JP2000076656A - Optical recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress recording sensitivity fluctuation and thermal interference between recording bits, to improve matching between an optical recorder and an optical disk and to improve recording capacity by performing trial write and reproducing the trail written data before starting regular recording/ reproducing operation for a disk. SOLUTION: The trial written data from a trial writer 103 are outputted to an encoder 104 by a trial write command signal. A symbolic code string from the encoder 104 is compared with a regenerative code string from a discriminator 115 by a comparison discriminator 116, and when the regenerative code string becomes smaller than the symbolic code string to a certain extent, a trial write end signal is outputted. An input switcher 112 switches an output of a waveform equalizer 111 to a shaper 113, and the regular recording/ reproducing operation is started. Even after the regular recording operation is started, a difference between the symbolic code string and the regenerative code string exists within the allowable range is confirmed by the comparison discriminator 116, and when unallowable, the trial write is started, and when the trial write end signal is outputted, the regular recording operation is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magneto-optical recording in which recording, reproduction, or erasing is performed using a laser beam.
The present invention relates to a recording method suitable for controlling a recording magnetic domain shape with high accuracy in ultra-high density magneto-optical recording.

[0002]

2. Description of the Related Art With the recent development of a highly information-oriented society, there is an increasing need for a high-density and large-capacity file memory. Optical recording has attracted attention as a memory that responds to this. Recently, rewritable magneto-optical recording has been put to practical use. Recently, research and development have been promoted with the aim of further improving the performance of magneto-optical recording. At the center of this is the improvement in recording capacity. In order to improve the recording density, techniques for reducing the track pitch or reducing the bit pitch have been considered. by the way,
In the case of magneto-optical recording, especially when the bit pitch is reduced, thermal interference between bits may occur. In this case, particularly, when performing high-density recording by narrowing the mark length recording or bit pitch, it causes edge shift and jitter, and may be fatal when performing high-density recording using this method. . On the other hand, JP-A-3-22223 can be cited as a known example in which edge shift is suppressed during recording. In this example, the recording code sequence of the recording mark is pulsed to form a series of pulse sequences corresponding to the length of the recording code sequence, controlled according to the pulse sequence length, the pulse sequence is divided into three parts, and each pulse In which the recording is performed by changing the pulse width.

[0003]

In the above-mentioned prior art, high-density recording is realized when the recording sensitivity of the recording medium fluctuates due to fluctuations in the film thickness of the recording medium or fluctuations in the use environment temperature, or by reducing the bit pitch. In some cases, thermal interference between recording bits generated in such a case is not sufficiently considered, and high-precision magnetic domain shape control may not be performed.
As a result, there has been a limit to the increase in density.

An object of the present invention is to provide a method for suppressing fluctuations in recording sensitivity to a recording medium and thermal interference between recording bits, and to provide a high-density optical recording / reproducing apparatus.

A second object of the present invention is to improve the matching between an optical recording device and an optical disk.

A third object of the present invention is to improve the recording capacity of a recording / reproducing apparatus.

[0007]

In order to realize the above-mentioned prior art, at least in magneto-optical recording in which recording, reproduction, or erasing is performed using a laser beam, when recording information on a disk, a plurality of power levels are required. When performing recording using a recording waveform consisting of, after a recording instruction is issued,
This is achieved by performing recording after passing through a preheating mode of the recording film for a fixed time. In the magneto-optical recording, when information is recorded on a disk, a recording waveform composed of a plurality of power levels used includes at least four power levels, a first level is a reproduction level, and a second level is preheating. Level, the third level and the fourth level are recording levels, and each level needs to be a power level set in consideration of heat flow in the recording medium.

At the preheating level, it is necessary to control the laser power so that the temperature of the recording film always becomes constant without depending on the ambient temperature. At this preheating level, a recording pulse is emitted after the temperature of the recording film has become constant after a certain period of time. Otherwise, the apparent environmental temperature and laser power seem to fluctuate, and recording magnetic domains of the same shape were not always obtained under all conditions.

By controlling the preheating power, the temperature of the recording film can be controlled to a constant value without depending on the ambient temperature. For that purpose, it is necessary to irradiate the recording film with laser light for a certain time. In the case where the recording film is irradiated with the preheating power, the irradiation time is governed by the recording timing rather than the time at which the temperature becomes constant. Therefore, when a recording command is issued and the preheating mode is entered, it is necessary to make the temperature of the recording film constant within a predetermined time. Therefore, in order to keep the temperature of the recording film constant at the preheating level, after entering a preheating mode and passing a high level for a certain period of time, the preheating level is set, and more preferably, the high level is 1.1 times the preheating level. The value may be set to 1.3 times or less. Preferably, the pulse width is synchronized with the write clock, and the level and the pulse width are changed according to the structure of the disk and the material used. this is,
The idea is to make the device easier.

