JPH0757326A - Method and device for magneto-optical recording - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording method recording by eliminating thermal interference between formed recording domains. CONSTITUTION:A recording pattern formed according to a fixed modulation system is recorded on the same or different track on a magneto-optical recording medium by dividing into plural times and at least using a laser beam. When recording by dividing into two times, first of all, a recording code M recorded on every other one, and the domains 111 are formed, and succeedingly remaining recording is performed, and the domains 112 are formed. The domains are recorded without receiving the thermal interference. By irradiating the light beam while separating a certain distance, two-dimensional recording may be performed on the same track.

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 method for recording using at least a laser beam and a magneto-optical recording apparatus for carrying out the method.

[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 recording has been put to practical use. Following this, as a second-generation magneto-optical disk device, a device having a recording capacity three times as large as that of the first-generation magneto-optical disk device has been studied for practical use. Further, as magneto-optical recording for the third generation and thereafter, research and development are being advanced with the aim of further increasing the recording capacity. In order to realize higher density recording, a recording / reproducing system, signal processing, development of a recording medium suitable for high density recording, and the like are being carried out in parallel. Among them, when recording a high density of minute magnetic domains, how to suppress thermal interference between recording bits is an important issue.

To solve this problem, Japanese Patent Laid-Open No. 3-22
223 has been proposed. In this method, the recording code sequence in the recording domain is pulsed to form a series of pulse sequences corresponding to the length of the recording code sequence, and the length and amplitude of the pulse sequence are set to the opposite phase of the recording code sequence immediately before the recording code sequence. Control according to the length of the pulse train, and also according to the length of the pulse train
Recording is performed by changing the pulse width of each pulse.

[0004]

The above-mentioned conventional technique suppresses thermal interference between recording domains formed by controlling the pulse width, but there is a problem in that there is a limit to the suppression. . Particularly, when the recording density becomes high and the domains come close to each other, the recording by the next recording pulse is performed before the recording film is sufficiently cooled.
Thermal interference occurred and it was difficult to form a minute recording domain. This problem has been an obstacle to improving the recording density not only when the mark length is recorded but also when the pit position is recorded.

An object of the present invention is to provide a magneto-optical recording method for recording by removing thermal interference between recording domains formed. Another object of the present invention is to provide a magneto-optical recording device suitable for performing the above.

[0006]

In order to achieve the above object, the magneto-optical recording method of the present invention comprises at least a recording pattern formed on a magneto-optical recording medium according to a certain modulation method, divided at least a plurality of times. Recording is performed on the same or different tracks by using a laser beam.

This method allows two-dimensional recording on the same track. For example, when recording is performed by a plurality of light beams, and the recording domains formed by the respective light beams are irradiated with the light beams at a certain distance so as not to be thermally interfered with each other, the same track is formed. It is possible to record in two dimensions. In addition, when recording with multiple light beams,
It is also possible to adopt a method of recording by irradiating a light beam at a certain distance in one dimension. The above certain distance is preferably in the range of 30 μm to 60 μm. This is because if the thickness is less than 30 μm, the subsequent beam is irradiated while the influence of heat of the preceding beam remains after the recording domain is formed by the preceding beam, which affects the domain size and the like. , Again, 60 μm
This is because if the value exceeds, the structure of the device for obtaining the accuracy of the recording position becomes more complicated and the lens diameter must be increased.

In order to prevent the formed recording domains from being thermally interfered with each other, it is also possible to record the recording pattern a plurality of times at desired intervals. For example, the magneto-optical recording medium may be a magneto-optical disk, and the desired time may be a time during which the magneto-optical disk makes one revolution. That is, in the first rotation, every other recording bit that constitutes the encoded recording pattern for recording is recorded, and in the next rotation, the remaining recording bits are recorded.
In the case of a higher domain density, it is effective to use a method such as recording every two, three times, or recording every third, four times.

Further, it is preferable to use a recording laser pulse having a pulse width of 20 ns or less and 10 ns or more.

Further, in order to achieve the above-mentioned other objects,
The magneto-optical recording apparatus of the present invention has a holding means for holding a recording medium, an optical head for recording and reproducing information on the recording medium, and a recording pattern formed according to a certain modulation method, which is dispersed into a plurality of pieces. A recording code dispersion device, an optical head drive system for recording the distributed recording code a plurality of times on the same or different tracks of the recording medium via the optical head, and a reproduction signal obtained from the optical head. Is composed of a processing system for converting the data into information and a recording control commander for controlling these.

Further, when the optical head drive system records the dispersed recording code on different tracks, the above processing system:
It is necessary to include a recording code synthesizing device for synthesizing a plurality of distributed recording patterns into an original recording pattern.

