JP2717794B2 - Signal decoding method for optical disk of sample servo system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal decoding method for an optical disk reproduction signal capable of stably detecting and decoding a reproduction signal of a sample servo type optical disk.

[Prior Art] Optical disk devices are widely used as large-capacity data storage devices capable of high-density recording. The recording method of the optical disk is to record pits in a spiral or concentric manner on the recording film of the optical disk with a laser beam focused to about 1 μm in diameter. In order to record a pit by scanning a light beam on an optical disk at a high track density, it is necessary to apply a tracking servo and a focus servo for adjusting the focus of the light beam to a target position on the recording film. There are two methods for performing tracking servo and focus servo. The first method is a continuous servo method using a guide groove, and the second method is a sample servo method using a wobble pit. FIG. 5 shows a wobble pit recording format of a conventional sample servo system shown in DP9171-2, which is a draft of an ISO international standard for optical discs. (1) shows one track, and one track is divided into 32 sectors. (A)
Is the data format of a certain track viewed in sector units. The user data capacity of one sector is 512 bytes. This method uses a CA in which the disc always rotates at a constant speed.
Because of the V scheme, each track has the same number of sectors. (B) is a data format showing a part of a sector in an enlarged manner. The data portion is divided into 18-byte units called segments, and one sector is composed of 43 segments. The first segment of each sector is called a header, and the address information of the sector records the preformat.
(C) is an enlarged view of (b) showing the internal structure of a segment. One segment is composed of a gap (42) and a data (43). A wobble pit (44) and a clock pit (45) are recorded in the gap (42). The wobble pit (44) consists of two pits,
Each pit is slightly offset from the center of the track to the right and left with respect to the traveling direction of the light beam. That is, if the preceding pit is shifted to the right with respect to the traveling direction of the light beam, the following pit is shifted to the left. FIG.
FIG. 6 is a block diagram for creating a recording / reproducing clock and data when the signal format of FIG. 5 is used. FIG. 7 is an explanatory diagram of the waveform. The optical sensor current is I / V converted and the reproduced voltage waveform (a) is input to the terminal (20). Next, the pit is detected by the detector (21), and a detection signal (b) is obtained. The detection signal (b) is obtained by the gate circuit (23) that detects only the clock pit signal by utilizing the characteristics of the time interval between the clock pit and the wobble pit and the time interval between successive clock pits. . From the detected clock pit, a recording / reproducing clock (referred to as recording / reproducing CK) (d) is created by a phase / lock loop (PLL) circuit (24). Also, a switching signal (e) for the gap block and the data block is obtained. By this recording / playback CK, the recording data input to the terminal (26) is digitally modulated by the modulator (27), and
0) and (31) send modulation clock and modulation data,
The laser recording amplifier records data on the disk only when the switching signal is a data block. As a recording method, an RZ recording method (recording waveform (g)) in which modulation data (f) is recorded with a fixed-length pulse at bit “1” and bit “1”
NRZI recording method whose polarity is reversed (recording waveform (i))
There is. In the RZ method, the Gaussian isolated reproduction waveform (h) and its level tip are differentially detected from each reproduction waveform to obtain a detection signal (k). On the other hand, in the NRZI method, the reproduced waveform (j) is 2
The value level is sliced, and this edge information is used as a detection signal (k).
Becomes The detection signal (k) is subjected to data decoding by recording / playback ck (d), and a decoder (25) outputs a decoding clock (d) and decoded data (1) to terminals (28) and (29). . As described above, in the sample servo type optical disc, the recording pit is preformatted and the recording pit is preformatted so that the recording data is created and the reproduction data is detected. There is an advantage that a self-clocking capability such as a length-limited code is not required, and a problem such as a clock loss which is a problem in the self-clocking hardly occurs. On the other hand, the self-clocking capability cannot be performed because the data portion is divided by the servo byte. Also, if the phase of the reproduction detection signal and the phase of the recording / playback ck deviate, there is no room for decoding and a detection error occurs. This phenomenon will be described with reference to FIG. FIG. 8 (a) shows the recording / playback ck, and FIG. 8 (b) shows the RZ recording signal (c)
Is an NRZI recording signal. When the detection signal is detected at the center of the decoding window (Tw) of the recording / playback ck, the width of the detected decoding window is +/-
-With Tw / 2, detection error is least likely to occur. Next, a detection signal of the optical disk device will be considered. Conventionally, an RZ recording method has been used in a hole-recordable optical disk. When the recording power is normal, the recording signal phase and the reproduction signal phase are relatively unlikely to be displaced on the disk, and the reproduction detection signal can be reproduced almost in a normal phase as shown in FIG. However, the laser power of the optical disk changes its current / power characteristics with respect to temperature, and a phase shift occurs due to a shift in the power characteristics and a change in the power characteristics of the inner and outer circumferences of the disk. This effect is very significant in a rewritable magneto-optical disk. In magneto-optical recording, when a laser power is applied to a disk, if the polarity of the magnetic field exceeds a predetermined temperature (curie temperature) or more,
The magnetic film is magnetized to the polarity of the applied magnetic field, and the magnetization polarity when cooled to a Curie temperature or lower by the rotation of the disk after the stop of power application remains. Therefore, the residual magnetization pattern is temporally shifted with respect to the applied power, and the phase of the reproduction detection signal advances with respect to the recording / reproducing ck during reproduction. In order to shorten the rotation waiting time in the erasing and recording modes, which is recently required for the conventional magneto-optical disk. A system having an immediate overwrite function with a magneto-optical disk has been proposed. The most feasible method is the magnetic field modulation overwrite method. In this method, when recording, the laser power is set to DC recording power, the magnetic field polarity is changed by a recording modulation signal, and erasing and recording are performed in the same mode. This enables overwriting. At this time, by performing magnetic field modulation by the NRZI recording method, it is possible to realize a significant improvement in recording density as compared with the RZ recording method. The reason for this is that when recording is possible with the same minimum pit length, the recording density of NRZI recording is twice as high as that of RZ recording. However, it has been reported that when the magnetic field modulation method is employed in a sample servo optical disk, the phase of the reproduction detection signal with respect to recording / playback ck changes significantly.

