JPS61190720A - Detector for disk defect - Google Patents

Abstract

PURPOSE:To detect accurately both the number of defects and their scales by setting the shift interval of a check track in the radius direction of a disk at the value equal to or smaller than the spot diameter of a check beam and storing successively the defect information on the check track adjacent to two memories storing the defect information equivalent to one circle of the disk to compare these information with each other in the circumference direction of the disk. CONSTITUTION:A disk 3 is revolved and a laser light beam 1 is irradiated on the disk 3 from a light source. Then the light reflected by the disk 3 or the transmitted through the disk 3 is checked for detection of the defects of the disk 3. The shift interval of a check track 7 for irradiation of the beam 1 in the radius direction of the disk 3 is set equal to or smaller than the spot diameter of the beam 1. Then the information on the check tracks adjacent to memories M1 and M2 storing the information equivalent to a single track 7 are stored successively. Then the defect information stored in both memories M1 and M2 are compared with each other in the circumferential direction of the disk 3. Thus it is possible to obtain the defect information on the disk 3 in both circumferential and radius directions.

Description

[Detailed Description of the Invention] [Summary] When inspecting defects by scanning an optical disk, etc. in the track direction, ■ If two memories capable of storing information for tracks are prepared, it is possible to detect defects larger than the inspection track. In this case, it becomes possible to accurately count the number of defects and to know the size of the defect in the radial direction.

[Industrial application field]

The present invention relates to a disk defect inspection device, and more specifically, to a data processing method for correctly recognizing the size of a defect on an optical disk.

[Conventional technology]

Conventional disk defect inspection equipment irradiates the surface of the disk to be inspected for defects with a laser beam in the form of a spot of approximately 1 μm, and performs photoelectric conversion of the intensity of the reflected light from the disk surface to inspect for defects. . The situation will be explained using FIG. The laser beam (2) is irradiated as a spot of about 1 μm onto a disk 3 rotating at a predetermined rotation speed using a predetermined optical system 2, and the reflected light 4 is guided to a photodetector 6 by a half mirror 5 or the like (7 is inspection truck).

The reflected light signal 11 and defect signal 12 obtained at this time are as shown in FIGS. 4(al) and (b), respectively.

That is, if there is a defect, the reflected light signal 11 will locally decrease, and a signal at an appropriate threshold level 13 will cause the reflected light signal 11 to decrease locally.
Can create defective pulses. By counting the defective pulses created in this way, the number of defects can be determined. Furthermore, by detecting the pulse width of the defect, it was possible to recognize the size of the defect in the disk tangential direction.

[Problem that the invention seeks to solve]

However, in such a conventional method, when the defects 21 are widely distributed in the radial direction as shown in FIG. ), the same defect is recognized as multiple defects, and the size of the defect in the radial direction cannot be recognized.

[Means for solving problems]

In order to solve the above problems, the present invention provides two memories capable of storing defect information for one revolution of the disk.

The radial movement interval of the inspection tracks is made equal to or smaller than the spot diameter of the inspection beam, and defect information of adjacent inspection tracks is sequentially stored in these two memories,
The defect information is compared in the circumferential direction.

For example, if defect information exists at the same or corresponding position in the circumferential direction, it means that the defects are one continuous defect in the radial direction, so the defects are counted. Try not to. On the other hand, if a defect exists in the preceding inspection track but there is no defect at the same position (corresponding position) in the circumferential direction of the next inspection track, it is assumed that the defect has ended there. Therefore, we are counting defects for the first time here.

At the same time, the size of the defect in the radial direction is calculated from the number of inspection tracks on which defect information existed continuously.

In this way, the present invention makes it possible to accurately count the number and recognize the size of defects even in the radial direction; since conventionally the number and size of defects in the circumferential direction could be detected1, It becomes possible to know the size and number of defects with complete accuracy.

(Embodiment) Fig. 1 shows a flowchart of defect signal processing showing an embodiment of the present invention.First, a flag is set to O (3 in the figure).
1) Next, the first memory M1 and the second memory M2
(32 in the diagram).

Then, the first inspection track of the disk is inspected over one circumference in the circumferential direction using a device as shown in Fig. 3 (33 in the figure).
. When the inspected defect information is stored in the memory, when the flag is an odd number, it is stored in the first memory M1, and when the flag is an even number, it is stored in the second memory M2 (34 in the figure). In this case, since the flag is 0, the defect information is stored in the second memory M2.
to go into.

(35 in the figure). At 36 in the figure, it is determined whether the flag is O, and if the flag is O, the flag is set to 1 (37 in the figure), and the inspection track is moved to the track next to all the inspection tracks (38 in the figure). .

The movement of this inspection track is made equal to or smaller than the spot diameter of the inspection beam (usually about 1 μm for optical disks) to prevent omissions in inspection on the disk.

The new (second) inspection track is inspected once again in the circumferential direction (33 in the figure). This time, since the flag is an odd number, defect information is stored in the first memory M1 (39 in the figure).
), and the flag is not 0, so the first
The defect information stored in the second memory M1 and the second memory M2 is compared in the circumferential direction.

