JP3015166B2 - Magneto-optical recording method and magneto-optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating 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 to invert the polarity of the magnetic thin film according to a recording signal. The present invention relates to a magneto-optical recording method for recording information by applying a changing magnetic field, and a magneto-optical recording device for implementing the method.

[0002]

2. Description of the Related Art Conventionally, as a method for recording information on a magneto-optical recording medium, a method called a so-called magnetic field modulation method is known. According to this method, information is recorded by scanning a medium with a continuously emitted light beam and applying a magnetic field whose polarity is reversed to a magnetic thin film in accordance with a recording signal. 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 decreases, and the portion 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 indicating information is formed on the magnetic thin film.

[0003]

However, in the above-mentioned method, the direction of the magnetic field applied to the magnetic thin film does not always reverse instantaneously, but a finite time (switching) from the start of the reversal to the completion. Period). For this reason, when recording a recording signal including a plurality of types of pulses having different lengths, when recording the shortest pulse, the next switching is started before the switching is completely completed, so that the magnetic thin film is not enough. There was a possibility that a magnetic field having a high strength was not applied. In this case, the pit recorded on the magnetic thin film corresponding to the short pulse has its tip position shifted backward from the original position to be recorded, and the pit width is larger than that of the pit corresponding to the longer pulse. It became narrow.

[0004] The displacement of the tip position of the pit as described above is as follows.
A more serious problem arises in mark length recording, which is effective in increasing the recording density and increasing the capacity of the medium as compared with inter-mark recording. This is because in the inter-mark recording, the center position of the pit indicates information, whereas in the mark length recording, the length of the pit, that is, the leading end position and the trailing end position of the pit indicate information.

On the other hand, the magnetic field modulation method has an advantage that a pit 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, a plurality of pits are present in the spot of the reproduction light beam, so that there has been a problem that the SN ratio of the reproduction signal is reduced due to intersymbol interference. Such a problem of intersymbol interference is usually solved by passing a reproduced signal through a transversal filter. However, when the pit recording position shifts and the pit width decrease as described above, the intersymbol interference becomes more complicated,
In some cases, the SN ratio of the reproduced signal cannot be sufficiently increased by means such as a transversal filter.

An example in which mark length recording is performed by a conventional method will be described below with reference to FIGS. Here, FIG. 13 is a schematic diagram showing a configuration example of a conventional magneto-optical recording device. FIG. 14 is a timing chart for explaining the operation of the apparatus shown in 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 is formed by forming a perpendicularly magnetizable magnetic thin film 3 on a substrate made of glass or resin. The magneto-optical disk 2 is rotated about an axis OO 'by a spindle motor (not shown). A light beam 4 emitted from a semiconductor laser 7 is condensed by a collimator lens 6 and an objective lens 5 and applied to the magnetic thin film 3 of the magneto-optical disk 2.
Here, the spot diameter of the focused light beam is about 1.4 μ
m. The light beam 4 is adjusted so as to have sufficient intensity to raise the temperature of the irradiated portion of the magnetic thin film above the Curie temperature of the thin film. The semiconductor laser 7 is driven by a laser drive circuit 9.
The light beam 4 may be emitted in pulses in synchronization with the recording signal, but is assumed to be emitted continuously in this example.

The objective lens 5 is sandwiched between the magneto-optical disk 2
The electromagnet 1 is located at a position facing the optical head 13 including
Is arranged. Then, the optical head unit 13 and the electromagnet 1
Are configured to be able to move in the radial direction of the disk 2 to a recording target location 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 driving circuit 8 inverts the polarity of the magnetic field applied from the electromagnet 1 to the magnetic thin film 3 according to the encoded signal. Let it.

In the device shown in FIG.
When the data of period T indicated by A is input to 4, the encoding circuit 10 converts the data into a code as indicated by B. here,
The conversion by the (2, 7) code has been described as an example. The magnetic head drive circuit 8 supplies a drive current shown in FIG. 14C 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 rise and fall of each pulse indicate the position and interval of the digit “1” of the code B. In this example, (2,
7) Since a code is used, the number of digits "0" between digits "1" is any of 2 to 7, and the pulse length is in increments of 0.5T with 1.5T being the shortest. 4T
Up to six 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 during other periods.

