JPH0227549A - Magneto-optical disk device - Google Patents

Abstract

PURPOSE:To perform recording and reproduction satisfactorily without expanding the dynamic range of a reproduction circuit by detecting a prescribed area existing before each unit recording area, and forming saturated state sections whose magnetizing directions are arranged in prescribed directions in the area. CONSTITUTION:When data is recorded, a system controller 30 detects a sector on which the data is recorded by the output data of a demodulation circuit 19. And the prescribed area existing before each unit recording area is detected, and a first saturated state section whose magnetizing direction is aligned to a first prescribed direction and a second saturated state section whose magnetizing direction to a second prescribed direction are formed in the area. And when the reproduction is performed, the level of a signal obtained from each unit recording area is suppressed within a range from the prescribed level to the level different from the said prescribed level by difference between the levels corresponding to each saturated state section by clamping a part corresponding to the prescribed area. In such a way, it is possible to perform the recording and reproduction satisfactorily without expanding the dynamic range of the reproduction circuit.

Description

[Detailed description of the invention] Technical field The present invention relates to a magneto-optical disk device.

BACKGROUND ART In recent years, read-only and write-once optical discs have been put into practical use, and rewritable optical discs are also about to be put into practical use. In any of these types of optical discs, the track pitch is very narrow, about 1 to 2 μm, so concave or convex pits or grooves are previously formed on the disc to follow the tracks. By diffraction of light that is irradiated onto the disk and reflected by these pits or grooves, it is possible to detect the relative positional relationship in the disk radial direction between the track and the beam spot for information reading, and thereby the tracking servo that makes the beam spot follow the track. can be done. In addition, pits are used for information necessary for recording or reproducing data and for generating locks, information for dividing sectors, information for accessing sectors, information for dividing the inside of a sector into blocks, etc. These various types of information are read by diffraction of light by the pits. As described above, pits that are formed in advance on a disk and are intended to obtain information by diffraction of light are called embossed pits.

Examples of the arrangement (so-called format) of embossed pits on a disk are shown in FIGS. 4 to 7.

In the format shown in FIGS. 4 to 7, a virtually spiral track formed on the disk is divided into 1376 equiangular segments per revolution. Furthermore, one sector is composed of 43 consecutive segments. Therefore, one track (one track) consists of 32 sectors.

FIG. 4 is a diagram showing a segment configuration within one sector. Every segment consists of a 2-byte servo area and a 16-byte header area or data area, a total of 18 bytes. The first segment has a 16-byte hefter area, and the second to 43rd segments have a 16-byte data area. Note that one byte of all bytes in the servo area, header area, and data area is divided into 15 channel bits.

FIG. 5 is a diagram showing the configuration of the servo area.

One segment of servo area consists of 2 bytes.

The bytes constituting the servo area are respectively referred to as a first servo byte and a second servo byte. Two embossed pits are formed in the first servo bite. These are formed to be shifted from the virtual track center by about 1/4 track pitch in opposite directions in the radial direction of the disk. The first wobbled pit PWI is
The wobbled pits PW2 are formed at the position of the third or fourth channel bit while being switched every 16 tracks, and the second wobbled pit PW2 is formed at the position of the eighth channel bit. Using these two wobbled pits, a tracking error signal can be generated in a sampling manner once per segment. That is, when the beam spot passes through the virtual track center, it passes between the two wobbled pits, so the degree of diffraction in each wobbled pit is equal, and the reflected light is also equal.

Therefore, the tracking error signal obtained by taking the difference between the signals obtained by photoelectrically converting the amount of reflected light is zero (
(no error). Further, when the beam spot passes through the track with a deviation from the center of the virtual track, a difference occurs in the reflected light from the two wobbled pits, so a tracking error signal corresponding to the direction and amount of deviation is obtained. Since there are 1.376 segments in one rotation, the tracking error signal obtained by sampling at each servo byte is almost equivalent to one obtained continuously, making it possible to perform tracking servo. .

Also, one embossed bit is formed in the second servo byte exactly on the virtual track center at the position of the twelfth channel bit. This is Clock Pit P
It is called C. There is one clock pit PC in each segment at a fixed position in each servo byte, so by synchronizing the PLL with a signal that is reproduced at regular intervals from these pits, a clock with the frequency of the channel bit rate is generated. can do. Modulation is performed using this clock when recording data, and demodulation is performed using this clock when reproducing data as well.

