JPH031346A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To prevent an error from being caused at the time of reproducing data and to accomplish high-density recording by projecting a 2nd light beam for recording data whose phase is different from a 1st light beam by 180 deg. in a period when a recording signal exists. CONSTITUTION:Magnetic field generation means 7, 7a and 22 give the alternat ing field of single frequency to a magneto-optical disk 1. A single light beam projection means 20 projects the 1st light beam in pulse state in synchronism with the alternating field given to the magneto-optical disk 1 in a specified cycle and projects the 2nd light beam in pulse state only in the period when the data is recorded in a cycle in which the phase is different from the 1st light beam by 180 deg., then gives the respective light beams to the magneto-optical disk. Therefore, a magnetizing area in which the intensity of magnetic field is vague is not generated between a data recording area and a data erasing area. Thus, the error is prevented from being caused by the magnetizing area (noise-up area) in which the intensity of magnetic field is vague at the time of reproducing and the high-density recording of the data is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording device, and more specifically, it proposes a magneto-optical recording device that can override (overwrite) a magneto-optical disk.

[Conventional technology]

When recording data on a magneto-optical disk, a laser beam is projected onto the data recording position of the perpendicularly magnetized film, and a magnetic field related to the data is applied. When the temperature of the perpendicularly magnetized film at the position where the laser beam is projected rises and reaches above the Curie point, the perpendicularly magnetized film is magnetized in the direction of the applied magnetic field, and data is recorded on the magneto-optical disk. be done.

FIG. 3 is a block diagram showing the main parts of a conventional magneto-optical recording device that allows data to be rewritten by overriding with respect to such a magneto-optical recording method.

The magneto-optical disk 1 is constructed by coating a perpendicularly magnetized film 3 on a transparent substrate 2, and the magneto-optical disk 1 rotates around a central axis 0.

An optical head section 4 including a semiconductor laser 5 and a lens 6 is disposed on one side of the magneto-optical disk 1 . Laser beams 1 and B emitted by this semiconductor laser 5 are projected onto the perpendicularly magnetized film 3 through a lens 6.

Further, the optical head section 4 can move in the radial direction of the magneto-optical disk l while maintaining a predetermined distance from the magneto-optical disk l.

An electromagnet 7 is provided on the other side of the magneto-optical disk 1 for applying a magnetic field.
It faces the optical head section 4 via a. Further, this electromagnet 7 can be moved in conjunction with the optical head section 4.

Furthermore, a magnetic field modulation circuit 8 is provided for magnetic field modulation,
Its input side is connected to the recording signal input terminal 9, and its output side is connected to the coil 7a of the electromagnet 7.

Next, the operation of this magneto-optical recording device will be explained with reference to FIG. 4 showing the waveforms and recording patterns of various signals.

When a recording signal as shown in FIG. 4(A) is input to the magnetic field modulation circuit 8, the electromagnet 7 generates a magnetic field as shown in FIG. 4(B) to direct the perpendicular magnetic film 3 of the magneto-optical disk l. give.

In this case, the perpendicularly magnetized film 3 is irradiated with the laser beam LB whose light intensity is constant to raise the temperature of the perpendicularly magnetized film 3 to the Curie point or higher, as shown in FIG. 4(C). The recording tracks of the perpendicular magnetization film 3 of the disk l are shown in FIG.
) Recording patterns IOA, IOB...I as shown in
An OE will be formed. Note that the (+) and (-) signs in the recording pattern represent upward and downward magnetization, respectively.

In this way, the magneto-optical recording device described above continuously heats a minute portion on the perpendicular magnetization film 3 of the magneto-optical disk 1 to a temperature higher than the Curie point using the laser beam LB, and moves this heated minute portion to reach the Curie point. When the temperature is near the 20 Curie point, the area near the 20 Curie point is magnetized in the direction of the magnetic field modulated according to the recording signal. Then, when the temperature drops, the magnetization is maintained and data is recorded in units of a range smaller than the range of the heated minute part. In this way, even if data is already recorded on the magneto-optical disk 1, new data can be recorded by overwriting.

