JPH0471271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a method for recording and reproducing information on an optical recording disk having an optically detectable guide track and in which the guide track is divided in advance into a plurality of sectors. The present invention relates to an optical information recording and reproducing method.

Conventional configurations and their problems For optical recording disk memories that are considered promising as high-density, large-capacity memories, error control technology is extremely important to overcome the low error rate of optical recording disks.

Optical recording disks usually have optically detectable guide tracks such as guide grooves to achieve high track density, and a laser beam focused to about 1 μm is applied to the recording layer formed on the guide tracks. Irradiate it, make a hole, or cause a change in reflectance and record it.

Recording dots and track pitches are approximately 1 μm, so various defects may occur depending on the optical recording disk manufacturing process guide, track formation, replica disk manufacturing, recording material deposition, protective layer formation, and the usage environment of the optical recording disk. , dust, and scratches occur, resulting in a dropout of the playback signal. These dropouts come in a variety of forms, including burst-like ones,
Random things occur to the same degree. As a result, the raw error rate of optical recording disks is between 10 ^-4 and 10 ^-6.
This is said to be extremely poor compared to the raw error rate of 10 ^-9 to 10 ^-12 for magnetic disks, which are typical conventional recording media.

For this reason, optical information recording and reproducing apparatuses using optical recording disks usually have strong error control, as shown in FIG.

In FIG. 1, 1 is a data buffer memory for temporarily storing user data to be recorded;
2 is an error detection and correction circuit, 3 is a sector buffer memory for storing encoded data to be recorded in sectors of the optical recording disk, 4 is a modulation circuit, 5 is a demodulation circuit, and 6 is an optical recording disk drive. An optical recording disk is a so-called sector format disk in which a guide track is divided into a plurality of sectors in advance.

FIG. 2 is a diagram showing details of the format of the modulated output 100 of the modulating circuit 4. As shown in FIG. 7 is a synchronization signal for prompting clock synchronization during clock reproduction, 8 is a data mark, and 9 is encoded data encoded by the error detection and correction circuit 2. Recording signal block B consisting of synchronization signal 7, data mark 8, and encoded data 9 is recorded in sectors divided by address section A, as shown in FIG. Address part A records track addresses and sector addresses.

In the sector format shown in FIG. 2, word synchronization of the reproduced signal 101 of the subsequent encoded data shown in FIG. 1 or phase synchronization with the reproduced clock is achieved using the data mark 8. If a dropout occurs in 101 and these synchronizations are lost, there is a possibility that all subsequent demodulated data will be in error.

RLL (RUN LENGTH) converts M-bit data to N-bit modulation code for high-density recording.
LIMITED) code modulation, for example, 4/5 or 4/8 modulation, it is necessary to demodulate the reproduced signal 101 into M bits by dividing data mark 8 and subsequent N bits at the time of demodulation. Therefore, the playback signal 1 is generated by the dropout of the optical recording disk.
If word synchronization is lost due to the omission of data mark 01, this synchronization will continue until the next data mark 8 is input, resulting in a long burst error.

In order to reduce burst errors caused by word synchronization errors, a recording signal format as shown in FIG. 4 is used. In Figure 4,
7 and 8 are the same synchronization signals and data marks as in FIG. 10 is a segment obtained by dividing the encoded data
SEG1, . . . , SEGm constitute frames F1, F2, . . . Fm with data mark 8 and segment 10.

By structuring the modulation signal in a frame in this way, even if word synchronization is lost during demodulation, resynchronization occurs at the beginning of the next frame, reducing burst errors caused by word synchronization to less than the frame length. Can be restricted.

When using a frame configuration, countermeasures must be taken when data marks cannot be detected due to dropouts or the like.

To demodulate data recorded in the frame configuration shown in FIG. 4, after detecting a data mark, the demodulator 5 shown in FIG. Stores a considerable amount of data. Thereafter, data corresponding to one frame is stored repeatedly every time a data mark is detected. In this way, one sector's worth of demodulated data is stored in the sector buffer memory 3.

When demodulating data using this method, if the data mark of a certain frame cannot be detected, the data of that frame is not stored in the sector buffer 3, and the demodulated data of the next frame and subsequent frames is
Since the data is stored at a different address than the one where it should be stored, all the data will be incorrect.

FIG. 5 shows how the address at which demodulated data is stored in the sector buffer 3 shifts when data mark non-detection occurs.

