JPH061168B2 - Shape defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a defective shape portion generated in a strip-shaped body such as a steel plate
The present invention relates to a device for detecting a belt-shaped body while traveling with high accuracy.

[Conventional technology]

Shape defects that occur in strips such as steel plates include those that extend over a certain range, such as inward spreads, side spreads, and waves, but also local defects such as dents, bulges, and folds. When detecting a shape defect of these strips during traveling, various types of shape detectors have been proposed for a shape defect that extends over a certain range, and some of them have been put into practical use. For example, as in JP-A-57-124243, a method of automatically detecting a distortion of an image caused by a defective shape from a video signal by photographing a virtual image of a rod-shaped light source reflected on a belt with a television camera, or a displacement meter for measuring the belt-like shape. A method of detecting a height change is well known. However, although these methods have some action and effect, it is extremely difficult to inspect the surface of the band-shaped body in a two-dimensional manner, and the sensitivity to a minute shape defect is low. It is quite helpless to me. The detection of a local shape defect has hitherto been the role of a so-called optical flaw detector. However, in reality, the optical flaw detector has a very low detection rate of shape defects without such changes as compared with flaws accompanied by changes in surface properties such as color, reflectance, and roughness. Therefore, only a sharp shape defect in which the reflected light is largely disturbed or the direction of the reflected light is largely changed can be detected. Further, these optical flaw detectors are ineffective in detecting a shape defect that spreads slowly and spreads over a wide range like a wave.

Although the strips, such as surface treatment steel sheets and electromagnetic steel sheets, are sufficiently controlled, there are various types and forms of shape defects that occur, as described above. It has been difficult to detect with a sufficiently satisfactory accuracy within the on-site manufacturing line.

By the way, electromagnetic steel sheets are used by stacking in multiple layers,
In order to reduce the loss of magnetic properties as much as possible, the adhesion of the layers is important, and it is necessary to reliably remove the defective shape of the steel sheet. Also, for the steel sheet for surface treatment, for example, for steel used for cans, it is necessary to strictly detect the defective portion and remove it. In order to deal with these problems, the actual situation is that visual inspection is currently being conducted.

[Object of the Invention]

The present invention provides a device capable of highly accurately detecting various shape defects occurring in a belt-like body during traveling. As another purpose, it is not only a signal indicating the presence or absence of a defective shape in the lengthwise direction of the strip, but it is also intended to make it possible to know at which position in the widthwise direction the defective shape exists and over which width. .

[Structure of Invention]

The present invention relates to a device for irradiating a test material with a laser beam to detect a defective shape, and a parallel scanning mechanism for irradiating a laser beam as a scanning beam in the width direction of the test material, and scanning reflected from the test material. Judges the scanning direction condenser that receives the specular reflection beam and condenses only in the width direction, the light receiving element row that receives the scanning regular reflection beam from the scanning direction condenser, and the light receiving element that receives the light from the light receiving element row The light receiving determination circuit, the circuit for detecting the position of the light receiving element receiving light, and the circuit for counting the number of light receiving elements receiving light are provided.

The principle of the present invention will be described with reference to FIG. 1 in Figure 1
Is a belt-like body which is a material to be inspected and runs in the X direction. A laser device 2 irradiates the rotating mirror 5 with the laser beam 3 through the convex lens 4. The laser beam 3 reflected by the rotating mirror 5 is reflected by the parabolic mirror 6 and becomes a scanning beam 7 that moves in parallel in the plate width direction, and irradiates the surface of the test material at an angle θ with respect to the test material 1. The scanning beam 7 reflected at the reflection point 8 of the material 1 to be inspected enters the light receiving device, is condensed in the width direction by the cylindrical lens 9, and is incident on the light receiving element array 10 densely arranged in the vertical direction. . here,
The reflection spot on the light receiving element array 10 changes as follows depending on the inclination of the reflection point 8 of the strip 1. That is, Fig. 2 (a)
When the scanning beam 7 is reflected by the normal portion 1-1 as shown in (1), the scanning reflection beam 7-1 is incident on the point A on the light receiving element array 10. When the scanning beam 7 is reflected by the defective shape portion 1-2, the scanning reflected beam 7-1 is incident on the point A on the light receiving element array 10. When the scanning beam 7 is reflected by the defective shape portion 1-2, the position where the scanning reflected beam 7-1 is incident on the light receiving element array 10 depends on the inclination direction of the defective shape portion 1-2, as shown in FIG. As shown in FIG. 2, it becomes a point B higher than point A, or as shown in FIG. 2 (c), it becomes point C lower than point A. The laser beam has a finite thickness, and when the inclination of the defective shape portion 1-2 is not constant at the scanning position of the test material 1, the scanning reflected beam 7-1 is the light receiving element array as shown in FIG. 2 (d). It may hit a wide range from B point to C point instead of hitting 1 point on 10.

