JPH0528568A - Magneto-optical disk device - Google Patents

Abstract

PURPOSE:To prevent the information recorded in a part other than a part where information is to be erased from being destructed. CONSTITUTION:When a magnetic field generation coil 9 for erasing information generates a magnetic field with a current from a magnetic field controlling circuit 8 and when strength goes over a prescribed level, a magnetic field detecting circuit 10 outputs a power DOWN signal. At the time of receiving the signal, an LD power controlling circuit 4 deteriorates the strength of an optical beam emitted by an LD 1. Later, when the optical beam reaches the erasing part, the controlling circuit starts an erasing pawer current supplying source 6 to supply a current to generate the optical beam of erasing power to the LD 1. After erasing information, until the strength of the magnetic field goes down to below the prescribed level, the detecting circuit 10 outputs the power DOWN signal so that the LD 1 is controlled to generate an optical beam at a low power level. Consequently, necessary information is prevented from being erased before/after the optical beam reaches the erasing part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk device, and more particularly to its information erasing function.

[0002]

2. Description of the Related Art In a magneto-optical disk device, when erasing information recorded on a storage medium, a magnetic field of a predetermined intensity is applied to the storage medium in the direction of erasing the information, and the intensity of the information required for erasing is set. Information is erased by supplying a light beam from a laser diode (LD).

A more detailed description will be given with reference to FIG. When a magnetic field for erasing is supplied to the storage medium, the rise time of the magnetic field strength is longer than the rise time of the light beam strength supplied from the LD due to the inductance component of the coil that generates the magnetic field and the like. That is, even if the erase command signal (FIG. 5A) is given at timing T6 and current is immediately supplied to the coil, the magnetic field strength (FIG. 5B) does not immediately rise. Therefore, if the erasing magnetic field and the light beam of the erasing intensity are started to be simultaneously supplied to the portion to be erased on the storage medium, the rise of the magnetic field intensity is slow,
The erased part remains. Therefore, before the light beam reaches the target position, the supply of the erasing magnetic field is started at the timing T6, and at the timing T7, the magnetic field strength reaches a predetermined level, that is, a predetermined threshold value.
In step 8, a light beam having an erase intensity (erase power) is emitted. Then, the information is erased between the timings T8 and T9, and when the erasing is completed, the supply of the magnetic field is stopped at the timing T9, and the light beam intensity is returned to the steady state level, that is, the base power. The reading of the recorded information from the recording medium is performed by irradiating a light beam of base power.

[0004]

However, in such a conventional magneto-optical disk device, since the erasing magnetic field is supplied before the light beam reaches the erasing portion, the portion other than the erasing portion has a threshold value or more. A strong magnetic field is supplied and a light beam of base power is simultaneously emitted. Then, due to the dependence of the storage medium on the magnetic field, the information recorded in a portion other than the target erased portion may be destroyed. Also, immediately after the end of erasing, the fall of the magnetic field intensity lags behind the fall of the intensity of the light beam, so there is a similar problem.

An object of the present invention is to solve such a problem and to provide a magneto-optical disk device in which information recorded in a portion other than a portion from which information is to be erased is not destroyed.

[0006]

According to the present invention, information is read from a storage medium by irradiating a light beam of a first intensity, irradiating a light beam of a second intensity exceeding the first intensity and erasing. In a magneto-optical disk device that erases information recorded in a storage medium by supplying a magnetic field, magnetic field detection means for detecting the magnetic field strength of the erase magnetic field supplied to the storage medium, and the detection result by this magnetic field detection means. Based on the above, when the erasing magnetic field is equal to or higher than a predetermined intensity, the light beam is switched to an intensity lower than the first intensity,
And a light beam intensity switching means for switching the intensity of the light beam to the second intensity when erasing a predetermined erase position on the storage medium.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an example of a magneto-optical disk device according to the present invention. This device uses an LD (laser diode) 1, a PD as means for irradiating a storage medium with a light beam.
(Photodetector) 2, LD power control circuit 4, current comparator 5, erase power current supply source 6, and base power current supply source 7, and magnetic field control circuit 8 and magnetic field generation as means for supplying an erase magnetic field. The coil 9 is provided. Further, it is provided with a magnetic field detection circuit 10 for detecting the strength of the magnetic field generated by the magnetic field generation coil 9, and an erase command supply circuit 3 for giving an erase command to the controls 4 and 8.

FIG. 4 shows the configuration of this magneto-optical disk device.
FIG. 6 is a waveform diagram showing a change in intensity of a magnetic field supplied to a storage medium and a change in intensity of a light beam applied to the storage medium when erasing recorded information. The operation for erasing information will be described with reference to this figure. The state where the erase instruction supply circuit 3 does not give the erase instruction to the control circuits 4 and 8 (timing T
1 and before), the magnetic field control circuit 8 does not generate an erasing magnetic field in the magnetic field generation coil 9, while the LD power control circuit 4 is L
D1 is irradiated with a light beam having an intensity necessary for reading recorded information or address information. That is, the base power current supply source 7 supplies the LD1 with a current necessary for emitting a light beam of base power, whereby the LD1 emits a light beam of base power and irradiates the storage medium. The intensity of this light beam is PD2
Is detected by the current comparator 5 and the output current thereof is compared with the current supplied from the control circuit 4. Then, the base power current supply source is LD1 according to the comparison result.
Is adjusted to keep the intensity of the light beam emitted from LD1 constant.