Note that since there is a mirror surface between PW2 and PC, it is possible to generate a stable focus error in a sampling manner that is not affected by the presence or absence of pits.

Furthermore, since the interval between PW2 and PC is an interval (19 channel bits) that cannot appear in the 4/15 modulation method described later, segment synchronization can be performed by detecting this interval. It is possible.

FIG. 6 is a diagram showing the configuration within the header area. 1st
In the bite, sink marks are formed by embossed pits. The sync mark is a pit formed in the 2.7.8.9 channel bit, and is 4/15 as described below.
In the modulation method conversion table, this is a special pattern that does not correspond to any NRZ data. Therefore,
By detecting this, sector synchronization can be performed. The second byte is a sector address within one track, and the third to seventh bytes are track addresses within a disk, which are formed by embossed pits. These are modulated using a 4/15 modulation method, which will be described later, for each byte.

The 8th to 13th bites are reserved areas whose uses have not been determined, and have mirror surfaces without embossed pits.

The 14th to 16th bites are laser power control areas, and are initially mirror surfaces without embossed pits. When recording or erasing on a disc, it is desirable to use appropriate optical power, but in this area it is permissible to emit recording or erasing power on a trial basis from the optical pickup and correct the output power based on that. has been done.

FIG. 7 is a diagram showing the data area. The data area is 1
It is 6 bytes long, and in the unrecorded state, it has a mirror surface with no embossed pits. NRZ data is modulated one byte at a time using the 4/15 modulation method described later and recorded in this area. In the case of the write-once type, recording involves physical changes such as holes in the recording film. In the case of a rewritable disk that utilizes the magneto-optical effect (hereinafter referred to as a magneto-optical disk), such a physical change does not occur, but it does involve a change in which the direction of the magnetic field of the recording film is reversed.

The data area in one sector is 16x42-672.
There are bytes, which consist of user data, error correction codes, etc., but the details will not be described here.

Next, the 4/15 modulation method will be explained with reference to FIG. 4/15 modulation method 1 byte is converted into 15 channel bits, and from these 15 places, the original 256
41i locations (2II locations each for odd-numbered and even-numbered locations, excluding the 15th channel bit) are in one-to-one correspondence with the conversion table for the regular NRZ data.
record the mark. In other words, in the case of a write-once type, operations such as drilling holes in the recording film are performed, and in the case of magneto-optical disks,
Reversing the direction of magnetization of the recording film. Note that, as in the example shown in Figure 8, the marks are next to each other (see 12.13).
．． 14 channel bits), but there is always a gap of at least two channel bits (10th and 11th channel bits) between marks (9th and 12th channel bits) that are not adjacent to each other. However, as an exception, the 14th channel bit of one byte and the 1st channel bit of the next byte serve as marks, and one channel bit (1st
Although there may be cases where only the 15th channel bit (5th channel bit) is available, since the 15th channel bit will never become a mark, it will not cause any problems during demodulation.

Next, demodulation of data using 4/15 modulation method will be explained. FIG. 8 shows the re-main waveform corresponding to the mark.

In addition, in the case of drilling records, the reflected light at the mark position is darker than the reflected light at the unmarked position (mirror surface).
Also, some media that are not perforated undergo the opposite change.

However, in the 4/15 modulation method, demodulation is possible if there is a difference between the level at the mark position and the level at the mirror surface.
It is assumed that the reproduced waveform in FIG. 8 is not bright in the upper part of the figure, but simply shows the voltage level at a certain point in the demodulation circuit.

