JPH0562276A - Magneto-optical recording device - Google Patents

Abstract

PURPOSE:To execute stable fixed magnetic field optical modulation overwrite by eliminating the fluctuation of an applying magnetic field due to circumstance at the time of recording. CONSTITUTION:When the recording is executed by irradiating the magneto- optical disk with a recording beam 2, a magnetic field detecting element 5 is set near a position where the recording is executed and the magnetic field is monitored. A detected signal is sent to a discrimination circuit 6 and the result of discrimination is fed back to an applying magnetic field controller 4, then the magnetic field is controlled so as to be in a range where the overwrite is executed in good condition. The magnetic field is controlled so that accuracy is <=10Oe, thus optical intensity modulation in fixed magnetic field can be stably executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magneto-optical recording for recording, reproducing and erasing information using an energy beam such as a laser beam, and particularly, under a fixed applied magnetic field,
It is suitable for a magneto-optical recording method that overwrites by light intensity modulation.

[0002]

2. Description of the Related Art Overwriting methods in magneto-optical recording include a magnetic field modulation method and an optical modulation method.

In the magnetic field modulation method, the magneto-optical recording film is continuously irradiated with light to heat the recording portion with irradiation light energy, and at the same time, a magnetic field modulated based on information to be recorded is applied. To reverse the magnetization of the magneto-optical recording film to perform overwriting (see, for example, JP-A-60-251539).
No.). In the magnetic field modulation overwrite method, a magnetic field generating electromagnet capable of switching a magnetic field having an intensity of several hundred Oe at high speed is required. Therefore, the magnetic field applying mechanism in the recording / reproducing apparatus becomes complicated.

On the other hand, a method using a two-layer magnetic film (Japanese Patent Laid-Open No. 62-175948) has been devised as one of methods of performing overwriting by a light modulation method. This method
A recording medium composed of two layers of magnetic films magnetically coupled by exchange interaction is used, and the recording film is initialized by applying a magnetic field for initialization every time recording is performed. The two-layer magnetic film system has a drawback that the recording / reproducing apparatus tends to be large in size because a magnet having an intensity of several kOe must be incorporated in the apparatus as an initializing magnet.

As another method for performing overwriting by light modulation, an overwriting method using a fixed magnetic field [23. IEEE Trans. Magnetics MA
G23) 1987, pp. 171-173]. In this method, a recording magnetic domain is formed with a laser pulse having a predetermined time width, a laser pulse having a time width shorter than the laser pulse is irradiated onto the recording magnetic domain to extinguish the existing recording magnetic domain, and the length of the optical pulse is shortened. Direct overwriting by modulating. The present invention relates to this magneto-optical recording method for performing overwriting with a fixed magnetic field.

[0006]

In the fixed magnetic field overwrite method, since recording and erasing are performed with the same magnetic field, the fixed magnetic field overwrite method is sandwiched between the magnetic field region where recording is exclusively performed and the magnetic field region where erasing is exclusively performed. The magnetic field applied to the recording medium must be set in a narrow magnetic field region. If the magnetic field deviates from this narrow area to the recording dominant side, existing information cannot be sufficiently erased during overwriting. On the other hand, if the magnetic field deviates toward the erasing dominant side, recording will not be sufficient and the signal output will decrease. In this way, the range of the magnetic field that can be recorded and erased is about 50 Oe [Japanese Journal of Applied Physics (Japan.J.Appl.Phys.), Vol.28, Suppl.28-3 (1).
989) pp.33 and Journal of Applied Physics (J.Appl.Phys.), Vol.67 (199).
0), pp. 4423]. Further, among them, the region where good recording and erasing characteristics are obtained is limited to a width of about 10 Oe. That is, in order to realize fixed magnetic field overwrite magneto-optical recording, it is necessary to control the applied magnetic field with an accuracy of about 10 Oe or more. This magnetic field accuracy is large enough to be easily affected by leakage magnetic fields from parts inside the device and environmental magnetic fields outside the device. It is possible that it will come off. It is an object of the present invention to provide a magneto-optical recording apparatus which does not change the magnitude of the magnetic field applied to the magneto-optical recording medium due to changes in the environment, excluding the above drawbacks.

