JP2001056978A - Data reproducing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable reproducing clock signal unaffected by a ghost signal. SOLUTION: A reproducing signal SMO' includes the ghost signal caused by the movement of a magnetic wall from the rear side of the temperature range of a switching layer becoming equal to or higher than a Curie temperature. The discrimination is made after the specified time by a pattern discriminating circuit 227 whether a pattern of recording magnetic domain of the part of a magneto-optical disk corresponding to the rear end side of the aforementioned temperature reigon is the pattern for generating the ghost signal such as changing an edge phase of a binary signal S2 or not, then the pattern discriminating signal PD is supplied to a gate circuit 215 as a control signal through a delay circuit 228. An edge detecting signal PN, the phase of which is being affected by the ghost signal, is not supplied to a phase comparator 213 by the operation of the gate circuit 215. A wrong phase error signal PE affected by the ghost signal does not be outputted from the phase comparator 213, thereby the stable clock signal CLK is obtained from an oscillator 212.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic layer having at least a magnetic layer of a moving layer, a switching layer, and a memory layer. The present invention relates to a data reproducing apparatus and method for handling a magneto-optical recording medium in which the size of a generated and effectively recorded magnetic domain is enlarged. Specifically, when the phase of the edge detection signal of the binary signal is affected by the ghost signal included in the reproduction signal, the oscillation frequency of the oscillator is not controlled by the phase error signal related to the edge detection signal, or The present invention relates to a data reproducing apparatus and a data reproducing method which removes the influence of a ghost signal from a phase error signal related to an edge detection signal to obtain a stable reproduced clock signal without the influence of a ghost signal.

[0002]

2. Description of the Related Art There is a magneto-optical recording medium as a rewritable high-density recording medium. In recent years, at least in the region where the magnetic layer temperature is equal to or higher than the Curie temperature of the switching layer, domain wall motion of the moving layer occurs at least in a region formed of a magnetic three-layer film of a moving layer, a switching layer, and a memory layer. Attention has been paid to a magneto-optical recording medium in which the size of a magnetic domain recorded on a magneto-optical recording medium is enlarged (see JP-A-6-290496). Displacement Detection) method. In the DWDD method, a very large signal can be reproduced even from a minute recording magnetic domain having a period equal to or less than the optical limit resolution of a light beam.
This is one of the promising methods for achieving high density without changing the numerical aperture NA or the like of the objective lens.

[0003] The DWDD system will be described in more detail. As shown in FIG. 7A, the magneto-optical recording medium 10
The moving layer 11, the switching layer 12, and the memory layer 13 are formed of an exchange-coupled three-layer film laminated in this order. The memory layer 13 is formed of a perpendicular magnetization film exhibiting a large domain wall coercive force. The moving layer 11 is formed of a perpendicular magnetic film having a small domain wall coercive force and a large domain wall mobility. The switching layer 12 is formed of a magnetic layer exhibiting a lower Curie temperature Ts than the moving layer 11 and the memory layer 13. Arrows 14 in each layer indicate the direction of the atomic spin. The domain wall 1 is located at the boundary between the regions where the directions of the atomic spins are opposite to each other.
5 are formed.

When the surface of the recording film is locally heated using a light beam (laser beam) 16 for reproduction, a distribution of a temperature T is formed as shown in FIG. Is formed as shown in FIG. 7C. Since the domain wall energy density σ generally decreases as the temperature rises, the distribution is such that the domain wall energy density σ is lowest at the position of the maximum temperature. As a result, a domain wall driving force F (x) for moving the domain wall energy density σ to a high temperature side is generated as shown in FIG. 7D. FIG. 7E
Shows the positional relationship between the spot 16P of the light beam 16 and the temperature region 17 higher than the Curie temperature Ts of the switching layer 12.

When the temperature of the medium 10 is lower than the Curie temperature Ts of the switching layer 12, since the magnetic layers are exchange-coupled to each other, the domain wall driving force F (x) due to the above-mentioned temperature gradient acts. In addition, the domain wall 15 does not move because of the large domain wall coercive force of the memory layer 13. However, in a place where the temperature of the medium 10 is higher than the Curie temperature Ts, the exchange coupling between the moving layer 11 and the memory layer 13 is broken, so that the domain wall 15 of the moving layer 11 having a small domain wall coercive force is broken.
Can be moved by the domain wall driving force F (x) due to the temperature gradient. For this reason, as the light beam 16 scans the medium 10, the domain wall 15 of the moving layer 12 moves to the high-temperature side at the moment when the domain wall 15 enters the bond cutting region beyond the position of the Curie temperature Ts.

Each time a domain wall 15 formed on the medium 10 at an interval corresponding to a recording signal passes through the position of the Curie temperature Ts as the light beam 16 scans the medium, the movement of the domain wall 15 of the moving layer 11 changes. appear. As a result, the size of the effectively recorded magnetic domain is enlarged, so that a very large signal can be reproduced from a minutely recorded magnetic domain having a period equal to or shorter than the optical limit resolution of the light beam 16.

When the light beam 16 scans the medium 10 at a constant speed, the above-described domain wall movement occurs at time intervals corresponding to the spatial intervals of the domain walls 15 recorded. The occurrence of the domain wall movement can be detected as a change in the plane of polarization of the reflected light of the light beam (laser beam) 16.

