JP2001202668A - Magneto-optical reproducing method and magneto-optical reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the deviation on the symmetry of the regenerative signal generated by the influence of a reproduction assisting magnetic field in magnetic domain expansion reproduction by domain wall displacement. SOLUTION: A correction rate computation circuit 5 determines, by computation, the correction rate necessary for the reproduction assisting magnetic field or at what deviation occurs when the mark of a normal length is reproduced at the reproducing magnetic field intensity. A reproduction signal correction circuit 9 corrects the regenerative signal obtained by a differential amplifier circuit 4 in accordance with the information on this correction rate, by which the regenerative signal meeting the recording mark length is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical reproducing method and a magneto-optical reproducing apparatus for reproducing information recorded on a magneto-optical recording medium by irradiating light such as a laser beam.

[0002]

2. Description of the Related Art In a magneto-optical recording system, the temperature of a ferrimagnetic thin film is locally increased to a point close to a Curie point or a compensation point, and the coercive force of the heated portion is reduced to reduce the direction of an externally applied recording magnetic field. The basic principle is to record information by reversing the direction of magnetization. The portion where the magnetization direction is reversed, that is, the information mark forms a magnetic domain, and the information is reproduced by reading it out by the magnetic Carr effect. In such magneto-optical recording and reproduction,
In order to improve the recording density, it is necessary to shorten the recording mark length, that is, to miniaturize the information magnetic domain.

However, the reproduction resolution of the signal is almost the same as the wavelength λ of the light source of the reproduction optical system and the numerical aperture N of the objective lens.
The spatial frequency 2NA / λ is the reproduction limit.
Therefore, in order to increase the recording density, it is conceivable to shorten the wavelength λ of the light source or to reduce the spot light diameter of the reproducing apparatus by using a high NA lens. However,
The wavelength of the laser which is currently at a practical level is only about 680 nm, and the use of a high NA lens reduces the depth of focus. Therefore, the distance between the objective lens and the magneto-optical disk is required to be high. Manufacturing accuracy becomes severe. Therefore, the NA of the objective lens cannot be so high, and the practically usable lens NA is at most 0.6. That is, the wavelength λ of the light source and the numerical aperture NA of the objective lens
There is a limit to the improvement in recording density.

Therefore, as a conventional method for solving the problem of the recording density defined by such a reproducing condition,
A magneto-optical reproducing method and a reproducing apparatus disclosed in Japanese Patent Application Laid-Open No. 6-290496 are known. In this reproducing method, a recording magnetic domain of a recording layer (third magnetic layer) of a magneto-optical recording medium is transferred at room temperature to a domain wall moving layer, which is a first magnetic layer, by exchange coupling force via a second magnetic layer. The domain wall movement in the laser spot is caused by utilizing the temperature gradient in the laser spot due to the irradiation of the laser beam at the time, and it is possible to enlarge and reproduce a small mark (magnetic domain). Thus, the reproduction of the minute magnetic domains that cannot be reproduced with the normal reproduction resolution described above is performed, thereby achieving a dramatic improvement in the recording density.

[0005] Here, the above-mentioned Japanese Patent Application Laid-Open No. 6-290496.
A magneto-optical reproducing method and a reproducing apparatus disclosed in Japanese Patent Application Laid-Open Publication No. H10-209 will be briefly described. The magneto-optical recording medium A is shown in FIG.
Magnetic three-layer film (first, second and third magnetic layers) A shown in FIG.
3 to A5. More specifically, the magneto-optical recording medium A includes a first magnetic layer A3 on a light-transmitting substrate A1 via a transparent dielectric layer A2 serving as a protective film or a multiple interference film.
The third magnetic layer A5 is formed by sequentially laminating the second magnetic layer A4 and the third magnetic layer A5 in vacuum, for example, by continuous sputtering.
A non-magnetic metal film (not shown) or a dielectric layer A6 is formed thereon, and a protective layer A7 is formed on the dielectric layer A6 if necessary.

