JPH05114184A - Method and device for recording optical information - Google Patents

Abstract

PURPOSE:To record data with a higher density by overwriting data on a magneto-optical recording medium without leaving predata unerased to obtain good C/N and resolution. CONSTITUTION:A semiconductor laser driving circuit 8 controls the emission power of a semiconductor laser 4 in accordance with data to be overwritten. A recording power setting part 10 constituting the semiconductor laser driving circuit 8 modulates code data A by the recording power. An erasing power gate setting part 9 generates an erasing power gate B by leading and trailing edges of code data A; but if the next recording part is shorter than the elapse of a time (t) which is preliminarily set to that predata is not left unerased, the erasing power gate is released, and a recording power Pw in a high level is irradiated. An erasing power setting part 11 modulates data by the erasing power based on the erasing power gate B, and a reproducing power setting part 12 always adds the reproducing power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recording optical information, and more particularly to recording of optical information on an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film. A recording method and an apparatus thereof.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical disk device has been used as an optical information recording device. In this magneto-optical disk device, a magneto-optical recording film made of a perpendicularly magnetized film such as a TbFeCo thin film is formed on a transparent disk-shaped substrate made of glass, polycarbonate or the like, and focused by a condenser lens via an optical head. The magneto-optical recording film is irradiated with the generated light spot through the transparent substrate, and at the same time, a bias magnetic field is applied to the magneto-optical recording film by a bias magnetic field generating coil in a direction perpendicular to the magneto-optical recording film, so that the irradiated portion of the light spot is irradiated with the magnetic field. It is a new file device that records the magnetization direction as data, and has major features such as large capacity, rewritability, and disk interchangeability.

In the case of the optical power modulation recording method which is generally used in the magneto-optical disk apparatus, when rewriting information, once applying the erase bias magnetic field -He,
After irradiating the focused laser beam to raise the irradiation area above the Curie temperature, an erasing operation is performed to uniformly align the magnetization direction with the erasing bias magnetic field in the process of cooling the magneto-optical recording film. Therefore, a recording bias magnetic field Hw in the direction opposite to the erasing bias magnetic field is further applied to turn the laser beam on and off, thereby recording information as the direction of magnetization.

However, since overwriting cannot be performed with this method, the transfer rate is effectively reduced during recording. On the other hand, if overwriting becomes possible,
Since recording and playback can be performed at the same transfer rate, the data transfer rate is improved and it can be applied to a wider range of fields. Is proposed.

As one of the methods, Masatoshi Sato et al., "Single beam overwrite method using multi-layer magneto-optical recording medium", Proceedings of the 34th Joint Lecture on Applied Physics No28p-ZL-3, An optical power modulation system using an exchange coupling multilayer film described in p. 721 (1987) is known. 9 and 10 regarding this method.
Will be explained.

FIG. 9 is a principle diagram showing a recording process in a magneto-optical disk device.

In FIG. 9, the moving direction of the magneto-optical recording medium progresses from right to left as indicated by an arrow 31. Three
Reference numeral 2 denotes a magneto-optical recording medium, which includes the memory layer 33 and the auxiliary layer 3.
4 and. In FIG. 9, the arrows written in the memory layer 33 and the auxiliary layer 34 indicate the directions of magnetization, respectively. Now, the upward magnetization is referred to as a "1" level recording state, and the downward magnetization is referred to as a "0" level recording state. Reference numeral 35 is an initializing magnetic circuit, 36 is a bias magnetic field applying magnetic circuit, and arrows 39 and 40 indicate the directions of the respective magnetic fields. A condenser lens 37 condenses a light spot 38 from a laser (not shown) on the magneto-optical recording medium 32.

Next, the operation of writing information will be described.

In FIG. 9A, first, the initialization magnetic circuit 35 for generating a strong magnetic field intensity initializes the magnetization of the auxiliary layer 34 in a certain direction. Then, the recording light spot 38 is modulated corresponding to the levels of "0" and "1", and the information is written by the magnetization of the auxiliary layer 34 or the action of the magnetic field by the bias magnetic field applying magnetic circuit 36.

For example, in the case of performing "1" level recording, as shown in FIG. 9B, the power emitted from the laser is set to a high level, and the light spot 38 condensed by the condenser lens 37 is used. Both the memory layer 33 and the auxiliary layer 34 are heated to the Curie temperature or higher, and the magnetic field action of the bias magnetic field applying magnetic circuit 36 in the cooling process causes both the auxiliary layer 34 and the memory layer 33 to be magnetized upward. To be

On the other hand, when recording at "0" level,
As shown in FIG. 9C, the power emitted from the laser is set to a low level, and the light spot 38 condensed by the condenser lens 37 raises only the memory layer 33 to the Curie temperature or higher. Recording is performed by inducing downward magnetization by spin interaction with the magnetization of the auxiliary layer 34.

Through the above process, overwriting with a single beam becomes possible.

Therefore, as shown in FIG. 10, the outgoing light power modulated between the high level recording power Pw and the intermediate level erasing power Pe corresponding to the code data is applied to the magneto-optical recording medium. The information is overwritten by being irradiated.

[0014]

In the above-mentioned conventional optical information recording apparatus, when rewriting information to a magneto-optical recording medium using an exchange coupling alternating multilayer film, a high level recording power Pw and an intermediate level recording power Pw are used. 3 using erase power Pe
There are a method in which overwriting is possible by performing optical modulation of a value level, and a method in which overwriting is not possible by performing recording at a binary level using only the recording power Pw. The former is compared with the latter. The C / N ratio is low, the resolution is poor, and it is difficult to increase the recording density. It is an object of the present invention to perform overwriting on an overwritable magneto-optical recording medium using an exchange-coupling alternating multi-layer film without erasure of pre-data and to obtain a good C /
An object of the present invention is to provide an optical information recording method and apparatus capable of obtaining an N ratio and resolution and achieving high density recording.

[0015]

The optical information recording method of the first invention is a recording method of overwriting a signal by irradiating a light beam onto a magneto-optical recording medium capable of being overwritten by an exchange coupling alternating multilayer film. Yes, depending on the information signal, when switching from the recording part that emits a high level of optical power to the erasing part that emits an intermediate level of optical power, a low level of optical power is emitted for a certain period of time. Is configured.

The optical information recording apparatus of the second invention is a magneto-optical recording / reproducing method for irradiating converged light of a semiconductor laser onto an overwritable magneto-optical recording medium having an exchange coupling alternating multilayer film to record / reproduce information. An optical information recording apparatus including a head is configured to include a semiconductor laser drive circuit that controls the emission power of the semiconductor laser according to overwritten data.

[0017]

Operation: Even in the magneto-optical recording medium that can be overwritten by the exchange-coupling alternating multilayer film, after the pre-data is once erased,
By performing binary recording without applying the erasing power Pe of an intermediate level, C /
The N ratio is high, the resolution is high, and the jitter can be reduced.

For example, FIGS. 6 and 7 show a case where a magneto-optical recording medium using an exchange coupling alternating multilayer film is overwritten by ternary recording and a case where predata is erased and then binary data is written. The result of evaluating the C / N ratio and the recording frequency dependency of the signal amplitude when recording is shown is shown.
From these evaluation results, it can be seen that the binary recording in which the intermediate level erasing power Pe is not applied has a higher C / N ratio and a higher resolution.

FIG. 8 shows that in addition to the presence of pre-data,
The relationship of the erasing rate of pre-data with respect to the length of time of the erasing portion when binary recording is performed is shown. From this, when the erased portion is short, the pre-data can be completely erased at the time of overwriting without adding the erase power Pe, and the C / N ratio is higher than that when the erase power Pe is added. It can be seen that it is high and has little jitter.

Here, the relationship between the length of the erased portion and the erase rate varies depending on the linear velocity of the magneto-optical recording medium. Therefore, by detecting the linear velocity of the magneto-optical recording medium and adjusting the length of the read power immediately after the recording power to reduce it based on the linear velocity, good recording characteristics can be obtained.

[0021]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of an optical information recording apparatus using an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film according to the present invention.
Further, FIG. 2 is a waveform diagram showing the waveform of each part showing the operation of the optical information recording apparatus of FIG.

In FIG. 1, 1 is a magneto-optical recording medium, 2 is a spindle motor, 3 is an optical head, 4 is a semiconductor laser, 5 is a preamplifier, 6 is a demodulator, 7 is an encoder, 8 is a semiconductor laser drive circuit, 9 is an erase power gate setting section, 1
0 is a recording power setting unit, 11 is an erasing power setting unit, and 12
Is a reproducing power setting unit, and 13 is a linear velocity detecting unit.

Next, the operation will be described. In FIG. 1, a recording data signal a is converted by an encoder 7 into code data recorded on a magneto-optical disk, for example, code data A as shown in FIG. Based on this code data A, the semiconductor laser driving circuit 8 causes the semiconductor laser 4
2 is driven, the light output power C shown in FIG. 2 is transmitted from the optical head 3 to the spindle motor 2 for the code data A.
Information is rewritten by irradiating the rotating magneto-optical recording medium 1 with. When reproducing the information written on the magneto-optical recording medium 1, the optical head 3 detects the information signal, the preamplifier 5 amplifies the detected signal, and the demodulator 6 reproduces the data. It has become a structure.

In the semiconductor laser drive circuit 8, the recording power setting section 10 first modulates the code data A by the recording power. In addition, the erase power gate setting unit 9 creates the erase power gate B from the falling edge and the rising edge of the code data A as shown in FIG. However, the next recorded portion is time t
If it is earlier than, the erase power gate is released and the high level recording power Pw is irradiated. Then, the time t of the erase power gate is set to such a length that no unerased portion of pre-data remains. Based on the erasing power gate B, the erasing power setting unit 11 modulates the erasing power, and the reproducing power setting unit 12 constantly adds the reproducing power.

In the conventional recording method, the light emission power is set to the intermediate level erasing power Pe when the recording portion irradiated with the high level optical power Pw is changed to the erasing portion. The power is set to a low level reproduction power Pr for a certain period of time t, and then the remaining erased portion is set to the erase power Pe. Of course, as described above, when the next recording portion is earlier than the time t, the erasing power gate is released and the high level recording power Pw is applied.

As described above, when the high level of the recorded portion is switched to the intermediate level of the erased portion, the reproduction power of the low level is dropped for a certain period of time, and then the erase power of the intermediate level is set, whereby the pre-data Good recording characteristics can be obtained without erasing residue, and high density recording can be realized.

Next, FIG. 5 shows an erase power gate setting section 9
FIG. 3 shows a block diagram of an embodiment of the present invention.

In FIG. 5, reference numeral 81 is a variable delay line. Magneto-optical recording medium 1 detected by the linear velocity detector 13
The length t of the erase power gate is set based on the linear velocity of

The time t of this erase power gate is set to a length such that the unerased portion of the pre-data does not remain. This time t changes depending on the magneto-optical recording medium and its linear velocity. The optimum value of t with respect to the linear velocity is recorded on the magneto-optical recording medium 1 in advance, and when the magneto-optical recording medium 1 is inserted into the drive, the information is read and the variable delay line 81 corresponding to the linear velocity is read. Depending on the configuration, the size of the time t may be set.

By using such a circuit, the erase power gate B having a required length can be formed from the falling edge and the rising edge of the code data A. This method
Irrespective of the data pattern of pre-data or recorded data, and without referring to them,
There is an advantage that it can be realized with a simple circuit.

The optical information recording apparatus shown in FIG. 3 may be used instead of the magneto-optical disk apparatus shown in FIG. 1, and the signal waveforms shown in FIG. 4 may be used instead of the signals of the respective portions shown in FIG.

In this case, in the part where the erase power is removed in the erase part, the reproduction power is also removed to eliminate the emission power, and this method further improves the C / N ratio and increases the output power. It is possible to achieve the recording density. In order to realize this, the gate signal generated by the erase power gate setting unit 9 may be added to the reproduction power setting unit 12 and the application state of the reproduction power may be controlled in the same manner as the erase power.