[0008]

By the way, as shown by a broken line in FIG. 7A, domain wall movement also occurs from the rear of the temperature region 17. Therefore, the above-mentioned signal due to the domain wall movement from the rear is superimposed as a ghost signal on the reproduction signal due to the domain wall movement from the front. Therefore, when a reproduced signal is converted into a binarized signal and a reproduced clock signal is generated using the edge information of the binarized signal, the edge phase of the binarized signal fluctuates due to the influence of the ghost signal described above. Therefore, a stable reproduced clock signal cannot be obtained. If it becomes impossible to obtain a stable reproduction clock signal in this manner, the process of obtaining reproduction data using this reproduction clock signal will not be performed well.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a data reproducing apparatus and a data reproducing method capable of obtaining a stable reproduced clock signal which is not affected by a ghost signal.

[0010]

A data reproducing apparatus according to the present invention is a data reproducing apparatus of a DWDD system, and irradiates a light beam from a moving layer side while moving the light beam relative to a magneto-optical recording medium. A domain wall formed in the moving layer by forming a temperature distribution having a gradient with respect to the moving direction of the spot of the light beam on the magneto-optical recording medium and having a temperature region higher than at least the Curie temperature of the switching layer. And a signal reproducing means for obtaining a reproduced signal corresponding to the change in the polarization plane of the reflected light of the light beam; a clock reproducing means for obtaining a reproduced clock signal based on the reproduced signal; and a reproducing clock signal for the reproduced signal. Reproduction processing means for obtaining reproduction data by performing the used processing, wherein the clock reproduction means has the following configuration.

That is, the clock reproducing means includes a binarizing circuit for converting the reproduced signal into a binarized signal, an edge detector for detecting at least one of a rising edge and a falling edge of the binarized signal, and a reproducing clock. An oscillator that outputs a signal, a phase comparator that compares a phase of an edge detection signal from an edge detector with a recovered clock signal to obtain a phase error signal that controls an oscillation frequency of the oscillator, and a phase of the edge detection signal, Determining means for determining whether or not the movement of the domain wall on the rear end side of the temperature region higher than the Curie temperature of the switching layer is affected by a ghost signal included in the reproduction signal; and the phase is affected by the ghost signal. Control suppression means for suppressing that the oscillation frequency of the oscillator is controlled by the phase error signal related to the edge detection signal determined to be present; Those having.

For example, when the magnetic domain having a predetermined length or more is continuously formed in a portion corresponding to the rear end of the temperature region of the magneto-optical recording medium, the determining means determines a phase of the edge detection signal. Is determined to be affected by the ghost signal. In this case, for example, the determination is made based on the pattern of the reproduction signal before a certain time corresponding to the moving time of the predetermined portion of the magneto-optical recording medium from the front end to the rear end of the temperature distribution.

[0013] For example, the control suppressing means does not supply an edge detection signal whose phase is determined to be affected by the ghost signal to the phase comparator, or controls the phase to be affected by the ghost signal. The phase error signal obtained from the phase detector in response to the edge detection signal determined to be present is not supplied to the oscillator.

The present invention relates to the DWDD reproduction, and the reproduction signal includes the above-mentioned ghost signal due to domain wall movement from behind. For example, when the ghost signal is obtained from a portion in which magnetic domains longer than a certain length are continuously formed, the phase of the edge detection signal fluctuates under the influence of the ghost signal. When the phase of the edge detection signal is affected by the ghost signal included in the reproduction signal, a stable reproduction clock not affected by the ghost signal is obtained by not controlling the oscillation frequency of the oscillator with the phase error signal related to the edge detection signal. A signal can be obtained.

Further, a data reproducing apparatus according to the present invention
In a WDD type data reproducing apparatus, a light beam is irradiated from the side of a moving layer while being moved relatively to a magneto-optical recording medium, and the light beam is irradiated on the magneto-optical recording medium in a moving direction of a spot of the light beam. By forming a temperature distribution having a gradient and at least a temperature region higher than the Curie temperature of the switching layer, the domain wall formed in the moving layer is moved, and reproduction corresponding to the change in the polarization plane of the reflected light of the light beam is performed. A signal reproducing means for obtaining a signal; a clock reproducing means for obtaining a reproduced clock signal based on the reproduced signal; and a reproducing processing means for performing processing using the reproduced clock signal on the reproduced signal to obtain reproduced data; The reproducing means has the following configuration.

That is, the clock reproducing means includes a binarizing circuit for converting the reproduced signal into a binarized signal, an edge detector for detecting at least one of a rising edge and a falling edge of the binarized signal, and a reproducing clock. An oscillator that outputs a signal; a phase comparator that compares the phase of an edge detection signal from an edge detector with a recovered clock signal to obtain a phase error signal that controls the oscillation frequency of the oscillator; A pattern detecting means for detecting a recording magnetic domain pattern of the magneto-optical recording medium at a division corresponding to a rear end side of the high temperature region; and a phase error obtained by a phase comparator for each pattern detected by the pattern detecting means. A storage unit for storing the average value of the signal in the storage unit, and reading the average value corresponding to the pattern detected by the pattern detection unit from the storage unit. And, those having an error correcting means for correcting the phase error signal obtained by the phase comparator on the basis of the average value. For example, the pattern detection means
The recording magnetic domain pattern is detected based on a reproduction signal pattern that is a predetermined time corresponding to a moving time of a predetermined portion of the magneto-optical recording medium from the front end to the rear end of the temperature region.

