JPS59180345A - Surface inspecting device - Google Patents

Abstract

PURPOSE:To detect accurately a linear flaw in a photoscanning direction by storing a scanning signal of every scan and comparing it with the signal of the last cycle for decision making, and deciding on the distribution of decision signal in the flow direction of a body to be inspected. CONSTITUTION:The output of an arithmetic circuit 24 is compared by a comparative decision circuit 25 with a set value from a setting circuit 26 synchronously with the body 13 to be inspected. This comparative decision result is tracked by a tracking circuit 27 in the movement direction and stored. The output of the tracking circuit 27 is supplied to discrimination circuit 28, which discriminate on the kind of a flaw on the basis of the distribution of comparative decision results stored in the circuit 27 in the movement direction of the body 13 to be inspected. Namely, when, for example, >=3 continuous decision results which are stored indicate the presence of flaws, the decision on a surface flaw 4 is made, and when <=2 results indicate the presence of flaws, a discrimination on flaws 3 and 3' in the scanning direction of a laser beam 1 is made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface inspection device that optically detects surface defects on a moving object.

[Technical background of the invention and its problems]

For example, surface defects on the test object 1, such as a steel plate or an aluminum plate formed by a rolling mill, include linear flaws such as welding marks and folds, as shown in Figure 1 (A), and dirt, etc. There is an areal flaw 4, and regarding linear flaws 2 and 3, there is a flaw 3 that occurs in a direction perpendicular to the running direction of the subject and other flaws 2.

An optical surface inspection device optically scans the object to be inspected in the width direction, detects reflected light reflected from the width direction and inner surface of the object, differentiates the detection signal, and extracts a flaw signal.

In this method, as shown in FIGS. 1(C) and (D), it is possible to identify and detect area defects 4 such as dirt or linear defects 2 that are not orthogonal to the running direction of the object 1. , perpendicular to the traveling direction of the subject 1 shown in FIG. 1(B). That is, it was difficult to detect a linear flaw 2 that coincided with the optical scanning direction.

In other words, since the linear flaw 2 that coincides with the optical scanning direction appears as a change in the scanning signal level for each scanning, it is difficult to detect it simply by differentiating the signal for one scanning.

[Purpose of the invention]

The present invention provides a surface inspection device that can accurately detect linear flaws that coincide with the optical scanning direction.

[Summary of the invention]

The present invention stores all scanning signals for each scan.

A surface inspection that makes it possible to separate and detect linear flaws that match the scanning direction from other flaws by comparing the signal with the signal from one cycle before and determining the distribution of the judgment signal in the flow direction of the object. It is a device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

Reference numeral 10 denotes, for example, a laser light source, and a laser beam 11 from this laser light source 10 is irradiated onto the surface in the width direction of a traveling subject 13 by means of a multifaceted rotary mirror 12.

Namely.

The width direction of the subject 13 is scanned by the laser beam 11. This laser beam 11.

After the amount of light changes due to reflection and absorption on the surface of the object, it is detected by the detection head 14.

The signal detected by this detection head 14 is supplied to a filter circuit 16 via an amplifier 15. This filter circuit 16 removes noise components from the detected word (see Fig. 1).
D) Removal and smoothing (indicated by niote code ■N).

This smoothed detection signal is obtained by proportionally integrating the signal,
N conversion circuit 17 that converts N after holding the integral value
is supplied to. The output of this lv'D conversion circuit 17 is supplied to a register group 20 at the subsequent stage.

This register group 20 has the same number of registers 21 as the mirror surfaces of the rotating mirror 12, and each register 21 and the A/D conversion circuit 17 are connected to each other.

It is switched in synchronization with the rotation of the rotary gear 2.

That is, each register 21 stores 7%M signals corresponding to each mirror surface of the one-rotation mirror 12.

Each of these registers 21 is further connected to a register 22 . These registers 22 are register 2
This is for storing and holding the N-1 cycle signal stored prior to the N cycle signal supplied to the memory cell 1. The output of these registers 22 and the register 21
The output is supplied to the subsequent arithmetic circuit group 23.

This arithmetic circuit group 23 has the same number of arithmetic circuits 24 as the number of registers 21 or 22, respectively. Each of these arithmetic circuits 24 calculates the difference between two consecutive cycles of signals for each mirror surface of the rotating mirror 12.

In this way, the signals for each mirror surface are compared.

This is to eliminate errors caused by differences in reflectance on each mirror surface of the rotating mirror 12. of course.

If it is possible to make the reflectance of each mirror surface exactly the same,
There is no need to compare each mirror surface in this way.

However, as shown in FIGS. 3(A) and 3(B), the reflectance of each mirror surface is generally different, and even if they are manufactured identically, the reflectance will change economically. Figure 3 (B) is the same figure (
It is a waveform diagram showing the reflectance corresponding to each mirror surface A9 shown in A).

The output of each of these arithmetic circuits 24 is connected to the rotating mirror 12 in the same way as the connection state between the ~Φ converter 17 and the register 21.
is retrieved in sync with The outputs of these arithmetic circuits 24 are as follows.

The comparison and determination circuit 25 compares the set value with the set value from the setting circuit 26 in synchronization with the subject 13 .

The comparison and determination results are tracked and stored in the moving direction by the tracking circuit 27, as shown in FIG. 4(B). Figure 4'(A) is.

The object 13 is shown not for each scan but for each predetermined unit of movement of the object 13.

In addition, the same figure (B) shows the tracking circuit 2 of the molecule iI.
The part showing the memory state of 7 and marked with the middle layer line of the memory content is as follows:
It shows that there is a defect. The output of the tracking circuit 27 is supplied to the discriminating circuit 28 at the subsequent stage, and the tracking circuit 27
The type of flaw is determined from the distribution state of the comparative judgment results stored in 7 in the moving direction of the object 13.

That is, if the memorized determination results indicate that there are three or more flaws in a row, it is determined that there is a one-sided flaw 4, and if there are two or less, the flaw is determined to be one-sided flaw 4. It is identified as flaw 3,3 which has occurred on the surface.

〔Effect of the invention〕

Since the present invention is configured in this manner, linear flaws generated in the direction f that coincides with the nine-dimensional scanning direction can be detected separately from other flaws.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the condition of the surface of the object to be inspected and the waveform of the detection signal corresponding to each type of flaw, and FIGS. 2 to 4 illustrate an embodiment of the present invention. FIG. 2 shows the circuit configuration. Figure 3 is a diagram illustrating the reflectance of each mirror surface of the rotating mirror that scans the laser beam, and Figure 4 is a diagram illustrating the distribution of judgment results corresponding to the type of flaw. 10... Laser light source 11... Laser beam 12... Polygon mirror 13... Subject 14... Detection head 20...・Register group 23... Arithmetic circuit group 25... Comparison/judgment circuit 26... Setting circuit 27... Tracking circuit 28... Discrimination circuit Agent Patent Attorney Kensuke Chika (and 1 other person) No. 4
Figure (A) 3 (B)

Claims (1)

[Claims] In a surface inspection device that inspects the surface of an object by optically scanning the object surface in its width direction and detecting reflected light from the object surface with a detection head, a scanning signal from the detection head for each scan is stored. means for comparing and determining the stored scanning signals for each successive scanning signal or for each predetermined movement unit of the object; A surface inspection device characterized by comprising: means for detecting.