Irradiation with laser light or the like is performed from the light-transmitting substrate A1 side (the irradiation direction of the laser light is indicated by an arrow L in the figure). First magnetic layer A3, second magnetic layer A4, third magnetic layer A
Reference numeral 5 denotes a film having an easy axis of magnetization in a vertical direction (a direction perpendicular to the film surface), that is, a so-called perpendicular magnetization film, which is an amorphous thin film made of a heavy rare earth-iron group metal. The Curie temperatures of the first, second, and third magnetic layers A3, A4, and A5 are set to T, respectively, in consideration of the temperature rise during recording and reproduction by the laser beam.
Assuming that c1, Tc2, and Tc3, it is necessary that Tc3>Tc1> Tc2.

The first magnetic layer A3 serving as a domain wall displacement layer
Requires a film having small anisotropy and coercive force in order to easily cause domain wall displacement. Therefore, it is desirable to use a material based on a Gd—Fe film. On the other hand, the third magnetic layer A5 serving as a memory layer for holding recorded information has a coercive force sufficient for recording marks (magnetic domains) to be stably present at room temperature, and has a Curie temperature suitable for recording. It must be a film, and it is therefore desirable to use a material based on a Tb-Fe-Co film. In addition, the above-mentioned Curie temperature Tc
It is desirable that the adjustment of 1, Tc2, and Tc3 be performed by adding a non-magnetic element that does not significantly change the magnetic properties.

[0008]

FIG. 5A is a conceptual diagram showing a state of detection of domain wall movement during reproduction. In order to simplify the drawing, the first, second, and third magnetic layers A3, A4, A
5 is depicted as magneto-optical recording medium A. FIG.
(B) shows the temperature distribution of the magneto-optical recording medium (disk) heated by the laser beam irradiation. When the disk A rotating at a constant speed is irradiated with the focused laser spot to heat the disk A, Elliptical temperature distribution regions having different temperature gradients are formed on the disk in the forward (right side in the drawing) and rearward (left side in the drawing) directions of the laser beam. This temperature gradient has a steeper slope in the forward direction of the laser beam than in the backward direction of the laser beam.

FIG. 5C shows a force F (x) for causing a domain wall motion in the first magnetic layer A3. Here, σ represents the domain wall energy, x represents the direction of travel of the laser beam as positive, and represents the domain wall position when the peak temperature position by the laser beam shown in FIG.

FIG. 5A shows a state in which the domain wall movement for signal detection occurs in the first magnetic layer A3 in the forward direction of the laser beam due to the temperature gradient in the forward direction of the laser beam. . An area S in FIG. 5B indicates an area heated to a temperature equal to or higher than the threshold temperature Ts. Here, since Ts> Tc2, the magnetization has disappeared in the second magnetic layer A4, whereby the exchange coupling between the third magnetic layer A5 and the first magnetic layer A3 via the second magnetic layer A4 becomes: In this area S, the state is cut off. The recording signal is
It is formed and stored as a magnetization reversal region (magnetic domain) in the third magnetic layer A5. In FIG. 5A, a hunted down arrow region corresponds to the region.

In a region outside the region S, a recording mark (magnetic domain) transferred from the third magnetic layer A5 to the first magnetic layer A3 by the exchange coupling via the second magnetic layer A4 is formed as the disk rotates. When entering the area S, the domain wall formed on one side of the recording mark instantaneously moves to the peak temperature position in the area S (this operation is indicated by an arrow AA in FIG. 5A). T). The process of moving the domain wall will be referred to as a front process here.

The force F (x) that causes domain wall motion is:
As shown in FIG. 5C, F (x) = − ∂σ / ∂x (1) Here, σ represents the domain wall energy, and x represents the domain wall position when the traveling direction of the laser beam is positive and the peak temperature position shown in FIG. 5B is the origin (zero).

FIG. 6 is a conceptual diagram showing a state of domain wall motion detection similar to FIG. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted. In the case of a specific mark length, domain wall movement as shown by an arrow BB in FIG. 6A may occur depending on the temperature gradient behind the traveling direction of the laser beam. This process of moving the domain wall will be referred to as a rear process here. The mark length at which both front and rear processes can occur is 0.25
μm or more, but in the reproduction without applying the reproduction auxiliary magnetic field, the reproduction signal of the mark of 0.25 μm or more is
The domain wall movement detection by both processes is detected as a superimposed waveform with a certain delay time.

This superimposed signal detection waveform causes an inconvenient state in normal signal reproduction processing. Therefore, this problem can be solved by applying a reproduction auxiliary magnetic field from the opposite side of the laser beam as shown in FIGS. That is, even when a mark of any length is reproduced by the reproduction auxiliary magnetic field, domain wall movement in the rear process is suppressed.

