JP2000298889A - Reproduction power detection method and device, reproduction power control method and device, and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform control so that the reproduction power of a light beam can be optimized rapidly and optimally when reproducing data from a high- density recording magnetooptical record medium. SOLUTION: A magnetic domain separation region (non-magnetic region) is provided in a zigzag at both sides in the radial direction of the magnetooptical disk of the recording track of data. A modulation frequency component according to the zigzag of the magnetic domain separation region is detected from a reproduction signal RF, and the amplitude level of the modulation frequency component is detected from a band-pass filter 211 by a detection circuit 212. The reproduction power of a light beam is controlled according to the amplitude level of the modulation frequency component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a reproducing power of a light beam when the light beam is irradiated to the magneto-optical recording medium in order to reproduce data from the magneto-optical recording medium. The present invention relates to a control method and a control device for a reproducing power of a light beam, and a reproducing device for a magneto-optical recording medium using these methods and devices.

[0002]

2. Description of the Related Art In recent years, as a rewritable high-density recording medium, DWDD (Domain Wall Displ) has been developed.
2. Description of the Related Art Magneto-optical discs of the "Act. As disclosed in JP-A-6-290496, a DWDD type magneto-optical disk is composed of at least a magnetic three-layer film of a domain wall moving layer, a switching layer, and a magnetic recording layer (memory layer). By using the magnetic wall movement of the domain wall motion layer in the region where the magnetic film temperature is equal to or higher than the Curie temperature of the switching layer, it is possible to increase the size of the effectively recorded magnetic domain and increase the reproduction signal. You can do it.

FIG. 9B shows a cross section of a track 7 (FIG. 9A) of a DWDD magneto-optical disk. As shown in FIG. 9B, the DWDD magneto-optical recording disk includes a magnetic layer 3 formed on a transparent substrate 2. The magnetic layer 3 includes a magnetic wall moving layer 4, a switching layer 5, and a magnetic recording layer 6.
Are laminated. In this case, the domain wall motion layer 4 is composed of a perpendicular magnetic film having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer 6, and the switching layer 5 has a lower Curie temperature than the domain wall motion layer 4 and the magnetic recording layer 6. The magnetic recording layer 6 is made of a perpendicular magnetization film.

In the magnetic recording layer 6, information signal marks (perpendicular magnetic signals) magnetized upward and downward according to information are recorded. At room temperature, the magnetization in the magnetic recording layer 6 is transferred to the domain wall displacement layer 4 via the switching layer 5 by the exchange coupling force acting between the magnetic layers.
In FIG. 9B, the upward and downward arrows indicate the direction of magnetization. The boundaries between the information signal mark magnetized in one direction in each layer and the information signal mark magnetized in the opposite direction before and after the information signal mark, that is, the edges of the information signal mark, are domain walls Q01, Q02,. Is formed.

The perpendicular magnetic signal recorded on the DWDD magneto-optical disk thus formed is reproduced by utilizing the domain wall motion of the domain wall motion layer 4 as described below.

That is, as shown in FIG. 10, a reproducing light beam (laser beam) 70 is irradiated from the domain wall moving layer 4 side so as to converge as a minute light spot 71 on the track 7 of the magneto-optical disk. . The reproducing light beam 70 relatively moves in the direction indicated by the arrow a with the rotation of the magneto-optical disk. The magnetic layer 3 is heated by the irradiation of the reproducing light beam 70, and a temperature distribution having a peak at a position P <b> 1 which is located rearward of the center of the light spot 71 with respect to the moving direction is formed.

[0007] Then, in FIG.
Indicates a region where the temperature reaches Ts which is a temperature near the Curie temperature of the switching layer 5, and the temperature of the magnetic layer 3 rises beyond the temperature Ts at the position P2 toward the back of the light spot 71, and the position P1 After reaching the peak at, it starts to fall.

At a position distant from the portion heated by the light spot 71, the temperature of the magnetic layer 3 is sufficiently low, and the domain wall displacement layer 4 is exchange-coupled to the magnetic recording layer 6 via the switching layer 5. Since the temperature distribution of the layer 3 is substantially uniform, no force acts to move the domain wall transferred to the magnetic deafness moving layer 4, so that the domain wall is fixed.

Here, in the portion of the switching layer 5 that has reached the position P2, the temperature rises to Ts and the magnetization disappears, so that the domain wall that has reached the position P2 (in the illustrated example, the domain wall Q
No. 06) is no longer restricted by the exchange coupling force in the domain wall displacement layer 4, while it is subjected to a force due to a temperature gradient. As a result, as shown in FIG. 10B, the domain wall Q06 moves in the domain wall displacement layer 4 in the direction indicated by the arrow b with higher temperature and lower domain wall energy, that is, toward the temperature peak position P1.

As a result, as shown in FIG. 10A, a magnetized region 73 extending to a certain length regardless of the length of the original information signal mark is formed at the portion of the domain wall displacement layer 4 where the light spot 71 is irradiated. You. Using the magneto-optical effect generated by the magnetized region 73, a change in a signal recorded in a magnetic domain that is enlarged by the movement of the domain wall is detected from the reflected light from the light spot 71.

The magnetic domain walls Q01, Q02,..., Q07 transferred to the domain wall motion layer 4 move toward the temperature peak position P1 each time the light spot 71 moves to the position P2 one after another. Thus, the information signal is reproduced by detecting a change in the signal of the magnetic domain which is made to expand by an optical head (optical pickup).

Thus, even when the length of the information signal mark on the recording medium is smaller than the diameter of the spot of the reproducing light beam, a signal can be detected from the magnetized region to be expanded. To be. Therefore, a very large signal can be reproduced even from a minute recording magnetic domain having a period equal to or less than the optical limit resolution of the reproduction light, and the information can be reproduced without changing the light wavelength, the numerical aperture NA of the objective lens, and the like. High-density recording and reproduction of information recorded at high density.

[0013]

As described above with reference to FIG. 10, in the case of a DWDD magneto-optical disk, the light beam is formed so that a minute light spot 71 is formed on the track 7 of the magneto-optical disk. To raise the temperature of the magnetic layer at the light spot 71, generate domain wall motion in the light spot 71, and expand a magnetic domain to reproduce a recorded signal. Therefore, at the time of reproducing data recorded on the magneto-optical disk, the temperature of the light spot on the magneto-optical disk must always be kept good so that domain wall movement occurs effectively in the light spot 71. Is required.

That is, if the reproducing power of the light beam is weak,
On the magneto-optical disk, the area (domain wall movement area) surrounded by the domain wall movement isotherm and having a temperature at which domain wall movement occurs cannot be made sufficiently large, and the quality of data recorded on the magneto-optical disk is good. Playback cannot be performed. On the other hand, if the reproducing power of the light beam is too strong, the temperature of the light spot portion rises too much, causing the Kerr effect to attenuate. Due to the influence of the temperature characteristics of the leakage magnetic field, good reproduction of data recorded on the magneto-optical disk cannot be achieved.

For this reason, when reproducing data recorded on a DWDD magneto-optical disk, some information must be stored in order to always keep the size of the domain wall moving region in the light spot on the magneto-optical disk good. Accordingly, control is required to optimize the reproduction power of the light beam.

In view of the above, the present invention provides a method for detecting a reproduction power of a light beam, a method for controlling a reproduction power, and a method for controlling the reproduction power of a light beam to be optimized.
It is an object of the present invention to provide an apparatus for detecting a reproducing power of a light beam, a reproducing power control apparatus, and a reproducing apparatus using these methods.

[0017]

According to a first aspect of the present invention, there is provided a reproducing power detecting method for reading recorded main information in such a manner that a magnetic domain is enlarged by moving a domain wall. A method for detecting a reproducing power of a light beam applied to the magneto-optical recording medium for reproducing data from the magneto-optical recording medium, wherein the reproducing power is meandering along a land track or a groove track of the magneto-optical recording medium. A non-magnetic region is formed, and a modulation frequency component corresponding to the meandering of the non-magnetic region is extracted from a reproduction signal obtained from reflected light of the light beam from the magneto-optical recording medium, and its amplitude level is detected. The reproducing power of the light beam is detected based on the detection level.

According to the method for detecting the size of the domain wall motion region according to the first aspect, the magneto-optical recording medium is irradiated with the light beam by irradiating the magneto-optical recording medium with the light beam. By raising the temperature of the light spot portion, which is a portion, and expanding the magnetic domain by moving the domain wall, data recorded at high density is read.

If the reproducing power of the light beam is low, the domain wall moving region, which is the region where the domain wall displacement occurs in the magnetic layer of the magneto-optical recording medium, is small, and the region where the magnetic domain is enlarged is small. Cannot obtain a proper reproduction signal. Conversely, if the reproducing power of the light beam becomes too large, the temperature of the light spot on the magneto-optical recording medium rises too much, causing the Kerr effect to attenuate or the domain wall moving region becoming too large, causing A good reproduction signal cannot be obtained due to the influence of the temperature characteristics of the peripheral leakage magnetic field.

When the reproducing power of the light beam is weak, as described above, the domain wall moving region is small, and the domain in which the magnetic domain is enlarged is also small. Less is. Conversely, when the reproducing power of the light beam is strong, the domain wall movement region becomes large, and the region where the magnetic domain is enlarged also becomes large, so that the modulation degree at which the reproduced signal is modulated by the meandering of the nonmagnetic region becomes large. .

Attention is paid to the degree of modulation of the reproduced signal whose amplitude is modulated by the meandering of the non-magnetic region, and a modulation frequency component corresponding to the meandering contained therein is extracted from the reproduced signal, and the amplitude level of the modulation frequency component is detected. Is done. The amplitude level of the modulation frequency component changes depending on the influence of the meandering of the non-magnetic region as described above, and the size of the domain wall moving region is detected according to the amplitude level of the modulation frequency component, The reproduction power of the light beam is controlled so that the magnetic domain movement region has an appropriate size.

According to a third aspect of the present invention, there is provided a reproducing power control method for reproducing data from a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. A method for controlling a reproducing power of a light beam applied to the magneto-optical recording medium, wherein a non-magnetic region is formed so as to meander along a land track or a groove track of the magneto-optical recording medium; Extracting a modulation frequency component corresponding to the meandering of the non-magnetic region from a reproduction signal obtained from reflected light of the beam from the magneto-optical recording medium, detecting the amplitude level thereof,
The reproducing power of the light beam is controlled using the detection level.

According to the reproducing power control method of the third aspect, the amplitude level of the modulation frequency component corresponding to the meandering of the non-magnetic region is detected from the reproduced signal whose amplitude is modulated according to the meandering of the non-magnetic region. Then, based on the detected amplitude level of the modulation frequency component, the reproduction power of the light beam is controlled so that the domain wall movement region has an optimum size.

Thus, based on the amplitude level of the modulation frequency component due to the meandering of the nonmagnetic region detected from the reproduction signal, the domain wall motion region is always kept at an appropriate size during reproduction so as to maintain the proper size. The reproduction power of the beam can be controlled.

According to a fifth aspect of the present invention, there is provided a reproducing apparatus for a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. In the magnetic recording medium, a non-magnetic region is formed so as to meander along a land track or a groove track, and light beam irradiation means for irradiating the magnetic layer of the magneto-optical recording medium with a light beam. A reproduction signal forming unit for forming a reproduction signal in accordance with a reflected light of the light beam irradiated by the light beam irradiation unit from the magneto-optical recording medium; and Extracting means for extracting a modulation frequency component corresponding to the meandering of the non-magnetic region; and a level detecting means for detecting an amplitude level of the modulation frequency component extracted by the extracting means. A reproducing power error signal generating means for forming a reproducing power error signal used for controlling a reproducing power of the light beam based on a detection level from the level detecting means; and the reproducing from the error signal generating means. Light beam control means for controlling a reproduction power of the light beam according to a power error signal.

According to the reproducing apparatus of the fifth aspect,
The amplitude level of the modulation frequency component corresponding to the meandering of the non-magnetic region is detected from the reproduction signal by the level detection means, and reproduction based on the amplitude level of the modulation frequency component is performed so that the domain wall motion region has an optimum size. A power error signal is generated by a reproduction power error signal generating means. Based on the reproduction power error signal from the reproduction power error signal generation unit, the light beam control unit controls the reproduction power of the light beam irradiated from the light beam irradiation unit.

Thus, based on the amplitude level of the modulation frequency component due to the meandering of the non-magnetic region detected from the reproduction signal, the size of the domain wall motion region is always maintained at an appropriate size during reproduction. Then, the reproducing power of the light beam can be controlled. Therefore, the optimization of the light beam can be performed reliably and appropriately, and the reproduction of the data from the magneto-optical recording medium can be always performed well.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a reproducing power detecting method, a reproducing power detecting apparatus, a reproducing power controlling method, a reproducing power controlling apparatus and a reproducing apparatus according to the present invention; The embodiment described below has at least a domain wall motion layer, a switching layer,
This is an example in the case of using the above-mentioned DWDD magneto-optical disk including a magnetic recording layer.

[Outline] First, an outline of the present invention will be described with reference to FIGS. FIG. 4 shows the DWD
FIG. 4 is a diagram for explaining data reproduction from a D-type magneto-optical disk and a DWDD magneto-optical disk. The DWDD magneto-optical disk includes a so-called land recording disk for recording data on a land track, a so-called groove recording disk for recording data on a groove track, and data recording on both a land track and a groove track. There is a disk to do.

Land tracks and groove tracks are formed, for example, in a spiral or concentric manner on a magneto-optical disk. As shown in FIG.
Magnetic domain separation regions (non-magnetic regions) SP are formed on both sides of the land track or the groove track in the radial direction of the disk along the land track or the groove track.

That is, if the magneto-optical disk of the DWDD system is a land recording disk, the magnetic domain separation region SP is formed in the groove portion, and if the magneto-optical disk is a groove recording disk, the magnetic domain separation region SP is formed in the land portion. You.
Then, the magnetic domain separation region SP irradiates, for example, a light beam (laser beam) of a minute spot between a data recording track and a data recording track of a DWDD disk to thereby generate a magnetic field in the irradiated portion. The characteristic is extinguished to form.

The reason why the magnetic domain separation area SP is provided between the tracks is to prevent the adjacent tracks from affecting each other. In the following, for simplicity of explanation, the DWDD magneto-optical disk used will be described as a land-recording disk in which data is recorded on one spiral land track.

Then, as shown in FIG. 4, a land track T
The light spot 50 on the R is relatively moved in the direction indicated by the arrow id as the magneto-optical disk rotates. Further, the domain wall motion isotherm 60 indicates an area where the temperature has risen by the irradiation of the light beam until the domain wall motion occurs, and the inner side of the domain wall motion isotherm 60 indicates the region where the domain wall motion occurs. This is the domain wall movement region where the temperature has risen.

When the domain wall motion isotherm 60 reaches the domain wall of the magnetic domain 41 in FIG. 4, the domain wall of the magnetic domain 41 moves in the direction indicated by the arrow kd, and the magnetic domain 41 moves, for example, to the tip of the arrow kd. The data recorded here can be satisfactorily read from the enlarged magnetic domain 41.

FIG. 5 illustrates a reproduction signal RF when data is reproduced from a DWDD magneto-optical disk in which magnetic domain separation areas SP are provided on both sides of a land track as shown in FIG. FIG.

As shown in FIG. 4, the land track TR
In the case where the magnetic domain separation regions SP are provided on both sides in the radial direction of the land track TR and the domain wall motion isotherm 60 reaches the magnetic domain separation regions SP at both ends of the land track TR, the magnetic domain separation regions SP Thus, the recorded data can be reproduced without being affected by the neighboring land tracks. Further, each magnetic domain of the land track cannot be expanded in the radial direction of the disk until it exceeds the magnetic domain separation region SP. Therefore, FIG.
As shown in the figure, a reproduced signal RF having a so-called eye pattern having a substantially constant amplitude level is obtained.

However, the magnetic domain separation region SP is, for example,
In the case of meandering by changing the width and position in the radial direction of the magneto-optical disk, if the domain wall motion isotherm reaches the magnetic domain separation region SP, the reproduction signal R
The amplitude level of F is modulated according to the meandering of the magnetic domain separation region SP.

FIG. 6 is a view for explaining a DWDD magneto-optical disk formed so that the magnetic domain separation area SP is meandering. FIG. 7 is a diagram illustrating the magnetic domain separation area SP formed so as to meander. Reproduction signal RF when data is reproduced from a DWDD magneto-optical disk
FIG.

For example, as shown in FIG. 6, the magnetic domain separation area SP is formed to meander so as to change its position in the radial direction of the disk. Thus, the reproduction signal R from the magneto-optical disk in which the magnetic domain separation region SP is formed to meander.
The amplitude level of F is such that the domain wall motion isotherm is
, Modulation is performed depending on the width of the magnetic domain, as shown in FIG. That is, the amplitude level of the reproduction signal RF is modulated according to the meandering of the magnetic domain separation region SP.

However, as described above, the magnetic domain separation region SP
Is meandered, and the amplitude level of the reproduction signal RF is affected by the meandering of the magnetic domain separation region SP when the magnetic domain wall movement isotherm reaches the magnetic domain separation region SP. . When the reproducing power of the light beam is not sufficient and the domain wall motion isotherm does not reach the domain separation area SP, the domain where domain wall movement occurs is small, and the amplitude level of the reproduction signal RF is The meandering of the area SP is not greatly affected.

FIG. 8 is a diagram for explaining the meandering of the magnetic domain separation region SP and the domain wall movement isotherm. As shown in FIG. 8, when the magnetic domain separation region SP is meandering, if the reproduction power of the light beam is low, the temperature rises until domain wall movement occurs, as indicated by the domain wall movement isotherm 61. The domain wall movement region on the magneto-optical disk is relatively small, and even if the domain wall is moved and the magnetic domain is expanded, the radial width of the expanded magnetic domain in the magneto-optical disk is limited by the magnetic domain separation. Since the amplitude does not reach the area SP, the amplitude level of the reproduction signal RF is not much affected by the meandering of the magnetic domain separation area SP.

On the other hand, when the reproducing power of the light beam is relatively high, as shown by the domain wall motion isotherm 62, the domain wall motion region on the magneto-optical disk, which has risen to the temperature until the domain wall motion occurs, If the domain wall is relatively large and the magnetic domain wall is moved to expand the magnetic domain, the radial width of the expanded magnetic domain in the magneto-optical disk is changed to the magnetic domain separation area S.
P, the amplitude level of the reproduction signal RF is affected by the meandering of the magnetic domain separation region SP,
Amplitude modulation by meandering.

As described above, when the magnetic domain separation regions SP provided on both sides of the land track meander, the amplitude level of the reproduction signal RF is such that the domain wall movement isotherm reaches the magnetic domain separation region SP. In this case, modulation is performed depending on the width of a magnetic domain (domain) expanded by domain wall motion. As described with reference to FIG. 8, the amplitude level of the modulation frequency component corresponding to the meandering of the magnetic domain separation region SP included in the reproduction signal RF is a magneto-optical disk having a domain wall moving isotherm that varies depending on the reproduction power of the light beam. Is determined by the radial width of.

The present invention has been made by paying attention to this point, and the magnetic domain separation region is formed to meander on a DWDD magneto-optical disk, and the magnetic domain separation region included in the reproduction signal RF is meandered. By detecting the amplitude level of the frequency component modulated according to the size of the domain wall movement region, which is the region that has risen to the temperature at which the magnetic domain movement occurs,
That is, the size (aperture diameter) of the domain wall motion isotherm is detected, and the reproducing power of the light beam is controlled so that the size of the domain wall motion isotherm becomes appropriate.

[Recording / Reproducing Apparatus] Next, a recording / reproducing apparatus for a magneto-optical disk to which an embodiment of the reproducing apparatus according to the present invention is applied will be described. FIG. 1 is a block diagram for explaining a recording / reproducing apparatus according to this embodiment.

In FIG. 1, the disk 100 has a DWD
This is a D-type land-recording magneto-optical disk, which can rewrite data. As described above, the magneto-optical disk 100 has the magnetic domain separation regions (non-magnetic regions) SP on both sides of the land track as shown in FIG.
Are formed so as to meander (wobble).

In this embodiment, the magnetic domain separation region S
P is meandering in the radial direction of the magneto-optical disk, for example, so that the position can be changed.
The meandering frequency of the magnetic domain separation region SP is set to be lower than the frequency of the magnetic domain recorded in the magnetic recording layer at high density in the track direction (track scanning direction).
In this embodiment, the magneto-optical disk 100
In the land track, for example, data such as audio data, text data, or image data,
Description will be made on the assumption that high-density recording has already been performed.

As shown in FIG. 1, the recording / reproducing apparatus of this embodiment in which the magneto-optical disk 100 is loaded comprises a spindle motor 11, an optical pickup unit 12,
F circuit 13, servo circuit 14, data demodulation circuit 15, data ECC (Error Correcting Co.)
de) Decoding circuit 16, output terminal 17, address demodulation circuit 18, address ECC decoding circuit 19, control unit 2
0, laser power control circuit 21, LD drive circuit 2
2, an input terminal 31, an ECC adding unit 32, a data modulation circuit 33, a magnet drive circuit 34, and an external magnetic field generating coil 35.

The pickup unit 12 includes, for example, a light source for a light beam such as a laser diode, optical components such as a choline meter lens, an objective lens, a polarizing beam splitter, and a cylindrical lens, a four-division photodetector, and the optical pickup unit 12 as a magneto-optical disk 100. And a thread motor for moving in the radial direction. The control unit 20 includes a CPU, a ROM, an R
The microcomputer is provided with an AM and the like, and controls each unit of the recording / reproducing apparatus according to the present embodiment.

The recording / reproducing apparatus of this embodiment reproduces data recorded on the magneto-optical disk 100 by a user through a key operation unit or a remote commander connected to the control unit 20. When the mode is set, the data recorded on the magneto-optical disk 100 is reproduced as follows.

The magneto-optical disk 100 is rotated by a spindle motor 11. The spindle motor 11 is controlled by a control signal from the servo circuit 14 so as to maintain a specified rotation speed. Then, the optical pickup unit 12 irradiates the magneto-optical disk 100 with a light beam, and receives the reflected light with a four-divided photodetector. The four-segment photodetector photoelectrically converts the reflected light,
A signal corresponding to the reflected light is supplied to the RF circuit 13.

The RF circuit 13 forms a reproduction signal RF, a tracking error signal, a focus error signal, and the like from a signal corresponding to the light reflected from the optical pickup unit 12. The tracking error signal and the focus error signal are supplied to the servo circuit 14. The servo circuit 14
A tracking servo signal and a focus servo signal are formed based on the tracking error signal and the focus error signal from the RF circuit 13, and are supplied to the optical pickup unit 12.

As a result, the light beam emitted from the optical pickup unit 12 can scan the track of the magneto-optical disk 100 accurately with a light beam of a light spot of a good size.

On the other hand, the reproduction signal RF formed in the RF circuit 13 is supplied to a data demodulation circuit 15, an address demodulation circuit 18, and a laser power control circuit 21. In the recording / reproducing apparatus of this embodiment, the reproducing power of the light beam emitted from the optical pickup unit 12 is controlled by the reproducing power error signal ER formed by the laser power control circuit 21 so as to optimize the reproducing power. Like that.

The laser power control circuit 21 employs the reproduction power control method and the reproduction power control device according to the present invention, and includes the reproduction power detection device according to the present invention to which the reproduction power detection method according to the present invention is applied. It is a thing.

FIG. 2 is a block diagram for explaining the laser power control circuit 21 of the recording / reproducing apparatus shown in FIG. As shown in FIG. 2, the laser power control circuit 21 of this embodiment includes a band-pass filter (BPF in FIG. 2) 211, a detection circuit 212, a comparison circuit 213, and an appropriate level holding unit 214. It is provided with.

The reproduction signal RF from the RF circuit 13 is supplied to the band pass filter 211 of the laser power control circuit 21. The band-pass filter 211 outputs the reproduced signal RF
, A signal in the meandering frequency band of the magnetic domain separation region SP is extracted. That is, the bandpass filter 211 extracts the modulation frequency component Cr from the reproduction signal RF that is amplitude-modulated according to the meandering of the magnetic domain separation region SP. Thus, the band pass filter 211 has a function as a modulation frequency component extraction unit.

The modulation frequency component Cr extracted by the band pass filter 211 is supplied to the detection circuit 212. The detection circuit 212 detects the modulation frequency component Cr,
A detection output Lb corresponding to the level of the modulation frequency component is output. As described above, the detection circuit 212 is used as a level detection circuit, and has a function as a level detection unit for a modulation frequency component.

The detection output L from the detection circuit 212
When the level of “b” is high, a large number of frequency components amplitude-modulated by the meandering of the magnetic domain separation region SP are included, and it can be detected that the size of the domain wall motion region is large. Conversely, when the level of the detection output Lb from the detection circuit 212 is low,
It is possible to detect that the frequency component amplitude-modulated by the meandering of the magnetic domain separation region SP is small, and that the size of the domain wall movement region is small. Thus, the detection output L from the detection circuit 212 is
In accordance with the level b, the size of the domain wall movement region, that is, the magnitude of the reproducing power of the light beam can be detected.

The detection output Lb from the detection circuit 212 is supplied to a comparison circuit 213. This comparison circuit 213 includes
As shown in FIG. 2, the appropriate level Et of the modulation frequency component is supplied from the appropriate level holding unit 214. The appropriate level Et indicates an appropriate level of a modulation frequency component of the reproduction signal RF whose amplitude is modulated by meandering of the magnetic domain separation region SP, and is predetermined.

