JPH05347042A - Method for magneto-optical recording - Google Patents

Abstract

PURPOSE:To improve a transfer rate by monitoring the sum signal obtained from the signal taken out of a reflected diffraction light from a magneto-optical recording medium through a bisected photodiodes in recording operation. CONSTITUTION:In such a magneto-optical recording method, recording is performed by the magnetic field modulation system applying modulated magnetic field and irradiating the laser light whose recording power is kept constant on the magneto-optical recording medium. Recording control is executed by monitoring a sum signal or a differential signal obtained from the signal taken out of the reflected diffraction light from the magneto-optical recording medium through the bisected photodiodes 11, 13. Consequently, the number of defects and a defective length are measured by monitoring the sum signal in recording operation, when the defective length incapable of correction or the number of defects more than specified number in a sector is present, recording is executed again on the alternate sector while recording is terminated without verification if nothing is wrong.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording method using a magnetic field modulation method.

[0002]

2. Description of the Related Art A magnetic field modulation method is one of recording methods of a magneto-optical recording method. This system is a system in which recording is performed by applying a modulated magnetic field to a magneto-optical recording medium and irradiating a laser beam whose recording power is kept constant. In the magneto-optical recording method using the magnetic field modulation method, since overwriting is possible, the erasing process that has been conventionally required is not necessary, and two processes of recording and verifying are performed, which has the advantage of increasing the transfer rate. Hold.

[0003]

However, in order to meet the recent demand for high-speed information processing, it is necessary to further increase the transfer rate. For that purpose, the disk rotation speed is increased and the linear density is increased. There are ways to raise it, but there are limits. Furthermore, when overwriting on old data, if data is recorded with a lower recording power than that when old data is recorded, unerased data may remain and errors may occur frequently.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a magneto-optical recording method capable of further improving the transfer rate and capable of reliable overwriting. The purpose is to provide.

[0005]

In order to achieve the above object, according to the present invention, a magnetic field for recording by applying a modulated magnetic field to a magneto-optical recording medium and irradiating a laser beam whose recording power is kept constant. In a magneto-optical recording method using a modulation method, a sum signal obtained from a signal obtained by extracting reflected diffracted light from a magneto-optical recording medium through a two-division photodiode is monitored during a recording operation, and recording is performed based on the result. The present invention provides a magneto-optical recording method characterized by deciding whether to end recording or to perform recording again in a different area. Further, according to the present invention, in the above, a constant threshold value is provided for the sum signal, and a section in which the monitored sum signal exceeds the threshold value is defined as a defect section, and a pulse corresponding to the section. The number of defects and the length of the defect in the magneto-optical recording medium are obtained by measuring the width of the clock with a clock, and based on the obtained results, it is possible to decide whether to end the recording or to perform the recording again in a different area. A featured magneto-optical recording method is provided. Further, according to the present invention, in a magneto-optical recording method by a magnetic field modulation method for performing recording by applying a modulated magnetic field to a magneto-optical recording medium and irradiating with laser light whose recording power is kept constant, during a recording operation, The difference signal obtained from the signal obtained by extracting the reflected diffracted light from the magneto-optical recording medium through the two-division photodiode is monitored, and based on the result, the recording is ended or the recording condition is changed and the recording is performed again. There is provided a magneto-optical recording method characterized by deciding whether to perform. Further, according to the present invention, in the above, a constant threshold value is provided for the difference signal, and when the monitored difference signal exceeds the threshold value, the recording laser power is increased to perform the recording again. A magneto-optical recording method is provided.

[0006]

When the medium has a defect, the signal intensity fluctuates, and the difference signal becomes large reflecting the possibility that there is an unerased portion. Therefore, by monitoring the sum signal or the difference signal (both may be used) during the recording operation, it is possible to know the defect status and the unerased status, and re-record in another sector according to the status. Appropriate processing such as increasing the laser power and re-recording can be performed. Therefore, the transfer rate can be improved and reliable overwrite can be realized, and the above problems can be solved.

[0007]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 is a diagram schematically showing an optical system of a magneto-optical recording / reproducing apparatus. 1 is a semiconductor laser (LD), 2 is a collimator lens, 3 is a beam shaper, 4 is a second beam splitter, and 5 is a first beam splitter. Beam splitter, 6 is a mirror prism, 7 is an objective lens, 8 is a half-wave plate, 9 is a polarization beam splitter, 10 is a collimator lens, 11 is a first photodiode, 12 is a collimator lens, and 13 is a second lens. It is a photodiode of. According to the method of the present invention, recording is performed by a magnetic field modulation method in which a modulated magnetic field is applied to a magneto-optical recording medium and a laser beam whose recording power is kept constant is applied to perform recording, and reflection diffraction from the magneto-optical recording medium is performed. Photodiode that splits light into two (11 and 13 in Fig. 1)
The recording is controlled by monitoring the sum signal or the difference signal obtained from the signal taken out via. Here, the sum signal is the first
Is a signal obtained by summing the output of the photodiode 11 and the output of the second photodiode 13, and the difference signal is the first
Is a signal obtained by taking the difference between the output of the photodiode 11 and the output of the second photodiode 13. Normally, the sum signal is used to read the ID existing as prepits on the medium, and the difference signal is used to reproduce the recording mark recorded magneto-optically.

