JP2658741B2 - Optical recording / reproducing method - 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 serially recording data, such as an optical disk apparatus, for recording and detecting synchronization information in data.

[0002]

2. Description of the Related Art FIG. 1 shows run-length-limited variable word length coding (Run-
The following shows a correspondence table between data words and code words in a Length-Limited Variable-Length Coding (Length-Coding) system. Hereinafter, the above code is abbreviated as RLL code. In particular, the code shown in FIG. 1 is called a (2, 7) modulation method. This code handles the case where data is encoded (data words are converted into code words) and information is recorded one-dimensionally (ie, serially) with respect to time t. In such a case, normally, for example, as is well known, uneven pits are formed in a portion corresponding to the code word "1" shown in FIG. 1 and recording is performed on a recording medium.

A well-known example of a synchronizing signal is disclosed in
-48607 and JP-A-55-129914.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is
When inserting synchronization information into data in an optical disk device or the like that records data serially using LL codes,
An object of the present invention is to provide a recording / reproducing method in which data and synchronization information do not interfere with each other. It is another object of the present invention to provide a recording / reproducing method capable of preventing error propagation during decoding and performing stable correction.

[0005]

According to the present invention, data to be recorded is divided into section data having a predetermined unit length, synchronization information indicating the start is added to the beginning of the section data, and synchronization is performed in the middle of the section data. A plurality of resynchronization information different from the information is inserted, recorded on a disk-shaped recording medium, and the synchronization information and the resynchronization information are respectively detected from the reproduction signal from the recording medium to obtain the synchronization signal and the resynchronization signal. Recovery with the synchronization signal and the resynchronization signal.
The reproduction signal is decoded by controlling the encoding timing, the section data is converted into a code word by the (2, 7) modulation method and recorded on the recording medium, and the last two bits of the resynchronization information are “00”. Characterized by being recorded on a recording medium as a pattern.

Further, data to be recorded is divided into section data having a predetermined unit length, synchronization information indicating the beginning is added to the beginning of the section data, and a plurality of resynchronizations different from the synchronization information are provided in the middle of the section data. The information is inserted, recorded on a disk-shaped recording medium, the synchronization information and the resynchronization information are respectively detected from the reproduction signal from the recording medium, and the synchronization signal and the resynchronization signal are obtained. by controlling the timing of decoding decodes a reproduction signal in, characterized in that to correct errors for each section data by the error correction function attached to the data.

[0007]

In FIG. 2, reference numeral 10 denotes a synchronization signal indicating the start of recording data. Reference numeral 20 denotes a data area in which the code encoded according to FIG. 1 is recorded. Reference numeral 11 denotes a delimiter signal which is located in the middle of the data part 20 and indicates a delimiter for each fixed unit of the data part. The delimiter signal is also coded according to the RLL code coding rule shown in FIG. Separation signal 11
Has a function of synchronizing the read codewords input to the decoder at the same time as dividing the reproduced data during data reproduction. That is, when information recorded in the form shown in FIG. 2 is reproduced, decoding is started with a synchronization pulse 100 detected from a synchronization signal 10 indicating the start of recording, and a re-synchronization pulse 110 detected from a delimiter signal 11 in the middle is also synchronized with the synchronization pulse 1.
It acts as a backup for 00.

That is, the error rate of an optical disk is considerably worse than, for example, a magnetic disk. Sync pulse 10
If the decoder controlled by 0 causes a timing deviation due to noise or some other reason on the way, all data thereafter is erroneously decoded. To prevent this, even if a timing shift occurs at a place where the timing shift occurs, the timing of the decoder is returned to the normal state by the resynchronization pulse 110, so that the error due to the timing shift can be limited to only a specific section in which the shift has occurred. If the error is limited to a specific section, the error can be corrected by the error correction function added to the code. A data recording / reproducing apparatus having this kind of error correction function is described in, for example, Japanese Utility Model Application Laid-Open No. Sho 56-77018.