[0010] By the current supplied as described above, a magnetic field whose intensity changes as shown in FIG. 14D 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, is started inverted polarity at the rise timing of the pulse, and gradually put switching period in which the magnetic field intensity varies , completely turned magnetic field inverted H _a polarity (upward magnetic field). The polarity inversion is started again at the timing of the falling edge of the pulse, and _a magnetic field of -Ha is applied after _a similar switching period. By applying such a magnetic field, the magnetization direction of the portion of the magnetic thin film 3 that has been heated by the light beam irradiation is inverted, and a recording pattern as shown in FIG. Here, P ₁ , P ₂ and P ₃ indicate recording pits each composed of a magnetic domain having a magnetization in a predetermined direction (upward in this example). The portion other than the recording pit has a magnetization in a direction (downward) opposite to the magnetization direction of the recording pit. Each pit has a crescent or arrow feather shape with a semicircular tip and a rear end corresponding to the temperature distribution of the magnetic thin film by light beam irradiation.

[0011] However, in the conventional recording method as described above, the shortest pulse, i.e. the recording pit P ₂ corresponding to the pulse of 1.5T in pulse curvature of the tip and rear end of the other length It is smaller than the corresponding pit. For this reason, the leading end position of the pit is shifted rearward by ΔL as compared with the pit corresponding to the 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 light beam irradiation has a concentric isotherm, which is high at the center and gradually decreases toward the periphery. Then, the shape of the recording pit follows an isothermal line at a certain temperature determined by the intensity 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 pulse length 1.5T, as shown in D in FIG. 14, the inversion of the next magnetic field will be started within the inversion of the magnetic field is not completed, the magnetic field intensity 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 pits are formed along isotherms having smaller diameters. Therefore, 1.
The pit corresponding to the pulse of 5T has a leading end retreated and a width smaller than that of the pit corresponding to the pulse of 2T to 4T. As described above, a change in the tip position and width of a pit to be recorded depending on the length of a pulse poses a major obstacle in accurately reproducing a signal recorded in such a manner. This will be described with reference to FIG.

The upper part of FIG. 15 shows the recording signal pulses, and the middle part shows the positions where the recording pits are formed when the pulses having different lengths are recorded at the same timing. It was drawn. The lower part of FIG. 15 is a diagram showing a waveform of a reproduced signal output from a pit corresponding to each pulse length. In FIG. 15, symbols 21, 22, and 23 each have 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 waveform of the reproduced signal output from pits of T, 2T, 2.5T, 3T, 3.5T and 4T is shown.

As can be seen from the center diagram of FIG. 15, even if the recording of each pulse is started at the same time t ₀ , it is possible that:
The tip position of the 5T pit is shifted rearward as compared with pits of other lengths. In the above-described example, the length of the pit recorded from the 1.5T pulse was 0.78 μm, and the displacement of the tip position was 0.045 μm. The reproduced signal from the pits recorded in this way has a time lag (jitter) as shown in the lower part of FIG. 15, causing a reproduction error and reducing 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 can improve the SN ratio during reproduction.

[0015]

SUMMARY OF THE INVENTION The 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 to locally heat the magnetic thin film and to use a plurality of types of magnetic thin films having different lengths. In a magneto-optical recording method of recording information by applying a magnetic field whose polarity is inverted to a magnetic thin film at a timing corresponding to a recording signal including a pulse, when recording a short pulse of the plurality of types of pulses, This is achieved by starting the reversal of the magnetic field at a timing earlier than the timing of the magnetic field reversal determined for a long pulse.

Further, the magneto-optical recording apparatus of the present invention for implementing the above-mentioned method comprises: means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam; Means for applying a magnetic field whose polarity is inverted at a timing corresponding to a recording signal including a pulse, and a compensation signal obtained by shifting a short pulse in the recording signal in a direction relatively preceding a longer pulse. Means for inverting the polarity of the magnetic field generated and applied to the magnetic thin film according to the compensation signal.

