JPH07249245A - Method of erasing information signal - Google Patents

Abstract

PURPOSE:To realize a high transfer rate and a high density recording and to stabilize the servo function by increasing the rotational speed of an optical disk and increasing a linear velocity. CONSTITUTION:A switch 21 is brought into on-state for a time t1 in one period so that a semiconductor laser 12 emits light of irradiation intensity at a prescribed emission rating and switched into off-state for a time t2 to stop the irradiation. By repeating intermittent light emission only for erasure time (t) as one period, a required information signal on a magneto-optical disk is erased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recorded information erasing method for erasing an information signal recorded on a magneto-optical disk, which is an information recording medium, by using a laser.

[0002]

2. Description of the Related Art At present, for example, a magneto-optical disk recording method is suitable as a method by which a user can directly record and rewrite an information signal. This recording method uses upward magnetization of the perpendicular magnetization film on the surface of the magneto-optical disk, which is the recording medium.
The information is recorded downward. In this case, the recording mode is a magnetic memory, but recording / reproducing and erasing are performed using laser light as a heat source.

As a method of recording information on a magneto-optical disk, initially, the magnetization direction of the perpendicular magnetization film is uniformly aligned upward. Then, laser light is emitted intermittently and irradiated to locally raise the temperature of the perpendicular magnetization film. At this time, when the temperature is increased to near the Curie temperature, the coercive force of the perpendicular magnetization film is reduced, and the magnetization is inverted by, for example, a downward magnetic field generated from an electromagnetic coil provided outside, so that information is formed.

As a method of erasing the information signal recorded on the magneto-optical disk, first, the direction of the magnetic field generated from the electromagnetic coil provided outside is set to the reverse of the recording, that is, the upward direction. As shown in FIG. 5, the perpendicularly magnetized film is continuously irradiated with laser light emitted by direct current. By doing so, the magnetization of the corresponding portion of the perpendicular magnetization film uniformly returns to the original upward direction by the same principle as that of recording.

[0005]

By the way, generally, the emission intensity, which is the maximum value, of the emission intensity of the semiconductor laser is determined in consideration of the durability of the semiconductor element and the like. At the time of erasing the information signal of the magneto-optical disk, the load on the semiconductor element, etc. is compared with the load on the semiconductor element, etc. due to the intermittent light emission at the time of recording because it is necessary to continuously emit direct current laser light as described above. The dc emission rating during erasing is inevitably lower than that during recording.

Therefore, at the time of erasing the information signal of the magneto-optical disk, the time required to raise the temperature of the perpendicularly magnetized film of the magneto-optical disk to the Curie temperature by irradiation of laser light is longer than that at the time of recording, and The upper limit of the rotation speed of the magnetic disk is determined depending on the DC light emission rating when the information signal is erased.

In order to meet the recent demands for higher transfer rate and higher density recording, the rotational speed of the magneto-optical disk is increased to increase the linear velocity and the data density per unit time is improved. It is necessary to extend the so-called OTF (Optical Transfer Function) of the optical system to the high frequency region. However, as described above, the rotation speed of the magneto-optical disk remains relatively low because the upper limit depends on the light emission rating at the time of erasing the information signal, and the desired high transfer rate and high density recording are achieved. Things are in difficult situations.

Further, when erasing the information signal recorded on the magneto-optical disk, if the laser light is made to emit direct current, laser noise such as so-called mode popping noise and return light excitation noise is generated, and the magneto-optical disk system has a problem. Servo function stability is a problem.

The present invention has been proposed in view of the above problems, and it is possible to realize a high transfer rate and a high density recording by increasing the rotational speed of an optical disk to increase the linear speed, and An object of the present invention is to provide an information signal erasing method capable of significantly improving reliability of an optical disc system by stabilizing a servo function.

[0010]

DISCLOSURE OF THE INVENTION The present invention is directed to an optical disc on which an information signal is rewritably recorded. In the present invention, such an optical disc is irradiated with intermittent emission or intensity-modulated laser light,
It is characterized in that the information signal is erased.

Further, as the optical disk, any optical disk in which the information signal is rewritably recorded as described above can be applied. In particular, a magneto-optical disk is mentioned as a suitable example to which the present invention is applied.

In this case, when the information signal recorded on the magneto-optical disk is erased, the temperature of the perpendicularly magnetized film of the magneto-optical disk is always higher than the Curie temperature.

[0013]

In the information signal erasing method according to the present invention, the information signal is rewritably recorded on the optical disc.
Since the intermittent emission or intensity-modulated laser light is emitted, it is possible to increase the emission rating, which is the maximum value of the emission intensity of the laser light, as compared with the case of direct-current emission. Therefore, the time required to raise the temperature of the optical disk to the Curie temperature is shortened by the amount corresponding to the increase in the light emission rating, and the number of rotations of the optical disk per unit time can be increased.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some specific embodiments in which the information signal erasing method according to the present invention is applied to a magneto-optical disk will be described in detail below with reference to the drawings.

