JPH0589548A - Magneto-optical recording method and magneto-optical recording device - Google Patents

Abstract

PURPOSE:To decrease jitter, to suppress inter-code interference and to attain a high S/N reproduction by correcting a driving signal of a magnetic head with respect to recording signal, in a recording of a magnetic field modulation system. CONSTITUTION:The recording signal including plural kinds of pluses different in length is corrected into a signal with a short pulse relatively shifted in the advancing direction or relatively lengthened by a compensation circuit 12 or relatively and an electromagnet 1 is driven in accordance with the corrected signal. Hence the magnetic field inverting a polarity in accordance with a signal can be impressed on a magnetic thin film 3 of the magneto-optical disk 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam to locally heat the magnetic thin film and at the same time reverses the polarity of the magnetic thin film according to a recording signal. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording method for recording information by applying a magnetic field that generates a magnetic field and a magneto-optical recording apparatus for implementing this method.

[0002]

2. Description of the Related Art Conventionally, as a method of recording information on a magneto-optical recording medium, a so-called magnetic field modulation method has been known. According to this method, information is recorded by scanning a medium with a light beam emitted continuously and applying a magnetic field whose polarity is reversed corresponding to a recording signal to a magnetic thin film. The portion of the magnetic thin film irradiated with the light beam is locally heated to the Curie temperature or higher, and the magnetization disappears. Then, the temperature of the portion through which the light beam has passed is lowered and it is magnetized in the same direction as the magnetic field applied at that time. In this way, a continuous pattern of magnetic domains (recording pits) having different magnetization directions, which indicate information, is formed on the magnetic thin film.

[0003]

However, in the above method, the direction of the magnetic field applied to the magnetic thin film is not instantaneously reversed, but a finite time (starting from switching) to completion (switching). Period). Therefore, when recording a recording signal containing multiple types of pulses with different lengths, when recording the shortest pulse, the next switching will start before the switching is completely completed, and it will be sufficient for the magnetic thin film. There was a risk that a magnetic field of different strength would not be applied. In this case, the pit recorded on the magnetic thin film corresponding to the short pulse is displaced from the original position where the tip position is to be recorded backward, and the pit width is larger than that of the pit corresponding to the longer pulse. Narrowed.

The deviation of the tip position of the pit as described above is
A more serious problem occurs in the recording of the mark length effective in increasing the recording density and increasing the capacity of the medium as compared with the recording between marks. This is because in the inter-mark recording, the center position of the pit indicates information, whereas in the mark length recording, the pit length, that is, the leading end position and the trailing end position of the pit represent information.

On the other hand, the magnetic field modulation method has the advantage that pits shorter than the spot diameter of the light beam irradiated on the magnetic thin film can be recorded, and the recording density can be increased to increase the capacity of the medium. .. On the other hand, when reading pits recorded at such a high density, there is a problem that the SN ratio of the reproduction signal is lowered due to intersymbol interference because there are a plurality of pits in the spot of the reproduction light beam. The problem of such intersymbol interference is usually solved by passing the reproduced signal through a transversal filter. However, if the pit recording position shift or the pit width decrease occurs as described above, the intersymbol interference becomes more complicated,
In some cases, the SN ratio of the reproduced signal cannot be sufficiently increased even by using a transversal filter or the like.

An example in which mark length recording is performed by the conventional method will be described below with reference to FIGS. 13 to 15. Here, FIG. 13 is a schematic diagram showing a configuration example of a conventional magneto-optical recording apparatus. 14 is a timing chart for explaining the operation of the apparatus of FIG. 13, and FIG. 15 is a diagram showing recorded pits and waveforms of signals reproduced from the pits.

