power is detected by emitting light with a short pulse used in the actual recording.
k (short) is calculated, and Peak (short
t) / Peak (long) is stored in a storage unit (not shown) as a correction value of the Pw target value register 9, and when actual recording is performed, a predetermined recording power is set in the Pw target value register 9. The correction value is read out from the storage means that does not perform the above operation, and the value stored in the Pw target value register 9 for a predetermined recording power is multiplied by the correction value.
By storing the data in the target value register 9, the recording power detection based on the response speed of the photodiode PD1 is corrected. This Peak (long), Peak (shor
When detecting t), the output of the loop filter 12 is zero, and it is necessary to set a fixed value in the Iw reference value register 15 so as not to exceed the maximum recording power, whereby Peak (long) and Peak (Shor
At the time of detecting t), the actual output light powers can be kept equal to each other.

In the above description, the A / D converter 6 and the A / D converter 7 are described as being separate from each other. By switching the A / D converters with a changeover switch, A / D conversion can be sequentially performed in a time-division manner.

The D / A converter 16 and the D / A converter 1
Although the D / A converter 7 and the D / A converter 18 are described separately, they are commonly used as one D / A converter, and the one D / A converter and the hold circuit are used in a time-division manner. It is also possible to perform D / A conversion sequentially. Further, the D / A converter is described as being 8 bits, but this may be 6 bits or 10 bits.

The constants A and B that determine the characteristics of the loop filters 10, 11, and 12 are described so that the same value is set in all the loop filters. Or a different value.

Although the reproduction power detection circuit 4 detects the reproduction level using a sample and hold circuit, the same function can be realized by holding the bottom value of the waveform using a bottom hold circuit. Similarly, the recording power detection circuit 5 detects the recording level using a sample and hold circuit. However, the same function can be realized by using a peak hold circuit.

The bottom value during reproduction and the bottom value during recording are both assumed to be 0.5 mW, and are described as being equal. However, different values are stored in the Pr target value register 8 during reproduction and during recording. By doing so, it is possible to set the reproduction power and the bottom value at the time of recording to different values.

When the table 24 of the Iw reference value with respect to the Pw target value is created, the input data of the D / A converter 18 is incremented by one bit. However, in order to shorten the initialization processing time. It is also possible to increment by two bits and obtain the value between them by interpolation, and of course, it is also possible to perform interpolation not by two bits but by n bits (n is an integer of 3 or more).

At this time, the APC operation is stopped and D
Although the A / A converter 18 was incremented, the D / A converter 18 was incremented by operating the reproduction power system APC and inputting the data signal 23 to perform modulation, and the Iw reference to the Pw target value was obtained. It is also possible to create a value table 24.

Further, in FIG. 5, Rir determining the current value with respect to the control amount of the read current Ir and the bias current I
The value of Rib that determines the current value for the control amount of b is Rir
= 16Rib, but the ratio between Rir and Rib can be set to a value other than 16 times.

As described above, according to the first embodiment, L
A PD (photodiode) 1 for receiving a part of the optical output of a D (semiconductor laser) 2 and converting the current into a current, and an IV conversion circuit 3 for converting the current of the PD 1 into a voltage. , And the bottom level control of the recording power
A reproduction power detection circuit 4 for detecting a reproduction power level or a recording power bottom level among output signals of the -V conversion circuit 3, an A / D converter 6 for converting the detected reproduction power level to a digital value, A Pr (reproducing power) target value register 8 for storing a power target value, and an A / D converted reproduction power level subtracted from the contents of the Pr target value register 8 to calculate an error from the target value of the reproduction power. A subtractor 101 that amplifies a low frequency component of the error value and attenuates a high frequency component of the error value; an Ir (reproduction current) reference value register 13 that stores a reproduction current value corresponding to a predetermined reproduction power; The loop filter 1
An adder 105 for adding the output of 0 to the contents of the Ir reference value register 13, a D / A converter 16 for converting the added digital value to a voltage, and a conversion of the output voltage of the D / A converter 16 to a current. An Ir (reproduction) current control circuit 19 for supplying a reproduction current to the LD 2, a loop filter 11 for amplifying a low frequency component of the output of the loop filter 10 and attenuating a high frequency component, and a bias corresponding to a predetermined reproduction power. An Ib (bias current) reference value register 13 for storing a current value, an adder 106 for adding the output of the loop filter and the contents of the Ib reference value register, and a D / A conversion for converting the added digital value to a voltage Converter 17 and the output voltage of the D / A converter 17 are converted to a current, and the bias current is
(Bias) current control circuit 20 for supplying the power to the I.P.M. and at the time of initialization before the reproduction power APC operation, the I.sub.
The content of the r reference value register 13 is set to approximately the center value of the output range of the D / A converter 16, the content of the Ib reference value register 14 is sequentially increased, and the bias current is increased. After the value at the time when the reproduction power level is reached is stored, the reproduction power APC operation is started.

