JPH06176430A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To cancel an edge shift component caused by inter-code interference at the time of reproducing information and to accurately reproduce the recorded information by correcting an edge position of a recording signal in accordance with an edge shift and recording it. CONSTITUTION:A recording pattern of an object of correction is detected out of recording patterns of an information signal to be recorded by a pattern detecting circuit 18. Then, an edge shift is corrected by a timing adjusting circuit 19 in adjustment of timing of the recording pattern. Then the width of an information pit is corrected in accordance with an edge shift amt. at the recording stage of the information and can be recorded. Consequently, even when a reproducing signal level is lowered by inter-code interference at the time of reproducing the information, and an edge shift takes place at the time of binarization, since the edge shift component is corrected and recorded, reproducing is performed under the state of cancellation of just the edge shift component, and hence the recorded information can accurately be reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus for recording / reproducing information by utilizing the magneto-optical effect of light and magnetism.

[0002]

2. Description of the Related Art Conventionally, as a recording method of this type of magneto-optical recording / reproducing apparatus, information is obtained by irradiating a magneto-optical recording medium with a light beam whose intensity is modulated according to a recording signal while applying a magnetic field in a fixed direction. And a magnetic field modulation method in which information is recorded by applying a magnetic field modulated according to a recording signal while irradiating a light beam having a constant intensity. In any of the recording methods, it is required to increase the recording density, and as one of them, it has been attempted to increase the information recording density by recording a pit having a diameter smaller than the spot diameter of the semiconductor laser of the light source. As information recording modes, pit position recording (recording between marks) that gives information meaning to the center position of the recording pit, and pit edge recording (information recording at edge positions before and after the recording pit) There is a mark length record). Since the pit edge recording has a recording density about twice as high as that of the pit position recording, the pit edge recording has recently been shifting to the pit edge recording.

By the way, when a pit smaller than the spot diameter of the semiconductor laser is recorded and the pit is reproduced by using the same laser spot as described above, a phenomenon called intersymbol interference occurs. This intersymbol interference will be described below with reference to FIG.
It will be described based on 1. In FIG. 11A, P1 to P3 are recording pits, and SP is a reproducing light spot irradiated on the recording pits. The recording pits P1 and P3 are upwardly magnetized, and the recording pit P2 is downwardly magnetized. Here, the light spot SP is applied to an area including the edges of the recording pits P1 and P3 centered on the recording pit P2. Figure 11
FIG. 11B shows a reproduction signal when reproduction is performed based on the reflected light of the reproduction light spot SP in the state of FIG. Ideally, the reproduced signal of A as shown by the broken line is,
As described above, there are three recording spots SP1 to SP3 in the light spot SP, and these pits are reproduced at the same time. Therefore, as shown by the solid line B, in comparison with the ideal reproduction signal A, Therefore, the signal is reproduced in a state where the amplitude level is low and the signal waveform is generally small. Such a phenomenon is a phenomenon called intersymbol interference.

The reproduced signal thus obtained is binarized at the slice level shown in FIG. 11B. However, as described above, the reproduced signal becomes small as a whole due to intersymbol interference. As indicated by B in c), the edge of the binarized signal shifts inward as compared with the binarized signal A when the ideal reproduction signal is binarized. This is a phenomenon generally called edge shift. Since the edge of the binarized signal corresponds to the edge of the recording pit, such an edge shift causes a significant problem to prevent accurate reproduction of information in pit edge recording in which the edge position of the recording pit also has the meaning of information. Was becoming.

A similar phenomenon is observed in a magnetic disk device (hard disk device etc.), which will be described with reference to FIG. FIG. 12A shows a recording pattern, and FIG. 12B.
Is a recording pulse for writing this recording pattern on the magnetic disk. Further, FIG. 12C shows a reproduction signal obtained by reproducing the information thus recorded by the magnetic head, and the peak of the reproduction signal waveform is shifted to the outside of the edge of the recording pulse at the actual recording position. ing. This is the peak shift of a magnetic disk. When the recording pits "1" indicating magnetization reversal are adjacent to each other, this peak shift causes mutual interference between these recording pits, and the magnetic pressure reversal points are relatively opposite to each other as shown in FIG. 12C. It is caused by the cause of deviation. Therefore, if a reproduction pulse is generated based on the obtained reproduction signal, the width of the reproduction pulse becomes wider than the width of the recording pulse as shown in FIG. 12E, and the information cannot be reproduced accurately. . The peak shift direction of the magnetic disk is opposite to the edge shift direction of the magneto-optical disk.

