JPH0922546A - Optical recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain beam intensity being optimum for overwrite recording by performing test recording again in the same area with the same beam intensity without erasing the area after performing the test recording and reproducing/ evaluating the information recorded under test. SOLUTION: Information of laser beam intensity recorded in the prescribed area of a magnetooptical disk is reproduced. Then, the central value and the intensity ratio of laser beam intensities of low level and high level are set by using the information. Next, by using a test recording pattern in which a continuous short mark and a continuous long mark are alternately repeated and changing the laser beam intensity stepwise, test recording is performed. Then, by performing overwrite operation in the same area with the same laser beam intensity, test recording is performed. Next, by reproducing the subject recorded under test and measuring the offset amount at the center of the amplitudes of reproduced signal of continuous short and long marks, the intensity in which the value becomes zero is found and the laser beam intensities of low level and high level are determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording method for recording information on an optical recording medium capable of overwrite recording.

[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. Of these, information can be recorded and then erased, and new information can be recorded again and again. Phase change and magneto-optical information are used for external memory of computers 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 the magneto-optical recording / reproducing method is composed of a multilayer magnetic layer having perpendicular magnetic anisotropy (perpendicular magnetic layer or layers) as a storage layer. This magnetic layer is, for example,
It is composed of amorphous TbFe, TbFeCo, GdFe, GdFeCo, DyFe, DyFeCo and 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. Then, the information has a mark having a magnetization in the direction perpendicular to the substrate (referred to as “A direction”) in the M layer (and possibly also the W layer) and a magnetization in the opposite direction (referred to as “reverse A direction”). Record by mark.

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 beam pulse-modulated according to the binarized information. The intensity of the beam is controlled to a binary value of high level P _H and low level P _L ,
This corresponds to the high and low levels 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 set the beam intensity to “very low level” even when no recording is performed, for example, in order to access a predetermined recording position on the medium. This very low level is also 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 beam, the direction of magnetization of the W layer does not change, and the direction of magnetization of the M layer is such that the domain wall is between the M layer and the W layer. It becomes the direction of the state that does not exist. 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 beam, the direction of magnetization of the W layer follows the direction of the recording magnetic field, and the direction of magnetization of the M layer changes between the M layer and the W layer. In the state where no domain wall exists. 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 beam, the magnetic field means works so that the magnetization of the W layer that follows the direction of the recording magnetic field by the high-level beam irradiation again follows the direction of the magnetic field means. Therefore, if the direction of the magnetization of the magnetic field means and the direction of the recording magnetic field are reversed, new recording can be repeatedly recorded (that is, overwritten) on the already recorded M layer. This is the principle of light modulation overwrite magneto-optical recording.

If the contents described above are changed to some expressions,
It can be said that new information is overwritten on old information by forming recording marks by high-level beam irradiation and erasing recording marks by low-level beam irradiation. By the way, when recording on an optical recording medium, in order to optimize the shape such as the length and thickness of the mark for the signal pulse, the optimum beam intensity should be set according to the recording sensitivity of the medium and the ambient temperature. Is required. The process of obtaining this optimum beam intensity is called test recording. At present, there are some magneto-optical disk recording apparatuses which are commercially available to obtain optimum beam intensity by performing test recording before recording information.

The test recording is performed by changing the binary beam intensity as a set while maintaining the intensity ratio of the binary beam intensities in the conventional optical recording medium (non-overwrite medium) which is not overwritten. Then, the optimum recording beam intensity is obtained by reproducing the recorded signal and evaluating the reproduced signal.

[0012]

However, in the light intensity modulation overwrite recording, the beam intensity of the low level P _L is involved not only in recording but also in erasing. Therefore, like a non-overwrite medium, while the ratio of the binary beam intensities is kept constant, the binary beam intensities are changed as a set to perform test recording and then reproducing, and the signal is evaluated. When trying to find the optimum beam intensity, it is often the case that a reasonable optimum recording beam intensity cannot be found because the test recorded data is not sufficiently erased by the laser beam intensity of the low level P _L. It was

It is an object of the present invention to solve the above problems and provide a method for obtaining the optimum beam intensity for overwrite recording.

[0014]

In order to solve the above-mentioned problems, the present inventors can complete the old test record data completely by overwriting the test record data again without erasing the test record data area. The present invention has been completed by finding that erased data and a reasonable optimum recording beam intensity can be obtained.

Therefore, the first aspect of the present invention is, "In an optical recording method for recording information on an optical recording medium capable of overwrite recording by modulating beam intensity, test recording is performed in a test recording area of the optical recording medium. Then, without erasing the test recording area, test recording is performed again in the test recording area with the same beam intensity as the test recording, and then the information recorded in the test recording is reproduced and evaluated to obtain the optimum recording beam intensity. An optical recording method characterized by the following is provided. Secondly, the "optical recording medium is a magneto-optical recording medium comprising two or more recording layers exchange-coupled to each other. The third aspect of the present invention is to provide "the optical recording method according to claim 1," and thirdly, "the optical recording method according to claim 1, wherein the test recording area is erased before the test recording."

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0017]

The present invention will be described with reference to FIG. FIG.
Shows a flow chart of the optical recording method of the present invention.
First, a magneto-optical disk that can be overwritten by optical modulation is prepared. This magneto-optical disc is divided into a plurality of recording zones having different recording frequencies, and information about the recording laser beam intensity at 25 ° C. in the plurality of recording zones is recorded in a predetermined area.

This magneto-optical disk is set in a recording / reproducing apparatus having an optical recording function by the optical recording method of the present invention,
Information about the recording laser beam intensity recorded in a predetermined area is reproduced. The center value and intensity ratio of the low-level and high-level laser beam intensities are set by these information. Next, using a test recording pattern in which continuous short marks and continuous long marks are alternately repeated, low-level and high-level laser beam intensities are set in stages in multiple sectors without changing the intensity ratio. Change the test record.

Next, without erasing the test recording area, the test recording is performed again in the same area with the same laser beam intensity so as to overlap (overwrite). next,
The test recorded signal is reproduced, and the difference (offset amount) between the amplitude center of the reproduction signal of the continuous short mark and the amplitude center of the reproduction signal of the continuous long mark is measured. The laser beam intensity at which this value becomes zero is obtained as shown in FIG. 2, and the low-level and high-level laser beam intensities are determined.

The combination of recording laser beam intensities is determined by the above procedure.

[0021]

As described above, according to the present invention,
When recording on an optical disc that can be overwritten with light intensity modulation, the ratio of the low-level beam intensity and the high-level beam intensity can be set optimally, so the low-level setting will not be too low during overwrite recording, resulting in no erasing failure A stable overwrite optical recording method can be provided.

[Brief description of drawings]

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

FIG. 2 is a graph showing a difference between a high level beam intensity P _H and an offset amount of test recording used in an example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Kurita 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (3)

[Claims] 1. An optical recording method for recording information on an optical recording medium capable of overwrite recording by modulating beam intensity, wherein test recording is performed on a test recording area of the optical recording medium, and then the test recording area is recorded. Without erasing
An optical recording method, wherein test recording is performed again in the test recording area with the same beam intensity as that of the test recording, and thereafter, information recorded in the test recording is reproduced and evaluated to obtain an optimum recording beam intensity. 2. The optical recording method according to claim 1, wherein the optical recording medium is a magneto-optical recording medium having two or more recording layers exchange-coupled to each other. 3. The optical recording method according to claim 1, wherein the test recording area is erased before the test recording.