First, as shown in FIG. 5a, data corresponding to frames F1, F2, ...Fm is stored in the sector buffer 3, and then the modulated data is recorded on the optical disk by the modulator 4 shown in FIG. It shall be assumed that Thereafter, if the data mark of frame F3 is not detected during data demodulation, the demodulated data of F3 is not stored in sector buffer 3.
Furthermore, the data of F4 is stored at the address where the data of F3 should originally be stored. Similarly, the data of F5 is stored at the address where the data of F4 should originally be stored. In the same manner, the data storage address is shifted by an amount equivalent to one frame. Therefore, all data below F4 is erroneous.

In this way, if a data mark is not detected when reproducing data recorded using a frame structure, two countermeasures can be considered.

One method is to use a frame counter, and the other is to insert a frame number into a segment in the frame structure shown in FIG.

First, a method using a frame counter will be explained. This method counts the number of frames each time a data mark is detected during data playback,
Also, when the data mark is not detected after the data mark has passed the frame period, the counter number is increased.
1, and by updating the storage address of the sector buffer memory 3 in accordance with the output of the frame counter, it is possible to prevent the storage address of demodulated data from shifting when no data mark is detected.

This method is characterized in that when no data mark is detected after a frame period has elapsed, it is assumed that no data mark has been detected, and the count number of the counter is increased to +1. However, in reality, the frame period becomes longer or shorter due to eccentricity caused by replacing the disk or fluctuations in the rotation of the disk motor.
When the data mark is not detected even after a period equal to the average value of the frame period plus the maximum value of the variation has elapsed, it is necessary to consider that the data mark has not been detected.

For this reason, as the number of frames increases and the average value of the frame period approaches the order of magnitude of variation in the frame period, a malfunction may occur in which it is assumed that the data mark has not been detected before the correct data mark has been detected. becomes more likely to occur.

Next, a method of inserting a frame number into a segment (data portion) within a frame will be explained.
FIG. 6 shows the recording signal format of this method. In FIG. 6, 7 and 8 are the same synchronization signals and data marks as in FIG. 2. 10 is a segment SEG1 obtained by dividing the same encoded data as in Fig. 4,...
In SEGm, 11 is the frame number. With data mark 8, frame number 11 and segment 10,
Frames F1, F2, ... constitute Fm.

This method does not depend on the number of frames, and no matter how many data marks cannot be detected, once a data mark is detected, the frame number is read and the data of that frame is stored at the correct storage address in the sector buffer memory. can do. However, if the frame number is read incorrectly, data will be stored at the wrong storage address in the sector buffer memory.

Therefore, countermeasures against frame number reading errors are necessary, but reading frame numbers is a process that occurs before data error correction, and data storage starts immediately, so there is plenty of time to correct errors. Less is.

OBJECTS OF THE INVENTION The present invention provides an optical information recording and reproducing method that is resistant to word synchronization caused by dropout of an optical recording disk and that does not cause shifts in the address at which demodulated data is stored in a sector buffer memory. The purpose is to provide.

Composition of the Invention The present invention records a modulated signal consisting of a plurality of frames on a sector-structured optical recording disk, and each frame is formed by adding a frame number with an error detection code to encoded data divided into segments. By using a recording signal format with a data mark at the beginning, word synchronization errors when a dropout occurs can be corrected with the data mark of the next frame. By reading the frame number, the modulated data is stored at the correct address in the sector buffer memory.

DESCRIPTION OF THE EMBODIMENTS FIG. 7 shows the format of a modulated signal recorded in a sector of an optical information recording apparatus according to an embodiment of the present invention.

In the figure, 7, 8, 10 are segments SEG1, ..., SEGm obtained by dividing the same synchronization signal, data mark, and encoded data as in FIG. 6, and 12 is
This is a frame number with an error detection code attached. Frame number 11 and segment 10 with data mark 8 and error detection signal, frames F1, F2,...
..., constitutes Fm.

By using such a frame structure, even if word synchronization is lost during demodulation, resynchronization will occur with the data mark of the next frame, so burst errors caused by word synchronization can be limited to less than the frame length, and playback Even if there is a frame in which no data mark can be detected, the encoded data of subsequent frames can be stored at the correct address in the sector buffer memory.

FIG. 8 is a block diagram of an apparatus for generating a sector recording modulation signal according to the present invention, and FIG. 9 is a block diagram of an apparatus for demodulating reproduced data and storing it in a sector buffer memory.