References K. Yamada et al, “Optical Storage Technology and
Application ", SPIE Proceeding Vol, 899-24, 12-15, Ja
n.1988 At this time, the reproduced signal becomes as shown in (d) with respect to the recording / reproducing ck phase, and the detection signal (e) becomes Δ with respect to the recording signal phase.
T goes ahead. The value of ΔT is very large with respect to the window width of the recording / playback ck.
It was difficult to perform data recording / reproducing using the recording / reproducing ck. [Problems to be Solved by the Invention] The decoding method using the signal format of the conventional sample servo type optical disk is as described above. Recording play ck
Is used to decode the reproduction detection signal, and the phase shift between the reproduction detection signal and the recording / playback ck cannot be corrected. In particular, in the magnetic field modulation overwrite recording method, a detection error occurs due to the phase shift, and it is difficult to provide an optical disk with a high-speed data recording / reproducing function like a magnetic disk. The present invention has been made in order to solve the above-described problems. In a sample servo type optical disk apparatus, a write-once disk, a magneto-optical disk, and a magnetic field modulation overwrite recording of a magneto-optical disk. The present invention also provides a novel signal decoding method that can eliminate the phase shift between the recording / playback ck and the detection signal by circuit processing.

[Means for solving the problem]

In the signal decoding method for an optical disk of the sample servo system according to the present invention, a data recording / reproducing sector in which a plurality of segments each composed of a pair of a gap portion and a data portion in which a clock pit is preformatted is formed, A header signal indicating the track information of the sector is present in the first segment of the sector, and a fixed pattern used to correct the phase shift of the recording / reproducing clock at the time of decoding is recorded in the subsequent segment. A signal decoding method for an optical disk of a sample servo method, wherein the clock pit is detected during reproduction, and a plurality of delay signals having different delay amounts are created from the detection signal using a delay circuit,
When each of the plurality of delay signals is in phase with the signal obtained from the fixed pattern recorded in the segment at the time of recording, the delay signal is output to each counter that operates so as to have the maximum count value. A delay signal that minimizes a phase shift between the delay signal and a signal obtained from the fixed pattern is selected based on the delay signal and decoded by the same decoder.