As described above, since the temperature gradient in the region S is (temperature gradient used in the front process)> (temperature gradient used in the rear process), this operation becomes possible. FIGS. 7 and 8 illustrate this. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted. 7 and 8 are enlarged views of the domain wall moving operation portion of FIGS. 5 and 6, respectively. An outline arrow F1 in FIG. 7 is a domain wall driving force due to a temperature gradient at the time of the front process, and is represented by the above equation (1). Open arrow F2 in FIG.
Is the domain wall driving force by Zeeman energy generated by the reproduction assisting magnetic field. On the other hand, the outline arrow F in FIG.
Reference numeral 4 denotes a domain wall driving force due to a temperature gradient during the rear process, and is represented by F (x) = ∂σ / ∂x (2).

An outline arrow F3 in FIG. 8 indicates a domain wall driving force by Zeeman energy generated by the reproduction assisting magnetic field. Now, from the difference between the above-mentioned temperature gradients and (temperature gradient used in the front process)> (temperature gradient used in the rear process), the reproduction auxiliary magnetic field strength satisfying F1> F2 and F3> F4 (3) is obtained. It can be said that it exists. Therefore, by selecting a reproduction auxiliary magnetic field intensity that satisfies the expression (3), it is feasible to suppress domain wall movement in the rear process and to cause only domain wall movement in the front process.

However, a new problem arises here. It is F2 in front process,
That is, the domain wall driving force that hinders the domain wall motion detection depends on the strength of the auxiliary reproduction magnetic field, and delays the domain wall motion by F1, that is, the rise of signal detection. Since the delay of the rise is proportional to the strength of the auxiliary reproduction magnetic field, as shown in FIG. 9, the area of the upward arrow, which is in the same direction as the auxiliary reproduction magnetic field, is longer by a certain amount, and the area of the downward arrow is shorter by the same length. It will be detected as a signal. That is,
The symmetry of the reproduced signal is detected as being shifted.

FIG. 10 is a diagram in which the change in mark length of a reproduction signal according to the conventional reproduction method is plotted for each recording mark length, and shows the change in the length of the area indicated by the upward arrow. FIG. 11 is a diagram in which the deviation (symmetry deviation) from the ideal mark length of the reproduction signal by the conventional reproduction method is plotted for each recording mark length, and the shift (symmetry deviation) is the length of the area. It is constant regardless of the recording mark length. FIG. 12 is a diagram in which a change in the duty ratio of a reproduction signal according to a conventional reproduction method is plotted with respect to a reproduction auxiliary magnetic field, and shows that the shift amount is proportional to the reproduction magnetic field intensity.

Accordingly, the present invention provides a magneto-optical reproducing method and a magneto-optical reproducing apparatus capable of correcting a deviation in symmetry of a reproduction signal generated by the influence of a reproduction auxiliary magnetic field in magnetic domain expansion reproduction by domain wall movement. Aim. In particular, the present invention relates to a magneto-optical reproducing method and a magneto-optical reproducing apparatus capable of correcting a deviation in symmetry of a reproduction signal caused by a difference in film composition when a rear domain wall motion is suppressed with a constant reproduction auxiliary magnetic field strength. The purpose is to provide.

[0020]

According to the present invention, a recording mark is reproduced by applying a light beam and, if necessary, by applying a reproducing auxiliary magnetic field in order to achieve the above object. In addition, a deviation of the symmetry of the mark length of the reproduction signal is detected, and the deviation of the symmetry of the mark length of the reproduction signal is corrected based on the deviation.

That is, according to the present invention, in a magneto-optical reproducing method for reproducing a recording mark constituted by magnetic domains formed in a magnetic layer of a magneto-optical recording medium, the recording mark is reproduced by applying at least a light beam. A reproducing step for detecting, a deviation amount of a symmetry of a mark length of a signal reproduced in the reproducing step, a deviation amount detecting step, and reproducing in the reproducing step based on the deviation amount detected in the deviation amount detecting step. And a correction step for correcting a deviation of the symmetry of the mark length of the obtained signal.