In order to obtain the above function, it is necessary to divide the data area into several parts, and insert a resynchronization pattern 11 at the part of the data area for recording. However, in this case, since the resynchronization pattern exists mixed with the data, it must be detected separately from the data. That is, (2,
7) The modulation method is coded so that the interval (the number of "0") of marks "1" recorded on the medium is 2 to 7, as shown in FIG. In this case, the minimum interval between marks is determined to be at least 2 from the viewpoint of reducing the mutual influence of marks and enabling stable reproduction. Therefore, the last two bits of the resynchronization pattern need to be “00”.
Otherwise, if the coded data following the resynchronization pattern starts with "1", "1" will be recorded close and may not be decomposed. It is also desirable that the resynchronization pattern itself obeys the promise that "1" is separated by two or more.

[0010] From the above viewpoint, if code conversion is performed collectively at the stage where data is divided and resynchronization information is added, the resynchronization information also conforms to the promise of the coding rule, which is convenient. By the way, in the RLL code shown in FIG. 1, when converting a data word into a code word, it is not fixed how many bits of data are converted in units for variable word length encoding. That is, coding is performed in units of 2-bit, 3-bit, or 4-bit data according to the data pattern. Therefore, when coding data of a fixed length, the data pattern causes excess or deficiency at the end of the code word.

On the other hand, the resynchronization pattern is always the same regardless of the data pattern and generates a correct synchronization pulse with a length as short as possible. It is necessary that they do not shift. Conventionally, a reliable resynchronization pattern for a variable word length code as described above and a detection method thereof have not been obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resynchronization pattern which is inserted in the middle of data with respect to a variable word length code and has a high detection reliability independently of data and a detection device therefor.

[0013]

The present invention will be described in detail with reference to the following examples.
The above-mentioned state of excessive or insufficient word division at the code word end part can be classified into the following six cases. That is, when a code word is converted into a data word, there is a case where a code word is formed at the end of the code word in some cases.

When there is no excess or deficiency When the data ends with 0 when there is one bit left When the data ends with 1 when there is one bit left When the data ends with 00 when there is two bits left The data ends with 01 when there is two bits left Case When the data ends with 001 when 3 bits are left For all of the above cases, it is impossible to obtain the same resynchronization pattern in the form of a code word, but it depends on each case. The part can be a minimum one. Further, the data pattern following the resynchronization pattern must always be a code word delimiter. There are 18 types of patterns that satisfy this condition, but in order to improve the reliability of detection, the inter-code distance between the normal timing and the pattern generated when the timing deviates from the normal must be large. From the above conditions, when the length of the resynchronization unit is 1 byte, a pattern obtained by coding the data word “10111010” according to the rule of FIG. 1 is optimal.

FIG. 3 shows how the above-mentioned resynchronization pattern corresponds to the above cases. In FIG. 3, the symbol △ indicates the location of the code word delimiter. As is apparent from the figure, two types of converted recording patterns are generated by the previous data pattern. However, if this pattern is carefully considered, the pattern shown in FIG. Further, one of the two x portions is always 1. Accordingly, the pattern shown in FIG. 3C is taken as a reference or reference pattern, the read code word is compared with the reference pattern, and if at least one of the crosses is "1", it is regarded as a match. FIG. 4 shows a comparison result when the timing is shifted in the positive and negative directions with respect to the normal timing position Δt = 0.
In the figure, d in the vertical direction is the distance between both patterns (Humming distance),
The abscissa indicates the timing shift amount Δt. As is apparent from the figure, the distance on both sides of the timing coincidence point is large, so that even if an error occurs in the read signal, a resynchronization pulse can be obtained only at a correct position in FIG. However, similar patterns can occur in the data, and to eliminate this, FIG.
A gate signal as shown in (b) is used. The gating signal is generated from a previous synchronization or resynchronization signal.

FIG. 5 shows an embodiment of the configuration of the resynchronization pattern generation circuit, and FIG. 6 shows an embodiment of the configuration of the detection circuit.

In FIG. 5, reference numeral 30 denotes write data, and reference numeral 31 denotes the resynchronization pattern (data word). The write data is compiled as a predetermined series of data words at 32 and sent to the encoder 40 with a resynchronization pattern. Encoder 40
Is coded according to the rules of FIG. The code word is provided from 51 to the write driver 50, and becomes a recording signal 61 for recording on the disk. At this time, a series of predetermined format information such as a synchronization signal is provided from the format signal generator 53 prior to data recording. As a result, it is recorded in a form as shown in FIG.