Therefore, in the magnetic disk apparatus, in order to correct this pattern peak, recording compensation is performed by recording a short pit in advance at the time of recording. That is, since the shift amount of the peak shift is determined by the mutual relation between the long pattern and the short pattern, the method of determining the compensation shift amount by the recording compensation table as shown in FIG. 13 and determining the width of the pit to be recorded is adopted. Has been. In the recording compensation table shown in FIG. 13, n is the current bit.
The number of “0” s between “1” and the previous bit “1”, m is the number of “0s” between the current bit “1” and the subsequent bit “1”, and the relationship between n and m The compensation shift amount of any one of A to D is obtained from A to D.

FIG. 14 is a diagram showing a specific example of a recording signal compensating circuit for generating a recording signal according to the recording compensation table. Reference numerals 401 to 403 are delay lines and 404 is a selecting circuit. The delay amounts of the delay lines 401 to 403 are determined corresponding to B, C and D in the recording compensation table of FIG. Also, A of the recording compensation table is input to the selection circuit 404 as the output of the recording signal. The selection circuit 404 adjusts the recording timing by selecting one from among them according to the recording compensation table,
The peak shift is corrected.

Specifically, the operation of the recording signal compensation circuit is shown in FIG.
It will be described based on. FIG. 15A shows a 1-7 modulated recording pattern, and FIG. 15B shows a pulse train obtained by converting this into an NRZ code. 15C to 15E are signals input to the selection circuit 404 shown in FIG. 14, which are signals delayed by a predetermined time by the delay lines 401 to 403, respectively. Further, FIG. 15 (f) shows the output signal selected by the selection circuit 404 according to the recording compensation table. If the output of the delay line is selected based on this, a pulse train as shown in FIG. 15 (h) is obtained. . Furthermore,
When this is NRZI converted, it becomes a signal as shown in FIG. On the other hand, FIG. 15 (g) is a diagram showing a signal after NRZI conversion when recording compensation is not performed. Figure 1
Comparing 5 (g) with (i), it can be seen that (i) is shorter than 2 (g) by 2T and is longer than the other (g), and recording compensation is performed. In this way, the width of the recording pulse is adjusted and the peak shift is corrected.

[0009]

Although the above description has been concerned with the peak shift compensating circuit in the magnetic disk device, the application of this to the edge shift of the magneto-optical disk device is as described above. It was difficult because it was the opposite. Therefore, conventionally, a new edge shift compensating device for eliminating the edge shift in the magneto-optical disk device has been desired.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magneto-optical recording / reproducing apparatus capable of effectively reproducing recorded information by effectively correcting edge shift caused by intersymbol interference. It is intended.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording / reproducing apparatus for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field. Means for detecting a recording pattern to be corrected from among the recording patterns, and edge positions before and after the recording signal are determined based on the relationship between the recording pattern and the recording patterns before and after the recording pattern according to the pattern detection signal of the detecting means. And a means for making corrections.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a magneto-optical recording / reproducing apparatus of the present invention. In FIG.
Reference numeral 1 is a magneto-optical disk which is an information recording medium, and 2 is a spindle motor for rotating the magneto-optical disk 1 at a predetermined speed. A floating magnetic head 3 for generating a magnetic field modulated according to a recording signal is arranged on the upper surface of the magneto-optical disk 1, and the floating magnetic head 1 is arranged on the lower surface thereof.
The optical head 4 is arranged so as to face the. The optical head 4 irradiates a light beam for recording / reproducing information and detects reflected light thereof to record / reproduce information, and its configuration is as follows.

