JPH0312006A - Magneto-optical overwrite system - Google Patents

Abstract

PURPOSE:To stably perform magnetic field modulation overwrite by comprising a magnetic field modulation coil system of an inductor to generate high frequency magnetic field and a capacitor forming a resonance circuit, and using digital amplitude modulation. CONSTITUTION:A binary data system modulated with a modulator 1 is digital- amplitude modulated with an amplitude modulation circuit system 2, and is inputted to a magnetic field modulation coil system 3. The magnetic field modulation coil system 3 is comprised of the inductor 20 which generates the high frequency magnetic field and arranged in shape applicable on the plane of a magneto-optical recording medium and the capacitor 21 forming the resonance circuit, and is provided with a resonance frequency coinciding with the carrier frequency of the digital amplitude modulation inputted from the digital amplitude modulation circuit 2. Therefore, it is possible to permit a current to flow much more than with a high frequency compared with a magnetic field modulation coil not using resonance, and high frequency magnetic field can be applied on the plane of the recording medium, and the magnetic field modulation overwrite can be realized by using two plane disks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic field modulation overwrite method in a magneto-optical disk device.

[Conventional technology]

Conventionally, in magneto-optical disk drives, information is recorded using a thermomagnetic recording method in which a laser beam is optically modulated and then focused onto a recording medium made of a magnetic thin film to record information as changes in perpendicular magnetization on the recording medium. It has been adopted. At this time, it is necessary to initialize the magneto-optical disk in advance, that is, to align the direction of magnetization on the recording medium. Furthermore, during recording, it is necessary to apply an external bias magnetic field on the surface of the recording medium in the opposite direction to the initialization direction.

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

These systems are basically the same as conventional devices using optical disks called write-once media of variable reflectance type. However, since magneto-optical disks use a magnetic thin film, they have the ability to rewrite information and are highly functional. However, magneto-optical disks have the disadvantage that they do not have the overwriting capability that magnetic disks have.

The waiting time for disk rotation is more than twice that of a magnetic disk between the time of data processing, information recording, verification, and rewriting, which leads to the disadvantage that throughput is extremely reduced.

Therefore, a method called a magnetic field modulation method was devised that allows information to be overwritten. This method is different from the method of optically modulating the laser beam described above, and is a method of modulating a magnetic field coil (hereinafter referred to as a magnetic head) that generates an external bias magnetic field with an information signal. At this time, the laser beam focused on the recording medium is irradiated only to provide the heat necessary for recording. Since this method uses a magnetic head, overwriting can be easily realized.

[Problem to be solved by the invention]

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

Therefore, two types of magnetic field modulation methods can be considered: a floating magnetic head method and a fixed magnetic head method.

In the floating magnetic head method, overwriting can be performed by flying a magnetic hent slider over the surface of a recording medium while maintaining a spacing of several μm and applying a recording modulation magnetic field. On the other hand, in the fixed magnetic head method, overwriting can be performed by fixing the head at a position several tens of micrometers or more away from the surface of the recording medium and applying a recording modulation magnetic field.

However, both methods have various drawbacks. First, in order to obtain the recording magnetic field strength necessary for recording information by driving the magnetic head with high frequency, the magnetic head is configured to be placed very close to the recording medium of the magneto-optical disk. That is, both types have the disadvantage that only single-sided disks can be used as magneto-optical disks. Furthermore, the floating magnetic head system has the same drawbacks as fixed magnetic disks, such as head crashes, and is inferior in terms of reliability.

On the other hand, fixed magnetic heads do not have the disadvantage of head crashes because they are located far from the surface of the recording medium, but they do have the disadvantage of noticeable fluctuations in recording magnetic field strength due to distance fluctuations due to surface runout of the disk medium. . This increases the instability of recorded bits and causes jitter fluctuations. Furthermore, the effect of the generated heat on the device cannot be underestimated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical overwrite system that can overwrite information stably and satisfactorily using a double-sided magneto-optical disk medium by improving the above-mentioned drawbacks.

[Means for Solving the Problems] The present invention provides a modulator that modulates a source information signal according to an encoding rule in a magneto-optical overwrite method of a magneto-optical recording and reproducing system that overwrites information using a magnetic field modulation means. an amplitude modulation circuit system that digitally amplitude modulates the multi-level data series that is the modulated recording information signal; and a magnetic field modulator having a resonant frequency that matches the carrier frequency of the digital amplitude modulation input from the amplitude modulation circuit system. a coil system, a bias magnetic field applying magnetic circuit system, a means for optically reproducing magneto-optically, an amplitude demodulation circuit system that demodulates the read digital amplitude modulation signal, and a demodulation circuit system that demodulates the source information signal according to the encoding rule. It consists of a demodulator and is characterized by performing magnetic field modulation overwriting using digital amplitude modulation.

According to the present invention, the magnetic field modulation coil system includes an inductor that generates a high-frequency 6R field and a capacitor that forms a resonant circuit, and performs magnetic field modulation overwriting using digital amplitude modulation.

