JPH02247824A - Detection of data abnormality of optical disk device - Google Patents

Abstract

PURPOSE:To improve the reliability of reproduction data by detecting the output time difference between the front edge and rear edge of pits and outputting an error signal when the difference is off a prescribed range. CONSTITUTION:A reading out signal 103 of an optical disk by a pit edge recording system is inputted to an edge detecting circuit 106. The circuit 106 outputs detection signals 107, 108 of the front and rear edges of the recording pits respectively to VOF circuits 109, 110. The circuits 109, 110 output detection signals 111, 113 in synchronization with synchronizing clocks 112, 114. A data synthesizing circuit 115 forms a reproduction signal 117 in synchronization with the clocks 118. On the other hand, the signals 111, 113 are simultaneously subjected to the measurement of the time difference therebetween by a circuit 116 for deciding the fluctuation in the recording pit length. An error signal 119 and a correction value signal 120 are outputted when the value thereof is decided to be off the prescribed range. The signal 120 is outputted according to the deviation from the prescribed of the time difference to correct the writing conditions of the pits.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data abnormality detection method for an optical disc device suitable for determining whether data has been accurately recorded on an optical disc.

[Conventional technology]

FIG. 5 is a waveform diagram for explaining a conventional method of binarizing a read waveform from an optical disc.

In FIG. 5, waveform portions 503 and 504 indicate drop-in and drop-out waveform shapes that may be erroneously binarized. That is, the read waveform 500 is binarized using the slice level 505. In the readout waveform 500, the dropout or dropin waveforms 503 and 504 described above may occur due to dust present on the optical disk or the influence of the detection system.

In the prior art, as disclosed in Japanese Patent Application No. 58-209032, for example, if the peak value of the readout waveform 500 is between levels 501 and 502, there is a risk that it will be erroneously binarized. The system determines that the waveform is abnormal, rewrites the same data in a different area in place of the sector where the abnormality occurred, and confirms that there is no abnormality again to ensure normal data reproduction.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, if the method for writing information on an optical disc is a method in which information is written on the optical disc according to the length of pits (usually called a pit edge recording method), the sensitivity of the optical disc, the circuit system, the optical system, etc. There is a problem in that even if there is a large variation in recording focus length, it cannot be determined that this is abnormal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable method for detecting data abnormality in an optical disk device by detecting data recording in which the pit length is abnormal in a pit edge type optical disk device.

[Means to solve the problem]

The data abnormality detection method for a magnetic disk device of the present invention detects the leading edge and trailing edge of a pit from a read signal read from an optical disc, and the output time difference between the detected leading edge and trailing edge is within a predetermined range. If it is determined that the data is outside a predetermined range, the written data is determined to be abnormal and an error signal is output.

[Operation] According to the present invention, during read-after-write, the leading edge and trailing edge of a pit are detected from the read signal read from the optical disk, and the time difference between the output timing of the leading edge and trailing edge is determined. It is determined from the time difference whether the data is within a reproducible range. If it is determined that the data is in a non-reproducible range, it is determined that data writing has failed, and an error signal and write conditions such as write power and write pulse width correction values are output.

This makes it possible to determine whether data has been accurately written to the optical disc.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, recorded data recorded as pits on an optical disk 101 is converted into a read signal 103 by an optical head 102. As shown in FIG. 2, the formation of the recording pit 202 begins when the recording data 201 becomes "1", and then the formation ends when the recording data becomes "1", and the same process continues thereafter. formed by the process. Therefore, the recording pit 202 is formed in the shape of a long hole.

Hereinafter, this method will be referred to as a pit edge recording method.

Note that, as shown in FIG. 2, data SD in a specific format is added to the beginning of the recorded data 201.

The data SD in the specific format is followed by data that should originally be recorded. Here, the pattern format and number of pits of the specific format data SD may be arbitrary. The read signal 103 is amplified by an amplifier 104 and input as a read signal 105 to an edge detection circuit 106. As shown in FIG. 2, the edge detection circuit 106 detects the front edge and the rear edge of the recording pit 202, separates the two, and generates a front edge detection signal 107 and a rear edge detection signal 108.
The signals are output to VFO circuits 109 and 113, respectively. 'The VFO circuit 109 receives the previous edge detection signal 107 and outputs a read synchronization clock 112 and a previous edge detection signal 111 synchronized therewith. Similarly, the VFO circuit 1i3 receives the trailing edge detection signal 108 and outputs a read synchronization clock 114 and a trailing edge detection signal 113 synchronized therewith. The data synthesis circuit 115 has a read synchronization clock 1
12, 114, a front edge detection signal 112, and a rear edge detection signal 113, a reproduction signal 117 synchronized with a clock 118 is formed as shown in FIG.

