JPH07210909A - Laser control method for magneto-optical disk device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the noise generated when the high-frequency superposition module is turned on and off from adversely affecting the playback operation. [Structure] A magneto-optical disk device in which a laser output is switched to a low output and a high frequency superposition module is turned on when reading pre-format information previously recorded on the magneto-optical disk during recording. In the laser control method for recording, the high frequency superposition module is turned on and off when the laser output is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an address or the like previously recorded on a magneto-optical disk such as an MO when information is recorded by irradiating the magneto-optical disk with laser light. The present invention relates to a laser control method at the time of recording in the magneto-optical disk device when reading the preformat information.

[0002]

2. Description of the Related Art Conventionally, in a magneto-optical disk device,
For example, when information is recorded by irradiating a laser beam on a magneto-optical disk such as an MO, as shown in FIG. 3, pre-format information recorded in advance on the magneto-optical disk, as shown in FIG. In this case, in order to read the address, reproduction is performed during data recording on the magneto-optical disk.

The output of the laser light is relatively high at the time of recording because magnetic recording is performed on the surface of the magneto-optical disk, and is reflected at the surface of the magneto-optical disk at the time of reproducing. Relatively low power is required because only the reflected light beam needs to be detected.

During reproduction, when the reflected light beam reflected by the surface of the magneto-optical disk is incident on the end face of the semiconductor laser, which is the light source of the laser light, the laser light emitted from this semiconductor laser is reflected by the above-mentioned reflection. It is modulated by the light beam. Therefore, by using a so-called high frequency superposition module equipped with a high frequency oscillator, the influence of the reflected light beam on the end face of the semiconductor laser is canceled.

According to such a laser control method for the magneto-optical disk device, when the recording mode of the magneto-optical disk device is switched to the reproducing mode, the laser output is switched to the low output and the high frequency superposition module is operated. When the reproduction mode is switched to the recording mode, the laser output is switched to the high output and the high frequency superposition module is switched off at the same time.

[0006]

However, in the magneto-optical disk device thus constructed, the laser output is switched to a low output or a high output as shown in FIG. From the time point, time t
After a delay time of 1, t2, the output will shift to low output or high output.

Therefore, when switching from the reproduction mode to the recording mode, the high frequency superposition module is turned off when the laser output is low, but when switching from the recording mode to the reproduction mode. Has a laser output
When the output is high, the high frequency superposition module is turned on.

Therefore, the influence of the switching noise when the high frequency superimposing module is turned on and off becomes significant. This makes the playback operation of the magneto-optical disk unstable,
In some cases, accurate reading of the preformatted information could not be performed.

In view of the above points, it is an object of the present invention to provide a laser control method for a magneto-optical disk device in which the on / off switching noise of the high frequency superposition module does not adversely affect the reproducing operation. There is.

[0010]

According to the present invention, the laser output is switched to a low output when pre-formatted information previously recorded on a magneto-optical disk is read during recording. A laser control method for recording in a magneto-optical disk device, wherein a high-frequency superposition module is turned on, wherein a high-frequency superposition module is turned on and off when the laser output is low. Achieved by the method.

The laser control method according to the present invention, preferably, when the recording mode is switched to the reproduction mode,
The laser output is switched to a low output, and after the laser output becomes completely low, the high frequency superposition module is turned on.

Further, the laser control method according to the present invention is preferably carried out when the high frequency superposition module is turned on and off when the laser output is detected and the laser output is below a predetermined level.

The laser control method according to the present invention is
Preferably, the high frequency superposition module is turned on at a timing delayed from the time when the laser output is switched to the low output by a time sufficient for the laser output to be the low output.

Further, according to the present invention, when the pre-format information previously recorded on the magneto-optical disk is read during recording, the laser output is switched to a low output and the high frequency superposition module is used. In the laser control method at the time of recording of the magneto-optical disk device, which is turned on, when the recording mode is switched to the reproduction mode, the laser output is switched to the low output, and after the laser output becomes completely low. This is achieved by a laser control method for a magneto-optical disk, in which the high frequency superposition module is turned on, and when the reproduction mode is switched to the recording mode, the high frequency superposition module is turned off and then the laser output is switched to the high output.

[0015]

According to the first structure, the high frequency superposition module is turned on and off when the preformat information is reproduced during recording on the magneto-optical disk with the laser output being low.

When the recording mode is switched to the reproduction mode, the laser output is switched to a low output, and when the high frequency superposition module is turned on after the laser output is completely lowered, the high frequency superposition module is switched on. Is performed with a low laser output.

Further, when the high frequency superposition module is turned on and off by detecting the laser output and when the laser output falls below a predetermined level, the laser output is detected in real time so that the laser output is detected. The high-frequency superposition module is switched on and off in a state where the output is surely low.

If the high frequency superposition module is turned on at a timing delayed from the time when the laser output is switched to the low output by a time sufficient for the laser output to become the low output, the laser output is detected. Since there is no need to do so, the configuration becomes simpler.