First, 5 is a semiconductor laser which is a light source, 6 is a polarization beam splitter for separating a laser light flux of the semiconductor laser 5 from an irradiation light flux on the magneto-optical disk 1 and a reflected light flux from the magneto-optical disk 1, and 7 Is an objective lens for narrowing the laser light flux of the semiconductor laser 5 to form a minute light spot on the magneto-optical disk 1. The objective lens 7 is driven by an actuator 8 in the tracking direction and the focusing direction, and tracking control and focusing control are performed. That is, a tracking control circuit and a focusing control circuit (not shown) detect a tracking error signal and a focusing error signal, and by controlling the actuator 8 based on these error signals, the light spot of the semiconductor laser 5 is focused on the medium surface. Focusing control for adjusting the light spot and tracking control for causing the light spot to follow the information track are performed. Reference numeral 9 is a polarization beam splitter for separating the reflected light beam from the magneto-optical disk 1 into two light beams.
Is an optical sensor for detecting each of the separated light beams. The optical head 4 is configured by integrating the above optical elements.

The detection signals of the optical sensors 10 and 11 are differentially detected by the differential amplifier 12 and reproduced as a magneto-optical signal. Reference numeral 13 is a waveform equalization circuit for reducing intersymbol interference of the obtained reproduction signal, and 14 is binarization for converting the reproduction signal after waveform equalization into a digital signal by binarizing it at a predetermined slice level. Circuit. Reference numeral 15 is a data separator for synchronizing the binarized data, which includes a time base generator that extracts the binarized data or generates a reference signal. Reference numeral 16 denotes a CPU for controlling the entire apparatus as a whole, which modulates the recording data transmitted from the outside by a predetermined modulation method, and the data separator 1
5 is also provided with a function of demodulating the data sent from No. 5 to generate reproduced data.

Reference numeral 17 is a recording compensation circuit for correcting the edge shift caused by the above-mentioned intersymbol interference, and is composed of a pattern detection circuit 18 and a timing adjustment circuit 19. The pattern detection circuit 18 is a detection circuit for detecting the recording pattern to be corrected from the recording patterns of the information signal to be recorded, and the timing adjustment circuit 19
Is a correction circuit for adjusting the timing of the recording pattern to correct the edge shift. The specific configuration of the timing adjustment circuit 19 and the specific correction operation of the recording compensation circuit 17 including the timing adjustment circuit 19 will be described later in detail. Reference numeral 20 denotes a magnetic head driver for driving the levitation magnetic head 3, which drives the levitation magnetic head 3 so as to switch the current direction of a coil wound around the magnetic core of the levitation magnetic head 3 in accordance with a signal output from the recording compensation circuit 17. . As a result, the floating magnetic head 3 generates a magnetic field modulated according to the recording signal and applies it to the magneto-optical disk 1 as a recording bias magnetic field.

FIG. 2 is a block diagram showing a concrete example of the timing adjustment circuit 19 in the recording compensation circuit 17.
In the figure, 101 is a one-shot pulse generator for narrowing the width of the input recording signal for a predetermined time. Here, the one-shot pulse generator 101 is connected to the CPU 1
A 6 to 1-7 RLL-modulated NRZ code recording signal is input. 102a to 102c are programmable delay lines (hereinafter abbreviated as PDL) for delaying the output of the one-shot pulse generator 101 for a predetermined time. The delay amount of the PDL 102a is set to advance by τ ₁ with respect to the output of the PDL 102b, and the PDL 102c is delayed by τ _{1 with} respect to the reference. Of course, this delay amount does not have to be equal. Reference numeral 103 denotes a multiplexer for selecting one of the outputs of the PDLs 102a to 102c according to the detection signal of the pattern detection circuit 18 described above according to the recording compensation table, and 104 denotes the NRZ of the output of the multiplexer 103.
It is a JK flip-flop for further converting the code to the NRZI code.