[0012]

The recording domain is formed by recording at a constant time interval or at a constant distance.
Thermal interference between recording domains can be eliminated. Therefore, the first bit is recorded by recording at least every other recording bit, instead of continuously recording a series of recording code strings, and then the portion is cooled. Since the recording bits adjacent to each other are recorded after the first recording, recording can be performed without thermal interference. Also, when a plurality of beams are used to divide and record a series of recording code strings for the preceding beam and the subsequent beam, recording can be performed without causing thermal interference between the recording bits.

[0013]

EXAMPLES The present invention will be described in more detail with reference to examples. <Embodiment 1> FIG. 2 shows a schematic view of the cross-sectional structure of the disk used in this embodiment. A silicon nitride film (2) having a film thickness of 75 nm was formed on a plastic or glass substrate (1) having an uneven guide groove by a sputtering method.
On top of that, a TbFeCo film (3) was formed as a recording film by 30
It was formed to a film thickness of nm. The magnetic characteristics at that time were as follows: compensation temperature: Tcomp = 60 ° C., Curie temperature: Tc = 220.
C, and coercive force: Hc = 14 kOe. Further, a silicon nitride film (4) was formed with a film thickness of 20 nm by a sputtering method. Finally, an Al ₉₈ Ti ₂ film (5) for light reflection and heat diffusion was formed to a film thickness of 50 nm. These entire surfaces were covered with an ultraviolet curable resin (6). The two disks thus produced were bonded together with an adhesive so that the surfaces on which the recording film was formed faced each other, and a recording medium was manufactured.

The recording medium produced in this manner is recorded in FIG.
Information was recorded using the recording / reproducing apparatus having the configuration shown in. This recording / reproducing apparatus has a holding means (29) for holding a recording medium (11), an optical head (12) for recording and reproducing information on the recording medium (11), and a recording code string of information. A recording code string distribution device (32) for distributing a plurality of
An optical head drive system (recording waveform generator (15), APC (automatic power control means) (1) for recording the dispersed recording code on the recording medium (11) via the optical head (12)
6), a laser driver (17), and a processing system (reproducing amplifier (20), waveform equalizer (21), input selector (22) for converting the reproduced signal obtained from the optical head (12) into information. )
Etc.) and a recording control commander (33) for controlling them. Further, the optical head (12) has a built-in optical system that narrows the light emitted from the laser (18) onto the recording medium (11).

When recording information, the input data bit string (information) is input to the encoder (14), and the recording code string is output from the encoder (14). The recording code sequence is dispersed into a plurality by the recording code sequence distribution device (32). For example, every other recording code sequence is dispersed. This alternate output is guided to the recording waveform generator (15), the waveform obtained here is input to the APC (16), and light corresponding to the dispersed recording code string is output from the laser (18). To be done. Then, the rest of the distributed recording code sequence is similarly processed by the laser (18).
Is input to and light corresponding to this is output.

At the time of reproducing information, the light reflected from the recording medium (11) is guided by the optical system to the light receiver (19) and converted into an electric signal. This signal is input to the reproduction amplifier (20) and output to the waveform equalizer (21) and the input switch (22). The input switching device (22) is a reproduction amplifier (20).
Alternatively, the reproduced signal of either the waveform equalizer (21) is output to the shaper (23). The reproduction signal is converted into a pulse signal by the shaper (23) and is guided to the discriminator (25) and the PLL (phase compensator) (24). The synchronization signal (signal synchronized with the basic cycle of the pulse signal) output from the PLL (24) is input to the discriminator (25). Discriminator (2
5) generates a recording code string from the pulse signal and the synchronizing signal, and outputs a data bit string (information) by the decoder (27). The recording code string of the discriminator (25) is output to the comparison discriminator (26).

Here, a method of recording information will be described.
The recording signal waveform as shown in FIG. 1 was divided into two groups and recorded. Here, recording was performed so that the recording density was the same at any position on the recording medium. This was done by changing the recording frequency at the inner and outer circumferences of the recording medium. The pit position method was used as the recording method. The first group was recorded on the first rotation of the recording medium to form the domain (111), and the second group remaining on the second rotation was recorded to form the domain (112) on the same track. The formed domain was circular and had a size of 0.35 μm. Here, the wavelength of the laser light used for recording is 680 nm, and the modulation method is the (1,7) RLL method. For ultra-high density recording, the (1,7) RLL method is a modulation method which has a wide detection window width and is advantageous also in terms of S / N of a disc.

Since the recording temperature of magneto-optical recording is as low as less than 200.degree. C., it is easily affected by room temperature fluctuations and laser power fluctuations in the recording / reproducing apparatus. Therefore, by performing trial writing, the fluctuation can be detected, and the accuracy of recording control can be further improved. Even a slight variation affects the controllability of recording, and in particular, the higher the recording density, the greater the effect, and it is important to improve the controllability.
The second-order differential method was used to reproduce the recorded information.

