JPH02163639A - Disk inspection device - Google Patents

Abstract

PURPOSE:To exactly detect all defects whose forms on the disk surface are different from each other by constituting the above device of a rotary means, a beam scanner, the first and the second photodetecting means, a comparing means and a deciding means. CONSTITUTION:Disks 1a, 1b are held by a turntable, a respectively and driven to rotate by a rotary means. A beam scanner 2 consists of a laser light source 4 and a rotary polygon mirror 4, and as the polygon mirror 4 rotates, a laser beam is scanned in a distance L extending from the outside peripheral part of the disk 1a to the inside peripheral part of the disk 1b. A first photodetecting means 5 and a second photodetecting means 6 are placed on a moving path of an optical axis of a regular reflection beam from the disks 1a, 1b, and in a position deviated against the moving path of the optical axis of the regular reflection beam, respectively. A comparing means compares each output level of the photodetecting means 5, 6 with a prescribed reference level, and a deciding means decides whether a defect of the disk exists or not, based on the comparison output of the comparing means.

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 pits.

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. It is exposed to light in a so-called bit-by-bit method in which it flickers in accordance with the information, and is then developed to record information based on the length of the dents and their repetition period.

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.

2. Description of the Related Art Conventionally, as an apparatus for inspecting the presence or absence of defects in a disk, for example, the apparatus described in Japanese Patent Application Laid-Open No. 60-22650 is known. In this conventional device, a laser beam is irradiated onto the disk surface in the form of a minute spot, and a photodetector placed at a position offset from the optical axis of the reflected light from the disk surface detects the scattered reflected light from the disk surface. The structure is such that the presence or absence of defects is inspected by receiving light and comparing the output level of this photodetector with a set level.

By the way, optical discs have various defects such as not only defects such as scratches, but also pinholes, scratches near the inner circumference of the disc caused by gas running during molding, whitening or blackening of the aluminum reflective film, etc. Defects may exist.

These various defects have different shapes on the disk surface, so the conventional device described above is configured to detect defects based only on scattered reflected light, so it is possible to accurately detect all defects with different shapes. It was difficult to detect.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a disk inspection device that can accurately detect all defects that have different shapes on the disk surface.

In the disk inspection device according to the present invention, a laser beam is irradiated onto the disk surface of a rotationally driven disk and scanned in the disk radial direction, and a laser beam is scanned in the disk radial direction. The reflected beam from the disk surface is received by the first light detecting means and the second light detecting means disposed at a position offset with respect to the moving path of the optical axis, and the output level of each of these light detecting means is adjusted to a predetermined level. The disc is compared with a reference level, and based on the comparison output, it is determined whether or not there is a defect in the disc.

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 la and lb are each mounted on a turntable (not shown).
and is rotated by a spindle motor (not shown) at a rotational speed of, for example, 30 [rpI11].

These discs 1. A laser beam is irradiated from the beam scanning device 2 onto the disk surfaces of a and lb. Beam scanning device 2
consists of laser beams 1g, 3 and a rotating polygon mirror 4 that irradiates the laser beam emitted from the light source 3 onto the surfaces of the disks la, lb. As the polygon mirror 4 rotates, the laser beam is directed 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 at this distance is determined by the rotational speed of the rotating polygon mirror 4, and is, for example, 3000 scans/
Set to seconds. Further, one disk is scanned 72 times, for example, every 5 degrees of rotation angle.

The laser beam is directed towards the disks la, 1. as is particularly clear from FIG. The beam is irradiated at a position offset by a distance d from the center of rotation b 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 is as follows: disk 1. a.1. Since diffraction occurs due to the bits on the surface of b, a wide distribution is obtained as shown in FIG.

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 (kuβI
).

1 and 2, on the moving path of the optical axis of the specularly reflected light A from the disk surface is a first light detection means (hereinafter referred to as a specularly reflected light sensor) for receiving the 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 allows easy 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 [a] 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 a specular reflection light sensor 5 is amplified by an amplifier 8, and then BPF (band pass filter) 9, 1 .
0, the noise component due to disturbance is removed and the comparator 11. ．．
1.2 each comparison input.

On the other hand, the output of the scattered reflection light sensor 6 is amplified by an amplifier 13, and then a noise component due to disturbance is removed by B P F 1.4, and becomes a comparison input of a comparator]5.

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 (ω is a noise component caused by white foreign matter due to the whitening of the aluminum reflective film and scratches caused by running gas, and the specular reflection) is the black color of the aluminum reflective film. It contains noise components caused by powdered aluminum and pinholes, which are detected by each sensor as noise at the level shown in the figure.

In order to discriminate these various types of noise, the comparator 11 has reference levels GS, GM, and GL to identify defects such as powdered aluminum, and the comparator 12 has reference levels FS, FM, and FL to identify defects such as pinholes. The comparator 15 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. Comparator 11. 1.2.
Each comparison output of i5 is transmitted to the processing unit 18 via a buffer 16.17.

The processing device 18 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 11, 12, ]5, 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. The determination result is printed out by a printer] 9, for example.

Next, the defect inspection processing procedure executed by the processor of the processing device 18 will be explained according to the flowchart of FIG. Note that one disk is scanned 72 times, for example, every 5'' of rotation angle, and this subroutine is called and executed at each scan timing.

In FIGS. 6A and 6B, the processor first takes in the comparison output of the comparator 15 (step S1),
The noise level in this comparison output data is at the reference level DS.
, DM, and DL (hereinafter referred to as DS output data, DM output data, and DL output data) exists.
S4) If the output data exists, a counter for counting the number of occurrences of each output data is incremented (Steps 85 to S7).

