JPS58123444A - Inspecting device for pattern defect - Google Patents

Abstract

PURPOSE:To provided an optical defect detector which automatically detects a defect included in a pattern, by a method wherein an optical axis of a receiving system is inclined so that it approaches a direction of a stripe more than a direction extending perpendicularly to a pattern surface. CONSTITUTION:Output signals of light receivers A1 9-1, and A2 9-2 and A3 9-3 are inputted to an angle signal circuit 16, a positive or a negative angle signal is produced by the output signals, and a computer 17 issues a command to drivers 21 and 22 via a control circuit 20 according to a previously determined program to perform a scanning in an X-direction and a Y-direction of a laser projecting light. If a spot of the laser projecting light so scanned passes through a defect spot of a stripe pattern, a scattered light enters a photomultiplier tube 15, and the detecting signal of the photomultiplier 15 is inputted to a signal processing part 24 via a preamplifier 23. After the signal processing part 24 conducts a processing such as a schematic classification of a defect degree by means of a crest value of a defect signal, it is inputted to the microcomputer 17, which, in turn, detects a defect of a stripe forming a stripe pattern.

Description

[Detailed description of the invention]

The present invention relates to an optical pattern defect detection device that automatically detects defects included in a striped pattern provided on, for example, an image receiving surface of an image pickup tube. As shown in FIG. 1, the image-receiving surface of a color image pickup tube usually has a striped Nesa film pattern y2 etched on a face plate (generally a glass plate) 1. Figure 2 is an enlarged cross-sectional view of the same, and the above stripe pattern 2 has R, B, and G stripes f corresponding to the three colors.
2'. There may be a short circuit 3-8 between each of these stripes as shown in Figure 3, or there may be a break 3-8 in any of the stripes as shown in Figure 4.
If there is a stripe 2', the image signal will be damaged, so it is essential to inspect the stripe 2' when manufacturing an image pickup tube. Conventionally, the above-mentioned striped skin was examined exclusively using a microscope. This was done by visual inspection using a large amount of time and effort. Currently, in electronic technology, automatic inspection equipment using photoelectric means has been put into practical use for IC heads, but these are not yet capable of inspecting material surfaces that have not yet been fully formed. Therefore, it is generally difficult to inspect a face plate with a glossy finish. The reason for this is that when a beam of light for inspection is projected onto a face plate with a fully formed bump, the light is scattered by the pattern, so it is not possible to distinguish between the light scattered by defects and the light scattered by normal gloss, except in special cases. It is. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inspection device that can automatically detect defects in a stripe pattern formed on an image receiving surface of an image pickup tube. Next, the state of light scattering in a normal stripe pattern and the state of light scattering in a defective portion will be explained, and the principle of detecting a defect using the difference in the above-mentioned two scattering states will be briefly described. FIG. 5 shows a part of the stripe 2' enlarged and a laser beam 4 irradiated from above.
2' is a schematic perspective view showing the state of scattering at the edge 2'' of 2', 4' is a spot of laser light, and 5 is a scattered light. For convenience of explanation, as shown in the figure, stripes 2' are The parallel direction is defined as the Y direction, and the direction perpendicular to this and parallel to the image receiving surface is added as the X direction. Figure 6 shows a cross-sectional view taken along a plane perpendicular to the Y axis with the directional characteristic curve of scattered light added. Fig. 7. The appearance of peaks and valleys in the scattered light is due to the interference of the scattered light itself. Fig. 7 shows the directional characteristic curve of the scattered light in a cross section perpendicular to the X-axis. It can be seen that the energy of the scattered light is concentrated directly upward compared to the figure.In other words, the energy of the scattered light is concentrated on the plane perpendicular to the Y axis (plane E41 in Figure 7).From the above characteristics, As can be easily understood, when there is a short circuit defect a-1 as shown in FIG. 8, and when there is a disconnection defect 3-'! as shown in FIG. When projected onto a defective area, scattered light 