JPH04370551A - Data recording and reproducing system for magneto-optical disk - Google Patents

Abstract

PURPOSE:To reduce the error of A/D-converted data by keeping the reference level of the reproduced RF signal of a magneto-optical disk constant. CONSTITUTION:At the time of recording the data to the bulk-erased magneto- optical disk 1, a reference recording area in which the definite data is recorded is provided in the recording area of the data, and simultaneously, the reproduced RF signal of this magneto-optical disk is supplied to a clamp circuit 11 to be clamped by reference voltage sampled in the above-mentioned reference recording area, and is converted into the signal of a definite reference level, and is supplied to an A/D converter 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording and reproducing method for a magneto-optical disk which is useful for recording and reproducing data on a magneto-optical disk whose recording surface is a recording medium sensitive to light.

0002

2. Description of the Related Art Optical disk devices capable of recording various data on an optical disk by irradiating a spiral track with a laser beam and reading out the recorded data include:
Two known methods are known: a continuous method in which tracks on which data is arranged are formed by pregrooves, and a sample servo method in which tracks on which data is arranged are formed by sample servo pits arranged discretely.

FIG. 4 shows an example of the format of a magneto-optical disk in which the recording track is formed by sample servo pits, and S1 to S42 indicate sectors divided into 42 in the circumferential direction, for example. . Each sector track has an address test area AD consisting of a header 1 in which address data is recorded and a header 2 as a trial writing area, as shown in FIG. 5(a), and the following 18-byte data. Segment SG1 with area 32
It is possible to record by dividing into SG32. FIG. 5(b) shows a further enlargement of each segment in the data recording area, in which a 2-byte servo byte SB is placed first, followed by a 16-byte data byte DB provided by a pregroove. There is.

[0004] The servo tool SB includes at least a pair of wobbling pits P1 and P2 that are deviated from the center of the track T toward the outer circumference and the inner circumference, and a clock pit that is arranged on the center line of the track T. P3 is formed in advance by embossing or the like. Also, wobbling pits P1, P2 and clock pit P
3 is a mirror surface M, and a focus servo signal is detected by the laser beam reflected from this mirror surface M, and the laser power can also be controlled.

[0005] Such a magneto-optical disk usually has wobbling pits P1 and P2 as sample points t1 and t.
A tracking error signal is formed by calculating the reflected light detected by clock pit P3.
A clock signal is formed by the signal detected at sample point t3.

In this magneto-optical disk, when a laser beam is irradiated onto the recording surface of the magneto-optical disk along the track and a magnetic field is applied from the other side of the magneto-optical disk, the recording surface reaches the Curie point or higher. When it is magnetized in the direction of the applied magnetic field, data is recorded. or,
When reading information from a magneto-optical disk on which data is recorded, the recorded data is read out as a reproduced RF signal by detecting the reflected light of the laser beam using the magnetic force effect.

[0007]The read reproduction RF signal is waveform-shaped and then binarized, and recorded data is read out. When detecting recorded data from the reproduced RF signal read from the magneto-optical disk, the level of the reproduced RF signal is digitized as it is by an A/D converter, and various clock signals are generated in the digital signal state. At the same time, if you extract recorded data, etc.
Signal processing becomes easier.

[0008]

[Problems to be Solved by the Invention] By the way, the level of the reproduced RF signal of the above-mentioned magneto-optical disk fluctuates due to various factors when the material of the recording layer and the reflectance of the disk are different. , the reproduced RF signal may deviate significantly from the dynamic range of the AD converter. In particular, in order to increase the density of recorded data, for example, N
When encoded using the RZi method, a DC component is superimposed on the reproduced RF signal.

[0009] When this DC component fluctuates, the regeneration R
The DC offset component of the F signal differs for each disc, and even if the gain of the reproduced RF signal is determined, a digital signal that effectively utilizes the dynamic range of the AD converter cannot be obtained. Therefore, the present applicant first records data for 2 to 3 clocks indicating a specific level in a part of the data recording area, and uses this part as a reference recording area to generate a reproduced RF signal obtained from this reference recording area during reproduction. We have proposed a data recording and reproducing method for optical discs in which the sampled signal is used as a clamp voltage to clamp the data reproduced from the data recording area.

However, in the above recording/reproducing method, since no reference recording area is formed in a sector in which no data is recorded in the data recording area, even if a reference recording area is detected in the sector following this sector, the data is not recorded immediately. There was a problem in that a clamping voltage could not be obtained in this sector, and a proper clamping action could not be performed in this sector. Therefore,
It is possible to shorten the time constant of the clamp circuit so that when the reference recording area is encountered, the playback level at that point can be detected immediately, but in this case, if there is a defective part in the reference recording area, unexpected problems may occur. The clamp level will be detected, causing a problem that the read data will be greatly erroneous.

