JP2001216693A - Magneto-optical recording medium, reproducing device and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical reproducing device for reproducing an identification signal from a magneto-optical disk with the identification signal recorded thereon without disappearing magnetization. SOLUTION: The magneto-optical reproducing device 190 reproduces the identification signal recorded in the magneto-optical disk 81. The disk 81 has a recording layer given heat processing for lowering the intensity of magnetization occurring in magneto-optical recording to the degree of not disappearing by a prescribed pattern on a substrate and has a prescribed signal magneto- optically recorded in an area in which the identification signal is recorded by the difference of a performance index corresponding to the prescribed pattern. The device 190 has an optical pickup 150 for irradiating the disk 81 with laser beams for reproduction, a generation circuit 160 for generating a reproduction signal MO consisting of a magneto-optical signal corresponding to the laser beams for reproduction reflected by the disk 81 and an identification signal detecting circuit 180 for detecting the identification signal based on the fluctuation of the amplitude of the signal MO.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magneto-optical recording medium, a reproducing apparatus for reproducing an identification signal recorded on the magneto-optical recording medium, and a reproducing apparatus for reproducing the identification signal recorded on the magneto-optical recording medium. And how to.

[0002]

2. Description of the Related Art With regard to a rewritable magneto-optical recording medium such as a magneto-optical disk, a technology such as a system for preventing copying or charging for copying is an important technology in the information society. For example, JP-A-9-274774 discloses that
An invention of an illegal copy prevention method effective for a recording medium such as a magneto-optical recording medium having a read-only area and a rewritable area is disclosed. The identification signal used for such a purpose includes a signal that can be determined by a normal reproduction method depending on a required degree of security, and includes a signal that cannot be determined by a normal reproduction method. And a signal that can be determined by a special reproduction method, and there are various forms.

As reports for the purpose of preventing copying of a magneto-optical disk, there are JP-A-8-167184, JP-A-9-17041, and JP-A-9-91781. JP-A-8-167184 discloses a magneto-optical device having a first layer of a magnetic film, a third layer of a magnetic film, and a second layer of a non-magnetic layer located between the first and third layers. In the recording medium, the Curie temperature of the third layer is higher than that of the first layer,
It is disclosed that data characterizing the medium is recorded on a third layer.

Japanese Patent Application Laid-Open No. 9-17041 discloses that a defective portion is formed by melting or evaporating a predetermined position of an optical recording layer, and the defective portion is provided at a specific position of each medium. I have. However, there is a possibility that an apparatus for generating a defective portion becomes large.

Japanese Patent Application Laid-Open No. 9-91781 discloses a method of irreversibly recording a medium identification code by rotating a magneto-optical disk at a low speed and irradiating a laser at a high recording power to change the quality of a magneto-optical recording layer to eliminate magnetization. Is disclosed. Further, it is disclosed that a medium identification code is reproduced after performing an erasing operation on a recording area of the medium identification code.

[0006]

However, in the magneto-optical recording medium disclosed in Japanese Patent Application Laid-Open No. 9-91781, the magnetization is lost. Therefore, when reproducing the medium identification code, a magneto-optical signal (magneto-optical reproduction signal) is generated. S / N may be deteriorated. This means that during normal playback, the positive and negative Kerr rotation angles (+ θk
, −θk), the magneto-optical signal is detected,
During reproduction of the medium identification code, a magneto-optical signal is detected based on the difference between the positive Kerr rotation angle (+ θk) and 0 or the difference between the negative Kerr rotation angle (−θk) and 0 due to the disappearance of magnetization. Because you do.

A first object of the present invention is to provide a magneto-optical recording medium on which an identification signal is recorded without losing magnetization, and a reproducing apparatus capable of reproducing the identification signal from the magneto-optical recording medium, It is a second object of the present invention to provide a reproduction method.

[0008]

A magneto-optical recording medium according to the present invention is a magneto-optical recording medium having a recording layer on a substrate, wherein the recording layer controls the magnitude of magnetization generated during magneto-optical recording. Heat treatment is performed in a predetermined pattern to reduce the temperature to such an extent that the pattern does not disappear, and an identification signal is recorded based on a difference in the figure of merit corresponding to the predetermined pattern.

The magneto-optical recording medium according to the present invention is preferably a magneto-optical disk, and the temperature of the heat treatment is set such that a signal is rewritable by laser light in a magneto-optical recording apparatus for the magneto-optical disk. In this case, the temperature is higher than the temperature at which the recording layer of the magneto-optical disk can be heated by the laser beam irradiation.

[0010] The magneto-optical recording medium according to the present invention is preferably a magneto-optical disk, and the tracks of the magneto-optical disk are subjected to the heat treatment in the predetermined pattern. The heat treatment is repeatedly performed in the predetermined pattern.

In the magneto-optical recording medium according to the present invention, preferably, the recording area of the identification signal in the recording layer is:
Content is magneto-optically recorded.

A reproducing apparatus according to the present invention has a recording layer on a substrate which has been subjected to a heat treatment in a predetermined pattern so as to reduce the magnitude of magnetization generated at the time of magneto-optical recording so as not to disappear.
A laser for irradiating a laser beam for reproduction to a magneto-optical recording medium in which a predetermined signal is magneto-optically recorded in an area where an identification signal is recorded according to a difference in the figure of merit corresponding to the predetermined pattern; A generation circuit for generating a reproduction signal composed of a magneto-optical signal corresponding to the reproduction laser light reflected by the medium; and an identification signal detection circuit for detecting the identification signal based on a fluctuation in the amplitude of the reproduction signal.