On the other hand, the recording power is controlled by the recording power detection circuit 5 for detecting the recording power peak level in the output signal of the IV conversion circuit 3 and the A for converting the detected recording power level to a digital value. A / D converter 7, a Pw (recording power) target value register 9 for storing a target value of the recording power, and the recording power level obtained by subtracting the A / D converted recording power level from the contents of the Pw target value register 9. , A loop filter 12 for amplifying a low frequency component of the error value and attenuating a high frequency component, and an Iw reference for a Pw target value storing a list of recording currents for recording power. A value table 24,
Iw for storing the recording current value corresponding to the predetermined recording power with reference to the Iw reference value table 24 for the Pw target value
A (recording current) reference value register 15, an adder 107 for adding the output of the loop filter 12 and the contents of the Iw target value register 15, a D / A converter 18 for converting the added digital value to a voltage, Based on an Iw (recording) current control circuit 21 that converts the output voltage of the D / A converter 18 into a current and supplies a recording current to the LD 2, and a data signal 23,
A switch 22 for turning on / off the recording current; and at the time of initialization before the recording power APC operation, the switch 22 is closed and the recording current is supplied from the Iw current control circuit 21 to the LD.
2 while keeping the output of the loop filter 12 at zero, the recording current is increased by sequentially increasing the contents of the Iw reference value register to increase the optical output. At this time, the recording power detection circuit 5 Are sequentially converted into digital values by the A / D converter 7 and stored in the Iw reference value table 24 for the Pw target value. Is sequentially stored in the Iw (recording current) reference value register 15 to start the recording power APC operation, so that the recording power can be controlled at high speed. Is obtained.

Further, a low-speed and inexpensive photodiode can be used as the monitor photodiode, and the cost of the product can be reduced.

A D / A converter having a small number of bits can be used without deteriorating the error rate of the reproduced data signal.
An advantageous effect that the reproduction power can be controlled is obtained.
Accordingly, recent one-chip microcomputers are equipped with a 10-bit A / D converter and an 8-bit D / A converter, and by applying the method of the first embodiment, a special digital circuit can be realized. A semiconductor laser power control circuit can be realized simply and inexpensively with a general-purpose one-chip microcomputer without making it.

Further, Runn is used for fine dust and dirt.
ing OPC can be realized, and higher recording quality can be maintained even when there is dust or dirt on the optical disc.

According to the first embodiment, prior to actual recording, test emission is performed with a pulse sufficiently longer than the response speed of the PD 1 and a data signal used for recording, and in each case, a recording power detection circuit is used. 5 is converted into a digital value by the A / D converter 7, and the data signal used for recording from the recording power detection value at the time of test emission with a long pulse is used to determine the decay rate of the recording power detection value at the time of test emission. In the actual recording, the value obtained by multiplying the recording power value to be actually output by the obtained attenuation rate is stored in the Pw target value register 9, so that the output decrease due to the response speed of the PD 1 is prevented. There is an effect that can be corrected.

[0099]

As described above, according to the semiconductor laser power control apparatus according to the first aspect of the present invention, in the apparatus for controlling the power of the semiconductor laser used in the optical disk recording / reproducing apparatus, the The power of the laser,
A reproduction power control unit that performs digital control using two current control systems, a bias current control system that performs coarse control and a reproduction current control system that performs fine control, and a recording current reference value setting that determines a recording current operating point of a semiconductor laser. A recording current control system for digitally controlling the recording power by setting a recording current reference value by referring to the table when the recording power is changed, and a semiconductor. A semiconductor laser is emitted with a pulse longer than the time constant of the photodiode for monitoring the power of the laser and a short pulse actually used for recording, and the amount of attenuation of the power when the recording power is detected with a short pulse is stored as a correction value. Recording power correction means for digitally correcting the recording power during actual recording. There is an effect that it is possible to obtain a semiconductor laser power control device capable of controlling the over to high speed.

