JPH01253638A - Defect checking apparatus for disk-shaped optical recording medium - Google Patents

Abstract

PURPOSE:To improve reliability in checking serious defects, by scanning information tracks for every specified tracks in a skipping mode, detecting the position information at the time of occurrence of the defect at a value smaller than a normal checking reference value, and rechecking all the tracks before and after the position where the defect has occurred. CONSTITUTION:A reference value WC is set so that the magnitude of a defect is smaller than a normal checking reference WB. The defects in a regenerated signal RF, a tracking error signal TE and a focus error signal FE in one track are checked. When an error whose magnitude of the defect exceeds WC in a defect detecting circuit 26, the error is stored in a defect-position information memory circuit 28. Then, the step is jumped into the next track. This procedure is repeated. When the checking of the final track is finished, the contents in the circuit 28 are read and analyzed. When the defects exceeding WC occur, the unchecked tracks before and after the defective tracks are rechecked. The quality of the defects is judged based on the final checking reference value WA. Thus, the checking of the serious defect can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for detecting defects such as damage or foreign matter in a disc-shaped optical recording medium.

BACKGROUND OF THE INVENTION Conventional disk-shaped optical recording media (hereinafter referred to as optical disks) may have defects such as scratches on the recording surface or the introduction of foreign matter during manufacturing.

Since such defects pose a major obstacle during information reproduction, it is necessary to detect their presence in advance.3Recently, optical discs as combination and external memories have been put into practical use, and due to their characteristics, these recording media will be used in the future. It is expected to provide an inexpensive recording medium that is essential to the advanced information society of the world. Therefore, there is a need for a mass-production inspection device that can accurately detect defects in optical disks in a short period of time.

A conventional defect inspection apparatus will be described below.

FIG. 3 is a configuration diagram of an example of a conventional defect inspection device. 1
1 is an optical detection element, in which a light beam is incident on the optical disk from an optical nozzle 8, and a reading light beam reflected from the recording surface is guided. 2 calculates the output according to the spot of the reading light beam guided from each photodetector element 1;
The reproduction signal (RF) and the spiral or concentric circle formed on the optical disk from the optical head 8
- A 1-rank error signal (TE) corresponding to the positional deviation in alignment with the hook and a focus error signal (FE) corresponding to the convergence state of the light beam from the optical nod 8 on the recording surface.
) is a signal processing unit that calculates each of the following. 3 to 5 are these reproduction signals (RF), respectively.

l-Rank error signal (TE) and focus error signal (FE) are amplified and reproduced signal (RF/).

This is a signal amplification section that obtains a tracking error (IT l'(TE') + focus error signal (FE'). 6 is a signal amplified reproduction signal (RF/), I-
Ranogink error signal -Q-(TE') l When an error of a size greater than a certain threshold value occurs due to a defect in the disk in the focus error signal (FE/), detects the pulse width according to the size of the defect. This is a defect detection section that detects defects by outputting pulses. Reference numeral 7 denotes a control unit that performs a quality judgment by comparing the magnitude of the Varne pulse width detected by the defect detection unit 6 with an inspection standard, and performs system control of the inspection device f.

The operation of the defect inspection apparatus configured as described above will be explained below.

First, when tracking servo control and focus servo control are performed, an inspection is performed using a light beam of reproducing power along a spiral or concentric solid track formed on an optical disc. Alternatively, if there is a defect such as dirt or scratches on the recording surface on which the concentric L-rank is formed, the defect is read by the optical head and the plurality of photodetecting elements 1 forming the optical detection section are detected. Defects cause changes in the detection signal. Then, based on the change caused by the disc defect due to the detection signals of the plurality of photodetecting elements 1, the plurality of photodetecting elements 1
The detection signal is calculated. The defect causes a signal defect in the reproduced signal (RF) obtained from the signal processing section 2, as well as the trunking error signal (TE) and focus error signal (FE) also obtained from the signal processing section.
Defects also occur inside.

FIG. 5 shows the measurement principle for detecting defects contained in reproduced signals. Depending on the type of defect, the reproduced signal changes either in the direction of increasing 6/, -7 or in the direction of decreasing. A threshold value is set for this signal to perform defect detection, and a path (V) having a width corresponding to the size of the defect that caused the threshold value is output. Then, measure the size of this pulse width using a clock pulse,
Detect the size of defects.