According to another embodiment of the present invention, the 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 to locally heat the magnetic thin film, In a magneto-optical recording method for recording information by applying a magnetic field whose polarity is reversed in accordance with a recording signal including a plurality of types of pulses having different lengths, a short pulse among the plurality of types of pulses is recorded. This is achieved by applying a magnetic field in a predetermined direction to the magnetic thin film longer than a 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 a method according to another embodiment of the present invention comprises: a means for irradiating a magneto-optical recording medium having a magnetic thin film as a recording layer with a light beam; Means for applying a magnetic field whose polarity is inverted in accordance with a recording signal including 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 longer than that of a longer pulse. Means for inverting the polarity of the magnetic field generated and applied to the magnetic thin film according to the compensation signal.

[0019]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a magneto-optical recording apparatus according to the present invention. FIG. 2 is a timing chart for explaining a first embodiment of the magneto-optical recording method of the present invention using the apparatus of FIG. In FIG. 1, FIG.
The same reference numerals are given to the same members as 3, and the detailed description is omitted.

The apparatus shown in FIG. 1 differs from the apparatus shown in FIG. 13 only in that a compensation circuit 12 is provided between an encoding circuit 10 and a magnetic head driving circuit 8. This compensation circuit 1
2 is based on a signal including a plurality of types of pulses having different lengths corresponding to the code input from the encoding circuit 10, in which a short pulse in the signal is moved 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 reversed according to the compensation signal is supplied to the electromagnet 1. Hereinafter, the operation of the apparatus of FIG. 1 will be described with reference to FIG.

In the apparatus shown in FIG. 1, when data having a period T indicated by A in FIG.
0 is converted into a code as shown in B. here,
The conversion by the (2, 7) code has been described as an example. Compensation circuit 12
Generates a compensation signal shown in FIG. 2D according to the output of the encoding circuit 10. This compensation signal D is a signal which is shifted by ΔT in a direction in which only the pulse of 1.5T precedes the signal before compensation shown in C of FIG. That is, in the compensation signal, the pulse of 1.5T in length is longer than the timing determined for the longer pulse of 2T to 4T.
The polarity is reversed at an early timing ΔT. ΔT is 1.5
The shift ΔL of the tip position of the pit corresponding to the T pulse and the 2T to 4T pulses recorded at the same timing (in the present embodiment,
0.045 μm).

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

With the current supplied as described above, a magnetic field whose strength changes as shown in FIG. 2E 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,
Polarity reversal at the rising edge of the pulse is started, at a gradual switching period in which the magnetic field intensity changes completely the inverted H _a polarity magnetic field (upward magnetic field)
Becomes The polarity inversion is started again at the timing of the falling edge of the pulse, and _a magnetic field of -Ha is applied after _a similar switching period. Here, 1.
For a 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 that has been heated by the light beam irradiation is reversed, and a recording pattern as shown in FIG. Is done. Here, P ₁ , P ₂ and P ₃ indicate recording pits each composed of a magnetic domain having a magnetization in a predetermined direction (upward in this example). The portion other than the recording pit has a magnetization in a direction (downward) opposite to the magnetization direction of the recording pit. In this embodiment, since the reversal of the polarity of the magnetic field is started by ΔT earlier, the recording position of the pit of 1.5T is shifted forward with respect to the other pits, and the shift ΔL of the tip position as in the related art is reduced. Does not occur. This will be described with reference to FIG.

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

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

FIG. 4 is a timing chart for explaining a second embodiment of the magneto-optical recording method according to the present invention. The method of the second embodiment can also be performed by the apparatus having the configuration shown in FIG.
However, the compensating circuit 12 is based on the recording signal corresponding to the code sent from the encoding circuit 10 and makes the length of the short pulse in the recording signal relatively longer than that of the longer pulse. Is generated.

In the apparatus shown in FIG. 1, when data having a period T indicated by A in FIG.
0 is converted into a code as shown in B. here,
The conversion by the (2, 7) code has been described as an example. Compensation circuit 12
Generates a compensation signal shown in FIG. 4D according to the output of the encoding circuit 10. This compensation signal D is different from the signal before compensation shown in FIG.
This is a signal that has been lengthened by%.

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

By the current supplied as described above, a magnetic field whose strength changes as shown in FIG. 4E 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,
Polarity reversal at the rising edge of the pulse is started, at a gradual switching period in which the magnetic field intensity changes completely the inverted H _a polarity magnetic field (upward magnetic field)
Becomes The polarity inversion is started again at the timing of the falling edge of the pulse, and _a magnetic field of -Ha is applied after _a similar switching period. Here, 1.
For the 5T pulse, the reversal of the magnetic field in the downward direction is slower than in the other pulses, and the upward magnetic field is applied to the magnetic thin film for that much longer.