[0007]

The above object is to detect the strength of a magnetic field applied to a medium by a magnetic field detecting element, feed back the detection signal to a magnetic field applying mechanism, and adjust the magnetic field applying mechanism to adjust the recording medium. It is achieved by using a magneto-optical recording device which has the function of controlling the magnetic field applied to the device so that it is always within a predetermined specific range.

[0008]

1 is a conceptual diagram of a magneto-optical recording apparatus using the present invention. Recording is performed by irradiating the recording beam 2 on the magneto-optical disk 1. At this time, the magnetic field applying mechanism 3 applies a magnetic field to the recorded portion of the magneto-optical disk 1. The intensity of this magnetic field can be controlled by the applied magnetic field controller 4. The magnetic field detection element 5 is placed in the vicinity of the position where the recording is made, and the magnetic field is monitored. The detected signal is
The magnetic field at the recording position is sent to the judgment circuit 6 to judge to which side and how much the magnetic field at the recording position deviates from the optimum magnetic field for overwriting. The result of this determination is fed back to the applied magnetic field controller 4, and the magnetic field applying mechanism 3 is moved in the direction to correct the deviation.
Adjust the state of. By operating such a feedback mechanism, the magnetic field at the time of recording can be kept within a range in which overwriting is always performed well.

As the magnetic field detecting element, a hall element, a magnetoresistive element or the like can be used. An example of a method of adjusting the applied magnetic field is a method of using an electromagnet as the magnetic field applying mechanism 3 and controlling the current flowing through the electromagnet. Alternatively, a method of adjusting the applied magnetic field is also possible by using a permanent magnet as the magnetic field applying mechanism 3 and changing the distance or direction to the medium or changing the magnetic field circulation path. The method using an electromagnet has an advantage that control can be performed at a high speed, whereas the method using a permanent magnet has an advantage that power consumption of the device can be reduced.

[0010]

The present invention will be described in detail with reference to the following examples.

(Embodiment 1) FIG. 2 shows a conceptual diagram of a magneto-optical recording apparatus of Embodiment 1. As a magnetic field applying mechanism, an electromagnet 8
To use. The strength of the magnetic field can be controlled by changing the current supplied to the electromagnet 8 in the electromagnet power supply 9. Hall element 10 as a magnetic field detection element
To use. The detected Hall voltage is compared with the voltage of the reference voltage generator 12 in the comparator 11, and it is determined by which side and how much the magnetic field at the recording position deviates from the optimum magnetic field for overwriting. It The result of this determination is fed back to the electromagnet power source 9 to adjust the current supplied to the electromagnet 8 in a direction to correct the deviation. By operating such a feedback mechanism, it is possible to control the magnetic field at the time of recording so that the magnetic field is always within the range in which overwriting is favorably performed. In this method, if the inductance of the electromagnet 8 is sufficiently small, it is possible to correct a magnetic field component that changes at high speed up to about 1 kHz, and for example, it is also possible to correct a leakage magnetic field from an actuator on the optical head. Due to the sensitivity and long-term reliability of the Hall element, it is possible to easily control the magnetic field with an accuracy within 10 Oe by the method of this embodiment.

(Embodiment 2) FIG. 3 shows a conceptual diagram of a magneto-optical recording apparatus of Embodiment 2. Similar to the first embodiment, the electromagnet 8 is used as the magnetic field applying mechanism and the Hall element 10 is used as the magnetic field detecting element. The magnetic field control method and detection method are
This is the same as in the first embodiment. In this embodiment, the Hall element 10
Is mounted on the optical head 13 near the objective lens 15. The optical head 13 moves on the rail 14 in accordance with the position of the track to be recorded. At this time, the Hall element 10 also moves with the optical head 13. With this mechanism, the position of the Hall element can always be placed near the position where recording is performed, and the relative positional relationship between the recording position and the Hall element can always be kept the same. As a result, the applied magnetic field can be controlled with the same accuracy regardless of which track is recorded on the magneto-optical disk.
Further, if this mechanism is used, even if the magnetic field generated by the electromagnet is not uniform in the radial direction of the disk and has a distribution, the current to the electromagnet will be adjusted so as to correct it. It is possible to control so that the optimum magnetic field for overwriting is always applied to the recording position during recording.