FIG. 3 is a diagram showing a recording compensation table provided in the multiplexer 103. As is clear from FIG. 3, when the i-th recording pattern is 2T and the preceding i−1-th recording pattern is other than 2T, the edge position of “1” of the recording signal of the NRZ code is set to τ. ₁
(Ns) shifts forward. Further, the i-th recording pattern is 2T, and the i + 1-th recording pattern after that is 2T.
If it is other than T, the edge position of "1" of the recording signal is shifted backward by τ ₁ (ns). If the 2T pattern is continuous, no correction is performed. In this way, the recording position is compensated for by correcting the edge positions on both sides of the recording signal by the amount of the edge shift during reproduction. Here, it is assumed that the degree of intersymbol interference is relatively small and the amplitude of the reproduced signal of the pattern other than 2T is almost saturated, and therefore the correction is performed only for the 2T pattern. Of course, the correction amount τ
₁ is a value determined according to the edge shift amount of the 2T pattern.

Next, the specific operation of the first embodiment will be described with reference to FIG. In addition, (a) to (h) shown in FIG.
Corresponds to FIGS. 4A to 4H. FIG. 4A shows a CPU
The recording signal of the NRZ code is input from 16 to the one-shot pulse generator 101 of the timing adjusting circuit 19. Here, recording patterns such as 2T, 4T, 3T, 2T, 2T ... Are shown. This recording signal has its pulse width narrowed for a predetermined time by the one-shot pulse generator 101 and then sent to the PDLs 102a to 102c. In the PDLs 102a to 102c, as shown in FIG.
As shown in (f), each input signal is delayed by the set time. As described above, the output of the PDL 102a is set to advance by τ ₁ and the output of the PDL 102c is set to be delayed by τ ₁ based on the output of the PDL 102b. The output signals of these PDLs 102a to 102c are sent to the multiplexer 103.

On the other hand, the pattern detection circuit 18 outputs a pattern detection signal as shown in FIGS. 4B and 4C to the multiplexer 103. FIG. 4B is a signal in which the front edge (2T-Lead) of the 2T pattern is detected, and FIG.
(C) is the trailing edge of the 2T pattern (2T-Trail)
Is a signal for detecting. The multiplexer 103 selects one of the outputs of the PDLs 102a to 102c according to the recording compensation table shown in FIG. 3 according to these pattern detection signals. Specifically, first, when the front edge of the first 2T pattern of the recording signal of FIG. 4A is detected,
Since the multiplexer 103 follows the recording compensation table of FIG. 3 and the pattern before the 2T pattern is other than the 2T pattern, the recording signal edge position is set to τ as shown in FIG.
The output of the PDL 102a in FIG. 4D is selected so as to move forward by ₁ . Next, when the trailing edge of the 2T pattern is detected, since the subsequent pattern is 4T, the multiplexer 103 selects the output of the PDL 102c of FIG. 4 (f) so as to delay the edge position of the recording signal by τ ₁ .
Further, since the multiplexer 103 does not need to perform recording compensation in the next 3T recording pattern, the PDL1 of FIG.
The output of 02b is selected and the front edge of the next 2T pattern is 3T, so the output advanced by τ _{1 in} FIG. 4D is selected. Also, at the trailing edge of the next 2T pattern, the next pattern is a 2T pattern and the same 2T pattern
Since the pattern is continuous, recording compensation is not performed.
Select the output of (e). Thus multiplexer 10
3 sequentially selects the outputs of the PDLs 102a to 102c according to the recording compensation table as shown in FIG.

The selection signal of the multiplexer 103 is output to the JK flip-flop 104 and converted into the NRZI code as shown in FIG. Figure 4 for comparison
(I) shows the NRZI code in the case where the recording compensation is not performed. As is clear from the comparison with this, since the preceding and following patterns are other than 2T in the first 2T pattern, the leading and trailing edges of the recording signal are shown. It can be seen that the pulse width of the recording signal spreads to both sides by shifting τ ₁ back and forth. Further, in the next 3T, since it is 2T after that, it is understood that the trailing edge is shifted forward by τ ₁ and the pulse width is narrowed. NR of JK flip-flop 104
The ZI code recording signal is output to the magnetic head driver 20 shown in FIG. 1, and the flying magnetic head 3 is driven according to the NRZI code recording signal. As a result, the floating magnetic head 3 generates a magnetic field modulated according to the recording signal and applies it to the magneto-optical disk 1. On the other hand, the magneto-optical disk 1 is irradiated with a light beam of a constant intensity from the semiconductor laser 5 in the optical head 4, and a series of information is recorded on the information track by the irradiation of this light beam and the application of the modulation magnetic field. .

