JPH02113469A - Detector for optical disk synchronizing signal - Google Patents

Abstract

PURPOSE:To accurately detect an optical disk synchronizing signal even at the time of drop-out or drop-in of a regenerative signal by using the signal resulting from OR between a normal synchronizing signal and a pseudo synchronizing signal as the synchronizing signal. CONSTITUTION:A regenerative signal b' is outputted as a binarization output C', which has the noise gated in a binarization circuit 2 by a normal slice level, by a binarization circuit 2. A synchronizing signal is detected by a servo pattern recognizing circuit C1. A phase locked loop circuit 10 outputs a channel clock based on this synchronizing signal, and a pseudo synchronizing signal (j) is generated by a pseudo synchronizing signal generating circuit 11. At the time of dropout or drop-in of the regenerative signal b', OR between the synchronizing signal from the circuit C1 and the signal (j) is operated by an OR circuit 12. Thus, the synchronizing signal free from drop-out like a signal (k) is outputted from an output terminal 9.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to the detection of a synchronization signal of a sampled format disc device in an optical disc, and in particular to an optical disc that makes detection of a synchronization signal for a phase-locked loop highly reliable. The present invention relates to a synchronization signal detection device.

[Prior Art] In a sampled format disk device, extracting a disk synchronization signal is essential for stabilizing the servo and increasing the reliability of signal recording and playback, and 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 disk, 2 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 signals b to i at various locations in FIG. 3 relative to the servo pattern of the disk. FIG. 4a shows a pre-pit servo pattern in the sampled format, in which al is the first wobble, C2 is the second wobble, and C3 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 reproduction signal from the optical disc is converted into two by the binarization circuit 2.
A servo pattern recognition circuit C converts the value into a binary signal C.
In the servo pattern recognition circuit C1, first, the retriggerable monomulti circuit 3 uses this binary signal C as a trigger to output the second wobble a2 and the synchronization signal 8.
A signal d with a pulse width according to the unique distance length between 3
Furthermore, using the end of each of these pulses as a trigger, a retriggerable monomulti circuit 4 generates a signal e for gating the synchronization signal a3. Next, the synchronization signal f is detected by ANDing the signal e and the binary 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 missing bit,
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, the optical disc synchronization signal detection device of the present invention includes a binarization circuit that binarizes a playback 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 pseudo synchronization signal that generates a pseudo synchronization signal based on the channel clock. A generating circuit is provided, and the synchronization signal outputted from the servo pattern recognition circuit and the pseudo synchronization signal are used together.

[Function] In this configuration, the reproduction signal of the servo pattern when recording or reproducing data on the sampled format optical disk is binarized by the binarization circuit, and only the synchronization signal is extracted by the servo pattern recognition circuit. on the other hand,
Based on this synchronization signal, the phase-locked loop circuit outputs a phase-locked channel clock, and based on this channel clock, a pseudo synchronization signal is generated in the pseudo synchronization signal generation circuit. Then, a signal obtained by ORing the above-mentioned extracted synchronization signal and this pseudo synchronization signal, for example, 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 etc., and the synchronization signal is not detected by the servo pattern recognition circuit,
Supplemented by a pseudo sync signal.

[Example] 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 reproduction signal input terminal, C2 is the conventional circuit shown in FIG. 3, and CI is a servo pattern recognition circuit. 9 is a synchronization signal output terminal, 10 is a phase-locked loop circuit, 11 is a pseudo synchronization signal generation circuit, and 12 is an OR (
It is a 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 figure, a' indicates the actual servo pattern in the sample servo, and b', ci', and j indicate the signals of each part indicated by the same reference numerals in FIG.

Next, the operation of this device will be explained.

In the above configuration, the reproduced signal b' is noise gated by the binarization circuit 2 at a normal slice level and outputs a binarized output C'. 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. 1376 synchronizing signal pulses are extracted per disk cycle, and this synchronizing signal that has passed through the OR circuit 12 is multiplied and divided by 270 in the phase-locked loop circuit 10 to generate a channel clock. Then, by inversely counting this channel clock by 270 in the pseudo synchronization signal generation circuit 11, a pseudo synchronization signal j is generated at the same timing as the original synchronization signal.

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 pseudo synchronization signal j is outputted by the pseudo synchronization signal generation circuit 11, and this output is ORed with the original synchronization signal from the circuit C3 and outputted from the OR circuit 12.
The synchronization signal without any missing signal is output to the synchronization signal output terminal 9.
is output from.

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 a normal synchronization signal and a pseudo synchronization signal, for example, is used as a more reliable synchronization signal. The inability to detect synchronization signals due to dropouts or drop-ins caused by unevenness, reflection film unevenness, etc. is eliminated. Furthermore, there is also the effect that the phase-locked loop circuit essential for stabilizing the sampled 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, 2: Binarization circuit, 3.4, 6, 7: Retriggerable mono multi circuit, 5. 8+AND circuit, 9: Synchronization signal output terminal, 10: Phase-locked loop circuit, 11: Pseudo synchronous signal generation circuit, 12: OR circuit.

Claims (1)

[Claims] 1. A binarization circuit that binarizes the reproduced signal, a servo pattern recognition circuit that detects a synchronization signal based on the output of the binarization circuit, and a phase-locked loop circuit that generates a channel clock based on the synchronization signal. , a pseudo synchronization signal generating circuit that generates a pseudo synchronization signal based on the channel clock, and detecting an optical disc synchronization signal, characterized in that the synchronization signal output from the servo pattern recognition circuit and the pseudo synchronization signal are used together. Device.