JPS63146236A - Laser beam controller for optical disk - Google Patents

Abstract

PURPOSE:To prevent misrecording to other track or miserasing of something by cutting out the laser beam output of switching over to the reproduction output when the output from an accelerosensor becomes bigger than a set value. CONSTITUTION:The device consists of an accelerosensor 1 and such a criterion as to whether a mechanical shock in imposed on an optical disk device in more than a certain degree of its strength is judged by an output of the sensor 1 to either cut out the output of a laser 6 or switch over to the output in reproduction mode in the event of the output of the sensor 1 exceeding a predetermined set value. Incidentally, even if maltracking is taken place, the laser output is already lowered or cut off at that time so that no malfunction of miscrecording or miserasing is ever happened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser control device for an optical disc in an optical disc device.

2. Description of the Related Art In recent years, optical disk devices capable of recording information signals at high density have come into use. These methods change the reflectance of the recording medium by focusing a laser beam on the recording surface of the disk and making holes in the recording medium, or by changing the material structure of the recording medium with the heat of the laser beam, and reproduce the information. The principle of obtaining is used. Recently, alloys of rare earths and transition metals have been used as recording media, and the direction of magnetization of the recording media is reversed by heating with a laser beam. During reproduction, continuous laser beams with a light intensity several times lower than that of recording are used. Magneto-optical disks, which utilize the fact that the Kerr rotation angle of the reflected light changes depending on the direction of magnetization when irradiated with light, are also being actively developed. This magneto-optical disk has the feature that it is capable of not only recording and reproduction but also erasing. In addition, there are optical discs that utilize phase change to enable recording, reproduction, and erasing.

Incidentally, in these optical disk devices, grooves or pits are provided on the disk, and tracking is performed to a target track using diffracted light by the grooves or pits. Generally, the diffraction-order light is received by a two-split detector, and the differential output is used to drive the objective lens for tracking.

Problems to be Solved by the Invention However, as described above, grooves or pits are provided on the disk and tracking is performed using diffracted light by the grooves or pits, so mechanical disturbances such as sudden vibrations can occur. There was a problem in that if the track was added, track jumping would occur. Especially during recording or erasing, if such disturbances are applied to the device, the optical head may move or the objective lens of the optical head may move, causing tracking to be lost and another track to be recorded or erased. Ta.

An object of the present invention is to provide a laser control device for an optical disc that does not destroy data even when the above-mentioned sudden mechanical disturbance, so-called shock, is applied to the optical disc device.

Means for Solving the Problems In order to achieve this object, the laser control device for optical disks of the present invention has an acceleration sensor, which is used for writable optical disk devices at the time of writing, and for writable optical disk devices at the time of writing. It consists of means for cutting off the laser output or switching to the output for reproduction when the output from the acceleration sensor becomes larger than a preset value during writing and erasing.

It is determined whether or not a certain amount of mechanical shock has been applied to the optical disk device based on the output from the acceleration sensor, and if the output from the acceleration sensor exceeds a preset value, Turn off the laser output or switch to the output for playback.

Therefore, even if tracking is lost, the laser output has already been lowered or turned off at that time, so there will be no possibility of erroneous recording or erasing of another track.

Example 11i Otsu > A block diagram of a disk laser control device is shown.

In FIG. 1, 1 is an acceleration sensor, 2 is a voltage amplifier,
3 is a voltage comparator, 4 is a reference voltage generator, 6 is a laser drive control device, and 6 is a laser. Each of the above components is incorporated into the optical disk device.

The operation of the optical disc laser control device configured as described above will be described below.

When a mechanical shock is applied to the optical disk device during recording or erasing, the acceleration sensor 1 generates a voltage according to the applied shock, this voltage is amplified by the voltage amplifier 2, and the voltage from the reference voltage generator 4 is and is compared by voltage comparator 3. When the voltage from the voltage amplifier 2 becomes larger than the voltage from the reference voltage generator 4, the voltage comparator 3 generates a control signal.

When the control signal from the voltage comparator 3 is generated, the laser drive control device 5 stops the current to the laser 6 or lowers the amount of current to lower the laser power to the power for reproduction. On the other hand, when the mechanical impact is small and the output from the acceleration sensor 1 is small, the output from the voltage amplifier 2 is also small, so the reference voltage is not reached and the voltage comparator 3 does not generate a control signal.

In this case, the laser drive control device 5 supplies a normal recording or normal erasing current to the laser 6.

Next, an example of the laser drive control device 6 will be explained in more detail using the block diagram of FIG. The case shown in FIG. 2 is an example in which the laser emission is stopped when an abnormal mechanical shock is applied. In FIG. 2, 6 represents a laser drive control device, 6 is a laser, 7 is a current limit switch, 8 is a current limit switch 70 control signal input terminal, 9 is a recording current control circuit, and 1o is a recording signal input terminal. , 11 is an erase current control circuit, 12 is an erase signal input terminal, 13 is a reproduction current control circuit, 14 is a reproduction signal input terminal, and 15 is a laser power supply terminal. In the above configuration, each current control circuit 9, 11 at the time of recording.

Among the recording current control circuits 13, only the recording current control circuit 9 operates and controls the current of the laser 6 in accordance with the signal from the recording signal input terminal 10. At this time, the erasing and reproducing current control circuits 11 and 13 are in a cutoff state because their respective signal input terminals 12 and 14 are off. On the other hand, when erasing and playing,
Each current control circuit 11 or 13 works. these are,
The signals at the erase signal input terminal 12 and the reproduction input terminal 14 act together, respectively, and the laser drive current flows so as to provide the laser power necessary for erasing or the laser power necessary for reproduction. Next, when a mechanical shock above a certain level is applied to the optical disk device, a control signal from the voltage comparator 3 is applied to the control signal input terminal 8, and the current limit switch 7 is cut off. Therefore, during recording or reproduction, the current to the laser 6 is cut off and the laser 6 stops emitting light. By setting the voltage from the reference voltage generator 4 in FIG. 1 to a voltage slightly lower than that at which the optical disk device causes track jump due to impact, it is possible to stop the laser emission before track jump occurs. Become.

Although not mentioned here, the acceleration sensor 1 may be of a piezoelectric type using a piezoelectric element, an electrodynamic type that uses changes in magnetic flux crossing a coil, an electrostatic type that uses changes in capacitance, or a strain type. It is possible to use a strain gauge type using a gauge or the like; it is also possible to use a plurality of acceleration sensors 1 to react to impacts in any direction.

Further, in this embodiment, one laser is used for each of recording, reproduction, and erasing, but the same control can be performed even when separate lasers are used for each.

Effects of the Invention The present invention detects a mechanical shock applied to an optical disc device by providing an acceleration sensor in the optical disc device.
By quickly reducing or shutting off the laser output, even if tracking is lost, erroneous recording to another track or erasing can be prevented, increasing the safety of the optical disc device. It is something that can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a laser control device for an optical disk according to an embodiment of the present invention, and FIG. 2 is a block diagram of a laser drive control device section of the same. 1... Acceleration sensor, 2... Voltage amplifier, 3... Voltage converter, 4... Reference voltage generator, 6... Laser drive control device, 6...
...Laser, 7...Current limit switch, 8
... Control signal input terminal, 9 ... Current control circuit for recording, 1o ... Signal input terminal for recording,
11... Erasing current control circuit, 13...
・Regeneration current control circuit.

Claims (1)

[Claims] An acceleration sensor is arranged in a writable or writable-erasable optical disk device, and the output from the acceleration sensor is set in advance at the time of writing in the writable optical disk device and at the time of writing and erasing in the writable-erasable optical disk device. 1. A laser control device for an optical disc, comprising means for cutting off laser output or switching to output for playback when the laser output becomes larger than a predetermined value.