JPH03122836A - Optical disk device - Google Patents

Abstract

PURPOSE:To secure a sufficient erasing rate and to prevent a medium property from being degraded at the time of repeated erasing by changing the intensity of a light beam at the time of erasing corresponding to relative velocity between the light beam and a storing medium and executing control so that the more the relative speed is increased, the more the intensity of the light beam can be increased. CONSTITUTION:The radial position of the medium corresponding to a track 91 irradiated with a light beam 72 is detected by an optical head position detecting circuit 8 such as a variable resistor, etc., coupled with an optical head 7 and the output of the circuit 8 is supplied to a recording current control circuit 4 and an erasing current control circuit 6. Accordingly, the more the track to be recorded or erased is positioned in an outer circumference, the more the output of the optical head position detecting circuit 8 is increased and the more the output voltages of the recording current control circuit 4 and the erasing current control circuit 6 are increased. Then, the control is executed so that the intensity of the light beam 72 can be enlarged. Thus, the sufficient erasing rate can be secured and the recording property can be prevented from being changed by the repetition of many recording and erasing cycles.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical disk device having a function of erasing information recorded on a storage medium by optical means, and in particular to a magneto-optical disk device. The present invention relates to an optical erasing device suitable for rewritable optical disk devices such as the above.

[Conventional technology]

Information recording or erasing means in a magneto-optical disk device uses a light beam emitted from a laser light source and focused on a very small spot by an optical lens, and a magnetic field from a permanent magnet or an electromagnet. Information is recorded and erased by raising the temperature of a storage magnetic medium locally to near the Curie point using a focused light beam, and aligning the magnetization direction of the medium with the direction of the external magnetic field at this time.

Information is recorded by forming a reversal of magnetization, and erasing of information is achieved by forming a unidirectional magnetization direction.

On the other hand, a disc-shaped disk medium is used as a storage medium.
This is rotated at a constant rotation speed.

Further, tracks are formed in a spiral or concentric pattern on the disk medium, and the above-mentioned optical beam is aligned to the target track to be recorded or erased by track control. Therefore, the relative speed between the light beam and the medium differs depending on the track position, and the relative speed is greater at the outer circumference than at the inner circumference. When recording information, this relative speed has a particularly large effect on the reproduced signal quality, so a method is used in which the beam intensity of the light beam or the recording pulse width is optimized in accordance with the relative speed conditions.

However, in conventional devices of this kind, the light beam intensity when erasing information is not optimized for relative speed conditions, and the intensity is sufficiently high so that the erased information does not remain after erasing. and a predetermined constant value has been used regardless of relative velocity changes.

[Problem to be solved by the invention]

In the optical erasing device in the conventional magneto-optical disk device described above, an optical beam of a predetermined constant intensity has been used regardless of changes in the relative velocity between the optical beam and the medium. Therefore, with a beam intensity that ensures a sufficient erasing rate even at the outer periphery where the relative speed is high, the medium temperature rises too much in the inner periphery due to the excessive beam intensity, causing deterioration of the medium substrate or recording film. As a result, when recording and erasing cycles are repeated many times, the playback signal quality deteriorates due to changes in the recording characteristics, and the playback error rate increases.On the other hand, in order to ensure the quality of the playback signal, the number of recording and erasure cycles has to be increased. has the disadvantage that it requires restrictions.

[Means to solve the problem]

The optical disc device of the present invention solves the problems in the prior art described above, and is an optical erasing device that erases stored information on a storage medium using a focused light beam.
Relative speed detection means detects the relative speed between the light beam and the storage medium to obtain an erase position signal, and beam intensity control means receives the erase position signal and controls the intensity of the light beam. The beam intensity is controlled to a certain extent.

More specifically, in the case of a disk-shaped storage medium rotating at a constant rotational speed and a stationary light beam, the relative speed can be detected by detecting the radial position of the light beam on the storage medium as a relative speed detection means. It is specified.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. The optical head 7 includes a laser diode 71, and a light beam 72 emitted from the optical head 7 illuminates a track 91 on the magneto-optical disk medium 9. First, an external magnetic field necessary for recording or erasing is generated by the coil drive circuit 1 and the magnetic field generating coil 2 in response to a supplied recording/erase switching signal. The drive current of the magnetic field generating coil is set so that a predetermined value of the magnetic field strength is obtained on the magneto-optical disk medium 9, and the polarity of the magnetic field is switched and controlled by a recording/erasing signal.

