JPH02163641A - Disk inspection device - Google Patents

Abstract

PURPOSE:To exactly detect not only a defect such as a flaw, etc., but also the crack of a disk inner diameter part by photodetecting a reflected beam from a output level of this detecting means with a prescribed reference level. CONSTITUTION:A beam scanning device 2 is composed of a laser light source 3 and a rotary polygon mirror 4, by which the disk surfaces of disks 1a and 1b are irradiated with a laser beam emitted from the light source 3. By the rotation of this polygon mirror 4, the laser beam executes scanning in a distance L from the outer circumferential part of one disk 1a to the inner circumferential part of the other disk 1b. The first optical detecting means 5 is provided on the moving route of an optical axis for a normally reflected light from the disk surface in order to photo-detect the normally reflected light and the second optical detecting means 6 is provided on the moving route of the optical axis for a scattering reflected light in order to photo-detect the scattering reflected light. The output level of this optical detecting means is compared with the prescribed reference level and the crack of the disk inner diameter part is detected by a comparing output with the scan-timing of the disk inner diameter part.

Description

TECHNICAL FIELD The present invention relates to a disk inspection apparatus, and more particularly to an apparatus for inspecting defects such as scratches on an optical disk on which information such as video and audio is recorded as minute bits.

BACKGROUND ART There is an optical method as a method for recording information such as video and audio on a disk. This optical method creates a resist master by coating the surface of a glass master, which serves as a substrate, to form a resist film, and records a laser beam focused on a minute point on the resist film of the resist master. Information is recorded using the so-called bit-by-bit method in which the information is flickered according to the information, and the information is recorded by the length of the bit (indentation) obtained by irradiation and subsequent development.

In optical discs obtained in this way, if there are defects such as scratches in addition to minute bits on the surface of the disc, this will cause noise or so-called dropouts during playback, so it is important to avoid this during the manufacturing stage. It is necessary to inspect for defects such as scratches.

By the way, in the case of optical video discs, side A and side B are pasted together to form a single double-sided disc, but during the production process from molding to pasting, the disc may be damaged due to physical impact, etc. Cracks may occur on the inner diameter.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a disk inspection device that can accurately detect not only defects such as scratches on the disk surface but also cracks in the inner diameter portion of the disk.

In the disk inspection device according to the present invention, a laser beam is irradiated on the disk surface of the disk being driven to rotate, and the laser beam is scanned in the disk radial direction, and the laser beam is placed on the moving path of the optical axis of the specularly reflected beam from the disk. The optical detection means receives a reflected beam from the disk surface, the output level of the optical detection means is compared with a predetermined reference level, and a crack in the inner diameter of the disk is detected based on the comparative output at the scanning timing of the inner diameter of the disk. It has become.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1 showing an embodiment of the present invention, for example, two disks 1. a.1. b are each supported by a turntable (not shown) and rotated by a spindle motor (not shown) at a rotation speed of, for example, 30 [rpn+].

A laser beam is irradiated from a beam scanning device 2 onto the surfaces of these disks la and lb. The beam scanning device 2 consists of a laser light source 3 and a rotating polygon mirror 4 that irradiates the laser beam emitted from the light source 3 onto the disk surface of the disk 1aib.The rotation of the polygon mirror 4 directs the laser beam to one of the disks. The distance from the outer circumference of disk 1a to the inner circumference of the other disk 1b is scanned. The scanning speed over this distance is determined by the rotational speed of the rotating polygon mirror 4, and is set to, for example, 3000 scans/second. Also, for one disk, for example, the rotation angle is 5
72 scans are performed every degree.

As is particularly clear from FIG. 2, the laser beam is irradiated at a position offset by a distance d from the centers of rotation of the disks la, lb at an incident angle α with respect to a line perpendicular to the disk surface. The intensity distribution of the reflected light from the disk surface based on this irradiation light has a wide distribution as shown in FIG. 3 because diffraction occurs due to the bits on the surfaces of the disks la and lb.

In Fig. 3, A is the specularly reflected light, B is the scattered reflected light by the bit, and C is the scattered reflected light by the defect.The emission angle of the specularly reflected light A with respect to a line perpendicular to the disk surface is β1 (-α
), the emission angle of the scattered reflected light C due to the defect is β2 (ku β1
).

In FIGS. 1 and 2, on the moving path of the optical axis to the specularly reflected light from the disk surface is a first light detection means (hereinafter referred to as a specularly reflected light sensor) for receiving specularly reflected light A. )5
However, on the moving path of the optical axis of the scattered reflected light C, there is a second light detection means (hereinafter referred to as
A scattered reflection light sensor) 6 is provided. These sensors 5 and 6 are integrally constructed, which facilitates position adjustment.

