JPH04121801A - Magnetic field modulation system for magneto-optical recorder - Google Patents

Abstract

PURPOSE:To secure normal operation of the driving circuit of a magnetic field modulation coil by controlling opening/closing of the switching element of a magnetic field application means by correction data in the sampling servo area of a magneto-optical disk. CONSTITUTION:Each segment of the recording track of the magneto-optical disk is set as a data area (AD) and a sampling servo area (SD), and a magnetic field inverted from the magnetic field modulation coil by recording data is applied to the magneto-optical disk in the period of the area (AD), and every kind of servo signal is generated by reproducing a sampling servo pit in the area (SD), and a switch 14 is switched in that period, and the correction data from a generating means 18 is supplied to the driving circuit 13. Therefore, the inversion magnetic field of the magnetic field modulation coil driven by the driving circuit 13 is controlled so that the mean time of logic values '1' and '0' can be equalized as possible through one segment period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording device that is capable of recording data by applying a magnetic field to the recording surface of an optical disk that is irradiated with a laser beam, for example. The present invention relates to a magnetic field modulation method.

"Summary of the Invention" The magnetic field modulation method of the magneto-optical recording device of the present invention includes a magneto-optical disk having a recording surface on which data can be recorded in response to at least light, and a laser beam applied to the magneto-optical disk. In a magneto-optical recording device, the magneto-optical recording device is equipped with an optical head that irradiates the magneto-optical disk, and a magnetic field applying means that applies a magnetic field modulated by a current flowing through a pair of switching elements that are opened and closed according to recorded data to the magneto-optical disk. means for detecting the occurrence rate of logical values "1" and "0" of recording data supplied to the recording area of the disk;
A correction data generating means is provided for generating correction data such that the generation rate is averaged as much as possible, and in a sample servo area (read-only area) of the magneto-optical disk, a switching element of the magnetic field applying means is controlled to open and close according to the correction data. to be done. Furthermore, even when a DC-free type device driven by a single power supply is used as the magnetic field applying means, data can be recorded accurately.

[Conventional technology]

Conventional examples of recording data on magneto-optical materials include, for example, magnetizing a magneto-optical disk in a specific direction prior to recording.
Next, during recording, this magneto-optical disk is exposed to a magnetic field in the opposite direction to the previously applied magnetic field, and a laser beam intermittent with data is irradiated to locally heat the disk to a temperature close to the Curie point, which modulates the disk. A magnetic pattern having a magnetization direction corresponding to the pattern is generated.

By the way, the above-mentioned recording method has a problem in that when new data is to be recorded on an area that has already been recorded, it is necessary to erase the data before recording, and so-called override cannot be performed.

Therefore, a magneto-optical recording device using a magnetic field modulation method has been developed, which records data while modulating the magnetic field of a recording portion irradiated with a laser beam according to recording data.

Magneto-optical recording devices using this magnetic field modulation method can record new data at any location without erasing data;
In order to perform modulation that inverts at a sufficiently high speed based on the recorded data, a drive circuit that intermittents a large current at a high speed is required.

FIG. 5 shows an example of such a conventional drive circuit, in which L, .Lt are magnetic field modulation coils wound in opposite directions, and S, , S2 are switching elements such as transistors.

This drive circuit includes switching elements S,,S.

By driving the magnetic field modulation coils L, , L connected to a single power supply element B so that they are turned on alternately based on recorded data, a magnetic field in the positive direction (N) and a magnetic field in the opposite direction are generated. (S) can be generated.

However, two magnetic field modulation coils L, , L are required to apply the magnetic field, resulting in poor efficiency and problems in that access speed is reduced due to the weight of the magnetic head.

Therefore, a drive circuit has been proposed in which a single magnetic field modulation coil is used to apply magnetic fields in the forward and reverse directions. (Japanese Unexamined Patent Publication No. 1-130302) The principle diagram of this drive circuit is as shown in Figure 6, where two circuits are connected in series.
one switching element S, , S, and a diode I)+,
A coupling capacitor C and a magnetic field modulation coil L are connected in series at an intermediate point A.