As described above, in this embodiment, the recording pattern that needs to be corrected (here, 2T is selected from the recording patterns).
Pattern) is detected, and the edge positions on both sides of the recording signal are corrected according to the relationship between the pattern and the preceding and following patterns according to this detection signal, so the width of the information pit is used as the edge shift amount at the information recording stage. It can be corrected and recorded accordingly. Therefore, even if the reproduction signal level decreases due to intersymbol interference during information reproduction and edge shift occurs during binarization, the edge shift is corrected and recorded as described above. Are just offset by the edge shift, and the recorded information can be reproduced accurately. This has a great effect particularly in pit edge recording. In the embodiment, since the programmable delay line capable of changing the delay amount by digital data is used as the delay line, the ZCAV method in which the recording frequency is changed for each zone of the magneto-optical disk 1 to record information. When used in the above device, if the delay amount τ ₁ is adjusted to an appropriate value for each zone, optimum recording compensation can be performed in any zone.

Next, a second embodiment of the present invention will be described. This embodiment is an example suitable when the degree of intersymbol interference is relatively larger than that of the above embodiments and the reproduced signals of patterns other than the 2T and 3T patterns are almost saturated. At this time, the relationship between the reproduction signal amplitudes of the 2T and 3T patterns is 2
T <3T. Therefore, in this embodiment, the 2T and 3T patterns are to be corrected, and the pattern detection circuit 18 has a 2T pattern.
In addition to the pattern, a circuit for detecting the leading edge and the trailing edge of the 3T pattern is provided.

FIG. 5 shows the recording compensation table of the second embodiment. In this embodiment, as shown in FIG.
The second recording pattern is 2T, and the preceding i−1th is 3T
If so, the edge position of the recording signal “1” of the NRZ code is τ
₁ (ns) is shifted by the previous, the edge position of the recording signal "1" if more than 4T is shifted to the front by τ ₂ (ns). If the i-th recording pattern is 2T and the i + 1-th subsequent pattern is 3T, the edge position of the recording signal “1” is shifted backward by τ ₁ (ns), and if 4T or more, the recording signal “1” is changed. Shift the edge position backward by τ ₂ . Further, if the i-th is the 3T pattern and the preceding i−1-th is 4T or more, the edge position of the recording signal “1” is τ ₁
(Ns) shifts forward, i + after 3T pattern
If the first is 4T or more, the edge position of the recording signal “1” is shifted backward by τ ₁ (ns). The relation between τ ₁ and τ ₂ is τ ₂ > τ ₁ > 0, and the correction amount of τ ₁ and τ ₂ is 2T, 3
It is determined according to the edge shift amount of the T pattern.
If the 2T pattern is continuous or the 3T pattern is continuous, the edge shift is not compensated.

FIG. 6 is a block diagram showing the timing adjusting circuit of the second embodiment. In FIG. 6, 102a-1
Reference numeral 02e is a programmable delay line (abbreviated as PDL) for delaying the signal output from the one-shot pulse generator 101 by a set time. Among them, the PDLs 102a to 102c are the delay lines for outputting the signals of the reference time described in the first embodiment and the delay time of ± τ ₁ with respect to the reference time.
Reference numerals d and 102e are delay lines for outputting a signal having a delay time of ± τ ₂ with respect to the reference. Therefore, the relationship between the overall delay times of these PDLs is PD
With L102b as the reference, PDL102a has τ ₁ , PD
L102d advances by τ ₂ , and PDL 102c advances by τ ₁ , P
DL 102e is set to be delayed by τ ₂ .
Further, the pattern detection circuit 18 detects the front edge and the rear edge of the 3T pattern in addition to the 2T pattern, and these four pattern detection signals are input to the multiplexer 103. In FIG. 6, the detection signal of the front edge of the 2T pattern is 2T-Lead, and the detection signal of the rear edge is 2T-T.
rail, 3T-L leading edge detection signal of 3T pattern
The detection signal at the edge and the trailing edge is shown as 3T-Trail. Reference numeral 104 is a JK flip-flop for converting the output signal of the multiplexer 103 into an NRZI code.