According to the above-mentioned second construction, when the preformat information during recording on the magneto-optical disk is reproduced, when the recording mode is switched to the reproduction mode, the laser output is switched to the low output, and the laser output is changed. After the output becomes completely low, the high frequency superposition module is turned on, and when the playback mode is switched to the recording mode, the high frequency superposition module is turned off and then the laser output is switched to the high output. Also, when the reproduction mode is switched to the recording mode, the high-frequency superposition module is switched on and off in the state where the laser output is low.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows an embodiment of a laser control unit of a magneto-optical disk device to which the present invention is applied. In FIG. 1, a laser control unit 10 includes a timing generation circuit 11 to which a recording / reproduction mode switching signal S3 from the control circuit of the magneto-optical disk device is input, and a laser output control signal S1 output from the timing generation circuit 11. To the laser control circuit 12 and the high frequency superposition module switching signal S output from the timing generation circuit 11.
It has a high frequency superposition module 13 to which 2 is input, a semiconductor laser 14 whose output is controlled by the laser control circuit 12, and a laser output detector 15 for detecting the laser output of the semiconductor laser.

As shown in FIG. 2, the timing generating circuit 11 changes the laser output control signal from the high output H to the low output L when the recording / reproducing mode switching signal is switched from the recording mode to the reproducing mode. Switch. And
After a predetermined delay time T1, the high frequency superposition module switching signal is turned on. In addition, this timing generation circuit 11
When the recording / reproducing mode switching signal is switched from the reproducing mode to the recording mode, the high frequency superimposing module switching signal is turned on, and after a predetermined delay time T2, the laser output control signal is changed from the low output L to the high output. Switch to output H.

The laser control circuit 12 operates the semiconductor laser 14 at high output when the laser output control signal from the timing generation circuit 11 is high output H,
When the laser output control signal from the timing generation circuit 11 is low output L, the semiconductor laser 14 is operated at low output. At that time, the switching from the high output to the low output or the switching from the low output to the high output is delayed by the delay times t1 and t2, respectively.
have.

Further, the high frequency superposition module 13 does not operate when the high frequency superposition module switching signal from the timing generation circuit 11 is off. Therefore, the high frequency superposition on the semiconductor laser 14 is not performed. Further, the high frequency superposition module 13 is operated when the high frequency superposition module switching signal from the timing generation circuit 11 is on, and performs high frequency superposition on the semiconductor laser 14. As a result, the influence of the reflected light beam on the end face of the semiconductor laser 14 is canceled. This eliminates the modulation of the laser light due to this reflected light beam.

The laser output detector 15 detects and measures the laser output of the semiconductor laser 14,
For example, it is composed of, for example, a photodiode, a phototransistor, etc. disposed adjacent to the semiconductor laser 14. The laser output detector 15 may be configured as a laser coupler integrally with the semiconductor laser 14, for example. The laser output detector 15 measures the delay time t1 at which the semiconductor laser 14 actually shifts to a low output when the semiconductor laser 14 is switched from a high output to a low output.

As a result, the timing generation circuit 11
Based on this delay time t1, the delay time T1 for turning on the high frequency superposition module switching signal is set to be longer than the delay time t1 of the output of the semiconductor laser 14. The delay time T2 for switching the laser output control signal to the high output H may be any timing as long as the high frequency superposition module 13 is reliably turned off.
May be zero.

The laser control unit 10 according to this embodiment is configured as described above, and its operation is performed as follows with reference to FIG.

In FIG. 2, during recording on the magneto-optical disk,
When there is preformat information, that is, an address portion in the figure, along the track of the magneto-optical disk, the recording / reproducing mode switching signal from the control circuit of the magneto-optical disk device (not shown) is switched to the reproducing mode.

As a result, the timing generation circuit 11
While switching the laser output control signal to low output L,
After the delay time T1, the high frequency superposition module switching signal is turned on.

Thus, the laser control circuit 12 controls the semiconductor laser 14 to have a low output. Therefore, the semiconductor laser 14 stabilizes at a low output after the delay time t1, after which the high frequency superposition module 13 is turned on, and the high frequency is sent from the high frequency superposition module 13 to the semiconductor laser 14 via the capacitor. It

As a result, the high frequency superposition module 13 is turned on while the semiconductor laser 14 is in a low output state, so that the noise when the high frequency superposition module 13 is turned on has a great influence on the semiconductor laser 14. There is no such thing.

In this way, the high frequency superposition module 1
The semiconductor laser 14 to which the high frequency from 3 is input is not modulated by the reflected light beam reflected on the surface of the magneto-optical disk during reproduction. Thus, the pre-format information of the magneto-optical disk can be read accurately.

After that, when the reading of the preformat information is completed, the recording / recording from the control circuit of the magneto-optical disk device is performed.
The reproduction mode switching signal is switched to the recording mode. As a result, the timing generation circuit 11 turns off the high frequency superposition module switching signal and switches the laser output control signal to the high output H after the delay time T2.

In this way, the high frequency superposition module 13 is turned off, the high frequency from the high frequency superposition module 13 is cut off, and then the laser control circuit 12 controls the semiconductor laser 14 to a high output.

