JPS5822941A - Surface defect inspecting device - Google Patents

Abstract

PURPOSE:To specify the same defect even in case when a sample is vibrating, by standardizing a measured time width and a standard signal width. CONSTITUTION:Reflected rays from a sample by scanning light are photodetected by a photoelectric element 21, are processed by a rise detector 24, a signal width detector 26 and a defective position detector 27, and a signal width T and a time width DELTAT to a defective position are detected. In accordance with these width T and DELTAT, time width DELTAT0 corresponding to a standard signal width T0 is operated and calculated in a defect generated position standardizing circuit 28, and even in case when the sample vibrates and the width T and DELTAT are varied to T', DELTAT', etc., the time width DELTAT0 is specified.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface defect inspection device that inspects surface defects by irradiating light onto an object to be inspected. However, it relates to a signal processing method for determining that the defects are the same.

A conventional surface defect inspection device is shown in FIG.

FIG. 1 is a conceptual diagram showing the configuration of a conventional surface defect inspection apparatus, in which 1 indicates the object surface of the object to be inspected, and 2a.

Reference numeral 2b denotes a support member that supports the object to be inspected and suppresses its displacement, and is composed of, for example, a roller, a die, etc. When the object to be inspected is displaced, it is displaced as shown in the figure with this supported point 2c as the center of rotation. do.

3 is a light source, 4 is incident light, 5 is an irradiation point on the object surface 1,
6 is the reflected light, T is the photodetector, 11 is the object surface when the object to be inspected is tilted at an angle θ in the positive direction, 51 is the irradiation point of the incident light 4 at that time, 8 is the irradiation point 5 m A surface 61 parallel to the object plane 1 that passes through receives the reflected light at that time. Also, move the object to be inspected at an angle of 0. The object surface when tilted is 1b, its irradiation point is 5b, the parallel plane passing through this irradiation point 5b is 9, and the reflected light at that time is 6b.

Next, the operation of this device will be explained.

Now, when the inspected object is tilted at an angle θ1 in the positive direction about the support point 2c, looking at the path of the reflected light 6a, the incident light 4 enters the irradiation point 5a at an angle of object surface 1aKα-〇, It is reflected at an angle α-201 with respect to the parallel plane 8. Further, at this time, the irradiation point 51 moves toward the photodetector T by only the beam.

That is, the movement of the irradiation point 51 causes the reflected light 6 stars to reach the photodetector 7.
While it is displaced upward by hl at the incident position,
Since the decrease in the reflection angle moves the incident position of the reflected light 6a downward, the two act to cancel each other out, and the reflected light 6a
and 6a intersect at a certain point.

Next, the object plane 1 moves at an angle of 0 in the negative direction around the support point 2c.
．． Looking at the path of the reflected light 6b when tilted, the irradiation point 5
The position of b moves downward Kh, while the reflected light 6
The reflection angle of b is α+20. Since they are directed upward, they cancel each other out, and the reflected lights 6 and 6b intersect at a certain point.

These two intersection points can be brought close by appropriately selecting the positional relationship between the light source 3 and the support point 2C, and when the object surface 1 is tilted in the positive or negative direction, the path of the reflected light is a narrow surface. It can be made to pass through the area. Therefore, by arranging the photodetector 1 at this position, the reflected light can be detected by a photodetector with a small detection area, and the reflected light can be efficiently collected against vibrations of the object surface 1. Ta.

However, when detecting defects by actually scanning the object surface 1 with light, in many cases the light is converged or spread toward the object surface 1, so it is not affected by the vibrations of the object surface 1. Even if the reflected light is received without being detected, the signal width changes, making it difficult to recognize the location of a defect or to determine whether the same defect is detected from consecutive scanning lines. The second one shows this situation.
It is a diagram.

In FIG. 2, for convenience of explanation, the sample is a plate material, and the optical scanning is a scanning that spreads out in a fan shape from one point, and the scanning angular velocity is constant. In addition, t and m in the figure indicate the scanning line width, and d indicates the plate width.

FIGS. 3A and 3B are diagrams showing the output of a photoelectric element (not shown).

In the wLz diagram, the signal width T obtained at the object plane 1 is the signal corresponding to the ratio of the plate width d to the total scanning line width l of the light, and the third
K as shown in Figure B. However, when the object plane 1 comes to a position where the object plane 1 is inclined at an angle θ1 in the positive direction, the signal width is calculated as the signal width T' corresponding to the ratio of the plate width d to the total scanning line width m of the light. As a result, the pulse width is expanded by 17 m.

Therefore, when there is vibration of the object surface 1, a change in pulse width occurs. For this reason, it is no longer possible to use a method that detects the location of a defect based on the temporal location within the signal width, or a method that identifies the same defect from consecutive scanning lines as a cumulative result. A new form of law was needed.

This invention was made in response to the current situation, and is based on the above-mentioned method of specifying the location of defects from K when all time measurements are made floating, that is, when the measured time width is normalized as a ratio to the signal width. The present invention provides a defect inspection device having a signal processing means that solves the problem.

An embodiment of the present invention will be described below based on the drawings.

Figure 4 is a block diagram of a signal processing circuit that makes time width measurement 70-tings.
In the output signal, the same symbol as the symbol attached to the signal path in FIG. 4 indicates the signal of that part.

In FIG. 4, 21 is a photoelectric element, 22 is an amplifier, and 23 is a photoelectric element.
is a waveform shaper 1.24 is a rising edge detector in the positive direction of the waveform,
25 is also a falling detector in the negative direction, 26 is a signal width detector which is a first time width detection means for detecting the signal width, 2T
28 is a defect position detector which is a second time width detection means for detecting the time width from the start point of the millet synchronization signal S to the defect occurrence position; and 28 is a defect position detector that corrects the output of the signal width detector 2@ to a specified value. At the same time, correction is made to this specified value, the output of the signal width detector 26, and the output of the defect position detector 21, and the defect signal is placed within the corrected specified value output at a temporal position based on the correction result. This is a defect occurrence position normalization circuit which is a means for giving Note that for convenience of explanation, it is assumed that only one defect exists.

In FIGS. 4 and 5, the output from the photoelectric element 21 is amplified by an amplifier 622 to become a signal including defective dips as shown in FIG. Here, the signal is chronologically shown in Figure 3A.
, BK. It is assumed that there has been a change corresponding to BK. The signal is binarized by a waveform shaper 23 having an appropriate slide level, resulting in a signal as shown in FIG. 5E. Here, the positive rising edge detector 24 detects the rising edge of the entire signal and the rising edge of the defective dip, and outputs a signal as shown in FIG. 5F, and the falling detector 25 detects the falling edge of the entire signal, The fall of the defective dip is detected and a signal as shown in FIG. 5G is outputted. The signal width detector 26 receives the output of the synchronization signal S and the signals F and G, detects the time width from the first rising signal to the last falling signal within the range of the synchronization signal S, and detects the time width T' and T, respectively. A signal as shown in FIG. 5H having a time width pulse of . Similarly, the defect position detector 27 detects the time width from the first rising signal to the first falling signal, and each detects ΔT.
', a signal as shown in FIG. 5J having a time width pulse of ΔT is generated. In the defect occurrence position standardization circuit 28 that receives the signals H and J, the signal width is first unconditionally generated as a predetermined standard value of T· with a certain relationship with the synchronization signal S, and ΔT′o=( The following calculation is performed: ΔτXTe)/τ ΔT0=(ΔTXT, )/T, and a signal as shown in FIG. 5 is generated with dips at the corresponding positions of ΔTl and ΔT0. In such a configuration, if the defect signals are from the same defect, the angular velocity of optical scanning is constant, so changes in the overall signal width due to object plane vibration are corrected, and Δ(+1., =ΔT6) in the signal In It is clear that the correction circuit 1 can identify defects even if there is vibration of the object surface 1.

In addition, in the above embodiment, for convenience of explanation, the object surface 1 was explained as being of a plate material, but it is clear that this can be directly applied to the inspection of object surfaces of other shapes such as cylinders.
It goes without saying that the same correction principle can be applied to pigeon lofts where optical scanning is performed in the convergent direction.

Furthermore, it is clear in principle that the same method can be used to standardize and measure the depth of the defect.

Furthermore, it is clear that a pigeon coop where a plurality of defects occur can be dealt with by providing a memory function to the defect occurrence position detector 27 and storing a plurality of time widths. Note that circuit technology for performing defect signal processing based on the output of this correction circuit is well known.

As explained above, in this invention, all the times measured in defect signal processing are normalized by the ratio to the signal width, and the vibration of the object surface is suppressed by generating a defect signal in a pulse with a standard signal width. Defects can be identified even when using the method, and practical effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a conventional surface defect inspection device.
FIG. 2 is an explanatory diagram showing an example in which the surface defect inspection apparatus of FIG. 1 is specifically applied, FIGS. 3A and 3B are waveform diagrams showing the signal width obtained in FIG. FIG. 5 is a diagram showing an example of a signal waveform in each Glock shown in FIG. 4. In the figure, 21 is a photoelectric element, 22 is an amplifier, 23 is a waveform shaper, 24 is a rise detector, 25 is a fall detector, Pro is a signal width detector, 2T is a defect position detector, and 28 is a defect occurrence position. It is a standardized circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno (1 other person) Figure 2 Zc 943 Figure 5

Claims (1)

[Claims] 0) Scanning the surface WK of the object by irradiating it with light, detecting the reflected light, and detecting the signal width between the detection signal obtained each time the object is scanned and the change in the detection signal. 1 time width detection means; a second time width detection means for detecting the time width from the starting point of the synchronization signal to the defect occurrence position in the synchronization signal; The output of the second time width detection means is corrected to a specified value, and the output of the second time width detection means is maintained with a certain proportional relationship between the specified value, the output of the first time width detection means, and the output of the second time width detection means. A surface defect inspection apparatus comprising: means for correcting the output and positioning the defect signal within the corrected specified value output at a temporal position based on the correction result. (2) The positioning means is characterized by comprising means for detecting a defect signal width and applying a certain correction between the defect signal width, the output of the first time width detection means, and the specified value. Claim 1 (Surface defect inspection device according to claim 11). (3) The second time width detection means has a memory function and can correct a plurality of defects. 1) The surface defect inspection device described in item 1).