Next, the operation of the second embodiment will be described with reference to FIG. Note that (a) to (i) shown in FIG.
This corresponds to the signals (a) to (i). First, FIG. 7A shows a recording signal of the NRZ code sent from the CPU 16,
(B) to (e) are pattern detection signals output from the pattern detection circuit 18. 7T of which is 2T
The leading edge detection signal of the pattern, FIG. 7 (c) is the trailing edge detection signal of the 2T pattern, FIG. 7 (d) is the leading edge detection signal of the 3T pattern, and FIG. 7 (e) is the trailing edge detection signal of the 3T pattern. . Further, FIGS. 7F to 7I show PDL1.
02a to 102e are output signals, and (f) is the PDL 102.
output signal of d, (g) output signal of PDL102a,
(H) is the output signal of the PDL 102b, (i) is the PDL1
02c is an output signal, and (j) is an output signal of the PDL 102e. These output signals are output to the multiplexer 103.

When the front edge detection signal of the 2T pattern shown in FIG.
One of the five PDLs is selected according to the recording compensation table shown in FIG. Here, since the pattern before the 2T pattern is 4T or more, the output signal of the PDL 102d in FIG. 7 (f) is set to advance the recording signal by τ ₂ as shown in FIG. 7 (k) according to the recording compensation table. select. Next, when the trailing edge detection signal of the 2T pattern of FIG. 7C is input, the subsequent pattern is 4T, so that the output signal of the PDL 102e of FIG. 7J is delayed to delay the recording signal by τ ₂ . Select. Furthermore, FIG.
When the front edge detection signal of the 3T pattern of (d) is input, the multiplexer 103 has the previous pattern of 4T, so that the recording signal is advanced by τ _{1 in} FIG.
The output signal of the PDL 102a of (g) is selected. Subsequently, when the trailing edge detection signal of the 3T pattern of FIG. 7E is input, the subsequent pattern is 2T, so that the recording signal is delayed by τ ₁ to the PDL 10 of FIG. 7I.
2c output signal is selected.

Further, when the front edge of the next 2T pattern is detected, it means that the 2T pattern is continuous at this time.
The output signal of the PDL 102b of FIG. 7 (h) is selected so as not to perform recording compensation. Since the subsequent 2T pattern trailing edge is a 3T pattern, the recording signal is delayed by τ _{1 in} FIG. 7 (i). Select the output signal. Thus, the multiplexer 103 is 2T, as shown in FIG.
Each time the 3T pattern detection signal is received, the PDL output signal is sequentially selected according to the recording compensation table. The output signal of the multiplexer 103 is the JK flip-flop 1
It is output to 04 and converted into NRZI code as shown in FIG. As apparent from FIG. 7 (l), the first 2T
Since the pattern is a 4T pattern before and after the pattern, it can be seen that the edge positions on both sides of the recording signal are each shifted by τ ₂ and the pulse width is corrected by the amount of edge shift. In the next 3T pattern, 4T and 2 are placed before and after that.
Since it is a T pattern, it can be seen that the edge position of the recording signal is shifted back and forth by τ ₁ , and this is also corrected according to the edge shift.

Thus, also in this embodiment, 2T, 3
By detecting the T pattern and correcting the edge positions of the front end and the rear end of the recording signal based on the relationship with the patterns before and after the T pattern, the edge of the binarized signal caused by intersymbol interference at the time of reproduction is exactly the same as in the above embodiment. The shift can be corrected and the information can be reproduced accurately. When used in an MCAV device, the delay amount of each PDL may be changed corresponding to each zone.