In FIG. 8, 13 is a sector buffer memory, 14 is a modulator, 15 is a modulation timing generation circuit, 16 is an address counter, 17 is a data mark generation circuit, and 18 is a frame that generates a frame number with an error detection code. This is a number CRCC generation circuit. 19 is a multiplexer, and 20 is a parallel-to-serial conversion circuit.

The operation of the sector recording modulation signal generating device configured as above will be explained below.

Data written in the sector buffer memory 13 is sequentially read out by a modulation timing generation circuit 15 and an address counter 16, and is modulated by a modulator 14. The output of the modulator 14 is, as shown in FIG. The attached frame number is added by switching the inputs X, Y, and Z of the multiplexer 19, converted into a serial modulation signal by the parallel-to-serial conversion circuit 20, and outputted to the optical disk drive.

FIG. 10 is a timing chart for adding frame numbers with the above-mentioned data marks and error detection codes. A data mark and a frame number with an error detection code are added to each segment by the data mark gate signal 81 of the modulation timing generation circuit 15, the frame number gate signal 82 with an error detection code, and the multiplexer switching signal 83. , create a modulated signal consisting of frames F1, ..., Fm.

Next, data demodulation will be explained using FIG. 9.

A reproduction signal 91 from the optical recording disk is applied to a clock reproduction circuit 21 and a serial/parallel conversion circuit 22. The clock recovery circuit 21 extracts a recovered clock 92 from the reproduced signal 91 using a phase-locked loop (PLL) circuit. The reproduced signal 91 is transmitted to the serial/parallel converter circuit 22 by the reproduced clock 92.
be taken in. The output of the serial-parallel conversion circuit 22 is input to a demodulator 23 and a data mark detector 24. When the data mark detector 24 detects a data mark, the reproduction timing circuit 25 is activated, the demodulator 23 is activated, and first, the frame number with the error detection code is latched. A CRCC check circuit 27 that performs error detection performs frame number error detection. Only when no error is detected, an address corresponding to the frame number is set in an address counter 28, and thereafter one frame's worth of demodulated data is stored in a sector buffer memory 13 in accordance with the reproduction code clock of a reproduction timing circuit 25. By detecting frame number errors,
When an error is detected, the demodulated data is not stored and waits until the data mark detection circuit 24 detects the data mark again.

As explained above, according to this embodiment, the modulated signal to the sector is configured as a frame, and a frame number with an erroneous detection code is added to each frame. This prevents demodulated data from being stored at the wrong address in the sector buffer memory by limiting burst errors to the next frame and detecting frame number errors when a data mark is detected. be able to. Error correction is difficult to use due to limited time, but error detection can be detected with sufficient performance without increasing redundancy.

For example, as a code for error detection,
GOLAY CODE is very suitable.

Effects of the Invention As explained above, the optical information recording and reproducing method of the present invention uses sectors as frames and adds a frame number with an error detection code to each frame, thereby preventing word synchronization errors caused by dropouts. This can be limited to the next frame, and can also prevent demodulated data from being stored at an incorrect address in the sector buffer memory.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a general optical information recording/reproducing device, FIG. 2 is a format diagram of a modulation signal recorded in a conventional sector, and FIG.
FIG. 4 is a diagram showing the arrangement of sectors recorded on the guide track of an optical recording disk. FIG. 4 is a diagram showing the format of a modulation signal for sector recording in a frame structure. FIG. A diagram showing how the addresses of demodulated data stored in the memory shift, FIG. 6 is a format diagram of a modulated signal with a frame number added to each frame, and FIG. 7 is an optical information recording diagram according to an embodiment of the present invention. FIG. 8 is a block diagram of a device for generating a sector recording modulation signal in the present invention; FIG. 9 is a block diagram of a device for demodulating reproduced data in the present invention; FIG. 10 is a timing chart showing the timing of adding frame numbers with data marks and error detection codes. 7...Synchronization signal, 8...Data mark, 10...
...Segment, 12...Frame number with error detection code attached.

Claims (1)

[Claims] 1. An optical disk having an optically detectable guide track, in which the guide track is divided into a plurality of sectors, the data to be recorded in the sector is divided into a plurality of segments, the segments are serially numbered, and the An error detection code is added to the serial number and added to the segment, a data mark indicating the start of data is placed at the beginning of the segment to which the serial number attached to the error detection code is added, and a data mark indicating the start of data is placed immediately before the data mark for regenerating clock pull-in. The data in the sector is recorded as a set of frames, and during playback, the data mark is detected and the serial number with the error detection code is read out. An optical information recording and reproducing method characterized by storing frame reproduction data in a memory.