JPH10289462A - System and method for laser output control of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk laser output control system and method capable of improving the countermeasure capability to external disturbances by reducing the variation of RF signal levels for each optical disk. SOLUTION: The level of an RF signal S corresponding to a reflected laser light L2 from an optical disk 9 is compared with a reference voltage V 0 in a level comparator 3, and its difference voltage signal ΔS is outputted to a level amplifier 4. In the level amplifier 4, the level amplified signal S2 of the difference voltage signal ΔS is outputted to an adder 5 and added with a power signal S1 emitted from a photodetector 2. Then, based on a level signal S3 indicating this adding result, an APC servo amplifier 6 changes the resistance value of a variable resistor 10 so that the level of the RF signal S becomes the reference voltage V0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk laser output control system and method for controlling the output of a laser beam emitted from a laser diode to an optical disk.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional laser output control system for an optical disk. In FIG.
Reference numeral 100 denotes a laser diode (hereinafter, referred to as “LD”) that emits a laser toward the optical disc 200, and is connected to a constant voltage supply 102 via a variable resistor 101. Reference numeral 103 denotes an APC (Automatic
Power Controler), the input side of which is connected to the photodetector 104. With such a configuration, LD1
00 is detected by the photodetector 104 and APC
103 changes the resistance value of the variable resistor 101 based on the detection value from the photodetector 104 so that the output of the laser beam emitted to the optical disk 200 is kept constant.

[0003]

However, the above-mentioned conventional laser output control system for an optical disk has the following problems. Since the configuration is such that the output of the LD 100 is only constant, the level of the RF signal based on the reflected laser from the optical disc 200 depends on the characteristics of the optical disc 200. Therefore, the level of the RF signal depends on the material of the optical disc 200 or the like.
Each time, the variation is different, and a hardware margin must be widened to cope with the variation in the RF signal level.

An object of the present invention is to provide a laser output control system for an optical disk in which the variation in the RF signal level of each optical disk is reduced to improve the ability to cope with disturbances. It is an object.

[0005]

In order to solve the above-mentioned problems, a laser output control system for an optical disk according to the present invention has a laser oscillating section for irradiating a laser beam to the optical disk and a laser oscillation unit for reflecting laser light from the optical disk. A level comparing section for comparing the level of the RF signal with a fixed reference level; and adjusting the output power of the laser oscillation section based on the comparison result of the level comparing section so that the level of the RF signal becomes substantially equal to the reference level. And a control unit.
With this configuration, when the laser beam is irradiated from the laser oscillation unit onto the optical disc, the RF corresponding to the reflected laser beam
The level of the signal and a reference level are compared by a level comparing unit. Then, the control section adjusts the output power of the laser oscillation section based on the comparison result of the level comparison section so that the level of the RF signal becomes substantially equal to the reference level. Thereby, even if the reflected laser light from the optical disk fluctuates, the level of the RF signal is always kept constant.

Further, in the laser output control method for an optical disk according to the present invention, the optical disk is irradiated with a laser beam, the level of the RF signal corresponding to the laser beam reflected from the optical disk is compared with a predetermined reference level, and the RF signal is controlled. The output power of the laser beam is adjusted so that the level of the RF signal is substantially equal to the reference level based on the comparison result between the reference level and the reference level.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a laser output control system for an optical disk according to an embodiment of the present invention. As shown in FIG. 1, a laser output control system for an optical disc according to this embodiment includes an LD 1 as a laser oscillation section, a photodetector 2, a level comparator 3 as a level comparison section, a level amplifier 4, an adder 5, a control section. APC servo amplifier 6 is provided.

[0008] The LD 1 outputs the emitted laser light L to the optical disc 9.
1 is a device for irradiating 1 and is connected to a constant voltage supply source 11 via a variable resistor 10. That is, by changing the resistance value of the variable resistor 10, the constant voltage
, And the output power of the laser light L1 emitted from the LD 1 can be controlled.

The photodetector 2 has a function of receiving the output laser light L1 from the LD 1 and outputting an output power signal S1 indicating the power of the output laser light L1 as a voltage.

[0010] The level comparator 3 is connected to the output side of an RF signal generator 30 composed of a photodetector or the like. R
The F signal generator 30 has a function of generating an RF signal S based on the reflected laser light L2 from the optical disc 9, and the level comparator 3 outputs the reflected laser light L2 generated by the RF signal generator 30. And has a function of comparing the levels by inputting the same. Specifically, a constant reference voltage V0 (reference level) is compared with the voltage level of the RF signal S, and a difference voltage signal ΔS is generated.

The level amplifier 4 is connected between the level comparator 3 and the adder 5, and has a function of amplifying the difference voltage signal ΔS from the level comparator 3. Specifically, when the difference voltage signal ΔS is negative, the reference voltage V0
And outputs a level amplified signal S2 obtained by amplifying the difference voltage signal ΔS to a voltage value obtained by adding the absolute value of the difference voltage signal ΔS to the reference voltage V0. A level amplified signal S2 obtained by amplifying the difference voltage signal ΔS to a voltage value obtained by subtracting the absolute value is output.

