JPH01223670A - Optical disk signal format - Google Patents

Abstract

PURPOSE:To set the phase of a recording and reproducing clock and a reproducing detecting signal to a phase being optimum for decoding by writing a fixed pattern at the time recording in a leading segment area continued from a header area brought to pre-format. CONSTITUTION:The inside of a data format 1 in one track is segmented to segments 2 of 4.5-byte unit, and the inside of each segment consists of data 9 of 4-bytes and a gap part 6 for a wobble pit of 0.5-byte. In a gap part 4, wobble pits are recorded as 5, 6 and 8. A header part 7 provided in the track 1 has length of 4.5-bytes in the same way as the segment part 2 in a track address data part and all recorded by a pre-pit, a data part in the segment continued from the header part 7 is a recordable and reproduceable area and a fixed pattern is used for a first segment part. By using this signal format, the phase shift of a recording and reproducing cK and a reproducing detecting signal can be corrected by a circuit processing at the time of reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sample servo system and an optical disc signal format that allows stable detection of a reproduced signal of an optical disc.

[Prior Art] Optical disk devices are widely used as large-capacity data storage devices capable of high-density recording.

The recording method for optical discs is to record pits in a spiral or concentric pattern on the recording film of an optical disc using a laser beam focused to a diameter of about 1 um. In order to record pits by scanning a light beam on an optical disk at a high track density, it is necessary to apply tracking servo and focus servo to focus the light beam on a desired 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 guide grooves, and the second method is a sample servo method using wobble pits.

Figure 5 is a draft of the ISO international standard for optical discs, DP
This is a conventional sample servo type wobble pit recording format shown in No. 9171-2. (1) indicates one track, and one track is partitioned into 32 sectors. (2L) is the data format of a certain track in units of sectors. ■The user data capacity of a sector is 512 bytes. Since this system is a CAV system in which the disk always rotates at a constant rotation speed, each track has the same number of sectors.

(b) is a data format showing an enlarged part of a sector, where the data portion is divided into 18-byte units called segments, and a sector (2) consists of 43 segments. The first segment of each sector is called a header, and the address information of the sector is recorded in a preformat. (
C) is a diagram showing the internal structure of the segment by further enlarging (B), and the l segment consists of a gap part (42) and a data part (43). A wobble pit (44) and a clock pit (45) are recorded in the gap part (42). The wobble pit (44) consists of two pits, and each pit is slightly shifted to the right and left with respect to the traveling direction of the light beam from the center of the track. In other words, if the front pit is shifted to the right with respect to the traveling direction of the light beam, the rear pit is shifted to the left. 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 light sensor current is I
/V converted and the reproduced voltage waveform (λ) is input to the terminal (20). Next, the pit tip is detected by the detector (21) and a detection signal (b) is obtained. The detection signal (b) is obtained by a gate circuit (23) that detects only the clock pit signal by utilizing the characteristics of the time interval between clock pits and wobble pits and the time interval of consecutive clock pits, and obtains the detection signal (c). . From the detected clock pits, a phase lock loop (PLL) circuit (24) creates a recording/reproducing clock (referred to as recording/reproducing CK) (d). Also, the gap section and data section switching signal (e)
I get it. When the recording/playback is OK, the recording data input to the terminal (26) is digitally modulated by the modulator (27), and the modulated clock and modulated data are reversely output to the terminals (30) and (31), and the laser recording medium is Therefore, only when the switching signal is the data portion, it is recorded on the disk.

