JPH06208740A - Magneto-optical recording method - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical disc drive having ultrahigh recording density. CONSTITUTION:A recording waveform has four power levels wherein the first level, i.e., a read out level (Pr), is 1.5mW. Second level, i.e., an intermediate level(Pas), depends on the structure of disc. Third and fourth levels, i.e., recording levels(Pel and Pw2), have a plurality of recording levels, respectively, which also depend on the structure of the disc. Laser power is set such that the ratio of the intermediate level to the first recording level(high power level) is 1.50-1.80 whereas the ratio of the intermediate level to the second recording level(low power level) is 1.50-1.80. Furthermore, the ratio of the first recording level to the second recording level is set in the range of 1.0-0.90.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording for recording, reproducing or erasing by using at least a laser beam and an externally applied magnetic field, and more particularly to a recording method of a suitable magneto-optical recording for high density recording. .

[0002]

2. Description of the Related Art With the progress of the advanced information society in recent years, there is an increasing need for a high-density and large-capacity file memory. Optical recording is attracting attention as a memory to meet this demand. Recently, rewritable magneto-optical disks have been commercialized. Further, more recently, research and development have been promoted with the aim of further improving disk performance. One of them is the improvement of recording density. The current product has a storage capacity of 5.25
It is inch-sized and 320MB on each side. As a target of recording capacity, research and development are being carried out with the aim of at least triple this capacity or more. The problem in that case was to find a method for recording a minute recording magnetic domain stably and without interference of the recording magnetic domain. In addition, if the mark length recording method is used, edge shift must be suppressed. Therefore, it is necessary to control the recording waveform shape to realize a high-precision magnetic domain shape control technique. As a publicly known example that realizes this, there is JP-A-3-22223. In this conventional example, the code sequence of the recording mark is pulsed to form a series of pulse sequences corresponding to the length of the record code sequence, and the length and amplitude of the pulse sequence are determined according to the length of the antiphase of the symbol code sequence. It was controlled by dividing the pulse train into three parts and changing the pulse width of each pulse for recording.

[0003]

[Problems to be Solved by the Invention]
It was not always possible to obtain sufficient precision in controlling the shape of the recording magnetic domain, which is required to realize the double-density recording capacity. As a result, it may be observed as an edge shift, which may cause an error, which may be a major obstacle in realizing ultra-high density recording using the mark length recording method. Therefore, there has been a need for a method of obtaining the desired width and length of the recording magnetic domain.

Therefore, an object of the present invention is to provide a magneto-optical disk drive device having an ultrahigh recording density by providing a method for controlling the recording magnetic domain shape with high accuracy.

[0005]

In order to achieve the above object, in a magneto-optical recording for recording, reproducing or erasing using at least a laser beam and an externally applied magnetic field, a laser is used in a recording pulse waveform used for recording. There are at least four types of power levels, and recording or erasing is performed by controlling the laser power according to the operating environment temperature and the structure of the disk used. Furthermore, at least the reading power level is at least the laser power level used for recording. The recording medium may have an intermediate level and a plurality of recording levels, and the recording may be performed by setting the ratio between the intermediate level and the recording level within a certain range depending on the operating environment temperature and the structure of the disc used. Here, in the recording pulse waveform used for recording, the ratio of the laser power to the first recording level (higher power level) of the intermediate level and the plurality of recording levels is set to be larger than 1.50 and smaller than 1.80. In addition, the ratio between the intermediate level and the second recording level (low power level) of the multiple recording levels
Set larger than 1.50 and smaller than 1.80, and
The ratio between the first recording level and the second recording level may be set smaller than 1.0 and larger than 0.90. As the recording method, a so-called mark length recording method, in which information is recorded in the formed edge portion, may be used to record information on the disc. To record information on a disc,
It has a waveform in which minute pulses are generated at fixed intervals, the level of the leading pulse is set to the first recording level, and the level of subsequent pulses is set to the second recording level. The read level may be set at an intermediate level between the pulse and one information code and immediately after the end of the recording pulse of one information code with a certain interval. By the way, in recording information on a disc, in a waveform in which minute pulses are generated at fixed intervals, the pulse width or gap used for recording is set to an integral multiple or a fraction of the write clock of the device. By using the signal, a highly accurate signal can be obtained by a simple method for manufacturing the device. as a result,
Since the device cost is reduced and the control accuracy of the width and length of the recording magnetic domain is improved, mark length recording can be realized. In the recording waveform having such a shape, the pulse width of the head pulse is different from the pulse width of the head pulse, and more advantageously, it is preferable to set the pulse width of the head pulse wider than the width of the head pulse. by the way,
It goes without saying that a pulse width that is an integral multiple or a fraction of the write clock of the disk drive is used as the reference clock. When recording information on a disc, it is composed of minute pulses, and the intervals between the pulses are generated equally, and more advantageously, the intervals between the pulses are an integral multiple or an integer of the write clock of the disk drive device. It goes without saying that it is preferable to set the value to a fraction. By the way, in recording information on a disc, the shortest recording magnetic domain in the modulation method used to record information by giving information to the formed edge is one of the aggregates of minute pulses as described above. It is preferable to form one pulse instead of a plurality of pulses. Therefore, at least one of the pulse width and the laser power may be controlled. In the case of a pattern longer than this, the second recording level synchronized with the write clock is held for a certain period after passing through the intermediate level for a certain period synchronized with the write clock, depending on the length corresponding to the code to be recorded. Then, the pulse of these two combinations may be added to the first pulse. As a result, the magnetic domain width and the magnetic domain length could be controlled with high accuracy for any pattern. In particular, the magnetic domain width is the same for both the long pattern and the short pattern, which has a great effect on suppressing the edge shift in recording the mark length.