According to the invention, in a magneto-optical reproducing apparatus for reproducing a recording mark constituted by magnetic domains formed in a magnetic layer of a magneto-optical recording medium, the recording mark is reproduced by applying at least a light beam. A reproducing means for detecting the deviation of the symmetry of the mark length of the signal reproduced by the reproducing means, and reproducing by the reproducing means based on the deviation detected by the deviation detecting means. And a correcting means for correcting the deviation of the symmetry of the mark length of the obtained signal.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A magneto-optical reproducing method and a magneto-optical reproducing apparatus according to the present invention will be described below with reference to FIG. This magneto-optical reproducing apparatus is schematically shown as a spindle motor 2, a pickup (PU) 3, a differential amplifier circuit 4,
The correction amount calculation circuit 5, the magnetic head 6, the reproduction magnetic field control circuit 7, the drive circuit 8, the reproduction signal correction circuit 9, and the irradiation of the reproduction signal (Readout Sig.) From the reproduction signal (Readout Sig.) To the information signal and the disk in a favorable state. And a playback signal processing circuit (not shown) for obtaining a tracking control signal and a focus control signal playback signal.

The disk 1 has a first magnetic layer A3 for irradiating the substrate A1 shown in FIG. 4 with a light beam at the time of reproduction to read the change in the polarization plane of the reflected light due to the polarity of the perpendicular magnetization.
A third magnetic layer A5 for recording the recording signal by applying a magnetic field having a polarity corresponding to the recording signal by the magnetic head 6 being heated to a Curie temperature or higher by irradiating a light beam during recording; A magneto-optical disk having the same structure as a magneto-optical disk A in which a second magnetic layer A4 and a protective layer A7, etc., which control the function of transferring the recording magnetization recorded on the layer A5 to the first magnetic layer A3 with respect to temperature, are stacked. It is. The magneto-optical disk 1 is supported by a spindle motor 2 and rotates at a predetermined rotation speed.

Although a detailed configuration of the PU 3 is not shown, a semiconductor laser as a light source for irradiating the disk 1, a collimator lens for converting a light beam emitted from the semiconductor laser into parallel light, a cross section of the light beam A light shaping prism, beam splitter, and a quarter-wave plate having the property of converting the plane of polarization of a light beam into linearly polarized light and circularly polarized light. A light beam is focused so as to focus on the disk 1. An objective lens, a polarizing beam splitter (PBS) having a characteristic of transmitting and reflecting a light beam having a linear polarization plane at a certain ratio,
Half-wave plate with the property of rotating by one degree and disk 1
And an optical system including a photodetector for detecting the light reflected and transmitted through the polarization beam splitter, respectively, and a light beam which is always transmitted to the disc 1 in a good condition in order to detect a signal from the disc 1 in a good condition. And an actuator for moving the objective lens for condensing light.

The reproduction magnetic field control circuit 7 controls the intensity of a reproduction auxiliary magnetic field (DC magnetic field) applied during reproduction. What is important here is that the auxiliary reproduction magnetic field strength must be determined so that the domain wall driving force in the forward direction of the laser beam is not erased and only the domain wall movement in the backward direction of the laser beam is suppressed. The differential amplifier circuit 4 performs a differential operation on the signal detected by the photodetector of the PU 3 to obtain a magneto-optical reproduction signal. As described above, this reproduced signal has a shift in the mark length (a shift in symmetry). The signal detected by the photodetector is also sent to a reproduction signal processing circuit (not shown) to obtain a recording information signal, a tracking control signal, a focus control signal, and the like.

Here, the amount of correction for canceling the deviation of the mark length (the deviation of the symmetry) from the reproduction auxiliary magnetic field varies depending on the characteristics of the disk 1. Therefore,
A correction amount calculating circuit 5 for detecting the amount of symmetry deviation of the reproduction signal calculates the amount of symmetry deviation correction required for the reproduction auxiliary magnetic field from the disk characteristic information obtained from the signal detected by the photodetector. Ask. The reproduction signal correction circuit 9 for correcting the amount of symmetry deviation of the reproduction signal is equal to the amount of symmetry deviation correction obtained by the correction amount calculation circuit 5.
By correcting the signal length, a magneto-optical reproduction signal (Readout Si
g.)

The drive circuit 8 outputs a drive signal to be applied to the magnetic head 6, and this drive signal becomes a drive signal corresponding to a recording signal at the time of recording, and becomes a DC drive signal by an input from the reproduction magnetic field control circuit 7 at the time of reproduction. . The magnetic head 6 generates a magnetic field on the disk 1 by the output of the drive circuit 8.

