JPH09180196A - Optical recording method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an optical recording method capable of stable overwriting, in which a low level laser beam intensity P _L is set too low to result in erasing failure and thus overwrite cannot be sufficiently performed. provide. In a method of determining a recording laser beam intensity for recording on an overwritable optical recording medium, a lower limit laser beam intensity at which a high temperature process occurs is calculated, and calculation is performed based on the value to obtain a low level laser beam intensity. Calculate the laser beam intensity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical recording method.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing method which satisfies various requirements including high density, large capacity, high access speed, and high recording / reproducing speed, a recording apparatus, a reproducing apparatus, and a recording medium used therein. Is widespread. There are many types of optical recording / reproducing methods that use principles such as thermal perforation, phase change, and magneto-optics. Among these, the method by phase change or magneto-optical method that can be erased after recording information and can record new information over and over again is a method for computer external memory and consumer audio equipment. Has been widely applied to.

Until recently, the optical recording / reproducing method has made it impossible to overwrite new information on a recorded medium without an erasing operation. However, only by modulating the intensity of the illuminating light beam according to the binary information to be recorded,
An overwritable optical recording method, an overwritable optical recording medium used therein, and an overwritable recording device used therein have been proposed.

[0004] This will be described using magneto-optical recording as an example. In addition,
This method has been applied for patents in multiple countries, of which a patent has been registered in the United States (JP 62-175948 = DE3,619,618A1 =
USP 5,239,524). Hereinafter, this invention will be referred to as "basic invention". The overwritable magneto-optical recording medium used in this magneto-optical recording / reproducing method has a perpendicular magnetic anisotropy (perpendicular magnetic layer or layers) as a storage layer.
Is composed of a plurality of magnetic layers. This magnetic layer is made of, for example, amorphous TbFe, TbFeCo, GdFe, GdFeCo, DyFe, DyFeCo, or the like.

The medium used in the basic invention is "a layer basically consisting of a magnetic thin film capable of perpendicular magnetization (hereinafter referred to as a memory layer or an M layer) and a magnetic thin film capable of perpendicular magnetization. A recording auxiliary layer (hereinafter, referred to as a recording layer or a W layer), both layers being exchange-coupled, and the magnetization direction of the M layer is not changed at room temperature. It is an overwritable multilayer magneto-optical recording medium in which only the magnetization can be directed in a predetermined direction. The W layer has a lower coercive force Hc and a higher Curie point Tc at room temperature than the M layer.

[0006] Then, information is recorded in a mark having magnetization in a direction perpendicular to the substrate (referred to as "A direction") in the M layer (and possibly also in the W layer) and a mark in the opposite direction (referred to as "reverse A direction"). Recording is performed using a mark having magnetization. In this medium, the W layer can have its magnetization direction aligned in one direction by a magnetic field means (for example, an initial auxiliary magnetic field Hini.).
Moreover, at that time, the magnetization direction of the M layer is not reversed, and further, the magnetization direction of the W layer once aligned in one direction is not reversed even when receiving the exchange coupling force from the M layer, and vice versa. The magnetization direction of the M layer is not reversed even when the exchange coupling force from the W layer aligned in one direction is received.

In the recording method of the basic invention, only the direction of magnetization of the W layer of the recording medium is aligned in one direction by the magnetic field means before recording. Then, the medium is irradiated with a laser beam pulse-modulated according to the binary information. The intensity of the laser beam is controlled to a binary value of high level P _H and low level P _L , which corresponds to the high level and low level of the pulse. This low level is higher than the reproduction level P _R that illuminates the medium during reproduction. As is already known, it is common to turn on the laser at a "very low level" even when not recording, for example to access a predetermined recording location on the medium. This very low level,
The level is the same as or close to the reproduction level P _R.

At the temperature reached by the medium when the medium is irradiated with a low-level laser beam, the magnetization direction of the W layer does not change, and the magnetization direction of the M layer is the domain wall between the M layer and the W layer. Is in the state of not existing. This is called a low temperature process, and the temperature range in which this process occurs is called the low temperature process temperature T _L. On the other hand, at a higher temperature reached by the medium when the medium is irradiated with a high-level laser beam, the direction of magnetization of the W layer follows the direction of the recording magnetic field, and M
The direction of magnetization of the layer is such that no domain wall exists between the M layer and the W layer. This is called high temperature process, the temperature region in which this process occurs as a high temperature process temperature T _H.

After the irradiation of the laser beam, the magnetic field means works so that the magnetization of the W layer, which follows the direction of the recording magnetic field by the high-level irradiation of the laser beam, follows the direction of the magnetic field means again. Therefore, if the direction of magnetization of the magnetic field means and the direction of the recording magnetic field are reversed, the already recorded M layer
New recording can be repeated (ie, overwritten). This is the principle of light modulation overwrite magneto-optical recording.

