JPS6318523A - Defect inspection system for additional description type optical disk - Google Patents

Abstract

PURPOSE:To inspect the disk in a short time and to detect a long burst defect by adopting the rotational speed of an additional write type optical disk not recorded yet at the defect inspection faster than the rotational speed at write or readout. CONSTITUTION:A driving motor 6 is controlled so as to rotate an optical disk 1 at a faster rotational speed than a conventional speed. A laser beam projected from a pickup onto the optical disk is reflected on a pre-group and the reflected light generates an output signal by a photoelectric transducer in the pickup, and when the signal level reaches an amplitude representing the presence of a defect by a level detector 7, a defect detection signal is applied to a disk driver 4 and a signal generator 8, the disk driver 4 increases the intensity of the laser ray of the pickup 5 to the write level and a signal generator 8 supplies the error flag write signal to said pickup to write an error flag to the ID part of the sector having a defect and no data is written onto said sector.

Description

[Detailed Description of the Invention] [Summary] In a defect inspection method in which a read-mode laser beam is irradiated onto the recording portion of a write-once optical disk and defects on the disk are detected by the reflected light, the rotation of the disk during this defect inspection is By making the speed faster than the rotational speed when writing or reading data, burst defects can be detected and the time required for inspection can be shortened.

[Industrial application field]

The present invention relates to a defect detection method for a write-once optical disc, in which a write-once optical disc is rotated while a recorded portion thereof is irradiated with a laser beam in a read mode, and defects on the disc are detected based on the reflected light.

[Conventional technology]

FIG. 2 is a diagram showing a state before data is recorded on an example of a write-once optical disc, and a data recording section provided subsequent to an ID section (sector identification section) indicating a sector address etc. has a section for tracking control. Pre-group (guide groove)
is preformed and data is recorded at the bottom of this pregroup.

FIG. 2(b) is a cross-sectional view of the pregroup P shown in FIG. The areas shown are defective areas where the recording film is applied thickly, and data cannot be recorded correctly in such defective areas.

Conventionally, one method for accurately recording data is to read the recorded data immediately after recording the data, compare the read data with the recorded data, and check that there is no error by comparing the read data and the recorded data. However, if an error is found in multiple recorded sectors, recording must be performed again in a pre-prepared replacement sector, and replacement sectors that are not necessarily used are prepared. Not only is it necessary to store data, but data equivalent to the storage capacity of the data buffer used for recording is recorded at one time, so for example, if this storage capacity is for 20 sectors, these 20 sectors are recorded from the sector where recording started. It is necessary to provide this replacement sector later, and even if recording is performed in this way, as shown in Figure 3(a), the recorded data will not be arranged in the correct order. However, there are drawbacks such as extra access time required to read the data, or unnecessary processing added to the processing of the read data.

In order to eliminate such defects, write-once optical discs are inspected for defects before recording.
One method is to irradiate the recorded area with a laser beam in read mode while rotating the disk to be inspected and detect the reflected light as shown in Figure 2 (C), and the output based on the reflected light is A'. As shown, it decreases in the area where the recording film was not applied, and as shown in B', it increases in the area where the recording film was thickly applied, and when these values exceed predetermined values, the recording area Detecting the presence of defects is being carried out.

In this way, for sectors in which a defect is detected in the recording part before recording, an error flag is written in the ID section of the corresponding sector to prevent writing to that sector when data is recorded. By doing this, it is possible to skip the defective sector and write to each sector in sequence, as shown in Figure 3Cb).However, by combining the inspection for the presence of defects with the data recording sequence, it is possible to record into each sector in sequence, skipping the defective sector. When executed, the write processing time becomes extremely long, and if the entire surface of the optical disk is inspected before it is used, a long inspection time is required.

In addition, in the case of the inspection method explained with reference to FIG. 2, if the inspection is performed using the rotational speed used for writing or reading, defects with a length similar to the length of a recording pit can be easily detected; For burst defects that are significantly longer than the bit, the amount of change in the reflected light is small compared to the length, so the change in detection output due to this burst as shown in Figure 2 (TC) is extremely low. Since it exists in a frequency band, it has been difficult to detect it due to the detection ability of a detector based on the frequency characteristics of an amplifier.

(Problems to be Solved by the Invention) The present invention provides a defect inspection method for write-once optical discs, which inspects the recorded portion for defects using a laser beam in the read mode before using the write-once optical disc, as explained with reference to FIG. The present invention aims to provide a defect inspection method that shortens the time required for inspection and makes it possible to detect long burst defects.