[Action]

In the signal decoding method for an optical disk of the sample servo system according to the present invention, a clock pit is detected during recording, a recording / reproducing ck for recording / reproducing data is created, and a header signal is detected based on the recording / reproducing ck. Based on this detection signal, a data area of a preformatted recording sector is set, a fixed pattern is recorded in a segment area prior to data, and then data is recorded. During playback, recording / playback ck
Thus, the header signal is detected, the data area of the sector is set, and in the fixed pattern area, the reproduction detection signal is corrected for the phase shift amount using a tapped delay line circuit or the like, and the corrected correction is performed. The reproduction signal is detected and decoded using the detection signal. On the other hand, the reproduction signal in the preformat area is decoded by a detection signal which does not cause the phase shift and does not pass through the delay circuit. By switching these two detection signals in each area, it is possible to use the same decoder to configure an optical disk apparatus free from errors.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a reproduced signal decoding circuit which is a specific example of the signal decoding method according to the present invention. The difference from the conventional circuit of FIG. 6 is that the output signal of the reproduction detector (21) is
Before the signal is input to the phase corrector (22), the signal is input to a phase corrector (22) to correct the decoding phase shift between the recording / playback ck and the reproduction detection signal, and the phase shift is corrected. FIG. 2 shows an example of a phase shift correction circuit. FIG. 3 is an explanatory diagram thereof. The reproduction detection signal is input to the terminal (50), and becomes a constant pulse width by the pulse generator (51) having a constant width, and is input to a delay line with taps (DL line) (52) with a delay amount of a minimum tap interval. ,
Obtain signals 01-08 delayed only by each one. In FIG. 3, in the signal format (a) in the track, the data portion of each segment following the header in the data portion of each segment and the gap portion (b) is a recordable / reproducible area, and the first segment portion thereof. Has a fixed pattern recorded therein. By reproducing the preformatted header signal and decoding it by recording / reproducing ck, the timing signal (c) indicating the preformatted area and the timing signal (d) of the fixed pattern area following the header are output to each terminal (61) and Entered in (55). The recording signal of the fixed pattern area is, for example, “001001... 00100” as shown in (e).
Pattern. During reproduction, the recording pattern of the decoded RZ signal in the fixed pattern area is known, and a recording pattern (g) having the same phase as the recording signal is input to the terminal (54). Second
In the figure, each of the delayed reproduction detection signals 01 to 08 is inputted to a counter (53) of which the clock and the clear terminal are on the same line. As this counter, for example, a synchronous counter such as SN74163N is used, and each of 01 to 08 is ET and EP.
Assume that it is connected to the terminal. This counter is incremented only when the clock signal (g) is input and when 01 to 08 are at the high level. CL terminal input (inverted signal of (d))
Is at a low level outside the fixed pattern area.
The clock signal (g) operates to reset this counter outside the fixed pattern area, and the counter of the output line where the phase of each of the delay line outputs (j) to (k) and the clock signal (g) matches is the maximum. Operate to have a count value. The determination circuit (56) is a logic circuit for determining, for example, the maximum count input lines 01 to 08 of each counter output value, and outputs a 3-bit code indicating the input line. This judgment code is latched by the latch circuit (57) at the end of the fixed pattern area, and the selector (5)
According to 9), a DL line output signal that minimizes the phase error is output. On the other hand, the reproduction detection signal of the pre-pit portion is shifted from the normal phase by passing through such a correction circuit. Therefore, the detection signal is switched to the input signal to the DL line by the switching signal (c) to the selector (60), and is transmitted to the decoder from the terminal (62). According to the above description, the phase of the recording / playback ck can be corrected using the phase corrector described above by using the reproduction detection signal recorded in the fixed pattern area, and the data area following the fixed pattern area can be corrected. It is understood that the reproduction detection signal is similarly corrected. By setting the tap delay line to be used to 5 ns, the phase correction error of the recording / reproducing data of 5 Mbps, (2-7) RLLC code is ± 5 nsec, which is sufficient for the decoding window (= ± 50 nsec). I can make it smaller. FIG. 4 is a diagram showing an example of a signal format according to the present invention. Data is recorded in a sector structure as in the conventional example, and FIG. 4 (a) is a diagram corresponding to FIG. 5 (b).
(1) shows a data format in one track. (1) is divided into 5-byte segments (2), and each segment is composed of 4-byte data (9) and 1-byte gap (10). Two pits, a wobbled pit (4) and a non-wobbled clock pit (5), are recorded in the gap (10). The wobble pit has a different wobble direction for each segment. Wobble bit (4),
(8), the bit size is shifted about 1/4 to the right from the track center when viewed from the light beam traveling direction, and the wobble pit (6) is from the track center when viewed from the light beam traveling direction. It is shifted about 1/4 of the bit size to the left. In this signal format, tracking servo can be performed in the same manner as in the conventional example. In the conventional example, a new tracking error signal is obtained every 16 bytes. In the signal format of FIG. 4, a new tracking error signal is obtained every 5 bytes. Can be increased by a factor of four. Further, the phase jitter of the PLL for creating the recording / playback CK becomes stable as the number of phase comparison signals increases. (7) is a header provided in the track (1), which is a track address data section having a length of 5 bytes like the segment section, and has an internal structure including a gap section (10) and a data section. However, all are recorded in pre-pits, and a code corresponding to the address of the track is recorded in the data portion. The data portion in the segment following the header is a recordable / reproducible area, and a fixed pattern is recorded in the first segment portion. By using this signal format, the phase shift between the recording / playback ck and the reproduction detection signal during reproduction can be corrected by circuit processing. The fixed pattern in this format may be any pattern. Instead of the delay line, the detection signal can be delayed using a high-frequency clock signal or a semiconductor delay element. The accuracy can be improved by reducing the delay amount of the tapped delay line. The second judgment circuit
By using a statistical processing algorithm in the determination logic of FIG. 56, a determination error due to a disk defect or the like can be removed, and the determination ability can be improved.