In FIG. 13, a magneto-optical disk 2 comprises a magnetic thin film 3 capable of perpendicular magnetization formed on a substrate made of glass or resin. The magneto-optical disk 2 is rotated about an axis O-O 'by a spindle motor (not shown). The light beam 4 emitted from the semiconductor laser 7 is focused on the magnetic thin film 3 of the magneto-optical disk 2 by the collimator lens 6 and the objective lens 5 and applied.
Here, the spot diameter of the condensed light beam is about 1.4 μ.
It was m. The light beam 4 is adjusted so as to have a sufficient intensity to raise the temperature of the irradiated magnetic thin film to the Curie temperature of the thin film or higher. The semiconductor laser 7 is driven by a laser drive circuit 9.
Although the light beam 4 may be pulse-emitted in synchronization with the recording signal, it is assumed that it is emitted continuously in this example.

The objective lens 5 is provided with the magneto-optical disk 2 in between.
The electromagnet 1 is provided at a position facing the optical head portion 13 including
Are arranged. Then, the optical head unit 13 and the electromagnet 1
Are configured so that they can be moved in the radial direction of the disc 2 to a target position for recording while facing each other. The electromagnet 1 is formed by winding a coil around a magnetic core, and applies a magnetic field to the magnetic thin film 3. The recording data input from the terminal 11 is encoded by the encoding circuit 10, and the magnetic head drive circuit 8 inverts the polarity of the magnetic field applied from the electromagnet 1 to the magnetic thin film 3 in accordance with the encoded signal. Let

In the apparatus shown in FIG. 13, the terminal 11 shown in FIG.
When the data of the period T indicated by A is input to 4, the encoding circuit 10 converts it into the code indicated by B. here,
The conversion using the (2,7) code is shown as an example. The magnetic head drive circuit 8 supplies the drive current shown in C of FIG. 14 to the electromagnet 1 according to the output of the encoding circuit 10. The drive current signal C includes a plurality of types of pulses having different lengths, and the rising and falling edges of each pulse indicate the position and interval of the digit “1” of the code B. In this example, (2
7) Since the code is used, the number of digits "0" between the digits "1" is any of 2 to 7, and the pulse length is 0.5T in increments of 1.5T as the shortest. 4T
Up to 6 types. Also, the duration of these pulses is
A current I flowing in a predetermined direction is supplied to the electromagnet 1, and a current −I flowing in a direction opposite to the predetermined direction is supplied to the electromagnet 1 in other periods.

Due to the current supplied as described above, a magnetic field whose intensity changes as shown by D in FIG. 14 is applied to the magnetic thin film 3 from the electromagnet 1. The change in the magnetic field strength starts from the state in which the magnetic field of −H _a (for example, the downward magnetic field) is applied, and the polarity inversion starts at the rising timing of the pulse, and the switching period in which the magnetic field strength gradually changes is set. , And becomes a magnetic field of H _a (polarity upward magnetic field) whose polarity is completely reversed. Also, again the polarity inversion timing of the falling of the pulse is started, a state in which the magnetic field is applied -H _a place similar switching period. By applying such a magnetic field, the magnetization direction of the portion of the magnetic thin film 3 which is overheated by the irradiation of the light beam is reversed, and a recording pattern as shown by E in FIG. 14 is formed on the magnetic thin film 3. Here, P ₁ , P ₂ and P ₃ each represent a recording pit composed of magnetic domains having magnetization in a predetermined direction (upward in this example). The portions other than the recording pits have magnetization in the direction opposite to the magnetization direction of the recording pits (downward). Further, each pit has a crescent shape or a quiver shape in which the front end and the rear end are semicircular corresponding to the temperature distribution of the magnetic thin film due to the irradiation of the light beam.

