JPH02163640A - Disk inspection device - Google Patents

Abstract

PURPOSE:To exactly detect only a defect such as flaw, etc., without erroneously recognizing an engraved mark such as a lot number, etc., as the defect by deciding there is no defect when a comparing output is continuously outputted for more than a prescribed period on the same circumference of a disk. CONSTITUTION:The disk surfaces of disks 1a and 1b are irradiated with a laser beam from a beam scanning device 2. The laser beam irradiates a position, which is off-set to the center of the rotation for the disks 1a and 1b only by a distance (d), by the incident angle of alpha to a line perpendicular to the disk surface. The first optical detecting means 5 is provided on the moving route of an optical axis for a regularly reflected light A from the disk surface in order to photo-detect the regularly reflected light A and the second optical detecting means 6 is provided on the moving route of the optical axis for a scattering reflected light C in order to photo-detect the scattering reflected light C caused by the defect. When the comparing output is continuously outputted for more than the prescribed period on the same circumference of the disk, it is decided that there is no defect. Accordingly, only the defect such as the flow without erroneously recognizing the engraved mark such as the lot number, etc., as the defect.

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 by irradiation and exposure using a so-called pit-by-bit method that flickers in accordance with the information, and then by developing the resulting pits (indentations) 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.

Incidentally, an optical disc is generally stamped with a lot number or the like along the circumferential direction at a predetermined radial position. In this manner, when a stamp such as a lot number is present on the disk surface, it is difficult for the above-mentioned conventional apparatus to distinguish it from a defect such as a scratch, and there is a possibility that the stamp such as the lot number may be mistaken for a defect.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a disk inspection device that can accurately detect only defects such as scratches without mistaking markings such as loft numbers as defects.

In the disk inspection device according to the present invention, a laser beam is irradiated onto the disk surface of a rotationally driven disk while scanning in the disk radial direction, and a position deviated from the optical axis movement path of the specularly reflected beam from the disk is detected. The reflected beam from the disk surface is received by a light detecting means disposed on the disc surface, and the output level of this light detecting means is compared with a predetermined reference level. The structure is such that when comparison outputs on the same circumference are continuously output for a predetermined period or more, it is determined that there is no defect.

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 and lb are each carried by a turntable (not shown) and a spindle motor (not shown).
The rotational speed is, for example, 30 [rpn].

These disks la, 1. A laser beam is irradiated from the beam scanning device 2 to the board surface 2 of b. The beam scanning device 2 consists of a laser beam [3 and a rotating polygon mirror 4 that irradiates the laser beam emitted from the light source 3 onto the surfaces of the disks ia, ] and b, and the laser beam is emitted by the rotation of the polygon m4. is scanned over the distance from the outer circumference of one disk 1a to the inner circumference of the other disk 1b. 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 disk 1. which is particularly clear from FIG. It is irradiated at a position offset by a distance d from the center of rotation of a and 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 pits on the surface of the disks la and lb.

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

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 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 due to the pit is large escapes to the outside of the scattered reflected light sensor 6. be. Also, CAV
In a (constant angular velocity) disk, the size of the pits differs between the inner and outer peripheries of the disk, and when a laser beam is scanned from the inner periphery to the outer periphery of the disk, the scattered reflected light B from the bits 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 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 1.1,
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 a BPF 14, and becomes a comparison input of a comparator 15.

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 includes noise components caused by white foreign objects and scratches caused by running gas due to the whitening of the aluminum reflective film, and the specular reflection light surface includes the blackening of the aluminum reflective film. 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 distinguish between 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 12 has reference levels FS, FM, and FL to identify defects such as powdered aluminum. 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 1.1. 1.2.
Each of the 15 comparison outputs is transmitted to the processing device 18 via a buffer 1.6.17.

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 1, 12. A disk for which the number of times exceeds a predetermined number is determined to be defective. 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 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 same number of occurrences of each output data (steps 89 to 511). 812-514
).

Furthermore, the comparison output data of the comparator 12 is taken in (step 515), and the output data (hereinafter referred to as FS output data, FM output data, F
Steps S], 6 to S1.8) determine whether or not the output data (referred to as L output data) exists; if it exists, the corresponding counter is incremented to count the number of occurrences of each output data ( Steps 819-521)
.

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 52B); 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
The LL force data is 0 times, the FS output data is 2 times, the FMS output data is 1 time, the FLL force data is 0 times, the GS output data is 3 times, the 0M output data is 2 times, and the GLL force 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 4 times, 0M output data is 3 times, DL output data is 2 times, FS
The output data is 5 times, the FMS output data is 3 times, the FLL force data is 2 times, the GS output data is 6 times, the 0M output data is 4 times, and the GLL force data is 1 time.

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 828).

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. - In boat fishing, defects on discs do not exist for a long time in the circumferential direction of the disc, whereas markings such as lot numbers etc. exist for a relatively long time in the circumferential direction.

FIG. 9 is a flowchart showing the processing procedure for stamping the loft number, etc. It should be noted that since the disk radial position where the loft number and other markings are engraved is determined in advance, this subroutine is called and executed at each scanning timing corresponding to this disk radial position.

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 15 (step 531), holds this 0M output data (step 532), and at the same time checks whether there is DM output data, that is, if there is a defect higher than the DM level. It is determined whether it exists (step 833). If there is DM output data, a counter for counting the number of defect detections 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 of the DM level or higher is N0. It is determined whether or not there have been more than 1 consecutive results (step 535).

If N<No, 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 the lot number. etc., and clears the data held until then and does not judge it as a defect (step 53
6). If it is determined in step 833 that there is no DM output data, the previously held data is set as output data (step 537), and the previous counter is cleared (step 53).
8) Return 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, only the original defect can be accurately detected without misidentifying the lot number or other stamp 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.

Further, in the above embodiment, the comparator 11. ．． Although each reference level in 12.15 has been explained as being fixed, it is also possible to make these reference levels variable, and by making it possible to input the allowable number and limit number of defects from the outside, the appearance quality judgment criteria can be changed. 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 detection means disposed at a position offset from the moving path of the optical axis of the specularly reflected beam from the disk, and each output level of this light detection means is set to a predetermined reference level. When this comparison output exists, it is determined that there is a defect, and when the comparison output on the same circumference of the disk is output continuously for a predetermined period of time, it is determined that there is no defect. Engravings such as numbers are not mistaken for defects (only defects such as scratches 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. 4 is a block diagram showing the configuration of the circuit system of the disk inspection device according to the present invention, and FIG. 5 is a scattering reflection light sensor (a) and a specular reflection light sensor (l). ) waveform diagram showing the noise components included in each output,
Figures 6 (A) and (B) are flowcharts showing the processing procedure of defect inspection, Figure 7 is a diagram showing the state of stamping of, for example, a lot number on the disk surface, and Figure 8 is a situation where 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, lb...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 Figure 1 Applicant: Pioneer Corporation Pioneer Video Corporation

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 arranged at a position offset with respect to the movement path of the shaft;
Comparing means for comparing the output level of the light detecting means with a predetermined reference level, and determining means for determining that there is a defect when the comparison output of the comparing means exists, A disk inspection device characterized in that it is determined that there is no defect when the comparison output of the comparison means is continuously output for a predetermined period or more. (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.