As a result, the high frequency superposition module 13 is turned off while the semiconductor laser 14 is in a low output state, so that the noise when the high frequency superposition module 13 is turned off has a great influence on the semiconductor laser 14. There is no such thing. Thus, recording on the magneto-optical disk is completed.

In the above-described embodiment, the delay time T1 of the timing generation circuit 11 is set beforehand by the semiconductor laser 1
By measuring the delay time t1 at the time of switching from the high output to the low output of No. 4 by the laser output detector 15, the delay time T1 is selected to be longer than the delay time t1 of the semiconductor laser 14.

On the other hand, for example, as shown by the dotted line in FIG. 1, the detection output of the laser output detector 15 is input to the comparator 16 and is compared with the reference level by the comparator 16 to detect this detection. When the output becomes equal to or lower than the reference level, the timing generation circuit 11 may turn on the high frequency superposition module switching signal by inputting a control signal to the timing generation circuit 11.

According to this structure, even if the delay time until the output becomes low at the time of switching from the high output to the low output of the semiconductor laser 14 becomes long due to some reason, the output is surely brought to the low output. Then, the high frequency superposition module 13 is turned on, and the influence of noise when the high frequency superposition module 14 is switched on is reliably eliminated.

As described above, according to the above-described embodiment, since the high frequency superposition module is turned on and off when the preformat information is reproduced during recording on the magneto-optical disk, the laser output is low. The influence of noise when switching on and off the high frequency superposition module is reduced. Therefore, the noise of the on / off switching of the high frequency superposition module is
It does not significantly affect the laser light.

Also, when the high-frequency superimposing module is turned on after the laser output is completely reduced when switching from the recording mode to the reproducing mode, the influence of the on-switching noise of the high-frequency superimposing module is reduced. Further, when the high frequency superposition module is turned on and off, the laser output is detected, and when the laser output falls below a predetermined level,
When this is done, the high frequency superposition module is switched on and off while the laser output is certainly low.

Thus, since the high frequency superposition module is turned on and off with the laser output being low, the influence of on / off switching noise of the high frequency superposition module is reduced, so that the reproduction of the preformat information is stable. It will be able to be performed accurately in the state.
If the high frequency superposition module is turned on at a timing delayed from the time when the laser output is switched to the low output by a time sufficient for the laser output to become the low output, it is necessary to detect the laser output. Therefore, with a simpler configuration, the high frequency superposition module is turned on in a state where the laser output is low.

Further, when the reproduction mode is switched to the recording mode, after turning off the high frequency superimposing module,
When switching the laser output to high output, even if the start-up of the high frequency superposition module is off slowly,
After that, the laser output is switched to the high output, so that the high frequency superposition module can be switched off with certainty when the laser output is low, so the influence of the on / off switching noise of the high frequency superposition module is reduced. Therefore, the reproduction of the preformat information can be performed accurately in a stable state.

[0043]

As described above, according to the present invention, the high frequency superposition module is turned on and off when the preformat information is reproduced during recording on the magneto-optical disk with the laser output being low. Therefore, the noise of switching the high frequency superposition module on and off does not significantly affect the laser light and adversely affects the reproducing operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a laser control device to which the present invention is applied.

FIG. 2 is a time chart showing a relationship between a laser output control signal, a high frequency superposition module switching signal and a laser output in the apparatus of FIG.

FIG. 3 is a time chart showing a relationship between a laser output control signal, a high frequency superposition module switching signal and a laser output in a conventional laser control method.

[Explanation of symbols]

 10 laser control unit 11 timing generation circuit 12 laser control circuit 13 high frequency superposition module 14 semiconductor laser 15 laser output detector 16 comparator

Claims (5)

[Claims] 1. A magneto-optical disk device, wherein a laser output is switched to a low output and a high-frequency superposition module is turned on when reading pre-format information previously recorded on a magneto-optical disk during recording. In the laser control method for recording, a high-frequency superposition module is turned on and off when the laser output is low output. 2. The laser output is switched to a low output when the recording mode is switched to the reproduction mode, and the high frequency superposition module is turned on after the laser output becomes completely low. The laser control method described in 1. 3. The high frequency superposition module is turned on and off when a laser output is detected and when the laser output is below a predetermined level, the high frequency superposition module is turned on or off. Laser control method. 4. The high frequency superposition module is turned on at a timing delayed from the time when the laser output is switched to a low output by a time sufficient for the laser output to be a low output. 3. The laser control method according to either 1 or 2. 5. A magneto-optical disk device, which switches a laser output to a low output and turns on a high frequency superposition module when reading pre-format information previously recorded on the magneto-optical disk during recording. In the laser control method of, when the recording mode is switched to the reproduction mode, the laser output is switched to the low output, and after the laser output becomes completely low, the high frequency superposition module is turned on and the reproduction mode is switched to the recording mode. When turned off, the high frequency superposition module is turned off, and then the laser output is switched to a high output, which is a laser control method for a magneto-optical disk.