On the other hand, the optical beam 72 at the time of recording or erasing is the optical head 7
However, there are slight differences in the beam strength and control method between recording and erasing. During recording, upon receiving the supplied recording gate signal and recording data, while the recording gate is open in the recording current control circuit 4, a control voltage corresponding to the recording beam intensity is supplied to the recording current drive circuit 3, where the recording data is Modulation is performed by the recording modulation current, and a recording modulation current is supplied to the laser diode 71 in the optical head 7. During erasing, the erase gate signal is received, and while the erase gate signal is open in the erase current control circuit 6, a control voltage corresponding to the erase beam intensity is supplied to the erase current drive circuit 5, where it is converted into an erase current. Like the recording modulation current described above, it is supplied to the laser diode 71. laser diode 71
The recording modulation current or erasing current is converted into optical output, which is focused by the optical lens in the optical head 7 and output to the optical beam 7.
2, and is irradiated onto the track 91 to be recorded or erased on the magneto-optical disk medium 9 which is being rotated at a constant speed by the spindle motor 10. The radial position of the medium corresponding to the track 91 irradiated by the light beam 72 is determined by an optical head position detection circuit 8 such as a variable resistor coupled to the optical head 7.
and its output is supplied to the recording current control circuit 4 and the erasing current control circuit 6. Therefore, the output of the culm head position detection circuit 8 where the track position to be recorded or erased is on the outer circumference becomes large, the output voltages of the recording current control circuit 4 and the erasing current control circuit 6 also become large, and the intensity of the light beam 72 becomes large. controlled to become

A second embodiment of the present invention will be described with reference to FIG.

Prior to recording or erasing, a constant drive current is supplied from the reproduction current drive circuit 113 to the laser diode 171 in the optical head 107, and the medium 109 is irradiated with a reproduction light beam. Track position information is recorded in advance on the track 191 on the medium 109 by forming changes in reflectance, etc., and this is detected by the reproduction optical sensor 173 in the optical head 107 and amplified by the amplifier circuit 111, and then the track address is detected. It is reproduced by circuit 112 to obtain a track position signal. The track position signal is the track 1910 on the medium.
Since this is a signal corresponding to the radial position, the intensity of the light beam 172 during recording or erasing can be controlled by supplying this signal to the recording current control circuit 4 and the erasing current control circuit 6, as in the first embodiment shown in FIG. is controlled by the radial position of the media.

In the above embodiments, in addition to controlling the intensity of the optical beam during erasing, the intensity of the optical beam during recording is also controlled depending on the radial position of the medium. It may also be a means of controlling.

In addition, relative speed is detected from the radial position of the medium assuming that the rotational speed of the medium is constant, but in applications where the rotational speed of the medium changes, the product of (rotational speed x medium radial position) is detected. Just add a circuit and use it to control the intensity of the optical beam.

[Effect of idea]

As explained above, the present invention changes the light beam intensity during erasing according to the relative speed between the light beam and the storage medium, and controls the culm beam intensity at which the relative speed is high to be the highest. This has the effect of ensuring a sufficient erasing rate against changes in relative velocity within the plane of the medium and preventing deterioration of medium characteristics during repeated erasing.

Output circuit, 9... Magneto-optical media, 10...
...Spindle motor, 11...Amplification circuit,
12...Track address detection circuit, 13...
... Reproduction current drive circuit, 71 ... Laser diode, 72 ... Light beam, 73 ... Reproduction light sensor, 91 ... Track.

Claims (3)

[Claims] (1) In an optical disk device having a function of erasing stored information on a storage medium using a focused light beam, a relative speed detection means for detecting a relative speed between the light beam and the storage medium; and a light beam intensity control means for controlling the intensity of the light beam according to the magnitude of the relative velocity. (2) In the optical disk device, a disk-shaped storage medium that rotates at a constant rotational speed and a light beam that is approximately stationary are used, and the radial position of the light beam on the storage medium is detected as the relative speed detection means. The optical disc device according to claim 1, characterized in that it is configured as follows. (3) The relative speed detection means is configured to include means for reproducing track position information stored in advance on a storage medium, and to detect a radial position on the storage medium from the track position information. The optical disc device according to claim 2, characterized in that: