JPH1092036A - Magnetooptical recording and reproducing method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the change of the deflection surface of reflection light a desired phase by previously correcting/recording the difference of the starting times of magnetic domain wall movement to the position of a light beam caused at the time of magnetic domain wall movement between the expanding direction and the reducing direction of a recording mark at the front end and/or rear end. SOLUTION: A signal processing circuit 22 detects a correcting amount, for the deviation of moving timing between the expanding direction and the reducing direction of a recording mark at the time of magnetic domain wall movement and for time shortening by always a fixed time to the time complied with the recording mark at the time of reproduction, from the output of a differential amplifier 18. By adjusting the phase of modulated magnetic field and driving a magnetic head 23 through a magnetic head driver 24 based on the output of the signal processing circuit 22, a recording phase adjusting circuit 21 corrects the time shortening complied with the length of recording mark. Consequently, the detection of the deflection surface is enabled with a desired phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a temperature gradient of a medium temperature with respect to a magnetic domain of a medium caused by irradiation of a light beam to move a domain wall of a recording mark of a reproducing layer without changing recording data of the recording layer. The present invention relates to a magneto-optical recording / reproducing method and a magneto-optical recording / reproducing apparatus capable of detecting a change in a deflection surface of a reflected light of a beam and reproducing a recording mark below a diffraction limit of the light beam.

[0002]

2. Description of the Related Art As a rewritable high-density recording medium,
There is a magneto-optical recording medium on which information is recorded by writing magnetic domains on a magnetic thin film using the heat energy of a semiconductor laser and reading this information using a magneto-optical effect. In recent years, there has been an increasing demand for a higher-capacity recording medium by further increasing the recording density of the magneto-optical recording medium. The linear recording density of an optical disc such as a magneto-optical recording medium is determined by the laser wavelength of the reproducing optical system and
It largely depends on the numerical aperture of the objective lens. That is, since the beam waist diameter is determined when the laser wavelength λ of the reproducing optical system and the numerical aperture NA of the objective lens are determined, the spatial frequency at the time of recording mark reproduction is a spatial frequency band in which about 2NA / λ can be detected. I will. Therefore, in order to realize a higher density in a conventional optical disk, it is necessary to shorten the laser wavelength of the reproducing optical system and increase the numerical aperture NA of the objective lens. However, there is a limit to the improvement of the laser wavelength and the numerical aperture of the objective lens. For this reason, techniques for improving the recording density by devising the configuration of the recording medium and the reading method have been developed.

For example, in Japanese Patent Application Laid-Open No. 06-290496, signal recording is carried out on a multi-layered recording holding layer having a magnetic layer and a reproducing layer and a recording holding layer and having different Curie temperatures. By using the temperature gradient by irradiating the recording light beam, the domain wall of the recording mark of the reproducing layer is moved without changing the recording data of the recording holding layer so that almost the entire area of the reproducing light beam spot has the same magnetization. A signal reproducing method and apparatus have been proposed in which a reproducing layer is magnetized to detect a change in a deflecting surface of a reflected light of the reproducing light beam and to reproduce a recording mark having a diffraction limit of the light beam or less. According to this method, as shown in FIG. 11, a large circular heating beam, a small circular recording / reproducing beam in the heating beam, and an elliptical Ts isothermal corresponding to the beam moving speed at the time of the reproducing. It is a state diagram in each movement corresponding to the recording magnetic domain with a line, the reproduction signal shown at the bottom becomes rectangular, and the recording mark having a period equal to or less than the diffraction limit of light is reproduced without reducing the reproduction signal amplitude. This makes it possible to provide a magneto-optical recording medium and a reproducing method capable of greatly improving the recording density and the transfer speed.

[0004]

However, according to the above-mentioned prior art, the guide groove portion of the magneto-optical recording medium is irradiated with high-power laser light to anneal the magnetic layer in the guide groove portion, and the guide groove is annealed. It is necessary that the magnetic wall of a part of the magnetic layer is deteriorated and a recording mark is not formed in a closed loop, that is, a closed shape. Further, even in this case, the domain walls at the front and rear ends of the recording mark are not completely separated / independent, and are in a state where they have a relationship affecting each other. Therefore, when the domain wall of the recording mark moves in the recording mark enlargement direction,
That is, the energy at which the magnetic domain in the case of the original closed magnetic domain starts to expand, and the energy at which the magnetic domain of the recording mark domain moves in the recording mark reduction direction, that is, the energy for reducing the magnetic domain in the case of the original closed magnetic domain. Will be different. That is, a difference occurs in the medium temperature at which the domain wall starts moving. Therefore, as shown in FIG.
In the laser beam irradiation DC irradiation during reproduction, the thermal is Considering that is saturated, when the expansion of the recording marks, the domain wall starts moving at the time the reproduction layer temperature of the recording medium has reached T _l On the other hand, when the recording mark is reduced, the domain wall starts moving at the time when the recording medium reproducing layer temperature reaches _Tt . Accordingly, a difference occurs in the positional relationship of the reproduction beam at the time when the domain wall reaches the medium temperature at which movement starts, and
There is a time difference between the front and rear ends of the magnetic domain of the recording mark and the change of the deflection surface to be detected / reproduced. Here, the T _S temperature region is shown in the figure, and this is a region in which the layer called the intermediate layer, which magnetically couples the reproducing layer and the recording layer, has an increased temperature above the Curie temperature. This indicates that within this temperature range, the main condition that the domain wall in which the recording layer and the reproducing layer are uncoupled move is satisfied.

Due to the above-described factors, as shown in FIG. 11, the movement timing is shifted between when the domain wall moves in the recording mark enlargement direction and when the domain wall moves in the reduction direction, and the time corresponding to the recording mark is always shortened by a fixed time. There is a problem that it is detected.

[0006] In the portions showing recording marks in the figure, the hatched portions indicate the magnetization state of the recording medium corresponding to the recording marks described in this specification, and the hatched portions indicate the magnetization states in which the magnetization states are opposite. I have.

Further, by utilizing the temperature gradient of the medium temperature with respect to the magnetic domain of the medium caused by the irradiation of the light beam, the domain wall of the recording mark of the reproducing layer is moved without changing the recording data of the recording layer, and the reflected light of the light beam is reflected. In this magneto-optical recording and reproducing method of detecting a change in the deflection surface and reproducing a recording mark,
Reproduction of a recording mark below the diffraction limit of the light beam becomes possible, and almost the entire area within the spot of the reproduction light beam has the same magnetization, so that it is also affected by the band of the reproduction signal processing system.
As shown in the reproduction signal in FIG. 11, the reproduction signal has a problem that it has a rectangular waveform with a narrow pulse width with respect to the recording signal.

[0008]

The above-mentioned problem is solved by the following means.

First, the recording / reproducing method of the present invention utilizes the temperature gradient of the medium temperature with respect to the magnetic domain of the medium due to the irradiation of the light beam to form the domain wall of the recording mark of the reproducing layer without changing the recording data of the recording layer. In the magneto-optical recording / reproducing method of reproducing the recording mark by detecting the change in the deflecting surface of the reflected light of the light beam by moving the spot to make substantially the entire area of the spot of the reproducing light beam the same magnetization, The difference between the domain wall movement start time with respect to the domain wall position generated at the front end and the rear end is recorded by correcting the position of the front end and / or the rear end of the recording mark in advance so that the reflection generated at the front end and the rear end of the recording mark is obtained. This is a magneto-optical recording / reproducing method characterized in that a change in a light deflection surface is set to a desired phase.

In a magnetic field modulation recording method in which a recording mark is formed by irradiating a light beam with DC light and modulating a magnetic field to be applied, the position of the front end and / or the rear end of the recording mark is corrected by changing the phase of the modulation magnetic field. It is characterized by executing by changing, while irradiating the light beam with pulses,
In a pulse-assisted magnetic field modulation recording method in which a recording mark is formed by modulating a magnetic field to be applied, the position of the front end and / or the rear end of the recording mark is corrected by the light beam power and / or the phase of the assist pulse light, Characterized by performing by changing the phase of the modulation magnetic field,
In the light modulation recording method of forming a recording mark by applying a constant magnetic field and modulating the light beam intensity, the position of the front end and / or the rear end of the recording mark is corrected by the phase of the light beam and / or the light beam power. And a magneto-optical recording / reproducing method characterized in that the method is executed by changing

Secondly, the recording / reproducing apparatus of the present invention utilizes the temperature gradient of the medium temperature with respect to the magnetic domain of the medium due to the irradiation of the light beam to form the domain wall of the recording mark of the reproducing layer without changing the recording data of the recording layer. In the magneto-optical recording / reproducing apparatus for detecting the change of the deflecting surface of the reflected light of the light beam and reproducing the recording mark, in the magneto-optical recording / reproducing apparatus, Recording means for pre-correcting the position of the front end and / or rear end of the recording mark and recording the difference, and pre-correcting and recording the position of the front end and / or rear end of the recording mark to record the difference; A magneto-optical recording / reproducing apparatus characterized in that a change in a deflection surface of reflected light generated at a front end and a rear end is set to a desired phase.

In a magnetic field modulation recording apparatus that forms a recording mark by modulating a magnetic field to be applied by irradiating a light beam with DC light, the position of the front end and / or the rear end of the recording mark is corrected by changing the phase of the modulation magnetic field. It is provided with means for changing and recording, wherein the mark position is corrected and recorded,
In a pulse-assisted magnetic field modulation recording apparatus that forms a recording mark by irradiating a pulse with a light beam and modulating an applied magnetic field, the position of the front end and / or the rear end of the recording mark is corrected by the light beam power and / or Means for recording by changing the phase of the assist pulse light and / or the phase of the modulating magnetic field, wherein the recording is performed by correcting the mark position, while applying a constant magnetic field and modulating the light beam intensity In the light modulation recording method for forming a recording mark, the position of the front end and / or the rear end of the recording mark is corrected by changing the phase of light beam and / or the power of the light beam and recording the mark. A magneto-optical recording / reproducing apparatus characterized in that a position is corrected and recorded.

According to the present invention, a time difference is generated between the movement start time when the leading end of the recording mark moves in the recording mark enlargement direction and the movement start time when the trailing end of the recording mark moves in the recording mark reduction direction. This can solve the problem that the movement timing is shifted between the movement in the recording mark enlargement direction and the movement in the reduction direction, and the recording mark is always detected for a short period of time. Detection becomes possible, jitter is suppressed, read errors are reduced, information can be recorded / reproduced at a low error rate, and a higher density magneto-optical recording method and apparatus can be provided.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] FIG. 1 shows the configuration of a magneto-optical recording / reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a domain wall of a recording mark of a reproducing layer without changing recording data of a recording layer on a substrate 2 made of glass or plastic using a temperature gradient of a medium temperature with respect to a magnetic domain of a medium caused by light beam irradiation. Is moved so that almost the entire area within the reproduction spot has the same magnetization, the change in the deflection surface of the reflected light of the light beam is detected, and the magneto-optical recording medium 3 capable of reproducing the recording mark is deposited. This is a magneto-optical disk on which a protective film 4 is formed. The magneto-optical disk 1 is supported by a spindle motor by magnet chucking or the like, and has a structure rotatable with respect to a rotating shaft. 5 to 17 are schematic elements of individual components constituting an optical head for irradiating the magneto-optical disk 1 with a laser beam and obtaining information from the reflected light, 6 is a condenser lens, and 5 is a condenser lens 6. An actuator to be driven, 7 a semiconductor laser having a wavelength of 680 nm for recording and reproduction, 8 a semiconductor laser having a wavelength of 1.3 μm for heating,
9 and 10 are beam shaping lenses, 11 is 680 nm light and 1
A dichroic mirror that passes 00% and reflects 1.3 μm light 100%, 12 is a beam splitter, 13 is 1.3
The 1.3 μm light is not transmitted, but the 680 nm light is 10 μm.
This is a dichroic mirror that transmits 0%. 14 is λ /
Reference numeral 15 denotes a polarizing beam splitter, reference numeral 17 denotes a photosensor, and reference numeral 16 denotes a condenser lens for the photosensor 17, respectively. Reference numeral 18 denotes a differential amplifier circuit that differentially amplifies signals collected and detected according to the direction of deflection of the reflected light from the magneto-optical disk 1.

In the configuration of the magneto-optical recording / reproducing apparatus, laser beams having wavelengths of 680 nm and 1.3 .mu.m emitted from the recording / reproducing / heating semiconductor lasers 7 and 8 respectively have beam shaping lenses 9 and 10 and dichroic. The light is applied to the magneto-optical disk 1 via the mirror 11, the beam splitter 12, and the condenser lens 6. At this time, the condenser lens 6 is moved and driven in the focusing direction and the tracking direction by the control of the actuator 5 so that the laser beam is controlled so as to sequentially focus on the magneto-optical recording medium 3, and It is configured to track along the guide groove engraved on the surface. Further, the 1.3 μm light beam system for heating is configured to be smaller than the aperture diameter of the condenser lens 6, and the NA is smaller than that of 680 nm light which is condensed through all the apertures. It is like that. Therefore, as shown in FIG.
Since the heating spot of the m semiconductor laser 8 has a long wavelength and a small NA, it has a larger diameter than the recording / reproducing spot of the 680 nm wavelength semiconductor laser 7. As a result, it is possible to form a desired temperature gradient as shown in the lower part of the drawing in the recording / reproducing spot area on the surface of the moving medium 3.

The laser beam reflected by the magneto-optical disk 1 is converted by the beam splitter 12 into the polarized beam splitter 1.
The light path is changed in the direction of 5, and the dichroic mirror 1
3, via a λ / 2 plate 14 and a polarizing beam splitter 15, are collected by a condenser lens 16 on a photosensor 17 depending on the polarity of magnetization of the magneto-optical recording medium 3. Here, since the light having a wavelength of 1.3 μm cannot pass through the dichroic mirror 13, only the light having a wavelength of 680 nm will be used thereafter. Each photo sensor 17
Are differentially amplified by a differential amplifier circuit 18 to output a magneto-optical signal.

The controller 20 outputs a recording power, a recording signal, and the like using a recording signal to be recorded on a recording medium (not shown), the number of rotations of the magneto-optical disk 1, recording radius / recording sector information, and the like as input information. , The LD driver 19, the magnetic head driver 24, and the like. The LD driver 19 drives the semiconductor lasers 7 and 8, and in this embodiment, controls the desired recording power, reproduction power, and heating beam power. Reference numeral 23 denotes a magnetic head for applying a modulating magnetic field to a laser-irradiated portion of the magneto-optical disk 1 during a recording operation.

When recording a recording signal, the recording / reproducing semiconductor laser 7 uses the LD driver 19 to change the recording laser power to DC.
At the same time, the magnetic head 23 generates a magnetic field having a different polarity corresponding to a recording signal by a magnetic field modulation magnetic head driver 24. Also,
The magnetic head 23 moves in the radial direction of the magneto-optical disk 1 in conjunction with the optical heads 5 to 17, and records information by sequentially applying a magnetic field to a laser-irradiated portion of the magneto-optical recording medium 3 during recording. Has become. Further, as pointed out from the above problem, the signal processing circuit 22 shifts the movement timing between the domain wall movement in the recording mark enlargement direction and the domain wall movement in the reduction direction from the output of the differential amplifier 18, and the recording timing during reproduction is changed. This is a circuit for detecting the amount of correction to always be shorter than the time corresponding to the mark by a certain time. The recording phase adjusting circuit 21 adjusts the phase of the modulation magnetic field based on the output of the signal processing circuit 22 and drives the magnetic head 23 via the magnetic head driver 24, so that the time interval corresponding to the recording mark length can be adjusted. Correct for shortening.

The operation of the signal processing circuit 22 and the recording phase adjustment circuit 21 will be described below with reference to FIG. It is conceivable that the phase adjustment for correcting the position of the recording mark is determined in advance as a value unique to the apparatus. However, considering the combination of the magneto-optical recording / reproducing apparatus and the recording medium 3, the heat distribution and the heat distribution of the heating light beam are considered. It is desirable to use or provide a predetermined recording test area and execute it as a recording test in consideration of the variation in the thermal characteristics of the recording medium. For this purpose, the present embodiment provides a means for relatively easily executing the recording mark position correction. A single frequency recording mark sequence is employed as a recording pattern for a recording test.

FIG. 3A shows a case where the recording mark of this single frequency is recorded with a modulation magnetic field duty of 50%. In the drawing, the hatched portion of the recording mark and the hatched portion indicate a state in which the magnetization directions of the recording medium 3 are different, and in the present embodiment, the hatched portion is described as the recording mark. In this case, as shown in the figure, in the reproducing method using the domain wall motion, as pointed out in the above problem, the time interval corresponding to the recording mark is detected to be short. In the present embodiment, first, the reproduced signal is converted to a high-pass filter (hereinafter, referred to as a high-pass filter).
DC component is removed via HPF). Next, this DC
The peak level detection and the bottom level detection of the reproduced signal after the component removal are performed, and further, a center level that becomes a median value from the peak level and the bottom level is generated. Here, the center level when the reproduced signal has a duty ratio of 50% is set as a reference level and compared with the detected center level. In (1) in the figure, since the recording mark is recorded at a duty ratio of 50%, the time corresponding to the recording mark is detected for a short time, and a duty shift occurs in the reproduction signal. Are in a relationship of reference level <center level as shown in FIG.

When the phase of the modulation magnetic field is adjusted so that the recording mark is not long, as a result, when the recording mark position correction is excessively performed, as shown in (2), the time interval corresponding to the recording mark is reduced. Is detected for a long time, and a duty shift occurs in the reproduced signal. In this case, the detected center level and reference level are reversed from the case of the above (1), and the relation of reference level> center level is established as shown in the figure. When the phase of the modulation magnetic field is adjusted so that the duty of the reproduced signal becomes 50% as shown in (3), the center level and the reference level are set to the reference level =
Center level relationship.

As shown in FIG. 4, if the relationship between the difference between the reference level and the center level and the amount of phase correction of the recording mark is determined in advance, it is possible to correct the recording mark length by converting from the level difference voltage to the phase correction time. Thus, a signal having a duty ratio of 50%, that is, a desired reproduced signal can be obtained. In addition, when the variation due to the combination of the recording / reproducing apparatus and the recording medium is taken into consideration, the recording test and the level are set as initial values without relying only on the relationship between the difference between the reference level and the center level and the phase correction amount of the recording mark. It is more desirable to repeatedly feed back the difference detection and the phase correction to determine the final phase correction amount.

The method of detecting the amount of phase correction is not limited to this. For example, the phase difference between the rising edge of the reproduction signal and the reference clock, the reproduction signal, and the reference clock having the same frequency as the recording single frequency are used. There is also a method of detecting the phase difference between the falling edge of the reference clock and the reference clock, and the difference between these differences, and correcting the recording mark phase so as to eliminate the difference.

Based on the determination of the correction amount of the recording phase,
The recording / reproducing operation shown in FIG. 2 will be described. In the figure,
(A) is a recording signal, (b) is a recording power, (c) is a modulated magnetic field after recording compensation, (d) is a recording mark, and (e) is a reproduction signal. When recording a recording signal as shown in (a), the laser power of the semiconductor laser 7 is set to a predetermined recording power at the start of the recording operation. Further, a modulation magnetic field based on the recording signal is applied, and the modulation magnetic field (c) after the recording compensation in which the recording phase is corrected by the recording phase adjustment circuit 21 in FIG. . By these operations, in the process of cooling the recording medium, a recording mark row (d) indicated by a hatched portion is formed. The hatched portions represent magnetic domains having the direction of magnetization corresponding to the recording marks described in the present embodiment, and the shaded portions represent magnetic domains having the direction of magnetization opposite to this. As shown in the figure, the hatched portion corresponding to the recording mark is longer with respect to the time of the high level portion of the recording signal. By heating the recording mark recorded by the compensation operation with the heating beam and simultaneously reproducing the recording mark with the recording / reproducing beam, a reproduction signal (e) is obtained.
The reproduction signal (e) obtained here faithfully reproduces the recording signal (a), thereby reducing errors during reproduction and enabling information reproduction at a good error rate.

In the present embodiment, the phase adjustment is performed at both the front and rear ends of the recording mark. However, the present invention is not limited to this. The phase adjustment at the front end only, taking into account the adjustment amount at the rear end, and the adjustment amount at the front end are performed. It is also possible to adjust the phase only at the rear end with the addition. In particular, when a clock is generated from a recording mark sequence using a code capable of self-clocking and a reproduced signal is detected with this clock, the relative positional relationship between the recording mark and the non-recording mark is important, and Location
Since the time lag does not cause any particular problem, the phase of one end of the recording mark can be adjusted. However, in a sample servo method in which a clock is extracted from the recording medium surface, since the absolute phase relationship of the reproduction signal with respect to the clock is important, it is desirable to adjust the phase at both the front and rear ends of the recording mark.

[Embodiment 2] FIG. 5 shows a configuration diagram of a second embodiment of the present invention. FIG. 5 has a lot in common with FIG. 1, and a description of the same components will be omitted, and only different portions will be described. In the first embodiment, at the time of recording, the recording laser is irradiated with DC light. However, in the second embodiment, the recording laser power is pulsed at an integral multiple of the channel clock of the recording code. A configuration for irradiating a laser beam is adopted. In the second embodiment, irradiation is performed in a pulse shape at the channel frequency. In the first embodiment, the DC temperature of the recording medium becomes steady with respect to the light beam due to the irradiation of the light beam with the DC light, and the magnetization is performed at the switching phase of the modulation magnetic field in the magnetic domain forming temperature portion in the temperature region behind the light beam traveling direction. The direction was reversed and magnetic domains were formed. In the second embodiment, in the process in which the temperature of the recording medium rises and cools by the irradiation of the pulse light, the recording method is magnetized in the direction of the applied magnetic field to form magnetic domains. Does not directly determine the position and size of the magnetic domain, and the temperature rise portion of the recording medium greatly affects the position and phase of the magnetic domain formation. Therefore, in the second embodiment, the correction of the phase and size of the recording mark to be formed is performed by adjusting the power of the recording laser pulse, and by adjusting the phase of the laser pulse and further the phase of the modulation magnetic field. Do.

Based on such a basic concept, FIG.
Is a means for adjusting the power of the recording laser pulse and adjusting the phase of the laser pulse based on the signal obtained from the signal processing circuit 22. The modulation magnetic field recording phase adjusting circuit 21 is means for adjusting the phase of the modulation magnetic field in an auxiliary manner as necessary.

Signal processing circuit 22 and recording phase adjusting circuit 21
The operation will be described below with reference to FIG. It is conceivable that the phase adjustment for correcting the position of the recording mark is determined in advance as a value unique to the apparatus.However, when considering the combination of the magneto-optical recording / reproducing apparatus and the recording medium, the heat distribution and recording of the heating light beam are considered. It is desirable to use or provide a predetermined recording test area and execute it as a recording test in consideration of variations in the thermal characteristics of the medium. For this purpose, the present embodiment provides a means for relatively easily executing the recording mark position correction. A single frequency recording mark sequence is adopted as a recording mark recording pattern. FIG. 7A shows a case where the single frequency recording mark is recorded at a duty of 50%. That is, this is a case where the pulse-like recording power during recording is constant regardless of the direction of magnetization.
In the drawing, the hatched portion of the recording mark and the shaded portion indicate a state in which the direction of magnetization of the recording medium is different, and in the present embodiment, the hatched portion is described as a recording mark. In this case, as shown in the figure, in the reproducing method using the domain wall motion, as pointed out in the above problem, the time interval corresponding to the recording mark is detected to be short.

In this embodiment, first, this reproduced signal is converted into a DC signal through a high-pass filter (hereinafter, HPF).
Remove components. Next, a peak level and a bottom level of the reproduced signal after the DC component is removed are detected, and a center level corresponding to a median value is generated or calculated from the peak level and the bottom level. Here, the center level when the reproduced signal has a duty ratio of 50% is set as a reference level and compared with the detected center level. In (1) in the figure, the recording mark is recorded at a duty ratio of 50% because the value of the recording mark forming pulse power and the value of the non-recording mark forming pulse power are made equal. For this reason, as pointed out in the problem, the time interval corresponding to the recording mark is detected to be short, a duty shift occurs in the reproduced signal, and the detected center level and reference level are different from each other as shown in FIG. There is a level relationship. On the other hand, in order to increase the recording mark length, the recording power at the time of forming the recording mark is larger than the recording power at the time of forming the non-recording mark, as shown by the recording power (2) in the figure. If the power is adjusted and the recording mark position is corrected too much, as shown in FIG. 7 (2), a long time interval corresponding to the recording mark is detected and a duty shift occurs in the reproduced signal. In this case, the detected center level and the reference level are reversed from the case of the above (1), and the relation of reference level> center level is established as shown in the figure. And FIG.
As shown in the recording power of (3), when an appropriate recording power is adjusted so that the recording power at the time of forming a recording mark is larger than the recording power at the time of forming a non-recording mark, As shown in FIG.
0%, and the center level and the reference level have a relationship of reference level = center level as shown in the figure. As shown in FIG. 8, if the relationship between the difference between the reference level and the center level and the recording power difference between the recording mark and the non-recording mark is determined in advance, the recording power level difference voltage → the recording power correction amount. The recording mark length can be corrected by the conversion, and the duty ratio 50
% Signal, that is, a desired reproduction signal can be obtained.

In consideration of the variation due to the combination of the recording / reproducing apparatus and the recording medium, the correction amount is used as an initial value without relying only on the relationship between the difference between the reference level and the center level and the recording power correction amount of the recording mark. It is still more desirable to repeatedly feed back the recording test, the level difference detection, and the recording power correction to determine the final recording power correction amount.

The method of detecting the recording power correction amount is not limited to this. For example, the phase difference between the rising edge of the reproduction signal and the reference clock, the phase difference between the reproduction clock and the reference clock, using a reference clock having the same frequency as the recording single frequency and a phase comparator. There is also a method of detecting a phase difference between a falling edge of a signal and a reference clock, and a difference between these differences, and correcting the recording power so as to eliminate the difference.

The recording / reproducing operation shown in FIG. 6 based on the determination of the recording power correction amount will be described. FIG.
Among them, (a) is a recording signal, (b) is a recording laser irradiation sequence by the recording power after recording compensation determined based on the recording power correction method, (c) a modulation magnetic field, (d) is a recording mark, and (e). ) Is a reproduction signal. In the case of recording a recording signal as shown in FIG. 6A, a pulse irradiation (b) of a predetermined recording power determined by the recording power correcting means is performed as the laser power at the start of the recording operation. Further, a modulation magnetic field (c) based on the recording signal is applied. By these operations, a recording mark row (d) is formed in the process of cooling the recording medium heated by the irradiation of each recording pulse. For this reason, in the second embodiment, a recording mark string as shown in the drawing is obtained. The hatched portions represent magnetic domains having the direction of magnetization corresponding to the recording marks described in the present embodiment, and the shaded portions represent magnetic domains having the direction of magnetization opposite to this. Since the recording power is compensated for by the recording power correction, as shown in the figure, the hatched portion corresponding to the recording mark is longer with respect to the time of the high level portion of the recording signal.

By heating the recording mark recorded by this compensation operation with the heating beam and simultaneously reproducing the recording mark with the recording / reproducing beam, a reproduction signal (e) is obtained. The reproduction signal (e) obtained here faithfully reproduces the recording signal (a), thereby reducing errors during reproduction and enabling information reproduction at a good error rate.

In this embodiment, the recording mark length is adjusted only by adjusting the recording power. However, the present invention is not limited to this. The compensation for adjusting the recording mark length is also performed by adjusting the phase of the recording pulse. There can be a method.
Further, in the second embodiment, adjustment of the recording power value,
Alternatively, when the phase of the recording pulse is adjusted, it may be necessary to adjust the phase of the modulation magnetic field due to the necessity of applying a sufficient magnetic field in the process of forming the magnetic domain at the time of cooling the recording medium.

Regarding the length adjustment of the recording mark length,
It is not specified at either the front end or the rear end of the recording mark. In particular, when a clock is generated from a recording mark sequence using a code capable of self-clocking and a reproduced signal is detected with this clock, the relative positional relationship between the recording mark and the non-recording mark is important, and Since a typical positional / time shift does not cause any problem, it is sufficient that the time-series change of the deflection surface change detected from the recording mark is adjusted and compensated. However, in a sample servo system in which a clock is extracted from the recording medium surface, since the absolute phase relationship of the reproduction signal with respect to the clock is important, it is desirable to adjust the length at both the front and rear ends of the recording mark. .

[Embodiment 3] In Embodiments 1 and 2, the positional relationship of the reproducing beam spot with respect to the heating beam spot is as shown in FIG.
The reproducing beam spot shown as the recording / reproducing beam is arranged so as to be located ahead of the maximum temperature reaching point in the temperature rising region by the heating beam. In the present embodiment, as shown in FIG. The spot is located so as to be located behind the highest temperature reaching point of the temperature rising region by the heating beam and within the Ts isotherm. Accordingly, in the first and second embodiments, the change in the deflection surface due to the domain wall movement from the traveling direction and the front of the critical temperature reaching point is detected, whereas in the present embodiment, the critical temperature reaching point is reached. The change in the deflection surface due to the movement of the domain wall from the traveling direction / backward is detected. However, in this case, only the physical position of the reproduction beam changes, and the configuration and operation principle are the same as those of the first and second embodiments. FIG. 9 (3)
Shows the temperature distribution on the recording track with respect to the light beam, and reproduces the recording mark using a temperature gradient from the highest temperature to a low temperature.

Although not explicitly shown in each of the above embodiments, it is not necessary to be concerned with the recording tracks of the magneto-optical disk irrespective of the land and the groove, and also of the CLV (constant linear velocity) and CAV (constant angular velocity) modes. It can be applied to the case. Further, the magneto-optical recording medium 3 capable of reproducing a recording mark equal to or less than the diffraction limit of the light of the magneto-optical disk 1 shown in each of the above embodiments has a third magnetic layer of a perpendicular magnetization film,
At a temperature near the ambient temperature, the first magnetization layer of the perpendicular magnetization film having a smaller domain wall coercive force and a larger domain wall mobility than the third magnetic layer, and a lower Curie temperature than the first and third magnetization layers. In the case of a three-layer structure composed of the second magnetic layer, or when the Curie temperature between the first and second magnetic layers is higher than that of the second magnetic layer, lower than that of the first magnetic layer, and further closer to the second magnetic layer, the Curie temperature becomes higher. The fourth magnetization of the perpendicular magnetization film having a gradient of the Curie temperature in the film thickness direction such that the magnetic field wall coercive force is smaller than that of the third magnetization layer at a temperature equal to or higher than the Curie temperature of the second magnetization layer. There is a case of a four-layer configuration including additional layers, but a multi-layer configuration can also be applied.

In the above-described embodiment, an example has been described in which the medium temperature is raised by a heating laser. However, other means may be used as the temperature raising means, and the configuration of the optical head is not limited to the above example. It is also possible to configure the sensor and the condenser lens as one. Further, in the above embodiment, the example of the magneto-optical disk is shown as the magneto-optical recording medium. However, the present invention can be applied to a magneto-optical card which performs recording and reproduction at a constant recording and reproducing speed.

[0039]

According to the present invention, the magnetic wall of the recording mark of the reproducing layer is moved without changing the recording data of the recording layer by utilizing the temperature gradient of the medium temperature with respect to the magnetic domain of the medium due to the irradiation of the light beam. In the magneto-optical recording / reproducing method in which almost the entire area within the beam spot is made to have the same magnetization, the change in the deflection surface of the reflected light of the light beam is detected, and the recording mark is reproduced, the tip of the recording mark moves in the recording mark enlargement direction. In this case, there is a time difference between the start time when the recording mark moves and the movement start time when the trailing edge of the recording mark moves in the recording mark reducing direction. It is possible to solve the problem that the movement timing is shifted between when moving and the recording mark is always detected for a short period of time.

Further, the deflection surface can be detected at a desired phase, jitter can be suppressed, read errors can be reduced, and information can be recorded / reproduced at a low error rate. A method and apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment according to the present invention.

FIG. 2 is an operation timing chart of the first embodiment according to the present invention.

FIG. 3 is an operation timing chart of the first embodiment according to the present invention.

FIG. 4 is an operation principle diagram of the first embodiment according to the present invention.

FIG. 5 is a configuration diagram of a second embodiment according to the present invention.

FIG. 6 is an operation timing chart of the second embodiment according to the present invention.

FIG. 7 is an operation timing chart of the second embodiment according to the present invention.

FIG. 8 is an operation principle diagram of a second embodiment according to the present invention.

FIG. 9 is a principle diagram of a third embodiment according to the present invention.

FIG. 10 is a diagram showing a principle of a domain wall movement operation and a problem which are the basis of the present invention.

FIG. 11 is a timing operation diagram showing a conventional operation and a problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Substrate 3 Magneto-optical recording medium 4 Protective film 5 Actuator 6 Condensing lens 7 Recording / reproducing semiconductor laser 8 Heating semiconductor laser 9, 10 Beam shaping lens 11, 18 Dichroic mirror 12 Beam splitter 13 Dichroic mirror 14 λ / 2 Plate 15 Deflection beam splitter 16 Condenser lens 17 Photosensor 18 Differential amplifier circuit 21 Recording phase adjustment circuit 22 Signal processing circuit

Claims (13)

[Claims] 1. A method for irradiating a magneto-optical recording medium having a multilayer structure with a light beam and utilizing a temperature gradient of a temperature distribution of the medium at the irradiated portion without changing recording data on the recording layer to record marks on the reproducing layer. In the magneto-optical recording / reproducing method for moving the magnetic domain wall, detecting a change in the deflection surface of the reflected light of the light beam, and reproducing the recording mark, the magnetic domain wall moves in the recording mark enlargement direction and in the reduction direction. A difference between the domain wall movement start time and the light beam position generated at the time of movement is generated at the front end and the rear end of the recording mark by recording the position of the front end and / or the rear end of the recording mark in advance and recording. A magneto-optical recording / reproducing method, wherein a change in a deflection surface of reflected light is set to a desired phase. 2. The recording mark is recorded by a magnetic field modulation recording method of irradiating the light beam with DC light and modulating an applied magnetic field to form the recording mark.
2. The magneto-optical recording / reproducing method according to claim 1, wherein the correction of the position of the front end and / or the rear end of the recording mark is performed by changing the phase of a modulation magnetic field. 3. The recording mark is recorded by a pulse-assisted magnetic field modulation recording method of irradiating the light beam with a pulse and modulating an applied magnetic field to form the recording mark. 2. The magneto-optical recording / reproducing apparatus according to claim 1, wherein the correction of the position of the rear end is performed by changing the phase of the light beam power and / or the phase of the assist pulse light and / or the phase of the modulation magnetic field. Method. 4. The recording mark is recorded by a light modulation recording method of forming a recording mark by applying a constant magnetic field and modulating a light beam intensity, and a front end and / or a rear end of the recording mark. 2. The magneto-optical recording / reproducing method according to claim 1, wherein the correction of the position is performed by changing the phase of the light beam and / or the light beam power. 5. The magneto-optical recording / reproducing method according to claim 5, wherein the correction of the recording mark length is constant regardless of the recording mark length and is constant for all mark lengths. 6. The recording mark length correction amount is obtained by detecting a difference between a center level obtained from a peak level and a bottom level of a reproduction signal and a predetermined reference level. The magneto-optical recording / reproducing method according to any one of the above. 7. A laser beam is irradiated to a magneto-optical recording medium having a multi-layer structure, and a recording layer of a reproducing layer is recorded without changing recording data of the recording layer by utilizing a temperature gradient of a temperature distribution of the medium at the irradiated portion. A magneto-optical recording / reproducing apparatus that moves a domain wall of the recording mark, detects a change in the deflection surface of the reflected light of the light beam, and reproduces the previous recording mark. Recording means for recording a difference between a domain wall movement start time with respect to the position of the light beam generated during the movement and a position of the front end and / or the rear end of the recording mark in advance, and recording the front end and / or the recording mark; A magneto-optical recording / reproducing apparatus characterized in that the position of the rear end is corrected in advance and recording is performed so that the change in the deflection surface of the reflected light generated at the front end and the rear end of the recording mark has a desired phase. . 8. The magneto-optical recording / reproducing apparatus includes: a magnetic field modulation recording unit that irradiates the light beam with DC light to modulate a magnetic field to be applied to form the recording mark; and a unit that changes a phase of the modulated magnetic field. 8. The magneto-optical recording / reproducing apparatus according to claim 7, wherein the position of the front end and / or the rear end of the recording mark is corrected by means for changing a phase of a modulation magnetic field for modulating the magnetic field. . 9. A magneto-optical recording / reproducing apparatus comprising: a pulse-assisted magnetic field modulation recording unit that irradiates a pulse of the light beam and modulates an applied magnetic field to form the recording mark; and a phase adjustment unit for the assist pulse. A power adjusting means for the assist pulse, and a phase adjusting means for a modulation magnetic field for modulating the magnetic field. The position of the front end and / or the rear end of the recording mark is corrected by adjusting the phase and / or light of the assist pulse light. The magneto-optical recording / reproducing apparatus according to claim 7, wherein the step is performed by changing a beam power and / or a phase of a modulation magnetic field. 10. The magneto-optical recording / reproducing apparatus comprises a light modulation recording means for applying a constant magnetic field and modulating the intensity of the light beam to form the recording mark, wherein a front end and / or a rear end of the recording mark are provided. 8. The magneto-optical recording / reproducing apparatus according to claim 7, wherein the correction of the end position is performed by changing a phase and / or a light beam power of the light beam. 11. The recording mark length correction includes an inspection unit that detects a difference between a center level obtained from a peak level and a bottom level of a reproduction signal and a predetermined reference level, and based on an output of the detection unit, 11. The magneto-optical recording / reproducing apparatus according to claim 7, wherein the recording mark length is corrected. 12. A method for irradiating a magneto-optical recording medium with a light beam and using a temperature gradient of a medium temperature distribution with respect to a magnetic domain of a medium to move a domain wall of a magnetic domain mark of a reproducing layer without changing recording data of a recording layer; In the magneto-optical recording / reproducing apparatus for detecting a change in the deflection surface of the reflected light of the light beam and reproducing the previous recording mark, the magneto-optical recording / reproducing apparatus generates the magnetic recording wall when the domain wall moves in the enlargement direction and the domain wall moves in the reduction direction. The difference between the domain wall movement start time with respect to the light beam position is calculated from the recording means for recording the recording mark by correcting the position of the front end and / or the rear end of the recording mark in advance and the magneto-optical recording medium recorded by the recording means. A magneto-optical recording / reproducing apparatus, comprising: reproducing means for reproducing a recording mark. 13. A magneto-optical recording / reproducing apparatus according to claim 12, wherein said recording means for preliminarily correcting and recording said recording mark records and reproduces a recording mark having a duty ratio of 50% on a predetermined recording track. In this case, a recording phase adjusting means for setting a difference between a center level, which is a center value between a peak value and a bottom value of the reproduction signal, and a reference level, which is a center level when the reproduction signal has a duty ratio of 50%, to zero is included. A magneto-optical recording / reproducing apparatus characterized in that: