JPH11259923A - Magneto-optical record medium discrimination circuit, device containing it and discrimination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly discriminate a kind of a loaded magneto-optical record medium. SOLUTION: A first magneto-optical signal L1 is detected in the state applying a first directional magnetic field to the magneto-optical record medium (S2, S3), and a second magneto-optical signal L2 is detected in the state applying a second directional magnetic field (S4, S5). Thereafter, its difference S=L1-L2 is operated from two detected magneto-optical signals L1, L2 (S6), and when the operation result S is positive, it is the first kind magneto-optical record medium is discriminated (S8), and when the operation result S is negative, it is the second kind magneto-optical record medium is discriminated (S9).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a circuit for discriminating a magneto-optical recording medium for recording a signal in a perpendicular magnetic domain and reproducing the signal using a laser beam or a laser beam and a magnetic field. It relates to a playback device.

[0002]

2. Description of the Related Art Magneto-optical recording media have attracted attention as rewritable, large-capacity, and highly reliable recording media, and have begun to be put to practical use as computer memories and the like. Recently, the recording capacity is 6.0 Gby.
The standardization of the magneto-optical recording medium of tes has been promoted and is being put to practical use. Reproduction of signals from such a high-density magneto-optical recording medium is performed by irradiating a laser beam to transfer magnetic domains of the recording layer of the magneto-optical recording medium to the reproducing layer,
A detection window is formed in the reproducing layer so that only the transferred magnetic domain can be detected, and an MSR (Magnetically Super) for detecting the transferred magnetic domain from the formed detection window.
(resolution) method.

Further, a magnetic domain enlarging / reproducing technique for reproducing an signal by applying an alternating magnetic field in reproducing a signal from a magneto-optical recording medium and enlarging and transferring a magnetic domain of a recording layer to a reproducing layer by a laser beam and the alternating magnetic field has also been developed. Thus, a magneto-optical recording medium capable of recording and / or reproducing a signal of 14 Gbytes by using this technology has been proposed.

[0004]

However, when a signal is reproduced by the MSR method, only the laser beam is applied to the magneto-optical recording medium, and when the signal is reproduced by expanding the magnetic domain, the laser beam and the magnetic field are applied to the magneto-optical recording medium. Is applied or applied.
In addition, MSR (Magnetically Super)
The intensity of the laser light applied to the magneto-optical recording medium is different between when reproducing by the Resolution method and when reproducing by expanding the magnetic domain. Therefore, when it is not possible to determine whether the mounted magneto-optical recording medium is a magneto-optical recording medium that performs reproduction by the MSR method or a magneto-optical recording medium that performs reproduction by magnetic domain expansion, a laser beam having an optimum intensity cannot be set. When reproduction is performed by magnetic domain expansion, a magnetic field may not be applied in some cases, and there has been a problem that accurate signal reproduction and rapid signal reproduction are difficult.

Therefore, the present invention solves such a problem,
An object of the present invention is to provide a method and a circuit for determining a type of a magneto-optical recording medium, which can quickly determine the type of a mounted magneto-optical recording medium, and a reproducing apparatus using the same.

[0006]

The invention according to claim 1 is a discrimination circuit for discriminating the type of a magneto-optical recording medium by applying or irradiating a magnetic field and a laser beam to the magneto-optical recording medium. is there. According to the first aspect of the present invention, the type of the magneto-optical recording medium can be easily determined by applying or irradiating a magnetic field and a laser beam to the magneto-optical recording medium.

According to a second aspect of the present invention, there is provided a discriminating circuit for a magneto-optical recording medium including a magnetic field applying unit, an optical unit, and a discriminating unit. The magnetic field applying means applies a magnetic field in a first direction and a magnetic field in a second direction to the magneto-optical recording medium.
The optical means irradiates the magneto-optical recording medium with a laser beam, and detects a first magneto-optical signal from the magneto-optical recording medium in response to the application of the magnetic field in the first direction by the magnetic field applying means. Further, a second magneto-optical signal is detected from the magneto-optical recording medium in response to the application of the magnetic field in the second direction by the magnetic field applying means.

[0008] Further, the discriminating means inputs the first and second magneto-optical signals detected by the optical means. And the first
The difference between the first magneto-optical signal and the second magneto-optical signal is calculated, and if the calculation result is the first code, it is determined that the medium is the first type of magneto-optical recording medium, and the calculation result is the second code. If it is, it is determined that the medium is the second type of magneto-optical recording medium. According to a second aspect of the present invention, a type of a magneto-optical recording medium is determined by calculating a difference between two magneto-optical signals detected by applying magnetic fields in two directions. The magnetic material used for the magneto-optical recording medium is composed of an alloy of a transition metal and a rare earth metal, and the reproducing layer for detecting a signal is made of a magnetic material having a large content of a transition metal or a magnetic material having a large content of a rare earth metal. Either is used. Further, the Kerr rotation angle, that is, the polarity of the magnetic field dependence of the magneto-optical signal is opposite between the magnetic material having a large content of the transition metal and the magnetic material having a large content of the rare earth metal. Therefore, according to the second aspect of the present invention, the type can be reliably identified only by applying or irradiating a magnetic field and a laser beam without rotating the mounted magneto-optical recording medium.

According to a third aspect of the present invention, there is provided a discriminating circuit for a magneto-optical recording medium including a magnetic field applying unit, an optical unit, and a discriminating unit. The magnetic field applying means applies a magnetic field in a first direction and a magnetic field in a second direction to the magneto-optical recording medium.
The optical means irradiates the magneto-optical recording medium with a laser beam, detects a first magneto-optical signal from the magneto-optical recording medium in response to the application of the magnetic field in the first direction, and 2
The second magneto-optical signal is detected from the magneto-optical recording medium in response to the application of the magnetic field in the direction of.

The discriminating circuit inputs the first and second magneto-optical signals detected by the optical means, calculates a difference between the first and second magneto-optical signals, and calculates the difference. If the result is in the range of -0.1 to +0.1 degrees, it is determined to be the third type of magneto-optical recording medium, and if the calculation result is a value outside the above range and the first sign, It is determined to be the first type of magneto-optical recording medium, and if the result of the operation is a value outside the above range and the second code, it is determined to be the second type of magneto-optical recording medium.

According to the third aspect of the present invention, the first
When the first and second magneto-optical signals are detected by applying a magnetic field in the direction of the second direction and a magnetic field in the second direction, the first, second, and third magneto-optical recording mediums are detected. The type of magneto-optical recording medium can be determined. According to a fourth aspect of the present invention, in the discriminating circuit according to the second or third aspect, the magnetic field in the second direction is a magnetic field in a direction opposite to the magnetic field in the first direction. .

According to the fourth aspect of the invention, magnetic fields in opposite directions are applied to the magneto-optical recording medium to detect two magneto-optical signals, and a magneto-optical recording is performed based on a difference between the detected magneto-optical signals. Since the type of medium is determined, the polarity or the difference in polarity and range can be reliably detected, and as a result,
The type of the magneto-optical recording medium can also be reliably determined. According to a fifth aspect of the present invention, in the determination circuit according to the fourth aspect, the magnetic field in the first direction is a magnetic field perpendicular to the magneto-optical recording medium.

According to the fifth aspect of the present invention, the magnetic field applied when detecting the first and second magneto-optical signals is applied perpendicularly to the magneto-optical recording medium. The magnetization of the reproducing layer irradiated with the laser light to be detected is directed in a direction that most easily exerts a magneto-optical effect on the irradiated laser light, and an accurate magneto-optical signal is obtained. Can be determined.

According to a sixth aspect of the present invention, in the discrimination circuit according to any one of the second to fifth aspects, the first type of magneto-optical recording medium is characterized in that the transition metal has rare-earth magnetization. This is a discrimination circuit which is a magneto-optical recording medium having a reproducing layer larger than the magnetization of metal. According to the invention described in claim 6, it is possible to distinguish between a magneto-optical recording medium having a reproducing layer in which the magnetization of the transition metal is larger than the magnetization of the rare-earth metal and other magneto-optical recording media.

According to a seventh aspect of the present invention, in the discrimination circuit according to any one of the second to fifth aspects, the first type of magneto-optical recording medium is characterized in that the transition metal has rare-earth magnetization. A discrimination circuit which is a magneto-optical recording medium having a reproducing layer larger than the magnetization of a metal, and a second type of magneto-optical recording medium is a magneto-optical recording medium having a reproducing layer whose magnetization of a rare earth metal is larger than that of a transition metal. It is.

According to the invention described in claim 7, a magneto-optical recording medium having a reproducing layer in which the transition metal has a magnetization larger than that of the rare earth metal, and a reproducing layer in which the rare earth metal has a magnetization larger than the transition metal. And the magneto-optical recording medium can be determined. According to an eighth aspect of the present invention, there is provided a reproducing apparatus for a magneto-optical recording medium including the discriminating circuit according to the second aspect, wherein the reproducing of the magneto-optical recording medium includes a magnetic field applying means driving circuit and a laser driving circuit. Device.

In the magnetic field applying means driving circuit, the discriminating means is a first circuit.
If it is determined that the recording medium is of the type, the magnetic field applying means is driven to generate an alternating magnetic field, and the determination means
If the type of magneto-optical recording medium is determined, the magnetic field applying means is driven so as not to generate a magnetic field. The laser drive circuit drives the laser light generating means in the optical means so as to generate laser light of the first intensity when the determining means determines that the medium is the first type of magneto-optical recording medium. If the means determines that the medium is the second type of magneto-optical recording medium, the laser light generating means in the optical means is driven so as to generate laser light of the second intensity.

According to the invention described in claim 8, the magnetic field applying means and the laser light generating means are driven in accordance with the type of the magneto-optical recording medium determined by the determining circuit, so that the mounted magneto-optical recording medium can be used. Suitable signal reproduction is possible.
According to a ninth aspect of the present invention, in the reproducing apparatus for a magneto-optical recording medium according to the eighth aspect, the laser beam of the first intensity does not transfer magnetic domains from the recording layer to the reproducing layer of the magneto-optical recording medium. It is a reproducing device that is an intense laser beam.

According to the ninth aspect of the present invention, the first
Is a laser beam of an intensity that does not transfer magnetic domains from the recording layer to the reproducing layer of the magneto-optical recording medium, so that the mounted magneto-optical recording medium reproduces signals by expanding the magnetic domains. In some cases, the magnetic domain of the recording layer can be further enlarged and transferred to the reproducing layer to reproduce a signal. According to a tenth aspect of the present invention, in the reproducing apparatus for a magneto-optical recording medium according to the eighth aspect, the laser beam of the first intensity does not transfer magnetic domains from the recording layer to the reproducing layer of the magneto-optical recording medium. The reproducing device is a laser beam of high intensity, and the laser beam of second intensity is laser light of such intensity that magnetic domains are transferred from the recording layer to the reproducing layer of the magneto-optical recording medium.

According to the tenth aspect of the present invention, the first intensity laser beam is a laser beam whose magnetic domain is not transferred from the recording layer to the reproducing layer of the magneto-optical recording medium.
Is a laser beam having an intensity that transfers magnetic domains from the recording layer to the reproducing layer of the magneto-optical recording medium, so that the mounted magneto-optical recording medium reproduces signals by expanding the magnetic domains. In the case of, the magnetic domain of the recording layer can be further enlarged and transferred to the reproducing layer to reproduce a signal, and the mounted magneto-optical recording medium can reproduce the signal by expanding the magnetic domain. When the recording medium is used, the signal can be reproduced by the super-resolution method.

The invention according to claim 11 is the third invention.
A reproducing apparatus for a magneto-optical recording medium including the discriminating circuit described in 1. above, which is a reproducing apparatus for a magneto-optical recording medium including a magnetic field applying unit driving circuit and a laser driving circuit. The magnetic field applying means driving circuit drives the magnetic field applying means to generate an alternating magnetic field when the determining means determines that the medium is the first type of magneto-optical recording medium. If it is determined that the medium is a magneto-optical recording medium, the magnetic field applying means is driven so as not to generate a magnetic field.

In the laser driving circuit, the discriminating means is a first
If the discrimination is made as the type of magneto-optical recording medium, the laser light generating means in the optical means is driven so as to generate the laser light of the first intensity, If the discrimination is made, the laser light generating means in the optical means is driven so as to generate the laser light of the second intensity, and if the discrimination means discriminates the third type of magneto-optical recording medium, the third light is output.
The laser light generating means in the optical means is driven so as to generate the laser light of the intensity.

According to the eleventh aspect of the present invention, the magnetic field applying means and the laser beam generating means are driven in accordance with the type of the magneto-optical recording medium determined by the determining circuit, so that the three types of mounted magneto-optical recording medium are driven. Signal reproduction suitable for a recording medium is possible. According to a twelfth aspect of the present invention, a magnetic field in a first direction and a magnetic field in a second direction are applied to a magneto-optical recording medium, and the magnetic field is detected from the magneto-optical recording medium in response to the magnetic field in the first direction. The difference between the first magneto-optical signal thus obtained and the second magneto-optical signal detected from the magneto-optical recording medium corresponding to the magnetic field in the second direction is calculated, and the calculation result is the first code. In this case, the discrimination method is the first type of magneto-optical recording medium, and if the calculation result is the second code, the second type of magneto-optical recording medium is determined.

According to a thirteenth aspect of the invention, a magnetic field in a first direction and a magnetic field in a second direction are applied to a magneto-optical recording medium, and the magnetic field in the magneto-optical recording medium corresponds to the magnetic field in the first direction. The difference between the first magneto-optical signal detected from the first magneto-optical signal and the second magneto-optical signal detected from the magneto-optical recording medium corresponding to the magnetic field in the second direction is calculated. If the angle is within the range of 1 to +0.1 degrees, it is determined that the medium is a third type of magneto-optical recording medium. If the calculation result is a value outside the above range and is the first sign, the first type of light is recorded. This is a method of determining a magneto-optical recording medium in which the discrimination is made as a magnetic recording medium, and when the calculation result is a value outside the above range and the second code, the discrimination is made as a second type of magneto-optical recording medium.

According to the twelfth aspect or the thirteenth aspect of the present invention, the detection is performed by applying the magnetic field in two directions.
Since the type of the magneto-optical recording medium is determined by calculating the difference between the two magneto-optical signals, the type of the magneto-optical recording medium can be reliably determined. According to a fourteenth aspect of the present invention, in the discrimination method according to the twelfth or thirteenth aspect, the first type of magneto-optical recording medium includes a reproducing layer in which the transition metal has a larger magnetization than the rare earth metal. This is a method for determining whether the medium is a magneto-optical recording medium.

According to the fourteenth aspect of the present invention, it is possible to discriminate a magneto-optical recording medium having a reproducing layer in which the magnetization of the transition metal is larger than that of the rare-earth metal from other magneto-optical recording media. The invention according to claim 15 is the invention according to claim 12.
Alternatively, in the determination method according to claim 13, the first
The type of magneto-optical recording medium is a magneto-optical recording medium having a reproducing layer in which the transition metal has a magnetization larger than that of the rare-earth metal, and the second type of magneto-optical recording medium has a rare-earth metal whose transition metal has a magnetization of the transition metal. This is a method for determining a magneto-optical recording medium having a reproducing layer larger than the magnetization.

According to the fifteenth aspect of the present invention, a magneto-optical recording medium having a reproducing layer in which the transition metal has a magnetization larger than that of the rare earth metal and a reproducing layer in which the rare earth metal has a magnetization larger than the transition metal. Discrimination with a magneto-optical recording medium,
Alternatively, a magneto-optical recording medium having a reproducing layer in which the magnetization of the transition metal is larger than that of the rare earth metal, a magneto-optical recording medium having a reproducing layer in which the magnetization of the rare earth metal is larger than the magnetization of the transition metal, and the other magneto-optical recording medium Can determine.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. With reference to FIG. 1, a cross-sectional structure of a magneto-optical recording medium that performs signal reproduction by magnetic domain expansion reproduction will be described. In the magneto-optical recording medium 10, an interference layer 2 made of SiN is formed on a transparent substrate 1 made of glass, polycarbonate, or the like.
A reproducing layer 3 made of GdFeCo is formed on the interference layer 2, a nonmagnetic layer 4 made of SiN is formed on the reproducing layer 3, and a recording layer 5 made of TbFeCo is formed on the nonmagnetic layer 4. It has a structure in which a protective layer 6 made of SiN is formed on the recording layer 5. In GdFeCo used for the reproducing layer 3 of the magneto-optical recording medium 10 that reproduces signals by magnetic domain expansion, the sublattice magnetization (hereinafter, simply referred to as “magnetization”) of FeCo, which is a transition metal, is larger than that of Gd, which is a rare earth metal. It is a magnetic material. A magnetic material having a large magnetization of the transition metal is called a TM-rich magnetic material. The magneto-optical recording medium 1
When performing signal reproduction from 0, laser light is irradiated from the substrate 1 side, and signal reproduction is performed using the magneto-optical effect of the magnetic domain enlarged and transferred from the recording layer 5 to the reproduction layer 3 and the laser light.

Referring to FIG. 2, a cross-sectional structure of a magneto-optical recording medium for reproducing a signal by the MSR method will be described. In the magneto-optical recording medium 20, an interference layer 2 made of SiN is formed on a light-transmitting substrate 1 made of glass, polycarbonate, or the like, and a reproduction layer 7 made of GdFeCo is formed on the interference layer 2; A recording layer 5 made of TbFeCo is formed thereon, and a protective layer 6 made of SiN is formed on the recording layer 5. Magneto-optical recording medium 2 for reproducing signals by MSR method
GdFeCo used for the 0 reproducing layer 7 is a magnetic material in which the magnetization of Gd as a rare earth metal is larger than the magnetization of FeCo as a transition metal. Reducing large rare earth metal magnetic materials
It is called a rich magnetic material. When reproducing a signal from the magneto-optical recording medium 20, the substrate 1 is irradiated with laser light, and the signal is reproduced using the magneto-optical effect of the magnetic domain transferred from the recording layer 5 to the reproducing layer 7 and the laser light. Do. First Embodiment In the first embodiment, discrimination between a magneto-optical recording medium for reproducing a signal by magnetic domain expansion and a magneto-optical recording medium for reproducing a signal by the MSR method, and a magneto-optical method according to the discrimination result. The reproduction of the recording medium will be described.

The magneto-optical recording medium 10 for reproducing a signal by magnetic domain expansion and the magneto-optical recording medium 20 for reproducing a signal by the MSR method are both magnetic domains enlarged or transferred from the recording layer 5 to the reproducing layers 3 and 7. In that the signal is reproduced by using the magneto-optical effect with the irradiated laser light. However, as described above, the magnetic material used for the reproducing layer 3 of the magneto-optical recording medium 10 is TM-rich. The magnetic material used in the reproducing layer 7 of the magneto-optical recording medium 20 is a remarkably different material in that the magnetic material is an RE-rich magnetic material. Accordingly, the present invention detects a difference in magnetic characteristics due to a difference in magnetic material used for such a reproducing layer, and performs magneto-optical recording in which a magneto-optical recording medium mounted on a recording / reproducing apparatus reproduces a signal by expanding a magnetic domain. This is to determine whether the medium is a medium or a magneto-optical recording medium for reproducing signals by the MSR method.

Referring to FIG. 3, the dependence of the Kerr rotation angle of the TM-rich magnetic material and the RE-rich magnetic material on the applied magnetic field will be described. The curve in FIG. 3A shows the dependence of the Kerr rotation angle of the TM-rich magnetic material on the applied magnetic field.
In an M-rich magnetic material, when the direction of the applied magnetic field is positive, the Kerr rotation angle becomes a positive value,
When the direction of the applied magnetic field is negative, the Kerr rotation angle has a negative value. Here, the application of the magnetic field in the plus direction means that when the magneto-optical recording medium is viewed from the direction in which the laser light is irradiated, the polarization plane of the laser light reflected by the magneto-optical recording medium rotates clockwise. A magnetic field in such a direction is applied, and a magnetic field in a minus direction is applied, when the magneto-optical recording medium is viewed from the direction of irradiating the laser light, the laser reflected by the magneto-optical recording medium This means that a magnetic field is applied in a direction such that the plane of polarization of light rotates counterclockwise.

On the other hand, the curve in FIG. 3B shows the dependency of the Kerr rotation angle of the RE-rich magnetic material on the applied magnetic field. In the RE-rich magnetic material, the direction of the applied magnetic field is positive. When the direction of the applied magnetic field is negative, the Kerr rotation angle becomes a positive value. Therefore, the polarities of the TM-rich magnetic material and the RE-rich magnetic material are opposite to the applied magnetic field.

Therefore, in the present invention, the reproducing layer is applied to each of the magneto-optical recording media 10 and 20 mounted on the recording / reproducing apparatus in a state where a positive DC magnetic field is applied and a state where a negative DC magnetic field is applied. The method is characterized in that the reflected light of the laser light applied to 3, 7 is detected as a magneto-optical signal and the difference between the two detected magneto-optical signals is calculated to determine the type of the mounted magneto-optical recording medium. And That is, a magneto-optical signal detected in a state where a positive DC magnetic field is applied to a TM-rich magnetic material (ie,
The car rotation angle. same as below. ) The difference between L1 and the magneto-optical signal L2 detected when a negative DC magnetic field is applied to the TM-rich magnetic material is positive, whereas the positive DC Since the difference between the magneto-optical signal L1 detected with the magnetic field applied and the magneto-optical signal L2 detected with the negative DC magnetic field applied to the RE-rich magnetic material becomes negative, the two light beams Depending on whether the difference between the magnetic signals L1 and L2 is plus or minus, a TM-rich magnetic material is
Or a magneto-optical recording medium having an RE-rich magnetic material in the reproducing layer 7 (that is, a magneto-optical recording medium for performing signal reproduction by the MSR method). Recording medium 20).

The polarities of the respective Kerr rotation angles shown in FIGS. 3A and 3B may be reversed depending on how the Kerr rotation angles are defined as positive or negative. Since the polarity is always reversed between the magnetic material and the RE-rich magnetic material, the difference between the magneto-optical signals detected by applying a magnetic field having two different directions as described above is calculated,
If the operation result is positive (also referred to as a first sign) or negative (second
Also referred to as sign. ), It is possible to discriminate between a magneto-optical recording medium for reproducing signals by magnetic domain expansion and a magneto-optical recording medium for reproducing signals by the MSR method.

Referring to FIG. 4, the means for determining the magneto-optical recording medium will be described. The reproducing layer 3 of the magneto-optical recording medium 10 or the reproducing layer 7 of the magneto-optical recording medium 20 is irradiated with the laser light 40 from the substrate 1 side, and DC magnetic fields 41 and 42 are applied from the side opposite to the side irradiated with the laser light 40. . DC magnetic field 41
Is applied, the magneto-optical signal L1 is generated by the laser light 40.
After that, the magneto-optical signal L2 is detected by the laser light 40 with the DC magnetic field 42 applied. Therefore, in the present invention, it is not necessary to rotate the magneto-optical recording medium mounted on the recording / reproducing apparatus, and the laser light 40 and the DC magnetic fields 41 and 42 are irradiated or applied to reflect the reflected light from the magneto-optical recording medium. Only by detecting, the type of the mounted magneto-optical recording medium can be determined.

FIG. 5 shows the structure of an optical pickup used for reproducing signals from a magneto-optical recording medium. Wavelength 635 nm emitted from semiconductor laser 50 (tolerance ± 1
The laser beam (5 nm) is collimated by a collimator lens 51, condensed by an objective lens 53 via a half mirror 52, and applied to the magneto-optical recording medium 10 or 20.
The laser light reflected by the magneto-optical recording medium 10 or 20 returns to the half mirror 52 via the objective lens 53, and half of the laser light is reflected by the half mirror 52 in the direction of 90 degrees and enters the Wollaston prism 54. In the Wollaston prism 54, the laser light is separated into a P-polarized component, an S-polarized component, and a component in which P-polarized light and S-polarized light are mixed, and is condensed by a condenser lens 55 and irradiated to a photodetector 56. . The difference between the P-polarized component laser beam 57 and the S-polarized component laser beam 58 among the laser beams irradiated to the photodetector 56 is detected as a magneto-optical signal, and the P-polarized and S-polarized laser beams are mixed. 59 is detected as a focus error signal and a tracking error signal.

Referring to FIG. 6, the planar structure of the photodetector 56 for detecting a magneto-optical signal will be described. Photodetector 56
Are arranged so that the direction indicated by arrow 60 is the tracking direction of the magneto-optical recording medium, and the direction indicated by arrow 61 is the track direction (tangential direction) of the magneto-optical recording medium, and the surface thereof is divided into six. ing. Light detector 56
At 0, the P-polarized component laser light 57 is output,
The laser light 58 of the polarization component is transmitted to the photodetectors 562, 563,
At 564 and 565, the laser light 59 in which the P-polarized light and the S-polarized light are mixed is detected. Then, the light detection unit 560,
By calculating the difference between the intensities P1 and P2 of the laser light detected at 561, the magneto-optical signal L is detected. Also,
The respective intensities of the laser light detected by the light detectors 562, 563, 564, and 565 are detected as a focus error signal and a tracking error signal by a known push-pull method. In the present invention, the DC magnetic field 41 or 42
To calculate the difference between the laser beams detected by the photodetectors 560 and 561 to obtain the magneto-optical signal L (L1, L2).
2) is detected.

Referring to FIG. 7, a flowchart for determining the type of the magneto-optical recording medium according to the present invention will be described. When the determination starts (S1), a magnetic field in the first direction is applied to the magneto-optical recording medium (S2). Here, the first
Is the magnetic field in the plus direction described above. Thereafter, the first magneto-optical signal L1 is detected from the magneto-optical recording medium by the photodetector 56 (S3). Next, a magnetic field in the second direction is applied to the magneto-optical recording medium (S4), and the photodetector 56 detects a second magneto-optical signal from the magneto-optical recording medium (S5). Here, the magnetic field in the second direction is the above-described magnetic field in the minus direction. After the first and second magneto-optical signals L1 and L2 are detected, the difference S = L1− between the first magneto-optical signal L1 and the second magneto-optical signal L2.
L2 is calculated (S6), and it is determined whether the calculation result S is positive or negative (S7). The value of the operation result S is positive, that is, S> 0
If so, the first type of magneto-optical recording medium, that is, the magneto-optical recording medium 10 that performs signal reproduction by magnetic domain expansion is determined (S8), and if the value of S is negative, that is, S <0, The two types of magneto-optical recording media, that is, magneto-optical recording media 20 that perform signal reproduction by the MSR method are determined (S9).

Referring to FIG. 8, a reproducing apparatus for a magneto-optical recording medium for determining the type of a magneto-optical recording medium according to the present invention will be described. The playback device includes an optical pickup 80, a playback signal amplification circuit 81, a servo circuit 82, a servo mechanism 83,
It includes a spindle motor 84, a shaper 85, a decoder 86, a microcomputer 87, a control circuit 88, a magnetic head drive circuit 89, a laser drive circuit 90, and a magnetic head 91. The optical pickup 8 irradiates the magneto-optical recording medium 10 or 20 with laser light and detects the reflected light. The reproduction signal amplification circuit 81 amplifies the signal output from the photodetector 56 of the optical pickup 80 based on a predetermined reference, and outputs a tracking error signal, a focus error signal, and a clock to the servo circuit 82, and Signals L1, L2
To the microcomputer 87 and the magneto-optical signal at the time of reproduction to the shaper 85. The servo circuit 82 controls the servo mechanism 83 based on the input tracking error signal and focus error signal. The servo mechanism 83 performs tracking servo and focus servo of the objective lens in the optical pickup 80. Further, the servo circuit 82 rotates the spindle motor 84 at a predetermined rotation speed based on the input clock. The shaper 85 removes noise from the input magneto-optical signal at the time of reproduction and outputs the noise to the decoder 86. The decoder 86 demodulates the magneto-optical signal modulated in a predetermined format and outputs the demodulated signal as reproduction data. The microcomputer 87
The above-described magneto-optical signals L1 and L2 are input, and the process proceeds to step S in FIG.
The calculation of S = L1−L2 shown in 6 to S9 is performed, and it is determined whether the calculation result S is positive or negative to determine the type of the magneto-optical recording medium. Then, based on the determination result, the control circuit 8
8 is controlled. The control circuit 88 outputs a signal to a magnetic head drive circuit 89 and a laser drive circuit 90 in accordance with an instruction from the microcomputer 87. The magnetic head drive circuit 89 drives the magnetic head 91, and the laser drive circuit 90 Is driven.

The operation of determining the type of the magneto-optical recording medium will be described. When the magneto-optical recording medium 10 or 20 is mounted on the recording / reproducing apparatus, the control circuit 88 controls the laser driving circuit 9
0 and outputs a signal to the magnetic head drive circuit 89, which drives the magnetic head 91, and the magnetic head 91 applies a DC magnetic field 41 or 42 to the magneto-optical recording medium 10 or 20. The laser drive circuit 90 drives the semiconductor laser 50 based on a signal from the control circuit 88, and the optical pickup 80 irradiates the magneto-optical recording medium 10 or 20 with laser light, and the DC magnetic field 41 or 42 is applied. In this state, the reflected light is detected by the photodetector 56.
Then, the photodetector 56 outputs magneto-optical signals L1 and L2 based on the laser beams detected by the photodetectors 560 and 561. The output magneto-optical signals L1 and L2 are amplified to a predetermined value by the reproduction signal amplifier circuit 81 and output to the microcomputer 87. The microcomputer 87 determines the type of the mounted magneto-optical recording medium based on the input magneto-optical signals L1 and L2 by the method described above.

Next, the operation after the type of the magneto-optical recording medium is determined will be described. When the type of the magneto-optical recording medium is determined, the microcomputer 87 outputs the result of the determination to the control circuit 88. The control circuit 88 controls the magnetic head drive circuit 89 and the laser drive circuit 9 based on the determination result.
Control 0. That is, when the mounted magneto-optical recording medium is a magneto-optical recording medium that reproduces a signal by magnetic expansion, the control circuit 88 sends a signal to the magnetic head driving circuit 89 so that the magnetic head 91 generates an alternating magnetic field. And the semiconductor laser 50 outputs a signal to the laser drive circuit 90 so that the magnetic domain of the recording layer 5 of the magneto-optical recording medium 10 generates laser light having an intensity that is not transferred to the reproducing layer 3 by the laser light alone. A magnetic head driving circuit 89 drives a magnetic head 91, and the magnetic head 91 applies an alternating magnetic field to the magneto-optical recording medium 1.
Apply to 0. Further, the laser drive circuit 90 drives the semiconductor laser 50, and the semiconductor laser 50 generates a laser beam having an intensity such that the magnetic domain of the recording layer 5 is not transferred to the reproduction layer 3,
As a result, the optical pickup 80 is mounted on the magneto-optical recording medium 10.
Is irradiated with the laser light. Then, the magnetic domain of the recording layer 5 of the magneto-optical recording medium 10 is enlarged and transferred to the reproducing layer 3 by the laser light and the alternating magnetic field, and the reflected light is detected by the photodetector 56 so that the magnetic domain of the recording layer 5 becomes optical. Reproduced as a magnetic signal. Since the subsequent operation is as described above,
Omitted.

On the other hand, the mounted magneto-optical recording medium is MSR
In the case of a magneto-optical recording medium that performs signal reproduction by the method, the control circuit 88 controls the semiconductor laser 50 to read the reproduction layer 7 when the magnetic domain of the recording layer 5 of the magneto-optical recording medium 20 is only a laser beam.
A signal is output to the laser drive circuit 90 so as to generate a laser beam having the intensity transferred to the magnetic head drive circuit 89, and no signal is output to the magnetic head drive circuit 89. Then, the laser drive circuit 90
The semiconductor laser 50 is driven, and the semiconductor laser 50 generates a laser beam having such intensity that the magnetic domains of the recording layer 5 are transferred to the reproducing layer 7, whereby the optical pickup 80 transmits the laser beam to the magneto-optical recording medium 20. And irradiates the reflected light with a photodetector 5
The signal is reproduced by the MSR method by detecting the signal in step 6. Subsequent operations are the same as described above, and a description thereof will be omitted.

As described above, the type of magneto-optical recording medium mounted can be determined by the reproducing apparatus shown in FIG. 8, and a signal can be reproduced according to the type of magneto-optical recording medium determined. Second Embodiment In a second embodiment, discrimination of a magneto-optical recording medium for reproducing a signal by magnetic domain expansion, a magneto-optical recording medium for reproducing a signal by an MSR method, and a magneto-optical recording medium other than these are performed. The reproduction of the magneto-optical recording medium according to the determination result will be described.

With reference to FIG. 9, the sectional structure of a magneto-optical recording medium for reproducing signals by magnetic domain expansion and a magneto-optical recording medium other than a magneto-optical recording medium for reproducing signals by the MSR method will be described. In the magneto-optical recording medium 30, an interference layer 2 made of SiN is formed on a light-transmitting substrate 1 such as glass or polycarbonate, and a recording / reproducing layer 8 made of TbFeCo is formed on the interference layer 2. S on the recording / reproducing layer 8
It has a structure in which a protective layer 6 made of iN is formed. TbFeCo used for the recording / reproducing layer 8 of the magneto-optical recording medium 30
Is a magnetic material in which the magnetization of FeCo which is a transition metal is almost equal to the magnetization of Tb which is a rare earth metal. When reproducing a signal from the magneto-optical recording medium 30, the substrate 1 is irradiated with a laser beam, and the signal is reproduced using the magneto-optical effect of the magnetic domain of the recording / reproducing layer 8 and the laser beam.

Referring to FIG. 10, transition metal FeC
The dependence of the Kerr rotation angle of the magnetic material on the applied magnetic field, in which the magnetization of o is substantially equal to the magnetization of Tb, which is a rare earth metal, will be described. The magneto-optical signal detected by applying a magnetic field to a magnetic material in which the magnetization of FeCo, which is a transition metal, is substantially equal to the magnetization of Tb, which is a rare earth metal, has a substantially constant value independent of the applied magnetic field. Therefore, the first magneto-optical signal L1 and the second magneto-optical signal L2 described in the first embodiment have substantially the same value, and the difference S = L1−L2 is almost “0”. Therefore, by calculating the difference between the detected first magneto-optical signal L1 and the second magneto-optical signal L2, the magneto-optical recording medium 10 for reproducing the signal by the magnetic domain expansion, and the light for reproducing the signal by the MSR method. The magnetic recording medium 20 and the other magneto-optical recording medium 30 can be distinguished. That is, when S is positive, it is determined to be the magneto-optical recording medium 10, when S is negative, it is determined to be the magneto-optical recording medium 20, and when S is almost "0", it is determined to be the magneto-optical recording medium 30. However, in practice, the first magneto-optical signal L1 detected from a magnetic material in which the magnetization of FeCo as the transition metal is substantially equal to the magnetization of Tb as the rare earth metal
And the second magneto-optical signal L2 do not have the same value, so in the present application, when the value of S is in the range of -0.1 to +0.1 degrees, the medium is determined to be the magneto-optical recording medium 30. I will.

The detection of the first magneto-optical signal L1 and the second magneto-optical signal L2 from the magneto-optical recording medium 30 is performed by using the optical pickup shown in FIG. 5 described in the first embodiment and FIG. The detection is performed using the photodetector 56 shown in the figure, and the detection method is the same as that described above. Therefore, the description is omitted. With reference to FIG. 11, a flow chart for determining the magneto-optical recording medium according to the second embodiment will be described. Steps S1 to S6 are the same as the description of FIG. 7 of the first embodiment, and a description thereof will be omitted. After calculating the difference between the first magneto-optical signal L1 and the second magneto-optical signal L2 in step S6. Step S10
It is determined whether or not the value of S is in the range of -0.1 to +0.1 degrees, and if the value of S is in this range, the third type of magneto-optical recording medium is determined in step S11. That is, it is determined that the medium is the magneto-optical recording medium 30 (S11). If the value of S does not fall within the above range, it is determined in step S12 whether the value of S is positive or negative, and if it is positive, it is determined as the first type of magneto-optical recording medium, that is, the magneto-optical recording medium 10. (S13), S
Is negative, it is determined that the medium is the second magneto-optical recording medium, that is, the magneto-optical recording medium 20 (S14).

A reproducing apparatus for discriminating the magneto-optical recording media 10, 20, and 30 and performing reproduction according to the discriminated magneto-optical recording medium has the same configuration as the reproducing apparatus shown in FIG. 8 in the first embodiment. It is a playback device. When the microcomputer 87 is used in the second embodiment, the microcomputer 87 executes step S6 in FIG.
From step to step S14, the type of the magneto-optical recording medium mounted on the reproducing apparatus is determined. Microcomputer 87
Outputs the determined result to the control circuit 88. When the discrimination result is the first and second types of magneto-optical recording media, the control circuit 88 performs the same operation as that described in the first embodiment. On the other hand, when the result of the determination is that of the third type of magneto-optical recording medium, the control circuit 88 controls the magnetic head 9
1 outputs a signal to the magnetic head drive circuit 89 so that the semiconductor laser 5 in the optical pickup 80 does not apply a magnetic field.
0 outputs a signal to the laser drive circuit 90 so as to emit a laser beam having an intensity that does not erase the signal recorded on the recording / reproducing layer 8 of the magneto-optical recording medium 30 (also referred to as a third intensity laser beam). . The other description is the same as the description of FIG. 8 in the first embodiment.

As described above, the magneto-optical recording media 10, 20,
30 types of magneto-optical recording media can be determined, and
Reproduction suitable for the discriminated magneto-optical recording medium is possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional structural view of a magneto-optical recording medium that performs signal reproduction by magnetic domain expansion.

FIG. 2 is a sectional structural view of a magneto-optical recording medium for performing signal reproduction by the MSR method.

FIG. 3 is a diagram showing the applied magnetic field dependence of the Kerr rotation angle of a TM-rich magnetic material and a RE-rich magnetic material.

FIG. 4 is a diagram illustrating a method for detecting a Kerr rotation angle from a reproduction layer.

FIG. 5 is a configuration diagram of an optical pickup.

FIG. 6 is a plan view of a light detection unit.

FIG. 7 is a flowchart for determining the type of a magneto-optical recording medium.

FIG. 8 is a block diagram of a recording / reproducing apparatus for a magneto-optical recording medium.

FIG. 9 is a cross-sectional structural view of a magneto-optical recording medium for reproducing signals by magnetic domain expansion and a magneto-optical recording medium other than a magneto-optical recording medium for reproducing signals by the MSR method.

FIG. 10 is a diagram showing the applied magnetic field dependence of the Kerr rotation angle of a magnetic material in which the magnetization of a transition metal is substantially equal to the magnetization of a rare earth metal.

FIG. 11 is another flowchart for determining the type of the magneto-optical recording medium.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Interference layer 3, 7 ... Reproducing layer 4 ... Nonmagnetic layer 5 ... Recording layer 6 ... Protective layer 8 ... Recording / reproducing layer 10, 20, 30, magneto-optical recording medium 40, laser light 41, 42, DC magnetic field 56, photodetector 560, 561, 562, 563, 564, 564,.
・ Light detector

Claims (15)