[0010] To restate the contents described above a little, by forming a recording mark by irradiating a high level laser beam and erasing the recording mark by irradiating a low level laser beam, new information is added to the old information. It can be said that it is overwritten. By the way, when actually recording on an optical disc, in order to optimize the shape of the recording mark, fine adjustment of the laser beam intensity is required according to the recording sensitivity of the disc to be recorded, the optimum recording temperature, and the ambient temperature. Becomes At present, there are some magneto-optical disk recording apparatuses on the market that perform fine adjustment of the laser beam intensity by performing test recording before actually recording information.

[0011]

However, even if the test recording is performed and the laser beam intensity is finely adjusted as described above, there are cases where it is determined that the overwriting optical recording is erroneous recording. In such a case, most of the cause was that the previous recording mark was not sufficiently erased by the laser beam intensity of the low level P _L.

This is because in the light intensity modulation overwrite recording, the low level laser beam intensity P _L is an important parameter that is involved not only in recording but also in erasing, so test recording is performed to determine the recording laser beam intensity. Even if it was obtained, it was because overwriting could not be sufficiently performed because P _L was set too low, resulting in defective erasing.

An object of the present invention is to provide an optical recording method which solves the above problems and enables stable overwrite recording.

[0014]

Means for Solving the Problems Accordingly, the present inventors have:
In order to solve this problem, when obtaining the recording laser beam intensity, obtain the lower limit of the laser beam intensity at which high temperature process starts and recording is started, and calculate the low level laser beam intensity by calculation based on that value. so,
The present invention has been completed by finding that it is possible to avoid a laser beam intensity region in which erasing failure occurs.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described with reference to FIG. Prepare a magneto-optical disk that can be overwritten by optical modulation. This magneto-optical disk is divided into a plurality of recording zones having different recording frequencies, and information on the reference value of the recording laser beam intensity in each recording zone is recorded in a predetermined area.

This magneto-optical disk is set in a recording / reproducing apparatus, and information regarding the recording laser beam intensity is read from a predetermined area. Next, recording is performed on the test recording area while changing the high level laser beam intensity P _H for each sector to form a magnetization reversal mark.
This is to determine the lower limit value of the laser beam intensity at which a high temperature process occurs and recording is started. On this occasion,
It is preferable to record a long mark that can be easily detected during reproduction. Next, the recorded area is reproduced and the lower limit of the laser beam intensity at which the mark is recorded is obtained. However, since the level of the reproduction signal when reproducing a mark recorded with a laser beam intensity near the lower limit is extremely low and it is difficult to detect it, the laser that recorded the mark where the reproduction signal above a certain level was detected was recorded. It is realistic to set the beam intensity to the lower limit.

Then, a low level laser beam intensity P _L is obtained by calculation based on the obtained lower limit value. In the simplest way, there is a method of paying attention to the small variation in the thermal diffusion coefficient between the disks and multiplying the lower limit value obtained by a predetermined coefficient to obtain P _L. Further, similarly to P _L , the high level laser beam intensity P _H can be obtained by multiplying the obtained lower limit value by a coefficient.

After the P _L is determined, the P _L is fixed and the high level laser beam intensity is changed for test recording, and the optimum high level laser beam intensity P _H is obtained from the reproduced signal. You may ask.

[0019]

As described above, according to the present invention,
When recording on an overwritable optical disk, the recording laser beam intensity can be set appropriately, so that it is possible to prevent overwriting from being performed sufficiently due to erasing failure due to setting P _L too low. Light can be realized.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an optical recording method of the present invention.

Claims (4)

[Claims] 1. In an optical recording method for determining a recording laser beam intensity for recording on an overwritable optical recording medium, a lower limit laser beam intensity at which a high temperature process occurs is calculated, and calculation is performed based on the value. An optical recording method for an overwritable optical recording medium, characterized in that an optimum low-level laser beam intensity is obtained. 2. An optical recording method for determining a recording laser beam intensity for recording on an overwritable optical recording medium, wherein a lower limit of the lower limit of the laser beam intensity at which a high temperature process occurs is obtained and based on that value. An optical recording method for an overwritable optical recording medium, characterized in that optimum high-level and low-level laser beam intensities are calculated. 3. An optical recording method for determining a recording laser beam intensity for recording on an overwritable optical recording medium, wherein a lower limit laser beam intensity at which a high temperature process occurs is calculated, and calculation is performed based on the value. A characteristic is that a low-level laser beam intensity is obtained, and further, the low-level laser beam intensity is fixed and the high-level laser beam intensity is changed to perform recording to obtain an optimum high-level laser beam intensity. Optical recording method for overwritable optical recording medium. 4. The optical recording method according to claim 1, wherein the optical recording medium is a magneto-optical recording medium having a plurality of magnetic layers exchange-coupled to each other.