An adder 5 adds the level amplified signal S2 from the level amplifier 4 and the output power signal S1 from the photodetector 2, and outputs a level signal S3 indicating the added voltage.
Is output to the APC servo amplifier 6.

A limiter 50 is connected to the adder 5, and the output power signal S from the photodetector 2 is
The addable upper limit value of the adder 5 is determined based on 1 so that the voltage value of the level signal S3 is not saturated.

The APC servo amplifier 6 has a function of increasing or decreasing the output power of the emitted laser light L1 based on the level signal S3 from the adder 5. Specifically, based on the voltage value indicated by the level signal S3 from the adder 5, the LD1 emits the emitted laser light L1 such that the level of the RF signal S becomes equal to the reference voltage V0 of the level comparator 3. And has a function of changing the variable resistor 10.

Next, the operation of the laser output control system for an optical disk according to this embodiment will be described. In addition,
The laser power control system is capable of operating the laser power control system during operation.
Further, the laser output control method according to claim 4 is specifically achieved. In the initial state, the output power of the laser light L1 emitted from the LD 1 is constant. Therefore,
In this state, the level of the RF signal S generated based on the reflected laser light L2 from the optical disk 9 is equal to the reference voltage V0 of the level comparator 3, and the voltage value indicated by the difference voltage signal ΔS from the level comparator 3 is It is zero. Therefore, the value indicated by the level amplified signal S2 from the level amplifier 4 is V0, and the level signal S3 obtained by adding the output power signal S1 from the photodetector 2 and the level amplified signal S2 in the adder 5 is constant and changes. There is no. As a result, APC
No adjustment of the variable resistor 10 by the servo amplifier 6
The output power of the output laser light L1 from No. 1 does not change.

In this state, when the optical disk 9 is replaced or the ambient temperature of the optical disk 9 changes, the reflected laser light L
2 changes, the R signal from the RF signal generator 30 changes.
The level value of the F signal S also changes. For example, assuming that the level of the RF signal S has decreased by ΔV, the RF signal S is compared with the reference voltage V0 in the level comparator 3, and ΔV
Is output to the level amplifier 4.
Thus, the level amplified signal S2 in the initial state is obtained.
The level amplified signal S2, which is increased by the value ΔV indicated by the difference voltage signal ΔS, is output from the level amplifier 4 to the adder 5. Then, the level amplified signal S2 from the level amplifier 4
And the output power signal S1 from the photodetector 2 are added in the adder 5, and a level signal S3 which is increased by ΔV from the level signal S3 in the initial state is output to the APC servo amplifier 6. As a result, the change amount Δ of the RF signal S
The APC servo amplifier 6 changes the variable resistor 10 so that the output laser light L1 having an output power increased by an amount corresponding to V is output from the LD1. Thereby, the level of the RF signal S from the RF signal generator 30 increases by ΔV and becomes equal to the reference voltage V0.

As described above, according to the laser output control system of this embodiment, even if the power of the reflected laser beam L2 changes due to a change in the material of the optical disk 9, a change in the ambient temperature, noise, or the like, the RF signal generator 30 RF from
Since the level of the signal S is always maintained at the reference voltage V0, it is possible to cope with disturbance without taking a wide margin of hardware.

[0018]

As described above in detail, according to the present invention, even if the reflected laser light from the optical disk fluctuates, the level of the RF signal is adjusted to be substantially equal to a constant reference level. There is an effect that various disturbances can be dealt with without increasing a hardware margin.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a laser output control system for an optical disk according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional laser output control system for an optical disk.

[Explanation of symbols]

1 LD, 2 photo detector, 3 level comparator, 4 level amplifier, 5 adder, 6 APC
Servo amplifier, 10: variable resistor, 11: constant voltage supply source, 30: RF signal generator, L1, L2: laser beam, S: RF signal, ΔS: difference voltage signal.

Claims (4)

[Claims] A laser oscillator for irradiating the optical disc with a laser beam; a level comparing section for comparing a level of an RF signal corresponding to the reflected laser beam from the optical disc with a fixed reference level; A control unit for adjusting an output power of the laser oscillation unit such that a level of the RF signal becomes substantially equal to the reference level based on a comparison result. 2. A laser output control system for an optical disk according to claim 1, wherein said level comparing section generates a level difference between a level of said RF signal and said reference level, and said level comparator. And a level amplifier for amplifying the level difference generated in the above to a level obtained by adding the reference level to the level difference, wherein the control unit adjusts the level of the RF signal based on the addition result of the level amplifier. A laser output control system for an optical disk, wherein the output power of the laser oscillation unit is adjusted to be substantially equal to the reference level. 3. An optical disk is irradiated with laser light, a level of an RF signal corresponding to the reflected laser light from the optical disk is compared with a fixed reference level, and a comparison result between the level of the RF signal and a reference level is obtained. Adjusting the output power of the laser beam so that the level of the RF signal becomes substantially equal to the reference level based on the output signal. 4. The laser output control method for an optical disk according to claim 3, wherein a level difference between the level of the RF signal and the reference level is generated, and the level difference is added to the level difference. A method for controlling the output power of the laser beam based on the amplification level so that the level of the RF signal is substantially equal to the reference level.