This test writing will be described in detail with the use of the recording / reproducing apparatus shown in FIG. By the trial writing command signal, from the trial writing device (13) of the recording / reproducing apparatus,
The trial writing data is input to the encoder (14) and converted into a recording code string. The recording code string of this trial writing data is
It is recorded on the recording medium (11) through the same path as the recording information. In the evaluation of the trial writing data, the input switch (22) operated by the trial writing command signal is the reproduction amplifier (2
The output of 0) is switched to be output to the shaper (23). In this way, the control for driving the laser (18) so as to compare the recording code sequence from the encoder (14) with the reproduction code sequence from the discriminator (25) and cancel the difference in the reproduction code sequence from the recording code sequence. The signal is input to the APC (16). As a result of such control, the difference between the reproduced code string and the recorded code string becomes small to some extent, and when the allowable range is reached, the test writing end signal is output and the test writing ends.

After the trial writing end signal is output, the input switching device (22) switches the output of the waveform equalizer (21) to the shaping device (23) to start a normal recording / reproducing operation. To do. Even after the normal recording / reproducing operation is started, the comparison discriminator (26) confirms that the difference in the reproduced code string from the recorded code string is within the allowable range. Start the operation again.

The edge shift of the recording domain thus recorded was measured and found to be ± 1 ns or less.
On the other hand, unlike the present example, when the recording signal waveform was continuously recorded without division, the edge shift of the formed recording domain was significantly large, ± 8 ns. When the recording domain formed by the magnetic force microscopy method (MFM method) was observed, it was found that the length of the recording domain was long or deformed. Moreover, it was found that the adjacent magnetic domains were close to each other below the resolution as a result of thermal interference between the adjacent recording domains. Considering the case of recording by using the present invention, it was clarified from the result of magnetic domain observation that recording could be performed without receiving thermal interference. Thus, it can be seen that the present invention is effective in eliminating thermal interference between recording domains.

<Embodiment 2> In Embodiment 1, the distributed recording code is recorded on the same track of the recording medium (11), but in this embodiment, the distributed recording code is recorded on different tracks. The example recorded in is shown below. The recording / reproducing apparatus for performing this recording / reproducing is the recording / reproducing apparatus shown in FIG. is there. FIG. 5 shows this recording / reproducing apparatus. The same parts as in FIG. 3 are omitted.

Recording is performed by the same method using the same recording medium as in Example 1, but the dispersed recording codes are recorded on different tracks. At the time of reproducing information, the signal read from the first track is converted into a recording code string dispersed by the discriminator (25) as in the first embodiment. Next, the signal read from the second track is converted into the other dispersed recording code string. These distributed recording code strings are combined by a recording code string synthesizing device (26), and a data bit string (information) is output by a decoder (27). The distribution of the recording code is the same as in the first embodiment
Similarly to the above, an example in which the data is distributed in two is shown, but it goes without saying that the number may be more than that.

<Embodiment 3> An example using a mark length recording method as a recording method will be described. The same recording medium and recording / reproducing apparatus as those used in Example 1 were used. Here, when recording information on the recording medium, the recording pattern was divided into three and recorded three times. As a result, the magnetic domain width is 0.38 μm,
The shortest magnetic domain length is 0.38 μm. In this case, the shortest bit interval is 0.38 μm. Jitter was measured for the recording pattern thus recorded. As a result, when the edge shift was measured, it was ± 1 ns or less, and the jitter was 29% as small as the window ratio. Here, as the detection method, the original waveform detection method was used, and 2PLL was applied.

<Embodiment 4> An example using so-called two-dimensional correlation recording in which two-dimensional recording is performed in the disk surface direction and recording is performed according to the positional relationship of recording domains will be described as a recording method.
The light spot was 3 beams in this embodiment. this is,
This is in consideration of the improvement of data transfer speed and reproduction. By recording using a plurality of beams in this way, the data transfer speed becomes faster than in the case of recording in a plurality of rotations in the above embodiment. On the other hand, although the apparatus becomes complicated, the more the light beam is used, the more the advantage that the thermal interference for recording can be eliminated.

This recording method will be described with reference to FIG. In the tracks between the grooves, three rows of recording domains are formed at a distance of 0.725 μm in the direction perpendicular to the tracks. The beam intervals are 30 μm or more during recording.
That is, when the light beam forming the recording domain of the first column forms the recording domain of the first row, the light beam forming the recording domain of the second column is, for example, the recording domain of the tenth row. To form. Further, the light beam forming the recording domain in the third column forms the recording domain in the 20th row.

In this recording method, since the recording domains are naturally close to each other in the related art, when a metal having a high thermal conductivity is used as the recording film, the heat is diffused to the periphery irradiated with the light beam, and therefore the recording domains are continuously formed. In the case of recording, since the influence of the heat of the preceding beam is applied when the subsequent beam is irradiated, it is necessary to separate a certain distance, but in the case of this embodiment, high density recording can be performed, and further, the MFM It was found from the result of observation by the method that the recording domain was well formed.