As a recording method, pits are recorded for modulated data (f).
There is an RZ recording method (recording waveform (g),) in which recording is performed with a fixed length pulse at 〃, and an NRZI recording method (recording waveform (i)) in which the polarity is reversed at pit 1〉. In the RZ method, each reproduced waveform is a Gaussian isolated reproduced waveform (h)
Then, the tip of the level is differentially detected to obtain a detection signal (k). On the other hand, in the NRZI method, the reproduced waveform (j) is sliced into 200 million levels, and this edge information becomes the detection signal (k). The detection signal (k) is subjected to data decoding by the recording/reproducing ck (d), and is sent to the terminal (28) by the decoder (25).
) and (29) are the decoded clock (d) and decoded data (1
) is output. As explained above, in sample servo type optical discs, the recording and reproducing clocks are preformatted clock pits to create the recorded data and detect the reproduced data. It has the advantage that it does not require self-clocking capability like the limited code, and is less prone to problems such as clock deviations that occur with self-clocking. On the other hand, the self-clocking ability is due to the fact that the data section is divided by servo bytes.
Self clock is not possible. Furthermore, if the phase of the reproduction detection signal and the phase of the recording/reproduction ck deviate, there will be no decoding margin and a detection error will occur. This phenomenon will be explained with reference to FIG. FIG. 8(a) shows the recording/reproduction ck, and FIG. 8(b) shows the RZ recording signal (C) is the NRZI recording signal.The detection signal is
When detected at the center of the recording/reproducing ck decoding window (Tw),
The detection decoding window width is +/−Tw/2, and detection errors are least likely to occur. Next, the detection signal of the optical disc device will be considered. Conventionally, in write-once optical disks,
RZ recording system was used. When the recording power is normal, the recording signal phase and the reproduction signal phase are relatively unlikely to deviate on the disk, and the reproduction detection signal is approximately (b).
It can be reproduced with the normal phase as shown in the figure. but,
The current/power characteristics of the laser power of an optical disk change with respect to temperature, and a phase shift occurs due to a shift in the power characteristic or a change in the power characteristic between the inner and outer circumferences of the disk. This effect becomes very noticeable in rewritable magneto-optical disks. In magneto-optical recording, when laser power is applied to a disk, when the temperature exceeds a predetermined temperature (Curie temperature) with respect to the polarity of the magnetic field, the magnetic film becomes magnetized according to the polarity of the applied magnetic field.
As the disk rotates after the power application is stopped, the magnetization polarity that existed when the disk was cooled to below the Curie temperature remains. Therefore, for the applied power, the residual magnetization pattern is
A time delay occurs, and during playback, the phase of the playback detection signal advances with respect to the recording/playback ck. To reduce the rotational waiting time due to erase and write modes, which is required in recent conventional magneto-optical disks. A system with an immediate override function has been proposed for magneto-optical disks. The most feasible method is the magnetic field modulation override method. In this method, when recording, the laser power is set to DC recording power, and the magnetic field polarity is changed by a recording modulation signal, and erasing and recording are performed in the same mode. It is possible to override the previous version. At this time, NR
By performing magnetic field modulation using the ZI recording method, RZ
It is also possible to achieve a significant improvement in recording density compared to the recording method. The reason for this is that when recording is possible with the same minimum pit length, the recording density in NRZI recording is twice as high as that in RZ recording. However, when the magnetic field modulation method is adopted in a sample servo optical disk, the above playback detection signal,
It has been reported that the phase of recording and playback changes significantly.

References include Yamada et al, “opticat
Storage Technology
ApplicationN, SPIEProceed
ing Vol, 899-24゜12-15. Jan
, 1988 At this time, the reproduced signal becomes as shown in (d) with respect to the recording/reproducing ck phase, and its detection signal (e) leads by ΔT with respect to the recording signal phase. The value of 8T was extremely large compared to the window width of the recording/reproducing ck, and it was difficult to record/reproduce data using the recording/reproducing ck in a sample servo type optical disk. As explained above, the signal format of the conventional sample servo type optical disk is configured to use the recording/reproducing CK and decoding the reproduction detection signal.
It was not possible to correct the phase shift. In particular, with the magnetic field modulation override recording method, this phase shift causes
Detection errors occurred, making it difficult to provide optical disks with the same high-speed data recording and reproducing function as magnetic disks. This invention was made to solve the above-mentioned problems, and is applicable to sample servo type optical disk devices, regardless of write-once disks and magneto-optical disks, and also in magnetic field modulation override recording of magneto-optical disks. This invention provides a new signal format that can eliminate the phase shift between the recording/reproducing ck and detection signals through circuit processing.