Next, the comparison output data of the comparator 11 is fetched (step S8), and output data (hereinafter referred to as GS output data, GM Output data, GL
Steps 89 to 511) determine whether there is any output data (referred to as output data), and if so, the counter corresponding to each output data is incremented to count the number of occurrences of each output data (step 31. 2~S14
).

Furthermore, the comparison output data of the comparator 12 is taken in (step S], 5), 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 each of the reference levels FS, FM, and FL. , FM output data,
(referred to as FL output data) exists (steps 31.6 to 81.8), and if so, the corresponding counter is incremented to count the number of occurrences of each output data (step 31 .9-521).

Next, the scanning number counter is incremented (step 522), and whether or not the count value N has reached 72 is determined.
That is, it is determined whether or not the 72 scans for one disc have been completed (step 823); if not, the process returns to step S1 and the above-described process is repeated. 72
When the number of scans has been completed, each defect detection number (
It is determined whether or not the count value of each counter is less than or equal to the allowable number of defects (pass determination number) (step 524). The number of pass judgments for each defect is set as follows. For example, DS output data is twice, 0M output data is once, D
L output data is 0 times, FS output data is 2 times, FM output data is 1 time, FL output data is 0 times, GS output data is 3 times, 0M 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 826). 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 five times, the FM output data is output three times, the FL output data is executed twice, the GS output data is executed six times, the 0M output data is executed four 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.

Incidentally, as shown in FIG. 7, a disc is generally provided with a stamp such as a loft number at a predetermined radial position along the inner circumferential direction. In this way, if there is a stamp such as a lot number on the disk surface, there is a possibility that this stamp will be mistaken for a defect. Generally, a defect on a disk does not exist for a long time in the circumferential direction of the disk, whereas a stamp such as a lot number exists for a relatively long time in the circumferential direction.

FIG. 9 is a flowchart showing the processing procedure for stamping the lot number, etc. It should be noted that since the radial position of the disk where the lot number or the like is engraved is predetermined, this subroutine is called and executed at each scanning timing corresponding to this radial position of the disk.

Further, it is assumed that the reference level DM of the comparator 15 is used as the determination reference level at this time.

In FIG. 9, the processor takes in the 0M output data of the comparator 5 (step 531), holds this 0M output data (step 532), and at the same time checks whether there is DM output data, that is, there is a defect higher than the DM level. It is determined whether or not there exists (step 833). If there is DM output data, a counter for counting the number of defects detected is incremented (step 534), and it is determined whether this count value N is greater than or equal to a predetermined value No (for example, 4), that is, whether there is a defect greater than or equal to the DM level. It is determined whether or not there have been more than 1 consecutive results (step 535).

If N<N, return to the main routine, and if N≧No, as shown in Figure 8, N0 or more defects of DM level or higher have been detected in a row, so this is a lot failure. 2. Clear the data held until then and do not judge it as a defect (Step 5)
36). It is determined that there is no DM output data in step 53B.
, the previously held data is changed to output data (step 537), the previous counter is cleared (step 538), and the process returns to the main routine.

In this way, when it is detected that the output data level of the scattered reflection light sensor 6 is equal to or higher than the predetermined reference level DM on the same circumference of the disk for a predetermined period or more given by the defect detection number No. By not determining this as a defect, it is possible to accurately detect only the original defect without misidentifying a stamp such as a loft number as a defect.

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.

Furthermore, in the above embodiment, the comparators 1.1. , 1.2.
Although each of the 15 standard levels has been explained as being fixed, it is also possible to make these standard levels variable, and by manually setting the allowable number and limit number of defects from outside, it is possible to set the appearance quality judgment standard arbitrarily. The appearance quality rank of the disc can be determined based on the criteria.

As described in detail, the disk inspection method according to the present invention scans in the radial direction of the disk while irradiating a laser beam onto the surface of the disk that is being driven to rotate.
The specularly reflected beam from the disk is detected from the disk surface by a first light detection means arranged on the path of movement of the optical axis and a second light detection means arranged at a position offset from the movement path of the optical axis. The optical detector receives the reflected beam of the light, compares the output level of each of these light detection means with a predetermined reference level, and detects defects on the disc based on this comparison output. All different defects can be detected accurately.

[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 the processing procedure for defect inspection, Figure 7 is a diagram showing how the lot number is engraved on the disk surface, and Figure 8 explains the situation in which the lot number is inspected as a defect. FIG. 9 is a flowchart showing the procedure for stamping lot numbers and the like. Explanation of symbols of main parts 1, a, 1. b...Disk 2...Laser scanning device 4...Rotating polygon mirror 5...Specular reflection light sensor 6...Scattered reflection light sensor 11.12.15 ... Comparator 18 ... Processing device

Claims (3)

[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 first light detecting means disposed on the moving path of the optical axis of the specularly reflected beam; a second light detecting means disposed at a position offset from the moving path of the optical axis of the specularly reflected beam; A disc characterized in that it comprises a comparison means for comparing each output level of the second light detection means with a predetermined reference level, and a determination means for determining the presence or absence of a defect in the disc based on the comparative output of the comparison means. Inspection equipment. (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. (3) The comparison means includes a first comparator that compares the output level of the first light detection means with a plurality of mutually different reference levels, and a first comparator that compares the output level of the second light detection means with a plurality of mutually different reference levels. a second comparator for comparison with a reference level; the determining means includes means for counting the number of times each different defect is detected based on the comparison outputs of the first and second comparators; 2. The disk inspection apparatus according to claim 1, wherein a disk in which at least one of the number of defects detected is equal to or greater than a predetermined number is determined to be a defective product.