Problems to be Solved by the Invention In this drive circuit, first the switching element Sl is closed and the switching element S2 is opened, so that a current ir flows as shown by the arrow, and then the switching element Sl is opened,
When the switching element S2 is closed, a current 1r flows in the direction of the arrow, so that a magnetic field with reversed polarity is generated in the magnetic field modulation coil.

Moreover, in this drive circuit, the diodes D1 and D are turned off by the kick pack voltage of the magnetic field coil L at the moment when the switching elements S, , S are alternately reversed.
The resonance current formed by the magnetic field modulation coil and its stray capacitance C0 has the advantage of sharpening the rise of the reversal magnetic field.

However, since the magnetic field modulation coil is formed so that current flows in and out through the coupling capacitor C, the data recorded on the magneto-optical disk is
There is no problem when the average time of the signal's logical value "l" is equal to the average time of the logical value "0" (hereinafter referred to as DC free data), but when it comes to normal video data or other data modulation formats, the average time of the logical value ``1'' and the logical value ``O'' of the recorded data may not be equal, and when this data is not DC free data, the coupling capacitor C The terminal voltage may be biased and insufficient current may not be able to flow through the magnetic field modulation coil.

For example, if the time during which the logical value is "l" is much longer than the time when the logical value is "0", then the logical value "l"
There is a problem in that the strength of the magnetic field for recording " is reduced, and the resolution of recorded data is significantly reduced.

One way to solve the above problem is to connect the negative power supply (-B) without using the switching element S2 as a grounding point and remove the capacitor C, but in this case, a two-power circuit system This leads to an increase in costs,
Furthermore, since it is necessary to change the polarity or level of the control voltages of the switching element S1 and the switching element S2, there is a drawback that the logic signal output from the digital IC circuit cannot be directly supplied as a control signal.

Means for Solving Problem 1 The present invention has been made to solve this problem. ”), and correction data generation means for generating correction data such that the logical value of the recorded data is averaged by the output of the detection means, and furthermore, from this correction data generation means. The apparatus is provided with means for supplying output data to a magnetic field modulation coil within a sample servo area period of a magneto-optical disk.

[Function] The magneto-optical recording device of the present invention is equipped with the above-described means, so that the average logical value of the recorded data can be calculated using the period during which the optical head passes through the sample servo area, which is normally used as the reproduction mode. We are trying to ensure that the
It becomes possible to ensure normal operation of the drive circuit that drives the magnetic field modulation coil, except for extreme recording data such as recording data that includes a large direct current component.

[Embodiment] FIG. 1 shows an embodiment of the magnetic field modulation method of the magneto-optical recording device of the present invention, in which the magneto-optical disk 10 is connected to the optical device 1.
1 and magnetic field modulation data supplied to the magnetic head 12.

The magnetic field modulation coil constituting the magnetic head 12 is driven by the aforementioned drive circuit 13 (FIG. 6), and recording data supplied from the outside via a switch 14 is input to this drive circuit 13.

15 modulates the recording data in a predetermined modulation format, and
This is a recording data processing unit 15 that adds codes and blocks data.

On the other hand, various servo signals are formed in the RF signal processing unit 16 of the low RF signal reproduced by the optical device 11, and the position of the objective lens of the optical device 11 and the spindle motor M
The rotation of the data is controlled, and the data is supplied to the reproduction data processing section 17 and the correction data generation means 18.

Note that 19 indicates a control section that outputs control signals for the entire magneto-optical recording apparatus.

For example, as shown in FIG. 2, the correction data generating means 18 includes a counter 21 that adds or subtracts a clock signal according to the logical value "l" 0 of the reproduced data, and
The conversion table 23 includes a latch circuit 22 that latches the count value of the latch circuit 22, and a conversion table 23 that reads out the correction data stored based on the count value of the latch circuit 22.