Preferably, the reproducing apparatus according to the present invention further comprises a magnetic head for applying a magnetic field to a portion where magneto-optical recording is performed at the time of magneto-optical recording of a signal on the magneto-optical recording medium. The magnetic recording medium is a magneto-optical disk,
The laser and the magnetic head each include a recording layer on which a track is subjected to the heat treatment in the predetermined pattern on a substrate, and a light on which an identification signal is recorded based on a difference in the figure of merit corresponding to the predetermined pattern. On the track of the magnetic disk, the predetermined signal is magneto-optically recorded, and after the magneto-optical recording of the predetermined signal, the laser irradiates the reproduction laser light on the track of the magneto-optical disk,
The period of the predetermined signal is smaller than half the period of the predetermined pattern formed on the track of the magneto-optical disk.

In the reproducing apparatus according to the present invention, for example, the predetermined signal has a fixed period, and the fixed period is
The period of the predetermined pattern formed on the track of the magneto-optical disk may be in a range of about 0.1 times to about 0.2 times.

In the reproducing apparatus according to the present invention, preferably, the identification signal detecting circuit includes an envelope detecting circuit for detecting a change in amplitude of the reproducing signal, and an integrating circuit for integrating an output signal of the envelope detecting circuit. And a binarizing circuit for detecting the identification signal based on an integrated value indicated by an output signal of the integrating circuit and a preset threshold value. Are repeatedly applied in the predetermined pattern.

In the reproducing apparatus according to the present invention, preferably, the laser and the magnetic head erase the magneto-optically recorded predetermined signal after irradiation with the reproducing laser beam.

Preferably, the reproducing apparatus according to the present invention further includes an information detecting circuit for detecting the predetermined signal based on the reproduced signal, wherein a recording area of the identification signal in the recording layer includes: The content of the magneto-optical recording medium is magneto-optically recorded as the predetermined signal.

In the reproducing apparatus according to the present invention, preferably, the magneto-optical recording medium is a magneto-optical disk, and the temperature of the heat treatment is made rewritable by laser light in the magneto-optical recording apparatus for the magneto-optical disk. When a signal is magneto-optically recorded, the temperature is higher than a temperature at which the recording layer of the magneto-optical disk can be heated by the laser beam irradiation.

The reproducing method according to the present invention has a recording layer on a substrate which has been subjected to a heat treatment in a predetermined pattern so as to reduce the magnitude of magnetization generated during magneto-optical recording so as not to disappear.
A reproducing method for reproducing said identification signal from a magneto-optical recording medium on which an identification signal is recorded according to a difference in figure of merit corresponding to said predetermined pattern, wherein said predetermined signal is recorded on said magneto-optical recording medium by magneto-optical recording. Performing a step of irradiating the magneto-optical recording medium with a reproducing laser beam, and generating a reproducing signal composed of a magneto-optical signal corresponding to the reproducing laser beam reflected by the magneto-optical recording medium. Detecting the identification signal based on a fluctuation in the amplitude of the reproduction signal.

In the reproducing method according to the present invention, preferably, the magneto-optical recording medium is a magneto-optical disk, and the tracks of the magneto-optical disk are subjected to the heat treatment in the predetermined pattern. The period of the predetermined signal is less than half the period of the predetermined pattern formed on the track of the magneto-optical disk. In the step of magneto-optical recording, the predetermined period is recorded on the track of the magneto-optical disk. In the step of magneto-optically recording a signal and irradiating the reproduction laser light, a track of the magneto-optical disk is irradiated with the reproduction laser light.

In the reproducing method according to the present invention, for example, the predetermined signal has a fixed period, and the fixed period is
The period of the predetermined pattern formed on the track of the magneto-optical disk may be in a range of about 0.1 times to about 0.2 times.

In the reproducing method according to the present invention, more preferably, the recording layer of the magneto-optical recording medium is subjected to the heat treatment repeatedly in the predetermined pattern, and in the step of detecting the identification signal, The identification signal is detected based on the number of times of detecting the fluctuation of the amplitude of the reproduction signal.

In the reproducing method according to the present invention, more preferably, in the step of irradiating the reproducing laser beam, the reproducing laser beam is repeatedly irradiated on a recording area of the recording layer where the identification signal is recorded. In the step of detecting the identification signal, the identification signal is detected based on the number of times of detecting the fluctuation of the amplitude of the reproduction signal.

The reproducing method according to the present invention preferably further comprises a step of erasing the predetermined signal magneto-optically recorded after irradiation with the reproducing laser beam.

In the reproducing method according to the present invention, preferably, the magneto-optical recording medium is a magneto-optical disk, and the temperature of the heat treatment is made rewritable by a laser beam in a magneto-optical recording device for the magneto-optical disk. When a signal is magneto-optically recorded, the temperature is higher than a temperature at which the recording layer of the magneto-optical disk can be heated by the laser beam irradiation.

In the reproducing apparatus according to the present invention described above, a magneto-optical disk or the like having a recording layer on a substrate which has been subjected to a heat treatment in a predetermined pattern to reduce the magnitude of the magnetization generated during magneto-optical recording to such an extent that it does not disappear. For magneto-optical recording media,
A reproduction laser beam is applied. The amplitude of a reproduction signal composed of a magneto-optical signal corresponding to the reproduction laser light reflected by the magneto-optical recording medium varies due to a difference in the figure of merit corresponding to the predetermined pattern. The identification signal detection circuit detects the identification signal based on a change in the amplitude of the reproduction signal.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic block diagram showing an embodiment of a reproducing apparatus according to the present invention.
A magneto-optical reproducing device 190 is exemplified as a reproducing device, and a magneto-optical disk 81 is illustrated as a magneto-optical recording medium driven by the magneto-optical reproducing device 190.