Note that the laser beam is irradiated at a position offset by a distance d with respect to the center of rotation of the disk, but this is because the part where the intensity of the scattered reflected light B by the bit is large escapes to the outside of the scattered reflected light sensor 6. be. Also, CAV
(Constant angular velocity) On a disk, the size of the bit differs between the inner and outer circumferences of the disk, and when a laser beam is scanned from the inner circumference to the outer circumference of the disk, the scattered reflected light B from the bit and the scattered reflected light C due to defects Since the levels become very close and it becomes difficult to distinguish, a light shielding plate 7 is provided in the scanning portion from the inner circumference to the outer circumference of the disk 1a to prevent defect detection.

FIG. 4 is a block diagram showing an example of the configuration of the circuit system. In the figure, the output of the specular reflection light sensor 5 is amplified by an amplifier 8 and then passed through BPFs (band pass filters) 9 to 11.
The noise component due to the disturbance is removed and the comparators 12 to 14
are each comparison input.

On the other hand, the output of the scattered reflection light sensor 6 is amplified by an amplifier 15 and then becomes a comparison input of a comparator 17 after noise components due to disturbance are removed.

Assuming that there are various defects on the surface of the disk, such as pinholes, scratches caused by gas running during molding, and whitening or blackening of the aluminum reflective film,
As shown in Figure 5, the scattered reflected light (noise components caused by white foreign objects and scratches caused by running gas on the surface due to the whitening of the aluminum reflective film, and the blackening of the aluminum reflective film on the specular light surface) It contains noise components caused by powdered aluminum and pinholes, and is detected by each sensor as noise at the level shown in the figure.

In order to discriminate these various types of noise, the comparator 12 has reference levels GS, GM, and GL to detect defects such as powdered aluminum, and the comparator 13 has reference levels FS, FM, and FL to detect pinholes. The comparator 17 detects defects such as the reference level DS.
, DM, and DL to detect defects such as white foreign matter and scratches caused by gas running. In addition, the comparator 14 is a BPF
When the output level of No. 11 is greater than a predetermined reference level, a comparison output is generated. This comparison output is supplied to gate circuit 8. This gate circuit 18 is connected to a processing device 2 which will be described later.
] is applied with a detection pulse generated at the timing when the inner diameter portion of the disk is scanned by the laser scanning device 2, it becomes open and relays the comparison output. Comparator 1-2
．． 13. Each comparison output of 17 and the output of gate circuit 8 are transmitted to a processing device 21 via buffers 19 and 20.

The processing device 21 is constituted by, for example, a microcomputer, and counts the number of detections for each different defect based on the comparison outputs of the comparators 2, 13 and 17, and counts at least one of the number of detections for each defect. A disk for which the number of times exceeds a predetermined number is determined to be defective, and the presence of a crack in the inner diameter of the disk is detected based on the output of the comparator 14 via the gate circuit 18. The determination result is printed out by the printer 19, for example.

Next, the defect inspection processing procedure executed by the processor of the processing device 21 will be explained according to the flowchart of FIG. Incidentally, one disk is scanned 72 times, for example, every 5 degrees of rotation angle.
It is assumed that this subroutine is called and executed at each scanning timing.

In FIGS. 6(A,) and (B), the processor first takes in the comparison output of the comparator 7 (step S1).
, the noise level in this comparison output data is at the reference level D.
In step 82, it is determined whether or not output data (hereinafter referred to as DS output data, DM output data, and DL output data) exists when the level is higher than each level of S, DM, and DL.
~S4), if it exists, a counter that counts the number of occurrences of each output data is incremented (steps 85~S7).

Next, the comparison output data of the comparator ] 2 is taken in (step S8), and the output data when the noise level in this comparison output data is equal to or higher than each of the reference levels GS, GM, and GL (hereinafter referred to as GSS output pig GM) Steps 89 to 511) determine whether or not output data (referred to as GL output data) exists. If so, a counter corresponding to each output data is incremented to count the number of occurrences of each output data. (Steps 812-514).

Furthermore, the comparison output data of the comparator 13 is taken in (step 515), and the output data (hereinafter referred to as FS output data) when the noise level in this comparison output data is equal to or higher than the reference levels FS, FM, and FL. FM output data,
(referred to as FL output data) exists (steps 316 to 518); if so, the corresponding counter is incremented to count the number of occurrences of each output data (steps 316 to 518); 521).

Next, the scanning number counter is incremented by L-L (step 522), and it is determined whether the count value N has reached 72, that is, whether 72 scans for one disk have been completed or not.Step 323 ), if the process has not been completed, the process returns to step S1 and the above-described process is repeated. 7
When two scans are completed, the number of times each defect detection (count value of each counter) is less than or equal to the allowable number of defects (pass judgment number) for each of the defects detected based on the nine types of reference levels. It is determined whether there is one (step 524).

The number of pass judgments for each defect is set as follows. For example, DS output data twice, 0M output data once,
DL output data is 0 times, FS output data is 2 times, FM output data is 1 time, FL output data is 0 time, GS output data is 3 times, 6M output data is 2 times, GL output data is 0.
times.