In addition, in the case of magneto-optical disks, it is not a mirror level, but
This is the erasure level. For demodulation, it is sufficient to specify the mark positions at 211 odd-numbered positions and 211 even-numbered positions among the 1st to 14th channel bits of a certain byte. Therefore, for example, by performing A/D conversion at the bit center of the first to fourteenth channel bits and comparing the magnitudes of the obtained digital data, the position of the mark can be specified. For example, in the example shown in Figure 8, ml, 3.5, 7, 9, 1
1. Among the 13 channel bits, the 13th channel bit has the highest level, and the 9th channel bit has the second highest level. (In this example, there are marks on the 14th channel bit and the 1st channel bit of the next byte, so the 1st
Although the level of the 5th channel bit may be higher than the level of the 9th channel bit, since the 15th channel bit never becomes a mark, it is not compared in size, and therefore does not cause a problem in demodulation. ) That is, it can be seen that there are marks on the 9th and 13th channel bits among the odd-numbered bits. Similarly, the second degree 4.6, 8, 10
, 12. Among the even-numbered channel bits of 14, the 12th . It can be seen that there is a mark on the 14th channel bit. Using the conversion table from these four marks,
The original NR2 data can be demodulated.

In short, demodulation of the 4/15 modulation method is based on comparing the reproduction levels at the center of each channel bit.

Next, an outline of the magneto-optical disk will be explained.

First, as with write-once optical discs, parts that will become embossed bits are created on a glass master disc by mastering, and a standby is created by electroforming.

Next, using this stubber as a mold, a polycarbonate resin or the like is injection molded to produce a substrate on which the embossed bits are transferred. Next, a thin film of TbFeCo alloy or the like is formed as a recording film on this substrate by a method such as sputtering to obtain a magneto-optical disk as shown in FIG.

The recording film 1 of the magneto-optical disk as shown in FIG. 9 produced in this way usually has a uniform reflectance of about several tens of percent. Therefore, light of uniform intensity is reflected on the mirror surface portion 2 without the embossed bit.

Further, in the embossed bit portion 3, the amount of reflected light is approximately several tens of percent of that of the mirror surface portion 2 due to a diffraction phenomenon.

Note that 4 is a substrate.

Next, an outline of the recording principle of a magneto-optical disk will be explained. In the initial state where a recording film is formed by a method such as sputtering as described above, the magnetic domains of the recording film are randomly arranged upward and downward in a direction perpendicular to the film surface. Generally, a magnetic field Hm stronger than the coercive force Hc of the film is applied to the disk in this initial state to align the direction of magnetization in one direction (erasing direction). This creates a disc with no signal (completely erased). This disk has a magneto-optical disk device (hereinafter referred to as a drive).
When recording information with , it is weaker than Hc and the direction is Hm.
While applying the opposite magnetic field H, a strong recording beam is irradiated only for the channel bit for which a mark is to be recorded.

Then, the temperature of that part rises and the coercive force becomes smaller than Hr, so the magnetization direction is reversed, and after the beam spot passes, the magnetization direction of that part becomes H', and the mark is not recorded. That means it's done.

When erasing recorded data using a drive, a strong erasing beam is applied while applying a magnetic field He that is weaker than Hc and in the same direction as Hm. As a result, the direction of the magnetic field in the area irradiated with the erasing beam is no signal, regardless of whether there is a mark or not! ! (It will be erased! In other words, the mark will be erased.)

During reproduction, a linearly polarized reproduction beam, which is weaker than the recording beam or erasing beam, is irradiated. The plane of polarization of the reflected light is slightly rotated by the Kerr effect, but the direction of rotation depends on the direction of magnetization. By detecting this with an analyzer, converting it into a change in intensity, and photoelectrically converting it, it is possible to obtain the potential difference between the mark location and the non-mark location.

Note that a differential optical system is generally used as a reproduction signal detection optical system of a magneto-optical pickup.

Although not particularly shown, this method divides the reflected light from the disk into two systems using a polarizing beam splitter, and by taking the difference between the respective photoelectrically converted signals, it obtains a magneto-optical reproduction signal and eliminates semiconductor laser noise and disk noise. It is well known that the in-phase noise such as minute reflection unevenness from the optical system is suppressed, and that it is indispensable as an optical system for reproducing magneto-optical signals. Note that the reproduced signal of the embossed bit is obtained by summing the two systems of signals.

When demodulating data recorded on a magneto-optical disk with the format described above, segment synchronization is first performed by detecting the interval between the embossed bits of PW2 and PC shown in FIG. Sector synchronization is performed by detecting the sync mark shown in FIG. As shown in FIG. 8, by performing A/D conversion on the magneto-optical signal reproduction waveform of each byte and comparing the sizes, it is possible to determine whether the recorded mark (i.e. direction of magnetization is changed from the erased state). (inverted channel bits)
Since the position of the data can be known, it is possible to demodulate the recorded data.