When the shape of the strip 1 is flat, the light receiving signal received from the light receiving element array 10 is generated only from the light receiving elements near the point A. In other words, the scanning reflected beam 7-1 due to the defective shape has a large number of light receiving elements that receive it.
Since it causes the phenomenon that the light receiving element above a certain upper limit position or the light receiving element below a certain lower limit position is hit, or in extreme cases, it does not hit any light receiving element, these light receiving signals are used. The defect in shape can be detected by detecting that one or more of the above phenomena occur within the effective irradiation time. Since the shape defect is detected in this way, the present invention shows a shape defect over a relatively long range such as a middle stretch and a side stretch, or a spot such as a dent or a local defect such as a ditch defect. Even a defective shape can be accurately detected.

This principle is to detect the inclination of the surface of the reflection point 8 as described above. However, the direction of the reflected scanning beam 7 changes twice as much as the inclination of the reflection point 8, and further the light receiving element is used. The vertical movement distance on the row 10 is the reflection point 8 and the light receiving element row 10.
Since the distance L is proportional to the distance L, the inclination change can be very sensitively promoted if the distance L is sufficiently separated.

The conventional optical flaw detector is a method of detecting a change in intensity of reflected light, and does not detect the vertical position when the scanning reflected beam 7-1 enters the light receiving element array 10 as in the present invention. . Therefore, as described above, it was not possible to detect other than the extremely defective shape. The material to be inspected 1
The idea of detecting the vertical movement of the reflected light reflected by to obtain the inclination of the surface of the object is not particularly novel. For example, as disclosed in Japanese Patent Laid-Open No. 52-69853, a method of irradiating a point on a running strip with parallel rays and detecting the vertical position of the reflected parallel rays to detect the warp of the strip is known. Already exists. However, since this method can inspect only one point in the width direction of the strip, it is effective when the overall shape can be estimated from a portion such as a warp, but it is not possible to detect a shape defect that occurs locally. .

In short, the greatest feature of the present invention is that the excellent detection principle of obtaining the inclination change of the surface of the material to be inspected by monitoring the vertical fluctuation of the scanning reflected beam is applied to the traveling strip in two dimensions. It is possible to reliably detect not only the shape defects that spread over a wide range but also the locally generated shape defects.

Next, the present invention will be described in detail based on an embodiment with reference to the drawings.

〔Example〕

As shown in FIG. 1 and partly as already described, 1 is the material to be tested, for example a strip. Reference numeral 2 is a laser device, and its laser beam 3 is incident on a deflecting device, for example, a rotating mirror 5. The deflecting device is not limited to the rotating mirror 5, and any periodic vibrating mirror or the like may be used as long as it has a function of distributing the projected laser beam 3. 6 is a parallel scanner, which is, for example, a parabolic area,
The sample 1 is scanned as a scanning beam 7 that reflects the laser beam 3 incident from the rotating mirror 5 and moves in parallel in the width direction of the sample 1. Reference numeral 4 denotes a condenser provided between the laser device 2 and the rotating mirror 5, which is, for example, a convex lens, and serves to appropriately set the beam diameter and the divergence angle of the scanning beam 7 reflected by the parabolic mirror 6. I have The scanning beam 7 is applied to the material 1 to be inspected, and the irradiated part is called a reflection point 8. Reference numeral 9 denotes a scanning direction condensing device for the scanning reflected beam 7-1, which is, for example, a cylindrical lens,
It is provided in the width direction of the test material 1.

As described above, since the parallel scanning mechanism by the rotating mirror 5 and the parabolic mirror 6 and the focusing mechanism only by the cylindrical lens 9 in the width direction are incorporated, the scanning reflected beam 7-1.
The information in the vertical direction is not affected and the information on the defective shape is not lost. Further, if the scanning cycle is sufficiently short and the scanning pitch is sufficiently fine, the material to be tested 1
It is possible to thoroughly inspect the surface of the material to be inspected as the vehicle travels, and it is possible to reliably detect even minute shape defects.

A light receiving element array 10 is provided with a plurality of light receiving elements 11, and the scanning reflected beam 7-1 from the cylindrical lens 9 is incident on the light receiving element array. Although the number of the light receiving elements 11 is arbitrarily set, the cylindrical lens 9 collects the scanning reflected beams 7-1 at all points in the width direction in the light receiving element array 10, so that only one light receiving element array 10 is required.
In addition, the processing of signals becomes easy. The parabolic mirror 6 and the cylindrical lens 9 are required to have a size corresponding to the width of the material to be inspected for the entire width of the material to be inspected 1. However, if the width of the material to be inspected is large, It is also possible to provide n sets of the apparatus shown in FIG. 1 and inspect each 1 / n of the width. In order to make the beam spot of the scanning reflected beam 7-1 incident on the light receiving element array 10 as clear as possible, the angle θ formed between the scanning beam 7 and the material to be inspected 1 should be small, for example, 15 ° or less. Is preferred.