The magneto-optical reproducing device 190 includes the magnetic head 20.
, A magnetic head drive circuit 25, a motor 30, a motor drive circuit 35, a phase compensation circuit 40, and an amplification circuit 42.
, An optical pickup 150, an amplification circuit (head amplifier) 152, a laser drive circuit 155, and a generation circuit 16
0, an information detection circuit 165, a control circuit 170, and an identification signal detection circuit 180. This magneto-optical reproducing device 1
90 irradiates the rotating magneto-optical disk 81 with a reproducing laser beam to perform magneto-optical reproduction of a signal, and irradiates the rotating magneto-optical disk 81 with a recording laser beam as necessary. Performs magneto-optical recording of signals.

The control circuit 170 includes a magneto-optical reproducing device 190
Is a controller that controls the entire system, and is configured by, for example, a microcomputer. The control circuit 170 includes the motor drive circuit 35 and the laser drive circuit 1
55, optical pickup 150, phase compensation circuit 40, generation circuit 160, information detection circuit 165, identification signal detection circuit 1
80, and controls the magnetic head drive circuit 25 and the like.

The optical pickup 150 applies a laser beam L to a reproduction position of the magneto-optical disk 81 during magneto-optical reproduction.
Irradiate B. If necessary, the laser beam LB may be applied to the recording location of the magneto-optical disk 81 during magneto-optical recording.
Is irradiated. However, the power of the laser beam LB is larger during magneto-optical recording than during magneto-optical reproduction.

The magnetic head drive circuit 25 includes a control circuit 17
0, the magnetic excitation current S2 for driving is supplied to the magnetic head 20.
Supply 5. The magnetic head 20 includes a magneto-optical disk 81
Magnetic head drive circuit 2 during signal recording and signal erasing
The core is excited by the excitation current S 25 from the magnetic field 5, a line of magnetic force MB is generated from the core, and a magnetic field is applied to the laser irradiation portion of the magneto-optical disk 81. The magnetism of the magnetic head 20 is set, for example, to N-direction during signal erasing to align the direction of magnetization of the recording layer in a fixed direction, and to S-direction during signal recording to reverse the direction of magnetization of the recording layer. I have.

The motor 30 is constituted by, for example, a spindle motor, and rotates the magneto-optical disk 81 at a predetermined rotation speed. The motor 30 rotates the magneto-optical disk 81 so that the linear velocity becomes constant, for example.

The motor drive circuit 35 supplies drive power to the motor 30 to drive the motor 30. The motor drive circuit 35 may perform rotation control of the motor 30 by PWM (Pulse Width Modulation) control, and may perform PLL (Ph
Rotation control may be performed by ase Locked Loop) control.

The laser drive circuit 155 includes a control circuit 170
Drive signal SL is generated under the control of the above, and the semiconductor laser in the optical pickup 150 is driven by the drive signal SL,
The laser beam LB is output from the semiconductor laser. The laser drive circuit 155 makes the output power of the laser beam LB at the time of signal recording and signal erasing larger than at the time of magneto-optical reproduction.

The optical pickup 150 receives the laser beam L
B is supplied to the track of the magneto-optical disk 81, and the magneto-optical recording portion or the magneto-optical reproducing portion of the magneto-optical disk 81 is irradiated. At the time of magneto-optical recording, the temperature of the irradiated portion of the magneto-optical disk 81 becomes higher than the Curie point of the recording layer, and the irradiated portion is magnetized by the magnetic field applied from the magnetic head 20, and a predetermined signal is recorded.

The amplification circuit (head amplifier) 152 amplifies the output signals SA to SF of the photodetector in the optical pickup 150 and supplies the amplified signals to the generation circuit 160.

The generation circuit 160 generates a reproduction signal MO, a focus error signal FE, and a tracking error signal TE based on the output signals SA to SF of the photodetector from the amplification circuit 152.

The phase compensation circuit 40 generates a compensation signal by compensating (phase compensation and / or frequency compensation) the focus error signal FE and the tracking error signal TE, and supplies this compensation signal to the amplifier circuit 42.

The amplification circuit 42 has a focus error signal FE.
Is supplied to the focusing actuator in the optical pickup 150. Further, the amplifier circuit 42 outputs the tracking error signal TE
Is supplied to the tracking actuator in the optical pickup 150.

The information detection circuit 165 is supplied with the reproduction signal MO from the generation circuit 160, demodulates the reproduction signal MO, reproduces the recording signal of the magneto-optical disk 81, and outputs it as an output signal So.

The identification signal detection circuit 180 includes the generation circuit 16
0, the reproduction signal MO is supplied from the magneto-optical disk 81 based on the fluctuation or envelope of the amplitude of the reproduction signal MO.
, And outputs the detected identification signal to the control circuit 170.

When emboss pits indicating addresses are formed in the magneto-optical disk 81 in advance, the generation circuit 160 further generates a reproduction signal RF corresponding to the amount of reflected laser light and supplies it to the information detection circuit 165. The information detection circuit 165 may detect an address based on the reproduction signal RF and supply the detected address to the control circuit 170, and the control circuit 170 may control the magneto-optical reproduction based on the address.

FIG. 2 is a schematic structural view showing the optical pickup in FIG. The optical pickup 150 includes a semiconductor laser 4, a collimator lens 5, a beam splitter 3, an objective lens 2, a condenser lens 6, a cylindrical lens 7, a photodetector 18, a lens holder 2H, a focusing lens, It has an actuator 2F, a tracking actuator 2T, and a Wollaston prism 15.

The objective lens 2 is held by a lens holder 2H. The focusing actuator 2F is
Based on the drive signal Sfe, the lens holder 2H is moved in a focus direction perpendicular to the recording surface of the magneto-optical disk 81, and as a result, the objective lens 2 is moved in the focus direction. The tracking actuator 2T moves the lens holder 2H to the magneto-optical disk 81 based on the drive signal Ste.
, And as a result, the objective lens 2 is moved in the radial direction of the magneto-optical disk 81.

The semiconductor laser 4 outputs a linearly polarized laser beam based on the drive signal SL and supplies it to the collimator lens 5. The collimator lens 5 converts the laser light from the semiconductor laser 4 into parallel light and supplies the parallel light to the beam splitter 3. The beam splitter 3 passes the laser light from the collimator lens 5 and supplies the laser light to the objective lens 2. The objective lens 2 condenses the laser beam from the beam splitter 3 and supplies it to the track of the magneto-optical disk 81 having lands and / or grooves.

The objective lens 2 is a magneto-optical disk 8
The laser light reflected at 1 is returned to the beam splitter 3. The beam splitter 3 receives the laser light from the objective lens 2, reflects the emitted laser light, emits the reflected laser light, and supplies the laser light to the Wollaston prism 15.

The Wollaston prism 15 divides the laser light from the beam splitter 3 into the main laser light and the first and second laser lights.
And is supplied to the condenser lens 6. The condensing lens 6 condenses the laser light that has passed through the Wollaston prism 15, and forms a cylindrical lens (cylindrical lens) 7
To supply. The cylindrical lens 7 passes the laser beam from the condenser lens 6 and supplies the laser beam to the photodetector 18. Photodetector 1
Numeral 8 receives the laser beam from the cylindrical lens 7 at the light receiving section and generates output signals SA to SF.

FIG. 3 is an explanatory diagram showing the configuration of the light receiving section of the photodetector in FIG. The light receiving section of the photodetector 18 includes a main light receiving section 18S, a first sub light receiving section 18E, and a second sub light receiving section 18F. The main laser beam separated by the Wollaston prism 15 is supplied to the main light receiving unit 18S via the condenser lens 6 and the cylindrical lens 7. Main light receiving section 18S
Is divided into four equal parts by two dividing lines 18Sx and 18Sy, and has four divided areas 18A to 18D. A beam spot MS is formed on the main light receiving section 18S of FIG. 3 by the main laser light from the cylindrical lens 7.

The direction of the generatrix of the cylindrical lens 7 is
It forms an angle of about 45 degrees or about 135 degrees with the direction of the 8S division line 18Sx or 18Sy. The dividing line 18Sy of the main light receiving portion 18S to which the laser light reflected by the magneto-optical disk 81 is supplied is parallel or substantially parallel to the track direction of the magneto-optical disk 81. Division line 18S
The intersection of x and 18Sy is located at or substantially at the center of the main laser beam that has passed through the cylindrical lens 7.

Since the shape of the beam spot MS formed on the main light receiving portion 18S changes diagonally according to the distance between the magneto-optical disk 81 and the objective lens 2, the divided region 18
On the basis of the output signals SA to SD generated by A to 18D, the defocus of the magneto-optical disk 81 can be detected by the astigmatism method.

The first sub-light receiving portion 18E is supplied with the first sub-laser light separated by the Wollaston prism 15 via the condenser lens 6 and the cylindrical lens 7, and outputs an output signal SE.
Generate The first sub-light receiving portion 18E shown in FIG.
SE is formed.

The second sub-light receiving section 18F supplies the second sub-laser light separated by the Wollaston prism 15 via the condenser lens 6 and the cylindrical lens 7, and outputs the output signal SF.
Generate The second sub-light receiving portion 18F shown in FIG.
SF is formed.

The generating circuit 160 of the magneto-optical reproducing device 190
Generates a reproduction signal MO that is a magneto-optical signal based on the difference (SE-SF) between the output signals SE and SF of the photodetector 18 from the amplifier circuit 152. Further, among the output signals SA to SD of the photodetector 18 from the amplifying circuit 152, the focus error is determined based on the difference (for example, SA + SC-SB-SD) of the sum of the output signals of the two diagonally divided regions. Generate the signal FE. Also, of the output signals SA to SD of the photodetector 18 from the amplifier circuit 152, the difference (for example, SA +
SB-SC-SD) based on the tracking error signal T
Generate E.

FIG. 4 is a partially enlarged view of a magneto-optical disk used in the magneto-optical reproducing apparatus of FIG. FIG. 4 (A)
FIG. 3 is an explanatory partial enlarged view showing a recording layer when an identification signal is recorded by initializing the magneto-optical disk 81.
FIG. 4B is an explanatory partial enlarged view showing the recording layer when the identification signal is recorded by initializing the magneto-optical disk 81 and a carrier signal having a constant period is recorded.

The magneto-optical disk 81 shown in FIG. 4A has been initialized, and the track 81T has an initial recording area 81I.
Are formed. The initial recording area 81I corresponds to an identification signal unique to the magneto-optical disk 81, and an unrecorded area 81N exists between the initial recording areas 81I.

This magneto-optical disk 81 is formed by laminating a silicon nitride layer of about 80 nm on a plastic substrate such as polycarbonate (PC), and forming a layer of about 30 nm of TbFeCo.
The magneto-optical disk has a configuration in which a magneto-optical recording layer having a thickness of m is laminated, a silicon nitride layer having a thickness of about 50 nm is laminated, and an aluminum layer having a thickness of about 30 nm is further laminated.