By the way, the magneto-optical disk device is not always in the same use environment, but is usually changing. In this case, for example, when the air temperature fluctuates in the environment of use, the width of the magnetic domain formed increases as the temperature rises, and conversely, when the temperature decreases, the width of the magnetic domain formed also decreases. Even so, it is observed as an edge shift, which causes an error. Therefore, when recording information on a disc, test recording for detecting fluctuations in recording conditions is performed at regular time intervals or when the disc is loaded.
Alternatively, when the optimum recording condition is found from the result before the execution of the recording command and the recording is performed by using the result, the laser power is changed to change the recording laser power and set the recording condition. As a result, recording or erasing is performed by controlling the laser power according to the operating environment temperature and the structure of the disk used, and more advantageously, at least the read level and the intermediate level as the laser power level used for recording. Level, there are multiple recording levels, and the ratio between the intermediate level and the recording level is set within a certain range depending on the operating environment temperature and the structure of the disc to be used. , The power of the laser is the first recording level (higher power) of the intermediate level and the plurality of recording levels. Level) is greater than 1.50,
In addition to setting it lower than 1.80, the ratio of the second recording level (low power level) of the intermediate level and the plurality of recording levels is set to higher than 1.50 and lower than 1.80, and further to the first recording level. The ratio to the second recording level may be set smaller than 1.0 and larger than 0.90.

[0007]

By controlling the ratio of each laser power within a certain range by the above method, the heat flow in the recording medium can be made constant without depending on the structure of the recording medium.
Here, the ratio of laser power represents the gradient of heat flow in the recording medium, and even if the use environment changes, the heat flow can always maintain the same state as long as the ratio is kept within a certain range. Therefore, it can be said that the recording method is suitable for mark length recording because magnetic domains having the same shape are always obtained regardless of the use environment or the structure of the medium. As a result, ultra-high density magneto-optical recording was realized.

[0008]

The details of the present invention will be described in detail with reference to an embodiment.

(Example 1) Recording was performed by the recording control method of the present invention using disks having various structures. First, a schematic diagram of the magneto-optical disk device used is shown in FIG. Using this apparatus, recording was performed on the disc using the recording waveform shown in FIG. The recording waveform used has four power levels, 1
The second level is the read level (Pr), which is 1.5 mW. The second level is the intermediate level (Pas), and its power value is determined by the structure of the disc. The third and fourth values are recording levels (Pw1 and Pw2) and have a plurality of recording levels. Each value is different depending on the structure of the disc as well as the intermediate level. Table 1 summarizes the results of obtaining each value.

[0010]

[Table 1]

From this table, Pw1 / Pas, Pw2 / Pas, and Pw1 / Ps of the present invention can be applied to five types of media having different disk structures.
Looking at each ratio of w2, the values are almost the same, Pw1 / Pas and Pw2 /
Both Pas are in the range of 1.50 to 1.80. Also, Pw
The 1 / Pw2 ratio is between 0.9 and 1.0. Each power level was set in these ranges, and a random pattern was recorded on the disc. Here, the modulation method used is (1,7) RLL.
It is a method. Set the recording power etc. to the above power ratio,
A record was made. When the amount of edge shift was measured, the value could be suppressed to 2 ns or less. Also, when the jitter distribution is calculated, it is 40% or less with respect to the window ratio without PLL operation.
(10 ⁵ samples). This corresponds to an accuracy of a magnetic domain length of ± 0.02 μm or less. Also,
From the magnetic domain observation results, it was found that the magnetic domain width could be controlled with an accuracy of ± 0.05 μm or less. Here, the drive conditions of the disk used are: disk rotation speed: 3000 rpm, disk recording position: r = 30 mm, recording laser wavelength: 780 nm. As described above, although the absolute value of the recording laser power is different, the above-described highly accurate magnetic domain shape control was possible only for the disk in which the ratio of each power level is within a certain range. As a comparative example, Pas = 2.95 mW, Pw1 = 6.1 mW, Pw2 = 6 for a comparative disc having a different structure from the previous disc.
Recording was performed at 1 mW. Where Pw1 / Pas = Pw2 / Pas = 2.0
7, and Pw1 / Pw2 = 1.0. As a result, the amount of edge shift is 15 ns, and when the jitter distribution is calculated, there is no PLL operation, and the window ratio is about 80% (10 ⁵ samplings).
Therefore, considering various margins, it is difficult to realize a recording density of 1 GB / 5.25 inches on one side, and it can be seen that the present invention is effective.