If a defect in the first inspection track and a defect in the second inspection track share the same position in the circumferential direction, these defects are considered to be continuous on the disk. , the track number memory is set to 1 in order to recognize the radial size of the defect without counting the defect (41 in the figure). Then, 1 is added to the flag, that is, the flag is set to 2 (42 in the figure), and the inspection track is moved to the next one (38 in the figure).

If a defect exists in the first inspection track, but there is no defect in the second inspection track at a common position in the circumferential direction, the defect in the first inspection track ends there. It is thought that
The size of the defect in the radial direction is displayed (43 in the figure).

Since this defect was present only in the first inspection track and not in the second inspection track, the radial size was considered to be the size of one inspection track, and the size or the number of inspection tracks ( 1) is displayed. After displaying the size of the defect in the radial direction, the track count for recognizing the size of the defect at that position is reset to O (44 in the figure).

Then, 1 is added to the flag (42 in the figure) and the inspection track is advanced to the next one (38 in the figure).

When a new inspection track, ie, the third inspection track, is inspected (33 in the figure), its defect information is entered into the second memory M2 (34, 35 in the figure). At 36 in the figure, since the flag is never set to 0 except at the beginning, all subsequent processes proceed to the process at 40, and the process at 37 is never performed.

At 40 in the figure, the defect information for the second and third inspection tracks is now compared and processed in the same manner as the comparison of defect information for the first and second inspection tracks.

Thereafter, the same process is continued, and if the defect information of the (η-1)th and ηth inspection track exists at the same position in the circumferential direction, the number of defects is not counted and the defect is However, even though there is a defect in the (η-1)th inspection track, the ηth inspection track is If there is no defect in the same circumferential position in an inspection track, the number of defects is counted as one, and the defect is counted from the number of inspection tracks in which the defect existed continuously in the radial direction. Recognize the radial size of

For example, if the defect 21 shown in FIG. 5 is
If the inspection was carried out using inspection tracks ① and ②, defective pulse information for each inspection track would be obtained as shown in FIG. When this is processed using the above flowchart, defects are not counted in case (2) because there is no defect information. ■
Since there is defect information, the size of the defect is set to one as the number of inspection tracks. Since (2) and (2) have the same defect information as (2) and (2), respectively, the defect size is set to 2 and 3 as the number of inspection tracks, without counting the defects. ■Now■
Since there is no defect that is common to the defect in (1) to (2), the number of defects is counted as 1 for the defects in (1) to (2), and the width of the three inspection tracks is displayed as the size of the defect.

In this way, by inspecting the entire surface or desired area of the disk, the number and size of defects in the circumferential and radial directions can be accurately determined. Of course, it is obvious that if the data stored in the two memories is processed appropriately, it is also possible to recognize other information, such as the position and shape of the defect. In this way, the radial processing applied to the circumferential direction requires that this defect inspection device has two memories, and that the radial movement interval of the inspection truck is made equal to the diameter of the inspection beam spot. Defect information of adjacent inspection tracks while smaller than 2
This was made possible by storing defect information in two memories and comparing the defect information.

〔Effect of the invention〕

According to the present invention, when inspecting a disk for defects, it becomes possible to accurately recognize the number and size of defects not only in the circumferential direction but also in the radial direction. If the size, number, location, etc. of defects on a disk can be accurately known, that information will be more meaningful in determining the cause of the defect.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of a disk defect inspection process according to an embodiment of the present invention, FIG. 2 is a diagram showing pulses of defect information used to inspect the defects in FIG. 5, and FIG. 3 explains an optical disk defect inspection method. FIG. 4 is a diagram illustrating an inspection signal and a defect signal, and FIG. 5 is a diagram illustrating a large defect. DESCRIPTION OF SYMBOLS 1... Laser light, 2... Lens, 3... Optical disk, 4... Reflected light, 5... Half mirror 16...
Photodetector, 7...Detection track, 11...Reflected optical signal, 12...Defect (t number, 13...Threshold level, 21...Defect.

Claims (1)

[Claims] 1. In a disk defect inspection device that rotates a disk, irradiates the disk with a light beam, and examines the reflected light or transmitted light obtained to inspect the disk for defects, comprising: The radial movement interval of the tracks is made equal to or smaller than the spot diameter of the light beam, and information on adjacent inspection tracks is sequentially stored in each of two memories that can store information for one inspection track. , by comparing defect information of adjacent inspection tracks sequentially stored in the two memories in the circumferential direction,
A disk defect inspection device is characterized in that it is capable of obtaining information regarding disk defects not only in the circumferential direction but also in the radial direction. 2. When comparing the information of adjacent inspection tracks sequentially stored in the two memories, if a defect in the new inspection track exists in a position that matches a defect in the old inspection track, the defect is not counted; Defects are counted only when there is a defect in the old inspection track but no defect exists in the corresponding position of the new inspection track, and the radius of the defect is determined by the number of inspection tracks that had a defect in that position until then. A disk defect inspection device according to claim 1, which recognizes a size in a direction.