JPH0619336B2 - Surface inspection device - Google Patents

Description

The present invention relates to a surface inspection device used for detecting surface defects of a rolled metal plate.

Conventionally, there is a device shown in FIG. 1 as this type of device. In FIG. 1, 1 is an optical system sensor using a laser, 2
Is a laser beam emitted from the optical system sensor 1 to the inspected plate 3, 4 is a pulse generator that converts the moving distance of the inspected plate 3 into the number of pulses, 5 is an amplifier that amplifies the output signal from the optical system sensor 1, Reference numeral 6 is a waveform shaping circuit, 7 is a comparison circuit for extracting a defect signal, 8 is a gate circuit for determining an inspection region, 9 is a first flip-flop circuit, and 10 is a value 1 of a first set value 11 for defect break determination. A defect break detection counter circuit for detecting the length of the discontinuous portion of the defect, 12 a defect length detection counter circuit, 13 a first latch circuit for extracting and accumulating defect data of the defect length detection counter circuit 12, Reference numeral 14 is a microcomputer circuit that collects defect data of the first latch circuit 13 and determines the degree of defect.

Next, the operation will be described. In addition, here, the plate 3 to be inspected
The case of inspecting vertical scratches that occur in a direction parallel to the traveling direction of will be described.

The laser beam oscillated at high speed inside the optical system sensor 1 is scanned in the plate width direction of the plate 3 to be inspected such as a running rolled metal plate, and the reflected light is converged inside the optical system sensor 1. After that, photoelectric conversion is performed and an electric signal is output. This electrical signal shows a steady level with respect to the normal surface of the plate 3 to be inspected, and appears as an abnormal level if any defect (vertical scratch in this case) exists in the plate 3 to be inspected. Although the presence of a defect is recognized by detecting this abnormal level signal, not only the presence of the defect but also the length of the defect is detected to determine the degree of the defect.
The signal output from the optical system sensor 1 is amplified by the amplifier 5, shaped by the waveform shaping circuit 6 to facilitate the extraction of the defective signal, and then compared by the comparison circuit 7 with a predetermined level. A pulsed defect signal is extracted.

In order to detect the length of the defect, it is necessary to know the moving distance of the plate 3 to be inspected. For this reason, the pulse generator 4 is attached to the traveling line of the plate 3 to be inspected, and the plate 3 to be inspected moves a unit length. One pulse signal is output every time. Each time this pulse signal arrives, the gate circuit 8 is opened in synchronization with one scanning of the laser beam. A defect length detection counter circuit 12 outputs a defect signal output every time the inspection plate 3 moves a unit length.
Count with.

On the other hand, once the defect signal is generated, the first flip-flop circuit 9 is reset by the pulse of the defect signal from the gate circuit 8 and operates so as to be set by the output pulse of the pulse generator 4. While the first flip-flop circuit 9 is set, the defect break detection counter circuit 10 counts the output pulses of the pulse generator 4. When the count number reaches the value 1 of the first set value 11, the defect break detection counter circuit 10 outputs a signal and determines that the defect is interrupted. After the data of the defect length detection counter circuit 12 is latched in the first latch circuit 13 by the output signal of the defect break detection counter circuit 10, the defect length detection counter circuit 12 is cleared.
The data obtained in the first latch circuit 13 is the accumulated length of only the portion detected by the optical system sensor 1 for a defect having a certain length, and this data is fetched by the microcomputer circuit 14 for one defect. The degree is judged.

FIG. 3 (A) shows a case where a continuous defect is detected, 20 is a vertical flaw as a continuous defect having a length L, P is a defect signal pulse generated for each unit length, and a is the inspection target plate 3 The direction of travel.

FIG. 3 (B) shows the case of detecting a discontinuous defect.
a, 20b, 20c, and 20d are vertical scratches as discontinuous defects, which have lengths L ₁ , L ₂ , L ₃ , and L ₄ , respectively, and are generated with intervals l ₁ , l ₂ , and l _3. ing. here,
l ₁ , l ₂ and l ₃ are smaller than the value l of the first set value 11.

In the case of the continuous defect shown in FIG. 3 (A), the first latch circuit 1
In 3, the value of the length L of the vertical scratch 20 is latched as defect data. In the case of the discontinuous defect shown in FIG.
The latch circuit 13 latches the total length L ₁ + L ₂ + L ₃ + L _{4 of the} vertical scratches 20 a to 20 d.

FIG. 4 is an operation explanatory view when the defect is displaced in the plate width direction, and FIG. 5 is a view showing an output signal of the waveform shaping circuit 6 corresponding to FIG. In the figure, 30 is a beam scan in the forward direction, 31 is a beam scan in the backward direction, 32 is a normal surface signal, 3
Reference numeral 3 denotes a defective portion signal, and (a), (b) and (c) in FIG. 4 correspond to (a), (b) and (c) in FIG. 5, respectively. Further, in FIG. 5, H corresponds to the inspection width.

Next, the operation will be described. The signal after photoelectric conversion at the time of forward beam scanning 30 in which the laser beam is scanned in the plate width direction on the inspected plate 3 shown in FIG.
It looks like Figure 5.

