JPH06318367A - Optical disk device - Google Patents

Abstract

PURPOSE:To detect a correct synchronizing signal by linking three kinds of symbols A, B and C with prescribed bit lengths respectively in the order of BCBCCCBBACBA and constituting a symbol string. CONSTITUTION:Three kinds of symbols A, B and C with prescribed bit lengths respectively are linked in the order of BCBCCCBBACBA and the symbol string 30 is constituted, and the symbol string is provided in front of the data 40 with a prescribed unit as a synchronizing pattern. Then, in the detection, the symbol string is referred to a three byte pattern 300 shown in (2), and the extent in coincidence is detected. Thus, the synchronization detection with sufficient high reliability is performed though the rate of occurrence in a disk medium is allowed to a certain extent also.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous information recording / detecting device in an optical disk device, and more particularly to an optical disk medium capable of detecting a synchronous signal with high reliability and an optical information recording / reproducing method using the same.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a format for recording data on an optical disc. The data recording unit will be referred to as a sector hereinafter. That is, FIG. 1 shows a sector format. Data is encoded and modulated in a form suitable for an optical disc, and is recorded.
In addition to data for clocking, synchronization, etc., synchronization signals,
Addresses, clocks, various marks, etc. are recorded according to a predetermined format.

The recording format is, for example, Japanese Patent Laid-Open No. 50-1245.
17, JP-A-56-101652, JP-A-56-1
As described in Japanese Patent No. 37531, etc., the reflectance is locally changed by dissolving the recording layer on the surface of the optical disk or causing a chemical reaction. Alternatively, the Review of the MCA Disco-Vision System, July
As described in 1974 Journal of the SMPTE Vol.83), circular holes or oval holes are formed on the surface of an optical disc to cause a phase change in irradiation light. The present invention is directed to such an optical disc medium.

In FIG. 1, 1 is a mark indicating the start of a sector, 40 is address information, and 41 is data.
20, 21 and 30, 31 are recorded as clocking and synchronizing signals for reading these addresses and data. The regions 20 and 21 for clocking activate a phase locked loop (PLL) during this period, and generate a clock for reading the address information 40 and the data 41. The synchronization signals 30 and 31 are address information 4 respectively.
0, the start point of the data 41.

[0005]

The format close to that shown in FIG. 1 is generally used in conventional magnetic recording devices and the like, but the characteristics of the recording medium are basically different between magnetic recording and optical disk. Therefore, even if the formats shown in FIG. 1 are similar, the recorded contents are completely different. In particular, the optical disc medium has a problem that the error rate is larger than that of the magnetic medium because the recording density is high. Therefore, when signals are recorded on the optical disc in the above format, the concrete structures of the clocking signals 20, 21 and the synchronizing signals 30, 31 and the like must be configured in consideration of the conditions peculiar to the optical disc, which are different from the conventional ones.

There are several possible optical disk coding and conversion methods. The ratio of data words converted to code words, that is, code words (bits)
/ Data words (bits) of 2 are often used. Recording on the disc is performed by forming bits in the "1" portion of the code word.

If the bit frequency of the data is f, the frequency of the code word is 2f. Therefore, in data reproduction, the clock frequency of 2f is reproduced from the read code word,
Inverse conversion from code words to data words, that is, decoding is performed. Since the reproduced data has a clock frequency of f, it is necessary to convert 2f to f in the decoding process. To do this, it is sufficient to divide 2f by 1/2, but if 2f is divided by 1/2, two phases are generated in the output f, and the correct phase is selected from these two for correct decoding. You have to choose. That is, it is necessary to determine the clock phase required for decoding.

A specific sync pattern is also recorded for the sync signal for knowing the starting point of the recorded data, and the detection is made by comparing the read reproduction signal with the sync pattern and detecting the coincidence. It is used as a synchronization signal. Therefore, if there is an error in the synchronization pattern, normal synchronization detection is not performed even if there is a 1-bit error. However, the error rate of the optical disk medium is large, and the bit error rate is 10 ⁻⁶ to 10 ^−8.
The system must be assembled to a certain degree.