As described above, ternary level optical modulation using a high level recording power and an intermediate level erasing power is performed on the magneto-optical recording medium using the exchange-coupling alternating multilayer film, and overwriting is possible. In the case of this method, when switching from the recording part that is radiating a high level of optical power to the erasing part that is radiating an intermediate level of optical power, the playback power is dropped for a certain period of time and then the intermediate level of erasing power is set. As a result, it is possible to overwrite without erasing the pre-data, obtain a good C / N ratio and resolution, and as a result, reduce the jitter and the error rate,
Higher recording density can be achieved.

[0035]

As described above, the optical information recording method and apparatus according to the present invention have a high level recording power and an intermediate level erasing power for a magneto-optical recording medium using an exchange coupling alternating multilayer film. In the case of a method capable of overwriting by performing ternary-level light modulation using and, when switching from a recording portion irradiating a high level optical power to an erasing portion irradiating an intermediate level optical power, By lowering the reproduction power for a certain period of time and then changing it to the intermediate level of the erasing power, it is possible to overwrite without erasing the pre-data, obtain a good C / N ratio and resolution, and as a result, reduce the jitter. Error rate is reduced,
This has the effect of increasing the recording density.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an optical information recording apparatus using an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film according to the present invention.

FIG. 2 is a waveform diagram showing waveforms of various parts showing the operation of the optical information recording apparatus of FIG.

FIG. 3 is a configuration diagram showing a second embodiment of an optical information recording apparatus using an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film according to the present invention.

FIG. 4 is a waveform diagram showing waveforms of various parts showing the operation of the optical information recording apparatus of FIG.

5 is a block diagram of an embodiment of an erase power gate setting unit 9. FIG.

FIG. 6 is a diagram showing C in the case of overwriting with ternary recording and in the case of erasing predata and then recording with binary recording.
It is a figure which shows the result of having evaluated the recording frequency dependence of / N ratio.

FIG. 7 is a diagram showing the results of evaluating the recording frequency dependence of the signal amplitude in the case of overwriting in ternary recording and in the case of erasing pre-data and then recording in binary recording.

FIG. 8 is a diagram showing a relationship of a pre-data erasing rate with respect to a length of time of an erasing portion when binary recording is performed.

FIG. 9 is a principle diagram showing a recording process in a magneto-optical disk device.

FIG. 10 is a waveform diagram showing waveforms of code data recorded in a conventional optical information recording device and a light emission power applied to a magneto-optical recording medium.

[Explanation of symbols]

 1 Magneto-optical recording medium 2 Spindle motor 3 Optical head 4 Semiconductor laser 5 Preamplifier 6 Demodulator 7 Encoder 8 Semiconductor laser drive circuit 9 Erase power gate setting section 10 Recording power setting section 11 Erase power setting section 12 Reproduction power setting section 13 Wire Speed detection unit 31 Medium traveling direction 32 Magneto-optical recording medium 33 Memory layer 34 Auxiliary layer 35 Initializing magnetic circuit 36 Bias magnetic field applying magnetic circuit 37 Condenser lens 38 Optical spot 39, 40 Arrow 81 Variable delay line

Claims (2)

[Claims] 1. A recording method of overwriting a signal on a magneto-optical recording medium capable of being overwritten by an exchange coupling alternating multilayer film by irradiating a light beam, and irradiating a high level of optical power in accordance with an information signal. A method of recording optical information, which comprises irradiating a low level optical power for a certain period of time when switching from a recording part to an erasing part which radiates an intermediate level optical power. 2. An optical information recording apparatus equipped with a magneto-optical head for recording and reproducing information by irradiating converged light of a semiconductor laser onto an overwritable magneto-optical recording medium comprising an exchange-coupling alternating multilayer film. An optical information recording apparatus comprising a semiconductor laser drive circuit for controlling an emission power of the semiconductor laser according to data to be written.