6,6' is generated in a direction that does not occur from a normal stripe, that is, in a direction out of the plane perpendicular to the Y-axis.This phenomenon has been experimentally confirmed by nine researchers. Although the above description has been about scattering in the reflection direction, a similar phenomenon has been confirmed for scattering in the transmission direction when the face plate 1 is transparent.Using the above phenomenon, stripe defects can be detected. Theoretically, it is possible to detect the light scattered by the defect by placing the entire receiver on the extension line of the arrow showing the scattered light 6°6' due to the defect in Figs. 8 and 9, but in practice, the following There is a technical problem. L Figure 10 (Al) schematically shows a method for detecting all stripe defects using the above-mentioned principle. If there is a stripe, each stripe 2 making up the stripe f/4' turn 2
(The direction of the laser beam is in the direction perpendicular to
? The scattered light is focused by the light receiving lens 7 from all oblique directions and formed into an image on the light receiving surface of the photoelectric converter 8. However, the diagonal direction mentioned above means that the face plate with the stripe/4' turn 2 is closer to the strike f2' than the perpendicular line on the scanning line (along the line inclined in the direction). The reason why the light receiving direction is set obliquely in this way is to prevent the projected laser beam from directly entering the receiver. Figure 10 (Bl shows the output curve of the photoelectric converter 8) The horizontal axis is the time axis. When the scanning spot passes through the defect C, the photoelectric converter 8 generates a peak output (→, ), so the existence of the defect can be fully detected. However, as mentioned above, In order to detect defects, the scanning direction
<Must be matched. If the angle θ is off as shown in Figure 11 fA1, a part of the light scattered by the normal stripes will be detected and a photoelectric converter output as shown in Figure 11 B will be generated, which can be used to detect defects. hinder. Therefore, in order to put stripe defect detection into practical use that utilizes all of the above-mentioned principles, a simple and highly accurate means is needed to make the laser beam scanning direction X' strictly perpendicular to the stripe 2'. Become. b. Another technical issue for practical application of defect detection based on the above-mentioned principle is that when the laser beam spot is scanned along the X-axis as shown in Figure 10 (A), the detection starting point and It is necessary to accurately detect the two points to E, which is the detection end point.If the detection interval between the above-mentioned imaginary HO and imaginary becomes narrower, the area around the stripe/mother turn 2 overlook the flaws in
Also, if this detection section deviates to the wider side, stripe pattern 2
This is because it is mistaken for a harmless tiger stripe defect outside the area. In the present invention, in order to strictly control the scanning direction of the laser beam to a direction perpendicular to the strike f2', the scanning direction of the laser beam S
one direction detection receiver on X/, scanning line X' and positive;
One direction detection light receiver is provided in each direction forming a negative angle, and one direction detection light receiver is provided on each side of the /4' tan in the scanning direction of the stripe pattern.
A light receiving system consisting of a light receiving lens and a photoelectric converter for detecting scattered 'yfS caused by stripe defects is installed in the direction perpendicular to the image receiving surface as well as in the direction of the stripe. It is characterized by being installed at an angle. Next, an embodiment of the present invention will be described with reference to FIGS. 12 to 14. As shown in FIG. 12, a direction detection light receiver A19-1 is provided on an extension of the scanning line X'. And the above scan,
ii Light receivers A29-2 and Aa9-a for direction detection in the directions of hexagonal θ above and below x/ in the drawing, respectively.
Q shown in the figure is a point on the scanning line.As shown in FIG. 13, a light receiver A9 and a light receiver Bl ( However, in this embodiment, the above-mentioned light receiver A9 is also used as the above-mentioned direction detection light receivers A and kl. Fig. 14 is an elevational view schematically showing this embodiment. In the example, the face plate 1 is made of a transparent glass material.The laser beam 4 is reflected by a vibrating mirror 13 to sweep the angle, and is focused on the face plate 1 by a scanning lens 14 for scanning. Unofficial notice