Next, the signal processing will be described with reference to FIG. Reference numeral 10 denotes the above-mentioned light receiving element array in which N light receiving element arrays are arranged. 1
Reference numeral 2 designates a total of N light receiving determination circuits provided for each light receiving element, and only those corresponding to the light receiving element on which the scanning reflected beam 7-1 is incident outputs an output. 13 is a scanning reflected beam 7
-1 is a light receiving position detection circuit for obtaining the maximum number h and the minimum number l of the incident light receiving elements, whereby the upper end position and the lower end position of the scanning reflected beam 7-1 are obtained. Reference numerals 14 and 15 denote determination circuits, respectively, when the upper end position h is a preset position h ₀ or more, the lower end position l is a preset position l ₀ or more, and the lower end position 1 is a preset position l _0. It is output at the following times and the defective shape is detected. Reference numeral 16 is a counting circuit, which is a light receiving determination circuit 1
The output n corresponding to the output number of 2 is output. Reference numerals 17 and 18 denote determination circuits, which output when n = 0 and n ≧ k (k is a preset value). This also detects a defective shape. Reference numeral 19 denotes a gate signal generating circuit, which is a scanning synchronization pulse separately sent from a light projecting head (not shown) and an edge detector (not shown) separately provided when the scanning beam 7 extends beyond the edge of the strip 1. The scanning beam 7 is based on the edge signal output from the strip 1
Generate a gate signal corresponding to the effective time of effectively irradiating.

Further, reference numerals 20, 21, 22, 23 denote the determination circuits 14, 1
AND circuit for passing only the output of 5, 16, 17, and 18 generated within the effective time, and 24 is the AND circuit
It is a selection circuit for selecting one or a plurality of outputs from the outputs of the circuits 20, 21, 22, and 23 as needed. The output from the selection circuit 24 is output only during the one-time laser scanning while the abnormality of the scanning reflected beam 7-1 as described above occurs. Therefore, the position and width of the defective shape in the width direction can be known by grasping at which timing this signal started to be generated and at which timing this signal was generated.

〔The invention's effect〕

Since the present invention is as described above, it is possible to accurately detect a shape defect over a relatively wide range occurring in a steel plate such as a magnetic steel plate or a steel plate for surface treatment, or a local fine shape defect with high accuracy. it can.

The shape flaw of the steel sheet has a metallic luster and has many specular reflection components at the time of light reflection, and as the flaw type, there are many sharp flaws, minute flaws, elongation, and gentle shape defects such as waves. It is effective for detecting such flaws. That is, in the present invention, many specular reflection components are used. In this regular reflection component, the angle of the reflected light changes by 2Δθ with respect to the angle change of Δθ on the reflecting surface, and by making the distance between the reflecting surface and the sensor large, the light movement distance on the sensor corresponding to the angle change Δθ. A sufficient Δs can be obtained, and highly accurate detection is possible. In addition, the light receiving position of the reflected light of a steep minute flaw is shifted or spread out compared with the case of being flat, and the shape defect that changes gently is displaced from the case of being flat.
Since the position detection and the number counting of the light receiving elements are performed in the present invention, it is possible to detect and identify such flaws and defective shapes.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are views for explaining an embodiment and principle of the present invention, and FIG. 3 is a view showing a signal processing block in the embodiment of the present invention. In the drawing, 3 is a laser beam, 1 is a material to be inspected, 5 and 6 are parallel scanning mechanisms, 7-1 is a reflected beam, 9 is a width direction focusing device, 10 is a light receiving element array, 12 is a light receiving determination circuit, 13 Is a light receiving position detection circuit, and 16 is a counting circuit.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G01N 21/88 8304-2J

Claims (1)

[Claims] 1. A device for detecting a shape defect by irradiating a test material with a laser beam, wherein a parallel scanning mechanism for irradiating a laser beam as a scanning beam in a width direction of the test material and a beam reflected from the test material. A scanning direction condensing device that receives a scanning regular reflection beam and condenses only in the width direction, a light receiving element array that receives the scanning regular reflection beam from the scanning direction condensing device, and a light receiving element that receives light by the light receiving element array. A shape defect detecting device, comprising: a light receiving determination circuit for determining whether a light receiving element is receiving light, a circuit for detecting the position of a light receiving element receiving light, and a circuit for counting the number of light receiving elements receiving light.