FIG. 3 shows a predetermined appropriate level Et.
FIG. 9 is a diagram for explaining comparison processing in a comparison circuit 213. The appropriate level Et is detected in advance by performing a test reproduction using a magneto-optical disk in which the magnetic domain separation regions SP meander on both sides of the land track TR.

That is, test reproduction is performed using a magneto-optical disk in which the magnetic domain separation region SP is formed to meander, while gradually increasing the reproduction power of the light beam. Then, as shown in FIG. 3, the error rate (bit error rate) BER of the reproduced data and the magnetic domain separation region SP
Signal RF that is amplitude-modulated by meandering
And the amplitude level MF of the modulation frequency component.

In this case, as can be seen from FIG. 3, as the reproducing power of the light beam increases, the size of the domain wall movement region also increases, so that the amplitude level MF of the modulation frequency component increases. When the reproducing power of the light beam increases to a certain extent and the domain wall movement region reaches the meandering magnetic domain separation region SP on both sides of the land track, the domain wall movement region is moved in the radial direction of the magneto-optical disk by the magnetic domain separation region SP. Does not spread, the amplitude level of the modulation frequency component becomes substantially constant.

The error rate BE of the reproduced data at this time is
R decreases as the reproducing power of the light beam increases, but when the reproducing power increases to some extent,
As described above, the error rate BER of the reproduced data increases due to the influence of the attenuation of the Kerr effect and the temperature characteristics of the leakage magnetic field from the magnetic domain around the light spot.

Therefore, the amplitude level of the modulation frequency component when the error rate BER of the reproduced data becomes the lowest is detected as an appropriate level Et.
To be held.

The comparison circuit 213 is connected to the detection circuit 21
2 is compared with the appropriate level Et from the appropriate level holding unit 214. If the detected output Lb is higher than the appropriate level Et, a reproduction power error indicating that the reproduction power of the light beam is strong. The signal ER is output, and when the detection output Lb is lower than the appropriate level Et, a reproduction power error signal ER indicating that the reproduction power of the light beam is weak is output.

The reproduction power error signal ER output from the comparison circuit 213 is supplied to the LD drive circuit 22. The LD drive circuit 22 receives the reproduction power error signal ER from the comparison circuit 213 of the laser power control circuit 21.
In response to the above, a signal for driving the light source of the light beam of the optical pickup unit 12 is formed and supplied to the light source of the light beam of the optical pickup unit 12.

As a result, the reproduction power of the light beam emitted from the optical pickup section 12 is controlled by the reproduction power error signal from the laser power control circuit 21, so that the reproduction power of the light beam can be optimized quickly and appropriately. Is to be. That is, the amplitude level of the modulation frequency component included in the reproduction signal RF that is amplitude-modulated by the meandering of the magnetic domain separation region SP is adjusted to the appropriate level Et.
Thus, the reproducing power of the light beam is controlled so that the data can always be satisfactorily reproduced at the time of reproducing.

Then, as described above, the reflected light of the light beam, which is controlled so that the reproduction power is always appropriate, is calculated from the reflected light.
The reproduction signal RF formed in the F circuit 13 is also supplied to a data demodulation circuit 15 and an address demodulation circuit 18, and the data demodulation circuit 15 shapes the waveform of the reproduction signal RF supplied thereto to “0”. The data is converted to "1" data and supplied to the ECC decoding circuit 19. The ECC decoding circuit 19 performs error detection and error correction, restores the original data, and outputs this through the data output terminal 17.

The address demodulation circuit 18 extracts address data from the supplied reproduction signal RF. In this embodiment, the address data is recorded by providing, for example, minute concave portions (pits) on the track of the magneto-optical disk 100, and the address data can be extracted according to a change in the reproduction signal RF. It has been like that.

The address demodulation circuit 18 demodulates the extracted address data and supplies the demodulated address data to the address ECC circuit 19. The address ECC demodulation circuit 19 performs error detection and error correction on the demodulated address data, and supplies the restored address data to the control unit 20.

The control unit 20 obtains the position on the magneto-optical disk 100 where the light beam is scanning based on the supplied address data, and sets the target on the magneto-optical disk 100 based on the reproduced address data. A control signal including information for instructing movement of the scanning position of the light beam and the like is supplied to the servo circuit 14 so as to scan the track.

The servo circuit 14 forms a control signal for changing the scanning position of the light beam from the optical pickup unit 12 based on the control signal from the control unit 20, and sends the control signal to the optical pickup unit 12. Supply. As a result, the target data recorded on the magneto-optical disk 100 can be read.

When the recording / reproducing apparatus of this embodiment is in the reproducing mode for reproducing the data recorded on the magneto-optical disk 100, the reproduced signal RF whose amplitude is modulated by the meandering of the magnetic domain separation area SP. The reproducing power of the light beam can be quickly and appropriately controlled in accordance with the amplitude level of the modulation frequency component included in the data, so that the data recorded on the magneto-optical disk 100 can be reproduced and used satisfactorily at any time. be able to.

It should be noted that the recording / reproducing apparatus of this embodiment
Data can be magneto-optically recorded on a magneto-optical disk. Therefore, when the recording / reproducing apparatus of this embodiment is in a recording mode in which data input through the input terminal 31 is recorded on the magneto-optical disk 100, data is written to the magneto-optical disk as follows. Record at 100.