[Means for solving problems]

The present invention makes it possible to inspect the disk in a short time by setting the rotational speed of an unrecorded write-once optical disk at the time of defect inspection to a faster rotational speed than the rotational speed at the time of writing or reading. This made it possible to detect long burst defects.

In order to switch the rotational speed, as shown in FIG. This can be achieved by providing a rotating speed control means C for switching.

[For production]

In a defect inspection method, which is the subject of the present invention, in which defects are detected by tracking the recording trunk while rotating a write-once optical disk, the time required for inspection can be shortened by increasing the rotational speed of the optical disk. does not require any special explanation.

However, when inspection is performed at such a high rotational speed, the minimum size of a detectable defect increases. In other words, the minimum value of the readable size at the rotational speed used for recording or reading is the M T of the optical system.
F (Modulation TransferFun
Assuming that it is 1 μm due to constraints such as ction),
For example, the minimum value that can be read at a rotational speed 100 times that value is 1100 cr, which is 100 times that value, and defects having a length shorter than this cannot be detected.

By the way, what needs to be detected as a defect in such a write-once optical disc is a defect that prevents recorded data from being reproduced correctly. It will be clear that if data is available, there is no need to detect it as a defect. As such an error correction means, for example, an error correction method disclosed in Japanese Patent Application Laid-open No. 143485/1985 is capable of completely correcting burst errors of about 200 bits. Therefore, if the minimum readable size at the rotational speed used for recording and reading is 1 μm, by applying the error correction method described above, there is no need to detect burst defects of 200 μm or less, and this inspection The rotational speed of the optical disk during reading can be changed to about 200 times the rotational speed during normal reading.

As described above, the rotational speed of the write-once optical disk during defect inspection in the present invention is determined by taking into consideration the minimum size of the burst defect to be detected and the error correction method to be used.

〔Example〕

FIG. 4 is a block diagram showing an embodiment of the present invention in which a write-once optical disc is inspected for defects when it is loaded into a recording/reproducing mechanism.

When the write-once optical disc l is loaded, the disc sensor 2 sends a signal indicating that this optical disc is present at a predetermined position to the disc loading detector 3, and this detector detects that loading of the disc is completed. When the disk driver 4 receives this signal and sends out a loading end signal, the disk driver 4 sends out a light intensity switching signal that controls the pickup 5 to project a laser beam of the read mode light intensity onto the optical disk, and at the same time, the rotation speed is increased from the normal rotation speed. The rotation drive motor 6 is controlled to rotate the optical disc 1 at a rotation speed for fast inspection.

The laser beam projected from the pickup onto the optical disk is reflected by the pre-group, and this reflected light is generated by the photoelectric conversion element in this pickup to generate an output signal as shown in FIG. When the signal level reaches an amplitude indicating the presence of a defect, a defect detection signal is applied to the disk driver 4 and the signal generator 8, and the disk driver 4 increases the intensity of the laser beam of the pink-up 5 to a writing level; At the same time, the signal generator 8 supplies an error flag write signal to this pickup to write an error flag in the ID section of the sector in which the defect has been detected, thereby preventing data from being written to this sector.

The slice circuit 9 shown in FIG. 4 shapes the normal read signal and supplies the data recorded on the optical disc to a reading means (not shown) including a processor, for example. Needless to say, the above-described inspection of the write-once optical disc and normal recording/reading control are performed by a control means such as a processor (not shown).

〔Effect of the invention〕

According to the present invention, the time required to inspect a write-once optical disc for defects can be reduced to, for example, about 1/200, and the data read from the write-once optical disc can be accurately recorded and processed by error correction processing. Since defects that can be reproduced are not detected as defects, the recording capacity of the write-once optical disk can be substantially increased by using the recorded portions having such undetected defects for recording, which is a special effect. be able to.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the present invention in detail, FIG. 2 is a diagram explaining recording/reading of a write-once optical disc, FIG. 3 is a diagram conceptually explaining the data recording state, and FIG. 4 is a diagram explaining the present invention. FIG. 1 is a block diagram showing main parts of an embodiment of the invention. ai [I15-Sugi' Rentanuki 1st figure (b) (.) °C M'6 Otsu-type Men-1 suri no War0 Riku: Shitsuto 8 Jbis Sh% Dh guy 1 damn figure 2

Claims (1)

[Scope of Claims] A write-once optical disc in which a read-mode laser beam is irradiated onto the recorded portion of the optical disc while the write-once optical disc is rotated, and the disc is inspected for defects based on the detected reflected light from the optical disc. A defect inspection method for a write-once optical disk, characterized in that the rotational speed of the disk during the inspection is faster than the rotational speed during data writing or reading.