The identification signal is recorded on the magneto-optical disk 81 at a relatively low linear velocity of about 1 to about 2 m / s.
A laser light having a wavelength λ of about 680 nm and an optical system (or an objective lens) having a numerical aperture NA of about 0.55;
A laser beam (heat treatment laser beam) is irradiated at a high laser power of about 15 to about 20 mW. A heat treatment for reducing the magnitude of the magnetization generated during magneto-optical recording by irradiation with the laser light to a level that does not disappear is performed in a predetermined pattern, and an identification signal is recorded based on a difference in the figure of merit corresponding to the predetermined pattern. As an example, the heat treatment may be a heat treatment that lowers the coercive force of the recording layer. The figure of merit corresponds to the product of the reflectance of the magneto-optical disk 81 and the Kerr rotation angle. Recording of the identification signal is preferably performed by an optical modulation method of turning on / off a laser beam in accordance with the identification signal. In addition, a state where the phases are aligned with reference to pits formed in the magneto-optical disk 81 in advance (or the phase is controlled) State)
Preferably, the identification signal is recorded.

The temperature of the heat treatment at the time of recording the identification signal is determined by the irradiation of the recording laser light when the signal is rewritable by the recording laser light in the magneto-optical recording device of the magneto-optical disk 81. Thus, the temperature of the recording layer of the magneto-optical disk 81 is set higher than the temperature at which the temperature can be raised.
In the magneto-optical reproducing device 190, the rotation speed of the magneto-optical disk 81 may be reduced so that the temperature of the heat treatment can be obtained.

In FIG. 4B, carrier recording areas 81C and 81C 'are formed on tracks 81T of the initialized magneto-optical disk 81 shown in FIG. 4A. The carrier recording area 81C is an unrecorded area 8 of the track 81T.
This is a carrier signal recording area formed on 1N. The carrier recording area 81C 'is a recording area of the carrier signal formed on the initial recording area 81I of the track 81T. The recording of the carrier signal is made to conform to a normal condition for magneto-optical recording of a signal in a rewritable manner in the user area.
For example, magneto-optical recording is performed by irradiating a recording laser beam with a laser power of about 5 to about 7 mW at a linear velocity of about 1 to about 2 m / s.

The frequency of the carrier signal is preferably about 10 to about 20 times the frequency of the identification signal in order to increase the stability of the reproduced signal. As an example, when the frequency of the identification signal is about 300 kHz or less, the frequency of the carrier signal is about 4 MHz or less so as to satisfy the above-described about 10 to about 20 times. The initial recording area 81I may be formed in the lead-in area and / or the lead-out area.
It may be formed in an area of OC (Table Of Contents). In the lead-in area and the lead-out area where no magneto-optical signal is recorded, an initial recording area 81 is provided.
When I is formed, it is suitable for writing and erasing a carrier signal.

FIG. 5 shows the magneto-optical disk 81 shown in FIG.
FIG. 6 is an example of a waveform diagram of a reproduced signal MO when a carrier signal is reproduced from FIG. As shown in the waveform diagram of FIG. 5, when the carrier signal recorded on the initialized magneto-optical disk 81 is reproduced, the amplitude of the reproduced signal fluctuates and resembles the waveform of the amplitude-modulated (AM) signal. A reproduction waveform is obtained.
The fluctuation of the amplitude of the reproduction signal MO corresponds to the identification signal recorded on the track 81T, and the initial recording area 81I
This is because the amplitude of the reproduction signal corresponding to the carrier recording area 81C ′ formed thereon is smaller than the amplitude of the reproduction signal corresponding to the carrier recording area 81C formed on the unrecorded area 81N.

The degree to which the amplitude of the reproduction signal MO is reduced depends on the recording power of the identification signal, and utilizes the fact that the Kerr rotation angle θk of the heat-treated portion irradiated with the laser at high power is reduced. However, instead of eliminating magnetization by high-power laser irradiation, and not setting the Kerr rotation angle θk to zero, positive and negative Kerr rotation angles (+ θk, −θk)
Is caused. The initial recording area 81I of the magneto-optical disk 81 and its periphery are magnetized in a certain direction and irradiated with a reproducing laser beam, and a magneto-optical reproducing signal corresponding to the reproducing laser light reflected by the magneto-optical disk 81 is generated. In the magneto-optical reproducing method in which the magnetic reproduction signal is set to 1 when the average value is larger than the average value and set to 0 when the magnetic reproduction signal is smaller than the average value, it is possible to reproduce the magneto-optically recorded signal. However, in this magneto-optical reproducing method, it is not possible to reproduce the identification signal recorded by performing the heat treatment in the predetermined pattern.

For this reason, when the reproduction signal MO whose amplitude changes as shown in FIG. 5 is supplied to the identification signal detection circuit 180, the identification signal detection circuit 180 detects the fluctuation of the amplitude of the reproduction signal MO or the envelope (envelope). The identification signal is detected based on the detection result, and the detection result is output to the control circuit 170. When the identification signal is supplied from the identification signal detection circuit 180, the control circuit 170 determines that the magneto-optical disk 81 is a genuine product, permits magneto-optical reproduction of the recorded data, and If no signal is supplied, it is determined that the magneto-optical disk 81 is a duplicate product, and magneto-optical reproduction of recorded data thereafter is prohibited.

Further, the control circuit 170 erases the carrier signal recorded on the track 81T after the irradiation of the reproducing laser beam (for example, after determining whether or not the magneto-optical reproduction is permitted). By erasing the carrier signal, the security of the magneto-optical disk 81 and the magneto-optical reproducing device 190 can be improved.

FIG. 6 is a schematic block diagram showing the identification signal detection circuit in FIG. Identification signal detection circuit 18
0 has an envelope detection circuit 181, an integrator 182, a binarization circuit 183, a PLL circuit 184, and a frequency divider 185.