[0010] When a preset preheating level is entered after a high level for a certain period of time after entering the preheating mode, it is preferable to change the level in the high level portion for a certain period according to the environmental temperature and the difference in disks. This is because the temperature of the recording film varies depending on the environment in which the recording / reproducing apparatus is used, fluctuations in the laser power, and differences in discs. Here, at the preheating level, the power must not be recorded on the disc.

When recording on a magneto-optical disk, the recording film is preheated to a constant temperature by a preheating power, thereby suppressing edge shift and jitter during information recording and combining with multi-pulse. Thereby, the interference between bits can be made constant regardless of the recording pattern.

[0012]

FIG. 1 is a schematic sectional view of a magneto-optical disk used in an embodiment of the present invention. A silicon nitride film 2 was formed on a glass or plastic substrate 1 having an uneven guide groove by a sputtering method. The thickness is 85 nm. Next, a TbFeCoNb film 3 was formed by a sputtering method. The thickness is 25 nm. Then, a silicon nitride film 4 was formed by a sputtering method. The thickness is 15 nm. Finally, an Al ₉₅ Ti ₅ film 5 was formed by a sputtering method. The thickness is 50 nm. This structure is an example, and there is another structure that can obtain a large magneto-optical Kerr rotation angle in consideration of optical interference. Finally, the entire recording medium was covered with the ultraviolet curing resin 6.

FIG. 2 is a block diagram showing the configuration of the magneto-optical disk drive used.

The feature of this drive is that it has a trial writing function. Test recording was performed at fixed time intervals when the disk drive was started, when the disk was loaded, or during operation of the disk drive.

First, the wavelength of the laser beam used for recording is 78
0 nm. The recording / reproducing apparatus includes a recording medium 101 for storing information and an optical head 1 for realizing recording / reproduction.
02 and a processing system for converting a reproduction signal obtained from the optical head 102 into information. The optical head 102 narrows the light emitted from the laser 108 onto the recording medium 101. At the time of recording information, an input data bit sequence (information) is input to the encoder 104, input to the encoder 104, and a recording code sequence output from the encoder 104 is recorded by the recording waveform generator 1.
The recording waveform obtained by the recording waveform generator 105 is input to the APC 106, and the light intensity corresponding to the recording code string is output from the laser 108.

At the time of reproducing information, the light reflected from the recording medium 101 is guided to the light receiver 109 and converted into an electric signal. The signal is input to the reproduction amplifier 110 and output to the waveform equalizer 111 and the input switch 112. The input switch 112 is converted into a pulse signal indicating the presence or absence of a reproduced signal from either the reproducing amplifier 110 or the waveform equalizer 111 in accordance with the test writing command signal. The pulse signal is sent to the discriminator 1
15 and the PLL 114. The synchronization signal (signal synchronized with the basic period of the pulse signal) output from the PLL 114 is input to the discriminator 115.

The discriminator 115 generates a detection code sequence from the pulse signal and the synchronization signal, and outputs a data pit sequence (information) by the decoder 117. Further, the detection code string of the discriminator 115 is output to the comparison discriminator 116. Comparison discriminator 1
Reference numeral 16 denotes a trial writer 1 operated by a trial write command signal.
03 is output to the encoder 104, and the input switch 112 that operates according to the test writing command signal switches the output of the reproduction amplifier 110 to output to the shaper 113. The symbol code string is compared with the reproduced code string from the discriminator 115, and the difference between the reproduced code string and the symbol code string is reduced to some extent, and a test write end signal is output within an allowable range.

After the test write end signal is output, the input switch 112 changes the output of the waveform equalizer 111 to the shaper 11.
3, and the normal recording / reproducing operation is started. Even after the normal recording operation is started, the comparison discriminator 1
At 16, it is confirmed that the difference between the reproduced code string from the recorded code string is within an allowable range. If the difference is not acceptable, the above-described test write operation is started. Continue normal recording operation. When the comparison discriminator 116 checks the difference between the reproduced code string and the recorded code string, the output of the input switch 112 is
If the operation is performed to output the signal of the reproduction amplifier 110, the detection can be performed with higher accuracy.

In these operations, the input switch 1
A similar operation can be realized without using the block 12. In order for the comparison discriminator 116 to accurately detect the difference between the reproduced code string from the recorded code string, it is better not to use the waveform equalizer 111.

First, FIG. 3 shows the temperature change of the recording film when the preheating power is applied to the recording film.