However, in the conventional recording method as described above, the recording pit P ₂ corresponding to the shortest pulse, that is, the pulse of 1.5 T, is a pulse whose curvature at the leading end and the trailing end is another length. It is smaller than the pit corresponding to. For this reason, the tip position of the pit is shifted backward by .DELTA.L as compared with a pit corresponding to a pulse of another length, and the width of the pit is also reduced. This is considered to be due to the following reasons. That is, the temperature distribution of the magnetic thin film heated by the irradiation of the light beam has a concentric isotherm that is high at the center and gradually decreases toward the periphery. The shape of the recording pit follows the isotherm of a certain temperature determined by the strength of the applied magnetic field. Thus, the shape of the pits corresponding to the pulse of the 2T to 4T, the results in reflecting the isotherm temperature which magnetization is upward when applied magnetic field intensity H _a. However, in the case of a pulse having a length of 1.5 T, the reversal of the next magnetic field is started before the reversal of the magnetic field is completed as shown by D in FIG. 14, and the magnetic field strength does not reach the saturation value H _a .
Therefore, the threshold temperature for magnetizing the magnetic thin film upward is higher than that of the other pits, and the pits are formed along the isotherm having a smaller diameter. Therefore, 1.
The pits corresponding to the 5T pulse have a width smaller than that of the pits corresponding to the 2T to 4T pulses, with the tip retracted. As described above, if the tip position and width of the recorded pits change depending on the length of the pulse, it will be a great obstacle in accurately reproducing the recorded signal. This will be described with reference to FIG.

The upper part of FIG. 15 shows the pulses of the recording signal, and the central part of the figure shows the positions where the recording pits are formed when the pulses having different lengths are recorded at the same timing so that the pits overlap each other. It was drawn by. The lower part of FIG. 15 is a diagram showing the waveform of the reproduction signal output from the pit corresponding to each pulse length. In FIG. 15, reference numerals 21, 22 and 23 respectively denote a length of 1.5.
T, 2T and 2.5T pits are shown. Also, 31, 3
2, 33, 34, 35 and 36 each have a length of 1.5
The waveforms of reproduced signal outputs from pits of T, 2T, 2.5T, 3T, 3.5T and 4T are shown.

As can be seen from the diagram in the center of FIG. 15, even if the recording of each pulse is started at the same time t ₀ , 1.
The tip position of the 5T pit is shifted rearward as compared with the pits of other lengths. In the above example, the length of the pit recorded from the pulse of 1.5T was 0.78 μm, and the deviation of the tip position was 0.045 μm. The reproduced signal from the pits recorded in this way has a time shift (jitter) as shown in the lower part of FIG. 15, which causes a reproduction error and causes a decrease in reliability.

An object of the present invention is to provide a magneto-optical recording method and a magneto-optical recording apparatus which can solve the above-mentioned problems of the prior art and improve the SN ratio during reproduction.

[0015]

The above object of the present invention is to irradiate a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam so as to locally heat the magnetic thin film, and at the same time, a plurality of types having different lengths are used. In a magneto-optical recording method for recording information by applying a magnetic field whose polarity reverses at a timing corresponding to a recording signal including a pulse to a magnetic thin film, when recording a short pulse among the plurality of types of pulses, This is achieved by initiating the reversal of the magnetic field at a timing earlier than the defined reversal timing for long pulses.

Further, the magneto-optical recording apparatus of the present invention for carrying out the above method includes means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam, and a plurality of types of magnetic thin films having different lengths. Means for applying a magnetic field whose polarity is reversed at a timing corresponding to the recording signal including the pulse, and a compensation signal obtained by shifting the short pulse in the recording signal in a direction relatively preceding the longer pulse. And means for reversing the polarity of the magnetic field generated and applied to the magnetic thin film in accordance with this compensation signal.

According to another embodiment of the present invention, the above object of the present invention is to locally heat the magnetic thin film by irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam. In a magneto-optical recording method for recording information by applying a magnetic field whose polarity is inverted according to a recording signal including a plurality of types of pulses having different lengths to a magnetic thin film, a short pulse among the plurality of types of pulses is recorded. In doing so, the magnetic field in the predetermined direction is applied to the magnetic thin film for a longer period than the period corresponding to the length of the pulse, as compared with the case of recording a longer pulse.

A magneto-optical recording apparatus for carrying out the method according to another embodiment of the present invention includes means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam, and a length of the magnetic thin film. Means for applying a magnetic field whose polarity is inverted according to a recording signal containing a plurality of different types of pulses, and a compensation signal in which the length of a short pulse in the recording signal is relatively long with respect to a longer pulse. And means for reversing the polarity of the magnetic field generated and applied to the magnetic thin film in accordance with this compensation signal.