The PLL circuit 184 is supplied with the reproduction signal MO from the generation circuit 160, generates the first synchronization signal S184 at the cycle of the carrier signal included in the reproduction signal MO, and envelopes the first synchronization signal S184 with the envelope. It is supplied to the detection circuit 181 and the frequency divider 185.

The reproduction signal MO and the first synchronization signal S184 are supplied to the envelope detection circuit 181. The envelope detection circuit 181 detects the envelope of the reproduction signal MO based on the first synchronization signal S184, and generates a detection signal S181. This detection signal S181 is output to the integrating circuit 182. As the detection signal S181,
It may be a signal indicating the detection of the fluctuation itself, or a signal indicating the envelope.

The integrating circuit 182 includes an envelope detecting circuit 181
Is integrated to generate an integration signal S182, and the integration signal S182 is supplied to a binarization circuit 183. For example, when the heat treatment is repeatedly performed in a predetermined pattern and the same identification signal is repeatedly recorded on the track 81T, it is possible to improve the detection accuracy of the identification signal by integrating the number of times the detection signal S181 is supplied. . In addition, when the recording area of the identification signal is repeatedly irradiated with the reproduction laser light, the detection signal S181 can be integrated to increase the number of times of supply of the detection signal, thereby improving the detection accuracy of the identification signal.

The frequency divider 185 generates the first synchronization signal S184
Is divided to generate a second synchronization signal S185.
Is supplied to the binarization circuit 183.

The binarizing circuit 183 generates the second synchronizing signal S1
85 and the integration signal S182 are supplied, and the integration signal S1
When the integrated value indicated by 82 is equal to or larger than a preset threshold value, the identification signal is detected, and the detected identification signal is supplied to the control circuit 170.

The identification signal detection circuit 180 detects the identification signal recorded on the magneto-optical disk 81 from the reproduction signal MO using the carrier signal of a fixed period, so that the detection accuracy of the identification signal can be increased. . Integration circuit 182
By performing the integration processing in, it is possible to further increase the detection accuracy.

FIG. 7 is an explanatory diagram showing a recording layer when a carrier signal is recorded on an uninitialized magneto-optical disk 81 '. Incidentally, the magneto-optical disks 81, 81 '
The point of initialization is different.

Track 8 of magneto-optical disk 81 'in FIG.
In 1T ', a carrier signal having a constant period is recorded. The carrier recording area 81C in FIG.
This is a carrier signal recording area formed on the unrecorded area 81N of T '. The recording of the carrier signal is made to conform to a normal condition for magneto-optical recording of a signal in the user area.
For example, recording is performed with a recording laser beam having a laser power of about 5 to about 7 mW at a linear velocity of about 1 to about 2 m / s.

FIG. 8 is an example of a waveform diagram of a reproduced signal MO when a carrier signal is reproduced from the magneto-optical disk 81 'of FIG. As shown in the waveform diagram of FIG. 8, when the carrier signal recorded on the uninitialized magneto-optical disk 81 'is reproduced, the amplitude of the reproduced signal MO is constant.

Therefore, when the reproduction signal MO having the constant amplitude is supplied to the identification signal detection circuit 180, the identification signal detection circuit 180 does not detect the fluctuation of the amplitude of the reproduction signal MO and supplies the identification signal to the control circuit 170. Not done. Control circuit 17
In the case of 0, since the identification signal is not supplied from the identification signal detection circuit 180, it is determined that the magneto-optical disk 81 'is a duplicate product, and the reproduction of the recorded data thereafter is prohibited.

FIG. 9 is a schematic flowchart showing the reproducing process of the identification signal performed by the magneto-optical reproducing device of FIG.
First, in step S1, the control circuit 170 drives the optical pickup 150 and the magnetic head 20 via the laser drive circuit 155 and the magnetic head drive circuit 25, and records data on the track 81T of the initialized magneto-optical disk 81. And a carrier signal having a constant period is magneto-optically recorded using an optical modulation method or the like. The irradiation of the recording laser light is performed on the track 81T in the area where the initial recording area 81I is formed and the identification signal is recorded.

In step S2, the control circuit 170 drives the optical pickup 150 via the laser drive circuit 155, and irradiates the track 81T of the magneto-optical disk 81 with a reproducing laser beam. Irradiation of the reproduction laser beam is performed on the track 81T where the carrier signal is magneto-optically recorded in the area where the initial recording area 81I is formed and the identification signal is recorded.

In step S 3, light receiving signals SA to SF based on the reproduction laser light reflected on the magneto-optical disk 81 are supplied from the optical pickup 150 to the generation circuit 160. The generation circuit 160 generates a reproduction signal (magneto-optical reproduction signal) MO composed of a magneto-optical signal based on the light receiving signals SA to SF, and supplies the reproduction signal MO to the information detection circuit 165 and the identification signal detection circuit 180. Information detection circuit 160
Detects the carrier signal, but does not output it as the output signal So under the control of the control circuit 170.

In step S4, the identification signal detecting circuit 18
0 performs the detection operation of the identification signal based on the fluctuation (or envelope) of the amplitude of the reproduction signal MO. For example, when the same identification signal is repeatedly recorded on the track 81T, the detection accuracy of the identification signal can be improved by detecting the identification signal based on the number of times of detection of the amplitude change. In addition, when the recording area of the identification signal is repeatedly irradiated with the reproduction laser beam, the identification signal is detected based on the number of times of detection of the fluctuation of the amplitude, so that the detection accuracy of the identification signal can be improved.