The present invention relates to DWDD reproduction, and the reproduction signal includes the above-mentioned ghost signal due to domain wall movement from behind. This ghost signal corresponds to the recording magnetic domain pattern corresponding to the rear end side of the temperature region, and the average value of the phase error signal for each pattern is the phase of the edge detection signal based on the ghost signal corresponding to each pattern. Corresponding to the fluctuation of Therefore, by correcting the phase error signal with the average value corresponding to the pattern, it is possible to obtain a stable reproduced clock signal that is not affected by the ghost signal.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a magneto-optical disk drive 100 of the DWDD system as an embodiment. The magneto-optical disk 111 handled by the disk device 100 has a magneto-optical recording medium 10 as shown in FIG. 7A as a recording film on a substrate made of glass or plastic, and further has a protective film thereon. Is formed.

The disk drive 100 includes a spindle motor 1 for rotationally driving the magneto-optical disk 111 described above.
13. The magneto-optical disk 111 is rotated at a constant angular velocity, for example, during recording and reproduction. A frequency generator 114 for detecting a rotation speed of the spindle motor 113 is attached to a rotation shaft of the spindle motor 113.

The disk drive 100 includes a magnetic head 115 for generating an external magnetic field, a magnetic head driver 116 for controlling the generation of a magnetic field of the magnetic head 115, a semiconductor laser, an objective lens, a photodetector, and the like. It has an optical head 117 and a laser driver 118 for controlling the emission of the semiconductor laser of the optical head 117.
The magnetic head 115 and the optical head 117 are arranged to face each other with the magneto-optical disk 111 interposed therebetween.

The laser driver 118 is supplied with a laser power control signal SPC from a servo controller 141, which will be described later. The power of the laser beam output from the semiconductor laser of the optical head 117 becomes the recording power PW during recording and the recording power PW during reproduction. Reproduction power PR lower than power PW
It is controlled so that

At the time of writing data (at the time of recording), the NRZI (Non Re
Record data D as turn to Zero Inverted) data
r is supplied, and the recording data D
A magnetic field corresponding to r is generated, and the recording data Dr is recorded on the magneto-optical disk 111 in cooperation with the light beam (laser beam) from the optical head 117.

The disk device 100 has a CPU (ce
ntral processing unit). The servo controller 141 includes a focus error signal SFE and a tracking error signal STE generated by the optical head 117, and a frequency signal SFG output from the frequency generator 114 described above.
Is supplied.

The operation of the servo controller 141 is controlled by a system controller 151 described later.
The servo controller 141 controls the tracking coil, the focus coil, and the optical head 117.
The actuator 145 including a linear motor for moving the optical head in the radial direction is controlled to perform tracking and focus servos, and the movement of the optical head 117 in the radial direction (radial direction) is controlled. Further, the spindle motor 11 is controlled by the servo controller 141.
3 is controlled so that the magneto-optical disk 111 rotates at a constant angular velocity, for example, during recording or reproduction as described above.

The disk device 100 includes a system controller 151 having a CPU and a data buffer 1.
52 and a SCSI (Small Computer System) for transmitting and receiving data and commands between the host computer.
Interface) 153. The system controller 151 controls the entire system.

The disk device 100 adds an error correction code to write data supplied from the host computer through the SCSI 153, and performs error correction on output data of the data demodulator 160 described later. An ECC (error correction code) circuit 154 and a data bit string of write data to which an error correction code is added by the ECC circuit 154 are RLL (Run
Length Limited) modulated bits and then NRZ
And a data modulator 155 for obtaining recording data Dr by converting the data into I data.

Here, for example, (1,7) RLL modulation is used as RLL modulation. This (1,7) R
In the LL modulation, 2-bit data is converted into 3 channel bits, thereby limiting the number of 0s between 1 and 1 of the channel bits to 1 to 7. The NRZI data is obtained by associating 1 of channel bits with polarity inversion and 0 with channel non-inversion. In this case, the polarity inversion interval is between 2 channel bits and 8 channel bits.

The disk device 100 includes a waveform equalizing circuit 156 for performing a waveform equalizing process on the reproduced signal SMO obtained from the optical head 117, and a reproduced signal S on which the waveform is equalized.
MO 'is converted into a binary signal S2, for example, a binary circuit 157 composed of a comparator, and a PLL (phase-locked loop) for reproducing a clock signal CLK from the binary signal S2.
The circuit 158 and the clock signal CLK from the binarized signal S2
Data detection circuit 1 for detecting reproduction data Dp using
59, and a data demodulator 160 that demodulates the reproduced data (RLL modulated data) Dp to obtain read data.

Next, the PLL circuit 158 and the data detection circuit 159 will be described in more detail. FIG.
4 shows a configuration example of a PLL circuit 158 and a data detection circuit 159.

The PLL circuit 158 detects at least one of the rising edge and the falling edge of the input binary signal S2, here both edges, and generates an edge detection signal PN on a pulse. 2
11, a voltage controlled oscillator (VCO) 212 for generating a clock signal CLK, and a phase comparison for comparing phases of an edge detection signal PN output from an edge detector 211 and a clock signal CLK output from the voltage controlled oscillator 212. 213 and a loop filter 214 for filtering the phase error signal PE output from the phase comparator 213 with appropriate frequency characteristics and supplying the filtered signal to the voltage controlled oscillator 212 as a control signal.

The PLL circuit 158 has an A / D converter 221 for converting the input reproduced signal SMO 'from an analog signal to a digital signal. in this case,
Clock signal CL output from voltage controlled oscillator 212
K is used as a sampling clock, and a digital signal of 8 bits per sample (b7 to b0) is obtained.