[0019]

1 is a schematic diagram showing the construction of an embodiment of a magneto-optical recording apparatus of the present invention. FIG. 2 is a timing chart for explaining the first embodiment of the magneto-optical recording method of the present invention using the apparatus of FIG. In FIG.
The same members as those in No. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

The apparatus of FIG. 1 differs from the apparatus of FIG. 13 only in that a compensating circuit 12 is provided between the encoding circuit 10 and the magnetic head drive circuit 8. This compensation circuit 1
2 is based on a signal including a plurality of types of pulses having different lengths corresponding to a code input from the encoding circuit 10, and a short pulse in the signal in a direction relatively preceding a longer pulse. Generate a shifted compensation signal. This compensation signal is input to the magnetic head drive circuit 8, and a current whose direction is inverted according to the compensation signal is supplied to the electromagnet 1. The operation of the apparatus shown in FIG. 1 will be described below with reference to FIG.

In the apparatus of FIG. 1, when the data of the period T shown by A in FIG.
0 is converted into a code as shown in B. here,
The conversion using the (2,7) code is shown as an example. Compensation circuit 12
Generates a compensation signal indicated by D in FIG. 2 according to the output of the encoding circuit 10. The compensation signal D is a signal obtained by shifting the signal before compensation shown in C of FIG. 2 by ΔT in the direction in which only the pulse of 1.5T precedes. That is, in the compensating signal, a pulse of length 1.5T is more than a fixed timing for a longer pulse of 2T to 4T.
ΔT The polarity reverses at an early timing. ΔT is 1.5
A deviation ΔL of the tip position of the pit corresponding to these pulses, which occurs when the T pulse and the 2T to 4T pulses are recorded at the same timing (in the present embodiment,
0.045 μm).

The compensation signal output from the compensation circuit 12 is
A current corresponding to the compensation signal is input to the magnetic head drive circuit 8 and a current flows through the electromagnet 1. That is, during the pulse period, the electric current I flowing in the predetermined direction is supplied to the electromagnet 1,
During the other period, the current −I flowing in the direction opposite to the predetermined direction is supplied to the electromagnet 1.

Due to the current supplied as described above, a magnetic field whose strength changes from the electromagnet 1 as shown by E in FIG. 2 is applied to the magnetic thin film 3. The change in the magnetic field strength is changed from the state where the −H _a magnetic field (for example, the downward magnetic field) is applied.
The polarity reversal starts at the rising edge of the pulse, and the magnetic field of H _a (the upward magnetic field) whose polarity is completely reversed with a switching period in which the magnetic field strength gradually changes.
Becomes Also, again the polarity inversion timing of the falling of the pulse is started, a state in which the magnetic field is applied -H _a place similar switching period. Here, 1.
For the pulse of 5T, the reversal of the polarity of the magnetic field is also started earlier by ΔT.

By applying the magnetic field as described above, the magnetization direction of the portion of the magnetic thin film 3 which is overheated by the irradiation of the light beam is reversed, and a recording pattern such as F in FIG. 2 is formed on the magnetic thin film 3. To be done. Here, P ₁ , P ₂ and P ₃ each represent a recording pit composed of magnetic domains having magnetization in a predetermined direction (upward in this example). The portions other than the recording pits have magnetization in the direction opposite to the magnetization direction of the recording pits (downward). In the present embodiment, the reversal of the polarity of the magnetic field is started earlier by ΔT, so the recording position of the pit of 1.5T shifts to the front with respect to the other pits, and the deviation ΔL of the tip position as in the conventional case occurs. Does not happen. This will be described with reference to FIG.

The upper part of FIG. 3 shows the pulses of the recording signal, and the central part of the figure shows the positions where the recording pits are formed when recording pulses of different lengths at the same timing. It was drawn by. The lower part of FIG. 3 is a diagram showing the waveform of the reproduction signal output from the pit corresponding to each pulse length. In FIG. 3, reference numerals 21, 22 and 23 denote lengths of 1.5T and 2T, respectively.
And a pit of 2.5T is shown. Also, 31, 32, 3
3, 34, 35 and 36 are lengths 1.5T and 2 respectively
The waveforms of the reproduced signal output from the pits of T, 2.5T, 3T, 3.5T and 4T are shown.

