JP2576625B2 - Magneto-optical overwrite device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic field modulation overwrite device in a magneto-optical disk device.

[Conventional technology]

In the magneto-optical disk device, a thermo-magnetic recording method is conventionally used in which information is recorded by modulating a laser beam, and then condensing and irradiating a recording medium made of a magnetic thin film to record information as a change in perpendicular magnetization on the recording medium. ing. At this time, it is necessary that the direction of magnetization of the magneto-optical disk is initialized in advance on the recording medium, which is called initialization. Further, at the time of recording, it is necessary to apply an external bias magnetic field on the surface of the recording medium and a static magnetic field opposite to the initialization direction.

On the other hand, for reproducing information, a method of magneto-optically reproducing a perpendicular magnetization pattern (information data string) on a magneto-optical disk medium using the Kerr effect of a magnetic thin film is used.

These methods are basically the same as those of a conventional apparatus using an optical disk called a changeable reflectance recording medium. However, since a magneto-optical disk uses a magnetic thin film, it has a function of rewriting information, and some have high functionality. However, the magneto-optical disk has a disadvantage that it does not have the overwrite function of the magnetic disk. For this reason, the disk rotation waiting time is more than twice as long as that of the magnetic disk during the period from recording and verifying of information to rewriting, resulting in a disadvantage that the throughput is extremely deteriorated.

Therefore, a method called a magnetic field modulation method capable of overwriting information has been considered. This is a method of modulating a magnetic field coil (hereinafter referred to as a magnetic head) for generating an external bias magnetic field with an information signal, unlike the method of optically modulating the laser light described above. At this time, the laser beam condensed on the recording medium is irradiated only to give heat necessary for recording. Since this method uses a magnetic head, overwriting can be easily realized.

[Problems to be solved by the invention]

The magnetic field modulation method requires a magnetic head to have a low impedance up to a high frequency range and a configuration capable of applying a generated magnetic field of, for example, 1500 e or more to a high frequency range on a recording medium surface.

Therefore, two types of magnetic field modulation methods, a floating magnetic head method and a fixed magnetic head method, can be considered. In the floating magnetic head system, overwriting can be performed by applying a recording modulation magnetic field while flying over a recording medium surface while maintaining a spacing of several μm by a magnetic head slider used for a fixed magnetic disk. On the other hand, in the fixed magnetic head method, overwriting can be performed by applying a recording modulation magnetic field fixed at a position separated from the recording medium surface by several tens μm or more.

However, both methods have various disadvantages.
First, in order to drive a magnetic head at a high frequency to obtain a recording magnetic field intensity necessary for recording information, a configuration is employed in which the magnetic head is brought very close to a recording medium of a magneto-optical disk. That is, both types have a disadvantage that only a single-sided disk can be used as a magneto-optical disk. In addition, the flying magnetic head method has a drawback such as a head crash like a fixed magnetic disk, and is inferior in reliability. On the other hand, the fixed magnetic head method has no drawback of head crash because it is far from the surface of the recording medium, but has a drawback that the recording magnetic field intensity fluctuates significantly due to the distance fluctuation due to the surface deflection of the disk medium. . For this reason, the instability of the recording pit increases, which causes jitter fluctuation. Further, the influence of the generated heat on the device cannot be neglected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical overwrite device which can stably and satisfactorily overwrite information using a magneto-optical disk medium on both sides by improving the above-mentioned drawbacks.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a magneto-optical overwrite device of a magneto-optical recording / reproducing system for performing overwriting of information using a magnetic field modulation means, comprising a modulator for modulating a source information signal according to a coding rule. A phase modulation circuit system that changes a phase of a clock that is equal to or shorter than a transition time of a recording data clock in accordance with a transition of a multilevel data sequence that is the modulated recording information signal in accordance with a code of the multilevel data sequence. A magnetic field modulation coil system having a resonance frequency that matches a carrier frequency of phase modulation input from the phase modulation circuit system; a means for optically and magnetically reproducing; and a phase for demodulating the read phase modulation signal. A demodulator for demodulating the source information signal according to the coding rule, and performing a magnetic field modulation overwrite using phase modulation. Those were.