[Claims] 1. A discriminating circuit for discriminating a type of a magneto-optical recording medium by applying or irradiating a magnetic field and a laser beam to the magneto-optical recording medium. 2. A magnetic field applying means for applying a magnetic field in a first direction and a magnetic field in a second direction to a magneto-optical recording medium; and irradiating the magneto-optical recording medium with a laser beam; Detecting a first magneto-optical signal from the magneto-optical recording medium in response to the application of the magnetic field, and responding to the application of the magnetic field in the second direction. Optical means for detecting a second magneto-optical signal from the first and the second magneto-optical signal, wherein the first and second magneto-optical signals detected by the optical means are inputted, and the first magneto-optical signal and the second magneto-optical signal are inputted. Is calculated, and if the calculation result is the first code, it is determined that the medium is the first type of magneto-optical recording medium. If the calculation result is the second code, the second type of light is recorded. A discriminating circuit for discriminating the magneto-optical recording medium, the discriminating means including a discriminating means for discriminating the magnetic recording medium 3. A magnetic field applying means for applying a magnetic field in a first direction and a magnetic field in a second direction to a magneto-optical recording medium; and irradiating the magneto-optical recording medium with a laser beam; Detecting a first magneto-optical signal from the magneto-optical recording medium in response to the application of the magnetic field, and responding to the application of the magnetic field in the second direction. Optical means for detecting a second magneto-optical signal from the first and the second magneto-optical signal, wherein the first and second magneto-optical signals detected by the optical means are inputted, and the first magneto-optical signal and the second magneto-optical signal are inputted. Is calculated, and if the calculation result is in the range of -0.1 to +0.1 degrees, it is determined to be a third type of magneto-optical recording medium, and the calculation result is a value outside the range. If the result is the first code, it is determined that the medium is the first type of magneto-optical recording medium, and the calculation result is If a second code to a value outside 囲以 the determination circuit of the magneto-optical recording medium comprising a determining means for determining a second type of magneto-optical recording medium. 4. The discrimination circuit according to claim 2, wherein the magnetic field in the second direction is a magnetic field in a direction opposite to the magnetic field in the first direction. 5. The discrimination circuit according to claim 4, wherein the magnetic field in the first direction is a magnetic field perpendicular to the magneto-optical recording medium. 6. The magneto-optical recording medium according to claim 2, wherein the first type of magneto-optical recording medium is a magneto-optical recording medium having a reproducing layer in which a transition metal has a larger magnetization than a rare earth metal. The discriminating circuit according to 1. 7. The magneto-optical recording medium of the first type is a magneto-optical recording medium having a reproducing layer in which the magnetization of a transition metal is larger than the magnetization of a rare earth metal, and the second type of magneto-optical recording medium is 6. The discriminating circuit according to claim 2, wherein the discriminating circuit is a magneto-optical recording medium having a reproducing layer in which the magnetization of the rare earth metal is larger than the magnetization of the transition metal. 8. A reproducing apparatus for a magneto-optical recording medium including the discriminating circuit according to claim 2, wherein an alternating magnetic field is generated when the discriminating means discriminates the magneto-optical recording medium of the first type. And a driving circuit for driving the magnetic field applying means so as not to generate a magnetic field when the determining means determines that the medium is the second type of magneto-optical recording medium. When the discriminating unit discriminates the first type of magneto-optical recording medium, the discriminating unit drives the laser beam generating unit in the optical unit so as to generate a laser beam of the first intensity. A laser driving circuit for driving a laser light generating means in the optical means so as to generate a laser light of a second intensity when the medium is determined to be the second type of magneto-optical recording medium. Playback device. 9. The reproducing apparatus according to claim 8, wherein the first intensity laser beam is a laser beam whose magnetic domain is not transferred from a recording layer to a reproducing layer of the magneto-optical recording medium. 10. The laser beam of the first intensity is a laser beam of an intensity that does not transfer a magnetic domain from a recording layer to a reproduction layer of the magneto-optical recording medium, and the laser beam of the second intensity is the laser beam of the second intensity. 9. The reproducing apparatus according to claim 8, wherein the reproducing apparatus is a laser beam having an intensity at which a magnetic domain is transferred from a recording layer of the magnetic recording medium to the reproducing layer. 11. A reproducing apparatus for a magneto-optical recording medium including the discriminating circuit according to claim 3, wherein an alternating magnetic field is generated when the discriminating means discriminates the first type of magneto-optical recording medium. When the discrimination means discriminates between the second and third types of magneto-optical recording media, the magnetic field application means drives the magnetic field application means so as not to generate a magnetic field. Means driving circuit, when the discriminating means discriminates the first type of magneto-optical recording medium, drives the laser light generating means in the optical means so as to generate laser light of the first intensity; When the discriminating means determines that the medium is the second type of magneto-optical recording medium, the discriminating means drives the laser light generating means in the optical means so as to generate a laser beam of a second intensity. Third type of magneto-optical recording medium If it is determined, the playback apparatus of the magneto-optical recording medium comprising a laser drive circuit for driving the laser light generating means in said optical means so as to generate a laser beam of a third intensity. 12. A magnetic field in a first direction and a magnetic field in a second direction are applied to a magneto-optical recording medium, and a first magnetic field detected from the magneto-optical recording medium corresponding to the magnetic field in the first direction. A difference between the magneto-optical signal of the second direction and a second magneto-optical signal detected from the magneto-optical recording medium corresponding to the magnetic field in the second direction, and the calculation result is the first sign. Is determined to be the first type of magneto-optical recording medium,
A method for discriminating a magneto-optical recording medium, wherein if the calculation result is a second code, the discrimination is made as a second type of magneto-optical recording medium. 13. A magnetic field in a first direction and a magnetic field in a second direction are applied to a magneto-optical recording medium, and a first magnetic field detected from the magneto-optical recording medium in response to the magnetic field in the first direction. And the difference between the magneto-optical signal and the second magneto-optical signal detected from the magneto-optical recording medium corresponding to the magnetic field in the second direction is calculated.
If the angle is within the range of +0.1 degrees, it is determined that the medium is a third type of magneto-optical recording medium. A method for discriminating a magneto-optical recording medium, wherein the discrimination is made as a magnetic recording medium, and when the calculation result is a value outside the above range and a second code, the discrimination is made as a second type of magneto-optical recording medium. 14. The magneto-optical recording medium of the first type,
12. A magneto-optical recording medium having a reproducing layer in which the transition metal has a magnetization larger than that of the rare-earth metal.
3. The determination method according to 3. 15. The magneto-optical recording medium of the first type,
A magneto-optical recording medium having a reproducing layer in which the transition metal has a magnetization larger than that of the rare earth metal, wherein the second type of magneto-optical recording medium has a reproducing layer in which the rare earth metal has a magnetization larger than that of the transition metal. 14. The discriminating method according to claim 12, wherein the discriminating method is a magnetic recording medium.