JPS6299962A - Dropout detecting system - Google Patents

Abstract

PURPOSE:To prevent a correctable small dropout from being treated as a faulty product, by performing signal reproducing operations before data are recorded on an optical disk and detecting the part where levels of reproduced signals exceed a set range as a dropout. CONSTITUTION:A signal read out by means of a pickup 1 from an optical disk 12 is amplified by a preamplifier 2 and converted into a digital signal by a data slicer 3. The digital signal is supplied to a synchronizing signal detecting circuit 4 where a synchronizing signal in a pre-format signal is detected and a gate signal B corresponding to an additional area is outputted from a gate signal generating circuit 7. The output of the preamplifier 2 is converted into digital signals by slicing the output at a high level (a) and low level (b) by using level slicers 5 and 6 and a signal C is outputted through an OR gate 8. The signal C is gated by the gate signal B at an AND gate 9. A signal D outputted from the AND gate 9 becomes a signal which indicates a dropout only to the additional area.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an inspection device for an optical disc before recording digital data, and in particular, to detect dropouts that cannot be corrected even with an error correction code added to digital data. The present invention relates to a dropout detection method suitable for detecting dropouts that occur in recording media.

[Background of the invention]

Conventionally, optical disk media have been inspected by detecting dropouts on the original disk, such as by detecting the rotational position and radial size of the dropouts, as described in Japanese Patent Laid-Open No. 57-183645. was. However, no consideration has been given to improving the yield of optical disk media by determining whether the dropout is large enough to be corrected by an error correction code after additional data is written.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to correct errors caused by scratches or the like on the original disc before digital data is recorded, using an error correction code added when digital data is recorded. The object of the present invention is to provide a dropout detection method that makes it possible to determine whether or not the level of dropout is acceptable.

[Summary of the Invention] ' In order to achieve this object, the present invention performs a signal reproducing operation on recorded digital data, and checks the level of the reproduced signal only for the part where the signal is recorded, and determines whether the recorded signal is recorded or not. The feature is that a high level and a low level are set for a signal level that does not exist, and a portion exceeding the range set by these levels is detected as a dropout.

Optical discs have a high bit error rate compared to optical discs.
For that purpose, D A D (DigitαlAμdi.

A code with high error correction ability is generated and added along with the data, such as a disk. For code generation, a method such as interleaving that changes the arrangement of time-series data is used, so that even if data is continuously missing due to dropouts of a certain length, it can be corrected. .

Furthermore, for optical discs on which additional data can be written, in order to increase the reliability of the data to be additionally written, it is necessary to check in advance for dropouts caused by scratches, scratches, etc. before additionally writing data.

At this time, as mentioned above, if the dropout is of a certain length, when added using the error correction code,
Data that could not be recorded due to scratches etc. can be corrected and played back.

Therefore, when inspecting the disk before additional writing, it is sufficient to detect dropouts that cannot be corrected by taking into account the ability of the error correction code.

As described above, the present invention detects a defective disk by detecting uncorrectable dropouts on an optical disk before additional writing.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the dropout detection method according to the present invention, in which 1 is a pickup, 2 is a preamplifier, 6 is a data slicer, 4 is a synchronization signal detection circuit, and 5 and 6 are dropout detection circuits. Level slicer for 7
1 is a gate signal generation circuit, 8 is an OR gate, 9 is an AND gate, 10 is a synchronization signal detection signal terminal, 1] is a dropout detection signal terminal, 12 is a recordable original disk, 13
is a disk rotation motor.

FIG. 2 is a timing diagram for explaining the operation of the embodiment of the present invention.

In FIG. 1, the original disk 12 is rotated by the moco 13, and the pickup 1 is rotated! The detected signal is amplified by a preamplifier 2 and supplied to a data slicer 6 and a dropout detection level slicer. Preamplifier 2 above
The output signal waveform of is shown in FIG. 2(A).

The optical disc used here uses a sector format in which the track is divided into multiple blocks and pre-recorded preformatted signals such as a synchronization signal, track address, and block address at the beginning of each block. . Therefore, originally, when this original disc 12 is reproduced, only the preformat signal should be output. However, if there is a scratch on the original disc 12, dropout occurs as shown in the additional write area E-2 in FIG. 2 (A1).

The reproduced signal resulting from this dropout is converted into a digital signal by the data slicer 6 shown in FIG. The generated gate signal [B1 is outputted from the gate signal generation circuit 7 and inputted to one of the A t'JD gates 9.