A defective pulse signal is obtained by passing the signal through the comparison circuit 7. Then, similar to the measuring method described above, the defect detection pulse signal detected first in the defective portion is used as a basis to measure the length of the defective portion, the length of the defect cut, and the like.

Even if the defects are displaced in the plate width direction as described above, if the defects occur within the inspection width, they are treated as the same discontinuous defects as when the defects are continuous on a straight line. ing. For more precise measurement, the inspection width may be narrowed or the defect detection pulse signal may be electrically divided.

The inspection width ranges from about 30 cm to about 150 cm. Generally, when the inspection width per unit is 30 cm and it is wide, the inspection units are arranged side by side in the lateral direction. Therefore, the discontinuous defects that frequently occur within the inspection width of about 30 cm are
The spread of defects inside the plate to be inspected is expected, and the detection direction becomes effective.

Although the case of vertical scratches has been described here, both types of scratches can be detected. However, in general, a rolled metal plate is apt to cause vertical scratches, and the one corresponding to horizontal scratches has many surface stains. For vertical scratches, the degree of importance is judged by the length of the defect, and for horizontal scratches, the degree of importance is judged by the width and length of the defect. Therefore, in this specification, the case of vertical scratches will be described.

Since the conventional apparatus is configured as described above, the degree of the defect is determined by the cumulative length of the portion detected by the sensor for one continuous and discontinuous defect, and in the case of the discontinuous defect, the interval l ₁ , L ₂ , l ₃ are determined to be shorter than the entire length, and thus the defect may be determined to be mild. In the case of a rolled metal plate, the discontinuous defects are often serious defects including internal defects, but conventional devices have drawbacks such as oversight and judgment as mild defects.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional apparatus, and even in the case of a discontinuous defect, a circuit for detecting the total length from the beginning to the end of the defect is provided, and further, the total length and the accumulated length are accumulated. An object of the present invention is to provide a surface inspection apparatus that has a function of calculating a difference in length and inspecting it as a serious defect if it is a certain value or more, and capable of accurately determining a serious defect.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2 in which the same parts as those in FIG. 1 are designated by the same reference numerals, 15 is a second flip-flop circuit, and 16 is a total detecting the total length from the beginning to the end of one defect (continuous defect or discontinuous defect). A length detection counter circuit, 17 is a second latch circuit for taking out the data of the total length detection counter circuit 16, and 18 is a second set value for the microcomputer circuit 14 to judge the degree of defect.

In FIG. 2, the signal optically detected by the sensor 1 is subjected to various signal processing as described in FIG. 1 to obtain a defect signal. The defective signal that has passed through the gate circuit 8 sets the second flip-flop circuit 15 and enables the total length detection counter circuit 16 to count. The total length detection counter circuit 16 is the second flip-flop circuit 1
While 5 is set, the output pulse of the pulse generator 4 is counted.

On the other hand, when the defect break detection counter circuit 10 determines the defect break length l and outputs a signal, the second flip-flop circuit 15 is reset, and at the same time, the data of the total length detection counter circuit 16 is transferred to the second latch circuit 17. Get caught. At this time, the data taken into the second latch circuit 17 is the data obtained by adding the value 1 of the first set value 11 to the total length from the beginning to the end of one defect. At the time when the defect break is determined, the data of the detected cumulative length of one defect is taken in by the first latch circuit 13, and the data of the total length is taken in by the second latch circuit 17.

The microcomputer circuit 14 takes out these data and judges the degree of defect. In the determination of the degree of defect, the difference between the value obtained by subtracting the value 1 of the first set value 11 from the total length and the cumulative length of the detector is calculated, and this value is calculated as the value k of the second set value 18.
If it is larger than the value k, it is determined that the defect is a severe defect and the degree of the defect is determined based on the value of the total length.

According to this embodiment, in the case of FIG. 3A, the value of L is latched by the first latch circuit 13 and the value of L + 1 is latched by the second latch circuit 17. Further, in the case of FIG. 7B, the first latch circuit 13 has L ₁ + L ₂ + L
The value of ₃ + L ₄ is latched and L ₁ is set in the second latch circuit 17.
The value of + L ₂ + L ₃ + L ₄ + l ₁ + l ₂ + l ₃ + l = L ₀ is latched. Therefore, when L ₀ −l− (L ₁ + L ₂ + L ₃ + L ₄ ) ≧ k, it is determined to be a discontinuous defect.

Here, the defect of FIG. 6 will be described in detail with reference to the timing chart of FIG. It should be noted that this timing chart shows only the signal portion selected in synchronization for each unit length. In the figure, 61 is a defect such as a flaw having a length of 5, 62 is a defect such as a flaw having a length of 4, 63 is a defect such as a flaw having a length of 3, 71 is a value obtained by converting the distance from the defect occurrence into a numerical value,
72 is an output waveform of the waveform shaping circuit 6, 73 is a gate circuit 8
Output waveform, 74 is the output waveform of the pulse generator 4,
Reference numeral 75 is the output waveform of the flip-flop 9, 76 is the output waveform of the defect break detection counter 10, 77 is the output waveform of the defect length detection counter 12, 78 is the output waveform of the flip-flop 15 by the additional function of the present invention, and 79 is the same. 7 is an output waveform of the total length detection counter 16 according to the additional function of the present invention.

