JPH0574051A - Synchronous information detector - Google Patents

Abstract

PURPOSE:To adapt to the yearly enlargement and increment, as the defect of an optical recording medium by collating the bit pattern of a signal containing synchronous information with a preliminarily set bit pattern and finding the number of coincidence. CONSTITUTION:A regenerative signal 21 read from an optical disk is inputted to a shift register 1, the output 11 is decoded in symbols by a decoder 2. Decoding is performed by the output pattern of the register 1 and a reference pattern. Then, whether respective symbols of the output of the register 1 coincide with the corresponding symbols of the reference pattern or not are outputted as to all the symbols respectively and outputted to a majority decision circuit 3 as a coincidence signal. In the circuit 3, the number of the detected symbol is counted, a count value signal 14 and a threshold signal 16 are compared and a synchronous signal detecting signal 13 is outputted when the signal 14 is more than the signal 16. Thus, the detection and the check of the synchronous information capable of adapting to the yearly enlargement and increment, as well of the defect is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting synchronization information in information recorded on an optical recording medium.

[0002]

2. Description of the Related Art Conventionally, optical recording media such as disk-shaped and card-shaped are known. In a disc-shaped optical recording medium (hereinafter referred to as an optical disc), the recording surface of the optical disc is divided into a plurality of tracks. Further, each track is divided into areas called sectors as a recording unit at the time of read / write.

In an optical disc device for recording and reproducing information on such an optical disc, it is general to record and reproduce information in sector units. As a sector format of an optical disc, there is a system adopted in the ISO5.25 "Write Once optical disc format standard as shown in FIG. 3, for example. FIG. 3 shows a 1-sector format. , SM (sector mark) is a mark indicating that it is the beginning of a sector, and an address code, etc. is recorded in the ID. These SM and ID are already pre-written when the disc is manufactured.
Matted. In this method, user data is recorded on the optical disc as follows. 1. Data is input in 1024-byte units from the host computer. 2. An error correction code is generated and added to the input data. 3. Following VFO and SYNC (synchronization signal), data and an error correction code (1200 bytes, a portion described as DATA in FIG. 3) are modulated by the (2-7) modulation method and recorded on the disc. However, at this time, Resync (resynchronization signal) is inserted into the data and the error correction code (DATA) every 20 bytes.

In order to read the user data recorded in this way, 1. SYNC is detected from the playback signal. 2. The detection of SYNC is used as a trigger to start demodulation of data and error correction code (DATA). 3. 20 during demodulation of data and error correction code (DATA)
Resync inserted every byte is detected, and thereby the above demodulation operation is resynchronized. 4. The demodulated data and the error correction code (DATA) are sent to the error correction circuit, and after the error is corrected,
It is output to the host computer.

In the above user data read method, SYNC or Resync is used to read user data.
It is important to detect sync signals such as. As a detection method for detecting the synchronization signal with high reliability, there is a method disclosed in Japanese Patent Laid-Open No. 58-169341. This is a pattern in which the synchronization signal pattern has a sharp peak in its autocorrelation function and has a small autocorrelation function except at the correct synchronization timing. Then, by using the majority decision logic, high detection reliability is realized. That is, the sync signal detection output is performed when detected from m or more (m <n) of the n sync detection outputs.

Then, such a detection method and the detection of the sync signal for the target sector (all the sectors at the time of the inspection immediately after the disk is manufactured) after the inspection immediately after the disk is manufactured and the data writing to a certain sector are performed. Check,
If the sector is NG, the sector is regarded as a defective sector, and the process of not writing data to the sector at all (hereinafter, referred to as sync signal check) is used in combination, so that the detection of the sync signal is higher. It will be reliable.

[0007]

However, the above-mentioned conventional techniques have not been able to sufficiently cope with an optical disc having a characteristic that defects on a medium expand or change over time. That is, the conventional technique cannot cope with the case where a sector that has been checked OK at the time of checking the synchronizing signal at the time of checking the synchronizing signal becomes undetectable due to the increase of the medium defects thereafter. If the synchronization signal cannot be detected due to such deterioration over time, the address information and the start point of the data are unknown and the read timing control becomes impossible. However, there is a problem that the user data cannot be read.

The present invention has been made in view of the above problems of the prior art, and provides a synchronization information detecting device for an optical recording medium which can cope with the enlargement and increase of defects of the optical recording medium over time. With the goal.

[0009]

In order to solve the above problems, the synchronization information detecting apparatus of the present invention inputs a signal which is a reproduction signal from an optical recording medium and which contains synchronization information indicating the starting point of data. Input means, a decoder for collating the bit pattern of the signal input to the input means with a preset bit pattern of the synchronization information and outputting a coincidence number, and a coincidence output from the decoder. Counting means for counting a number, comparing means for counting the number by the counting means and a threshold value, and comparing means for outputting a synchronization information detection signal if the count number is greater than or equal to the threshold value, and the threshold value The configuration comprises a threshold setting means for setting.

