JP2639378B2 - Optical disk media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording and detecting synchronization information in an optical disk apparatus, and more particularly to an optical disk medium capable of detecting a synchronization 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 disk. The data recording unit is hereinafter referred to as a sector. That is, FIG. 1 shows a sector format. Data is encoded and modulated in a form suitable for optical discs, and recorded.
In addition to data for clocking, synchronization, etc., synchronization signals,
The address, clock, various marks, etc. are recorded according to a predetermined format.

[0003] The recording mode is described in, for example,
No. 17, JP-A-56-101652, JP-A-56-1
As described in U.S. Pat. No. 3,751,331 and the like, the reflection is locally changed by dissolving the recording layer on the optical disk surface or causing a chemical reaction. Or, review of the MCA Disco-Vision System, July
As described in, for example, 1974 Journal of the SMPTE Vol.83), this is performed by forming a round hole or an oval hole on the surface of an optical disc to cause a phase change in irradiation light. The present invention is directed to such an optical disk medium.

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

[0005]

Although a format close to that shown in FIG. 1 is generally used in a conventional magnetic recording apparatus and the like, the characteristics of a recording medium are basically different between magnetic recording and an optical disk. Therefore, although the format as shown in FIG. 1 is similar, the recorded content itself is completely different. In particular, an optical disk medium has a problem that the error rate is higher than that of a magnetic medium due to a high recording density. Therefore, when recording signals on the optical disk in the above-described format, the specific structures of the clocking signals 20, 21 and the synchronization signals 30, 31, etc., must be configured in consideration of the conditions specific to the optical disk, which are different from the conventional ones.

Several schemes are conceivable as a coding scheme and a conversion scheme for an optical disc. A ratio when a data word is converted into a code word, that is, a code word (bit) is used.
/ Data words (bits) of 2 are often used. Recording on the disk is performed by forming bits in the "1" portion of the code word.

If the bit frequency of data is f, the frequency of the code word is 2f. Therefore, in data reproduction, a clock frequency of 2f is reproduced from the read code word,
Performs reverse conversion, ie, decoding, from code words to data words. Since the reproduced data has a clock frequency of f, it is necessary to convert 2f to f in the decoding process. This can be done by dividing 2f by が. However, dividing ｆ by 2f results in two phases of the output f. For correct decoding, the correct phase must be selected from the two. You have to choose. That is, it is necessary to determine the phase of the clock required for decoding.

A specific synchronization pattern is also recorded for a synchronization signal for knowing the starting point of the recording data. The detection is performed by comparing the read reproduction signal with the synchronization pattern and detecting that they match. It is a synchronization signal. Therefore, if there is an error in the synchronization pattern, even if there is a one-bit error, normal synchronization detection is not performed. However, the error 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 synchronization pattern is B bits, the probability that one or more errors are included in the synchronization pattern is approximately Bp. This value is unacceptable in relation to the error rate of the data recorded on the disk.

For example, a data error rate of 10 ^-10 to
In order to achieve a quality of 10 ⁻¹² or the like, the error can be reduced in the data portion in a manner 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, error processing in the data part becomes completely meaningless. This is because the processing of the data section is performed on the assumption that the clock signal and the synchronization signal are accurate. Since the error rate of the optical disk is a large value as described above, there is a problem that data cannot be reproduced with high reliability by the synchronous detection according to the conventional method.

An object of the present invention is to provide an optical disk medium that can guarantee correct detection of a synchronization signal even if an error occurs in a recording medium as long as the error is within a predetermined range.

[0012]

SUMMARY OF THE INVENTION The present invention relates to 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 sequence,
The present invention is characterized in that the symbol sequence is provided before a predetermined unit of data as a synchronization pattern. It can also have address information before the data. A mark indicating the start 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 following the mark, a first clocking signal following the address information, a synchronization pattern following the first clocking signal, and data are recorded in one recording unit. It is preferred to have as. It is also desirable to have a second clocking signal after the mark indicating the beginning of the information recording unit and address information after the second clocking signal.

Further, it is also possible to configure so as to have the same synchronization pattern as the synchronization pattern before the address information, and a plurality of synchronization patterns may be connected in series.

A 4-bit pattern as a symbol, for example, a symbol is A = (1000), B = (0100), C
= (0010).
As described above, these patterns can be formed by locally changing the reflectivity 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.