Further, the front edge detection signal 107 and the rear edge detection signal 113 outputted from the edge detection circuit 106 are input to a recording pit length variation determination circuit 116, as shown in FIG. The recording pit length variation determination circuit 116
Regarding the data SD of the specific format shown in the figure, as shown in FIG.
The input time difference Te of 8 is measured and it is determined whether the time difference Te is within a predetermined range. For example, the input time difference Te is (T-Tb/2)<Te< (T+Tb/
It is determined whether or not it is within the range of 2). Here,'r
indicates the period of the front edge detection signal and the rear edge detection signal set in advance, and Tb is a value indicating the permissible range thereof. If the time difference Tb is determined to be within a predetermined range, it is determined that the record data has been written normally. In addition, if it is determined that it is outside the predetermined range, the error signal 11
9 and a correction value signal 120 are output. Correction value signal 120
is the focus writing conditions (power setting, pulse width setting, etc.)
This is a signal for correcting the time difference To, and is output according to the amount of deviation of the time difference To from a predetermined value.

In FIG. 3, when the trailing edge detection signal 10B is output at timing 301, it is determined to be normal. Further, the trailing edge detection signal 108 is 302, 30
If it is output at timing 3, it is determined that there is an error, and the error signal 119 and correction value signal 120 are output.

FIG. 4 is a block diagram showing a specific example of the recording pit length variation determination circuit 116 shown in FIG. 1.

As shown in FIG. 4, the electronic recording pit length variation determination circuit 116 includes a counter 401 for measuring the time difference Te between the front edge detection signal 107 and the rear edge detection signal 108, and a variation determination circuit 402. There is. The counter 401 starts counting upon receiving the front edge detection signal 107, and stops counting upon receiving the rear edge detection signal 10B. The counted time difference Te is input to the variation determination circuit 402, and it is determined whether or not it is within a predetermined range. If it is determined that the value is outside the predetermined range, the error signal 119 and correction value signal 120 are output as described above.

The variation determination circuit 402 includes a memory that records correction values such as the light irradiation power and the pulse width of the optical pulse corresponding to the value of the time difference Te, and outputs the correction value signal 120 by reading the correction values from this memory. do.

Note that in the above embodiment, the edge detection circuit 106
Although the front edge detection signal 107 and the rear edge detection signal 108 outputted from the recording pit length variation determination circuit 116 are inputted to the recording pit length variation determination circuit 116 to determine whether or not data recording has been performed accurately, the present invention is not limited to this. For example, V
Pre-esocine output signal 11 output from the FO circuit 109
1 and the trailing edge detection signal 113 output from the VFO circuit 113 may be input to the recording pit length variation determination circuit 116.

As explained above, according to this embodiment, the lead
It becomes possible to accurately check the dispersion of recorded pits during after-write, improve the quality of data writing, and ensure normal data reproduction.

[Effects of the Invention] According to the present invention, the quality of data written on an optical disk can be sufficiently guaranteed, and therefore the reliability of reproduced data can be greatly improved.

In addition, even if there are large variations in recording pit length caused by the sensitivity, circuit system, optical system, etc. of the optical disc,
Since data quality can be sufficiently guaranteed, it is also effective in ensuring data compatibility.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG.
3 is a waveform diagram for explaining the operation of the recording pit length variation determination circuit shown in FIG. 1, FIG. 4 is a block diagram showing a specific example of the recording pit length variation determination circuit shown in FIG. 1, and FIG. The figure is a waveform diagram for explaining a method of binarizing a read signal from an optical disc using a conventional technique. 101... Optical disk, 102... Optical head, 1
03... Read signal, 104... Amplifier, 106...
- Edge detection circuit, 107, 111... Front edge detection signal, 108.113... Back edge detection signal, 109
．． 113-V F 0 circuit, 115-data synthesis circuit,
116... Recording pit length variation determination circuit, 119.
...Error signal, 120...Correction value signal. Agent Patent Attorney Tadashi Akimoto Jitsuzu Takayo-,)202 C=======)(22=2==
=) (===========:) Signal 203 - 1 ゜ 11 ゛ (Exit 108 Re-summary)] 7 Fig. Condolences Island - 采ふ

Claims (1)

[Claims] 1. Detect the leading edge and trailing edge of the pit from the readout signal read from the optical disk, determine whether the output time difference between the detected leading edge and trailing edge is within a predetermined range, and A data abnormality detection method for a magnetic disk device, characterized in that when it is determined that the data is out of range, the written data is determined to be abnormal and an error signal is output.