In such a magneto-optical reproducing apparatus, the correction amount calculation circuit 5 determines the amount of shift required when reproducing a mark of a correct length required for the auxiliary reproduction magnetic field or a regular length in the reproducing magnetic field intensity. Is obtained by calculation.
In this case, the shift amount is constant regardless of the mark length as shown in FIG. 11, so that this value can be used as it is as the correction amount. There are several methods for acquiring the disc characteristic information, such as reading information recorded on the disc 1 in advance, or performing trial writing before reproduction to determine the correction amount. When information is recorded on the disk 1, a method of calculating a correction amount according to the information is effective.
It is effective to record and reproduce a mark of a certain length, compare it with a regular mark length, and obtain a correction amount.

The reproduction signal correction circuit 9 corrects the reproduction signal obtained from the differential amplifier circuit 4 based on the information on the correction amount, thereby obtaining a reproduction signal that matches the recording mark length.

Therefore, by applying the reproduction auxiliary magnetic field by the reproduction correction which complementarily corrects the relationship between FIG. 10 and FIG. 11, the influence of the pseudo mark due to the domain wall movement from behind can be eliminated. At the same time, it is possible to eliminate the duty shift of the reproduction signal due to the reproduction auxiliary magnetic field, and it is possible to obtain a good reproduction signal.

<Second Embodiment> In the first embodiment, in a state where the intensity of the reproduction auxiliary magnetic field for suppressing the backward domain wall movement is constant, the deviation of the symmetry is corrected, and accurate reproduction is performed. The case of obtaining a signal has been described,
In the second embodiment, when the auxiliary reproduction magnetic field strength for suppressing the backward domain wall movement differs for each disk, the auxiliary reproduction magnetic field intensity is controlled based on the control data of the auxiliary reproduction magnetic field intensity recorded on the disk. It is configured to be variable.

As described in the first embodiment, the practical application of the high-density recording / reproduction using the magnetic domain expansion reproduction method becomes more practical by the application of the reproduction auxiliary magnetic field and the mark length correction recording / reproduction. What is important is that the reproduction assist magnetic field is selected so that the domain wall driving force in the forward direction of the laser beam is not erased and only the domain wall movement in the backward direction of the laser beam is suppressed.
That is something that must be decided. Also, the domain wall driving force due to the temperature gradient varies depending on the film composition of the medium, etc.
When several types of media are put to practical use, it is conceivable that the effective reproduction assisting magnetic field intensity has a different value depending on the media.

Further, a method of changing the layer structure of the recording medium, for example, is used to prevent a domain wall from moving backward in the laser beam traveling direction up to a somewhat longer mark length, and to use a modulation method that does not use a longer mark length. In addition, there has been proposed a recording medium and a reproducing method that do not provide a reproduction auxiliary magnetic field (reproduction auxiliary magnetic field intensity = 0). Therefore, when these media are put to practical use, a system is required that can grasp and adjust the intensity of the reproduction auxiliary magnetic field required for each medium and perform good reproduction. That is, it is necessary to set, for example, the reproduction auxiliary magnetic field strength to 0, 50, and 100 Oersteds according to the medium.

A magneto-optical reproducing apparatus according to a second embodiment will be described with reference to FIG. In this magneto-optical reproducing apparatus, the correction amount calculation circuit 5 and the reproduction signal correction circuit 9 shown in FIG. 1 are omitted, and a reproduction magnetic field calculation circuit 10 is provided instead. The reproducing magnetic field control circuit 7 controls the reproducing magnetic field operation circuit 1 during reproduction.
The intensity of the auxiliary reproduction magnetic field (DC magnetic field) is controlled based on the reproduction magnetic field calculated by 0.