〔The invention's effect〕

As described above, the use of the signal decoding method of the sample servo optical disc of the present invention causes a problem when performing magneto-optical recording, RZ / NRZI recording, and magnetic field modulation overwrite recording on the sample servo optical disc. A recording / reproducing clock created from preformatted clock pits, and a phase shift between a reproduction detection signal and a clock signal obtained from a fixed pattern written at the time of recording, and a plurality of different delay amounts obtained from the recording / reproducing clock. When the phase with the delay signal is matched, it is output to each counter that operates so as to have the maximum count value, and based on the output of these counters, the recording / reproducing signal with the minimum phase shift is obtained, so that the phase shift can be easily performed. Can be corrected,
The capacity and transfer rate of the optical disk device can be improved. The hardware for obtaining this effect is also constituted by a logic circuit, and is easily implemented in an LSI, and has high practical value.

[Brief description of the drawings]

FIG. 1 is an embodiment of a block diagram of a decoding circuit for a reproduction detection signal which embodies a signal decoding system according to the present invention. Second
FIG. 1 shows an embodiment of a phase corrector which is the core of the object of the present invention. FIG. 3 is an explanatory diagram of FIG. FIG.
This is an example of a signal format according to the present invention. FIG. 5 is an example of a conventional signal format. FIG. 6 is an example of a conventional recording / reproducing data generating circuit, and FIG. 7 is an explanatory waveform diagram of FIG. FIG. 8 is an explanatory diagram of a recording / reproducing clock and a decoding phase of a detection signal. In the figure, 21 ... detector, 22 ... phase corrector, 23 ...
Gate circuit, 24 PLL circuit, 25 decoder, 27 modulator, 51 pulse generator, 52 delay line with tap,
53 ... Counter unit, 56 ... Judgment circuit, 57 ... D latch,
59, 60... Selectors, where the same numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Masaharu Ogawa 8-1-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Inside the Applied Equipment Research Laboratory Mitsubishi Electric Corporation (72) Kyosuke Yoshimoto 8-1-1, Tsukaguchi Honmachi, Amagasaki City, Hyogo Prefecture No. 1 Mitsubishi Electric Corporation Applied Equipment Laboratory (72) Inventor Masafumi Ototake 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Mitsubishi Electric Corporation Applied Equipment Laboratory (56) References JP-A 64-79955 (JP, A) JP-A 64-1167 (JP, A) JP-A 1-155535 (JP, A)

Claims (1)

(57) [Claims] 1. A data recording / reproducing sector in which a plurality of segments each formed of a pair of a gap portion and a data portion in which a clock pit is preformatted constitutes a continuous data recording / reproducing sector, and track information of the sector is recorded in a leading segment of the sector. In the signal decoding method of the sample servo optical disk, a fixed pattern used to correct a phase shift of a recording / reproducing clock at the time of decoding is recorded in a segment subsequent to the header signal shown in FIG. Then, the clock pit was detected during reproduction, a plurality of delay signals having different delay amounts were created from the detection signal using a delay circuit, and each of the plurality of delay signals was recorded in the segment at the time of recording. When the phase with the signal obtained from the fixed pattern matches, output to each counter that operates so as to have the maximum count value. A signal of an optical disk of a sample servo system, wherein a delay signal that minimizes a phase shift between the delay signal and a signal obtained from a fixed pattern is selected based on an output of a counter and decoded by the same decoder. Decryption method.