[Action]

According to the present invention, since the magnetic head forms a resonance circuit including the inductor and the capacitor, the generated magnetic field is a strong high-frequency magnetic field having a constant resonance frequency. Since the intensity of the magnetic field generated from the magnetic head can be much higher than that of the above-described conventional magnetic head, the magnetic head can be located farther from the surface of the magneto-optical disk medium than ever before. Therefore, a standardized double-sided disc can be used as it is. Since the high-frequency magnetic field according to the present invention can only generate a constant high-frequency magnetic field, the signal recorded on the recording medium is obtained by modulating information data in a burst. When recording binary data, modulation is performed in such a manner that the phase of the frequency is shifted by π in accordance with the binary data and can be applied to the magnetic head in a superimposed manner. For this reason, at the time of reproducing the information, the area where the phase modulation recording according to the information signal is read is read and the information is reproduced. Therefore, overwriting can be realized with a phase-modulated high-frequency magnetic field.

〔Example〕

 FIG. 1 is a block diagram showing one embodiment of the present invention.

Here, a magneto-optical disk system that performs recording and reproduction using a binary data string will be described as an example. The magneto-optical overwrite device according to the present embodiment includes a modulator 1 that modulates a source information signal according to a coding rule, and a phase modulation that performs two-phase modulation of a binary data sequence that is a recording information signal modulated by the modulator 1. A circuit system 2, a magnetic field modulation coil system 3 having a resonance frequency matching the carrier frequency of the phase modulation input from the phase modulation circuit system 2, and a magneto-optical head system for performing magneto-optical reproduction from the magneto-optical disk system 4. 5, an LD (laser diode) drive circuit 6, a reproduction amplifier 7, a servo processing system 8, a phase demodulation circuit system 9 for demodulating the read phase modulation signal, and a source information signal according to the encoding rule. And a demodulator 10 for demodulation.

The phase modulation circuit system 2 has a function of superimposing and applying to a magnetic head a high-frequency current subjected to two-phase modulation in accordance with binary data of a recording information signal. At this time, the magnetic field modulation coil system 3 is 2
The frequency of the phase-modulated recording information signal is set to be the resonance frequency.

That is, when the binary codes “1” and “0” are recorded,
The phase of the carrier can be set to have 0 degree and 180 degrees. When recording the quaternary code “3”, “2”, “1”, “0”, the phase of the carrier is 0 degree, 90 degrees, 180 degrees.
Degrees, can be set to use 270 degrees. Also, taking the case of quaternary data as an example, as a specific configuration example, combinations of quaternary data series (0,0), (0,1), (1,0),
In (1,1), a serial modulation circuit for driving the 0-π modulator and the 0-π / 2 modulator may be used. This may use a general method used in wireless PCM transmission.

FIG. 2 is a diagram showing an example of the magnetic field modulation coil system 3 of FIG. The magnetic field modulation coil system 3 is composed of an inductor 20 shaped to generate a high-frequency magnetic field and applied to the surface of the magneto-optical recording medium, and a capacitor 21 forming a resonance circuit. As a result, the high-frequency magnetic field generated from the inductor 20 is limited to the vicinity of the resonance frequency. Resonance frequency is defined by the capacitance C of the inductance L ₁ and the capacitor 21 of the inductor 20 as indicated by the following equation.

As described above, since the inductance L of the inductor can be made apparent at the resonance frequency, the magnetic field modulation coil has only a pure resistance. Therefore, since a larger amount of current can flow at a higher frequency than a magnetic field modulation coil that does not use resonance, a strong magnetic field can be generated. This eliminates the disadvantage that a magnetic head has to be installed near the conventional magneto-optical recording film. Therefore, a high-frequency magnetic field for magnetic field modulation can be applied from the disk substrate side, and magnetic field modulation overwriting can be realized using a double-sided disk which is a standardized disk.

On the other hand, the read side of the recorded information signal has a magneto-optical head system 5, a semiconductor laser (LD) drive circuit 6, a servo processing system 8, and a reproduction amplifier 7. 7, a phase demodulation circuit 9 for demodulating the magneto-optically read two-phase modulated signal, and a demodulator 10 for reproducing the original information data sequence from the signal synchronously reproduced by the phase demodulation circuit 9. Is used.

FIG. 4 shows, as an example, the phase demodulation circuit system 9 which employs a method of synchronously detecting a read signal. The phase demodulation circuit system 9 includes a phase detection circuit 41, a carrier reproduction circuit 42, an identification reproduction circuit 43, and a timing extraction circuit 44.