The PLL circuit 158 includes a series circuit of five D flip-flops 222 to 226 for sequentially delaying only the most significant bit (MSB) b7 of the digital signal output from the A / D converter 221. D
Output signals D0 to D4 of flip-flops 222 to 226
And a pattern discriminating circuit 227 for discriminating whether or not there is a specific pattern and outputting a pattern discriminating signal PD. The clock signals C output from the voltage controlled oscillator 212 are respectively supplied to the D flip-flops 222 to 226.
LK is supplied as an operation clock.

During reproduction, the magneto-optical disk 111 located at the front end of the temperature region 17 (see FIG. 7E) higher than the Curie temperature Ts of the switching layer 12 at a certain time.
Moves so as to be located at the rear end of the temperature region 17 after a certain period of time. As described above, since the domain wall movement also occurs from the rear of the temperature region 17, a signal due to the domain wall movement from behind is superimposed as a ghost signal on the reproduction signal due to the domain wall movement from the front. As described above, the reproduced signal SMO 'is converted into the binary signal S2,
When the clock signal CLK is obtained using the edge information of No. 2, the edge phase of the binarized signal S2 fluctuates depending on the pattern of the ghost signal included in the reproduction signal SMO ', and a stable clock signal CLK can be obtained. It will be difficult.

As described above, the ghost signal for changing the edge phase of the binarized signal S2 has a magnetic domain of a predetermined length or more continuous at a portion corresponding to the rear end of the temperature area 17 of the magneto-optical disk 111. Occurs when formed. The patterns of the signals D0 to D4 correspond to the recording magnetic domain patterns of the portion of the magneto-optical disk 111 located near the rear end of the temperature area 17 after a predetermined time. here,
The certain time is a moving time of a predetermined portion of the magneto-optical disk 111 from the front end to the rear end of the temperature area 17.

As described above, the pattern determining circuit 22
In step 7, it is determined whether or not the recording magnetic domain pattern of the portion of the magneto-optical disk 111 corresponding to the rear end of the temperature area 17 after a predetermined time is a pattern for generating a ghost signal for changing the edge phase of the binarized signal S2. Is determined. Therefore, the pattern determination circuit 227 outputs the signals [D0, D1, D
2, D3, D4] is [1,1,0,0, x] or [x, 1,1,0,0] or [0,0,1,1, x]
Or, when [x, 0, 0, 1, 1] (x is 0 or 1), the recording magnetic domain pattern of the portion of the magneto-optical disk 111 corresponding to the rear end of the temperature area 17 after a predetermined time is It is determined that the pattern is a pattern that generates a ghost signal that changes the edge phase of the binarized signal S2, the output pattern determination signal PD is set to 1, and one of the signals [D0, D
[1, D2, D3, D4] are other patterns, the output pattern determination signal PD is set to 0.

The PLL circuit 158 has a gate circuit 215 for controlling whether or not to supply the edge detection signal PN output from the edge detector 211 to the phase comparator 213.
And a delay circuit 228 that delays the pattern discrimination signal PD output from the pattern discrimination circuit 227 and supplies it to the gate circuit 213 as a gate control signal.

In this case, the gate circuit 215 supplies the edge detection signal PN from the edge detector 211 to the phase comparator 213 when the gate control signal is 0, and outputs the edge when the gate control signal is 1 The configuration is such that the edge detection signal PN from the detector 211 is not supplied to the phase comparator 213.

In the delay circuit 228, as described above, the recording magnetic domain pattern of the portion of the magneto-optical disk 111 corresponding to the rear end of the temperature area 17 changes the edge phase of the binary signal S2 after a certain period of time by the pattern determination circuit 227. The timing of one pattern discrimination signal PD, which is determined and output as a pattern for generating a ghost signal to be generated, is detected by the edge detector 211 from the above-described binarized signal S2 of the reproduction signal SMO 'after a predetermined time. The delay is adjusted to match the detection timing of the edge detection signal PN. This allows
Although the reproduced signal SMO 'after a predetermined time includes a ghost signal for changing the edge phase of the binarized signal S2, the edge detection signal PN is not supplied to the phase comparator 213.

In the PLL circuit 158 having such a configuration,
The oscillation frequency of the voltage controlled oscillator 212 is always controlled so that the phase error signal output from the phase comparator 213 approaches zero. Therefore, the clock signal CLK whose rising edge is synchronized with the rising edge and the falling edge of the binarized signal S2 can be obtained from the voltage controlled oscillator 212. In the PLL circuit 158, when the phase of the edge detection signal PN output from the edge detector 211 is affected by the ghost signal, the edge detection signal PN is transmitted to the phase comparator 213 by the operation of the gate circuit 215. Since the phase control signal is not supplied, the phase comparator 213 does not output an erroneous phase error signal PE due to the influence of the ghost signal.
2, a more stable clock signal CLK can be obtained.

The operation of the PLL circuit 158 shown in FIG. 2 for removing the influence of the ghost signal will be further described with reference to the timing charts of FIGS. 3A to 3I.

FIG. 3A shows a reproduced signal S having undergone waveform equalization processing.
MO ', and a ghost signal corresponding to the portion indicated by the arrow Q1 is generated in the portion indicated by the arrow Q2 after a predetermined time T0. Corresponding to the reproduced signal SMO ', the binarized signal S2 and the edge detection signal PN are obtained as shown in FIGS. 3B and 3C, respectively. 3A to 3C, the broken lines indicate the states of the respective signals when there is no ghost signal. FIG. 3D shows the clock signal CLK.