[0011]

[Means for Solving the Problems] In order to solve these problems, the present invention applies a strong magnetic field to a magneto-optical disk used for recording and reproduction, so that the recording surface of the disk is oriented in a specific direction at room temperature. Make it magnetized. Then, a specific position on the recording surface of the bulk-erased magneto-optical disk is set as a reference recording area, and during reproduction, the level when sampling this reference recording area is extracted, and the reproduced RF signal is clamped at this level. That's what I do.

0012

[Operation] Since the recording surface of the magneto-optical disk is erased in a specific direction by bulk erase, the clamp level of the reproduced RF signal is set using the data recording area, for example, the beginning of the data byte DB as a reference recording area. be able to. Furthermore, when data is recorded, control is performed so that constant data is always recorded in this reference recording area, so that a clamp voltage indicating a reference level can be obtained for each segment during reproduction. Therefore,
The time constant of the clamp circuit can be made longer, eliminating the influence of defects caused by scratches on the track, and the output of the AD converter installed in the subsequent circuit can be converted into digital data that makes effective use of the dynamic range. It is possible to reduce error data when extracting reproduced data.

[0013]

[Embodiment] Fig. 1 shows a schematic diagram of a recording/reproducing circuit to which the magneto-optical disk recording/reproducing method of the present invention is applied, and 1 is a magneto-optical disk having the above-mentioned track format. The magneto-optical disk 1 is rotated by a spindle motor 2 at a constant linear velocity (CLV) or a constant angular velocity (CAV). An optical head 3 that irradiates laser light during recording or reproduction is arranged below the magneto-optical disk 1.

As is well known, the optical head 3 is composed of an optical system consisting of a laser light source, a collimator lens, a beam splitter, a two-axis device that controls an objective lens, etc. It is equipped with a polarizing beam splitter and a detector to detect. In particular, the reflected light is split into a P-polarized component and an S-polarized component by the polarizing beam splitter 3C, and detected by the two detectors 3A and 3B.

Then, the outputs of the detectors 3A and 3B are supplied to a differential amplifier 4, and the differential amplifier 4 takes the difference between the two outputs, thereby generating an RF signal for reproducing the data recorded magneto-optically.
Extract the signal. The detector 3A is, for example, a light-receiving element having a split surface, and the push-pull signal is extracted by the detection circuit 5 to form various servo signals, which are supplied to the servo circuit 6 to drive the two-axis device. and performs tracking servo and focus servo, detects the sum signal of the detector 3A, and supplies it to the control data reproducing circuit 7 to form a master clock signal etc.
This clock signal is output to the system control section 8.

Reference numeral 10 indicates a signal processing circuit for the reproduced RF signal demodulated by the differential amplifier 4, and includes an AGC circuit for making the amplitude constant. Further, as described later, 11 is a clamp circuit for the reproduced RF signal read from the magneto-optical disk 1, and the DC fluctuation component superimposed on the reproduced RF signal by the clamp pulse supplied to this clamp circuit 11. is removed so that, for example, the "0" level becomes a constant voltage. The output of this clamp circuit 11 is then supplied to an A/D converter 12 and converted into a digital signal. Note that the signal processing circuit 10 may be provided after the clamp circuit 11.

The output of the A/D converter 12 is supplied to a data detecting section 13 composed of a digital circuit, and this data detecting section 13 performs code conversion, extraction of recorded data by a differential method, read clock, etc. Playback etc. are performed. On the other hand, for the magneto-optical disk 1, the optical head 3
A magnetic head section 20 is provided at a position opposite to that, and a magnetic field that is reversed depending on recorded data is applied. That is, the recording data supplied from the terminal 21 is subjected to predetermined code modulation and blocking in the recording data processing section 22, and furthermore, an error correction code etc. is added, and the data is supplied to the magnetic head 20 as recording data. .

By the way, in the data recording and reproducing method of the magneto-optical disk of the present invention, first, a strong magnetic field is applied to the magneto-optical disk to be used, and the entire disk is magnetized in a specific direction. Bulk erase is performed to maintain the magnetized state, and when recording data on this magneto-optical disk, the recorded data processing section 22
During signal processing, for example, a "0" level signal is supplied from the reference data section 23, and two clocks worth of "0" bit data is added to the beginning of the data recorded in the data byte DB in each segment. It is made to be done. Note that, in practice, the reference data section 23 is included in the recording data processing section 22.

In this way, since the magneto-optical disk is magnetized in a specific direction by a strong magnetic field before data is recorded, the reproduction R before data is recorded is
The F signal is transmitted to each data recording area DB(A), DB(B), DB( as shown in SRF(0) in Figure 2).
A signal at a constant level (zero level) is obtained in C). Furthermore, when data is recorded in a data recording area, for example DB(A), the leading 2-clock portion of the data byte DB area is recorded so that the recording layer becomes "0",
As shown in FIG. 2(b), this part is the reference recording area A.
R2, and the recording data is subsequently recorded.