In step S5, control circuit 170 determines whether or not an identification signal has been supplied from identification signal detection circuit 180 and / or whether or not a signal indicating detection of the identification signal has been supplied. Is detected. If the identification signal is detected, the process proceeds to step S6, and the subsequent magneto-optical reproduction is permitted. If no identification signal has been detected, the process proceeds to step S7.

In step S7, the control circuit 170 stops the output of the reproduction laser beam via the laser drive circuit 155, and prohibits the subsequent magneto-optical reproduction. Further, the output of the output signal So of the information detection circuit 165 is prohibited. It is to be noted that a display may be provided in the magneto-optical reproducing device 190 to perform a display indicating that an identification signal is not detected or a display of a disk error.

At step S 8, the control circuit 170 drives the optical pickup 150 and the magnetic head 20 via the laser drive circuit 155 and the magnetic head drive circuit 25, and erases the carrier signal from the magneto-optical disk 81.

In the above flowchart, the carrier signal is magneto-optically recorded in the recording area of the identification signal, and the reproduction signal MO is recorded.
The identification signal is detected from the fluctuation of the amplitude of the signal. However,
When the content is magneto-optically recorded in the recording area of the identification signal, the identification signal detection circuit 180 detects the identification signal from the fluctuation of the amplitude of the reproduction signal MO, and the information detection circuit 165 detects the content from the reproduction signal MO. May be output as an output signal So. In this case, writing and erasing of a carrier signal is not required.

As described above, the magneto-optical disk 8
In No. 1, it is possible to record an identification signal that can be used for duplication prevention or the like by performing a heat treatment by increasing the recording power of a laser beam. Further, since the identification signal recorded as described above cannot be detected by a magneto-optical reproducing device used by a general user, duplication of the magneto-optical disk 81 on which the identification signal is recorded can be made difficult. The above embodiment is an exemplification of the present invention, and the present invention is not limited to the above embodiment.

[0085]

As described above, according to the present invention, it is possible to provide a magneto-optical recording medium in which an identification signal is recorded without losing magnetization, and the identification signal is transmitted from the magneto-optical recording medium. A playback device and a playback method that can be played back can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an embodiment of a reproducing apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing an optical pickup in FIG.

FIG. 3 is an explanatory diagram illustrating a configuration of a light receiving unit of the photodetector in FIG.

FIG. 4 is an explanatory view in which a recording layer of a magneto-optical disk used in the magneto-optical reproducing device of FIG. 1 is partially enlarged.

FIG. 5 is a waveform diagram of a reproduction signal MO when a carrier signal is reproduced from the magneto-optical disk 81 of FIG. 4B.

FIG. 6 is a schematic block diagram illustrating an identification signal detection circuit in FIG. 1;

FIG. 7 is an explanatory view showing a partially enlarged recording layer when a carrier signal is recorded on an uninitialized magneto-optical disk 81 ′.

8 is a waveform diagram of a reproduced signal MO when a carrier signal is reproduced from the magneto-optical disk 81 'of FIG.

9 is a schematic flowchart showing a method of reproducing an identification signal performed by the magneto-optical reproducing device of FIG.

[Explanation of symbols]

2 ... Objective lens, 2F ... Focusing actuator, 2H ... Lens holder, 2T ... Tracking actuator, 3 ... Beam splitter, 4 ... Semiconductor laser (laser), 5 ... Collimator lens, 6 ... Condenser lens,
7 ... Cylindrical lens, 15 ... Wollaston prism, 18 ...
Photodetectors, 18A to 18D: divided areas, 18E: first sub-light receiving section, 18F: second sub-light receiving section, 18S: main light receiving section, 18Sx, 18Sy: dividing line, 20: magnetic head,
25 ... magnetic head drive circuit, 30 ... motor, 35 ... motor drive circuit, 40 ... phase compensation circuit, 42 ... amplification circuit, 8
1, 81 ': magneto-optical disk (magneto-optical recording medium), 81
C, 81C ': carrier recording area, 81I: initial recording area, 81N: unrecorded area, 81T, 81T': track, 150: optical pickup, 152: amplifier circuit (head amplifier), 155: laser drive circuit, 160 ... Generation circuit, 165: information detection circuit, 170: control circuit, 180
... Identification signal detection circuit, 181 ... Envelope detection circuit, 182
····················································································· 積 算 ·······… · ··· 積 算 積 算
B: Laser beam, MB: Line of magnetic force, MS, SSE, SS
F: beam spot, MO: reproduction signal (magneto-optical reproduction signal), Sfe, Ste: drive signal, t: time, TE: tracking error signal.

Claims (19)

