JPH03235223A - Semiconductor laser defect detector - Google Patents

Abstract

PURPOSE:To detect the defect of a semiconductor laser and to prevent information tracks or information on a recording carrier from being damaged by switching laser power to recording power before executing focus control, and operating a laser defect discriminating means according to the detection signal of a light quantity detector. CONSTITUTION:A laser defect discriminating means 7 is composed of a microcomputer equipped with a central arithmetic unit, etc., and after confirming the raising of rotation speed for a disk 5, a laser power control circuit 1 is switched to the recording power control according to the detection signal from a rotation detector 4 before executing the focus control. When it is detected by the detection signal of a light quantity detector 3 that the semiconductor laser can not output the quantity of light necessary for recording, a focus control circuit 8 is not driven but the semiconductor laser is stopped being driven. At such a time, since focus is not loaded even when outputting the recording power from the semiconductor laser, power concentration on a disk 5 is small and nothing is recorded onto the information tracks.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser defect detection device for a recording device that records information on a record carrier using a semiconductor laser.

Conventional technology Semiconductor lasers used in recording light sources such as disk-shaped record carriers (hereinafter referred to as disks) that optically record information deteriorate over time and due to shocks such as static electricity, and the rate of deterioration is faster than the rate at which the elements deteriorate. Although it is possible to output the amount of output light (reproduction power) necessary for reproduction, the amount of output light (recording power) required for recording cannot be output during recording, which requires an output 5 to 10 times the reproduction power. This defect may occur.

Because of this, conventional semiconductor laser defect detection devices measure the amount of light emitted from the rear exit of the semiconductor laser during recording.
By detecting a shortage in the amount of emitted light relative to the drive current of the semiconductor laser, defects in the semiconductor laser are detected and recording defects are prevented.

Problems to be Solved by the Invention However, in the conventional semiconductor laser defect detection device described above, defects in the semiconductor laser are detected during recording, and defects such as an insufficient amount of emitted light are discovered after information is written to the record carrier. In addition to information loss due to missed recording timing, playback is not possible with devices that use record carriers that can only record once, such as write-once discs (C/N
This has led to the problem of recording signals with poor signal quality (e.g., signals with poor signal quality), producing defective information tracks on the record carrier and causing damage to the user.

The present invention differs from the above-mentioned conventional 17? It is an object of the present invention to provide a semiconductor laser defect detection device which can solve the ff problem and prevent loss of information tracks and information on a record carrier L.

Means for Solving the Problems In order to solve the above problems, the semiconductor laser defect detection device of the present invention includes a laser power control circuit that controls the output of the semiconductor laser, and detects whether the amount of laser emitted light is below a specified value. and a laser defect determining means that switches the laser power control circuit to recording power control and selects whether or not to drive the focus control circuit based on the detection signal of the light amount detector.

Furthermore, in addition to the above configuration, the semiconductor laser defect detection device of the present invention includes a rotation detector that detects whether the rotational speed of the disc-shaped record carrier is equal to or higher than a specified value when the record carrier is disc-shaped. After confirming the rise of the rotation speed of the disc-shaped record carrier using the detection signal from the rotation detector, the laser defect determination means switches the laser power control circuit to recording power control, and performs focus control using the detection signal from the light amount detector. The configuration is such that it is possible to select whether or not to drive the circuit.

Effect With the above configuration, before performing focus control, when the laser power is switched to recording power and the light intensity detector detects that the semiconductor laser cannot output the amount of light necessary for recording, at this time, the semiconductor laser outputs the recording power. Since it is not in focus even though it is emitted, the power density on the record carrier is small and thus no information track is recorded. Therefore, a defective semiconductor laser can be detected without losing information tracks or information.

Furthermore, after the rotation detector detects that the rotation speed of the disc-shaped record carrier is equal to or higher than a specified value, the laser defect determination means is activated, so that the power density of the laser beam irradiated onto the disc-shaped record carrier can be adjusted. It is much smaller and there is less loss of information tracks and information.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a professional diagram of a semiconductor laser defect detection device showing an embodiment of the present invention.