Generally, on an optical disc, data is not recorded sequentially in each sector, which is the smallest unit of recording, but randomly.

Therefore, it is naturally possible that a recorded sector appears after consecutive unrecorded sectors.

A magneto-optical disk device (hereinafter referred to as
In the drive (referred to as a drive), the playback signal is obtained by detecting minute changes in the Kerr rotation angle, so the amplitude of the signal read by the pickup is also very small, so the signal is increased to enable subsequent signal processing. Amplification is required, and for this purpose an AC coupled amplifier (hereinafter referred to as an AC amplifier) must be used. AC like this
FIG. 10 shows a circuit that performs demodulation processing after amplification by an amplifier.

In FIG. 10, a magneto-optical reproduction signal a (in the case of a differential optical system, a signal obtained by taking the difference between two channels) output from a pickup (not shown) is amplified by an amplifier 5, and then is amplified by a capacitor C1. The signal is supplied to an analog/digital (hereinafter abbreviated as A/D) converter 6 via the converter 6. A resistor R is connected between the input terminal of the A/D converter 6 and the ground.
1 is connected. After the magneto-optical reproduction signal a is converted into digital data by the A/D converter 6, it is supplied to a demodulation circuit (not shown) and subjected to 4/15 demodulation processing.

By the way, in the case of a magneto-optical disk, in a completely erased part, the direction of magnetization is aligned in a certain direction, and conversely, in a part that is completely recorded over a sufficiently long section, the direction of magnetization is erased. They are aligned in opposite directions, and there are two saturated states. However, in the initial state of the disk where the recording film was formed by sputtering etc.,
Since the direction of magnetization is random, it is in an undefined state between a completely erased state and a completely recorded state.

Now, just by forming a recording film in this way, the retention force of the film is H.
The waveform of the magneto-optical reproduction signal a obtained by the pickup in the vicinity of the recorded sector for a disk that has not been subjected to the entire erasing operation by applying a magnetic field Hm stronger than C is as shown in FIG. 11(A). .

Since neither recording nor erasing is performed in the unrecorded sector, the level of the magneto-optical reproduction signal a is an undefined level between the recording saturation level vR corresponding to the recording saturation state and the erasing saturation level Vε corresponding to the erasing saturation state. level. Therefore,
The level of the magneto-optical reproduction signal a obtained from an unrecorded sector may be very close to the recording saturation level vR, and the waveform may be as shown by the solid line, or the level may be very close to the erase saturation level vE. As a result, the waveform may become as shown by the dashed line. On the other hand, in the recorded sector, the data is erased by the -degree drive and then a mark is recorded in the channel bit corresponding to the data, so the level of the magneto-optical reproduction signal a is equal to the recording saturation level vR and the erase saturation level V= It changes depending on the mark position between. Note that here, the level difference between the recording saturation level vR and the erasing saturation level VE is assumed to be e.

The waveform of the input signal S to the A/D converter 6, to which the magneto-optical reproduction signal a is supplied via the AC-coupled capacitor CI, is as shown in FIG. 11(B). While reading an unrecorded sector, regardless of whether the level of the magneto-optical reproduction signal a is near vR or near VE, the A/D
The level of the input signal to the converter 6 is approximately equal to the ground level. However, when the beam spot for reading information moves to the recorded sector, if the level of the magneto-optical reproduction signal a just before that is close to the VR level, the level of the input signal S is approximately -e and the ground level. The waveform becomes as shown by the solid line. Furthermore, when the beam spot for reading information moves to a recorded sector, if the level of the magneto-optical reproduction signal a immediately before that is a level near VE, the level of the input signal a is approximately the ground level and +e.
The waveform changes between , and the waveform becomes as shown by the dashed line.