[0010]

With the above configuration, the bit pattern of the signal containing the synchronization information is collated with the preset bit pattern to obtain the number of coincidences, and if the number of coincidences is equal to or more than the threshold value, the synchronization information is detected. Output a signal. Since the threshold value can be set by the threshold value setting means, the threshold value can be set to a strict value corresponding to the enlargement and increase of defects of the optical recording medium over time.

[0011]

1 is a block diagram of a sync signal detection circuit according to an embodiment of the present invention. In FIG. 1, the reproduction signal 21 read from the optical disc is input to the shift register 1. A reproduction clock 22 is also input to the shift register 1, and the reproduction signal 21 is sequentially input in synchronization with the input timing of the reproduction clock 22. The reproduction clock 22 is generally created from the reproduction signal 21.

In the present embodiment, it is assumed that the synchronization signal has 48 bits, and this is considered by dividing it into continuous symbols of 4 bits each. Here, the symbol is a unit of pattern reference described later. As the synchronization signal pattern, it is preferable to use a pattern which has a sharp peak in its autocorrelation function and has a small autocorrelation function except at the correct synchronization timing, as in the conventional case.

The shift register 1 has a stage number capable of handling a signal of at least 12 symbols (48 bits) in code units. The decoder 2 has a bit pattern (hereinafter referred to as a reference pattern) of a sync signal (that is, a sync signal included in the recording signal at the time of recording on the optical disk) which is included in the reproduction signal in advance. Is remembered. The output 11 (bit data of the reproduced signal) of the shift register 1 is decoded by the decoder 2 in symbol units. Decoding is performed by comparing the pattern output from the shift register 1 with the reference pattern. And
Whether each symbol of the output of the shift register 1 matches the corresponding symbol of the reference pattern,
Output for each of the 12 symbols. Therefore, the output 12 of the decoder 2 is equal to the number of symbols (12) and is output to the majority decision circuit 3 as the coincidence signal 12.

FIG. 2 is a diagram showing the configuration of the majority decision circuit 3. As shown in FIG. 2, the majority circuit 3 comprises a counter circuit 4 and a magnitude comparator 5. The counter circuit 4 counts how many symbols can be detected from the output 12 of the decoder 2. That is, of the twelve output signals 12 indicating coincidence / disagreement, the number of signals indicating coincidence is counted. Then, the count value signal 14 is output. The count value signal 14 is input to the magnitude comparator 5. The magnitude comparator 5 inputs the count value signal 14 and the threshold value signal 16 and compares the count value with the threshold value. If the count value is greater than or equal to the threshold value, the sync signal detection signal 13 is output.

In the optical disk device, when the sync signal detection signal 13 is not output, that is, when the sync signal cannot be detected, the sector in which the reproduction signal is recorded is regarded as a defective sector, and data is written to that sector thereafter. Ban. Since the processing for such a defective sector is a well-known technique, its explanation is omitted here. The threshold signal 16 is output from the external sequencer 6. External sheath
The Kenser 6 can set and change this threshold. The threshold value can be switched between normal data reading and synchronization signal checking. Therefore, the threshold for checking the sync signal is set to the normal data level.
If it is made larger than that at the time of read, the above-mentioned processing is performed as a defective sector even if there is a possibility that the synchronization signal cannot be detected due to the expansion and increase of defects in the recording medium (optical disk) in the future. That is, data writing can be prohibited.

Further, at the time of inspection after manufacturing the optical disc,
Even if the synchronization information detection check is performed after writing the data, the check may be performed with a strict threshold value.
In this embodiment, the synchronization information is 48-bit data, but it is not limited to this and may be any number of bits.
Although the symbol has 4 bits, it may have any number of bits. In the decoder 2, the number of matching bits may be detected by referring to each one bit without referring to each symbol.

[0017]

As described above, according to the present invention, it is possible to perform the synchronization information detection check that can cope with the aging expansion or increase of defects of the optical recording medium in which the signal including the synchronization information is recorded. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a synchronization information detecting device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a majority circuit of a synchronization information detecting device according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a sector format of an optical disc.

[Explanation of symbols]

 1 shift register 2 decoder 3 majority circuit 4 counter circuit 5 magnitude comparator 6 external sequencer 11 bit data of reproduced signal 12 coincidence signal of symbol 13 sync signal detection signal 14 count value signal

Claims (1)

[Claims] 1. Input means for inputting a signal which is a reproduction signal from an optical recording medium and which contains synchronization information indicating a start point of data, and a bit pattern of the signal inputted to the input means are preset. A decoder that outputs the number of coincidences by collating with the bit pattern of the synchronized information, a count means that counts the number of coincidences output from the decoder, and a count number and a threshold value by the count means. By comparison, if the count number is equal to or more than a threshold value, a synchronization information detecting device comprising a comparison means for outputting a synchronization information detection signal and a threshold value setting means for setting the threshold value.