If the bit error rate is p and the length of the sync pattern is B bits, the probability that one or more errors are included in the sync pattern is approximately Bp. This value is unacceptable in relation to the error rate of the data recorded on the disc.

For example, the data error rate is from 10 ^-10 to
When a quality of 10 ⁻¹² or the like is to be achieved, the error can be reduced in the data portion in the form proportional to p ³ by adding an error correction code (for example, a double error correction code is used). If the signal is erroneous with a value proportional to p, the error processing in the data section becomes completely meaningless. This is because the processing of the data section is established on the assumption that the clock signal and the synchronizing signal are accurate. Since the error rate of the optical disk is a large value as described above, there is a problem in that data cannot be reproduced with high reliability by the conventional synchronization detection.

It is an object of the present invention to provide an optical disc medium which can guarantee correct sync signal detection even if the recording medium has an error as long as it is within a predetermined range.

[0012]

The present invention is a disk medium for optically recording and reproducing information, in which three types of symbols A, B and C having a predetermined bit length are BCBC.
CCBBACBA is connected in order to form a symbol string,
It is characterized in that the symbol string is provided as a synchronization pattern before data of a predetermined unit. It is also possible to have address information before the data. A mark indicating the beginning of a recording unit of information may be provided before the address information.

A mark indicating the beginning of a recording unit of information, address information after the mark, a first clocking signal after the address information, a synchronization pattern and data after the first clocking signal are recorded in one recording unit. It is preferable to have Further, it is also desirable to have a second clocking signal after the mark indicating the beginning of the recording unit of information and address information after the second clocking signal.

It is also possible to have the same sync pattern as the sync pattern before the address information, and it is also possible to use a plurality of sync patterns connected in series.

A 4-bit pattern as a symbol, for example, a symbol is A = (1000), B = (0100), C
It is desirable to configure so that = (0010).
As described above, these patterns can be formed by locally changing the reflectance or forming a round hole or an oval hole on the surface of the optical disk to cause a phase change in the irradiation light.

[0016]

The optical disk medium according to the present invention has a special symbol array in which the synchronization pattern has a sharp peak which is the autocorrelation function and has a small autocorrelation number except for the correct synchronization timing. In the optical information recording / reproducing method using this, the majority logic, that is, n
When m or more (m <n) of the sync detection outputs are detected, a sync signal is output. In such a synchronization pattern, if there is even a slight bit shift, when a match is made on a symbol-by-symbol basis, the number of matching symbols is extremely small, so that it is possible to prevent a false signal from being output.

[0017]

The present invention will be described in detail with reference to the following examples.
There are several possible data recording and conversion methods, and the synchronization pattern is the same as the data modulation rule. This condition is a request from using the same reproducing circuit and detecting circuit as the data.

FIG. 2 shows a coding rule in the embodiment of the present invention. This rule is called the 2-7 modulation rule. It is recorded on the disc by forming bits in the "1" part of the code word. Therefore, the read signal is only the "1" portion of the code word, and these clocks and data are reproduced. The synchronization signal pattern is also consistent with the rule of FIG.

FIG. 3A shows a synchronization pattern 3 according to the present invention.
0 is an example. However, the symbols A, B, and C are A = (1000), B = (0100), and C = (001, respectively.
0) pattern. Although the synchronization pattern length in this embodiment is 3 bytes, other lengths may be used. For detection, the 3-byte pattern shown in FIG. 3B is used as a reference pattern, and the read pattern and the reference pattern 300 are collated to check the degree of coincidence. Reference numeral 20 is a clock signal, and 40 is a data area. These signals can be formed by locally changing the reflectance or by forming a round hole or an oval hole on the surface of the optical disk to cause a phase change in the irradiation light. It may be formed together with the data, or may be formed on a disk in advance and placed.

In FIG. 4, A, B, and C are considered as one symbol, and the read pattern and the reference pattern are symbol units,
This is an examination of what degree of coincidence the timing deviation shows.