As can be seen from the upper diagram of FIG. 3, in this embodiment, the reversal of magnetization when recording a pit of 1.5 T
It starts at time t ₁ which is earlier than the start timing t ₀ of other pulses by ΔT. Therefore, as shown in the center diagram of FIG. 3, the pit of 1.5T is recorded without shifting the tip position from the pits of 2T and 2.5T. Therefore, the reproduced signal from the pit thus recorded has almost no time shift (jitter) as shown in the lower part of FIG. 3, and it is possible to prevent the occurrence of a reproducing error.

FIG. 4 is a timing chart for explaining the second embodiment of the magneto-optical recording method of the present invention. The method of the second embodiment can also be implemented by the device having the configuration shown in FIG.
However, based on the recording signal corresponding to the code sent from the encoding circuit 10, the compensating circuit 12 makes the length of the short pulse in this recording signal relatively long with respect to the longer pulse. Is configured to generate.

In the apparatus of FIG. 1, when the data of the period T shown by A in FIG.
0 is converted into a code as shown in B. here,
The conversion using the (2,7) code is shown as an example. Compensation circuit 12
Generates a compensation signal indicated by D in FIG. 4 according to the output of the encoding circuit 10. This compensation signal D has only a pulse length of 1.5T compared with the signal before compensation shown in C of FIG.
It is a signal that has been lengthened.

The compensation signal output from the compensation circuit 12 is
A current corresponding to the compensation signal is input to the magnetic head drive circuit 8 and a current flows through the electromagnet 1. That is, during the pulse period, the electric current I flowing in the predetermined direction is supplied to the electromagnet 1,
During the other period, the current −I flowing in the direction opposite to the predetermined direction is supplied to the electromagnet 1.

Due to the current supplied as described above, a magnetic field whose intensity changes as shown by E in FIG. 4 is applied to the magnetic thin film 3 from the electromagnet 1. The change in the magnetic field strength is changed from the state where the −H _a magnetic field (for example, the downward magnetic field) is applied.
The polarity reversal starts at the rising edge of the pulse, and the magnetic field of H _a (the upward magnetic field) whose polarity is completely reversed with a switching period in which the magnetic field strength gradually changes.
Becomes Also, again the polarity inversion timing of the falling of the pulse is started, a state in which the magnetic field is applied -H _a place similar switching period. Here, 1.
For the 5T pulse, the downward reversal of the magnetic field is slower than for the other pulses, and the upward magnetic field is applied to the magnetic thin film for a longer period.

By applying the magnetic field as described above, the magnetization direction of the portion of the magnetic thin film 3 which is overheated by the irradiation of the light beam is reversed, and a recording pattern such as F in FIG. 4 is formed on the magnetic thin film 3. To be done. Here, P ₁ , P ₂ and P ₃ each represent a recording pit composed of magnetic domains having magnetization in a predetermined direction (upward in this example). The portions other than the recording pits have magnetization in the direction opposite to the magnetization direction of the recording pits (downward). In the present embodiment, when recording a 1.5T pit, the upward magnetic field is applied relatively longer than other pits, so that the curvature of the leading end and the trailing end of the 1.5T pit is small. The curvature of other pits approaches, and the displacement of the tip position is reduced to ΔL ′ compared to the conventional example. Also, 1.5T
There is almost no difference between the width of the pit of 2T and the width of the pit of 2T to 4T. This will be described with reference to FIG.

The upper part of FIG. 5 shows the pulses of the recording signal, and the central part of the figure shows the positions where the recording pits are formed when the pulses having different lengths are recorded at the same timing. It was drawn by. The lower part of FIG. 5 is a diagram showing the waveform of the reproduction signal output from the pit corresponding to each pulse length. 5, the same parts as those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

As can be seen from the upper diagram of FIG. 5, in this embodiment, the reversal of the magnetization at the rear end of the 1.5T pit is started with a delay of 7% from the other pulses. Therefore, as shown in the center diagram of FIG. 5, 1.5T pits, 2T and 2.
There is almost no difference in the tip position from the 5T pit. Therefore, in the reproduced signal from the pits recorded in this way, the jitter is improved as compared with the conventional example as shown in the lower part of FIG. 5, and the occurrence of the reproduction error can be prevented.