As described above, when the ghost signal exists in the portion indicated by the arrow Q2 of the reproduced signal SMO ', the edge detection signal PN of the rising edge of the binary signal S2 corresponding to the portion.
The phase of (PN0) fluctuates as shown in FIG. 3C. Therefore, if this edge detection signal PN is supplied to the phase comparator 213, the phase error signal PE fluctuates as shown in FIG. 3E, and it becomes impossible to obtain a stable clock signal CLK from the voltage controlled oscillator 212. .

In the present embodiment, a D flip-flop 22 is applied to a reproduced signal SMO 'as shown in FIG.
Signals D0 to D4 output from 2 to 226 change as shown in FIG. 3G, and a pattern determination signal PD is obtained from pattern determination circuit 227 as shown in FIG. 3H. And
This pattern discrimination signal PD is supplied to the delay circuit 228 in FIG.
Is supplied to the gate circuit 215 as a gate control signal after being delayed as shown in FIG. In this case, the edge detection signal PN0 whose phase is changed due to the influence of the ghost signal
At the detection timing (shown in FIG. 3C), the gate control signal becomes 1, and this edge detection signal PN0 is
13 is not supplied. Therefore, the phase comparator 213
Is stable as shown in FIG. 3F, and a stable clock signal CLK not affected by the ghost signal can be obtained from the voltage controlled oscillator 212.

In the configuration of the PLL circuit 158 shown in FIG. 2, a gate circuit 215 is inserted between the edge detector 211 and the phase comparator 213. This gate circuit 215 is connected to the phase comparator 213 and the loop. A configuration in which the phase error signal PE obtained from the phase comparator 213 corresponding to the edge detection signal PN whose phase is affected by the ghost signal is not supplied to the loop filter 214 may be provided between the loop filter 214 and the filter 214. Good.

Returning to FIG. 2, the data detection circuit 15
Reference numeral 9 denotes a D flip-flop 231 as a synchronizing unit for obtaining a binary signal S2 'synchronized with the clock signal CLK from the binary signal S2, and the binary signal (NRZI data)
S2 'is demodulated and reproduced data Dp as NRZ data
And a demodulation unit 232 that obtains In this case, the binary signal S2 is supplied to the data terminal D of the D flip-flop 231 and its clock terminal is connected to the PLL circuit 1
The clock signal CLK output from 58 is supplied.
The binary signal S synchronized with the clock signal CLK is output from the non-inverting output terminal Q of the D flip-flop 231.
2 'is derived.

Next, the magneto-optical disk drive 10 shown in FIG.
The operation of 0 will be described. When a data write command is supplied from the host computer to the system controller 151, data writing (recording) is performed. In this case, the data received by the SCSI 153 and the data buffer 15
The ECC circuit 154 adds an error correction code to the write data from the host computer stored in 2 and the data modulator 155 converts the data into RLL modulation bits and NRZI data. .

The recording data Dr as NRZI data is supplied from the data modulator 155 to the magnetic head driver 116, and the recording data Dr is recorded in a data area as a target position on the magneto-optical disk 111. In this case, the recording film of the magneto-optical disk 111 (the magnetic recording medium 1)
A light beam (laser light) 16 having a high power such that the memory layer 13 of (0) reaches the Curie temperature is applied to the optical head 117.
From the optical disk 111. The light beam may be modulated in a pulsed manner in synchronization with the channel bit of the recording data Dr. At the same time, the magnetic head 115
Generates a magnetic field whose polarity is inverted in accordance with the recording data Dr of 1, 0, and this magnetic field is applied to the recording film of the magneto-optical disk 111. Thereby, the magneto-optical disk 1
In the memory layer 13 of the 11 recording film, a magnetic domain whose polarity is inverted according to the recording data Dr is recorded.

When a data read command is supplied from the host computer to the system controller 151, data reading (reproduction) is performed. In this case, the reproduction signal SMO is reproduced by the optical head 117 from the data area as the target position of the magneto-optical disk 111. The reproduced signal SMO is subjected to waveform equalization processing by the waveform equalizing circuit 156, and is converted into a reproduced signal SMO 'by the binarizing circuit 1
57. The binarized signal S2 output from the binarization circuit 157 is supplied to a data detection circuit 159, and the reproduced data (RLL) is generated from the binarized signal S2 using the clock signal CLK obtained by the PLL circuit 158.
The modulation bit) Dp is detected.

The reproduced data Dp is subjected to demodulation processing by the data demodulator 160, and further to the ECC circuit 154.
And error correction is performed to obtain read data. The read data is temporarily stored in the data buffer 152, and thereafter transmitted to the host computer via the SCSI 153 at a predetermined timing.

As described above, in the present embodiment, in the PLL circuit 158 (see FIG. 2), when the phase of the edge detection signal PN is affected by the ghost signal included in the reproduction signal SMO ', By not supplying the edge detection signal PN to the phase comparator 213, the oscillation frequency of the voltage controlled oscillator 212 is not controlled by the phase error signal PE related to the edge detection signal PN. Therefore, a stable reproduced clock signal that is not affected by the ghost signal can be obtained from the PLL circuit 158, and the processing in the data detection circuit 159 can be performed well.

In the above embodiment, in the PLL circuit 158, the phase of the edge detection signal PN is
When affected by the ghost signal included in MO ',
Although the oscillation frequency of the voltage controlled oscillator 212 is not controlled by the phase error signal PE relating to the edge detection signal PN, the phase of the edge detection signal PN is affected by the ghost signal included in the reproduction signal SMO '. The phase error signal PE related to the edge detection signal PN
May be corrected to obtain a stable clock signal CLK from the voltage controlled oscillator 212.