During reproduction, the three beams are used, and the signal difference obtained from the three beams is subjected to a certain signal processing, whereby the crosstalk from the recording domains can be canceled.

[0029]

According to the present invention, thermal interference can be eliminated by a method of forming recording domains by recording at regular time intervals. for that reason,
The first bit is recorded by recording the recording bit by dividing the recording bit into, for example, every other bit instead of continuously recording a series of recording code strings, and then the portion is cooled. Since adjacent recording bits are recorded from, it was possible to record without thermal interference. In addition, by using a plurality of beams and dividing a series of recording code strings into a preceding beam and a succeeding beam and performing recording, recording can be performed without causing thermal interference between recording bits. As a result, ultra-high density recording was realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a recording method of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of an example of an optical disc used in the present invention.

FIG. 3 is a diagram showing a configuration of an example of a recording / reproducing apparatus of the present invention.

FIG. 4 is a diagram for explaining a two-dimensional correlation recording method.

FIG. 3 is a diagram showing a configuration of an example of a recording / reproducing apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk substrate 2 ... Silicon nitride film 3 ... TbFeCo film 4 ... Silicon nitride film 5 ... Al ₉₈ Ti ₂ film 6 ... UV curable resin 11 ... Recording medium 12 ... Optical head 13 ... Trial writer 14 ... Encoder 15 ... Recording Waveform generator 16 ... APC (automatic power control means) 17 ... Laser driver 18 ... Laser 19 ... Photoreceiver 20 ... Reproduction amplifier 21 ... Waveform equalizer 22 ... Input switch 23 ... Shaper 24 ... PLL (Phase compensator) ) 25 ... Discriminator 26 ... Comparison discriminator 27 ... Decoder 29 ... Holding device 32 ... Recording code string dispersing device 33 ... Recording control command device 34 ... Recording code string synthesizing device 111, 112 ... Domain

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[Procedure amendment]

[Submission date] August 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a recording method of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of an example of an optical disc used in the present invention.

FIG. 3 is a diagram showing a configuration of an example of a recording / reproducing apparatus of the present invention.

FIG. 4 is a diagram for explaining a two-dimensional correlation recording method.

FIG. 5 is a diagram showing a configuration of an example of a recording / reproducing apparatus of the present invention.

Claims (11)

[Claims] 1. A magneto-optical recording method for recording information on a magneto-optical recording medium using at least a laser beam,
A magneto-optical recording method, wherein a recording pattern formed according to a certain modulation method is divided into a plurality of times and recorded on the same or different tracks. 2. The magneto-optical recording method according to claim 1,
The magneto-optical recording method is characterized in that the recording of the recording pattern is performed two-dimensionally on the same track. 3. The magneto-optical recording method according to claim 1, wherein the recording of the recording pattern is performed by a plurality of light beams, and the recording domains formed by the respective light beams are mutually thermal. A magneto-optical recording method comprising irradiating a light beam with a desired distance so as not to be interfered with. 4. The magneto-optical recording method according to claim 3,
The magneto-optical recording method, wherein the desired distance is in the range of 30 μm to 60 μm. 5. The magneto-optical recording method according to claim 1,
Magneto-optical recording characterized in that the recording of the recording pattern is performed at a plurality of times with a desired time interval so that the recording domains formed by each recording do not receive thermal interference with each other. Method. 6. The magneto-optical recording method according to claim 5,
The magneto-optical recording medium is a magneto-optical disk, and the desired time is a time during which the magneto-optical disk makes one revolution substantially. 7. The magneto-optical recording method according to claim 1, wherein the recording is performed using a recording laser pulse having a pulse width of 20 ns or less. 8. A magneto-optical recording method according to claim 1, wherein the recording is performed at the same recording density at any recording position of the magneto-optical recording medium. Magnetic recording method. 9. The magneto-optical recording method according to claim 1, wherein test writing is performed before the recording, and the recording condition is changed based on the result. And a magneto-optical recording method. 10. A holding means for holding a recording medium, an optical head for recording and reproducing information on the recording medium, a recording code dispersion device for distributing a plurality of recording patterns formed according to a certain modulation method, An optical head drive system for dividing the distributed recording code into a plurality of times and recording on the same or different tracks of a recording medium via the optical head, a processing system for converting a reproduction signal obtained from the optical head into information, and A magneto-optical recording apparatus having a recording control commander for controlling these. 11. A magneto-optical recording apparatus according to claim 10, wherein said optical head drive system is an optical head drive system for recording on different tracks of a recording medium, and said processing system is distributed in plural. A magneto-optical recording device comprising a recording code synthesizing device for synthesizing a recording pattern into an original recording pattern.