The optimum value of the length of the short pulse varies depending on the frequency of the recording signal, the relative speed of the light beam and the medium, and for example, for a light beam having a spot diameter of 1.4 μm, the shortest is 0.78 μm. In the case of recording the pit No. 1, a sufficient effect was obtained by making the length several% to 10% longer.

The effects of the first and second embodiments described above were confirmed by experiments. FIG. 6, FIG. 7 and FIG. 8 are diagrams showing eye patterns of reproduced signals when reproducing pits recorded by the conventional method, the method of the first embodiment and the method of the second embodiment, respectively. In these figures, the horizontal axis represents time and the vertical axis represents reproduced signal output. 7 and 8
6 has a more open eye pattern than that of FIG. 6, and when recorded by the method of the first and second embodiments of the present invention, more accurate pits can be recorded than in the conventional method, which is a main cause of reproduction error. It can be seen that some jitter is reduced and intersymbol interference is suppressed.

FIGS. 9, 10 and 11 respectively show histograms of pit lengths when pits recorded by the conventional method, the method of the first embodiment and the method of the second embodiment are reproduced. In these figures, the horizontal axis shows the detected pit length and the vertical axis shows the frequency. The broken lines in the figure are accurate pit lengths of 1.5T, 2T, 2.5T, 3T,
Shows 3.5T and 4T. From these figures, when the method of the first or second embodiment of the present invention is used, the detected pit length is concentrated in a range close to the correct pit, and pits of different lengths are misread. It can be seen that the error can be reduced.

The following Table 1, Table 2 and Table 3 are obtained by analyzing the results of FIGS. 9, 10 and 11, respectively. From these tables, it can be seen that the present invention enables reproduction with a high SN ratio.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3] FIG. 12 is a timing chart for explaining the third embodiment of the magneto-optical recording method of the present invention. This embodiment is a combination of the above-mentioned first and second embodiments, and when recording the shortest pulse, starts the reversal of the magnetic field at a timing earlier than the timing of the reversal of the magnetic field set for a longer pulse. In addition, when recording the shortest pulse, a magnetic field in a predetermined direction is applied to the magnetic thin film for a period longer than the period corresponding to the length of the pulse, as compared with the case of recording a longer pulse. Is. The method of this embodiment can also be carried out by the apparatus having the configuration shown in FIG. However, the compensation circuit 12
Is the shortest pulse length in the recording signal based on the recording signal corresponding to the code sent from the encoding circuit 10.
It is configured to output a compensation signal that is relatively long for a longer pulse and that shifts the shortest pulse in a direction relatively ahead of the longer pulse.

In the apparatus shown in FIG. 1, from the terminal 11 to FIG.
When the data of the cycle T indicated by A is input, the encoding circuit 10 converts it into the code indicated by B. here,
The conversion using the (2,7) code is shown as an example. Compensation circuit 12
Generates a compensation signal indicated by D in FIG. 12 according to the output of the encoding circuit 10. The compensation signal D is shifted by ΔT ′ in the direction in which only the 1.5T pulse precedes the signal before compensation shown in C of FIG. 12, and the 1.5T pulse length is increased by 7%. It is a signal. That is, in the compensation signal, the 1.5T-long pulse is Δ times shorter than the timing defined for the longer 2T-4T pulse.
T'At the early timing, the reversal of the polarity of the magnetic field is started from downward to upward. Further, the downward magnetic field reversal starts 1.5 × 1.07 T after the upward magnetic field reversal starts. ΔT 'is 1.5 × 1.07T pulse and 2
Deviation Δ of the tip position of the pit shown in FIG. 4, which occurs when the pulses of T to 4T are recorded at the same timing
It is a time difference corresponding to L '. The compensation signal output from the compensation circuit 12 is input to the magnetic head drive circuit 8, and a current corresponding to this compensation signal flows through the electromagnet 1. That is, the electric current I flowing in the predetermined direction is supplied to the electromagnet 1 during the pulse period, and the current −I flowing in the opposite direction to the predetermined direction is supplied to the electromagnet 1 during the other periods.