[0012]

According to the present invention, since it is possible to control the recording magnetic domain shape with high accuracy, it is possible to obtain an ultrahigh density magneto-optical recording. According to the present invention, a magneto-optical disk having a recording capacity of 5.25 inch size and 1 GB or more on one side can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a magneto-optical disk drive device.

FIG. 2 is a schematic diagram of a recording waveform.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Maeda 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Metropolitan Research Laboratory, Hitachi, Ltd. (72) Fumio Kugiya 1-280 Higashi Koikeku Ku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory

Claims (10)

[Claims] 1. In magneto-optical recording for recording, reproduction, or erasing using at least a laser beam and an externally applied magnetic field, a recording pulse waveform used for recording has at least four kinds of laser power levels. Recording or erasing is performed by controlling the laser power according to the temperature and the structure of the disk used. Furthermore, at least the read laser level, the intermediate level, and multiple recording levels are used as the laser power level used for recording. A recording method for magneto-optical recording, characterized in that the recording is performed by setting the ratio of the intermediate level to the recording level within a certain range depending on the environmental temperature and the structure of the disc used. 2. The recording pulse waveform used for recording according to claim 1, wherein the ratio of the laser power to the first recording level (higher power level) of the plurality of recording levels is 1.50. Set it to a large value and less than 1.80.
The ratio to the second recording level (low power level) is 1.50
A recording method for magneto-optical recording characterized in that the ratio is set to be larger than 1.80 and smaller than 1.80, and the ratio of the first recording level to the second recording level is set smaller than 1.0 and larger than 0.90. 3. A recording method for magneto-optical recording, characterized in that when the information according to claim 1 is recorded on a disc, the formed edge portion has information. 4. When recording the information according to claim 1 on a disc, it has a waveform in which minute pulses are generated at fixed intervals, and the level of the leading pulse is set to the first recording level. Then, the level of the pulse after that is set as the second recording level, and the level between the pulse and the pulse and the intermediate level between one information code are set as a constant level immediately after the end of the recording pulse of one information code. A recording method for magneto-optical recording characterized in that the read level is set with an interval of. 5. An integer of a write clock having a pulse width or a gap used for recording in a waveform in which minute pulses are generated at a fixed interval for recording the information of claim 4 on a disc. A recording method for magneto-optical recording, characterized by being set to a multiple or an integer. 6. When recording the information according to any one of claims 4 to 5, the pulse width of the head pulse is different from the pulse width of the head pulse, and more advantageously, the pulse width of the head pulse is A recording method for magneto-optical recording characterized by being set wider than the width. 7. When recording the information according to any one of claims 4 to 6 on a disc, the pulse width of the leading pulse and the width of the succeeding pulse are different, and more advantageously, the pulse width of the leading pulse is A recording method for magneto-optical recording characterized in that the pulse width is set wider than the width, and more advantageously, the pulse width is set to an integral multiple or a fraction of the write clock of the disk drive device. 8. When recording information according to any one of claims 4 to 7 on a disc, it is composed of minute pulses, and the intervals between the pulses are equally generated. A recording method for magneto-optical recording, characterized in that it is set to an integral multiple or a fraction of a write clock of a disk drive device. 9. The shortest recording magnetic domain in the modulation system used for recording the information according to claims 1 and 3 on a disk and recording the information by giving information to the formed edge portion. (7) A recording method for magneto-optical recording characterized by being formed by one minute pulse. 10. When recording information according to any one of claims 1 to 9 on a disc, test recording for detecting a change in recording conditions is performed at regular time intervals or when the disc is loaded.
Alternatively, when the optimum recording condition is found from the result before the execution of the recording command and the recording is performed by using the result, the laser power is changed to change the recording laser power and set the recording condition. As a result, recording or erasing is performed by controlling the laser power according to the operating environment temperature and the structure of the disk used, and more advantageously, at least the read level and the intermediate level as the laser power level used for recording. Level, there are multiple recording levels, and the ratio between the intermediate level and the recording level is set within a certain range depending on the operating environment temperature and the structure of the disc to be used. , The power of the laser is the first recording level (higher power) of the intermediate level and the plurality of recording levels. Level) is greater than 1.50,
In addition to setting it lower than 1.80, the ratio of the second recording level (low power level) of the intermediate level and the plurality of recording levels is set to higher than 1.50 and lower than 1.80, and further to the first recording level. A recording method for magneto-optical recording, characterized in that the ratio to the second recording level is set smaller than 1.0 and larger than 0.90.