The bias magnetic field applying magnetic circuit system is configured to apply a direct current bias magnetic field superimposed on the digital amplitude modulated high frequency magnetic field generated from the magnetic field modulation coil system on the medium surface.

[Effect]

According to the present invention, since the magnetic head forms a resonant circuit composed of an inductor and a capacitor, the generated magnetic field is a strong high-frequency magnetic field with a constant resonant frequency. Since the strength of the magnetic field generated from the magnetic head can be made much larger than that of the conventional magnetic head described above, it is possible to install the magnetic head further away from the surface of the magneto-optical disk medium than ever before. Therefore, the standardized double-sided disc can be used as 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 modulates the information data in a burst manner. Become something. For example, when recording binary data, a high frequency magnetic field is applied when the binary data is 1°, and the high frequency magnetic field is blocked when the binary data is 0°.At this time, a DC magnetic field is applied as a bias magnetic field. By creating a configuration that can be superimposed,
Digital amplitude modulation can be efficiently realized. For this reason,
When reproducing information, the area recorded with digital amplitude modulation according to the information signal is read out and the information is reproduced.

Therefore, overwriting can be achieved using a digital amplitude 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 method of this embodiment includes a modulator 1 that modulates a source information signal according to an encoding rule, and a digital amplitude modulation system that digitally modulates a binary data sequence, which is a recorded information signal modulated by the modulator 1. a circuit system 2, a magnetic field modulation coil system 3 having a resonant frequency that matches the carrier frequency of digital amplitude modulation input from the digital amplitude modulation circuit system 2, and a magneto-optical coil system 3 for optically reproducing data from a magneto-optical disk system 4. A head system 5, an LD (laser diode) drive circuit 6, a reproducing amplifier 7, a servo processing system 8, and a digital amplitude demodulation circuit system 9 that demodulates the read digital amplitude modulation signal.
and a demodulator 10 that demodulates the source information signal according to the encoding rule.

The digital amplitude modulation circuit system 2 has a function of superimposing and applying a high frequency wave digitally amplitude modulated according to the binary data of the recording information signal to the magnetic head.

At this time, the magnetic field modulation coil system 3 is set so that the carrier frequency of the amplitude-modulated recording information signal becomes the resonance frequency.

FIG. 2 is a diagram showing an example of the magnetic field modulation coil system 3 of FIG. 1. This magnetic field modulation coil system 3 is composed of an inductor 20 shaped into a shape capable of generating a high frequency magnetic field and applying it onto the surface of the magneto-optical recording medium, and a capacitor forming a resonant circuit. As a result, the high frequency magnetic field generated from the inductor 20 is limited to the vicinity of the resonance frequency. The resonant frequency is defined by the inductance L of the inductor 20 and the capacitance CI of the capacitor 21, as shown by the following equation.

F=1/(2πF) In this way, the inductance L of the inductor can be apparently eliminated at the resonance frequency, so that the magnetic field modulation coil is made up of only pure resistance. Therefore, since a larger amount of current can flow at a higher frequency than in a magnetic field modulation coil that does not utilize resonance, a strong magnetic field can be generated. This eliminates the conventional disadvantage of having to install a magnetic head near the magneto-optical recording film.

Also, according to this digital amplitude modulation method, data “0”
”, no magnetic field is applied, which leads to an increase in reproduction noise. Therefore, a bias magnetic field applying magnetic circuit system disposed in the magneto-optical disk system 4 applies a DC magnetic field onto the medium surface in the form of superimposing it on a high-frequency magnetic field. It is structured as follows.

Therefore, it is possible to apply a high-frequency magnetic field for magnetic field modulation from the disk substrate side, and since the magnetic field is superimposed on the medium surface, the magnetic field modulation coil can be driven at high speed with a small amount of current, and magnetic field modulation overwrite can be performed using a double-sided disk that is a standardized disk. can be realized. .

On the other hand, on the reading side of the recorded information signal, the magneto-optical head system 5
, a semiconductor laser (LD) drive circuit 6, a servo processing system 8, and a reproduction amplifier 7. For information reproduction, a digital amplitude modulation signal read out magneto-optically from the reproduction amplifier 7 is used. a digital amplitude demodulation circuit system 9 that demodulates the
A demodulator 10 is used to reproduce the original information data sequence from the signal synchronously reproduced by the digital amplitude demodulation circuit system 9.

As an example of the digital amplitude demodulation circuit system 9, FIG.
The data sequence is demodulated by a wave detector and a synchronous detection method is used by a clock extraction circuit. The digital amplitude demodulation circuit system 9 includes an ASK detector 41, a data discriminator 42, and a timing extraction circuit 43.

Each time the original information data sequence is reproduced by the demodulator 10 from the signal synchronously reproduced by the digital amplitude demodulation circuit system 9.

Next, the operation of the magneto-optical overwrite method according to the present invention is as follows.
This will be explained with reference to the signal and waveform diagram in FIG.