From this figure, the time required for the temperature of the recording film to become constant is the position of the disk: r = 30 mm, the rotation speed of the disk is 3000 rpm, and the wavelength of the laser is 780 n.
m indicates that at least 100 ns or more is required.

On the other hand, the temperature change of the recording film when the laser waveform having the shape shown in FIG. 4 is applied is shown in the lower part of FIG. The temperature change was determined by computer simulation.
From this figure, it was possible to reduce the time to 70 ns before the temperature of the recording film became constant. When the temperature of the disk and the driving device thereof was changed, the temperature of the recording film also changed accordingly. Therefore, by changing the power according to the environmental temperature, the temperature of the recording film is controlled to be always constant.

Recording / reproducing was performed on a disk using the recording / reproducing apparatus and the recording medium described above. The disk rotation speed of the used apparatus was 3000 rpm, and the laser wavelength was 78.
0 nm, and (1,7) RLL was used as a modulation method. Here, recording was performed so that the recording density was equal at any position on the disk. Then, the recording waveform used for recording on this disk was the same as that shown in FIG. The laser power used was read level: Pr = 1.5 mW, preheat level: Pa
s = 3.5 mW, first recording level: Pw1 = 5.8 mW,
Then, the second recording level was set to Pw2 = 6.1 mW. Here, the value of each power varies depending on the laminated structure of the disk and the material used.

However, the greatest effect of suppressing the jitter or edge shift caused by thermal interference between recording domains to a certain value or less is the laminated structure of the disk except for the material used. When this is evaluated using the parameters of the recording / reproducing apparatus, Pw1 / Pas, Pw2 / Pa
It is necessary that the ratio of s, Pw1 / Pw2 be within a certain range. When this value is measured for many disks, 1.5 <Pw1 / Pas <1.7, 1.6 <Pw2
For a disc in the range of /Pas<1.8, 0.9 <Pw1 / Pw2 <1.1, the length and width of the formed recording domain could be precisely controlled when performing mark length recording. The control accuracy at that time was such that the domain length (in the track direction of the disk) was ± 0.02 μm or less, and the domain length direction (in the radial direction of the disk) was ± 0.05 μm or less. This accuracy is a value obtained from both the measurement of jitter and edge shift at the time of reproduction and the measurement by MFM (scanning magnetic force microscope).

Then, recording / reproduction was attempted on the innermost zone of the 5.25 ″ disk. First, room temperature (20 ° C.)
In (2), a random pattern was recorded using the (1,7) RLL method at the previously set power. FIG. 6 shows the jitter distribution at that time. This is a result measured without applying a PLL. According to this, the ratio to the window width was 39%.

When the edge shift amount was measured,
It could be suppressed to ± 2 ns or less.

[0027]

According to the present invention, by providing a preheating region for a certain period, a recording magnetic domain having the same shape and size can always be formed with high precision without depending on the environmental temperature or the like. It is important for the recording magnetic domain shape control to keep the recording film temperature constant by the preheating power which plays an important role in recording. Moreover, it is necessary to stabilize the temperature of the recording film in a short time from the recording timing. Even in that case,
The stabilization method using the recording waveform according to the present invention is effective, and high-density magneto-optical recording can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magneto-optical disk used in an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a magneto-optical disk drive using the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a temperature change of the recording film when a preheating power is applied to the recording film.

FIG. 4 is an explanatory diagram showing a change in temperature of the recording film when the recording film is irradiated with a preheating power whose waveform is controlled.

FIG. 5 is a waveform chart used for recording in the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a jitter distribution when a random pattern is recorded.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk substrate, 2 ... Silicon nitride film, 3 ... TbFe
CoNb film, 4 ... silicon nitride film, 5 ... Al ₉₅ Ti ₅ ,
6 ... A UV-curable resin layer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuyoshi Toda 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Hiroshi Ide 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Takeshi Maeda 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Hitachi Central Research Laboratory, Inc. (72) Inventor Fumio Kugiya 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Hitachi Central Research Laboratory Co., Ltd.

Claims (2)

[Claims] In optical recording in which recording, reproduction, or erasure is performed using a laser beam, test writing and reproduction of the test-written data are performed before starting a normal recording / reproducing operation on a disc. Characteristic optical recording / reproducing method. 2. A means for generating test writing data, means for generating and outputting a recording code string of the generated test writing data, a laser driver for controlling laser irradiation according to the recording code string, Means for reading information written in accordance with the test write data from the recording medium to obtain a reproduction code string from the reproduction signal, and comparing the reproduction code string with the recording code string, Means for outputting a test write end signal for starting a normal recording / reproducing operation if the difference from the code string is within a predetermined allowable range.