FIG. 4 shows a PLL circuit 15 in that case.
8 'is shown. In FIG. 4, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The PLL circuit 158 'includes a pattern detection circuit 241 for detecting patterns of output signals D0 to D4 of the five D flip-flops 222 to 226 and a pattern detection signal PS from the pattern detection circuit 241 for a predetermined time. And a delay circuit 242 that delays only the delay time. Here, the certain time is, as described above, a moving time of a predetermined portion of the magneto-optical disk 111 from the front end to the rear end of the temperature region 17 (see FIG. 7E).

The patterns of the signals D0 to D4 correspond to the recording magnetic domain patterns of the portion of the magneto-optical disk 111 located near the rear end of the temperature area 17 after a certain time as described above. Therefore, the reproduction signal SM after a certain period of time
O 'includes a ghost signal corresponding to this pattern. The pattern detection signal PS is supplied to the delay circuit 24.
By delaying by a fixed time at 2, the pattern indicated by the delayed pattern detection signal PS 'and the phase error signal PE obtained from the phase detector 213 correspond one-to-one.

The PLL circuit 158 'is provided with a delay circuit 2
Based on the pattern detection signal PS 'output from the P.42 and the phase error signal PE output from the phase comparator 213, as shown in FIG.
.., A pattern for outputting the average value PEa of the phase error signal PE corresponding to the pattern detection signal PS ′, a correlation recording section 243 of the phase error signal, and a memory for storing the average value PEa0, PEa1, PEa2,. The phase error signal PE obtained from the phase comparator 213 using the average value PEa
And a phase error correction unit 216 that corrects the error and supplies the resultant to the loop filter 214.

In this case, the average value of the phase error signal for each pattern corresponds to the phase variation of the edge detection signal PN due to the ghost signal corresponding to each pattern. Therefore, the average value PEa of the phase error signal PE corresponding to the pattern detection signal PS 'is output from the correlation recording unit 243.
Is output, and the phase error signal PE is corrected with the average value PEa and supplied to the loop filter 214, whereby a stable clock signal CLK not affected by the ghost signal can be obtained from the voltage controlled oscillator 212.

With reference to the timing charts of FIGS. 6A to 6I, the operation of removing the influence of the ghost signal in the PLL circuit 158 'shown in FIG. 4 will be further described. FIG. 6A shows a reproduced signal SMO 'that has been subjected to the waveform equalization process, and a ghost signal corresponding to a portion indicated by an arrow Q1 is generated in a portion indicated by an arrow Q2 after a predetermined time T0. In response to the reproduced signal SMO ', the binarized signal S
2. The edge detection signal PN is obtained as shown in FIGS. 6B and 6C, respectively. 6A to 6C, the broken lines indicate the states of the respective signals when there is no ghost signal. FIG. 6D shows the clock signal CLK.

As described above, when the ghost signal is present in the portion indicated by the arrow Q2 of the reproduced signal SMO ', the edge detection signal PN of the rising edge of the binary signal S2 corresponding to that portion.
The phase of (PN0) fluctuates as shown in FIG. 6C. Therefore, if the edge detection signal PN is supplied to the phase comparator 213, the phase error signal PE fluctuates as shown in FIG. 6E, and it becomes impossible to obtain a stable clock signal CLK from the voltage controlled oscillator 212. .

In the PLL circuit 158 'shown in FIG.
In response to the reproduced signal SMO 'as shown in FIG. 6A, the signals D0 to D4 output from the D flip-flops 222 to 226 change as shown in FIG. 6G. Then, the pattern detection signal PS output from the pattern detection circuit 241 (FIG. 6H
Is supplied to the delay circuit 242, and the delay circuit 2
42, the pattern detection signal P delayed by a certain time
S ′ (shown in FIG. 6I) is obtained. The pattern indicated by the pattern detection signal PS 'and the phase error signal PE (shown in FIG. 6E) obtained from the phase detector 213 correspond one-to-one.

Therefore, by supplying the pattern detection signal PS ′ and the phase error signal PE to the correlation recording section 243, the average value of the phase error signal PE for each pattern can be stored in the correlation recording section 243. The average value of the phase error signal PE for each pattern corresponds to the phase variation of the edge detection signal PN due to the ghost signal corresponding to each pattern. Accordingly, the phase error signal PE corresponding to the pattern detection signal PS 'is output from the correlation recording section 243.
Is output, and the phase error signal PE is corrected with the average value PEa, so that the corrected phase error signal PE is one in which the influence of the ghost signal has been removed as shown in FIG. 6F. Therefore, the voltage controlled oscillator 2
12, a stable clock signal CLK not affected by the ghost signal can be obtained.

[0061]

According to the data reproducing apparatus and method of the present invention, when the phase of the edge detection signal of the binary signal is affected by the ghost signal included in the reproduced signal,
The oscillation frequency of the oscillator is not controlled by the phase error signal related to the edge detection signal, or the influence of the ghost signal is removed from the phase error signal related to the edge detection signal. Therefore, a stable reproduced clock signal that is not affected by the ghost signal can be obtained, and the data detection processing and the like can be performed favorably.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a magneto-optical disk device as an embodiment.

FIG. 2 is a block diagram showing a configuration example of a PLL circuit and a data detection circuit of a reproduction system of the magneto-optical disk device.