By applying the magnetic field as described above, the magnetization direction of the portion of the magnetic thin film 3 that has been heated by the light beam irradiation is reversed, and a recording pattern as shown in FIG. Is done. Here, P ₁ , P ₂ and P ₃ indicate recording pits each composed of a magnetic domain having a magnetization in a predetermined direction (upward in this example). The portion other than the recording pit has a magnetization in a direction (downward) opposite to the magnetization direction of the recording pit. In this embodiment, when recording a 1.5T pit, the upward magnetic field is applied relatively longer than the other pits. The curvature of the other pits approaches, and the deviation of the tip position is reduced to ΔL ′ as compared with the conventional example. Also, 1.5T
And the width of the pits of 2T to 4T have almost no difference. This will be described with reference to FIG.

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

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

The optimum value of the ratio of lengthening the short pulse varies depending on the frequency of the recording signal, the relative speed between the light beam and the medium, etc. 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, a sufficient effect was obtained by increasing the length by several% to 10%.

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

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

Tables 1, 2, and 3 below are obtained by analyzing the results of FIGS. 9, 10, and 11, respectively. These tables also show 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 a third embodiment of the magneto-optical recording method according to the present invention. This embodiment combines the above-described first and second embodiments to start the reversal of the magnetic field at a timing earlier than the magnetic field reversal timing determined for the longer pulse when recording the shortest pulse. And, when recording the shortest pulse, a magnetic field in a predetermined direction is applied to the magnetic thin film longer than a period corresponding to the length of the pulse as compared with a case where a longer pulse is recorded. It is. The method of the present embodiment can also be performed by the apparatus having the configuration shown in FIG. However, the compensation circuit 12
Is based on the recording signal corresponding to the code sent from the encoding circuit 10, and determines the length of the shortest pulse in the recording signal,
It is configured to output a compensation signal that is relatively long with respect to longer pulses and is shifted in a direction in which the shortest pulse is relatively preceding with respect to longer pulses.

In the device shown in FIG.
When data having a period T indicated by A is input, the encoding circuit 10 converts the data into a code as indicated by B. here,
The conversion by the (2, 7) code has been described as an example. Compensation circuit 12
Generates a compensation signal shown in FIG. 12D in accordance with the output of the encoding circuit 10. This compensation signal D is shifted by ΔT ′ in the direction in which only the 1.5T pulse precedes the signal before compensation shown in FIG. 12C, and extends the length of the 1.5T pulse by 7%. Signal. In other words, in the compensation signal, the pulse of 1.5T in length is longer than the timing determined for the longer pulse of 2T to 4T by Δ.
The reversal of the polarity of the magnetic field starts from downward to upward at an early timing T ′. Also, after 1.5 × 1.07T from the start of the upward magnetic field inversion, the downward magnetic field inversion starts. ΔT ′ is a pulse of 1.5 × 1.07T and 2
The shift Δ of the tip position of the pit shown in FIG. 4 that occurs when the pulses T to 4T are recorded at the same timing.
This 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 the compensation signal flows through the electromagnet 1. That is, the 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.

By the current supplied as described above, a magnetic field whose strength changes as shown in FIG. 12E 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 place the completely the magnetic field of the inverted H _a polarity (upward magnetic field). Also, the pulse of the compensation signal
> At the falling timing, the polarity inversion starts again,
A state in which the magnetic field is applied -H _a place similar switching period.

By the application of the magnetic field as described above, the magnetization direction of the portion of the magnetic thin film 3 that has been heated by the light beam irradiation is reversed, and a recording pattern as shown in FIG. Is done. Here, P ₁ , P ₂ and P ₃ indicate recording pits each composed of a magnetic domain having a magnetization in a predetermined direction (upward in this example). The portion other than the recording pit has a magnetization in a direction (downward) opposite to the magnetization direction of the recording pit. In this embodiment, the reversal of the polarity of the magnetic field is ΔT ′.
1.5T for other pits because it started early
Recording position of the pit P ₂ of the shifts forward, no deviation occurs in the end position. The width of the pit P ₂ also becomes no little difference with the other pits. Therefore, information recorded by the method of this embodiment can be read at a high SN ratio.