If the number of times all defects are detected is less than or equal to the number of acceptance judgments described above, the disk is judged to be an acceptable product (step 525).
. If even one of all the defect detection times exceeds the number of pass judgments, it is determined whether the number of defect detections exceeds the number of fail judgments (step 526). The number of failure judgments is set as follows. For example, DS output data is sent 4 times, 0M output data is given 3 times, DL output data is given 2 times, FS
It is assumed that the output data is output 5 times, the FM output data is output 3 times, the FL output data is executed 2 times, the GS output data is executed 6 times, the 6M output data is executed 4 times, and the GL output data is executed once.

If even one of the number of defect detections exceeds the number of rejections, the disk is determined to be a rejected product (step 527), and if there is no defect detection number exceeding the number of rejections, that is, the disc is determined to be an acceptable product. Those that do not belong to rejected products are determined to be intermediate products (step 528).

Through the series of processes described above, it is possible to accurately detect all types of defects on the disc, and to determine the appearance quality rank of the disc based on the criteria.

Next, the operation for detecting cracks in the inner diameter portion of the disk will be explained with reference to FIG. In addition, in Fig. 7, (A)
(B) is a diagram showing the inspection area when two sheets are inspected simultaneously, and (B) is a waveform diagram of each part.

In FIG. 7, since there are specular reflection detection objects such as bar codes on the inner circumference of the disk, an area to avoid them is defined as the inspection area, and the processing device 21 detects the inner circumference of the disk using the laser scanning device 2. Figure 7 (
A detection pulse (ω is generated) as shown in B) is supplied to the detection pulse (ω is a gate circuit) 8.

On the other hand, the output level (b) of BPFII by the specular reflection light sensor 5 changes as shown in the figure during one scanning period over the two disks la and lb, and the comparator 14 detects that this output level (peak) is higher than the reference level. When the comparison output pulse (C
) is generated and supplied to the gate circuit 18. Gate circuit 1
8 becomes an open state in response to the detection pulse (a) supplied from the processing device 21, so this detection pulse (a)
Comparison output pulse (d+
Only bags processed through buffer 20! 21. The processing device 21 detects the existence of a crack in the inner diameter portion of the disk by being supplied with this pulse (d+).

In the above embodiment, two means for supporting and rotationally driving the disks are arranged in the laser scanning direction to inspect two disks at a time, but the present invention is not limited to this. Instead, it may be a single disk, or three or more disks may be arranged. The larger the number, the more disks can be inspected at once, and therefore the inspection efficiency can be improved.

Further, in the above embodiment, the comparators 1.2. 1.3.
] 7 has been explained as being fixed, but it is also possible to make these standard levels variable, and by making it possible to input the allowable number and limit number of defects from the outside, it is possible to set the appearance quality judgment criteria. It can be changed arbitrarily, and the appearance quality rank of the disc can be determined based on the criterion.

As described in detail, the disk inspection apparatus according to the present invention scans in the radial direction of the disk while irradiating a laser beam onto the disk surface of the disk that is being driven to rotate.
The reflected beam from the disk surface is received by a light detecting means disposed on the path of the optical axis of the specularly reflected beam from the disk, and the output level of this light detecting means is compared with a predetermined reference level. Since the structure is such that cracks in the inner diameter portion of the disk are detected based on the comparison output at the scanning timing of , it is possible to accurately detect not only defects such as scratches on the disk surface but also cracks in the inner diameter portion of the disk.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an outline of the structure of a mechanical section of a disk inspection device according to the present invention, FIG. 2 is a side view showing the relationship between the laser irradiation section and the light receiving section in FIG. 1, and FIG. 3 is a disk surface. FIG. 4 is a block diagram showing the configuration of the circuit system of the disk inspection device according to the present invention, and FIG. Waveform diagram showing noise components included in each output, No. 6
Figures (A) and (B) are flowcharts showing processing procedures for defect inspection, and Figure 7 is a diagram for explaining the operation of detecting cracks in the inner diameter portion of the disk. Explanation of symbols of main parts la, ], b...Disk 2...Laser scanning device 4...Rotating polygon mirror 5...Specular reflection light sensor 6... ...Scattered reflection light sensor 12-14.17...Comparator 21...Processing device

Claims (2)

[Claims] (1) A disk rotating means for supporting and rotationally driving the disk, a laser scanning means for scanning in the radial direction of the disk while irradiating a laser beam onto the surface of the disk, and a specularly reflected beam from the disk. A light detection means disposed on the movement path of the shaft, a comparison means for comparing the output level of the light detection means with a predetermined reference level, and a detection pulse is generated at the timing when the inner diameter portion of the disk is scanned by the laser scanning means. A disk inspection device comprising means for detecting a crack in an inner diameter portion of the disk based on a comparison output of the comparison device when the detection pulse is generated. (2) The disk inspection apparatus according to claim 1, wherein a plurality of said disk rotating means are arranged in the scanning direction of the laser beam.