Due to the current supplied as described above, a magnetic field whose intensity changes as shown by E in FIG. 12 is applied to the magnetic thin film 3 from the electromagnet 1. Change in magnetic field strength, from a state where the magnetic field of -H _a (e.g. downward magnetic field) is applied, the inversion of the polarity is started at the rising edge of the pulse of the compensation signal, gradually switching period in which the magnetic field intensity varies Then, the magnetic field of H _a (upward magnetic field) whose polarity is completely inverted is obtained. The inverting again the polarity at the timing of the falling of the pulse of the compensation signal is started, a state in which the magnetic field is applied -H _a place similar switching period.

By applying the magnetic field as described above, the magnetization direction of the portion of the magnetic thin film 3 which is overheated by the irradiation of the light beam is reversed, and a recording pattern as shown by F in FIG. 12 is formed on the magnetic thin film 3. To be done. Here, P ₁ , P ₂ and P ₃ each represent a recording pit composed of magnetic domains having magnetization in a predetermined direction (upward in this example). The portions other than the recording pits have magnetization in the direction opposite to the magnetization direction of the recording pits (downward). In this embodiment, the reversal of the polarity of the magnetic field is ΔT '.
Since it started early, 1.5T against other pits
The recording position of the pit P ₂ is shifted forward, and the tip position is not displaced. Further, the width of the pit P ₂ is almost the same as that of the other pits. Therefore, the information recorded by the method of this embodiment can be read with a high SN ratio.

The present invention can be applied in various ways other than the above-described embodiments. For example, in the embodiment, only the shortest pulse is corrected, but when jitter or the like occurs between two types of pulses having different lengths, the present invention can be applied to all of these pulses. Further, the present invention can obtain the same effect in recording a signal encoded by a method other than the (2,7) code. Furthermore, the present invention is not limited to mark length recording, but may be applied to inter-mark recording.

[0045]

As described above, according to the magneto-optical recording method and apparatus of the present invention, the short pulse in the recording signal is shifted in the forward direction or the length of the short pulse is lengthened. And the SN ratio of the reproduced signal is improved. At the same time, the present invention has the effect of suppressing intersymbol interference. As a result, the present invention enables higher density information recording.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a magneto-optical recording apparatus of the present invention.

FIG. 2 is a timing chart diagram for explaining the first embodiment of the magneto-optical recording method of the present invention.

FIG. 3 is a schematic diagram showing pits recorded by the method of the first embodiment and waveforms of reproduction signals from these pits.

FIG. 4 is a timing chart diagram for explaining a second embodiment of the magneto-optical recording method of the present invention.

FIG. 5 is a schematic diagram showing pits recorded by the method of the second embodiment and waveforms of reproduction signals from these pits.

FIG. 6 is a diagram showing an eye pattern of a reproduction signal of information recorded by a conventional method.

FIG. 7 is a diagram showing an eye pattern of a reproduction signal of information recorded by the method of the first embodiment of the present invention.

FIG. 8 is a diagram showing an eye pattern of a reproduction signal of information recorded by the method of the second embodiment of the present invention.

FIG. 9 is a histogram of pit lengths read from information recorded by a conventional method.

FIG. 10 is a histogram of pit length read from information recorded by the method of the first embodiment of the present invention.

FIG. 11 is a histogram of pit lengths read from information recorded by the method of the second embodiment of the present invention.

FIG. 12 is a timing chart diagram for explaining the third embodiment of the magneto-optical recording method of the present invention.

FIG. 13 is a schematic configuration diagram showing an example of a conventional magneto-optical recording apparatus.

FIG. 14 is a timing chart diagram for explaining a conventional magneto-optical recording method.