That is, the data input through the input terminal 31 is supplied to the ECC adding circuit 32, where the data is added with an error correction code, and then supplied to the data modulating circuit 33. The data modulation circuit 33 modulates the data to which the error correction code has been added, for example, by an appropriate EFM modulation method when recording the data on the magneto-optical disk 100, and supplies this to the magnet drive circuit.

The magnet drive circuit 34 drives the external magnetic field generating coil 35 according to the recording data.
As shown in FIG. 1, the external magnetic field generating coil 35 is provided on the extension line of the optical pickup unit 12.
, And can move in the radial direction of the magneto-optical disk 100 in synchronization with the optical pickup unit 12. Then, the external magnetic field generating coil 35 generates + (plus) and − (minus) recording magnetic fields according to the recording data from the magnet drive circuit 34.

At this time, each section is controlled by the control section 20 using the address data read from the magneto-optical disk 100 as a reference as described above, and the magneto-optical of the light beam emitted from the optical pickup section 12 is controlled. The irradiation position on the disk 100 and the external magnetic field generating coil 35
The position on the magneto-optical disk 100 to which the magnetic field is applied is adjusted, and, for example, the control unit 2
In response to the control from 0, the laser power control circuit 21 controls the power of the light beam from the optical pickup unit 12 to a power suitable for recording.

The magneto-optical disk 100 is designed to rotate at a predetermined rotation speed.
From the target position on the external magnetic field generating coil 3
The recording mark corresponding to the polarity of No. 5 is formed on the land track, and the recording data is recorded on the land track of the magneto-optical disk 100 at a high density.

In the above-described embodiment, the magnetic domain separation area SP is described as being meandering by changing its position in the radial direction of the magneto-optical disk. However, the present invention is not limited to this. Absent. For example, the magnetic domain separation region may be formed to meander by changing the radial width of the magneto-optical disk.

For example, in the case of a land-recording magneto-optical disk, the magnetic domain separation region is made non-magnetic in a groove portion formed so as to meander, or in the case of a groove recording magneto-optical disk, It can be formed by making the land portion formed so as to meander nonmagnetic.

In addition, for example, in the case of a magneto-optical disk for land recording, when the groove portion is not formed to meander, a light beam of a minute spot irradiated to make the groove portion non-magnetic is used. By irradiating by changing the irradiation position in the radial direction of the disc,
In the groove, the position of the magneto-optical disk can be changed in the radial direction to form a magnetic domain separation region meandering.

Further, if the power of the light beam of the minute spot to be irradiated to make the groove portion non-magnetic is irradiated at the groove portion while modulating it at a predetermined frequency, magneto-optical The radial width of the disk may be varied to form a meandering magnetic domain separation region.

Similarly, in the case of a grooved magneto-optical disk, if the land portion is not formed so as to meander, the position is changed in the radial direction of the magneto-optical disk within the land so as to meander. A magnetic domain separation region can be formed, and a magnetic domain separation region can be formed in a land where the width of the magneto-optical disk in the radial direction is changed so as to meander.

As described above, the magnetic domain separation region is formed by irradiating a minute spot light beam with an irradiation power of such a degree as to lose the magnetic properties of the magnetic layer. Other methods such as removing the magnetic layer in the magnetic domain separation region may be used. In other words, in the magnetic domain separation region, a portion (non-magnetic portion) whose magnetic properties are lost may be formed between tracks for recording data, and various methods for realizing this can be used. Can be used.

In the above-described embodiment, the description has been made assuming that the address data is recorded in advance on the magneto-optical disk 100 by pits. However, the address data is formed by the wobbling of the track.
Of course, it may be recorded.

That is, the address data may be recorded on the magneto-optical disk by meandering the meandering groove portion or land portion where the magnetic domain separation region is formed. As described above, when the address data is recorded by the meandering of the groove portion or the land portion, if the push-pull signal formed in the RF circuit is supplied to the address demodulation circuit, the data is recorded as the meandering of the track. Address data is extracted.

Therefore, the meandering of the magnetic domain separation region may correspond to the meandering for recording information for data detection such as address data and other information on the magneto-optical disk.

Of course, in order to control the reproduction power of the light beam, the meandering frequency of the magnetic domain separation region may be determined, and the meandering may be performed at the determined frequency.

In the above embodiment, the present invention is applied to a recording / reproducing apparatus.
Of course, the present invention can be applied to a playback-only device.

Further, the magneto-optical disk according to the above-described embodiment has been described as being of the land recording type, but the magneto-optical disk may of course be of the groove recording type.
Further, data that can be recorded on both the land track and the groove track may be used. In any case, the magnetic domain separation region may be formed to meander on both sides of the track on which data is recorded.

[0092]

As described above, according to the present invention, the amplitude is modulated according to the meandering of the magnetic domain separation region (non-magnetic region) formed so as to meander adjacent to the track where data is recorded. In accordance with the amplitude level of the modulation frequency component of the reproduced signal, the reproduction power of the light beam can be controlled so as to always keep the optimal power.

Further, since data recorded on a magneto-optical recording medium capable of high-density recording can be read and used at any time without fail, the reliability of data reproduction can be improved.