That is, in FIG. 4A, the time t = 0 indicates the correct synchronization timing, t <0 indicates before the correct time, and t> 0 indicates after. The t-axis is a bit unit of data. When t = 0, all 3-byte patterns (that is, 12 symbols) match, but the number of matches when t ≠ 0 is small. Therefore, for example, if the sync signal SYNC pulse (shown in FIG. 4B) is output when the number of symbol matches is 8 or more, the sync signal can be correctly detected even if an error occurs in any 4 symbols in the sync pattern. .

The sync detection gate signal shown in FIG. 4C is used so that a similar pattern does not occur in data or the like and is not mistaken. This gate signal is generated from the detection signal of the sector mark 1 in FIG. 1 and the like, but it is omitted here because it is not particularly difficult.

FIG. 5 shows an embodiment of the sync signal detection circuit. The signal detected from the disk is a signal corresponding to the code word "1" in FIG. 2 and the read signal 50 is taken into the shift register 6 by the reproduction clock 51. The shift register 6 has a number of stages capable of handling at least 12 symbols of information in codeword units. The output 60 of the shift register 6 is decoded by the decoder 7 in symbol units. Decoding is performed by collating with the reference pattern in FIG.

Specifically, each symbol can be realized by the configuration as shown in FIG. The output 70 of the decoder 7 is the number of symbols (12) and guides this to the majority logic circuit 8. Here, it is detected that m or more (m <n) of n is established, that is, (n · m) + (n · m + 1) + ... + (n
Output 80 for the input of the combination n). This output is gated by a gate signal 91 (FIG. 4C) and an AND gate 90, output as a synchronizing signal 92 (FIG. 4B), and used as a time reference point in the data signal.

The signal 93 entering the gate 90 of FIG. 5 is clock phase information. That is, since the synchronization signal is generated at the phase of a specific clock, it is intended to prevent the output from being output at other phases and further reduce the error occurrence probability. That is, if the symbol synchronization timing (4 code bits) is detected at the same time as the clock reproduction in the portion 20 of FIG. 1, the error occurrence probability can be reduced by using this as the clock phase information 93.

FIG. 7 shows a case where two synchronization patterns are used, and even if the entire synchronization pattern is erased due to lack of a large medium, for example, one of the two synchronization patterns has a correct synchronization signal. It is made possible to detect. Note that FIG. 7A shows an example of the format, and FIGS. 7B and 7C show the synchronization detection gate signal.

FIG. 8 shows a detection circuit in this case, which is different from FIG. 5 in that an AND gate 902, a predetermined time delay circuit 94 and an OR gate 95 are added and a gate signal 912 is newly provided.

The detection signal degree of the sync signal according to the present invention will be described below. In FIG. 4, it is considered that the probability of lowering the number of matching symbols by m by t = 0 due to the occurrence of an error is approximately P ₀ (m). However, P ₀ (m) is a burst error occurrence probability of m symbol length. On the other hand, the probability of increasing the number of matching symbols by k at t ≠ 0 is considered to be approximately P ₀ (k) P ₁ k.
However, P ₁ is the probability that one symbol is mistaken for another symbol.

The majority logic circuit threshold for detecting the synchronization signal is t =
When it is assumed that the value is M less than the number of matching at 0 and K more than the maximum number of matching at t ≠ 0 (in the embodiment of FIG. 4, if the threshold value is 8 then M = K = 4). At t = 0, the probability that a sync pulse does not occur is ~ P ₀ (5) and t ≠ 0.
Probability of synchronization pulses false results in becomes ^{_{~P 0 (4) P 1 4}} .

In the case of duplication as shown in FIG. 8, the probability of error at t = 0 is ~ {P ₀ (M + 1)} ² = (P ₀ (5)) ² or at worst P ₀ {2 (M + 1) )} = P ₀ (10) or less. The above error is greatly improved as compared with the case of ~ Bp in the conventional method. The evaluation of the error rate is performed by treating the disc as a burst channel. When the error is random, it is sufficiently smaller than the above evaluation result and there is no problem.