FIG. 6 is a block diagram of a reproducing apparatus. A read signal 61 from a head is converted into a signal 62 corresponding to a code word recorded by a read signal processing circuit 60. This signal is supplied to the timing recovery circuit 70, and a read clock 700 is obtained. The reproduction signal 62 is output from the synchronization signal detection circuit 7.
1,72. Reference numeral 71 denotes a synchronization signal detection circuit indicating the start corresponding to reference numeral 10 in FIG. 2, and reference numeral 72 denotes a resynchronization signal detection circuit corresponding to reference numeral 11 in FIG. The reproduction signal 62 and the two synchronization signals are supplied to a decoder circuit 80 and are converted into data words. The read clock 700 is used for synchronization detection in the synchronization signal detection circuits 71 and 72, a decoder in the decoder circuit 80, and a process in the read data reconfiguration circuit 90. After conversion into a data word by the decoder circuit 80, the read data reconfiguration circuit 90 obtains data 900 corresponding to the write data 30 in FIG. 5 except for the pattern for resynchronization.

FIG. 7 shows an embodiment of a specific configuration of the resynchronization signal detection circuit 72. 721 is a shift register, 723
724 is a reference pattern source, 726 is an AND gate, 729 is an OR gate, 73
0 is a timing generation circuit. The read signal 62 is taken into the shift register 721 by the clock 700, the pattern taken into the shift register and the reference pattern are collated by the coincidence detection circuit 723, and when they match, the coincidence signal 725
And outputs a resynchronization pulse 720 through the gates of 726 and 729. Here, the synchronization signal 710 and the resynchronization signal pass through the OR gate 729 and the timing generation circuit 73.
0 to generate a gate signal (727 in FIG. 4 (b). Even if an error or the like occurs in the read signal and a resynchronization signal cannot be detected at a normal time, the timing generation circuit 730 outputs the previous signal. A gate signal of a timing generated by the synchronization signal is generated.

[0020]

As described above, according to the present invention, the same synchronization pattern can always be used irrespective of the data pattern while using the code of variable word length coding, and its generation and detection can be easily performed. There is a feature that can be. Therefore, it is possible to minimize the influence of the timing shift due to any cause, and to improve the reliability of data reproduction.
In practicing the present invention, the data length is not limited at all, and any format configuration can be adopted as necessary.

[Brief description of the drawings]

FIG. 1 is a code diagram showing an example of a variable word length encoding method.

FIG. 2 is a conceptual diagram showing an example of a recording format of data recorded on an optical disc or the like.

FIG. 3 is a conceptual diagram showing classification of a code word pattern created from a data word pattern and a resynchronization pattern unit.

FIG. 4 is a graph showing the capability of a resynchronization pattern according to the embodiment of the present invention.

FIG. 5 is a circuit configuration diagram showing an example of a method for generating a synchronization pattern.

FIG. 6 is a circuit configuration diagram showing an example of a synchronization detection method.

FIG. 7 is a block diagram showing an embodiment of a resynchronization signal detection circuit.

[Explanation of symbols]

 10 synchronization signal, 11 separation signal, 20 data part

Claims (4)

(57) [Claims] 1. Data to be recorded is divided into section data having a predetermined unit length, synchronization information indicating the beginning is added to the beginning of the section data, and a plurality of pieces of data different from the synchronization information are provided in the middle of the section data. The resynchronization information is inserted and recorded on a disk-shaped recording medium, and the synchronization information and the resynchronization information are respectively detected from the reproduction signal from the recording medium to obtain a synchronization signal and a resynchronization signal. The reproduction signal is decoded by controlling the decoding timing with a synchronization signal and a resynchronization signal, and the section data is converted into a code word by a (2, 7) modulation method and recorded on the recording medium. An optical recording / reproducing method, wherein the resynchronization information is recorded on the recording medium as a pattern of the last two bits "00". 2. An optical recording / reproducing method according to claim 1, wherein said data has an error correction function. 3. The resynchronization information is “10111010”, and the last two bits are “0” by the (2, 7) modulation method.
3. The optical recording / reproducing method according to claim 1, wherein the code word is converted into a code word of 0 "and recorded on the recording medium. 4. The optical recording / reproducing method according to claim 1, wherein said resynchronization information is detected using a gate formed from previous synchronization information or a resynchronization signal.