[Claims] 1. A magneto-optical recording medium having a recording layer on a substrate, wherein the recording layer is subjected to a heat treatment in a predetermined pattern to reduce the magnitude of magnetization generated during magneto-optical recording to a level that does not disappear. A magneto-optical recording medium on which an identification signal is recorded by a difference in a figure of merit corresponding to the predetermined pattern; 2. The magneto-optical recording medium is a magneto-optical disk, and the temperature of the heat treatment is set when the magneto-optical recording device of the magneto-optical disk performs magneto-optical recording of a signal so as to be rewritable by laser light. 2. The magneto-optical recording medium according to claim 1, wherein the temperature is higher than a temperature at which a temperature of a recording layer of the magneto-optical disk can be raised by irradiation with a laser beam. 3. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is a magneto-optical disk, and the track of the magneto-optical disk is subjected to the heat treatment in the predetermined pattern. 4. The magneto-optical recording medium according to claim 1, wherein said magneto-optical recording medium is a magneto-optical disk, and said heat treatment is repeatedly performed on tracks of said magneto-optical disk in said predetermined pattern. 5. The magneto-optical recording medium according to claim 1, wherein the recording area of the identification signal in the recording layer is magneto-optically recorded with a content. 6. A substrate having a recording layer on which heat treatment for reducing the magnitude of magnetization generated during magneto-optical recording is performed so as not to be lost in a predetermined pattern on a substrate, and a difference in a figure of merit corresponding to the predetermined pattern. A laser for irradiating a reproducing laser beam to a magneto-optical recording medium in which a predetermined signal is magneto-optically recorded in an area where an identification signal is recorded, and a reproducing laser beam reflected by the magneto-optical recording medium. A reproduction apparatus comprising: a generation circuit that generates a reproduction signal composed of a magneto-optical signal; and an identification signal detection circuit that detects the identification signal based on a change in amplitude of the reproduction signal. 7. A magneto-optical recording medium further comprising: a magnetic head for applying a magnetic field to a portion where magneto-optical recording is performed during magneto-optical recording of a signal on the magneto-optical recording medium, wherein the magneto-optical recording medium is a magneto-optical disk The laser and the magnetic head each have a recording layer on the substrate, in which the heat treatment is performed on tracks in the predetermined pattern, and an identification signal is recorded based on a difference in the figure of merit corresponding to the predetermined pattern. On the track of the magneto-optical disk, the predetermined signal is magneto-optically recorded, and after the magneto-optical recording of the predetermined signal, the laser irradiates the reproduction laser beam on the track of the magneto-optical disk, 7. The reproducing apparatus according to claim 6, wherein a cycle of the predetermined signal is smaller than a half of a cycle of the predetermined pattern formed on a track of the magneto-optical disk. 8. The predetermined signal has a fixed period, and the fixed period is about 0.1 times to about 0.5 times a period of the predetermined pattern formed on a track of the magneto-optical disk.
8. The reproducing apparatus according to claim 7, wherein the distance is within a range of twice. 9. An identification signal detection circuit comprising: an envelope detection circuit for detecting a change in amplitude of the reproduction signal; an integration circuit for integrating output signals of the envelope detection circuit; and an output signal of the integration circuit. A binarization circuit for detecting the identification signal based on the integrated value and a preset threshold value, wherein the track of the magneto-optical disk is repeatedly subjected to the heat treatment in the predetermined pattern. The playback device according to claim 7. 10. The reproducing apparatus according to claim 7, wherein said laser and said magnetic head erase said magneto-optically recorded predetermined signal after irradiation with said reproducing laser beam. 11. An information detecting circuit for detecting the predetermined signal based on the reproduction signal, wherein a content of the magneto-optical recording medium is stored in the recording area of the identification signal in the recording layer. 7. The reproducing apparatus according to claim 6, wherein the signal is magneto-optically recorded as the signal. 12. The magneto-optical recording medium is a magneto-optical disk, and the temperature of the heat treatment is set when a magneto-optical recording apparatus for the magneto-optical disk performs magneto-optical recording of a signal so as to be rewritable by laser light. 7. The reproducing apparatus according to claim 6, wherein the temperature is higher than a temperature at which the recording layer of the magneto-optical disk can be heated by the irradiation of the laser beam. 13. A substrate having a recording layer on which heat treatment for reducing the magnitude of magnetization generated during magneto-optical recording is performed so as not to be lost in a predetermined pattern, and a difference in a figure of merit corresponding to the predetermined pattern. A reproducing method for reproducing the identification signal from a magneto-optical recording medium on which the identification signal is recorded, wherein: a step of magneto-optically recording a predetermined signal on the magneto-optical recording medium; Irradiating the laser beam for reproduction with a laser beam; generating a reproduction signal composed of a magneto-optical signal corresponding to the laser beam for reproduction reflected on the magneto-optical recording medium; and Detecting the identification signal. 14. The magneto-optical recording medium is a magneto-optical disk, wherein the tracks of the magneto-optical disk are subjected to the heat treatment in the predetermined pattern, and the predetermined signal period is determined by the magneto-optical disk. The size of the predetermined pattern formed on the track of the disk is less than half of the period, and in the magneto-optical recording step, the predetermined signal is magneto-optically recorded on the track of the magneto-optical disk; 14. The reproducing method according to claim 13, wherein, in the step of irradiating the laser light, a track of the magneto-optical disk is irradiated with a reproducing laser light. 15. The predetermined signal has a fixed period,
15. The reproducing method according to claim 14, wherein the predetermined period is in a range of about 0.1 to about 0.2 times a period of the predetermined pattern formed on a track of the magneto-optical disk. 16. The recording layer of the magneto-optical recording medium, wherein the heat treatment is repeatedly performed in the predetermined pattern, and in the step of detecting the identification signal, the number of times of detecting the change in the amplitude of the reproduction signal is detected. 14. The reproducing method according to claim 13, wherein the identification signal is detected based on the following. 17. The step of irradiating the reproduction laser light with the reproduction laser light repeatedly irradiating a recording area of the identification signal in the recording layer, and detecting the identification signal, 14. The reproducing method according to claim 13, wherein the identification signal is detected based on the number of times the amplitude of the reproduced signal is detected. 18. The reproducing method according to claim 13, further comprising the step of erasing said predetermined signal magneto-optically recorded after irradiating said reproducing laser beam. 19. The magneto-optical recording medium is a magneto-optical disk, and the temperature of the heat treatment is set when a signal is rewritable by laser light in a magneto-optical recording device of the magneto-optical disk. 14. The reproducing method according to claim 13, wherein the temperature is higher than a temperature at which the recording layer of the magneto-optical disk can be heated by the irradiation of the laser beam.