[Problem to be solved by the invention]

The conventional magneto-optical recording device described above projects a laser beam LB with a constant optical intensity onto a magneto-optical disk 1, and applies a modulated magnetic field according to a recording signal to the projection position, thereby recording data on the magneto-optical disk l. override. Then, the magnetic field applied to the magneto-optical disk l changes from the maximum negative value -H (or maximum positive value +H) to the maximum positive value +H (or maximum negative value -H), as shown in FIG. 4(B). It takes a magnetic field reversal time t1 for the change to occur. Therefore, the magnetic field strength gradually increases (or decreases) during the magnetic field reversal time t.

As shown in FIG. 4(D), in the perpendicular magnetization film 3, before and after each pattern forming the recording patterns IOA, IOB, . , 11B...IIF, which may cause an error during data reproduction. Furthermore, since there is a magnetic field reversal time t1, the reversal period cannot be increased, and high-density recording cannot be performed.

In view of this problem, the present invention eliminates errors during reproduction due to magnetized regions (noise-up regions) where the magnetic field strength is ambiguous.
The purpose of the present invention is to provide a magneto-optical recording device that can record data at high density.

[Means to solve the problem]

The magneto-optical recording device according to the present invention applies an alternating magnetic field of a single frequency to a magneto-optical disk, and emits pulsed first light at a predetermined period in synchronization with the alternating magnetic field by a single light beam emitting means. The beam is emitted at a period of 180 degrees different in phase from the first light beam only during the time to record data. A pulsed second light beam is projected onto the magneto-optical disk.

[Effect]

The magnetic field generating means applies an alternating magnetic field of a single frequency to the magneto-optical disk. The single light beam emitting means emits a pulsed first light beam at a predetermined period in synchronization with the alternating magnetic field applied to the magneto-optical disk, and the phase is 180 degrees with respect to the first light beam. Pulsed second light beams are emitted at four different periods only during the data recording time and are applied to the magneto-optical disk.

As a result, a magnetized region with ambiguous magnetic field strength does not occur between the data recording area and the data erasing area.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to drawings showing embodiments thereof.

FIG. 1 is a block diagram showing the main parts of a magneto-optical recording device according to the present invention. A semiconductor laser 20 is provided on one side of the magneto-optical disk 1, and the laser beam LB emitted by the semiconductor laser 20 is
is projected onto the magneto-optical disk l through a lens 21, and a focused point is obtained on the perpendicular magnetization film 3 of the magneto-optical disk l. An electromagnet 7 is disposed on the other side of the magneto-optical disk 1 so as to face the projection position of the laser beam LB projected onto the magneto-optical disk 1. Coil 7 of this electromagnet 7
a is connected to the output side of the electromagnet drive circuit 22.

Clock CK input to clock input terminal 23.

is input to the waveform shaping circuit 24. The waveform shaping circuit 24 generates a clock CK with a duty ratio of 50% based on the clock cKo, and the clock CK is input to the differentiating circuit 25 and the oscillating circuit 26. The oscillation circuit 26 oscillates at a single frequency in synchronization with the input clock, obtains a sine wave signal SS by the oscillation, and inputs the sine wave signal SS to the electromagnet drive circuit 22. The differentiating circuit 25 generates trigger pulses at the rising and falling edges of the manually inputted clock CK. The trigger pulse TP generated at the rising edge of the clock is input to the adder circuit 26, and the trigger pulse TP generated at the falling edge of the clock is input to the adder circuit 26.
, are input to a gate circuit 27 to which the recording signal SR is given as a gate signal. The output of the gate circuit 27 is input to the adder circuit 26 . The output of the adding circuit 26 is inputted to the optical modulating circuit 28, and the optical modulating circuit 28 is connected to the adding circuit 26.
A pulse P having an extremely narrow pulse width is outputted in relation to the output from the semiconductor laser 20 . The output of the electromagnet drive circuit 22 is the coil 7 of the electromagnet 7.
given to a.