[0016]

The optical disk medium according to the present invention has a special symbol array whose synchronization pattern has a sharp peak in its autocorrelation function and has a small number of autocorrelations except for correct synchronization timing. In the optical information recording / reproducing method using this, majority logic, that is, n
A synchronization signal is output when m or more (m <n) of the synchronization detection outputs are detected. In such a synchronization pattern, if there is any bit shift, the number of matching symbols becomes extremely small when matching is performed in symbol units, so that a false signal can be prevented from being output.

[0017]

The present invention will be described in detail with reference to the following examples.
Several data recording and conversion methods are conceivable, and the synchronization pattern is the same as the data modulation rule. This condition is a requirement 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 a 2-7 modulation rule. The data is recorded on the disk by forming bits in the "1" portion of the code word. Therefore, the read signal is only the "1" portion of the code word, and these clocks and data are reproduced. It is assumed that the synchronization signal pattern does not contradict the rule of FIG.

FIG. 3A shows a synchronization pattern 3 according to the present invention.
0 is an example. However, symbols A, B, and C are A = (1000), B = (0100), and C = (001), respectively.
0). Although the synchronization pattern length in this embodiment is 3 bytes, other lengths may be used. For the detection, the three-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. 20 is a clock signal, and 40 is a data area. These signals can be formed by locally changing the reflectivity or by forming a round hole or an oval hole on the surface of the optical disc 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.

FIG. 4 shows that each of A, B, and C is one symbol, and the read pattern and the reference pattern are symbol units.
It is an examination of what degree of coincidence is shown with respect to the timing deviation.

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

The synchronization detection gate signal shown in FIG. 4C is used so that a similar pattern does not occur in data or the like to cause an error. Although this gate signal is generated from the detection signal of the sector mark 1 in FIG. 1, there is no particular difficulty, so that the description is omitted here.

FIG. 5 shows an embodiment of the synchronization signal detecting 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 the information of 12 symbols in code word units. The output 60 of the shift register 6 is decoded by the decoder 7 in symbol units. Decoding is performed by comparison with the reference pattern shown 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), which is led to the majority logic circuit 8. Here, it is detected that m or more (m <n) are satisfied among n pieces, that is, (nm) + (nm + 1) +... + (N
・ Output 80 for the input of the combination of n). This output is gated by a gate signal 91 (FIG. 4C) and an AND gate 90, output as a synchronization signal 92 (FIG. 4B), and used as a time reference point in the data signal.

The signal 93 entering the gate 90 in FIG. 5 is clock phase information. That is, since the synchronization signal is generated at the time of a specific clock phase, the purpose is to prevent the output from being output at another phase and to further reduce the error occurrence probability. That is, if the symbol synchronization timing (4 code bits) is detected together with the clock recovery at the portion 20 in 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. For example, even when the entire synchronization pattern is erased due to lack of a large medium, either one of the two synchronization patterns has a correct synchronization signal. This is to enable detection. 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. Compared to FIG. 5, an AND gate 902, a predetermined time delay circuit 94, and an OR gate 95 are added, and only a new gate signal 912 is required.

A description will be given hereinbelow of the detected signal tone of the synchronization signal according to the present invention. In FIG. 4, the probability of reducing the number of symbol matches by m at t = 0 due to the occurrence of an error is considered to be substantially P ₀ (m). Here, 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 the point of t ≠ 0 is considered to be approximately P ₀ (k) P ₁ k.
However, the probability that P ₁ is the symbol there is a wrong to another symbol.

If the threshold value of the majority logic circuit for detecting the synchronization signal is t =
Assume that the value is M less than the number of matches at 0 and K larger than the maximum number of matches at t ≠ 0 (in the embodiment of FIG. 4, if the above threshold value is 8, M = K = 4). Is that the probability that no synchronization pulse will occur at t = 0 is ＰP ₀ (5)
Probability of synchronization pulses false results in becomes ^{_{~P 0 (4) P 1 4}} .

Further, if the structure is duplicated as shown in FIG. 8, the error probability at t = 0 is ｛{P ₀ (M + 1)} ² = (P ₀ (5)) ² or P ₀て も 2 (M + 1) at worst. )｝ = P ₀ (10) is improved. The above error is greatly improved as compared with the conventional method, which is ＢBp. The above evaluation of the error rate is based on the assumption that the disk is a burst channel. When the error is random, there is no problem in that the error is sufficiently smaller than the above evaluation result.