[0031]

As described above, according to the present invention, the error occurrence rate of the disk medium is allowed to some extent, and the synchronization signal can be detected with sufficiently high reliability. In the error occurrence probability (~ Bp) of the synchronization signal by the conventional medium, p = 10 ^-6 ~ 1
With ^respect to the medium quality level of about ^0-8 , no matter how high-performance and complicated error correction is applied to the data section, data recording / reproducing with high reliability cannot be realized. Therefore, according to the present invention, the data recording / reproducing at the practical reliability level can be realized for the first time, and the effect is very large.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a recording format on an optical disc.

FIG. 2 is a table showing an example of data encoding.

FIG. 3 is a conceptual diagram showing a synchronization pattern in the embodiment of the present invention.

FIG. 4 is a conceptual diagram showing characteristics when a sync pulse is detected in the embodiment of the present invention.

FIG. 5 is a block diagram showing an embodiment of a sync pulse detection circuit.

6 is a circuit diagram showing a specific example of the decoder circuit of FIG.

FIG. 7 is a conceptual diagram showing a recording example of a synchronization pattern different from that of FIG.

FIG. 8 is a block diagram showing an embodiment of a corresponding detection circuit.

[Explanation of symbols]

 30 ... Symbol string, 40 ... Data.

Claims (17)

[Claims] 1. A disk medium for optically recording and reproducing information, wherein three types of symbols A, B, and C having a predetermined bit length are connected in the order of BBCCCCBBACBA to form a symbol string, and the symbols are formed. An optical disc medium having a row as a synchronization pattern before a predetermined unit of data. 2. The optical disk medium according to claim 1, further comprising address information before the data. 3. The optical disk medium according to claim 1, further comprising a mark indicating the beginning of a recording unit of information before the address information. 4. A mark indicating the beginning of a recording unit of the information, the address information after the mark, a first clocking signal after the address information, and the synchronization after the first clocking signal. The optical disc medium according to claim 3, which has a pattern and data as one recording unit. 5. The second clocking signal after the mark indicating the beginning of the recording unit of the information, and the address information after the second clocking signal.
The optical disk medium described. 6. The optical disk medium according to claim 4, which has the same sync pattern as the sync pattern before the address information. 7. The optical disk medium according to claim 1, wherein a plurality of the synchronization patterns are connected in series and used. 8. The optical disk medium according to claim 1, wherein a 4-bit pattern is used as the symbol. 9. The symbol is A = (1000), B =
The optical disc medium according to claim 8, wherein (0100) and C = (0010). 10. A synchronization pattern having a peak in an autocorrelation function by connecting three types of symbols A, B, and C having a predetermined code bit length in the order BCBCCCCCBBACBA, and the synchronization pattern is coded data of a predetermined unit. Is recorded on the disk medium in an optically reproducible form by adding it to the front part of the, and the signal is optically read from the disk medium,
An optical information recording / reproducing method in which the same symbol sequence as the synchronization pattern is used as a reference pattern, the read signal is collated with the reference pattern in symbol units, and a synchronization signal indicating the starting point of the data is obtained based on the collation result. 11. The optical information recording / reproducing according to claim 10, wherein the number of symbols matching the reference pattern is compared with a predetermined threshold value, and a synchronization signal indicating the starting point of the data is obtained based on the comparison result. Method. 12. Prior to recording the coded data to which the synchronization pattern is added, address information in which the same synchronization pattern as the synchronization pattern is added to the front part is recorded and added to the front part of the address information. 12. A synchronization signal indicating the starting point of the address information is obtained from the synchronization pattern.
The described optical information recording / reproducing method. 13. The optical information recording / reproducing method according to claim 10, wherein a plurality of the synchronization patterns are connected in series and added. 14. A specific mark is recorded prior to recording the coded data to which the synchronization pattern is added,
A gate signal for limiting the detection of the synchronization signal within a predetermined range is obtained from the read signal of the mark.
3. The optical information recording / reproducing method described in any one of 3. 15. The optical information recording / reproducing method according to claim 10, wherein a 4-code bit pattern in which only one is “1” and the other is “0” is used as the symbol. 16. The symbol is A = (1000), B.
16. The optical information recording / reproducing method according to claim 15, wherein = (0100) and C = (0010). 17. The optical information recording / reproducing method according to claim 10, wherein the coded data is converted by a coding method having a codeword-to-dataword ratio of 2.