JPS63152051A - Method for recording magneto-optical disk - Google Patents

Abstract

PURPOSE:To prevent in advance the generation of an error by the defect of a recording medium by detecting the defective position on a track from the variation in the reflection factor of a laser beam in case of performing the erasing of an information and performing the recording by skipping the defective position in case of recording an information. CONSTITUTION:The reflection light emitted from the laser beam scanning along a guide groove is converted into an electric signal at a head 1, bisected after being amplified at a reproducing system 2 and one part is processed as a magneto-optical signal. One part of the signal for measuring reflection factor is compared with a normal reflection light level by a comparator 3 and the signals having large and small reflection factors are detected. This signal generating position is taken as an error position and the number of pulses oscillated from an inner part clock 4 is counted and recorded into a memory 5. On the other hand, the data to be recorded is projected as an optical signal from the head 1 through a laser driving circuit 7, but in this case, the information of the defective position is inputted from the memory 5 into a processor 6 to skip this defective position. The error generation by the defect of a recording medium is thus prevented.

Description

[Detailed Description of the Invention] C Summary] As a method for reducing errors that occur based on defects existing in a track on which information is to be recorded, a laser beam is scanned onto a track on which information is to be recorded to remove previously recorded information. A method for recording a magneto-optical disk, in which a defect position on the track is detected from a change in the reflectance of the laser beam when erasing data, and the defect position is skipped when recording information.

[Industrial application field]

The present invention relates to an optical disc recording method that reduces error rate.

A magneto-optical disk is a memory that uses laser light to record high-density information. Like an optical disk, it has a large storage capacity, can record and read without contact, and is unaffected by dust. It has the following characteristics.

Here, an optical disk is a read-only memory that uses a low-melting point metal as a recording medium and records and reproduces information using the presence or absence of holes (pits).
), whereas magneto-optical disks are being developed as rewritable memories (eraserble memories).

[Conventional technology]

Magneto-optical disks are made of polymethyl methacrylate (abbreviated as PM).
A rare earth-transition metal based amorphous alloy is deposited by vacuum evaporation or sputtering on a transparent substrate made of a plastic substrate such as MA) or polycarbonate (abbreviated as PC) or a glass substrate and equipped with a guide groove (pre-group). A recording medium made of a perpendicularly magnetized film is produced by forming a film using a method such as a perpendicular magnetization method, and a protective film is provided thereon to produce a disk substrate.

To record information on a magneto-optical disk having such a structure, a laser beam focused by a lens is irradiated from the side of the transparent substrate while a magnetic field is applied perpendicularly, and the temperature of the irradiated part of the perpendicularly magnetized film is increased. This is done by utilizing the fact that the temperature rises to near the Curie temperature and the magnetization reverses in the direction of the magnetic field.

Information is also erased by heating the material by irradiating it with laser light without applying a magnetic field in the direction opposite to the direction of magnetization at the recording position, thereby reversing the magnetization to its original direction.

Here, information is recorded on a recording medium with guide grooves that are densely arranged concentrically with a width of 0.6 to 0.7 μm, a depth of 0.07 μm, and a pinch of about 1.6 μm. Approximately 1
This is done by intermittent irradiation with a μm laser beam, but 1
Since the focal point area is as small as about 1 μm2, even a slight defect in the recording medium on the guide groove is likely to cause an error during information recording.

Such fine defects occur in the following cases.

■ When forming guide grooves.

■ When forming a recording medium.

■ Due to changes over time after film formation.

That is, the defect (2) occurs during molding when a plastic substrate is used, and during etching using photolithography when a glass substrate is used.

Furthermore, the defect (2) occurs when a film is formed on a recording medium made of a rare earth-transition metal by a method such as vacuum evaporation or sputtering.

Furthermore, the defect (2) occurs due to oxidation after the film is formed, since the rare earth elements such as Tb and Gd that form the recording medium are metals that are extremely easily oxidized.

For this reason, the defect content, or error rate, of current magneto-optical disks is 10-5.
degree and large.

Conventionally, error correction codes (E
Correcting Code (abbreviation: E): EC.

That is, error correction was performed by performing a parity check that added redundant bits.

However, when the error rate is as high as about 10 -5 as in the case of this magneto-optical disk, the redundant bits for ECC become large, reducing efficiency and making it impossible to use them effectively.

For the above reasons, there has been a need for effective measures to improve the error rate.

[Problem that the invention seeks to solve]

As described above, the error rate of magneto-optical disks is currently as high as about 10-5, and therefore there has been a demand for an error rate improvement method that can replace ECC.

[Means for solving problems]

The above problem arises when a laser beam is scanned onto a trunk where information is recorded to erase previously recorded information. This problem can be solved by a magneto-optical disk recording method that skips the defective position during recording.

[Effect]

The inventors have discovered that there is a close relationship between errors caused by defects in recording media and changes in reflectance.

That is, as a result of examining the reflectance of 116 defects, it was detected that 76% of them had an abnormal reflectance compared to a normal recording medium.

That is, the reflectance is high or low.

Therefore, in order to obtain a servo signal on a magneto-optical disk, the reflected light from the guide groove is received, and at this time, the reflectance is checked and the position where the reflectance changes from a predetermined value is determined. This is regarded as a defect, and when recording information, the error rate is reduced by skipping, for example, one byte at the preceding and following recording positions, including this location.

〔Example〕

The figure shows a block diagram for implementing the present invention.
The reflected light from the laser beam scanning along the guide groove is converted into an electrical signal by the head 1, amplified by the reproducing system 2, and then divided into two parts, one of which is processed as a magneto-optical signal in the conventional manner.

Here, one is for measuring reflectance, and the signal is compared with a normal reflected light level by a comparator 3, and a signal with a large reflectance and a signal with a small reflectance are detected.

Since such a signal generation position is an error position, this position is recorded in the memory 5 by counting the number of pulses oscillated from the internal clock 4.

On the other hand, the data to be recorded is input to the processor 6, and is emitted as an optical signal from the head 1 through the laser drive circuit 7. At this time, the processor 6 receives information about the defect position from the memory 5, and this defect position is skipped. do.

By adopting such a method, it is possible to suppress the occurrence of errors due to defects in the recording medium, even for a magneto-optical disk with a high error rate of about 104.

〔Effect of the invention〕

According to the present invention, it is possible to prevent errors caused by defects in recording media in advance, thereby simplifying ECC,
It is possible to increase the usage efficiency of magneto-optical disks.

[Brief explanation of the drawing]

The figure is a recording circuit diagram of a magneto-optical disk embodying the present invention.

Claims (1)

[Claims] In a magneto-optical disk device for recording and reproducing information, when a laser beam is scanned onto a track on which information is recorded and previously recorded information is erased, the reflection of the laser beam is A method for recording a magneto-optical disk, characterized in that a defect position on the track is detected from a rate change, and when information is recorded, the defect position is skipped.