First, the control by the monitor of the sum signal will be described. When a magneto-optical recording medium is irradiated with laser light whose recording power is kept constant, a sum signal of signal intensities (V in FIG. 2) according to the reflectance of the medium is obtained. As shown in FIG. 2, this sum signal changes in signal strength when the medium has a defect.
Therefore, if a threshold value is set for the signal strength of this sum signal, a section that exceeds the threshold value is set as a defect section, and the pulse width corresponding to that section is measured by a clock, the number of defects in the medium is determined. , The defect length can be obtained. Therefore, the sum signal is monitored during the recording operation to measure the number of defects and the defect length of the medium, and if the defect length is uncorrectable or the number of defects in a certain sector exceeds a certain level, the replacement sector Re-record to, and if there is no such case, the recording ends without verification. In order to enable such control, for example, a first circuit that inputs a sum signal to the drive side and measures a section in which the level exceeds a threshold value by a clock, and a measurement by the first circuit The contents of the second circuit and the third circuit are compared with the second circuit that stores the number of defects and the defect length that are stored, the third circuit that stores the number of defects and the defect length that are allowed in advance. To finish recording without verifying,
It suffices to provide a fourth circuit for determining whether to perform re-recording on the alternate sector. The design itself of each circuit having such a function can be performed using a known technique.

Next, the control by monitoring the difference signal will be described. As shown in FIG. 3, the difference signal obtained during the recording operation has a high medium temperature in front of the spot and a low temperature in the rear of the spot due to heat conduction of the medium in the region inside the laser spot. Since the magnetization disappears in the area above the Curie temperature (Tc), the difference signal appears in the area where old data is recorded in the area behind the spot. When the recording power is low, the signal intensity obtained from the rear area of the spot is high, but when the recording laser power is high, the signal intensity decreases because the Curie temperature approaches. Therefore, a threshold value is set for this difference signal, and when the signal strength of the difference signal exceeds the threshold value, for example, the recording power is increased and recording is performed again. The signal strength can be reduced or completely erased, and overwrite can be surely performed. To enable such control, for example,
A circuit for determining whether or not the level of the difference signal exceeds a threshold value by inputting the difference signal to the drive side and a circuit for changing and rewriting to an appropriate recording power when the level of the difference signal exceeds the threshold value. A circuit for instructing recording may be provided. The design itself of each circuit having such a function can be performed using a known technique.

[0010]

As described above in detail, according to the present invention, by monitoring the sum signal or the difference signal, it is possible to perform a defect inspection and an unerased inspection during the recording operation, and thereby verify. It is not necessary, the transfer rate can be further improved, and reliable overwrite is possible.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an optical system of a magneto-optical recording / reproducing device.

FIG. 2 is an explanatory diagram of control by monitoring a sum signal.

FIG. 3 is an explanatory diagram of control by monitoring a difference signal.

[Explanation of symbols]

1 Semiconductor Laser 2 Collimator Lens 3 Beam Shaper 4 Second Beam Splitter 5 First Beam Splitter 6 Mirror Prism 7 Objective Lens 8 1/2 Wave Plate 9 Polarization Splitter 10 Collimator Lens 11 First Photodiode 12 Collimator Lens 13 Second photodiode

Claims (4)

[Claims] 1. A magneto-optical recording method according to a magnetic field modulation method, wherein a modulated magnetic field is applied to a magneto-optical recording medium and recording is performed by irradiating a laser beam whose recording power is kept constant. The sum signal obtained from the signal obtained by extracting the reflected diffracted light from the medium through the two-division photodiode is monitored, and based on the result, it is determined whether the recording is ended or the recording is performed again in a different area. A magneto-optical recording method characterized by the above. 2. A constant threshold value is provided for the sum signal, and a section where the monitored sum signal exceeds the threshold value is defined as a defect section, and a pulse width corresponding to the section is measured by a clock. The number of defects and the defect length of the magneto-optical recording medium are obtained in this way, and whether to end the recording or to perform the recording again in a different area is determined based on the obtained result. The described magneto-optical recording method. 3. A magneto-optical recording method according to a magnetic field modulation method, wherein a modulated magnetic field is applied to a magneto-optical recording medium and recording is performed by irradiating a laser beam whose recording power is kept constant. Monitor the difference signal obtained from the signal obtained by extracting the reflected diffracted light from the medium through the two-division photodiode, and based on the result, stop recording or change the recording conditions and perform recording again. A magneto-optical recording method characterized by: 4. A recording apparatus is characterized in that a constant threshold value is set for the difference signal, and when the monitored difference signal exceeds the threshold value, recording laser power is increased to perform recording again. Item 3. The magneto-optical recording method according to Item 3.