Next, a third embodiment of the present invention will be described. It is generally known that in magneto-optical recording, the quality of a reproduced signal differs depending on the polarity (magnetization direction) of a recording pit. That is, in FIG. 8A, recording pits of 2T pattern of + polarity (corresponding to “1” of recording signal) and recording pits of − polarity (corresponding to “0” of recording signal) are recorded before and after the recording pit. FIG. 8B shows a state in which recording pits of a −polarity 2T pattern and recording pits of a positive polarity are recorded before and after the recording pits. However, when a pattern having different polarities is reproduced, intersymbol interference occurs. As a result, the amount of edge shift varies depending on the polarity of the recording pattern. Therefore, in this embodiment, the difference in the edge shift amount caused by the difference in the polarities of the recording pits is also corrected.
Note that here, the degree of intersymbol interference is relatively small, 2
It is assumed that the amplitudes of the reproduced signals other than the T pattern are almost saturated, so that the correction target is only the 2T pattern as in the embodiment of FIG.

FIG. 9 is a diagram showing a recording compensation table used in the third embodiment. FIG. 9A is a + side recording compensation table used for correcting the + T 2T pattern as described above.
FIG. 9B is a − side recording compensation table used for correcting a 2T pattern of polarity. Since the recording compensation table of FIGS. 9A and 9B targets the 2T pattern for correction, it is basically the same as the recording compensation table of FIG. 3 shown in the first embodiment. That is, the i-th is + 2T pattern (or -2T pattern), and the preceding i-1th is 2T pattern.
If it is other than the pattern, the edge position of the recording signal is shifted forward by τ ₁ (or τ ₁ ′), and if the i + 1-th pattern thereafter is other than 2T, then τ ₁ (or τ ₁
The edge position of the recording signal is shifted backward by ₁ ').
However, when the 2T pattern is continuous, the recording compensation is not performed. Here, FIG. 9 (a) ± τ ₁ the shift amount of the edge of the recording signal in, although the FIG. 9 (b) in ± tau ₁ ', +
If polarity of the pit, - because the edge shift amount as compared to the higher polarity of the shift amount is ± tau ₁ accordingly, also - the shift amount in accordance with the edge shift amount in polarity ± tau ₁ 'and setting Has been done.

FIG. 10 is a diagram showing a timing adjusting circuit of the third embodiment. Although not particularly shown in FIG. 10,
A determination circuit for determining the polarity of the recording pattern, that is, the polarity of the pit corresponding to the recording pattern is provided, and the polarity determination signal (Pole) is output to the multiplexer 103. As the polarity discriminating circuit, for example, NRZ
The I code is converted so that the polarity is inverted when "1" of the NRZ code comes. Therefore, if the initial state of the conversion is known, the rest can be composed of only a binary counter. Also,
A 2T pattern detection signal to be corrected is input from the pattern detection circuit 18 to the multiplexer 103.

Reference numerals 102a to 102c denote PDLs (programmable delay lines) provided in correspondence with the + side recording compensation table of FIG. 9A. When the output of the PDL 102b is used as a reference, the output of the PDL 102a is τ _1. The output of the PDL 102c is set to be advanced and delayed by τ ₁ . Further, 102a 'and 102c' are shown in FIG.
P provided corresponding to the minus side recording compensation table of (b)
It is DL. The delay amounts + τ ₁ ′ and −τ ₁ ′ of the PDLs 102a ′ and 102c ′ are set to be slightly smaller than the + polarity + τ ₁ and −τ ₁ depending on the shift amount of the −polarity pit as described above. Of course, PDL102a based on the output of PDL102b 'output of tau _1' advanced by, PDL102c 'output of tau _1' are set as delayed.

The output signals of the above five PDLs are output to the multiplexer 103, and the multiplexer 103 selectively outputs one of the output signals of the PDL according to the recording detection table according to the pattern detection signal. in this case,
The multiplexer 103 selects the recording compensation table of FIGS. 9A and 9B according to the polarity determination signal from the polarity determination circuit described above. That is, if it is determined that the 2T pattern corresponds to the + polarity, the multiplexer 103 operates as shown in FIG.
When the + side recording compensation table of (a) is determined to correspond to the − polarity, the PDL output signal is selected according to the − side recording compensation table of FIG. 9B. As a result, the correction amount of the edge position of the recording signal can be controlled according to the polarity of the pit to be recorded, and even a slight difference in the edge shift amount due to the difference in the pit polarity can be corrected. Therefore, in the third embodiment, not only the edge shift is corrected but also the difference in the edge shift amount due to the difference in the polarities of the recording pits can be corrected, and the recording information can be more accurately compared with the first and second embodiments. Can be played.