In addition, the output j4 of the preamplifier 2 enters the level slicer 5, and is sliced at levels α and b shown in FIG.
The signal enters the R gate 8 and outputs a signal having the waveform shown in FIG. 2(C). This signal (CI contains a brief format signal in addition to the signal indicating dropout, so
The AND gate 9 converts the signal (B
) to apply a gate. Therefore, AND gate 9
As shown in Figure 2 (D), the signal output from
A signal indicating only dropout for the additional write area is obtained from terminal 1].

FIG. 3 is a block diagram showing an example of a dropout determination circuit in the dropout detection method according to the present invention. Reference numerals 9 and 10 are connected to terminals 9 and 10 in FIG. ), terminals to which the dropout detection signal (D) is input, 14 , 22 , 23 ,
24 and 25 are counters, 15 is a decoder, 16 is an inverter, 17 is a clock input terminal for dropout counting, 18, 19, 20, and 21 are six-manual AND gates, 26 is a demarder, and 27 is a signal for determining the quality of the optical disc. It is an output terminal.

In the figure, when a synchronization signal detection signal is input to terminal 9, counters 14, 22, 23, . . . are cleared. When a dropout detection signal indicating that dropout has been detected is input to terminal 10, counter 1
4 is counted up, the output goes into the decoder,
Each is decoded from 0 to the number of the counter that measures the length of the dropout. There are two or more counters 22, 23, .
Make it firm. The counters are operated by the decoder 15 so that the length of the 9th toe 11th dropout is measured by the counter 22, and the length of the 2nd dropout is measured by the counter 23. For this, AND
Gates 18 and 19 are used to connect the output of decoder 15 to the clock signal used to measure the dropout length.
For example, the operation of the counter is controlled by applying a gate using the signal 1F) in FIG. 2 and the dropout detection signal (D). Therefore, a clock is input to the counter 22 only at the ANDed portion of the signals (G and G), and the length of the dropout P can be measured.

Furthermore, the dropout interval can be measured in a similar manner. This is a counter fable.

Do it at 25. For example, for a counter, it is sufficient to measure the length between dropouts P and Q of the dropout detection signal (D+. Therefore, the measurement clock is the signal (D) inverted by the inverter 16 and the decode signal (Fl). The input of the clock to the counter 24 is limited and measured by applying a siggate to the ANDtl-AND gate 20.

The above is an example of a method for measuring the length and interval of dropouts. Each output of counters 22 to 25 enters a decoder 26. This decoder determines whether or not the data recording can be corrected based on the length and interval of dropouts, based on the ability of the error correction code added when recording data. If it is out, a signal indicating that recording is not possible in the corresponding sector is output from the terminal 27.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to detect dropouts that occur in a portion to be additionally recorded on a recordable optical disc before recording data, and furthermore, it is possible to detect dropouts that occur in a portion to be additionally recorded on a recordable optical disc, and furthermore, to By measuring the distance between dropouts and determining whether or not they can be corrected using the error correction code added when recording data, small dropouts that can be corrected will not be considered defective. Therefore, the yield of optical disks can be improved, and a dropout detection method with excellent functions can be provided without the drawbacks of the above-mentioned prior art.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the dropout detection method according to the present invention, FIG. 2 is a timing diagram for explaining the operation of the embodiment of the present invention, and FIG. 6 is a dropout detection method according to the present invention. FIG. 2 is a block diagram showing an example of a dropout determination circuit in FIG. 1...Pickup...Brieamp 6...
・Data slicer 4...Synchronization signal detection circuit 5.6
・Level slicer for dropout detection 7 ・Gate signal generation circuit 8 ・OR gate 9 ・AND gate 1
0... Synchronous signal detection signal terminal 1]... Dropout detection signal terminal 12... Original recordable disk 13... Disk rotation motor 14. 22-25... Counter 15, 26...
・Counter 15.26...Decoder 16...
・Inverter 17...Clock input terminal for dropout count

Claims (1)

[Claims] (1) In a dropout detection method for an optical disc before digital data is recorded, a high level and a low level are set for the playback level of the part where the digital data is recorded, and the optical disc is used for recording the digital data. A portion where the playback level obtained from the previous playback operation exceeds the range set by the high level and low level is detected as a dropout, and the error is corrected using an error correction code added when recording the digital data. A dropout detection method is characterized in that it is configured to be able to determine whether or not a dropout is possible.