Further, according to the semiconductor laser power control device according to the second aspect of the present invention, a semiconductor laser for irradiating a laser beam to an optical disk on which a data signal can be recorded, and a laser beam emitted from the semiconductor laser A laser power detecting means for detecting the power of the laser light, and digitally detecting a reproduction power level of the laser light from an output of the laser power detection means, and determining a reproduction power error between a reproduction power target value and the reproduction power level. A reproducing power error calculating means for calculating, and a recording power for digitally detecting a recording power level of the laser light from an output of the laser power detecting means, and calculating a recording power error between a recording power target value and the recording power level. An error calculating means for amplifying a low frequency component of the output of the reproduction power error calculating means and attenuating a high frequency component. Filter means, second filter means for amplifying low frequency components of the output of the first filter means and attenuating high frequency components, and high frequency components for amplifying low frequency components of the output of the recording power error calculating means. Third filter means for attenuating the reproduction current, first current control means for controlling the first current for controlling the reproduction power, and second current means for controlling the reproduction power by adding to the first current. A second current control means for controlling a current; a third current control means for controlling a third current for controlling a recording power; and the second current control means based on an output of the first to third filter means. First to third current control means driving means for driving the first to third current control means, respectively, and first to third reference values for operating points of the first to third current control means, respectively. Third register Since such comprises, an effect can be obtained the semiconductor laser power control device capable of controlling the recording power at high speed.

Further, according to the semiconductor laser power control device according to the third aspect of the present invention, in the semiconductor laser power control device according to the second aspect, the first control is performed before the control loop is closed and the power control is started. , The second and third registers are initialized, and the initialization is performed by setting the output values of the first and second current control means driving means so as to be equal to the reproduction power. Since the output value of the third current control means driving means is set in the first and second registers and the output of the third current control means driving means is set to be equal to the recording power, the set value is stored in the third register. This has the effect that a semiconductor laser power control device capable of controlling the recording power at high speed can be obtained.

Further, according to the semiconductor laser power control device according to the invention of claim 4 of the present application, in the semiconductor laser power control device according to claim 2, the laser power detection means includes a laser beam emitted from the semiconductor laser. A photodiode for receiving light; and an IV conversion circuit for converting a current output obtained from the photodiode into a voltage output.
A reproducing power detecting means for extracting a reproducing power level from an output of the laser power detecting means, a first A / D converting means for converting an output of the reproducing power detecting means into a digital value, and storing a reproducing power target value. A first storage unit, and a first subtraction unit that subtracts an A / D conversion result of the output of the reproduction power detection unit from a reproduction power target value stored in the first storage unit to calculate a reproduction power error. The recording power error detecting means includes a recording power detecting means for extracting a recording power level from an output of the laser power detecting means, and a second A for converting an output of the recording power detecting means into a digital value. / D conversion means, a second storage means for storing a target recording power value, and an A of the output of the recording power detection means based on the target recording power value stored in the second storage means. Those having a second subtraction means for calculating a deduction recording power error D conversion result,
The first to third current control means driving means adds first to third outputs for adding the output of the first to third filter means and the contents of the first to third registers, respectively.
, And first to third D / A conversion means for D / A converting the outputs of the first to third addition means, respectively, wherein the first to third registers are provided. Stores the reference values of the operating points of the first to third D / A converters, so that the reproduction power can be controlled with good responsiveness by using the D / A converter having a small number of bits. There is an effect that a semiconductor laser power control device can be obtained.

Further, according to the semiconductor laser power control device of the present invention, in the semiconductor laser power control device according to the third aspect, the third value for controlling the target value of the recording power and the recording power. A table for storing the set value of the D / A converter in association with the set value of the D / A converter; Since the set value of the third D / A conversion means is read from the table and supplied to the third register, a predetermined recording power can be obtained from the beginning at the time of the additional recording for performing the additional recording on the write-once optical disk. As a result, it is possible to improve the initial recording quality at the time of additional recording, and to omit a useless area of dummy data at the first portion at the time of additional recording, thereby increasing a recordable capacity.

Further, according to the semiconductor laser power control device of the present invention, in the semiconductor laser power control device of the fourth aspect, the third value for controlling the target value of the recording power and the recording power. The table storing the set values of the D / A conversion means in association with each other sets a plurality of set values in the third D / A conversion means before recording the actual data signal, and sets the third current value in the third D / A conversion means. The output value of the second A / D conversion means for converting the output of the recording power detection means to a digital value when the semiconductor laser emits light with the changed recording power, and the output value of the third D / A conversion means. Since the set value is stored, a predetermined recording power can be obtained without being limited by the control band, and the recording power can be changed at a high speed.