Therefore, it is necessary to use an A/D converter 6 having a dynamic range of 2e even though the maximum signal amplitude is only e. In order to widen the dynamic range of the A/D converter while maintaining good resolution, one extra bit is required, but as in this example, if the period of each channel bit is short (the number of disk rotations is 3)
A that performs A/D conversion in approximately 90 ns at 0RPS)
/D converter becomes very expensive if it increases by even 1 bit.

Therefore, it is conceivable to apply a magnetic field Hm stronger than the coercive force Hc of the film to the disk on which the recording film has been formed by sputtering to erase the entire surface. By doing so, the level of the magneto-optical reproduction signal a in the unrecorded sector shown in FIG. will always change between the ground level and +0. However, in order to erase the entire disk, a magnetic field Hm that is sufficiently stronger than the coercive force Ha of the film is required.
(Generally, the Hc of the recording film is set to be quite large in order to avoid being affected by leakage magnetic flux from the drive actuator, spindle motor, etc., so the Hm required to overcome this is extremely large. ) must be applied to the entire surface of the disk without fail, and the equipment for that purpose becomes large-scale. Furthermore, since it takes a lot of man-hours to erase each disc one by one and inspect it, this increases the cost of the disc. Another possibility is to raise the temperature of the disk and erase the entire surface using a magnetic field weaker than Hm, but if the substrate is made of resin, there are restrictions on the temperature, and of course it requires equipment and time to raise the temperature. It becomes.

Furthermore, even if the entire area is erased, if the recorded sector continues for a very long time, a sag due to AC coupling will gradually appear in the input signal of the A/D converter 6, as shown in FIG. Therefore, the dynamic range must be larger than e.

Furthermore, although the explanation has been made assuming that e is constant, since the medium of optical discs is replaceable, it is necessary for the drive to be able to play discs with various variations. Therefore, it is necessary to set the dynamic range of the A/D converter to the maximum value of e, and if the value of e becomes small due to variations,
The resolution of the /D converter would be reduced, which could lead to a worsening of the error rate.

Summary of the Invention The present invention has been made in view of the above points, and includes:
It is an object of the present invention to provide a magneto-optical disk device that can perform good recording and reproduction using an inexpensive magneto-optical disk without expanding the dynamic range of a circuit that reproduces recorded information.

In order to achieve the above object, in the magneto-optical disk device according to the present invention, a predetermined area existing before each unit recording area is detected, and the direction of magnetization of the detected predetermined area is aligned in a first predetermined direction. At least one of the first saturated state section and the second saturated state section in which the direction of magnetization is aligned in the second predetermined direction is formed.

During reproduction, it is preferable to clamp the portion of the output of the pickup corresponding to one section in the predetermined region to a predetermined level, and then perform signal processing of the output of the pickup.

Furthermore, during reproduction, the gain of the circuit that processes the output of the pickup may be controlled depending on the difference between the levels of the signals read from each of the first and second saturation sections.

Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 3.

In FIG. 1, 10 is a magneto-optical pickup;
A light receiving element 12.1 that receives light from both channels of the semiconductor laser 11 as a light source and the differential optical system and performs photoelectric conversion.
3 is built-in. The light receiving elements 12 and 13 detect, for example, laser beams emitted from the semiconductor laser 11 and reflected by the magneto-optical disk 15 through analyzers, and one detects the positive direction component of the Kerr rotation angle. , the other detects the negative direction component of the Kerr rotation angle. The magneto-optical disk 15 is rotated at a predetermined speed by a spindle motor 16 that is driven and controlled by a spindle servo circuit (not shown). The pickup 10 further includes a focus actuator and a tracking actuator, which are driven by a focus servo circuit and a tracking servo circuit. By these servo circuits etc., the semiconductor laser 1
The laser beam emitted from the magneto-optical disk 15 is accurately focused on the recording surface of the magneto-optical disk 15 to form a beam spot, and this beam spot accurately follows the track. It is omitted because it is not.

The outputs of the light receiving elements 12 and 13 are added by an adder 17 to form an embossed bit reproduction signal d. Also,
At the same time, the output of the light receiving elements 12 and 13 is
One is subtracted from the other to form the magneto-optical reproduction signal a.