Three defects are generated as shown in FIG. 6, and whiskers are first generated at positions corresponding to these defects as shown by the output waveform 72. Further, a pulse-shaped defect signal is taken out at a timing corresponding to the defect as shown by an output waveform 73 through the comparison circuit 7 and the gate circuit 8. In response to such an output, as shown in the output waveform 75, the flip-flop 9 generates a pulse only at a timing having a defect. From the output of the flip-flop 9, in the defect break detection counter 10, as shown by the output waveform 76, while the pulse waveform of the output of the flip-flop 9 is interrupted, that is, the number of pulses 3, 2 corresponding to the defect break distance. , 1 will be counted. On the other hand, the defect length detection counter 1
In 2, the output of the gate circuit 8 is counted to derive a value obtained by adding the lengths of defects as shown in the output waveform 77. In this case, the value 12, which is the sum of the values corresponding to the lengths of the defect 1, the defect 2, and the defect 3, is counted. Further, in the total length detection counter 16, when the defect break detection counter circuit 10 determines a preset value 1 = 7, the second flip-flop circuit 15 is reset as shown by the output waveform 78, and at the same time, the total length detection counter is reset. The 16 data values 24 are taken into the second latch circuit 17. This value 24
By subtracting the initial setting value of 7, the total length of the defective portion of 17 is obtained.

In this way, the cumulative length 12 of the defective portion and the total length 17 of the defective portion are obtained, and by comparing the difference and the set value k, it is determined whether or not the defect is a discontinuous defect. Therefore, as compared with the conventional method in which only the cumulative length 12 of the defective portion is used, it is possible to accurately determine the degree of the defect with respect to the discontinuous defect.

Although the counter and its associated control circuit are shown as the total defect length detection circuit in the above embodiment, the present invention is not limited to this, and a microcomputer, a memory, an addition circuit, an arithmetic circuit or the like may be used as this circuit. good. Further, although the microcomputer circuit is used for the defect degree determining portion, the same effect can be obtained by combining the logic circuits.

Further, in the above-mentioned embodiment, the flaw inspection device using the laser has been described, but the sensor portion may be a general optical detection sensor and the same effect as that in the above-mentioned embodiment can be obtained.

As described above, according to the present invention, in order to detect the length of one defect, a circuit configuration capable of detecting the total length in addition to the cumulative length of the defects detected by the sensor portion is added. By combining this data, it is possible to accurately determine the degree of defects even for discontinuous defects that have occurred in a series of metal plates or the like. That is, small defects frequently occur in the discontinuous defect continuous at intervals within the defect break detection length, and a function for determining an important defect is added when the cumulative length of the discontinuous portion is a certain value or more, This has the effect of providing a highly reliable surface inspection device.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of a conventional laser type surface inspection apparatus, FIG. 2 is a block diagram showing the construction of a laser type surface inspection apparatus according to an embodiment of the present invention, and FIG. 3 is a conventional and inventive apparatus. 4 is an explanatory view of the operation of the conventional device and the device of the present invention, FIG. 5 is an explanatory view of the operation of the conventional device of the present invention, and FIG. 6 is a simplified diagram showing an example of a defect, FIG. The figure is a timing chart showing the operation of the device of the present invention. 1 ... Optical system sensor, 4 ... Pulse generator, 7
...... Comparison circuit, 8 ...... Gate circuit, 10 …… Defect break detection counter circuit, 12 …… Defect length detection counter circuit, 14 …… Microcomputer circuit, 16 …… Defect total length detection counter circuit, 30 ・ ・ ・... beam scanning in the forward direction, 31 ... beam scanning in the backward direction, 32 ... normal surface signal, 33 ... defective portion signal. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A sensor for optically scanning the surface of a continuous metal plate or the like to detect a change in reflected light thereof, and a pulse generator for converting the amount of movement of the metal plate or the like into the number of pulses.
A comparator circuit for comparing the output of the sensor with a predetermined level to extract a defect signal, a gate circuit for determining inspection timing based on the defect signal from the comparator circuit and the output pulse of the pulse generator, and the gate circuit. A defect length detection counter circuit that counts the defect signal that has passed through, and a defect that outputs a signal when the output pulse of the pulse generator is counted during a period in which the defect signal that has passed through the gate circuit is interrupted and a predetermined set value or more is counted. A break detection counter circuit, and a defect total length detection counter circuit that counts the output pulse of the pulse generator in the period from when the defect signal passes through the gate circuit to when the signal is output from the defect break detection counter circuit. , The defect total length detection counter circuit data and the defect length detection Surface inspection device provided with a microcomputer circuit to weight data and the comparison both to the defect approximately determined as discontinuous defect If there is a difference above a certain counter circuit.