Further, the use of a magneto-optical recording medium capable of high-density recording can be promoted, for example, the range of use of a magneto-optical recording medium capable of high-density recording can be expanded.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a recording / reproducing apparatus to which an embodiment of a reproducing apparatus according to the present invention is applied.

FIG. 2 is a block diagram for explaining a laser power control circuit of the recording / reproducing apparatus shown in FIG.

FIG. 3 illustrates a relationship between a reproduction power of a light beam, an amplitude level of a modulation frequency component included in a reproduction signal that is amplitude-modulated according to meandering of a magnetic domain separation region, and an error rate of reproduction data. FIG.

FIG. 4 is a diagram for explaining reproduction of data from a DWDD magneto-optical disk and from a DWDD magneto-optical disk.

FIG. 5 is a diagram for explaining a reproduction signal when data is reproduced from the DWDD magneto-optical disk shown in FIG. 4;

FIG. 6 is a view for explaining a DWDD magneto-optical disk formed so as to meander the magnetic domain separation region SP.

FIG. 7 is a diagram for explaining a reproduction signal when data is reproduced from a DWDD magneto-optical disk in which the magnetic domain separation regions shown in FIG. 6 are formed to meander.

FIG. 8 is a diagram for explaining a light spot and a magnetic domain movement region when a light beam is applied to a DWDD magneto-optical disk in which a magnetic domain separation region is formed to meander.

FIG. 9 is a diagram for explaining a DWDD type magneto-optical disk.

FIG. 10 is a diagram for explaining a principle of reproducing data from the magneto-optical disk shown in FIG. 9;

[Explanation of symbols]

11: spindle motor, 12: optical pickup unit, 1
3 RF circuit, 14 servo circuit, 15 data demodulation circuit, 16 ECC (Error Correcting)
Code) decoding circuit, 17 output terminal, 18 address demodulation circuit, 19 address ECC decoding circuit, 20 control unit, 21 laser power control circuit, 22 L
D drive circuit, 31 input terminal, 32 ECC addition circuit, 33 modulation circuit, 34 magnet drive circuit, 35 external coil for generating magnetic field, 100 magnetooptical disk, 211 bandpass filter, 212 detection Circuit, 213: comparison circuit, 214: proper level holding unit

Claims (5)

[Claims] 1. A reproducing power of a light beam applied to a magneto-optical recording medium for reproducing data from a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. Wherein a non-magnetic region is formed so as to meander along a land track or a groove track of the magneto-optical recording medium, and is obtained from reflected light of the light beam from the magneto-optical recording medium. A modulation frequency component corresponding to the meandering of the non-magnetic region is extracted from the reproduction signal, the amplitude level is detected, and the reproduction power of the light beam is detected based on the detection level. Power detection method. 2. The reproducing power of a light beam applied to a magneto-optical recording medium in order to reproduce data from a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. Wherein the non-magnetic region is formed on the magneto-optical recording medium so as to meander along a land track or a groove track, and the light beam is transmitted from the magneto-optical recording medium. Extracting means for extracting a modulation frequency component corresponding to the meandering of the non-magnetic region from a reproduction signal obtained from the reflected light; detecting an amplitude level of the modulation frequency component extracted by the extraction means; and And a detecting means for detecting a reproducing power of the light beam. 3. The reproducing power of a light beam applied to a magneto-optical recording medium in order to reproduce data from a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. The non-magnetic region is formed so as to meander along a land track or a groove track of the magneto-optical recording medium, and is obtained from reflected light of the light beam from the magneto-optical recording medium. Extracting a modulation frequency component corresponding to the meandering of the non-magnetic region from a reproduction signal, detecting an amplitude level thereof, and controlling a reproduction power of the light beam using the detected level. Control method. 4. A reproducing power of a light beam applied to the magneto-optical recording medium in order to reproduce data from the magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall. A non-magnetic region is formed on the magneto-optical recording medium so as to meander along a land track or a groove track, and the light beam is transmitted from the magneto-optical recording medium. Extracting means for extracting a modulation frequency component corresponding to the meandering of the non-magnetic region from a reproduced signal obtained from reflected light; level detecting means for detecting an amplitude level of the modulation frequency component extracted by the extracting means; A reproduction power for forming a reproduction power error signal used for controlling the reproduction power of the light beam based on the detection level from the detection means. A reproduction power control device comprising: an error signal generation unit. 5. A reproducing apparatus for a magneto-optical recording medium from which recorded main information is read by expanding a magnetic domain by moving a domain wall, wherein the magneto-optical recording medium includes a land track or a groove track. A light beam irradiating means for irradiating the magnetic layer of the magneto-optical recording medium with a light beam, wherein the light beam is irradiated by the light beam irradiating means; Reproducing signal forming means for forming a reproducing signal in accordance with the reflected light from the magneto-optical recording medium; and extracting a modulation frequency component corresponding to the meandering of the non-magnetic region from the reproducing signal from the reproducing signal forming means. Extraction means for detecting, an amplitude level of the modulation frequency component extracted by the extraction means, a level detection means, and a detection level from the level detection means A reproducing power error signal generating means for forming a reproducing power error signal used for controlling a reproducing power of the light beam, based on the reproducing power error signal from the error signal generating means. A reproducing apparatus, comprising: a light beam control unit for controlling a reproducing power.