(Embodiment 3) FIG. 4 shows a conceptual diagram of a magneto-optical recording apparatus of Embodiment 3. The permanent magnet 16 is used as a magnetic field applying mechanism. The magnetic field strength is controlled by moving the position of the permanent magnet 16 via the gear 18 and the rack 19 by the DC motor 17 to change the distance between the surface of the magneto-optical disk 1 and the permanent magnet 16. The magnetic resistance element 20 is used as the magnetic field detection element. The magnetic field signal converted into the voltage is compared with the voltage of the reference voltage generator 12 in the comparator 11, and how much to which side the magnetic field at the recording position deviates from the optimum magnetic field for overwriting, To be judged. The result of this determination is fed back to the DC motor drive power source 21, and the position of the permanent magnet 16 is moved in the direction to correct the deviation. By operating such a feedback mechanism, the magnetic field at the time of recording can be kept within a range in which good overwrite is always performed. Unlike the case of the first embodiment, this method is not suitable for correcting a magnetic field component that fluctuates at high speed, but by using a permanent magnet instead of the electromagnet, the power consumption of the device can be reduced.

[0014]

According to the present invention, the magnetic field applied to the magneto-optical recording medium can be controlled with an accuracy of 10 Oe or less, whereby the light intensity modulation overwriting with a fixed magnetic field can be performed with an environmental magnetic field or the like. There is an effect that it can be performed stably without being affected by changes.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a magneto-optical recording device using the present invention.

FIG. 2 is a conceptual diagram of a magneto-optical recording device according to a first embodiment.

FIG. 3 is a conceptual diagram of a magneto-optical recording device according to a second embodiment.

FIG. 4 is a conceptual diagram of a magneto-optical recording device according to a third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magneto-optical disk, 2 ... Recording beam, 3 ... Magnetic field application mechanism, 4 ... Applied magnetic field controller, 5 ... Magnetic field detection element, 6 ... Judgment circuit, 7 ... Disk rotation axis, 8 ... Electromagnet, 9 ... Electromagnet power supply 10 ... Hall element, 11 ... Comparator, 12 ... Reference voltage generator, 13 ... Optical head, 14 ... Rail, 15 ... Objective lens, 16 ... Permanent magnet, 17 ... DC motor, 18 ... Gear, 19 ... Rack, 20 ... Magnetoresistive element, 21 ... DC motor drive power supply.

Claims (4)

[Claims] 1. In a magneto-optical recording apparatus including an optical head and a magnetic field applying mechanism for applying a magnetic field to a recording medium, the intensity of the magnetic field applied to the recording medium is detected by a magnetic field detecting element, and the detection signal is detected. Feedback to the magnetic field application mechanism,
A magneto-optical recording apparatus having a function of controlling a magnetic field applied to a recording medium so that it is always within a predetermined specific range by adjusting a magnetic field applying mechanism. 2. The magneto-optical recording apparatus according to claim 1, wherein the magnetic field detecting element is a Hall element or a magnetoresistive element. 3. A magnetic field detecting element is mounted on an optical head, and when the position of a track to be recorded on the recording medium moves, the magnetic field detecting element also moves together with the optical head to always record on the recording medium. The magneto-optical recording apparatus according to claim 1, wherein the magnetic field is detected near the position where the magnetic field is generated. 4. The magneto-optical recording apparatus according to claim 1, wherein the magnetic field applying mechanism is an electromagnet.