For example, as shown in FIG. 3, the output of the conversion table 23 is a pulse train having a duty of approximately 50% near the count value ±O where the number of regenerated RF low signal logic values "1" and "0" is approximately equal. It is considered a PC.

However, when the time period when the logical value "1" of the reproduced data occurs becomes longer, the count value of the counter 21 increases, and at this time, the pulse train -Pc in which the logical value "0" accounts for a high proportion as the correction data. is read from the conversion table 23.

Furthermore, as the generation time of the logic m'''O'' of the reproduced data becomes longer, the count value of the counter 21 increases to the + side, and at this time, the conversion table 23 shows that the pulse train +Pc that has a high proportion of the logic value "1"' It is designed to be read out.

The correction data output from the conversion table 23 is stored in the sample servo area of the magneto-optical disk when the switch is pressed in the sample servo area of the magneto-optical disk.
4 to the drive circuit 13.

That is, the recording track of a magneto-optical disk is formed by a plurality of segments divided in the circumferential direction as shown in FIG. 4, and each segment has a data area (AD) and servo information recorded therein. This is the sample servo area (SD). Then, the data area (A
During the period Tw of D), a magnetic field that is reversed depending on the recording data is applied to the magneto-optical disk by the magnetic field modulation coil described above. In addition, the sample servo area (SD) is in the reproduction mode, and various servo signals of the magneto-optical recording device are generated by reproducing the sample servo bits, but in the present invention, the switch 14 is switched during this period TR to perform correction. Correction data output from the data generating means 18 is supplied to the drive circuit 13. Therefore, the reversal magnetic field of the magnetic field modulation coil driven by the drive circuit 13 throughout the l segment period is controlled so that the average time of the logical values "l" and "0" is as equal as possible.

If such an operation is performed for each segment while in the data recording mode, as a result, the drive circuit 13
The opening and closing times of each of the switching elements S, , S2 are averaged, and the influence of the coupling capacitor C can be reduced even when recording data that is not DC-free.

Note that the amount of data in the sample servo area (SD) is smaller than that in the data recording area (AD), so it is difficult to correct when the logical level of the recorded data is extremely biased to one side. In the case of free distribution data, the improvement effect can be considerably increased.

[Effects of the Invention] As explained above, the magnetic field modulation method in the magneto-optical recording device of the present invention operates with a single power supply, and at least one pair of switching elements supplies currents in opposite directions to the magnetic field modulation coil. When using a drive circuit, the period of the sample servo area is used to ensure reliable operation even when recording data is considered to be DC-free.

Therefore, a simple push-pull type drive circuit with high switching speed can be used, and the cost of the device can be reduced and the performance improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the magnetic field modulation method in the magneto-optical recording device of the present invention, FIG. 2 is a block diagram showing a specific example of the correction data generating means 18, and FIG. 3 is a block diagram showing a specific example of the correction data generating means 18. FIG. 4 is an explanatory diagram of the recording track of a magneto-optical disk, FIG. 5 is a drive circuit diagram of a conventional magnetic field modulation coil, and FIG. This is a drive circuit for a magnetic field modulation coil that can be adopted.

Claims (1)

[Claims] A magneto-optical disk that has a recording surface that is sensitive to at least light and can record data, an optical head that irradiates the magneto-optical disk with a laser beam, and a current that flows through a switching element that opens and closes depending on the recorded data. a first state of binary data supplied to a recording area of the magneto-optical disk in a recording mode; Alternatively, a detection means for detecting the frequency of occurrence of the second state, and a correction that generates a data string that averages the ratio of the frequency of occurrence of the first state and the second state obtained from the detection means. A magnetic field modulation system for a magneto-optical recording device, characterized in that data generation means is provided, and the switching element is opened and closed during a sample servo area period of the optical disk by the output of the correction data generation means.