FIG. 3 is a timing chart for explaining an operation of removing an influence of a ghost signal in a PLL circuit.

FIG. 4 is a block diagram showing another configuration example of the PLL circuit and the data detection circuit of the reproduction system of the magneto-optical disk device.

FIG. 5 is a diagram illustrating a recording example of correlation recording of a pattern and a phase error signal.

FIG. 6 is a timing chart for explaining an operation of removing an influence of a ghost signal in a PLL circuit (another example).

FIG. 7 is a diagram for explaining a DWDD method.

[Explanation of symbols]

10 ... magneto-optical recording medium, 11 ... moving layer, 12
..Switching layer, 13 ... memory layer, 14 ...
Atomic spin direction, 15 ... domain wall, 16 ... light beam for reproduction, 16P ... light beam spot, 17 ...
A temperature region higher than the Curie temperature Ts of the switching layer, 100... A DWDD type magneto-optical disk device,
111: magneto-optical disk, 115: magnetic head for generating an external magnetic field, 117: optical head, 141
..Servo controller, 151 ... system controller, 154 ... ECC circuit, 155 ... data modulator, 156 ... waveform equalization circuit, 157 ... binarization circuit, 158 ... PLL Circuit, 159: Data detection circuit, 160: Data demodulator, 211: Edge detector, 212: Voltage controlled oscillator, 213 ...
.Phase comparator, 214 ... Loop filter, 215
..Gate circuits, 216... Phase error correction units, 22
1 ... A / D converter, 222 to 226,231
..D flip-flops, 227: pattern discriminating circuits, 228, 242, delay circuits, 232, demodulating units, 241, pattern detecting circuits

Claims (11)