Therefore, in the magneto-optical disk used in the present invention, the leading portion of the data recording area always shows the 0 level regardless of whether data is recorded thereon or not. therefore,
This reference recording area AR1 as shown in FIG.
, AR2, AR3, . . . are extracted by the sample pulse P(E) formed based on the read clock, a clamp voltage Ec indicating the 0 level of the reproduced RF signal is obtained. In addition, since this clamp voltage Ec shows a substantially constant value for each segment, the time constant of the clamp circuit can be increased, for example, as shown in the data recording area DB (3) in FIG. To,
Even when a defect Sd is encountered, there is an advantage that the clamp voltage Ec does not change significantly due to the defect Sd.

The clamp circuit 11 in FIG. 1 clamps the reproduced RF signal using the clamp voltage Ec and converts it into a signal having a constant bottom value.
Send to 2. Therefore, by configuring the bottom value of the A/D converter 12 and the bottom value of the signal output from the clamp circuit 11 to almost match, the digital signal output from the A/D converter 12 is Since it is within the effective range of the A/D converter 12 and makes full use of this effective range, the accuracy of analog-to-digital conversion is increased, and data extraction in the subsequent data detection section is made easier. This is done accurately and reduces the occurrence of erroneous data.

FIG. 3 shows an embodiment of the clamp circuit 10, where B1 and B2 are buffer amplifiers, SS is a sample switch, C is a hold capacitor, and C1 is a comparator. The sample switch SS is supplied with a sample pulse P(E) for extracting the signals of the reference recording area, and is controlled to be turned on only during the period of this sample pulse. Then, the clamp voltage EC extracted with an appropriate time constant during this period
By adding to the comparator C1, the regenerated RF
The bottom value of the signal is set to a constant reference level. Note that the sampling time constant is 10 channels' worth of clock cycles as TX (667 nS), and 1/10 of the rotational fluctuation cycle of the disk as TY (2.48 mS), and the time constant of the clamp circuit is 14.7 μs ~ It is preferable to set it to 667 ns.

Note that in this embodiment, two clocks worth of "0" data are recorded in the reference recording area.
Three clocks worth of "0" data may be recorded. Furthermore, depending on the polarity of the bulk erase of the disk, it is also possible to record "1" level data in the reference recording area and clamp this portion so that the peak level of the reproduced RF signal becomes constant. Furthermore, by adjusting the timing of the sample pulse P(E), the reference recording area AR can be set to the middle part of the data byte DB,
Alternatively, it can also be provided at the rearmost end. Furthermore, as a bulk erase, any data may be recorded in the data recording area of the disk in the actual recording state.

[0024]

As explained above, the method for recording and reproducing data on a magneto-optical disk of the present invention applies a strong magnetic field to the magneto-optical disk in advance when using the magneto-optical disk. is magnetized in a specific direction, and at the time of recording, a reference recording area is also provided at a predetermined position within the recording data area to record several bits of data indicating "1" or "0". By clamping the reproduced signal with the clamp voltage extracted from the reference recording area, a uniform reproduced RF signal can be obtained over the inner and outer circumferential sides of the disc, and digital conversion of the reproduced RF signal containing DC components is effective. It has the advantage of being accurate and accurate.

Furthermore, since a DC-free circuit (AC amplifier) can be used in the reproduction system, the effects of optical system offset and circuit system offset can be reduced, making system design easier. Furthermore, in a magneto-optical disk that is completed in units of sectors, DC fluctuations tend to occur in units of sectors during reproduction, but by adopting the method of the present invention, such drawbacks can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a circuit to which a magneto-optical disk data recording/reproducing method of the present invention is applied.

FIG. 2 is a signal waveform diagram of a reproduced RF signal and a sample pulse.

FIG. 3 is a circuit diagram showing an example of a clamp circuit.

FIG. 4 is an explanatory diagram showing the format of a magneto-optical disk.

FIG. 5 is a detailed explanatory diagram of recording tracks.

[Explanation of symbols]

1 Magneto-optical disk 2 Spindle motor 3 Optical head 4 Differential amplifier 11 Clamp circuit 12 A/D converter 20 Magnetic head

Claims (2)

[Claims] 1. An address area in which a track formed concentrically or spirally on a magneto-optical disk is divided into predetermined sector areas, and an address area is formed in each divided sector; In a data recording/reproducing device for a magneto-optical disk in which a divided data recording area is formed following an address area, after bulk erasing the magneto-optical disk, each of the divided data recording areas is recorded in the data recording area. A reference recording area is formed at a predetermined position in the area to record several consecutive bits of data indicating the bulk erased level, and the level of the reproduced RF signal obtained from the reference recording area during reproduction is used as a clamp voltage to record the data. A data recording and reproducing method for a magneto-optical disk, characterized in that a reproduced RF signal reproduced from a region is clamped. 2. The data recording and reproducing method for a magneto-optical disk according to claim 1, wherein the reference recording area is provided at the beginning of each block of the data recording area.