In FIG. 1, a laser power control circuit 1 uses feedback control using the rear exit of the semiconductor laser in the optical head 2 to control the laser drive current so as to keep the amount of laser light constant during recording/reproduction. . light 1
The detector 3 converts the amount of light emitted from the rear exit of the semiconductor laser in the optical head 2 into a voltage. A decrease in the amount of light emitted from the semiconductor laser is detected by comparing it with the voltage. The rotation detector 4 performs frequency-voltage conversion on the FG signal of the disk motor 6 that drives the disk 5 and compares it with a reference voltage to detect whether the rotation speed of the disk has exceeded a specified value. The laser defect determination means 7 includes a central processing unit, a read-only memory storing a program, and a write/write memory.
It consists of a microcomputer equipped with a readable memory, an input/output board, etc., and after confirming the rise of the rotational speed of the disk 5 based on the detection signal from the rotation detector 4, the laser power control circuit 1 is set to control the recording power. The optical head 2 is switched by the detection signal of the light amount detector 3.
It is selected whether or not to drive the focus control circuit 8 that performs focus control.

The laser defect determining means 7 is executed by a program shown in FIG.

That is, when the optical disk 5 starts to start up and the disk motor 6 starts rotating, the program of the laser defect determining means 7 is executed. In FIG. 2, first, in step 10, the output of the rotation detector 4 is monitored from the microcomputer input port, and it is waited for the rotation speed of the disk motor 6 to exceed a certain value. When the rotational speed increases, the process proceeds to step 20, where an instruction is sent to the laser power control circuit 1 from the output port to switch to recording power output control and urge the semiconductor laser to emit an appropriate amount of recording light. At this time, if the semiconductor laser is deteriorated, the amount of emitted light is small, so the laser power control circuit 1 increases the driving output and the driving current of the semiconductor laser in order to increase the amount of emitted light. In step 30, the output of the light intensity detector 3 is monitored through the input port, and if the output light amount is less than the specified value, it is determined that the semiconductor laser is defective, and step 40 is executed; If the semiconductor laser is determined to be normal, step 60 is executed.

In step 40, a command is sent to the laser power control circuit 1 from the output port to stop driving the semiconductor laser. Thereafter, in step 50, a flag indicating that there is a defect in the semiconductor laser is set, and the operation of the laser defect determining means 7 is terminated. Semiconductor laser defect flag is 7y! -, abnormality response processing such as abnormality display is executed in a later abnormality processing program.

On the other hand, if it is determined that the semiconductor laser is normal, in step 60, a command is sent to the laser power control circuit 1 from the output port to switch the drive output of the semiconductor laser to reproduction output control. After resetting the flag indicating that there is a defect, the focus control circuit 8 is driven in step 80, the operation of the laser defect determining means 7 is terminated, and tracking control is performed to start up the optical disk recording at 9 kg. Perform recording/playback.

In this embodiment, the semiconductor laser is inspected after the disk 5 starts to rotate in order to minimize the power density of the laser beam irradiated onto the disk, but the inspection is performed when the disk is loaded or when the disk is not loaded. It is also possible to perform the test when the power is turned on for a recording device that is not installed.

Furthermore, it can also be used in a recording device that uses a card-like record carrier or a tape-like record carrier as a record carrier.

Effects of the Invention As described above, according to the present invention, semiconductor laser defects can be inspected before focusing, that is, before actual information is recorded, when loading a record carrier such as an optical disk or when starting up a recording device. Therefore, it is possible to prevent loss of information tracks due to recording of signals that cannot be reproduced correctly and loss of information due to missed recording timing, and it is possible to provide a highly safe recording device using a semiconductor laser.

Furthermore, since the laser defect determination means is activated after the rotational speed of the disc-shaped record carrier exceeds a specified value, the power density of the laser beam irradiated to the disc-shaped record carrier can be further reduced, resulting in greater safety. will improve.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a semiconductor laser defect detection device showing an embodiment of the present invention, and FIG. 2 is a flowchart showing a program of the laser defect determination means of FIG. 1... Laser power control circuit, 2... Optical head,
3... Light amount detector, 4... Rotation detector, 5... Disk, 7... Laser defect determination means, 8... Focus control circuit.

Claims (1)

[Claims] 1. A laser power control circuit that controls the output of the semiconductor laser, a light amount detector that detects whether the amount of laser emitted light is below a specified value, and the laser power control circuit that controls the recording power. A semiconductor laser defect detection device comprising: a laser defect determination means for switching and selecting whether or not to drive a focus control circuit based on a detection signal from the light amount detector. 2. A rotation detector is provided for detecting whether the rotation speed of the disk-shaped record carrier is equal to or higher than a specified value, and the laser defect determination means detects the rotation speed of the disk-shaped record carrier based on the detection signal from the rotation detector. 2. The semiconductor laser defect detection device according to claim 1, wherein after confirming the rise, the laser power control circuit is switched to recording power control, and it is selected whether or not to drive the focus control circuit based on a detection signal from a light amount detector.