Since magnetic field modulation overwriting is used, the thermal energy necessary for recording is obtained by laser light focused onto the recording medium by a magneto-optical head. When recording the data series shown in FIG. 5(a) on the magneto-optical disk medium, the magnetic field modulation coil system 3 has the following data "°1" and "0°" as shown in FIG. 5(b). This digital amplitude modulation signal S (t), which causes a current to flow for digital amplitude modulation of the amplitude, is expressed by the following equation.

S (t)=a (t)cos (2πFt)a (t
)=1; (-T/2≦L≦T/2)a(t)=0
(t<-T/2 and T/2<L) At this time, the carrier frequency F used for digital amplitude modulation is set to the resonance frequency of the magnetic field modulation coil system 3, so as mentioned above, the carrier frequency F used for digital amplitude modulation is set to the resonance frequency of the magnetic field modulation coil system 3, so Since a large amount of current can flow, a strong high-frequency magnetic field is applied to the surface of the recording medium. Therefore, the digital amplitude modulated signal shown in FIG. 5(b) is recorded on the recording medium as magnetization information. Here, the baseband frequency for data recording is set to 1/4 of the carrier frequency F.

At this time, since the current shown in FIG. 5(b) is passed through the magnetic field modulation coil system 3, reproduction noise will increase as a result if there is no bias magnetic field in the area where there is no data. However, since the structure is such that the bias magnetic field applying magnetic circuit system disposed in the magneto-optical disk system 4 applies a direct current magnetic field to the medium surface in the form of superimposing a high frequency magnetic field, areas with no data are, for example, Magnetization directed downward will be recorded.

Next, when overwriting the data series of FIG. 5(C) on this magnetization information, it can be seen that the same method as described above can be used. As a result, magnetization information as shown in FIG. 5(d) is recorded, and complete overwriting can be realized.

In this manner, with the above configuration, overwriting of information can be easily realized using the digital amplitude variation 1AWL 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 resonant 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 deal with changes in the inductance of the inductor 30 over time, for example. Also, among magneto-optical disk recording systems, CLV (constant linear velocity), etc. It can also be applied to devices with specifications that change the baseband frequency for data recording.

Although the above description has been made on the assumption that a binary data string is used for recording and reproducing information, it is sufficiently expandable to high-density recording and reproducing overwriting using multivalued data of three or more values.

[Effects of the Invention] As explained above, in the magneto-optical overwriting method of the present invention, since the Le 11 head forms a resonant circuit with an inductor and a capacitor, it is possible to generate a very strong high-frequency magnetic field, and it is possible to From this perspective, it is possible to install the magnetic head further away than in the past. Furthermore, since the configuration is such that a direct current magnetic field can be applied and superimposed as a bias magnetic field, digital amplitude modulation using a high frequency magnetic field can be efficiently realized. For this reason, the current flowing through the magnetic field modulation coil system can be reduced, enabling high-speed driving, and at the same time, double-sided disks with standardized specifications can be used as is. Therefore, the present invention can be realized with a device whose specifications are comparable to those of a magneto-optical disk device that does not have an overwrite function.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the magneto-optical overwrite method of the present invention, FIG. 2 is a diagram showing an example of an n-field modulation coil system according to the present invention, and FIG. 3 is a diagram showing a magnetic field modulation coil according to the present invention. FIG. 4 is a diagram showing a block diagram of the digital amplitude demodulation circuit system according to the present invention; FIG. 5 is a diagram for explaining the principle of the magneto-optical overwrite system of the present invention. . 1...Modulator 2...Discicle amplitude 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 ...Digital amplitude demodulation circuit system 10 ...
demodulator

Claims (3)

[Claims] (1) In a magneto-optical overwrite method of a magneto-optical recording and reproducing system that overwrites information using a magnetic field modulation means, a modulator that modulates a source information signal according to an encoding rule, and the modulated recorded information signal an amplitude modulation circuit system that performs digital amplitude modulation on a certain multi-value data series; a magnetic field modulation coil system having a resonant frequency that matches the carrier frequency of the digital amplitude modulation input from the amplitude modulation circuit system; and a bias magnetic field application magnetic circuit system. , a means for optically reproducing optically magneto-optically, an amplitude demodulation circuit system that demodulates the read digital amplitude modulation signal, and a demodulator that demodulates the source information signal according to the encoding rule, and is configured to perform digital amplitude modulation. A magneto-optical overwrite method that uses magnetic field modulation overwrite. (2) In the magneto-optical overwrite method according to claim 1, the magnetic field modulation coil system is composed of an inductor that generates a high-frequency magnetic field and a capacitor forming a resonant circuit, and performs magnetic field modulation overwrite using digital amplitude modulation. The magneto-optical overwrite method is characterized by: (3) In the magneto-optical overwrite method according to claim 1, the bias magnetic field applying magnetic circuit system is capable of superimposing a DC bias magnetic field onto the medium surface on the digital amplitude modulated high frequency magnetic field generated from the magnetic field modulation coil system. A magneto-optical overwrite method characterized by the following configuration.