[Means for Solving the Problems] A signal format according to the present invention follows a preformatted header area. By writing a fixed pattern at the time of recording into the first segment area, the phase shift between the detection signal and the recording/reproducing ck is detected in this segment area during playback, and a circuit processing system capable of optimal correction is configured. This is to eliminate the discrepancy.

[Operation] In the signal format of the present invention, during recording, a clock pit is detected, a recording/reproducing ck for recording/reproducing data is created, and a header signal is detected by this recording/reproducing ck. This detection signal sets the data area of the preformatted recording sector, records a fixed pattern in the segment area preceding the data, and then records the data.

During playback, the header signal is detected by the recording/playback check, and the data area of the sector is set.In addition, in this fixed pattern area, the playback detection signal is corrected for the amount of phase shift using a tapped delay line circuit, etc. However, by detecting and decoding the reproduced signal using the corrected detection signal, an error-free optical disc device can be constructed.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a diagram showing an example of a recording format according to the present invention. As in the conventional example, data is recorded in a sector structure, and FIG. 1(a) corresponds to FIG. 5(b). (1) does not indicate the data format within one track. The inside of (1) is divided into segments (2) of 4.5 bytes each, and each segment contains 4 bits of data (9) and a gap part for wobble bits of 0.5 bytes ( 6) Consists of. In the gap part (4), wobble bits (5), (6), and (8) are recorded one by one, and wobble bits (5) and (8) are recorded from the direction of travel of the light beam. The wobble bit (6) is shifted by about 1/4 of the bit size to the right from the center of the track when viewed, and the wobble bit (6) is shifted by about 1/4 of the bit size to the left from the center of the track when viewed from the direction of travel of the light beam. The difference is about /4.

Also in the signal format according to the present invention, tracking servo can be performed in the same way as in the conventional example.

Regarding changes in the tracking error signal, in the conventional example, a new tracking error signal was obtained every 16 bytes, but with the signal format shown in Figure 1, a new tracking error signal is obtained every 4 bytes. Bandwidth can be increased by a factor of four. (7)
is the header provided in the track (1), and is the track address data part, which has a length of 4.5 bytes like the segment part, and its internal structure has a gap part (4) and a data part. However, all of the tracks are recorded as pre-pits, and in the data section, codes corresponding to the track addresses are recorded. The data section in the segment following the header is a recordable/reproducible area, and a fixed pattern is recorded in the first segment section. By using this signal format, the phase shift between the recording/reproducing ck and the reproduction detection signal can be corrected by circuit processing during reproduction. Hereinafter, a method for correcting the phase shift of a reproduction detection signal recorded and reproduced using the signal format of the present invention will be described with reference to a specific example. FIG. 2 is a block diagram of a recording/reproduction data creation circuit for the signal format of the present invention. The difference from the conventional circuit in Fig. 6 is that the regenerative detector (
Before being input to the decoder (25), the output signal of 21) is input to a phase corrector (22) in order to correct the decoding phase shift between the previous recording/reproduction ck and the reproduction detection signal. The discrepancy will be corrected. FIG. 3 shows an example of a phase shift correction circuit.