FIG. 15 is a schematic diagram showing pits recorded by a conventional method and waveforms of reproduction signals from these pits.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnet 2 Magneto-optical disk 3 Magnetic thin film 4 Light beam 5 Objective lens 6 Collimator lens 7 Semiconductor laser 8 Magnetic head drive circuit 9 Laser drive circuit 10 Encoding circuit 11 Input terminal 12 Compensation circuit 13 Optical head section

Claims (7)

[Claims] 1. A magneto-optical recording medium having a magnetic thin film as a recording layer is irradiated with a light beam to locally heat the magnetic thin film, and the polarity is adjusted at a timing corresponding to a recording signal containing a plurality of types of pulses having different lengths. In a magneto-optical recording method for recording information by applying a reversing magnetic field to a magnetic thin film, when recording a short pulse of the plurality of types of pulses, a magnetic field reversal determined for a longer pulse A magneto-optical recording method characterized by starting reversal of a magnetic field at a timing earlier than the timing. 2. The time difference between the timing of starting the reversal of the magnetic field for the short pulse and the timing of starting the reversal of the magnetic field for the longer pulse is such that the magnetic field of the short pulse and the longer pulse are the same. 2. The magneto-optical recording method according to claim 1, which is a time difference corresponding to the deviation of the tip positions of the pits recorded on the magnetic thin film corresponding to each pulse, which occurs when the inversion of is started. 3. A means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam, and a polarity reversal at a timing corresponding to a recording signal containing a plurality of types of pulses of different lengths on the magnetic thin film. In a magneto-optical recording device comprising a means for applying a magnetic field, means for generating a compensation signal by shifting a short pulse in the recording signal in a direction relatively ahead of a longer pulse is provided, and the compensation signal is provided. A magneto-optical recording device characterized by inverting the polarity of a magnetic field applied to the magnetic thin film according to a signal. 4. A magneto-optical recording medium having a magnetic thin film as a recording layer is irradiated with a light beam to locally heat the magnetic thin film, and the polarity is inverted in response to a recording signal containing a plurality of types of pulses having different lengths. In the magneto-optical recording method for recording information by applying a magnetic field to the magnetic thin film, when the short pulse is recorded among the plurality of types of pulses, the pulse length is longer than that when the longer pulse is recorded. A magnetic-optical recording method characterized in that a magnetic field in a predetermined direction is applied to the magnetic thin film for a period longer than a period corresponding to the length. 5. A means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam, and a magnetic field whose polarity is inverted in response to a recording signal containing a plurality of types of pulses having different lengths. In the magneto-optical recording device, which comprises means for applying, a means for generating a compensation signal in which the length of the short pulse in the recording signal is made relatively longer than that of the longer pulse is provided, and the compensating signal is used in accordance with the compensation signal. A magneto-optical recording device characterized by reversing the polarity of a magnetic field applied to a magnetic thin film. 6. A magneto-optical recording medium having a magnetic thin film as a recording layer is irradiated with a light beam to locally heat the magnetic thin film, and the polarity is adjusted at a timing corresponding to a recording signal containing a plurality of types of pulses having different lengths. In a magneto-optical recording method for recording information by applying a reversing magnetic field to a magnetic thin film, when recording a short pulse of the plurality of types of pulses, a magnetic field reversal determined for a longer pulse When the reversal of the magnetic field is started at a timing earlier than the timing and the short pulse is recorded, the magnetic field in the predetermined direction is longer than the period corresponding to the length of the pulse as compared with the case of recording the longer pulse. A magneto-optical recording method characterized by being applied to a magnetic thin film. 7. A means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam, and a magnetic field for reversing the polarity according to a recording signal containing a plurality of types of pulses of different lengths. In a magneto-optical recording device comprising a means for applying, a short pulse in the recording signal is shifted in a direction relatively ahead of a longer pulse, and
A means for generating a compensation signal is provided, in which the length of the short pulse is made relatively longer than that of the longer pulse, and the polarity of the magnetic field applied to the magnetic thin film is inverted according to the compensation signal. Magneto-optical recording device.