JPS5920972B2 - Defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defect detection device suitable for determining the quality of a strip material.

Defects are detected by scanning the width of the strip while it is running, and the number or length (length in the longitudinal direction of the strip) of defects included in the strip is determined for each fixed length of the strip. A method is commonly used in which if the total exceeds a certain set limit, then the entire length of the strip is rejected.

According to this method, for example, the three types of defects shown in Figure 1 a, b, and c cannot be distinguished5. In these figures, z represents a strip material and e represents a defect. In Figure 1a, the defect is a single line with a length of X, and in Figure 1B, there are five scratches lined up on one line in the width direction, and the sum of the lengths of each scratch is x. In Figure 1c, two scratches are lined up in the width direction and the other two scratches are at band 10.
The sum of the lengths of each scratch in the length direction is equal to x. In all three cases, defects (
When determining pass/fail based on the total length of scratches, all of them are judged to be of the same quality. However, in reality, depending on how the strip material is used, due to factors such as material removal, Fig. 1 a is defective, but Fig. 1 b is a good product if only the scratches are cut out, or Fig. 1 a is a good product. There are various cases, such as good and bad, and it is unreasonable and uneconomical to judge them uniformly based on the total length or total number of scratches, etc. 20 The present invention detects defects in a strip material and processes the detection signal appropriately to reveal the differences in the distribution pattern of defects as shown in Fig. The aim is to make it possible to make something.

25 The present invention provides that in a given length or total length of a strip material, the total number or total length of defects and the number of defects lined up on one width direction line of the strip material are one (or one unit) regardless of the number. According to the present invention, the total length of defects in a given length of a strip material is L,
Defects lined up in a row in the width direction are treated as one defect (one unit length).If the total length of the defects is l, then in Figure 1a, L=1.
And in the same b, 35L>1 (specifically 1=L15)
, and in the same c, L>1, but in this case l is the first
It is larger than l in the case of Figure b.

In this way, the distribution state of defects can be grasped from the magnitude relationship of L)l and the ratio of 1 to L. The present invention will be explained below with reference to Examples. In FIG. 2, z denotes a strip of material to be inspected, which is scanned in a direction perpendicular to the plane of the drawing, and 1 denotes a defect detector.

This defect detector creates an optical image of the strip z, scans it in the width direction of the strip, and obtains a video signal by photoelectric conversion. This signal is amplified by an amplifier 2 and then level-selected by a discrimination circuit 3 to detect defects. FIG. 3a shows the video signal, and the range T corresponds to one scan.
V8 is the defective signal. FIG. 3b shows the defect signal from FIG. 3a by level selection. This is only an excerpt. If the defect extends long in the length direction of the strip, the defect signal appears at the same location every scan of the video signal. Therefore, by counting the signals shown in FIG. 3b with a counter, the total length of the defects can be obtained. The rising edge of the output of the amplifier 2, that is, the video signal shown in FIG. Ru. The output of the discrimination circuit 3, that is, the signal shown in FIG. 3b is applied to the set input terminal of the flip-flop. The delay time of the delay circuit 5 is designated as t in FIG. Flip-flop 6 is therefore set with the signal of FIG. 3b and reset at the end r of one scan of the video signal. Figure 3c
d indicates the output signal of the delay circuit 5, and d indicates the set output of the flip-flop 6. The flip-flop 6 is set when a defect detection signal is output from the discrimination circuit 3, and remains set no matter how many times a defect is detected during one scan.Since it is reset at the end of the scan, the set output of the flip-flop 6 is is a signal that is calculated as one defect when the defects are arranged in a row in the width direction of the strip material. Therefore, when the output of the discriminator 3 (FIG. 3b) is counted by the counter 7 and the set output of the flip-flop 6 is counted by the counter 8, the counter 7 represents the aforementioned L, that is, the total length of the defect, and the counter 8 represents the widthwise direction. The total length of defects calculated as one defect lined up is 1.

A pulse generator 9 rotates in contact with the strip material z, and outputs one pulse signal every time the strip material z travels a certain length, thereby resetting the counters 7 and 8.

Comparators 10 and 11 are set to a constant number in advance, and the count output of either counter 7 or 8 is compared with the constant number, and when it exceeds the constant number, a signal is output from the corresponding comparator.
This is sent to the recorder R as a defective signal through the OR circuit 0R.
and recorded along with the signal for the unit length of the strip.

The numbers set in the comparators 10 and 11 are, of course, independent of each other, and can be arbitrarily selected depending on the use of the strip material, etc. The device of the present invention has the above-mentioned configuration, and it not only quantifies and represents the total number and total length of defects per unit length of a strip material, but also the difference in the distribution pattern, so it can be used to quantify and express the differences in the distribution pattern. It will be possible to judge whether it is good or bad.

[Brief explanation of drawings]

Fig. 1 is a diagram showing three typical distribution patterns of defects in strip material, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a time chart explaining the above operation. ...
... Strip material to be inspected, 1 ... Defect detector, 9
...Pulse generator, R...Recorder.

Claims (1)

[Scope of Claims] 1. A defect detector that scans a moving object to be inspected in the width direction, a means for outputting a response signal to only the first defect detection signal in one scan, and a moving object to be inspected. A device for counting the detection signals of the defect detector over the entire length or a certain length of the inspection material, a device for counting the response signals, and a device for counting the outputs of each of the counting devices, each having a preset constant number. What is claimed is: 1. A defect detection device comprising: a comparator for comparing the 1. 2. Claims in which the means for issuing a response signal only to the first defect detection signal in one scan of the defect detector is a flip-flop that is set by the first defect detection signal and reset after the scanning is completed. The defect detection device according to item 1.