The intensity of the reproduction auxiliary magnetic field necessary for reproduction depends on the characteristics of the disk 1. Therefore, the reproduction magnetic field calculation circuit 10 calculates and obtains the reproduction auxiliary magnetic field intensity from the disc characteristic information obtained through the differential amplifier circuit 4 from the signal detected by the photodetector in the PU 3. In particular, the reproducing magnetic field calculation circuit 10 calculates the required reproducing magnetic field intensity from the reproducing signal information recorded as the control data of the disk 1 and the reproducing light beam intensity. Based on the result, the reproducing magnetic field intensity is set in the reproducing magnetic field control circuit 7, whereby a desired magnetic field can be generated. Therefore, according to the second embodiment, it is possible to set, for example, the reproduction auxiliary magnetic field intensity = 0, 50, and 100 Oersted based on the control data of the reproduction auxiliary magnetic field intensity recorded on the disk. . At this time, since the domain wall driving force in the forward direction of the laser beam is also affected by the reproduction auxiliary magnetic field, the rise of the reproduction modulation signal detection is delayed, and the symmetry is deviated as shown in FIG. In the embodiment, as in the first embodiment, the deviation of the symmetry of the reproduced signal is corrected.

<Third Embodiment> When the auxiliary reproduction magnetic field strength for suppressing the backward domain wall motion differs from disk to disk, the above-described second embodiment uses the auxiliary reproduction magnetic field strength recorded on the disk. In the third embodiment, the recording / reproducing characteristics of the disk are measured when the control data of the reproducing auxiliary magnetic field intensity is not recorded on the disk. The reproduction auxiliary magnetic field intensity is made variable based on the measurement result. That is, the magneto-optical reproducing device shown in FIG. 3 does not include the correction amount calculation circuit 5 and the reproduction signal correction circuit 9 shown in FIG. 1, and is provided with a reproduction magnetic field calculation circuit 10 and a shift amount detection circuit 11 instead. . The shift amount detection circuit 11 checks the shift amount of the duty ratio of the reproduced waveform of the single signal obtained through the differential amplifier circuit 4 from the signal detected by the photodetector in the PU 3, Calculates the reproduction auxiliary magnetic field intensity based on this deviation amount.

In the third embodiment, since the control data of the reproduction auxiliary magnetic field intensity is not recorded on the disk, the reproduction auxiliary magnetic field intensity is determined by trial writing before recording. The drive circuit 8 outputs a single signal having a duty ratio of 50%, for example, and records the signal on the disk 1.
Since the deviation amount of the duty ratio with respect to the variation amount of the magnetic field intensity is constant, for example, the reproduction magnetic field control circuit 7 sets two types of magnetic field intensity = 0 and 100 Oersteds, and reproduces the reproduced signal. If the deviation amount of the duty ratio is input to the deviation amount detection circuit 11 and the deviation amount of the duty ratio is obtained, the reproduction magnetic field calculation circuit 10 can obtain the optimum reproduction auxiliary magnetic field intensity at which the duty ratio = 50%. Also, when a single signal with a duty ratio = 50% is formatted on the disk 1 in advance, the auxiliary reproduction magnetic field strength is obtained by the same procedure. And, based on this result,
The reproducing magnetic field intensity is set by the reproducing magnetic field control circuit 7.

As a result, a desired magnetic field can be generated, and for a disk which does not require a reproduction auxiliary magnetic field, the reproduction magnetic field calculation circuit 10 can obtain a magnetic field intensity of 0. Playback is performed. By using these methods and devices, the intensity of the reproduction auxiliary magnetic field for eliminating the influence of the pseudo mark due to the domain wall movement from behind can be adjusted regardless of the type of disk.
Therefore, according to the third embodiment, when the control data of the auxiliary reproduction magnetic field intensity is not recorded on the disk, for example, the auxiliary reproduction magnetic field intensity = 0, 50, 1
00 Oersted can be set. In the third embodiment, similarly to the first embodiment, the deviation of the symmetry of the reproduction signal is corrected.