[Although not shown, the stripe pattern is formed on the face plate] σ) The laser beam is formed on the lower surface, and the laser beam passes through the face plate 1, irradiates the stripe pattern 2, and is scattered. Scattered light 6
In order to detect the
The light receiving system 25 is fixed below the face plate 1 at a slight angle in the stripe direction (direction perpendicular to the plane of the paper in this figure) than the direction perpendicular to the face plate 1. This prevents the radar light transmitted through the face plate 1 from directly inputting into the light receiving system B. In this figure, 10 is the aforementioned light receiver B, 9 is the light receiver A,
, A2. It is AS. FIG. 15 shows the light reception signals appearing on the 13th factor, the (provided) light receiver B10 for detecting armpit tongue width, and the light receiver A9, with time plotted on the horizontal axis. When the scanning spot moves in the X direction and passes the scanning start point (d) and (t), a light reception signal CB is sent to the light receiver BIO.
appears. The above light reception signal CB) is a stripe/4'
It moves according to the pitch of the tongue 2, and attenuates as the scanning point moves away from the body. A vibrating signal [A] appears on the receiver A9 for width detection,
As the scanning point approaches the point, the field of view increases, and the signal (A) disappears at time t when the scanning point passes the point. The above signals CB) and (A) are processed as follows to obtain data from scanning start time to to scanning end time 1. A dart signal G is generated for the period up to this point. As shown in FIG. 16, the received light signals [A] and CB)' are subjected to A-pulse shaping only by the shaping circuit 1, and are counted by the counter 12 at the next stage. A number n' is stored in advance in the counter 12, and when the number of pulses reaches U, a pulse 4' is output. As a result, the light receiver B 10 for detecting the width
At the time t shown in the figure, the optical receiver A9 is 1
．． iJ at this point? Lus p,? , each occurs 15 times. Since the scanning speed is constant, in the second and subsequent scans, tJ time A? A dart signal G't-start is started at time t7 using a known technique using a pulse signal Po, and a dart signal G't-stop is started at time t (see FIG. 12). The sample is placed on a rotating stage (not shown). When the above stage is rotated, three direction detection receivers A19-
1. The outputs of A2 9-, , l and Al'lLg each change in accordance with the above rotation. The rotation angle of the stage (not shown) and the three types of light reception signals (A,
), (At), and (As) are shown in FIG. The direction of the stripes in stripe pattern 2 is the scanning line
When aligned correctly in the direction perpendicular to ' (point O on the horizontal axis in Figure 17), [A,] becomes maximum (As), (
Since As) becomes zero or very small, this signal (Al)
, (At), (^] and to control the rotation of the stage so that the direction of the stripe pattern 2 is orthogonal to the scanning line X' is easily possible using known techniques. An example of a block diagram for inspecting a stripe pattern using the mother tongue defect inspection apparatus according to the present invention configured as above is shown in Fig. 18. Light receivers A19-t + Ai9-t, A89
-8 output signals are input to the angle signal circuit 16, and a positive or negative angle signal is created using these output signals. Details I,
7< detects the deviation of the angle of the stripe gloss by comparing the three signals, creates a positive or negative angle signal representing the direction of deviation, and inputs it to the microcomputer 17. The microcomputer 17 converts the above-mentioned angle signal into a rotation control signal and instructs the motor 19 via the driver 18 to rotate the stage metal on which the entire face plate is mounted so that the direction of the stripe gloss is in the direction of the scanning line. Automatic adjustment is performed so that it is orthogonal to the The output signal of the light receiver Al 9-1 and the output signal of the light receiver BIO are inputted to the counters 12 and 12' through the shaping circuits 11 and 11, respectively, as described in FIGS. 15 and 16. Microcomputer 17
A dirt signal is created in , and used for processing the defect detection signal described below. After making the preparations as described above, the microcomputer 17 gives commands to the drivers 21 and 22 via the control circuit according to a predetermined program to cause the laser projection light to scan in the X direction and the Y direction. When the spot of the laser projection light scanned as described above passes through a defective portion of a stripe or a turn, scattered light enters the photomultiplier tube 15 . The photomultiplier tube 15
The detection signal is input to the signal processing unit via the preamplifier 23. The signal processing unit 24 performs pre-processing such as rough classification of the degree of defect based on the peak value of the defect signal using a known technique, and then inputs the defect signal to the microcomputer 17 . Accordingly, the microcomputer 17 configures the stripe pattern 1. Defects in stripes can be detected. As explained above, the present invention provides means for scanning a laser beam in a direction perpendicular to the direction of the stripes, and one laser beam is provided on one side of the /4' tongue in the scanning direction on an extension line of the above scanning line. In addition to providing a direction detection light receiver, two direction detection light receivers are provided at positions facing each other across the above extension line, and one 9-tone sensor is installed on each side of the pattern in the above scanning direction. A light receiver for width detection is provided, and a light receiving system consisting of a light receiving lens and a photoelectric converter for detecting scattered light of laser light caused by stripe defects is provided separately from the above, and the optical axis of the light receiving system is set as described above. Defects in the stripe pattern can be automatically detected by tilting it closer to the stripe direction than in the direction perpendicular to the /IP tan surface.

[Brief explanation of drawings]

Fig. 1 is a plan view of the striped glossy tan, Fig. 2 is an enlarged cross-sectional view of the stripe pattern, Fig. 3 is an enlarged plan view of a short circuit defect in the stripe, Fig. 4 is an enlarged plan view of a disconnection defect in the stripe, FIG. 5 is a perspective view depicting the state of scattering of laser light by the stripe, FIGS. 6 and 7 are charts showing the scattering characteristics of normal stripes, and FIG. 8 is a perspective view showing the state of scattering in a short-circuit defect of the stripe. FIG. 9 is a perspective view showing the scattering state in a stripe breakage defect; FIG. 10 is a schematic diagram showing the arrangement of the scattered light detection member;
Figure 11 (Al is a schematic diagram showing the state where the direction of the stripe button is out of alignment, Figure 11 (Bl is the side of Figure 10) showing an example of the detected waveform in Figure 10. FIG. 12 is a diagram illustrating the arrangement of a light receiver for direction detection in an embodiment of the present invention; FIG. FIG. 14 is an elevational view schematically showing the arrangement of constituent members in an embodiment of the present invention, and FIG. 15 is an example of the output waveform of the receiver for i4 tongue width detection in an embodiment of the present invention. FIG. 16 is an explanatory diagram of the processing of the output wave described above, FIG. It is an operation block diagram in an example. 1... Face plate, 2... Stripe tongue, 2'...
・Stripe, 2"...Stripe edge, 3-1・
...Stripe defect, 3-2... Stripe disconnection defect, 4... Laser beam, 4'... Spora), 5.6... Scattered light, 7... Light receiving lens, 8...
・Photoelectric converter, 9-1...Photodetector Al59-2...
・Receiver A2.9-I+...Receiver edition, 10...Receiver f6B, 11...Shaping circuit, 12...Counter, 1
3... Vibration □ Mirror, 14... Scanning lens, 15... Photomultiplier tube, δ... Light receiving system, Ah... Same elemental axis. Patent Applicant Hitachi Electronic Engineering Co., Ltd. Representative Patent Attorney Tadashi Akimoto Real Department 111 Figure 2 Figure 3 Figure 4 Figure 8, 9F! ! A To T To T

Claims (1)

[Claims] Stripes! This inspection device detects defects in the stripe by irradiating laser light onto the stripe, and includes means for scanning the laser light in a direction perpendicular to the direction of the stripe. One direction detection light receiver is provided on one side of the tongue and on the extension line of the above scanning line, and two direction detection light receivers are provided at opposing positions across the above extension line, and , one photoreceiver is provided on each side of the pattern in the scanning direction for detecting the width of the four stripes, and a photoreceptor system consisting of a photoelectric converter and a photoreceptor lens for detecting scattered light of laser light caused by stripe defects is provided. A pattern defect inspection apparatus characterized in that the optical axis of the light receiving system is tilted closer to the direction of the stripe than the direction perpendicular to the surface of the pattern.