Further, according to the semiconductor laser power control device of the present invention, in the semiconductor laser power control device according to the fourth aspect, it is preferable that the laser power detection means be used before recording the actual data signal. When the semiconductor laser emits light with a pulse longer than a constant and a pulse used in actual recording, the ratio of each recording power detection value is stored as a correction value, and the recording power target is set in the actual recording power setting. Since the correction value is calculated for the value and the calculation result is stored in the second storage means for storing the target recording power value, the photodiode as the laser power detection means for detecting the power of the laser beam A semiconductor laser power control device that can accurately detect the recording power and control the recording power using an inexpensive device with a slow response speed There is an effect.

[Brief description of the drawings]

FIG. 1 is a block diagram of a semiconductor laser power control device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of current and light output of the semiconductor laser according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of an IV conversion circuit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a reproduction / recording power detection circuit according to the first embodiment of the present invention.

FIG. 5 shows Ir, Ib, and Iw according to the first embodiment of the present invention.
FIG. 3 is a circuit diagram of a current control circuit.

FIG. 6 is a diagram showing signal waveforms of respective parts of the semiconductor laser power control circuit according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a loop filter according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram of current and light output of the semiconductor laser when a temperature changes according to the first embodiment of the present invention.

FIG. 9 is a diagram showing an initialization flowchart of the semiconductor laser power control device according to the first embodiment of the present invention.

FIG. 10 is a diagram showing an example of an Iw reference value table for a Pw target value according to the first embodiment of the present invention.

FIG. 11 is a diagram showing signal waveforms at the time of recording power adjustment in a PCA area according to the first embodiment of the present invention.

FIG. 12 is an explanatory diagram of an optical output waveform at the time of additional recording according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a Running method according to the first embodiment of the present invention;
Explanatory drawing of an OPC operation waveform.

FIG. 14 is an explanatory diagram of a PD output waveform according to the first embodiment of the present invention.

FIG. 15 is an explanatory diagram of a PD output compensation operation according to the first embodiment of the present invention.

FIG. 16 is a block diagram of an APC circuit of a conventional semiconductor laser.

FIG. 17 is an explanatory diagram of current and light output of an APC circuit of a conventional semiconductor laser.

[Explanation of symbols]

Reference Signs List 1 PD (photodiode) 2 LD (laser diode) 3 IV conversion circuit (current-voltage conversion circuit) 4 reproduction power detection circuit (reproduction power detection means) 5 recording power detection circuit (recording power detection means) 6 A / D1 (first A / D converter) 7 A / D2 (second A / D converter) 8 Pr (reproduction power) target value register (first storage unit) 9 Pw (recording power) target value register (Second storage means) 10 Loop filter 1 (first filter means) 11 Loop filter 2 (second filter means) 12 Loop filter 3 (third filter means) 13 Ir (regeneration current) reference value register ( 1st register) 14 Ib (bias current) reference value register (second register) 15 Iw (recording current) reference value register (third register) 16 D / A1 ( D / A converter) 17 D / A2 (D / A converter) 18 D / A3 (D / A converter) 19 Ir (reproduction) current control circuit (first current control means) 20 Ib (bias) current Control circuit (second current control means) 21 Iw (recording) current control circuit (third current control means) 22 Iw (recording current) switch 23 data signal 24 Pw (recording power) Iw (recording current) relative to target value Reference value table 28, 31, 32 Operational amplifier 29 Vref (reference voltage) 30 IV conversion output 33 Sample hold switch 34 Sample hold control signal 35 Sample hold capacitor 36 VADL (A / D conversion Lo side reference voltage) 37 Playback / recording Power detection circuit input 38 Reproduction / recording power detection circuit output 39 Reproduction current (Ir) control input 40 Bias current (Ib Control input 41 Recording current (Iw) control input 42 / Data signal (inversion) 43 Data signal 44 PNP transistor (Reproduction current control) 45 PNP transistor (Bias current control) 46 PNP transistor (Recording current control) 47 PNP transistor (Recording current) Switch) 48 PNP transistor (recording current switch) 49 Loop filter input 50 Loop filter output 51 Multiplier (A times) 52 Multiplier (B times) 53 1 unit delay unit 101 Subtractor (first subtraction means) 102 Subtractor (Second subtraction means) 110 Laser power detection means 120 Reproduction power error calculation means 130 Recording power error calculation means 140 First current control means drive means 150 Second current control means drive means 160 Third current control means drive means

Claims (7)

