JPH05144194A - System for reproducing magneto-optical disk - Google Patents

Abstract

PURPOSE:To prevent the impossibility of data reproduction to the utmost and to improve the reliability of a magneto-optical disk system. CONSTITUTION:When a clamp defect occurs at the time of reproducing operation of a certain target sector with respect to the magneto-optical disk which is initialized such that in an MO area involving an address test area in which a first clamp area is set and a data recording area in which a second clamp area is set, a reproduced signal with the same polarity and the same level is obtained, the reproducing operation is restarted from a sector preceding to the target sector. With respect to the reproduced signal obtained from the first and second clamp areas of the sector preceding thereto, clamp is performed and the reproduced signal from the first clamp area of the target sector is not used for the clamp processing and for the data from the data recording area of the target sector, a reproducing processing is performed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An optical disk device capable of irradiating a spiral track with a laser beam to record various data on an optical disk and reading the recorded data is
Known are a continuous method in which tracks in which data is arranged are formed by pregrooves, and a sample servo method in which tracks in which data are arranged are formed by sample servo pits that are discretely arranged.

FIG. 6 shows an example of a magneto-optical disk format in which a recording track is formed by sample servo pits. S _{1 to} S ₄₂ are, for example, sectors divided into 42 in the circumferential direction. Indicates.

The track of each sector unit is shown in FIG.
The address test area AD is composed of a header segment H ₁ having an area where address data is recorded and an ALPC area (Automatic Laser Power Control Area), and a header segment H ₂ used for a trial writing area, etc. A data recording area DB, which is provided and subsequently records, for example, 20 bytes of data, is divided into ₃₀ segments SG _{1 to} SG ₃₀ .

FIG. 7B shows the header segments H ₁ and H ₁ .
₂ and the data segments SG ₁ to SG ₃₀ and further expanded the first servo byte SB is disposed on the subsequently address or a magneto-optical (MO) data area to be recorded which are provided.

At least one pair of wobbling pits P ₁ and P ₂ which are deviated from the center of the track T to the outer peripheral side and the inner peripheral side are arranged on the servo bite SB and on the center line of the track T. The clock pit P ₃ is previously formed by embossing or the like.

A mirror surface M is formed in the middle of the wobbling pits P ₁ and P ₂ and the clock pit P ₃ , and the focus servo signal is detected by the laser light reflected from the mirror surface M and the laser power control is performed. -Le can also be done. Furthermore, the pits P ₄ and P whose access code as track information forms a gray code
Recorded by ₅ .

In such a magneto-optical disk, a tracking error signal is usually formed by calculating reflected light when the wobbling pits P ₁ and P ₂ are detected at the sample points t ₁ and t ₂ , and the clock pit P is formed. _The clock signal is formed by the signal detecting ₃ at sample point t ₃ .

In this magneto-optical disk, when the recording surface of the magneto-optical disk was irradiated with a laser beam along the track and a magnetic field was applied from the other surface of the magneto-optical disk, the recording surface became the Curie point or higher. Data is recorded by being magnetized in the direction of the applied magnetic field. or,
When reading information from a magneto-optical disk on which data is recorded, the recorded data is read by detecting the reflected light of the laser beam using the magnetic cover effect.

Then, the reproduced signal thus read is subjected to waveform shaping and then binarized to read the recorded data. When detecting recorded data from the reproduction signal read from the magneto-optical disk, the level of the reproduced signal is
If it is digitized by the A / D converter as it is, various clock signals are generated in the state of digital signals, and recording data is extracted, the signal processing becomes easy.

[0011]

By the way, when the reproduction signal of the above-mentioned magneto-optical disk is different in the material of the recording layer, the reflectance of the disk, etc., the level of the reproduction signal fluctuates due to various factors and reproduction The signal may deviate significantly from the dynamic range of the A / D converter. In particular, in order to increase the recording data density, for example, when encoded by the NRZi system, a DC component is superimposed on the reproduced RF signal.

When the DC component fluctuates, the DC offset component of the reproduced signal becomes different for each disc, and even if the gain of the reproduced signal is determined, the dynamic range of the A / D converter is effectively used. No digital signal can be obtained. Therefore, it has been proposed as a prior art to define a predetermined clamp area, extract the reflected light level, and clamp the reproduced signal at this level.

That is, a relatively wide first clamp area is set near the beginning of a sector, for example, in the ALPC area or header segment H ₂ , and a relatively narrow second clamp area is set.
A clamp area is provided at the beginning of each of the data segments SG _{1 to} SG ₃₀ , and the signal obtained when sampling the first clamp area is used as a clamp voltage to clamp the bottom value of the reproduction signal to a constant level. Further, after that, the level of the reproduction signal in the data recording area DB is made constant for each data block by following the clamp level by using the sample signal of the second clamp area as the clamp voltage in a constant cycle, that is, in segment units. It is a thing.

By enabling the clamp processing to be performed in sector units in this way, it is possible to perform sufficient data reproduction processing by laser scanning only the target sector to be reproduced during reproduction. It is especially effective as a disk system for storage.

On the contrary, if the first clamp region of the target sector has some defects or scratches and cannot be clamped sufficiently, the reproduced signal from that sector falls within the dynamic range of the A / D converter. On the other hand, the reproduction signal has an inappropriate level, a large amount of reproduction data read error occurs in the sector, and the data recorded in the data segments SG _{1 to} SG ₃₀ of the target sector cannot be reproduced (error correction is impossible). There is a problem that it may be.

[0016] For example, in a disk system for data storage, it is necessary to avoid such unreproducible data as much as possible. Therefore, it becomes a very big defect that the data cannot be reproduced due to a defective clamp. ..

[0017]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, in which tracks formed concentrically or spirally on a magneto-optical disk are formed in a predetermined number of sector areas. In each of the divided sectors, an address test area and a data recording area divided after the address test area are formed, and the magneto-optical field applied to the address test area and the data recording area is formed. The recording area is provided with a first clamp area in the address test area for the magneto-optical disk which is initialized so that reproduction signals of the same polarity and the same level can be obtained. The second clamp area is provided at the position, and when the reproduction operation is performed for a certain target sector, the reproduction signal obtained from the first and second clamp areas is used. Clamp the reproduction signal of the data recording area by using to perform the reproduction processing of the data recording area.In addition, if a clamp failure occurs during the reproducing operation for the target sector, The reproducing operation is executed again, the reproducing signal is clamped by the reproducing signals obtained from the first and second clamp areas in the preceding sector, and the reproducing signal from the first clamp area in the target sector is clamped. Provided is a reproducing system of a magneto-optical disk, which reproduces data from a data recording area of a target sector in a state where it is not used.

[0018]

[Function] Before using a magneto-optical disk (for example, before shipping)
In addition, a strong magnetic field is applied to the entire magneto-optical disk to forcibly saturate the magnetic medium forming the recording surface. That is, by applying a strong magnetic field (10 KOe) to the magneto-optical disk, the recording layer, which is normally magnetized at the Curie point, is magnetized on the recording surface of the magneto-optical disk even at room temperature, and the bulk erase (Bulk Erase) is maintained. erase) can be performed.

If initialized in this way, even in a sector where data is not magneto-optically recorded, a reproduction signal having the same level and polarity as the clamp area in the data recorded sector can be obtained in the MO area. .. Therefore, even when the clamp level in the preceding sector is applied during the reproduction operation of the target sector, the appropriate clamp processing is executed to some extent and the data reproduction cannot be prevented.

[0020]

1 is a schematic diagram of a recording / reproducing circuit to which a reproducing system of a magneto-optical disk of the present invention is applied.
Reference numeral 1 denotes a magneto-optical disk having the track format as described with reference to FIGS. 6 and 7. The magneto-optical disk 1 is rotationally driven by a spindle motor 2 at a constant angular velocity (CAV), for example. .. In this magneto-optical disk 1, in a stage after manufacturing and before shipment, a strong magnetic field (10 KOe) is applied to the entire magneto-optical disk, and the magnetic medium constituting the recording surface is forcibly saturated and magnetized. Has been processed.

An optical head 3 for irradiating a laser beam at the time of recording or reproducing is arranged below the magneto-optical disk 1.
As is well known, the optical head 3 is composed of an optical system including a laser emission source, a collimator lens, a beam splitter, a biaxial device for controlling an objective lens, and the like, and detects reflected light from a magneto-optical disk. It is equipped with a polarizing beam splitter and a detector. In particular, the reflected light is split into a P-polarized component and an S-polarized component by the polarization beam splitter 3C and detected by the two detectors 3A and 3B.

Then, the outputs of the detectors 3A and 3B are supplied to the differential amplifier 4, and the differential amplifier 4 takes the difference between the two outputs to extract the reproduction signal of the magneto-optically recorded data. Further, the detector 3A is, for example, a light receiving element having a division surface, and the push-pull signal is detected by the detection circuit 5
Various servo signals are formed by extracting with
It supplies to the servo circuit 6 to drive the biaxial device, performs tracking servo and focus servo, detects the sum signal of the detector 3A, supplies it to the control data reproducing circuit 7, and supplies the master clock M _{CK and the} like. Forming,
This master clock M _{CK is applied} to the system control section 8
Output to.

Reference numeral 10 denotes a signal processing circuit for the reproduced signal demodulated by the differential amplifier 4, which has a constant amplitude A.
It includes a GC circuit. Further, 11 is a magneto-optical disk 1
This is a clamp circuit for the reproduction signal read from, and removes the DC offset component superimposed on the reproduction signal at the timing based on the clamp pulse supplied to the clamp circuit 11, and for example, keeps the "0" level constant. It is set to the voltage. The output of the clamp circuit 11 is supplied to the A / D converter 12 and converted into a digital signal.

Here, the bottom value of the A / D converter 12 and
Since the clamp circuit 11 is configured such that the bottom values of the signals output from the clamp circuit 11 are substantially the same, the digital signal output from the A / D converter 12 is effective in the A / D converter 12. Since it is within the range and fully utilizes this effective range, the accuracy of the analog-digital conversion becomes high, and the subsequent data detection unit correctly extracts the data and corrects the error data. Occurrence can be reduced.

The output of the A / D converter 12 is supplied to a data detection section 13 which is composed of a digital circuit, and the data detection section 13 extracts the recording data by the code conversion and the difference method, and the read clock R, for example. _CK is played back. Further, the data extracted by the data detection unit 13 is subjected to error detection and correction processing in the ECC processing unit 14, and is output as reproduction data. _{Reference numeral} 15 is a timing generator for generating clamp pulses (P (M), P (R)) based on the master clock M _CK and the read clock R _CK , 16 is an AND gate, and 17 is an OR gate.

On the other hand, the magneto-optical disk 1 is provided with a magnetic head portion 20 at a position opposed to the optical head 3.
A magnetic field that is inverted by the recorded data is applied. That is, the recording data supplied from the terminal 21 is subjected to predetermined code modulation and block formation in the recording data processing unit 22, further error correction code and the like are added, and the recording data is supplied to the magnetic head 20. ..

Further, at the time of signal processing in the recording data processing unit 22, for example, "0" is sent from the reference data unit 23.
A level signal is supplied, for example, several tens of bits of 0-level data is recorded in the ALPC area of the header segment H ₁ described above, and each data segment SG ₁ to
2 clocks for "0" bit data at the beginning of the data byte DB in the SG ₃₀ is adapted to be added.

Therefore, the ALPC area becomes a first clamp area where the reproduction level becomes 0 after data recording, and the reproduction signal in this clamp area becomes a saturated signal in which the data is 0. The first clamp area may be set to a predetermined area of the header segment H ₂ , for example. Further, the tip end portion of each data byte DB becomes a second clamp area magnetized so that the recording layer becomes "0", and thereafter, the record data is recorded.

The processing at the time of reproducing a certain target sector executed by this recording / reproducing circuit will be described with reference to FIGS.
In each figure, (a) shows the formats of the target sector and its preceding sector in which the reproducing operation should be performed,
(B) is an on / off state of reproduction laser scanning, (c)
(D) and (f) show various states of the reproduction signal, and (e) shows a clamp pulse.

FIG. 2 shows a normal reproducing operation. Figure 2
As can be seen from (b), laser scanning is in a standby state until the preceding sector is completed. That is, only the servo byte SB and the address area of the header segment H ₁ are laser-emitted and scanned. When the target sector is reached, the MO area is also scanned continuously and MO
The data magneto-optically recorded in the area is read. By this laser scanning, a reproduction signal in which the DC component is superimposed is obtained as shown in FIG. It should be noted that what is irregularly shown by vertical lines Re in the servo bytes SB and the address area is a signal leaking reproduction information due to embossed pits. A reproduced signal corresponding to actual MO data is indicated by M _R in the figure. The state in which the DC component is removed from this reproduced signal is shown in FIG.
It is shown in (d).

This reproduced signal is further clamped by the clamp circuit 11 based on the clamp pulses P (M) and P (R) shown in FIG. 2 (e), and a reproduced signal as shown in FIG. 2 (f) is obtained. That is, the first clamp area of the head portion of the target sector is sufficiently clamped based on the clamp pulse P (M), and then the head portion of each segment is clamped based on the clamp pulse P (R).
The clamp level will be followed. By this process M
The O reproduction signal M _R is set to the most appropriate level for the dynamic range of the A / D converter 12.

Here, the clamp pulse P (M) is generated and output by the timing generator 15 based on the master clock M _CK which is formed in synchronization with the clock pit at the time of reproduction, and the AND gate 16 and the OR gate 1 are output.
It is supplied to the clamp circuit 11 via 7. That is, by sampling the first clamp area with the clamp pulse P (M), the 0-level reference signal of the reproduction signal can be detected. Then, the read clock R _CK is formed by synchronizing the PLL circuit with the reproduction signal clamped by the reference signal.

Further, the second clamp area formed after the servo byte SB in each segment is sampled by the clamp pulse P (R) formed based on the read clock signal, and read from this portion. Since the reproduction signal for each data block is clamped by the sample signal, the second signal, which is as narrow as 2 clocks, can be used.
The clamping area can be reliably clamped. Since the second clamp area may be narrow, effective use of the data recording area DB is not hindered.

Next, a case will be described with reference to FIGS. 3 and 4 in which some defect such as a scratch or MO film defect exists in the first clamp region of the target sector. in this case,
When the scanning by the optical head reaches the target sector, the clamp operation is first performed on the reproduction signal level applied to the first clamp area based on the clamp pulse P (M). If noise due to a defect existing in the upper first clamp area appears in the reproduced signal, it is clamped at an incorrect level as shown in FIG.

Of course, since the second clamp area is provided at the head portion following the servo byte of each segment and is clamped based on the clamp pulse P (R), the normal clamp level can be gradually recovered. Arrogant
It will take a long time to fully recover,
The MO reproduction data in a considerable segment scanned during the recovery will be out of the dynamic range of the A / D converter 12. Such a reproduction signal is extracted by the data detection unit 13 and is judged as an uncorrectable error at the stage where the error correction processing is performed by the ECC processing unit 14, and eventually the data cannot be reproduced.

Therefore, in this embodiment, when the ECC processing section 14 supplies information about the occurrence of uncorrectable data to the system control section 8, a reproduction scan (hereinafter referred to as a retry) of the target sector in which a read error has occurred again. This is called reproduction.

The operation at the time of this retry reproduction is as shown in FIG. 4, that is, the laser scanning is started from the time when the preceding sector of the target sector is reached. Of course, since the clamp pulse P (M) and the clamp pulse P (R) are supplied, the MO reproduction signal is generated in the first clamp area set in the ALPC area of the preceding sector and the second clamp area in each segment. On the other hand, the clamp operation is performed. Of course, the data extraction operation is unnecessary for the scanning of the preceding sector.

Here, as described above, the magneto-optical disk 1
Since the bulk erase process is applied to, the MO reproduction signal having the same level and the same polarity as the first clamp region can be obtained even in the MO region of the sector in which the recording operation is not performed.
That is, the reproduction signal is clamped to at least the initialized saturation magnetic field level by the clamping operation in the first and second clamping regions of the preceding sector.

After that, the scanning of the optical head reaches the target sector again, and the defect detection signal D _D is supplied from the system controller 8 to the AND gate 16 at the timing corresponding to the first clamp area in this target sector. It This defect detection signal D _D causes the timing generator 15 to output the AND gate 1
The clamp pulse P (M) supplied to the other end of 6 is cut off and not supplied to the clamp circuit 11. That is, FIG.
As shown in (e), the clamp pulse P (M) is not generated in the target sector and the clamp operation is not executed, so the MO reproduction signal is the first and second reproduction signals in the preceding sector.
The clamp level in the clamp area is supplied to the A / D converter 12 as it is, and the clamp operation is executed when the second clamp area of the target sector is reached, and the clamp level is followed.

As described above, at the time of retry reproduction, the clamp operation is not executed in the first clamp area, but the reproduction signal is at least initialized saturated by the clamp operation in the first and second clamp areas of the preceding sector. Since it is clamped to the magnetic field level, the reproduced signal is A
Out of the dynamic range in the / D converter 12,
It never becomes unplayable. In other words, in the present embodiment, data reproduction can be realized by performing retry reproduction for a sector that is once determined to be unreproducible, and unreproducibility is avoided as much as possible, so the reliability of the disk system is greatly improved.

FIG. 5 shows an embodiment of the clamp circuit 11. B ₁ and B ₂ are buffer amplifiers, SS is a sample switch, C is a hold capacitor, and C ₁ is a comparator. The clamp pulse P (M) and the clamp pulse P (R) are supplied to the sample switch SS through the OR gate 17 to the contacts a and b for extracting the signals of the first and second clamp regions, respectively.
It is controlled so that it is turned on only during the period of this sampling pulse. Then, the clamp voltage E _C extracted with an appropriate time constant during this period is applied to the comparator C ₁ so that the bottom value of the reproduction signal becomes a constant reference level.

The sample time constant is set to be relatively long by making r ₁ small in the first clamp region to make it relatively short, and r ₂ > r _{1 in the second} clamp region. It is preferable to configure the circuit in

In this embodiment, 2 clocks of "0" data is recorded in the second clamp area, but 3 clocks of "0" data may be recorded. Further, the second clamp area can be provided at the middle portion or the rear end portion of the data byte DB by adjusting the timing of the clamp pulse P (R).

[0044]

As described above, in the reproducing method of the magneto-optical disk of the present invention, the magneto-optical recording on the data recording area in which the address test area having the first clamp area and the second clamp area are provided. The area is obtained from the first and second clamp areas when the reproducing operation is performed for a certain target sector with respect to the magneto-optical disk which is initialized so as to obtain the reproducing signal of the same polarity and the same level. Playback is performed by performing clamp processing on the level of the reproduced signal that is generated, and when a clamp failure occurs during the reproduction operation for the target sector, the reproduction operation is executed again from the preceding sector of the target sector, The reproduction signal from the first clamp area in the target sector is clamped to the reproduction signal obtained from the first and second clamp areas. Since the reproduction processing is performed on the data from the data recording area of the target sector without using it for the clamp processing, it is possible to read the data of the target sector which is once impossible to reproduce. Therefore, there is an effect that it is possible to avoid the occurrence of reproduction failure as much as possible. Therefore, the reliability of the disk system is significantly improved.

[Brief description of drawings]

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

FIG. 2 is a signal waveform diagram of a reproduction signal and a sample pulse during normal reproduction.

FIG. 3 is a signal waveform diagram of a reproduction signal and a sample pulse in the presence of a defect.

FIG. 4 is a signal waveform diagram of a reproduction signal and a sample pulse during retry reproduction.

FIG. 5 is a circuit diagram showing an example of a clamp circuit.

FIG. 6 is an explanatory diagram showing a format of a magneto-optical disk.

FIG. 7 is a detailed explanatory diagram of recording tracks.

[Explanation of symbols]

 1 Magneto-optical disk 2 Spindle motor 3 Optical head 8 System control unit 11 Clamp circuit 12 A / D converter 14 ECC processing unit 15 Timing generator

Claims (1)

[Claims] 1. A track formed concentrically or spirally on a magneto-optical disk is divided into a predetermined number of sector areas, and each divided sector has an address test area and this address test area. Then, a divided data recording area is formed, and the magneto-optical recording area of the address test area and the data recording area is initialized so that reproduction signals of the same polarity and the same level can be obtained. For the magnetic disk, a first clamp area is provided in the address test area, and a second clamp area is provided at a predetermined position in each of the data recording areas. When performing, the reproduction signal clamp processing is performed by using the reproduction signals obtained from the first and second clamp areas. Further, when a clamp failure occurs during the reproducing operation for the target sector, the reproducing operation is performed again from the preceding sector of the target sector, and the first and the first sectors in the preceding sector are executed. The reproduction signal obtained from the second clamp area is used to perform the clamp processing of the reproduction signal, and the reproduction signal from the first clamp area in the target sector is not used for the clamp processing. A reproducing method for a magneto-optical disk characterized in that a reproducing process is performed on data from a data recording area.