Serious defects in the reproduced signal (RF) cause mismatch between recorded information and read information, that is, bit errors and dropouts. Furthermore, if a relatively large defect occurs in the trunk error signal (TE) and focus error signal (FE), the tracking servo control or the focus servo control is likely to malfunction.

For this reason, the defect detection device accurately detects serious defects in the disk that may cause bit errors or dropouts, as well as serious defects that may cause the tracking servo control and focus servo control to malfunction. There is a need.

Incidentally, FIG. 4 shows an inspection flowchart of a conventional defect inspection apparatus. Optical discs have a huge recording capacity, and the number of information tracks on them is also huge. To avoid this, conventional defect inspection equipment skips the user information track range at fixed track intervals and performs defect inspection in order to shorten inspection time. Inspection standard value WB against inspection standard value WA
WA > WB), and a pass/fail judgment was made for defects.

Problems to be Solved by the Invention However, in the defect inspection apparatus using the conventional configuration and inspection method as described above, defects are inspected by flying over the entire surface of the optical disk at regular track intervals, so that defects may be caught between the inspection tracks. The problem is that it is difficult to detect serious defects, such as defects such as scratches, stains and scratches on the surface of an optical disk substrate that spans dozens of tracks, or on the recording surface where spiral or concentric tracks are formed. was.

In order to solve the above-mentioned conventional problems, the present invention realizes the ability to reliably detect serious defects in disk-shaped recording media in a short inspection time, and improves the reliability of identifying defects. The object of the present invention is to provide a defect inspection device with improved performance.

Means for Solving the Problems In the present invention, when detecting defects in the data area of spiral twists or concentric tracks in a disc-shaped optical recording medium, the disc-shaped optical recording medium is inspected for each track at regular intervals. , a defect detection pulse obtained when a defective part that is assumed to exist inside or on the surface of a disk-shaped optical recording medium is read according to the state in which it is placed at a reading position, and information on the occurrence position of the defective part. By accumulating the detected position information and re-inspecting the tracks before and after the detected defective part, serious defects in disc-shaped optical recording media can be detected in a short inspection time and more efficiently. This enables reliable detection.

Effect: With this configuration, when defect inspection is performed by jumping up the information track range every certain track, the threshold value Wc for the size of a large defect of 9,-1 can be set to a smaller value than the threshold value WB in the conventional method. WB > WC), etc., to detect the position information at the time of defect occurrence and record this defect information. By re-inspecting the trucks, it is possible to improve reliability against major defects.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of a defect inspection apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 21 denotes a photodetector element through which a light beam from the optical head 30 is incident on the disk and is reflected by the recording surface of the disk, and 22 indicates a readout beam guided from each photodetector element 21. The output corresponding to the spot of the light beam is calculated, and a tracking error signal 10 ＼-7 (TE )ff This is a signal processing unit that calculates a focus error signal (FE) according to the convergence state of the light beam from the optical head on the recording surface portion of the disk. 23-2
5 amplifies the reproduced signal (RF), l-racking error signal (TE), and focus error signal (jE) to generate a reproduced signal (RF/).

This is a signal amplification section that obtains a tracking error signal (TE/) and a focus error signal (FE'). 26 is an amplified reproduction signal (RF'), racking error signal (TE'), and focus error signal (TE') that contain abnormal signals (errors) exceeding a certain threshold due to defects on the outer surface of the disc or inside the disc. ) occurs, a defect detection unit 27 outputs a detection pulse with a pulse width corresponding to the size of the defect, and the defect detection unit 27 outputs a reproduction signal (RF') and a racking error signal (T E'). )
J. A defect position information detection unit that detects position information of the error occurrence using a pulse obtained when an error occurs in the focus error signal (FE/) as a trigger;
28 indicates the defect position obtained by the information detection unit 27; - raw signal (RF); - racking error signal (TE);
and a defect information recording unit that stores error occurrence position information in the focus error signal (FE), and is composed of a memory.

29 indicates that when a defect pulse is generated in the defect detection section 26,
After reading the position information from the defect position information detection unit 27 and recording the position information in the defect information recording unit 28, the size of the pulse width is compared with the inspection reference value to determine pass/fail. The system control section of the inspection device performs re-inspection start address calculations, etc.

The operation of the defect inspection apparatus of this embodiment configured as described above will be described below with reference to the inspection flowchart of the defect inspection apparatus shown in FIG.