Next, the operation of the magneto-optical overwrite device according to the present invention will be described with reference to the signals and waveform diagrams of FIG.

Because of the magnetic field modulation overwriting, the heat energy required for recording is obtained by a laser beam focused on a recording medium by a magneto-optical head. When recording the disk series shown in FIG. 5 (a) on a magneto-optical disk medium, the magnetic field modulation coil system 3 has a phase according to "1" and "0" of the disk as shown in FIG. 5 (b). Currents of two-phase modulation different by π are applied. This two-phase modulation signal S (t) is expressed by the following equation.

S (t) = SIN (2πFt + a _i π) When “1”; a _i = 0 When “0”; a _i = 1 At this time, the carrier F used for phase modulation is the resonance frequency of the magnetic field modulation coil system 3. Since a large amount of current can flow at a high frequency as described above, a strong high-frequency magnetic field is applied to the recording medium surface.
Therefore, the magnetization information subjected to the two-layer phase modulation shown in FIG. 5B is recorded on the recording medium. Here, the baseband frequency for data recording is set to 1/4 of the carrier frequency.

Next, it can be seen that when the data series shown in FIG. 5 (c) is overwritten on the magnetization information, it may be performed in the same manner as described above. As a result, magnetization information as shown in FIG. 5 (d) is recorded, and complete overwriting can be realized.

As described above, with the above configuration, overwriting of information can be easily realized using the two-phase phase modulation magnetic field of the recording information signal.

FIG. 3 shows a second example of the magnetic field modulation coil system 3 according to the present invention. In this example, the capacitor constituting the resonance circuit is a variable capacitor 31, which can be controlled by a signal from a capacitor control circuit (not shown). This makes it possible to flexibly cope with, for example, a change with time in the inductance of the inductor 30, for example. Also, the present invention can be applied to an apparatus of a specification in which the baseband frequency of data recording changes between the inner circumference and the outer circumference of the disk, such as the CLV method (constant linear velocity method) among the magneto-optical disk recording methods.

The above description has been made on the premise that a binary data string is used for recording and reproducing information. However, it should be noted that the present invention can be sufficiently extended to high-density recording / reproducing overwriting using multi-valued data of three or more values.

〔The invention's effect〕

As described above, in the magneto-optical overwrite device of the present invention, since the magnetic head forms a resonance circuit with the inductor and the capacitor, a very strong high-frequency magnetic field can be generated,
The magnetic head can be set farther from the surface of the magneto-optical disk medium than before. For this reason, a standardized double-sided disc can be used as it is. Therefore, it can be realized with the same device specifications as a magneto-optical disk device having no overwrite function.

In addition, since the information recording signal is recorded after being phase-modulated, there is an effect that the influence of jitter on reproduction data due to noise due to reproduction can be reduced as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a magneto-optical overwrite device of the present invention, FIG. 2 is a diagram showing an example of a magnetic field modulation coil according to the present invention, and FIG. FIG. 4 is a diagram showing a block of a phase demodulation circuit system according to the present invention, and FIG. 5 is a diagram for explaining the principle of the magneto-optical overwrite device of the present invention. DESCRIPTION OF SYMBOLS 1 ... Modulator 2 ... Phase modulation circuit system 3 ... Magnetic field modulation coil system 4 ... Magneto-optical disk system 5 ... Magneto-optical head system 6 ... LD drive circuit 7 ... Reproduction amplifier 8 ... Servo processing system 9: Phase demodulation circuit 10: Demodulator

Claims (1)

(57) [Claims] 1. A magneto-optical overwrite device of a magneto-optical recording / reproducing system for overwriting information using a magnetic field modulation means, comprising: a modulator for modulating a source information signal according to a coding rule; A phase modulation circuit system that changes the phase of a clock that is equal to or shorter than the transition time of the recording data clock in accordance with the transition of the multilevel data sequence that is a signal in accordance with the sign of the multilevel data sequence; A magnetic field modulation coil system having a resonance frequency that matches the carrier frequency of the phase modulation input from the device; a means for magneto-optically reproducing the optical signal; a phase demodulation circuit system for demodulating the read phase modulation signal; A demodulator for demodulating the source information signal in accordance with the general rule, and performing a magnetic field modulation overwrite using phase modulation. Device.