First, the first embodiment will be described. In the first embodiment, when the information signal of the magneto-optical disk in which the information signal is rewritably recorded is erased, the laser light by intermittent light emission is used.

That is, by using the control circuit 1 shown in FIG. 1 to periodically irradiate / non-irradiate a desired portion of the perpendicularly magnetized film of the magneto-optical disk with a laser beam, the data is recorded on the magneto-optical disk. The information signal that was deleted is deleted.

The control circuit 1 is composed of a positive electrode terminal 11, a semiconductor laser 12, a switch circuit 13, a constant current circuit 14, a current control circuit 15, and a negative electrode terminal 16. Here, with respect to the positive electrode terminal 11 and the negative electrode terminal 16, if the potential difference between the two terminals is a value within the range in which the semiconductor laser 12 emits light, one is a positive electrode terminal or a negative electrode terminal and the other is grounded, and both are positive electrode terminals. Alternatively, or both may be negative electrode terminals.

As a method of erasing the information signal stored in the magneto-optical disk using the control circuit 1, first, the potential difference between the positive electrode terminal 11 and the negative electrode terminal 16 is within the range in which the semiconductor laser 12 emits light. A voltage of a predetermined value is applied.
At this time, the current control signal S2 from the current control circuit 15 is input to the constant current circuit 14, and the constant current circuit 14 is adjusted so that a predetermined constant current flows through the semiconductor laser 12, and the switch circuit 13 is provided. On / off operation of the switch 21 is intermittently repeated at a constant cycle based on the light emission control signal S1 input to the.

At this time, the laser light emitted from the semiconductor laser 12 is intermittently emitted as the period t1 + t2, as shown in FIG. That is, in the semiconductor laser 12, the switch 21 is turned on during a period of time t1 and emits light at an irradiation intensity of a predetermined light emission rating, and the switch 21 is turned off during a period of time t2. Irradiation is stopped. By repeating this intermittent light emission for the erasing time t with this as one cycle, the desired information signal of the magneto-optical disk is erased. At the time of erasing the information signal, in order to uniformly orient the magnetization of the corresponding portion on the perpendicular magnetization film of the magneto-optical disk to the original upward direction, during the erasing time t, the perpendicular magnetization film of the magneto-optical disk is always written. So that the temperature is above the Curie temperature,
It is necessary to define the emission rating and the times t1 and t2.

In the information signal erasing method according to the first embodiment, since the magneto-optical disk on which the information signal is rewritably recorded is irradiated with the intermittent emission or intensity-modulated laser light, direct current emission is performed. As compared with the case, the emission rating, which is the maximum emission intensity of the laser light, can be increased. Therefore, the time required to raise the temperature of the magneto-optical disk to the Curie temperature is shortened by the amount corresponding to the increase in the emission rating, and the number of rotations of the magneto-optical disk per unit time can be increased.

Since the intermittent light emission of the laser beam is used also when the information signal is recorded on the magneto-optical disk, the same light emission control signal as that at the time of erasing is used. Therefore,
The light emission control signal S1 at the time of erasing may be the same single frequency as at the time of recording or a high frequency superimposed signal at the time of reproducing.

Next, a second embodiment of the present invention will be described. The same symbols are given to members and the like corresponding to the first embodiment.

The information signal erasing method according to the second embodiment uses a magneto-optical disk as a recording medium as in the first embodiment, except that the semiconductor laser 12 emits light in a different manner.

That is, in the second embodiment, the control circuit 2 shown in FIG. 3 is used to periodically irradiate / non-irradiate a desired portion of the perpendicularly magnetized film of the magneto-optical disk with laser light. Thus, the information signal recorded on the magneto-optical disk is erased.

The control circuit 2 includes a positive terminal 11, a semiconductor laser 12, switch circuits 13a and 13b, constant current circuits 14a and 14b, and current control circuits 15a and 15.
b, and the negative electrode terminals 16a and 16b. Here, the switch circuit 13a, the constant current circuit 14a,
The current control circuit 15a and the negative electrode terminal 16a, the switch circuit 13b, the constant current circuit 14b, the current control circuit 15b,
The negative electrode terminal 16b and the negative electrode terminal 16b are arranged in parallel as illustrated. The positive electrode terminal 11 and the negative electrode terminals 16a, 1
As for 6b, as in the first embodiment, if the potential difference between these terminals is within the range in which the semiconductor laser 12 emits light, one is the positive terminal or the negative terminal and the other is the ground terminal, both of which are the positive terminals. Alternatively, or both may be negative electrode terminals.