In order to erase the information recorded on the storage medium, when the erase command supply circuit 3 outputs a high level erase command (FIG. 4A) at timing T1, the magnetic field control circuit 8 first causes the magnetic field generation coil 9 to operate. A current for generating a magnetic field in the erasing direction is supplied to. As a result, the strength of the magnetic field generated by the coil 9 gradually increases (FIG. 4B). The magnetic field detection circuit 10 detects the strength of the magnetic field generated by the coil 9,
When it exceeds the erasing direction magnetic field threshold value, a high level light beam base power DOWN signal is output to the control circuit 4 (FIG. 4 (c)). As a result, the control circuit 4 reduces the value of the current output to the comparator 5 to a predetermined value, and the value of the current supplied from the current supply source 7 to the LD1 decreases,
The intensity of the light beam emitted from the LD1 drops to the base power during erasing, which is lower than the base power, and is maintained at that level (FIG. 4 (d)). As a result, timings T2 to T3
Even if an erasing magnetic field is supplied to a portion other than the intended erasing portion on the storage medium during the period, the information recorded in that portion is prevented from being destroyed.

When the magnetic field strength reaches the erase magnetic field and the light beam reaches the target position, the control circuit 4 (timing T
3) The erase power generation signal is output to the erase power current supply source 6. When the current supply source 6 receives this signal, the LD
1, a drive current is supplied to the LD 1, and the LD 1 is driven by a current obtained by adding the drive current and the current from the supply source 7 to irradiate the storage medium with a light beam of erasing power. As a result, an erasing magnetic field is supplied to the storage medium, and a light beam with an erasing power is applied, so that the information recorded in the target portion is erased. After that, when the erase command supply circuit 3 stops the output of the erase command signal at the timing T4, the control circuit 4 stops the output of the erase power generation signal, and as a result, the intensity of the light beam emitted from the LD1 becomes the erase base power. Return.

On the other hand, the control circuit 8 stops the supply of the current to the coil 9 at timing T4, and thereafter the strength of the magnetic field generated by the coil 9 gradually decreases. When the magnetic field strength falls below the threshold value at timing T5, the magnetic field detection circuit 1
0 returns the light beam base power DOWN signal to the low level. The control circuit 4 thereby returns the value of the current supplied to the comparator 5 to the original value, and as a result, the LD 1 irradiates the storage medium with a light beam of base power. That is, during the period from the timing T4 to the timing T5 at which the recorded information may be destroyed, the light beam having the base power at the time of erasing is irradiated to prevent the information destruction, and thereafter the intensity of the light beam is returned to the base power. . Thus, the erase operation is completed.

The magnetic field detection circuit 10 can have various configurations. FIG. 2 shows a case where a Hall element is used. That is, the Hall element 2 is provided near the magnetic field generating coil 9.
2 is provided to detect the strength of the magnetic field generated by the magnetic field generating coil 9. When the Hall element 22 detects the magnetic field strength and outputs the corresponding voltage, it is detected by the differential amplifier 23, and the comparator 24 compares the output voltage of the differential amplifier 23 with the reference voltage to thereby obtain the optical beam base power DOW.
The N signal is output to the control circuit 4.

FIG. 3 shows a case where a current detection resistor is used. That is, the resistor 25 is inserted in series with the magnetic field generating coil 9 to obtain a current flowing through the coil 9, and thus a voltage corresponding to the strength of the magnetic field generated by the coil 9. The voltage is detected by the differential amplifier 26, and the comparator 27 outputs the light beam base power DOWN signal to the control circuit 4 by comparing the output voltage of the differential amplifier 26 with the reference voltage.

[0014]

As described above, in the magneto-optical disk device of the present invention, the magnetic field supplied to the storage medium for erasing information reaches a sufficient accuracy, and thereafter, until the light beam reaches the erased portion. The intensity of the light beam applied to the storage medium can be suppressed to a level lower than usual. Further, the intensity of the light beam is similarly suppressed to a low level until the intensity of the magnetic field reaches a sufficiently low level after the information erasing is completed. Therefore, in the magneto-optical disk device of the present invention, the information recorded in the portion other than the target portion for erasing information will not be destroyed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a magneto-optical disk device according to the present invention.

FIG. 2 is a block diagram showing in detail a magnetic field detection circuit that constitutes the magneto-optical disk device shown in FIG.

FIG. 3 is a block diagram showing in detail another example of a magnetic field detection circuit constituting the magneto-optical disk device of FIG.

FIG. 4 is a waveform diagram for explaining an information erasing operation of the magneto-optical disk device of FIG.

FIG. 5 is a waveform diagram for explaining an information erasing operation of the conventional magneto-optical disk device.

[Explanation of symbols]

1 LD (laser diode) 2 PD (photo detector) 3 Erase command supply circuit 4 LD power control circuit 5 Current comparator 6 Erase power current supply source 7 Base power current supply source 8 Magnetic field control circuit 9 Magnetic field generating coil 10 Magnetic field detection circuit 22 Hall element 23,26 differential amplifier 24,27 comparator 25 resistance

Claims (3)

[Claims] 1. A storage medium by irradiating a light beam of a first intensity to read information from a storage medium, irradiating a light beam of a second intensity exceeding the first intensity and supplying an erasing magnetic field. In a magneto-optical disk device for erasing information recorded on a recording medium, magnetic field detecting means for detecting the magnetic field strength of the erasing magnetic field supplied to the storage medium, and the erasing magnetic field is determined based on the detection result by the magnetic field detecting means. Above the intensity of
And a light beam intensity switching means for switching the intensity to a second intensity when the light beam erases a predetermined erase position on the storage medium. Magnetic disk device. 2. The magneto-optical disk device according to claim 1, wherein the magnetic field detecting means includes a Hall element for detecting the magnetic field strength of the erasing magnetic field. 3. The magneto-optical disk device according to claim 1, wherein the magnetic detection means includes a current detection means for detecting a current for generating the erase magnetic field.