JPH02113468A - Detector for optical disk synchronizing signal - Google Patents

Abstract

PURPOSE:To accurately detect a synchronizing signal even at the time of drop- out or drop-in on an optical disk by using the signal resulting from OR between synchronizing signals, which are detected with a normal slice level and a lower slice level respectively, as the synchronizing signal. CONSTITUTION:A regenerative signal b' is outputted as a binarization output C' noise-gated by the normal slice level and a binarization output (j) gated by the lower slice level by binarization circuits 2a and 2b respectively. At the time of drop-out or drop-in of the regenerative signal b', AND between the binarization output (j) due to the lower slice level and a synchronizing signal gate (k) is operated by an AND circuit 13 to detect a synchronizing signal (l). Consequently, OR between the detection signal from a circuit C1 and that from the circuit 13 is operated by an OR circuit 14 to accurately detect the synchronizing signal even at the time of drop-in or drop-out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the detection of a synchronization signal for a sampled format disc device in an optical disc, and in particular to an optical disc that has highly reliable detection of a synchronization signal for a phase-locked loop. The present invention relates to a synchronization signal detection device.

[Prior Art] In a sampled format disk device, extraction of a disk synchronization signal is essential for stabilizing the servo and increasing the reliability of signal recording and reproduction.The signal system and servo system are extracted from this synchronization signal. It operates in synchronization with the obtained PLL (phase locked loop) clock (channel clock).

FIG. 3 is a block diagram showing the configuration of a conventional synchronization signal detection device. In the figure, 1 is an input terminal for playback signals from an optical disc, 2a is a binarization circuit, C1 is a servo pattern recognition circuit, 3, 4.6 and 7 are retriggerable monomulti circuits, and 5 and 8 are AND (logical product) circuit, 9 is a synchronization signal output terminal. FIG. 4 is a timing chart showing the timing of the signal b-i at various points in FIG. 3 with respect to the servo pattern of the disk.

A in Figure 4 shows the pre-pit servo pattern in the sampled format, and a in this pattern
, is the first wobble, a2 is the second wobble, and a3 is a synchronization signal (clock pit). b is a reproduction signal of servo pattern a.

Next, the operation of this device will be explained using FIGS. 3 and 4.

The reproduced signal from the optical disk is binarized by the binarization circuit 2a and output as a binarized signal C to the servo pattern recognition circuit C1. Then, using this binary signal C as a trigger, a signal d having a pulse width corresponding to the unique distance length between the second open pulse a2 and the synchronization signal 83 is generated, and further, using the end of each of these pulses as a trigger, a synchronization signal a3 is generated. A signal e for gating is generated by a retriggerable monomulti circuit 4. Next, the synchronization signal f is detected by ANDing the signal e and the binarized output signal C.

Using the synchronization signal f as a trigger, the retriggerable monomulti circuit 6 generates a pulse g up to the next synchronization signal pulse, and further uses the end of this pulse as a trigger to generate the synchronization signal f.
A retriggerable mono multi-circuit 7 generates a signal for gating the synchronous signal f, and by ANDing the signal and the synchronous signal f, only the synchronous signal i is detected.

[Problems to be Solved by the Invention] However, in the conventional synchronization signal detection device, if there is a defect in the pre-pit itself, for example, if a pit that should have been present is missing, or if there is a pit that does not exist,
Alternatively, if there is a dropout or dropin in the reflective film, there is a problem that the synchronization signal cannot be detected accurately.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an optical disc synchronization signal detection device that can detect a more accurate synchronization signal.

[Means for Solving the Problems] In order to achieve the above object, an optical disc synchronization signal detection device of the present invention includes a first binarization circuit that binarizes a playback signal, and a first binarization circuit that binarizes a reproduction signal; a servo pattern recognition circuit that detects a synchronization signal based on the output of the synchronization circuit; a phase-locked loop circuit that generates a channel clock based on the synchronization signal; and a gate signal for gating the synchronization signal based on the channel clock. comprising a synchronization signal gate generation circuit and a second binarization circuit that binarizes the reproduced signal at a slice level lower than that of the first binarization circuit, and an output of the second binarization circuit. The synchronization signal obtained by gating with the gate signal output from the synchronization signal gate generation circuit and the synchronization signal output from the servo pattern recognition circuit are used together.