[Claims] An apparatus for controlling the power of a semiconductor laser used in an optical disk recording / reproducing apparatus, comprising: a bias current control system for roughly controlling the power of the semiconductor laser during reproduction; and a reproduction current control system for finely controlling the power of the semiconductor laser. A reproducing power control unit that performs digital control using two current control systems, a recording current reference value setting unit that determines a recording current operating point of the semiconductor laser, and a table of recording current with respect to the recording power of the semiconductor laser, A recording current control system that digitally controls the recording power by setting the recording current reference value by referring to the table when changing the recording power, and a pulse that is longer than the time constant of the photodiode that monitors the power of the semiconductor laser. The power when the semiconductor laser emits light with a short pulse used for recording and the recording power is detected with a short pulse. A semiconductor laser power control device comprising: a recording power correction unit that stores the attenuation of the recording as a correction value and digitally corrects the recording power during actual recording. 2. A semiconductor laser for irradiating a laser beam to an optical disc capable of recording a data signal, a laser power detecting unit for detecting a power of the laser beam emitted from the semiconductor laser, and the laser power detecting unit. A reproduction power error calculating means for digitally detecting a reproduction power level of the laser beam from the output of the laser light, and calculating a reproduction power error between the reproduction power target value and the reproduction power level; and A recording power error calculating means for digitally detecting a recording power level of the laser beam and calculating a recording power error between the recording power target value and the recording power level; and a low frequency component of an output of the reproducing power error calculating means. Filter means for amplifying the signal and attenuating the high frequency component, and amplifying the low frequency component of the output of the first filter means A second filter for attenuating high-frequency components, a third filter for amplifying low-frequency components of the output of the recording power error calculator and attenuating high-frequency components, and a first filter for controlling reproduction power. The first to control the current
Current control means for controlling reproduction power by adding the current to the first current.
A second current control means for controlling a current of the third type; and a third current control means for controlling a third current for controlling the recording power.
Current control means; first to third current control means driving means for driving the first to third current control means based on the outputs of the first to third filter means, respectively; A semiconductor laser power control device comprising: first to third registers for respectively storing a reference value of an operating point of the third current control means driving means. 3. The semiconductor laser power control device according to claim 2, wherein the first and the second control circuits are closed before a control loop is closed and power control is started.
An initialization operation of the second and third registers is performed.
The set values when the output of the current control means driving means were set were stored in the first and second registers, respectively, and the output of the third current control means driving means was set to be equal to the recording power. A semiconductor laser power control device, wherein a set value at the time is stored in the third register. 4. The semiconductor laser power control device according to claim 2, wherein said laser power detection means includes: a photodiode for receiving laser light emitted from said semiconductor laser; and a current output obtained from said photodiode. An I / V conversion circuit for converting to a voltage output, wherein the reproduction power error detection means extracts reproduction power level from an output of the laser power detection means, and the reproduction power detection means. A / D conversion means for converting the output of the digital signal into a digital value, first storage means for storing a reproduction power target value, and the reproduction power based on the reproduction power target value stored in the first storage means. First subtraction means for calculating a reproduction power error by subtracting an A / D conversion result of the output of the detection means; A recording power detection unit for extracting a recording power level from an output of the laser power detection unit; a second A / D conversion unit for converting an output of the recording power detection unit into a digital value; A second storage unit for storing a value, and a second calculation unit for calculating a recording power error by subtracting an A / D conversion result of the output of the recording power detection unit from a target recording power value stored in the second storage unit. Subtracting means, wherein the first to third current control means driving means adds the output of the first to third filter means and the contents of the first to third registers, respectively. A first to a third adding means; and a first to a third D / A converting means for D / A converting the outputs of the first to the third adding means, respectively. Stone third register, the first to third
And a reference value of an operating point of the D / A converter. 5. The semiconductor laser power control device according to claim 3, further comprising a table for storing a target value of the recording power and a set value of the third D / A converter for controlling the recording power in association with each other, In conjunction with setting the target value of the recording power in the storage means for the target value of the recording power, the set value of the third D / A converter corresponding to the target value of the recording power is read from the table and read. A semiconductor laser power control device, wherein the power is supplied to a third register. 6. The semiconductor laser power control device according to claim 4, wherein the table storing the target value of the recording power and the set value of the third D / A converter for controlling the recording power in association with each other: A plurality of set values are set in the third D / A conversion unit before actual data signal recording, and the recording power detection when the semiconductor laser emits light by the recording power with the third current changed. A semiconductor laser power control device storing an output value of said second A / D conversion means for converting an output of said means into a digital value and a set value of said third D / A conversion means. 7. The semiconductor laser power control device according to claim 4, wherein before recording the actual data signal, the semiconductor laser emits a pulse longer than the time constant of the laser power detection means and a pulse used in actual recording. The ratio of the respective detected recording power values at the time of the recording is stored as a correction value, and the correction value is calculated as the recording power target value in setting the actual recording power, and the calculation result is used as the recording power target value. The semiconductor laser power control device is stored in the second storage means.