JPH08273233A - Optical recording method - Google Patents

Abstract

PURPOSE: To provide an overwrite optical recording method high in recording data transfer speed without making a retry whenever erroneous recording is discriminated by verification. CONSTITUTION: Data overwrite-recorded on a overwritable optical recording medium is verified. When a data error is more than a prescribed level, this data is overwrite-recorded again by making laser beam intensity at a low level higher than the recorded time without erasing the previous data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method for an overwritable optical recording medium.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing method satisfying various requirements including high density, large capacity, high access speed, and high recording and reproducing speed, recording apparatus, reproducing apparatus and recording medium used therefor. Is widespread. There are many types of optical recording / reproducing methods using the principles such as hole formation by heat, phase change, and magneto-optical properties. 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, in the optical recording / reproducing method, it has been impossible to overwrite the new recorded information without erasing the recorded medium. 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.

This will be described by taking 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 is referred to as a "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 defined as "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. And 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.

Information is recorded in the M layer (and also in the W layer as the case may be) in a direction having a magnetization in a direction ("A direction") perpendicular to the substrate and in a direction opposite to that ("reverse A direction"). It is recorded by 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 binarized 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 known, it is common, even when not recording, to turn on the laser at a "very low level", for example to access a given recording location on the medium. This very low level also
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 magnetization direction of the W layer follows the direction of the recording magnetic field, and M
The magnetization direction of the layer is in a state in which 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 repeatedly recorded (that is, overwritten). This is the principle of optical 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. When actually recording on an optical recording medium, the optical head is moved to a region to be recorded, and the beam is intensity-modulated according to the binarized information and irradiated on the medium.
However, at this time, due to noise generated, environmental temperature, servo performance of the optical head, defective erasure of information recorded before that, recording may not be performed properly, that is, incorrect information may be recorded. is there. Therefore, up to now, erroneous recording has been prevented by performing verification, which is an operation of confirming whether or not the information was properly recorded, by immediately reproducing the recorded information after recording the information.

[0011]

However, in the conventional optical recording, when it is determined by the verification that the recording is erroneous, the data area in which the information is recorded is once erased, and then the recording (retry) is performed again. Therefore, there is a problem that the recording data transfer speed becomes slow. The present invention solves such a problem and provides an overwrite optical recording method having a high recording data transfer rate.

[0012]

In order to solve the above problems, the present inventor has found that in the overwritable optical recording, when it is determined that the recording is erroneous, the previous recording mark has a low level P.
Most of the reason is that it is not erased sufficiently by the laser beam intensity of _L. Therefore, if the low level laser beam intensity is increased and overwrite recording is performed again without erasing the entire data area. Then, they found that old information is erased, and completed the present invention.

Therefore, according to the first aspect of the present invention, when verifying the data overwritten on an overwritable optical recording medium, the data is not erased if the data error is above a predetermined level. The optical recording method is characterized in that a low level laser beam intensity is made higher than that at the time of recording to perform overwrite recording again. Secondly, "the optical recording medium is composed of two layers exchange-coupled to each other. An optical recording method according to claim 1, which is a magneto-optical recording medium including the above-mentioned magnetic layer, and thirdly, "low-level laser beam intensity at the time of previous recording when re-recording is performed. The optical recording method according to claim 1, which is 2 to 20% higher than the above.

[0014]

The erasure failure in the optical modulation overwrite recording is that old information before recording is recorded in a biased manner from the center of the track, or is recorded larger than a predetermined mark width, and overwrite recording is performed. The beam spot at that time is deviated from the central portion of the track, etc., so that it is mostly due to the presence of unerased marks on the peripheral portion of the track.

Therefore, when the low-level laser beam intensity is made higher than that when old information was recorded and recording is performed again, the peripheral portion of the track reaches the low temperature process temperature and the unerased mark is erased. FIG. 2 is a schematic diagram showing how marks are erased by re-recording. Indicates that old information is recorded, and here, recording is performed with a slight deviation from the track center.
Indicates the case where the overwrite recording is performed once on the recording medium in the state of. It indicates that old information marks are left around the area that was erased by the low level laser beam intensity. Indicates the case where recording was performed again with the low level laser beam intensity higher than that of and. It can be seen that the old information is almost completely erased by setting the low level laser beam intensity high.

Since the low-level laser beam intensity affects the length of the mark, its size is limited. 2% to 20% compared to when old information was recorded
Higher is desirable and 5% to 15% higher is even more desirable. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

[0017]

Example A magneto-optical disk having a diameter of 130 mm and capable of overwriting recording by optical modulation is prepared. First, after recording a single frequency signal of 5 MHz on this disc, this signal is reproduced to confirm the level of the unerased portion of the signal of 5 MHz.

Next, a low-level laser beam intensity of 2 MHz is applied to the 5 MHz signal with a single frequency signal of 2 MHz.
After overwriting the recording by increasing various values of 20%, the signal at 5 MHz is measured again, and it is confirmed that the signal is substantially erased. Repeat this procedure to confirm that the 5MHz signal is surely erased.

[0019]

As described above, according to the present invention,
Since the retry is not performed each time it is determined that the recording is erroneous in the verification, it is possible to provide the overwrite optical recording method in which the recording data transfer speed is high.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a state in which old information is erased by overwriting recording new information.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 20/18 520 9558-5D G11B 20/18 520C 552 9558-5D 552B 572 9558-5D 572D (72 ) Inventor Masafumi Horikawa 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (3)

[Claims] 1. A low-level laser beam without erasing the data when the data recorded in the overwritable optical recording medium is overwritten and the data error is above a predetermined level. An optical recording method, characterized in that the intensity is made higher than that at the time of recording, and overwrite recording is performed again. 2. The optical recording method according to claim 1, wherein the optical recording medium is a magneto-optical recording medium including two or more magnetic layers exchange-coupled to each other. 3. The optical recording method according to claim 1, wherein the low-level laser beam intensity at the time of re-recording is increased by 2 to 20% as compared with the previous recording.