The present invention can be applied to various applications other than the embodiment described above. 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 between these pulses. In addition, the present invention can obtain the same effect in recording a signal encoded by a method other than the (2, 7) code. Further, the present invention is not limited to mark length recording, but may be applied to mark-to-mark recording.

[0045]

As described above, according to the magneto-optical recording method and apparatus of the present invention, a short pulse in a recording signal is shifted in the leading direction or the length of the short pulse is increased, so that jitter is reduced. 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, according to the present invention, higher-density information recording becomes possible.

[Brief description of the drawings]

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

FIG. 2 is a timing chart for explaining a 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 reproduced signals from these pits.

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

FIG. 5 is a schematic diagram showing pits recorded by the method of the second embodiment and waveforms of reproduced 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 according to 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 according to the second embodiment of the present invention.

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

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

FIG. 11 is a histogram diagram of a pit length read from information recorded by the method according to the second embodiment of the present invention.

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

FIG. 13 is a schematic configuration diagram showing one embodiment of a conventional magneto-optical recording device.

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

FIG. 15 is a schematic diagram showing pits recorded by a conventional method and waveforms of reproduced 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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105 G11B 5/02

Claims (7)

(57) [Claims] 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 polarizes at a timing corresponding to a recording signal including a plurality of types of pulses having different lengths. In a magneto-optical recording method for recording information by applying a magnetic field that reverses 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 is performed. A magneto-optical recording method, wherein the reversal of the magnetic field is started at a timing earlier than the timing. 2. The time difference between the timing of starting the reversal of the magnetic field with respect to the short pulse and the timing of starting the reversal of the magnetic field with respect to the longer pulse is as follows. 2. The magneto-optical recording method according to claim 1, wherein the time difference is a time difference corresponding to a shift of a tip position of a pit recorded on the magnetic thin film corresponding to each pulse, which occurs when inversion of the pit is started. 3. A means for irradiating a light beam to a magneto-optical recording medium having a magnetic thin film as a recording layer, and inverting the polarity at a timing corresponding to a recording signal including a plurality of types of pulses having different lengths on the magnetic thin film. And a means for applying a magnetic field, wherein a means for generating a compensation signal in which a short pulse in the recording signal is shifted in a direction relatively preceding a longer pulse is provided. A magneto-optical recording device, wherein the polarity of a magnetic field applied to the magnetic thin film is reversed according to a signal. 4. A method for irradiating 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 inverting the polarity according to a recording signal including a plurality of types of pulses having different lengths. In the magneto-optical recording method of recording information by applying a magnetic field to the magnetic thin film, when recording a short pulse of the plurality of types of pulses, the length of the pulse is longer than when a longer pulse is recorded. A magneto-optical recording method, wherein a magnetic field in a predetermined direction is applied to the magnetic thin film for a period longer than the corresponding period. 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 reversed in response to a recording signal including a plurality of types of pulses having different lengths. And a means for generating a compensation signal in which the length of a short pulse in the recording signal is made relatively long with respect to a longer pulse. A magneto-optical recording device wherein the polarity of a magnetic field applied to a magnetic thin film is reversed. 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 polarizes at a timing corresponding to a recording signal including a plurality of types of pulses having different lengths. In a magneto-optical recording method for recording information by applying a magnetic field that reverses 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 is performed. The magnetic field reversal is started at a timing earlier than the timing, and when recording a short pulse, the magnetic field in a predetermined direction is longer than a period corresponding to the length of the pulse as compared with a case where a longer pulse is recorded. A magneto-optical recording method, wherein the method is applied to a magnetic thin film. 7. A means for irradiating a light beam to a magneto-optical recording medium having a magnetic thin film as a recording layer, and a magnetic field whose polarity is inverted in response to a recording signal including a plurality of types of pulses having different lengths. Applying a short pulse in the recording signal in a direction relatively preceding a longer pulse, and
Means is provided for generating a compensation signal having a shorter pulse length relatively longer than a longer pulse, and inverting the polarity of the magnetic field applied to the magnetic thin film according to the compensation signal. Magneto-optical recording device.