Although the correction target is the 2T pattern in the third embodiment, the 2T and 3T patterns may be corrected as in the second embodiment when the degree of intersymbol interference increases. In that case, both polarity determination circuits for 2T and 3T patterns are required. Further, in the first to third embodiments, the example in which the recording signal of the 1-7 RLL modulation code is corrected has been shown, but it goes without saying that the present invention can be applied to other modulation methods. Furthermore, the recording pattern to be corrected is 2
The correction amount is not limited to the T and 3T patterns, and may be determined according to the degree of intersymbol interference. In that case, the correction amount may be determined based on the relationship between the patterns before and after them.

[0035]

As described above, according to the present invention, by correcting the edge position of the recording signal according to the edge shift and recording, the edge shift caused by the intersymbol interference at the time of reproducing the information can be canceled out. There is an effect that the recorded information can be accurately reproduced regardless of intersymbol interference.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a magneto-optical recording / reproducing apparatus of the present invention.

FIG. 2 is a block diagram specifically showing the timing adjustment circuit of the embodiment of FIG.

3 is a diagram showing a recording compensation table used in the timing adjustment circuit of FIG.

FIG. 4 is a time chart showing an edge shift correction operation of the timing adjustment circuit of FIG.

FIG. 5 is a diagram showing a recording compensation table used in a second embodiment of the present invention.

FIG. 6 is a block diagram showing a timing adjustment circuit according to a second exemplary embodiment of the present invention.

FIG. 7 is a time chart showing the edge shift correction operation of the embodiment of FIG.

FIG. 8 is a diagram showing + polar 2T patterns and −polar 2T patterns having different polarities.

FIG. 9 is a diagram showing a recording compensation table used in a third embodiment of the present invention.

FIG. 10 is a diagram showing a timing adjustment circuit according to a third exemplary embodiment of the present invention.

FIG. 11 is a diagram for explaining intersymbol interference.

FIG. 12 is a diagram for explaining a peak shift that occurs in the magnetic disk device.

FIG. 13 is a diagram showing a compensation table used for peak shift compensation.

FIG. 14 is a block diagram showing an example of a peak shift compensation circuit of a magnetic disk device.

15 is a time chart showing the peak shift compensation operation of FIG.

[Explanation of symbols]

1 magneto-optical disk 3 floating magnetic head 4 optical head 5 semiconductor laser 14 binarization circuit 16 CPU 17 recording compensation circuit 18 pattern detection circuit 19 timing adjustment circuit 101 one-shot pulse generator 102a to 102e PDL (programmable delay line) 103 multiplexer 104 JK flip flop

Claims (3)

[Claims] 1. In a magneto-optical recording / reproducing apparatus for recording information by irradiating a magneto-optical recording medium with a light beam and applying a magnetic field, a recording pattern to be corrected from among recording patterns of an information signal to be recorded. And means for correcting the edge positions before and after the recording signal based on the relationship between the recording pattern and the recording patterns before and after the recording pattern according to the pattern detection signal of the detecting means. A magneto-optical recording / reproducing device. 2. The correction means includes a recording compensation table in which a correction amount is determined for an edge position before and after a recording signal based on a relationship between a recording pattern to be corrected and recording patterns before and after the recording pattern, and information to be recorded. It is characterized by comprising a plurality of delay means for delaying each signal for a predetermined time, and a selection means for selecting the output of the corresponding delay means from the plurality of delay means according to the recording compensation table. The magneto-optical recording / reproducing apparatus according to claim 1. 3. A recording compensation table in which a means for determining the polarity of a pit corresponding to a recording pattern detected by the detecting means and a correction amount of an edge position of a recording signal corresponding to the polarity of the pit are set. 2. The magneto-optical recording / reproducing apparatus according to claim 1, further comprising: and a correction amount of the edge position of the recording signal is selected from the recording compensation table according to the determination result of the determining means.