The embossed pit reproduction signal d is supplied to a 4/15 demodulation circuit 19 and a synchronization circuit 20. The synchronization circuit 20 is configured to generate a segment synchronization signal and a sector synchronization signal based on the embossed pit reproduction signal d. The segment synchronization signal and sector synchronization signal output from the synchronization circuit 20 are supplied to a timing signal generation circuit 21. The timing signal generation circuit 21 is configured to generate various timing signals based on the segment synchronization signal and the sector synchronization signal and supply them to each section.

Furthermore, the 4/15 demodulation circuit 19 demodulates the portion of the embossed pit reproduction signal d corresponding to the embossed bits including the sector address and track address information in the header area using the timing signal from the timing signal generation circuit 21. It is configured to output data indicating a sector address and a track address.

On the other hand, the magneto-optical reproduction signal a is amplified by an amplifier 22 and then supplied to an A/D converter 24 and a sample hold circuit 25 via an AC coupling capacitor 02 and an analog switch 23. An analog switch 26 and a resistor R are connected between the input terminal of the A/D converter 24 and ground.
2 are connected. The analog switches 23 and 26 are supplied with ON command signals f and g from the timing signal generation circuit 21. The sample hold circuit 25 also receives a sampling pulse h from the timing signal generation circuit 21.
is supplied.

The output j of the sample hold circuit 25 serves as a full scale input to the A/D converter 24.

The A/D converter 24 has a dynamic range set from the ground level to the full-scale input level. The output data of this A/D converter 24 is supplied to a 4/15 demodulation circuit 28.

Further, a drive signal is supplied to the semiconductor laser 11 in the pickup 10 from a drive circuit 29 .

The drive circuit 29 is supplied with a timing signal from the timing signal generation circuit 21 and the system controller 3
Various commands output from 0 and recording signals output from a 4/15 modulation circuit (not shown) are supplied. The drive circuit 29 constantly outputs a constant level signal having an amplitude corresponding to the low level laser power for reading information, and also has an amplitude corresponding to the laser power during erasing in response to an erasing command from the system controller 30. The drive pulse signal k is superimposed on the constant level signal in synchronization with the timing signal,
In response to a recording command, a drive pulse signal g having an amplitude corresponding to the laser power during recording is superimposed on a constant level signal according to a recording signal output from a 4/15 modulation circuit (not shown), and forced irradiation is performed. In response to the command, the above drive pulse signal g
The configuration is such that the signal is superimposed on a constant level signal.

Various commands output from the system controller 30 are as follows:
Furthermore, it is supplied to the magnetic field application circuit 32. Magnetic field application circuit 32
is configured to supply a drive signal according to a command to the coil of the magnetic field application mechanism.

When an erasing command is generated, the magnetic field applying circuit 32 and the coil L apply an erasing magnetic field He of a predetermined strength, and when a recording command or forced irradiation command is generated, a recording magnetic field H'' whose direction is opposite to the erasing magnetic field He is applied. be done.

The system controller 30 includes a processor, ROM, R
It is formed by a microcomputer such as AM. The system controller 30 is further supplied with output data of the 4/15 demodulation circuit 19. The system controller 30 generates various commands as described below using a processor that operates according to a program stored in advance in the ROM.

When recording data, the system controller 30
The sector in which data is to be recorded is detected based on the output data of the /15 demodulation circuit 19, and when the sector is detected, the reserved area from the 8th byte to the 13th byte of the header area is determined by the timing signal from the timing signal generation circuit 21. Then, the data area of each of the second to forty-third segments is detected and an erase command is sent to the drive circuit 29 and the magnetic field application circuit 32.

Then, when the beam spot passes over the sector to be recorded as shown in the m2 diagram (A) I, the semiconductor laser 11
As shown in the same figure (B), a drive pulse signal k having an amplitude corresponding to the laser power during erasing is superimposed on a constant level signal that is constantly supplied to the reserve area and each of the second to 43rd segments. The data area becomes erased.

Next, the system controller 30 detects the sector in which data is to be recorded again based on the output data of the 4/15 demodulation circuit 19, and when the sector is detected, the system controller 30 uses the timing signal to detect the sector in which data is to be recorded. After detecting the area and sending a forced irradiation command to the drive circuit 29 and the magnetic field application circuit 32, detecting each data area of the M2 segment to the 43rd segment and sending a recording command to the drive circuit 29 and the magnetic field application circuit 32. do.

Then, a driving pulse signal g having an amplitude corresponding to the laser power during recording is superimposed on the constant level signal constantly supplied to the semiconductor laser 11, as shown in FIG. Marks are recorded over the entire area up to the 13th byte, that is, the latter three bytes of the reserve area, and marks corresponding to the recording signal are recorded in the data areas of each of the second to 43rd segments.

As described above, the state of the track becomes as shown in FIG. 2(D), and a disc recorded as shown in FIG. 3 is obtained.

As shown in FIG. 3, the segment configuration within one sector of the magneto-optical disk on which information is recorded by the apparatus according to the present invention is similar to the format shown in FIGS. 4 to 7, but the reserved area in the header area is The first three bytes are in an erase saturation state, and the latter three bytes are in a recording saturation state.

Next, during playback, the system controller 30
A reading command is sent to the drive circuit 29 and the magnetic field application circuit 32. Then, only a constant level signal having an amplitude corresponding to the low level laser power for information reading is supplied to the semiconductor laser 11, and a magneto-optical reproduction signal a as shown in FIG. 2(E) is output from the subtraction circuit 18. Ru. The level of the magneto-optical reproduction signal a becomes unstable in the embossed pit area and the laser power control area where erasing is not performed, but it becomes equal to the erase saturation level vE in the first three bytes of the reserve area, and in the second half of the reserve area. At 3 bytes, it becomes equal to the recording saturation level VR. Also,
In the data area, the level of the magneto-optical reproduction signal a changes between the erase saturation level VE and the recording saturation level VR.

At this time, if the ON command signal f is supplied to the analog switch 23 only during the 6-byte period of the reserve area and in each data area from the 2nd segment to the 43rd segment, as shown in FIG. 2 (CF). , no abnormal charge is accumulated in the capacitor C2 due to the undefined level of the magneto-optical reproduction signal a. Also, analog switch 2
6 acts as a clamp circuit together with the capacitor C2, so if the ON command signal g is supplied to the analog switch 26 only during the second byte period of the reserve area as shown in FIG. The erase saturation level of the input signal C of the /D converter 24 is clamped to the ground level. Therefore, as shown in FIG. 2(H),
The recording saturation level of the latter three bytes of the reserve area of the input signal C of the D converter 24 is 10, and the level of the input signal C of the A/D converter 24 in the data area changes between the ground level and +e. become. Therefore, in the A/D converter 24, A/D conversion is performed regardless of whether the immediately preceding sector is unerased, erased, or recorded. The dynamic range of the D converter 24 should always be from the ground level to +e.

Furthermore, if the sampling pulse h is supplied to the sample and hold circuit 25 only during the period of the 5th byte of the reserve area as shown in FIG. signal a
The level of is equal to the recording saturation level vR, and the input signal C of the A/D converter 24 is a signal obtained by clamping the magneto-optical reproduction signal a using the analog switch 26 and the capacitor C2 with respect to the ground level. Therefore, +e is input to the sample hold circuit 25. Therefore, as shown in FIG. 2(J), the level of the output j of the sample and hold circuit 25 is held at +e for one sector thereafter.

The output j of this sample hold circuit 25 is the full scale input of the A/D converter 24, so the A/D
In the D converter 24, the A/D conversion of the magneto-optical reproduction signal a is performed with the range from the erase saturation level Vε to the recording saturation level vR as the full scale. Therefore, even if the level difference between the erase saturation level Vε and the recording saturation level vR changes due to variations between disks or drives, automatic gain control is performed so that A/D conversion is always performed within the optimal dynamic range. The action will take place.

Although the formats shown in FIGS. 4 to 7 have been described above, the present invention can be applied not only to the above formats but also to other formats, and the minimum unit of recording is A similar effect can be obtained by recording at least one of the erase saturation level and the recording saturation level in an area located before the data recording area in the sector.

Furthermore, in the above embodiment, erasing and recording were performed independently of each other, but it is also possible to perform so-called override, in which erasing and recording are performed at the same time. You can write both at the same time.

Furthermore, in the above embodiment, both the erase saturation level and the recording saturation level are recorded in the reserve area, but only one of the erase saturation level and the recording saturation level may be recorded. . However, in that case, automatic gain control cannot be achieved, but clamping is possible, so the dynamic range of the A/D converter can be reduced.

In addition, although the device of the above embodiment had both recording and reproducing functions, since the magneto-optical disk device is capable of replacing the medium, it can also take the form of a recording-only device that can only record or a reproduction-only device that can only perform playback. Yes, the present invention can also be applied to these recording-only machines and reproduction-only machines.

Effects of the Invention As detailed above, in the magneto-optical disk device according to the present invention, a predetermined area existing in front of each unit recording area is detected, and the direction of magnetization of the detected predetermined area is aligned in the first predetermined direction. Since at least one of the first saturated state section and the second saturated state section in which the direction of magnetization is aligned in the second predetermined direction is formed, the "pickup output By clamping a portion corresponding to one section in the above-mentioned predetermined region to a predetermined level, the level of the signal obtained from each unit recording area is the difference between the predetermined level and the level corresponding to the first and second saturation state sections, respectively. It is possible to perform good recording and reproduction using an inexpensive disk that is not completely erased without expanding the dynamic range of the circuit that reproduces the recorded information. Since the dynamic range of the A/D converter in the circuit for reproducing recorded information can be effectively utilized, an increase in the manufacturing cost of the magneto-optical disk device can be prevented.

Furthermore, during playback, the gain of the circuit for signal processing of the output of the pickup is controlled according to the difference between the levels of the signals read from each of the first and second saturation sections, thereby controlling the gain of the circuit for signal processing of the output of the pickup. Even if there is a variation in the level difference between the signals read from each of the first and second saturation state sections due to the variation between the levels, signal processing can be performed in the optimum dynamic range, which is preferable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention.
Timing chart showing the operation of each part of the device shown in Figure 3.
The figure shows a disk recorded by the apparatus of FIG. 1, FIGS. 4 to 7 show the recording format of a magneto-optical disk, and FIG. 8 shows the recording state of the data area and the read signal. 9 is a sectional view showing the structure of a magneto-optical disk, FIG. 10 is a block diagram showing a reproducing circuit of a conventional device, and FIGS. 11 and 12 are 10 FIG. 3 is a waveform diagram showing the operation of each part of the circuit shown in the figure. Explanation of symbols of main parts 10...Pickup 15...Disk 18...Subtractor

Claims (3)

[Claims] (1) A magneto-optical disk device that records information on a magneto-optical disk in which a plurality of unit recording areas each having a predetermined recording capacity are arranged in the circumferential direction. a means for detecting at least one of a first saturated state section in which the direction of magnetization is aligned in a first predetermined direction and a second saturated state section in which the direction of magnetization is aligned in a second predetermined direction in the predetermined region; 1. A magneto-optical disk device comprising: means for forming. (2) a plurality of unit recording areas having a predetermined recording capacity and arranged in the circumferential direction; and a first unit recording area arranged in front of the plurality of unit recording areas and having a magnetization direction aligned in a first predetermined direction.
A magneto-optical disk device for reproducing information recorded on a magneto-optical disk having a saturated state section and a predetermined area including at least one of a second saturated state section in which the direction of magnetization is aligned in a second predetermined direction, A pickup for reading a recorded signal on the magneto-optical disk, and a clamping means for clamping a portion of the output of the pickup corresponding to the one in the predetermined area to a predetermined level, the output of the pickup being clamped by the clamping means. A magneto-optical disk device characterized by signal processing. (3) a plurality of unit recording areas having a predetermined recording capacity and arranged in the circumferential direction; and a first unit recording area arranged in front of the plurality of unit recording areas and having a magnetization direction aligned in a first predetermined direction.
A magneto-optical disk device for reproducing information recorded on a magneto-optical disk having a saturated zone and a predetermined area including a second saturated zone in which the direction of magnetization is aligned in a second predetermined direction, a pickup that reads a recorded signal; and a difference signal generator that generates a difference signal according to the difference between the level of the signal read from the first saturated section and the level of the signal read from the second saturated section by the pickup. A magneto-optical disk device comprising means for controlling the gain of the means for signal processing of the output of the pickup using the difference signal.