Next, the operation of the magneto-optical recording apparatus constructed as described above will be explained with reference to FIG. 2 showing waveforms and recording patterns of each part thereof.

When the clock CK is input to the clock input terminal 23, the waveform shaping circuit 24 outputs the clock CK as shown in FIG. 2(E).
Output. The oscillation circuit 26 oscillates in synchronization with the clock CK by the clock GK, and when the sine wave signal SS is input to the electromagnet drive circuit 22, the electromagnet 7 is excited by the electromagnet drive circuit 22, and the electromagnet 7 is moved to the magneto-optical disk.
An alternating magnetic field H shown in FIG. 2(B) is applied to the magnetic field.

On the other hand, when the clock CK is input to the differentiating circuit 25, the trigger pulse TP output in synchronization with the rising edge of the clock CK, that is, the negative maximum value -H of the alternating magnetic field H, is transmitted through the adding circuit 26 to the trigger pulse TP. The signal is input to the modulation circuit 28. Thereby, the optical modulation circuit 28 applies a predetermined pulse P to the semiconductor laser 20, and the semiconductor laser 20 emits the pulsed first laser beam LB shown in FIG. 2(C) and projects it onto the magneto-optical disk 1. It turns out.

When the temperature of the magneto-optical disk reaches the Curie point due to the projected laser beam LB, an alternating magnetic field [1 is the maximum negative value =
When the signal becomes H, the recorded data is definitely erased. and the second
A data erasing area (-) shown by a solid circle in FIG. 5(F) is continuously formed.

Here, when the recording signal S is applied to the gate circuit 27, the gate circuit 27 opens the gate while the recording signal SII is applied. Therefore, the differentiating circuit 25 detects the falling edge of the clock CK, that is, the positive maximum value of the alternating magnetic field H+H.
The trigger pulse TP output in synchronization with the adder circuit 26
is input to. Thereby, the adder circuit 26 inputs the trigger pulse TP together with the input trigger pulse TPu to the optical modulation circuit 28. Then, the semiconductor laser 2o is activated as shown in FIG. 2 (D
) is emitted as a pulsed second laser beam LB. When the temperature of the magneto-optical disk reaches the Curie point due to the emitted laser beam LB, the alternating magnetic field H during the period when the recording signal S is input has a positive maximum value +H, and data is reliably recorded. . Then, a data recording area (±) shown by a broken line circle in FIG. 2(F) is formed. However, as the alternating magnetic field I4 subsequently reaches the negative maximum value F1, part of the data recording area (+) changes to a data erasing area (-), and the data recording area (+) is formed in a crescent shape. Ru. When the recording signal Sll shown in FIG. 2(A) is manually generated, the recording pattern corresponding to the recording signal becomes as shown in FIG. 2(F). Note that during the period when three recording signals are not present (L level period), the gate circuit 27 does not open the gate, so the trigger pulse TP is generated.

is not input to the adder circuit 26, and therefore the semiconductor laser 2
0 does not emit the laser beam LB at the positive maximum value +H of the alternating magnetic field 11, as shown in FIG. 2(D). As a result, data erasing areas (-) are continuously formed. Note that when the magneto-optical recording medium is initialized to the erased state, the data erased area (-) shown as a circle in FIG. ,
As shown in FIG. 2(1), only a crescent-shaped data recording area is formed.

In this way, when the alternating magnetic field applied to the magneto-optical disk l reaches the negative maximum value -H, the semiconductor laser 20 emits the pulsed laser beam LB to erase the recorded data, while the recorded signals S, l During the period when is being input, the semiconductor laser 20 emits pulsed laser light to record data when the alternating magnetic field reaches its maximum positive value +H, so the maximum value of the alternating magnetic field is used to erase or erase data. It will be recorded. Therefore, the recording pattern does not have a noise-up area where the magnetic field strength is ambiguous as shown in FIG. 2(F), and the data erasing area (-) and the data recording area (G) are clearly distinguished.