FIG. 4 is an explanatory diagram thereof. The playback detection signal is sent to the terminal (50
), the signal is made into a constant pulse width by the constant width pulse generator (51), and is input to the tapped delay line (DL line) (52) with the minimum delay amount between taps, and each signal is delayed by 7. Obtain signals 01-08. In FIG. 4, the data part of each segment and the signal (b) of the gap part for the signal format (a) in the track are
The timing position is known from k(f), and the timing signal (c) indicating the preformat area and the timing signal (c) of the fixed pattern area following the header are known.
d) is input to each terminal (61) and (55). For example, the recording signal of the fixed pattern area is as shown in (e).
001001...00100 pattern. During reproduction, the recording pattern of the decoded RZ flaw signal in the fixed pattern area is already known, and a recording pattern (g) having the same phase as the recording signal is input to the terminal (54). In Figure 3,
Each delayed reproduction detection signal 01-081'! , clock and clear terminals are input to the counter (53) on the same line. As this counter, for example, 5N7416
Using a synchronous counter like 3N, each O1 to 08
Suppose that is connected to the ET and EP terminals. This counter is counted up only when the clock signal (g) is input and signals 01 to 08 are at a high level. The CL terminal input (the inverted signal in (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 whose phase matches each delay line output (j) to (k) and the clock signal (g) is maximum. It operates as if it had a count value. The determination circuit (56) is a logic circuit for determining, for example, the maximum count input line O1-08 of each counter output value, and outputs a 3-bit code indicating the input line. This determination code is latched by the latch circuit (57) at the end of the fixed pattern, and the selector (59) outputs the DL line output signal with the minimum phase error. On the other hand, when the reproduction detection signal of the pre-pit section passes through such a correction circuit, it causes a shift opposite to the normal phase, so the selector (60) uses the switching signal (c) and inputs it to the DL line. Output the signal as a detection signal. As described above, it is possible to correct the recording/reproduction ck and its phase of the reproduction signal recorded in the fixed pattern area using the phase corrector. By setting the tapped delay line to = 5 ns, the phase correction error of the recording/playback data of the 5 Mbps (2-7) RLLC code is ±5 nsecC, and the decoding window (= ±
50nsec), it can be made sufficiently small. Moreover, the fixed pattern in the signal format of the present invention may be any pattern. Furthermore, instead of the delay line, it is also possible to delay the detection signal using a high frequency clock signal or the like. Further, by performing statistical processing on the determination logic of the determination circuit (56) in FIG. 3, it is possible to improve its determination ability.

[Effects of the Invention] As described above, by using the signal format of the present invention, it is possible to avoid preformatting, which is a problem when performing magneto-optical recording, RZ/NRZI recording, and magnetic field modulation override recording on sample servo type optical disks. The phase shift between the recording/reproducing clock created from the clock pits and the reproduction detection signal can be corrected by circuit processing, and the capacity and transfer rate of the optical disc device can be improved. Furthermore, the hardware for obtaining this effect is also composed of logic circuits, which can be easily integrated into an LSI and has high practical value.

[Brief explanation of the drawing]

Figure 1 is a signal format according to one embodiment of the present invention. Figure 'jIK2 is an example of a recording/reproduction data creation circuit that embodies the intended effect of the present invention. FIG. 3 shows one embodiment of a phase corrector which is the core of the purpose of the present invention. FIG. 4 is an explanatory diagram of FIG. 3. FIG. 5 is an example of a conventional signal format. FIG. 6 shows an example of a conventional recording/reproduction data creation circuit, and FIG. 7 is an explanatory waveform diagram of FIG. FIG. 8 is an explanatory diagram of the recording/reproducing clock and the decoding phase of the detection signal. 1'i"l Ii ω12 te"97oh7,,,/
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Claims (1)

[Claims] From the pre-formatted servo area detection signal,
In the signal format of a sample servo type optical disk that obtains tracking servo information and recording/reproduction clock creation information, a plurality of segment areas each consisting of a pair of the servo area and a data area constitute a sector for data recording/reproduction, and , a header signal indicating the sector track information is present in the first segment of the sector,
An optical disc signal format characterized by having a fixed data recording area following the header area for the purpose of setting the phase of a data recording/reproducing clock and a reproduced data detection signal to an optimal phase for decoding.