After the inspection, the inspection drive is started up in process 100, and the tracking servo control and focus servo control are kept stable. Next, in process 101, the optical head is caused to seek to the first address of the user area of the disk, and in the next revolution after the completion of the seek, defect inspection for one track is performed. At this time, in process 103, defect inspection in the reproduced signal, tracking error signal, and focus error signal is performed, and a reference value is set so that the size of the defect becomes Wc with respect to the inspection reference value WA. However, the WKO value is the standard value WA using the conventional measurement method.
, WA ,>WB ”:)Wc.

In decision 104, the size of the defect is W. If an error exceeding 100% has occurred, the process proceeds to process 105, where the defect occurrence position data and its size are recorded on the position information recording memory.

Next, the process advances to process 107 and jumps to the next inspection l/ranok. If no defect occurs in decision 104, the process similarly jumps to the next inspection track.

The above steps I- are repeated 7 times until the end of the user information area, and after the last track of the user area has been inspected in decision 106, the contents of the defect information recording memory are read in process 108. It's crowded. Process 10
At step 9, the defect information read at step 108 is analyzed. If a defect with a size of We13 or above has occurred, the re-inspection start address and Calculate the re-examination end address. If a plurality of defects of We or higher have occurred, re-inspection start addresses and A-inspection end addresses for the plurality of defects are calculated.

Next, in process 112, the optical head is caused to seek to the re-inspection start address calculated in process 111, and all tracks from the start address to the end address are inspected for defects.
Similarly, defect information is stored in the memory for defect position information.

Then, in decision 115, the same operation is repeated as many times as there is defect information. At this time, the re-inspection may be performed by skipping several defective tracks before and after the defective track.

Finally, in process 116, the quality of the defect is determined based on the defect size inspection reference value WA, and the measurement is completed.

14.

According to the present invention, when detecting a defect in a spiral track or a concentric track in a disc-shaped optical recording medium, first, each track of the disc-shaped optical recording medium is detected at regular intervals. Defect inspection of disc-shaped optical media that generates a defect detection signal according to the state in which a defective part, which is assumed to exist inside or on the surface of the disc-shaped optical recording medium, is placed at the reading position by performing the inspection. In addition, by using the defect detection pulse obtained by reading the disk-shaped optical recording medium to accumulate information on the location of the defect and re-inspecting the tracks before and after the defect, the disk-shaped optical recording medium can be re-inspected. This allows serious defects in optical recording media to be inspected more reliably.

[Brief explanation of the drawing]

FIG. 1 shows an example of a disk-shaped optical recording medium according to an embodiment of the present invention. Configuration of medium defect inspection device 15 ・＼-. FIG. 5 is a flowchart of the inspection process. 21... Photodetection element, 22... Signal processing section, 23
~25... Signal amplification section, 26... Defect information detection section, 27... Defect information inspection circuit, 28...
. . . Defect information recording section, 29 . . . Control section. Name of agent: Patent attorney Toshio Nakao and one other person Field (

Claims (4)

[Claims] (1) A light beam is converged and irradiated while scanning a spiral or concentric information track on a disk-shaped optical recording medium in a fixed number of tracks, and a reflected beam from the disk-shaped optical recording medium is detected. a detection means including a photodetector; and a pulse generation means for generating a pulse signal when the intensity of the reflected beam is modulated by a defect on the disc-shaped optical recording medium and the output signal of the detection means exceeds a certain level. , a position detecting means for detecting the defect position of the disc-shaped optical recording medium of the light beam, and a means for storing the defect occurrence position information, and the defect occurrence position information is used to detect the front and rear tracks including the defect occurrence track or the front and rear tracks including the defect occurrence track. A defect inspection device for a disk-shaped optical recording medium, characterized in that a plurality of tracks are re-inspected. (2) At the time of re-inspection, all the uninspected tracks that are narrowed by the two passing tracks before and after the track where the defect inspection occurred in the track skipping inspection are sandwiched between them are inspected. A defect inspection device for disc-shaped optical recording media. (3) An inspection reference value (W_C) for the size of a defect during track skipping inspection and an inspection reference value (W_A) for the size of a defect during re-inspection are set to different values. 2. The defect inspection device for a disc-shaped optical recording medium according to 2. (4) The inspection standard value (W_C) for defect size during track skipping inspection and the inspection standard value (W_A) for defect size during re-inspection are set to values such that W_A>W_C. 4. The defect inspection device for a disc-shaped optical recording medium according to claim 3.