As a method of erasing the information signal stored in the magneto-optical disk using the control circuit 2, first, the potential difference between the positive electrode terminal 11-negative electrode terminal 16a and the positive electrode terminal 11-negative electrode terminal 16b is a semiconductor. A voltage having a predetermined value within the range in which the laser 12 emits light is applied. At this time, the current control signals S3 and S4 from the current control circuits 15a and 15b are input to the constant current circuits 14a and 14b, respectively, and these constant current circuits 14a and 14b are adjusted so that the semiconductor laser 12 receives the constant current circuits. A predetermined constant current flows from each of 14a and 14b, and each switch 21a intermittently repeats the ON / OFF operation at a constant cycle based on the light emission control signal S5 input to the switch circuit 13a. Based on the light emission control signal S6 input to the switch circuit 13b, each switch 2 is operated for the erase time t.
1a is turned on.

At this time, as shown in FIG. 4, the laser light emitted from the semiconductor laser 12 is based on the emission intensity of level 2 during the erasing time t, and the emission intensity is level 1 and level from this state. Intermittent light emission of a cycle t1 + t2, which is the difference (level 1-level 2) from 2, is added.

That is, in the semiconductor laser 12, the switch 21b of the switch circuit 13b is turned on during the erasing time t to emit direct current with the emission intensity of level 2, and at the same time, is provided in parallel with the switch circuit 13b. The switch 21a of the switched switch circuit 13a thus selected causes the light emission control signal S5.
Based on the above, the on / off is repeated at a constant cycle for the erase time t. That is, during one cycle, the switch 21a and the switch 21b are turned on for the time t3, and light is emitted at the irradiation intensity of level 1 which is a predetermined light emission rating, and the time t3.
During the period 2, the switch 21a is turned off and only the switch 21b is turned on, and irradiation is performed with the irradiation intensity of level 2. This is set as one cycle, and the intensity modulated light emission is repeated for the erasing time t to erase the desired information signal of the magneto-optical disk.

During the erasing of the information signal, in order to make the magnetization of the corresponding portion on the perpendicularly magnetized film of the magneto-optical disk uniformly upward in the original direction, the perpendicular direction of the magneto-optical disk is always maintained during the erasing time t. The above-mentioned level 1 and level 2, the times t3 and t4 so that the temperature of the magnetized film becomes the Curie temperature or higher.
Need to be specified.

In the information signal erasing method according to the second embodiment, as in the first embodiment, a laser which is intermittently emitted or intensity-modulated with respect to the magneto-optical disk on which the information signal is rewritably recorded. Since light is emitted, it is possible to increase the emission rating, which is the maximum emission intensity of laser light, as compared with the case of direct current emission. Therefore, the time required to raise the temperature of the magneto-optical disk to the Curie temperature is shortened by the amount corresponding to the increase in the emission rating, and the number of rotations of the magneto-optical disk per unit time can be increased.

Here, since the intermittent light emission of the laser beam is used also when the information signal is recorded on the magneto-optical disk, the same light emission control signal as that at the time of erasing is used. Therefore, the emission control signal S5 at the time of erasing may be the same single frequency as that at the time of recording or the high frequency superimposed signal at the time of reproducing.

Although the magneto-optical disk is used as the recording medium in the first and second embodiments, the present invention is not limited to this and can be applied to other optical disks.

[0033]

According to the information signal erasing method of the present invention, the information signal is erased by irradiating the optical disk on which the information signal is rewritable with the intermittently emitted or intensity-modulated laser light. Since it is configured as described above, it is possible to increase the rotational speed of the optical disc to increase the linear velocity to realize a high transfer rate and high density recording, and to stabilize the servo function, thereby improving the reliability of the optical disc system. It is possible to significantly improve

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a control circuit for achieving an information signal erasing method according to a first embodiment.

FIG. 2 is a waveform diagram showing intermittent light emission of laser light.

FIG. 3 is a schematic diagram showing a control circuit for achieving the information signal erasing method according to the second embodiment.

FIG. 4 is a waveform diagram showing intensity-modulated emission of laser light.

FIG. 5 is a waveform diagram showing DC light emission of laser light in a conventional information signal erasing method.

[Simple explanation of symbols]

 1, 2 control circuit 11 positive terminal 12 semiconductor laser 13 switch circuit 14 constant current circuit 15 current control circuit 16 negative terminal 21 switch

Claims (3)

[Claims] 1. An information signal erasing method, which comprises erasing the information signal by irradiating an optical disc on which an information signal is rewritably recorded with intermittently emitted or intensity-modulated laser light. 2. The information signal erasing method according to claim 1, wherein the optical disk is a magneto-optical disk. 3. The information signal erasing method according to claim 2, wherein the temperature of the perpendicularly magnetized film of the magneto-optical disk is always higher than the Curie temperature when the information signal recorded on the magneto-optical disk is erased. Method.