JPS5984355A - Optical disk device - Google Patents

Abstract

PURPOSE:To assure high reliability of a disk without destruction of data on a disk even under an abnormal condition, by detecting an abnormal condition in the number revolution of the disk and stopping or lowering a recording light in accordance with the detect signal. CONSTITUTION:The number of revolution of a motor 11 for rotating a disk 12 is detected by a motor driving circuit 13 and the output 1 of the circuit 13 and the output 2 of a reference output generating circuit 10 are inputted into a number of revolution comparing circuit 3. The circuit 3 compares whether the number of revolution of the disk 12 is in an allowable variation range or not and, when the number of revolution is out of the range, a rotation normal signal 4 becomes false and the signal is inputted into a laser output controlling circuit 6 together with a laser output ''on'' signal 5, a laser driving circuit 8 does not work even when the laser output ''on'' signal 5 is real and a laser diode 9 does not emit lights. Therefore, data on the disk 12 are not destructed even under an abnormal condition and a high reliability can be guaranteed to the disk 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical disk device, and more particularly to a recording/reproducing light output control system suitable for protecting data on a disk when the rotation of the disk decreases or stops during reproduction.

[Prior art]

Conventionally, in optical disk devices capable of recording and reproducing, a low-power laser beam is incident on the disk during playback.
A reproduction signal is obtained from the reflected light, and during recording, a laser beam with a power several times higher than that of reproduction is pulsed according to the recorded information, and the irradiation creates holes called bits in the recording film on the disk. information is recorded. FIG. 1 is a diagram showing the laser output during reproduction and recording. For example, when the rotational speed of the disc is set to 8 Hz, the laser output during reproduction P1? ::1rTTw, the laser output P2 during recording is 6 to 7 rryw, and the pulse width is 150n.
It is about s.

For the recording film formed on the disk, it is desirable to use a recording film material with good recording sensitivity so that recording can be performed with as low a laser power as possible in order to make it possible to apply a low-output laser device. On the other hand, from the perspective of information reproduction,
In order to increase the signal-to-noise ratio of the reproduced output signal due to reflected light, it is desirable to perform reproduction by irradiating the laser beam with the highest possible power, but in this case, the recording film may be destroyed by the laser output during reproduction. Never let anything happen to you. Therefore, in optical disk devices, we use a recording film that allows information to be written without placing an excessive burden on the laser device, and in order to improve the noise characteristics of the reproduced signal, we use a recording film that is as large as possible without destroying the recording film. It is necessary to perform reproduction using output laser light. Conventionally, the output of the recording/reproducing laser beam set in this manner was turned on/off regardless of the rotational speed of the disk. Therefore, no problem occurs when the disk is rotating normally, but if the disk rotation speed decreases or the disk stops while the laser light is on, recording pulses may not be generated. However, since the irradiation energy per unit area on the recording film becomes large, there is a problem that the recording film is destroyed by the reproduction laser beam.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an optical disk device that guarantees high reliability of the disk without destroying the data on the disk even in the event of an abnormality such as rotational fluctuation of the disk. With the goal.

[Summary of the invention]

In order to achieve the above objectives, the present invention detects the number of revolutions of a disk drive motor, and immediately suspends recording and reproducing operations when the number of revolutions changes from a steady value by more than a certain allowable range. , the laser output is turned off.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 shows an embodiment of the laser output control method of the present invention. The disk 12 is rotated by the motor 11.

A reference output generation circuit 10 for detecting the motor rotation speed by the motor drive circuit 15 and comparing the output 1 with it.
The output 2 is input to the rotation speed comparison circuit 3. The rotation speed comparison circuit compares whether the rotation of the disk is within the allowable variation range, and if it is outside the range, a rotation normal signal 4 is output.
becomes false. This signal is input to the laser output control circuit 6 together with the laser output on signal 5, and even though the laser output on signal 5 is true, the normal rotation signal 4 is false, so the laser drive circuit 8 is It does not work, so no current is supplied to the laser diode 9 and no light output occurs. The input/output relationship of these signals is as shown in FIG. T
In section 1, the rotation normal signal 4 is true, but the laser output on signal is false, and the laser 9 does not generate a first-out signal. In the interval T, the normal rotation signal 4 is true and the laser output on signal is true, so the laser 9 generates a reproduced light output PRt.

In the section T, the laser output ON signal is true, but the normal rotation signal is false, so the laser output ON signal is true.
produces no light output. Incidentally, the V-laser output control circuit 6 may be designed so that the rotation normal signal 4 is false and the laser output is lowered than the normal value.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in an optical disk device capable of recording and reproducing, even if the rotational speed of the disk decreases or stops due to some abnormality during playback, there is no possibility of erroneous recording on the disk. The data protection function is improved and a highly reliable optical disk device can be realized.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between laser output during recording and playback, Fig. 2 is a block diagram of an embodiment of the laser beam output control circuit of the present invention, and Fig. 3 is a diagram showing the relationship between signals of each part. It is a diagram. 1...Disc rotation detection output, 2...Reference sword, 3
... Rotation speed comparison circuit, 4... Rotation normal signal, 5. Laser output on signal, 6. Laser output control circuit, 8.
... Laser drive circuit, 9... Laser diode.

Claims (1)

[Claims] In an optical disk device consisting of an optical head for optically recording and reproducing information on a disk and a rotation drive unit for rotating the disk, a state in which the rotation speed of the disk decreases or has stopped is detected, and a detection signal is used to detect , an optical disk device whose characteristic is to stop or reduce the incidence of recording light and reproduction light on the disk.