Therefore, when data recorded in this way is reproduced, the analog reproduction signal has a virtual pulse waveform as shown in Figure 2 (G), but in reality, the size of the optical spot is finite. Therefore, if the analog signal is reproduced, a mountain shape with no resolution will be obtained as shown by the curve X according to the virtual pulse waveform. Therefore, if the reproduced analog signal is binarized using a predetermined threshold value, the final reproduced signal is obtained as shown in FIG. 2 (11), and the adjacent data recording areas (+), (+ Even if there is a data erasing area (-) between ), it is possible to accurately obtain a reproduced signal without being affected by the data erasing area (-).

When data is reproduced in this manner, no error occurs because the level of the reproduced signal changes instantaneously in correspondence to the data erasing area (-) and the data recording area (+).

Furthermore, even when the recording signal SR is input, the semiconductor laser 20 emits the laser beam LB for erasing data at the negative maximum value of the alternating magnetic field H. There is no need to control to stop the emission of. Therefore, the control circuit for the semiconductor laser 20 can be simplified.

Note that if the oscillation frequency of the oscillation circuit 26 is increased, the result shown in FIG.
The interval between the data recording area (+) and the data erasing area (-) of the recording pattern shown in F) can be shortened.

In addition, if the point at which the alternating magnetic field 1 reaches its maximum value is slightly delayed from the point at which the laser beam is emitted, the maximum value of the alternating magnetic field H can be obtained when the temperature of the magneto-optical disk reaches the Curie point. This allows data to be recorded and erased more reliably.

Note that if the frequency of the clock CK is set higher than the frequency of the recording signal SR, the number of crescent-shaped data recording areas corresponding to each recording signal shown in FIG. The density of the data recording area corresponding to the recorded signal can be further increased, and the reproduction accuracy of the reproduced signal can be further improved.

In this embodiment, a magneto-optical recording device has been described, but it is of course applicable to a magneto-optical recording/reproducing device as well.

Furthermore, the light projected onto the magneto-optical disk is not limited to laser light. Furthermore, although the description has been made to record data at the maximum positive value of the alternating magnetic field, it is also possible to record data at the maximum negative value.

〔Effect of the invention〕

As described in detail above, the present invention includes a magnetic field applying means that applies an alternating magnetic field of a single frequency to a magneto-optical disk, and a first light beam for erasing data that is periodically emitted in synchronization with the magnetic field to record data. Since a single light beam emitting means is provided for emitting a second light beam for data recording whose phase is 180 degrees different from that of the first light beam during a period when a signal exists, it is difficult to erase or record data. Erasing data at the maximum value of the alternating magnetic field'
, recording is possible, and no noise-up areas with ambiguous magnetic field strength occur in the recording pattern.

Furthermore, since the data is erased by the first light beam emitted at a constant period, no data remains. Therefore, according to the present invention, no errors occur during data reproduction, and high-density recording of data is possible. It is possible to provide an excellent magneto-optical recording device. Further, since the magnetic field applied to the magneto-optical disk may be an alternating magnetic field with a single frequency, excellent effects such as the ability to configure the electromagnet drive circuit with a simple circuit can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the main parts of the magneto-optical recording device according to the present invention, Fig. 2 is an explanatory diagram showing the waveforms and recording patterns of each part, and Fig. 3 shows the main parts of the conventional magneto-optical recording device. The block diagram shown in FIG. 4 is an explanatory diagram of waveforms and recording patterns of each part. ■... Optical disk 7... Electromagnet 20... Semiconductor laser 24... Waveform shaping circuit 25... Differential circuit 26... Oscillation circuit 27... Gate circuit 28
. . . Light modulation circuit In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A magneto-optical recording device that records data on a magneto-optical disk, comprising a magnetic field generating means that generates an alternating magnetic field of a single frequency, and a first pulsed light beam that emits a pulsed first light beam at a predetermined period in synchronization with the alternating magnetic field. and a single light beam emitting means that emits a pulsed second light beam at a period 180 degrees different in phase from the first light beam only during data recording time. Magneto-optical recording device.