Therefore, according to the present invention, the following inventions are provided in addition to the inventions described in the claims. (1) The magneto-optical reproducing method according to claim 1, wherein the correction amount selects a value uniquely determined by characteristics of a recording medium with respect to the intensity of a reproduction auxiliary magnetic field applied at the time of reproduction. (2) means for acquiring information such as characteristics of the disc relating to the correction amount, and determining the correction amount based on the obtained information;
3. A magneto-optical reproducing apparatus according to claim 2, further comprising means for adjusting a mark length of the reproduction signal by a predetermined correction amount. (3) In a magneto-optical reproducing method for reproducing a recording mark constituted by magnetic domains formed in a magnetic layer of a magneto-optical recording medium, the intensity of a reproduction auxiliary magnetic field applied when reproducing a recording mark is obtained from the recording medium. A magneto-optical reproducing method characterized in that reproduction is performed by switching to an appropriate value according to the information. (4) The magneto-optical reproducing method according to (3), wherein the value of the auxiliary reproduction magnetic field strength is selected from values determined by characteristics inherent to a recording medium. (5) In a magneto-optical reproducing apparatus for reproducing a recording mark composed of magnetic domains formed in a magnetic layer of a magneto-optical recording medium, the intensity of a reproduction auxiliary magnetic field applied when reproducing the recording mark is obtained from the recording medium. A magneto-optical reproducing device comprising means for switching to an appropriate value in accordance with the reproduced information for reproduction. (6) means for acquiring information such as characteristics of the recording medium relating to the auxiliary reproduction magnetic field, and determining an appropriate value of the auxiliary reproduction magnetic field intensity based on the obtained information; and means for adjusting the auxiliary reproduction magnetic field intensity to the appropriate value. (5)
3. The magneto-optical reproducing device according to 1.

[0041]

As described above, according to the present invention, a recording mark is reproduced by applying a light beam and a reproduction auxiliary magnetic field, a deviation amount of a symmetry of a mark length of a reproduction signal is detected, and the deviation amount is determined. Since the deviation of the symmetry of the mark length of the reproduction signal is corrected based on the reproduction signal, it is possible to correct the deviation of the symmetry of the reproduction signal caused by the influence of the reproduction auxiliary magnetic field in the magnetic domain expansion reproduction due to the domain wall movement.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a magneto-optical reproducing device according to the present invention.

FIG. 2 is a block diagram illustrating a magneto-optical reproducing device according to a second embodiment.

FIG. 3 is a block diagram illustrating a magneto-optical reproducing device according to a third embodiment.

FIG. 4 is a diagram for explaining a laminated structure of a magneto-optical recording medium.

FIG. 5 is a diagram for explaining detection of domain wall movement during reproduction.

FIG. 6 is a diagram for explaining detection of domain wall movement during reproduction.

FIG. 7 is a diagram for explaining detection of domain wall movement during reproduction.

FIG. 8 is a diagram for explaining detection of domain wall movement during reproduction.

FIG. 9 is a diagram showing a mark length shift of a reproduction signal due to a reproduction auxiliary magnetic field.

FIG. 10 is a diagram in which a change in mark length of a reproduction signal according to a conventional reproduction method is plotted for each recording mark length.

FIG. 11 is a diagram in which a deviation amount of a mark length of a reproduction signal from an ideal according to a conventional reproduction method is plotted for each recording mark length.

FIG. 12 is a diagram in which a change in a duty ratio of a reproduction signal according to a conventional reproduction method is plotted with respect to a reproduction auxiliary magnetic field.

[Explanation of symbols]

Reference Signs List 1 disc 3 pickup (constituting reproducing means together with differential amplifier circuit 4, magnetic head 6, reproducing magnetic field control circuit 7, and driving circuit 8) 5 correction amount calculating circuit (deviation amount detecting means) 7 reproducing magnetic field control circuit 9 reproducing signal Correction circuit (correction means) 10 Reproduction magnetic field calculation circuit 11 Shift amount detection circuit

Claims (2)

[Claims] 1. A magneto-optical reproducing method for reproducing a recording mark constituted by magnetic domains formed in a magnetic layer of a magneto-optical recording medium, comprising: a reproducing step of reproducing the recording mark by applying at least a light beam; Detecting a shift amount of the symmetry of the mark length of the signal reproduced in the reproduction step; and a mark of the signal reproduced in the reproduction step based on the deviation amount detected in the deviation amount detection step. A correction step of correcting a deviation of the long symmetry. 2. A magneto-optical reproducing apparatus for reproducing a recording mark constituted by magnetic domains formed in a magnetic layer of a magneto-optical recording medium, comprising: reproducing means for reproducing the recording mark by applying at least a light beam; A shift amount detecting unit that detects a shift amount of symmetry of a mark length of a signal reproduced by the reproducing unit; and a mark of the signal reproduced by the reproducing unit based on the shift amount detected by the deviation amount detecting unit. A magneto-optical reproducing device, comprising: a correcting unit configured to correct a deviation of the long symmetry.