[Operation] In this configuration, the reproduction signal of the servo pattern when recording or reproducing data on a sampled format optical disk is, on the one hand, binarized at the normal slice level by the first binarization circuit and used for servo pattern recognition. Only the synchronization signal is extracted by the circuit, but on the other hand, the second
The digitization circuit binarizes the signal at a lower slice level and extracts the synchronization signal contained therein. The latter extraction of the synchronization signal is mainly based on the channel clock of the phase-locked loop circuit, which is phase-locked by the synchronization signal extracted by the servo pattern recognition circuit, and the gate signal output from the synchronization signal gate generation circuit is used to perform the logical product, for example. Extracted via circuit. Then, a signal obtained by ORing the normal and lower-than-normal slice level synchronization signals extracted in this way is output as a more reliable synchronization signal. In other words, even if the signal strength of the servo pattern that should originally be detected is weak due to dropout or the like and the servo pattern recognition circuit does not detect the synchronization signal, the second binarization circuit that binarizes with a low slice level The output includes a synchronization signal, which is detected and output for supplementation.

[Example code] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit block diagram showing the configuration of a synchronization signal detection device according to an embodiment of the present invention.

In the figure, 1 is a reproduced signal input terminal, C3 is the conventional circuit shown in FIG. 3, and C1 is a servo pattern recognition circuit. 2b is a reproduction signal binarization circuit using a signal sliced at a level lower than the normal slice level as a noise gate, 9 is a synchronization signal output terminal, 11 is a phase-locked loop circuit, 12 is a synchronization signal gate generation circuit, and 13 is an AND
The circuit 14 is an OR (logical sum) circuit.

FIG. 2 is a timing chart for the servo pattern of signals in each part of the circuit shown in FIG. In the same figure, a' indicates the actual servo pattern in the sample servo, b' cj, i', It, m
The signals of each part indicated by the same reference numerals in the figure are shown.

Next, the operation of this device will be explained.

In the above configuration, the reproduced signal b' is a binary output C which is noise gated by the binarization circuit 2a at a normal slice level A, and a binary output C which is gated by the binarization circuit 2b at a slice level B lower than normal. It is output as converted output j. Normally, when there is no defect in the disk, the synchronizing signal i shown in FIG. 4 is obtained as the output of the AND circuit 8 shown in FIG.
Based on this signal that has passed through the R circuit 14, the phase-locked loop circuit 11 generates a phase-locked or left channel clock, and based on this channel clock, the synchronization signal gate generation circuit 12 generates a synchronization signal gate k. Ru.

Here, if the playback signal is affected by drop-in or drop-out like signal b', the conventional circuit C1 would not detect a unique distance and therefore would not output a synchronization signal like signal i'. but,
The synchronization signal 1 is detected by ANDing the binary output j from the binarization circuit 2b whose slice level has been lowered and the synchronization signal gate using the AND circuit 13.

Therefore, the OR of the detection output signal from the circuit C2 at the normal slice level and the detection output signal λ from the AND circuit 13 at a lower slice level is performed.
By using the R circuit 14, the synchronization signal can be reliably detected even if the disk has the above-mentioned defect.

In this embodiment, the noise gate signal is created by directly slicing the reproduced signal, but the gate signal may also be created by differentiating this signal, then slicing and delaying the signal.

[Effects of the Invention] As explained above, according to the present invention, a signal obtained by ORing the synchronization signals detected at normal and lower slice levels than normal is used as a more reliable synchronization signal. This eliminates the inability to detect synchronization signals due to drop-outs or drop-ins caused by uneven molding or uneven reflective films. Furthermore, there is also the effect that the phase-locked loop circuit, which is essential for stabilizing the sample servo, can be made more stable.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of a synchronization signal detection device according to an embodiment of the present invention, FIG. 2 is a timing chart for signal servo patterns in each part of the circuit in FIG. 1, and FIG. , a circuit block diagram showing the configuration of a conventional synchronization signal detection device, and FIG. 4 is a timing chart showing the timing of signals at various locations in FIG. 3 with respect to the servo pattern of the disk. 1: Reproduction signal input terminal, 2a, 2b: Binarization circuit, 3.4, 6, 7: Retriggerable mono multi circuit, 8.13: AND circuit, 1 synchronization signal output terminal, 1: Phase-locked loop circuit , 2: Synchronous signal gate generation circuit, 4.OR circuit. patent applicant

Claims (1)

[Claims] 1. A first binarization circuit that binarizes a reproduced signal;
a servo pattern recognition circuit that detects a synchronization signal based on the output of the binarization circuit, a phase-locked loop circuit that generates a channel clock based on the synchronization signal, and a gate signal for gating the synchronization signal based on the channel clock. and a second binarization circuit that binarizes the reproduced signal at a slice level lower than that of the first binarization circuit,
Detection of an optical disc synchronization signal, characterized in that a synchronization signal obtained by gating the output of a value converting circuit with a gate signal output by the synchronization signal gate generation circuit and a synchronization signal output from the servo pattern recognition circuit are used together. Device.