[0031]

As described above, according to the present invention, it is possible to allow the error rate of the disk medium to some extent, and to detect the synchronization signal with sufficiently high reliability. In the error occurrence probability (ＢBp) of the synchronization signal by the conventional medium, p = 10 ^{−6 １1}
Regardless of the medium quality level of about ^0-8 , no matter how high-performance and complicated error correction is applied to the data part, data recording / reproduction with high reliability cannot be realized. Therefore, according to the present invention, data recording / reproduction at a practical reliability level can be realized for the first time, and the effect is very large.

[Brief description of the 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 coding.

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 synchronization pulse is detected in the embodiment of the present invention.

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

FIG. 6 is a circuit diagram showing a specific example of the decoder circuit of FIG. 5;

FIG. 7 is a conceptual diagram showing a recording example of a synchronization pattern different from that in FIG. 1;

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

[Explanation of symbols]

 30 ... symbol string, 40 ... data.

Claims (20)

(57) [Claims] 1. A disk medium for optically recording and reproducing information, wherein a symbol sequence is formed by connecting three types of symbols A, B, and C having a predetermined bit length in the order of BCBCCCBBACBA. An optical disc medium having a row in front of a data area in which data of a predetermined unit is to be recorded as a synchronization pattern constituted by a row of round holes or oval holes. 2. An optical disk medium according to claim 1, wherein said data area has address information formed by a row of round holes or oval holes before said data area. 3. The optical disc medium according to claim 1, further comprising a mark formed by a row of round holes or oval holes indicating a start of a recording unit of information before the address information. 4. A first clocking signal comprising a mark indicating the start of a recording unit of the information, the address information following the mark, and a row of round holes or oval holes following the address information. , The synchronization pattern and the data area after the first clocking signal are
4. The optical disc medium according to claim 3, wherein the optical disc medium has one recording unit. 5. A second clocking signal composed of a row of round holes or oval holes after a mark indicating the start of the information recording unit, and the address following the second clocking signal. 5. The optical disk medium according to claim 4, having information. 6. An optical disk medium according to claim 4, further comprising a synchronization pattern formed by a row of the same round holes or oval holes as said synchronization pattern before said address information. 7. The optical disk medium according to claim 1, wherein a plurality of said synchronization patterns are connected in series. 8. The optical disk medium according to claim 1, wherein a 4-bit pattern is used as said symbol. 9. The symbol is A = (1000), B =
9. The optical disk medium according to claim 8, wherein (0100) and C = (0010). 10. A disk medium for optically recording and reproducing information, wherein a symbol sequence is formed by connecting three types of symbols A, B, and C having a predetermined bit length in the order of BCBCCCBBACBA. An optical disk medium having a row in front of a data area in which data of a predetermined unit is to be recorded as a synchronization pattern constituted by a row of round or oval optically detectable marks. 11. The optical disk medium according to claim 10, further comprising address information constituted by a row of optically detectable marks of a circle or an ellipse in front of said data area. 12. A mark formed by a circle or an oval optically detectable mark line indicating the start of a recording unit of information before the address information.
12. The optical disk medium according to 0 or 11. 13. A mark constituted by a mark indicating the start of a recording unit of the information, the address information following the mark, and a row of circular or oval optically detectable marks following the address information. 13. The optical disk medium according to claim 12, comprising one clocking signal, the synchronization pattern and the data area after the first clocking signal as one recording unit. 14. A second clocking signal comprising a row of round or oval optically detectable marks after the mark indicating the beginning of the information recording unit;
14. The optical disk medium according to claim 13, comprising the address information following the second clocking signal. 15. A synchronizing pattern comprising a row of the same circular or oval optically detectable marks as the synchronizing pattern before the address information.
Or the optical disc medium according to 14. 16. The optical disk medium according to claim 10, wherein a plurality of said synchronization patterns are connected in series. 17. The optical disk medium according to claim 10, wherein a 4-bit pattern is used as said symbol. 18. The method according to claim 18, wherein the symbols are A = (1000), B
18. The optical disk medium according to claim 17, wherein = (0100) and C = (0010). 19. An optical disk medium capable of optically reproducing information.
And three types of 4-bit patterns A, B, and C
BCBCCCBBACBA is connected in order to form a pattern row.
And the pattern row is used as a row of optically detectable marks.
Before the data area where the data of the predetermined unit is recorded.
Optical disk medium having. 20. An optical disk medium capable of optically reproducing information.
A body having a plurality of sectors along a track;
A sector is a synchronization pattern and a data area following the synchronization pattern.
The synchronization pattern has three types of predetermined bit patterns.
Connect A, B, and C in the order of BCBCCCBBACBA
Pattern pattern, which can be detected optically
Characterized by a series of special marks
Optical disk media.