[Claims] At least a moving layer, a switching layer,
A memory layer is formed by laminating in this order, the memory layer is made of a perpendicular magnetic film, and the moving layer is made of a perpendicular magnetic film having a smaller domain wall coercive force and a larger domain wall mobility than the memory layer, The switching layer is a data reproducing apparatus that handles a magneto-optical recording medium including a magnetic layer having a lower Curie temperature than the moving layer and the memory layer, and moves a light beam relative to the magneto-optical recording medium. While irradiating from the side of the moving layer, a temperature distribution having a gradient with respect to the moving direction of the spot of the light beam and having a temperature region higher than at least the Curie temperature of the switching layer is formed on the magneto-optical recording medium. By moving the magnetic domain wall formed in the moving layer, a signal reproduction that obtains a reproduction signal corresponding to a change in the polarization plane of the reflected light of the light beam is performed. Means, clock reproducing means for obtaining a reproduced clock signal based on the reproduced signal, and reproduction processing means for performing processing using the reproduced clock signal on the reproduced signal to obtain reproduced data; The means comprises: a binarization circuit for converting the reproduction signal into a binarization signal; an edge detector for detecting at least one of rising and falling edges of the binarization signal; and outputting the reproduction clock signal. An oscillator, a phase comparator that compares a phase of an edge detection signal from the edge detector and the phase of the reproduction clock signal to obtain a phase error signal for controlling an oscillation frequency of the oscillator, and a phase of the edge detection signal, Ghost included in the reproduction signal due to the movement of the domain wall on the rear end side of the temperature region higher than the Curie temperature of the switching layer Determining means for determining whether or not the signal is affected by the signal; and oscillating the oscillator by the phase error signal relating to the edge detection signal whose phase is determined to be affected by the ghost signal by the determining means. A data reproducing apparatus comprising: a control suppressing unit that suppresses frequency control. 2. The method according to claim 1, wherein the determining unit determines that the magnetic domain having a predetermined length or more is continuously formed in a portion corresponding to a rear end of the temperature region of the magneto-optical recording medium. The data reproducing apparatus according to claim 1, wherein it is determined that the phase of the detection signal is affected by the ghost signal. 3. The method according to claim 1, wherein the determining unit is configured to determine the edge of the edge of the magneto-optical recording medium based on a pattern of the reproduction signal a predetermined time corresponding to a moving time of a predetermined portion of the magneto-optical recording medium from a front end to a rear end of the temperature area. 3. The data reproducing apparatus according to claim 2, wherein it is determined whether or not the phase of the detection signal is affected by the ghost signal. 4. The apparatus according to claim 1, wherein the control suppressing unit does not supply the edge detection signal determined to be affected by the ghost signal to the phase comparator. 2. The data reproducing device according to 1. 5. The oscillator according to claim 1, wherein the control suppressing means outputs the phase error signal obtained from the phase detector in response to the edge detection signal determined to be affected by the ghost signal. 2. The data reproducing apparatus according to claim 1, wherein the data is not supplied to the data reproducing apparatus. 6. At least a moving layer, a switching layer,
A memory layer is formed by laminating in this order, the memory layer is made of a perpendicular magnetic film, and the moving layer is made of a perpendicular magnetic film having a smaller domain wall coercive force and a larger domain wall mobility than the memory layer, The switching layer is a data reproducing method for handling a magneto-optical recording medium comprising a magnetic layer having a lower Curie temperature than the moving layer and the memory layer, wherein a light beam is moved relative to the magneto-optical recording medium. While irradiating from the side of the moving layer, a temperature distribution having a gradient with respect to the moving direction of the spot of the light beam and having a temperature region higher than at least the Curie temperature of the switching layer is formed on the magneto-optical recording medium. Moving the domain wall formed in the moving layer to obtain a reproduction signal corresponding to a change in the polarization plane of the reflected light of the light beam. Obtaining a reproduction clock signal based on the reproduction signal; and performing processing using the reproduction clock signal on the reproduction signal to obtain reproduction data. The step of obtaining the reproduction clock signal includes: A first step of converting the reproduction signal into a binarized signal; and a second step of obtaining an edge detection signal that detects at least one of a rising edge and a falling edge of the binarized signal.
A third step of comparing the phases of the edge detection signal and the reproduced clock signal to obtain a phase error signal; and a fourth step of controlling the frequency of the reproduced clock signal by the phase error signal. It is determined whether or not the phase of the edge detection signal is affected by a ghost signal included in the reproduction signal due to the movement of the domain wall on the rear end side of the temperature region higher than the Curie temperature of the switching layer. In the fifth step, the control of the frequency of the reproduction clock signal by the phase error signal related to the edge detection signal whose phase is determined to be affected by the ghost signal in the fifth step is suppressed. A data reproducing method, comprising: 7. In the fifth step, when magnetic domains of a predetermined length or more are continuously formed in a portion corresponding to a rear end side of the temperature region of the magneto-optical recording medium, 7. The data reproducing method according to claim 6, wherein it is determined that the phase of the edge detection signal is affected by the ghost signal. 8. At least a moving layer, a switching layer,
A memory layer is formed by laminating in this order, the memory layer is made of a perpendicular magnetic film, and the moving layer is made of a perpendicular magnetic film having a smaller domain wall coercive force and a larger domain wall mobility than the memory layer, The switching layer is a data reproducing apparatus that handles a magneto-optical recording medium including a magnetic layer having a lower Curie temperature than the moving layer and the memory layer, and moves a light beam relative to the magneto-optical recording medium. While irradiating from the side of the moving layer, a temperature distribution having a gradient with respect to the moving direction of the spot of the light beam and having a temperature region higher than at least the Curie temperature of the switching layer is formed on the magneto-optical recording medium. By moving the magnetic domain wall formed in the moving layer, a signal reproduction that obtains a reproduction signal corresponding to a change in the polarization plane of the reflected light of the light beam is performed. Means, clock reproducing means for obtaining a reproduced clock signal based on the reproduced signal, and reproduction processing means for performing processing using the reproduced clock signal on the reproduced signal to obtain reproduced data; The means comprises: a binarization circuit for converting the reproduction signal into a binarization signal; an edge detector for detecting at least one of rising and falling edges of the binarization signal; and outputting the reproduction clock signal. An oscillator, a phase comparator for comparing a phase of an edge detection signal from the edge detector and the reproduced clock signal to obtain a phase error signal for controlling an oscillation frequency of the oscillator, Pattern detection means for detecting a recording magnetic domain pattern of the magneto-optical recording medium in a portion corresponding to a rear end side of the high temperature region; For each pattern detected by the pattern detection means, for each pattern detected by the phase comparator, storage means for storing the average value of the phase error signal in the storage unit, and for the pattern detected by the pattern detection means from the storage unit And an error correction means for reading the average value corresponding to the phase error signal and correcting the phase error signal obtained by the phase comparator based on the average value. 9. The pattern detection means according to claim 1, wherein said pattern detection means is configured to detect the pattern of the reproduction signal by a predetermined time corresponding to a moving time of a predetermined portion of the magneto-optical recording medium from a front end to a rear end of the temperature area. 9. The data reproducing apparatus according to claim 8, wherein a recording magnetic domain pattern is detected. 10. At least a moving layer, a switching layer, and a memory layer are stacked in this order, the memory layer is formed of a perpendicular magnetization film, and the moving layer is relatively domain wall coercive as compared with the memory layer. A data reproducing method for a magneto-optical recording medium comprising a magnetic layer having a lower Curie temperature than the moving layer and the memory layer, wherein the switching layer comprises a perpendicular magnetic film having a small domain wall mobility. Irradiation is performed from the side of the moving layer while relatively moving with respect to the magneto-optical recording medium, and has a gradient with respect to the moving direction of the spot of the light beam on the magneto-optical recording medium and at least the switching layer By forming a temperature distribution having a temperature region higher than the Curie temperature, the domain wall formed in the moving layer is moved, and the light beam Obtaining a reproduction signal corresponding to the change in the polarization plane of the emitted light; obtaining a reproduction clock signal based on the reproduction signal; performing processing using the reproduction clock signal on the reproduction signal to obtain reproduction data; Obtaining the reproduced clock signal, wherein the first step of converting the reproduced signal into a binarized signal; and detecting at least one of rising and falling edges of the binarized signal. Second to obtain edge detection signal
A third step of comparing the phases of the edge detection signal and the reproduced clock signal to obtain a phase error signal; and a fourth step of controlling the frequency of the reproduced clock signal by the phase error signal. A fifth step of detecting a recording magnetic domain pattern of the magneto-optical recording medium in a portion corresponding to a rear end side of a temperature region higher than the Curie temperature of the switching layer; and each pattern detected in the fifth step. A sixth step of storing, in a storage unit, an average value of the phase error signal obtained in the third step for each time, and the average value corresponding to a pattern detected in the fifth step from the storage unit And a seventh step of correcting the phase error signal obtained in the third step based on the average value. Data reproduction method to. 11. The method according to claim 5, wherein in the fifth step, a pattern of the reproduction signal before a predetermined time corresponding to a moving time of a predetermined portion of the magneto-optical recording medium from a front end to a rear end of the temperature region is determined. 11. The data reproducing method according to claim 10, wherein the recording magnetic domain pattern is detected.