JPH0412256A - Mirror inspecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to a mirror surface inspection device.

More specifically, the present invention relates to a mirror inspection device for inspecting mirror-finished flat plate materials used for cosmetics, building materials, and the like.

B. Conventional technology Conventionally, as a device for inspecting defects on the surface of mirror-finished flat plate materials used for cosmetics, construction materials, etc., a laser beam is incident and the amount of reflected beam from the surface is measured. The method is the same (method of injecting a laser beam and measuring the deviation of the reflection angle of the reflected beam from the surface from the reference angle, or the method of photographing the surface condition with a television camera and inputting the image, and applying image processing to this) There are known ways to do it.

C1 Problems to be Solved by the Invention However, the above-mentioned device had the following problems.

In other words, defects may not be detected even if they exist, or
Over-detection of defects that should have been acceptable occurred frequently, and the recognition or judgment of defects by the inspector's visual inspection did not match the inspection results by the above equipment, or a clear response could not be determined. .

Originally, mirror-finished flat plate materials were used for cosmetics, building materials, etc.
is the main performance, and surface defects must be judged from the viewpoint of whether or not they impair this performance.

That is, defects over a wide area of the flat plate material, such as large, gently sloping undulations, directional irregularities in the molding body, or long linear irregularities, are the main defects.

However, conventional devices are mainly suitable for detecting minute and local defects such as small bits, scratches, scratches, dirt, dust, etc., but are not necessarily suitable for detecting the major defects mentioned above. Ta.

Furthermore, although conventional devices are suitable for detecting large changes in minute areas, in order to detect defects over a wide range, it is necessary to scan laser beams and use multiple detection heads. This makes high-speed processing difficult and increases equipment costs.

On the other hand, when the inspection area is divided, the correspondence between the inspection results and the defects covering a wide area of the object to be inspected is not clear.

The present invention has been made in view of these conventional problems, and enables the measurement of defects over a wide range quickly and easily.
It is an object of the present invention to provide a mirror surface inspection device for a mirror-finished flat plate material that can reduce the burden on an inspector and perform the inspection with high accuracy.

90 Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides (1) a pattern, a photographing means for photographing a reflected image of the pattern on the surface of a test object, and a photographing means for photographing a reflected image of the pattern on the surface of a test object; A specular inspection apparatus comprising a detection means for receiving and processing an output of a reflected image to detect defects on the surface of the object to be inspected,
A mirror surface inspection device was constructed in which the pattern is a pattern in which elementary figures are regularly repeated. Furthermore, (2) a specular inspection device is constructed in which the pattern is a pattern in which circles are repeated at equal intervals in two orthogonal directions. Furthermore, (3) a specular inspection apparatus is provided, comprising a determining means for determining whether or not the defect detected by the detecting means exceeds a preset standard.

The E3 action pattern has a large area. It is a regular repeating pattern such as a pattern in which circles are repeated at equal intervals in two orthogonal directions.

A camera captures a wide range of reflected images on the surface of the object to be inspected. Photographing lenses with different focal lengths can be selected depending on conditions such as the width of the object to be examined, and it is possible to photograph the entire width at once.

The defect detection display is easily visible on the CRT and is displayed on a plurality of LEDs.

Pass/fail judgment is automatically made based on the detection results.

F. Example Embodiments according to the present invention will be described with reference to FIGS. 1 to 9.

Figure 1 is a side view showing the concept of a specular inspection device according to an embodiment of the present invention, Figure 2 is a diagram showing the relationship between a pattern and a camera, and Figure 3 is a diagram showing the relationship between defects and image blur. , FIG. 4 shows the pattern, FIG. 5 shows the light intensity distribution, and FIGS. 6 to 9 show the defects.

The object to be inspected (1) is an object to be inspected by this mirror inspection apparatus, and is a flat plate whose surface is mirror-finished. It includes glass plates and synthetic resin plates whose surfaces are coated with silver, aluminum vapor deposition, or other coatings. When the object to be inspected (1) is long in the form of a strip, it moves relative to the camera.

Pattern (2) is a pattern suitable for defect detection drawn on a flat plate. The color is a black pattern drawn on a white background, or a white pattern drawn on a black background, depending on the spectral characteristics of the light-receiving material used for the photographing screen of the camera (3), and the contrast is good. You can choose the color scheme. The planar plate material is made of a transparent or translucent material, and is used by illuminating from the opposite side of the object to be examined (1), but it can also be illuminated from the side of the object to be examined (1).

A geometric repeating pattern is appropriate for the figure.

A spotted pattern with repeating circles, similar to Go stones arranged on a base.
A blind pattern in which straight lines are arranged at equal intervals, a lattice pattern in which straight lines are arranged at equal intervals, etc. are used.

If the pattern (2) is transparent or translucent, the illumination device (not shown) illuminates it from the opposite side of the object to be examined (1), and if it is opaque, it illuminates it from the side of the object to be examined (1). Test object (1
), diffused illumination is suitable for uniformly illuminating the area with a sufficient but not excessive amount of light.

The camera (3) optically receives an image of the two-dimensional pattern (2) and outputs an electrical signal, and is suitably an industrial television camera (ITV). In addition to CCD cameras, ↑ image tube cameras can also be used. Multiple cameras may be used if necessary. A conductor is connected from the camera (3) to the detection device (4).

Although various focal lengths can be selected for the photographic lens (3a), a lens with a long focal length was used.

Fit the entire width of the test object (1) on the screen, and
In order to reduce the effects of changes in the thickness of the lens and vertical shake due to movement, it is better to choose a long focal length and deepen the depth of focus.

The detection device (4) is a known device that detects defects based on electrical signals transmitted from the camera (3).
A photographing screen is displayed on the screen (not shown), the received light intensity is displayed on a display section (not shown) equipped with an LED, and the detection result is transmitted to the judgment device (5). Image processing is carried out by a known method, but for example, if the pattern is a black circle on a white background, the defective part will be blurred to gray, and a gray filter can be used to binarize it and detect and display it as a white defect signal on a black background.

The determination device (5) is a known device that determines whether the test is passed or failed based on the results detected and transmitted by the detection device (4) in accordance with preset criteria. The detection device (4) performs expansion/contraction processing on the transmitted defect signal to remove noise, then measures the position, area, length, etc., and determines whether it is acceptable or not based on standards.

Next, how the camera (3) photographs a reflected image of the pattern (2) on the surface of the test object (1) will be explained with reference to FIG.

Figure 2 shows pattern (2), test object (1) and camera (
3) is a side view showing the arrangement and optical path.

The pattern (2) and the camera (3) are placed on the same side with respect to the object (1). Points on pattern (2) (
When the test object (1) is a perfect mirror surface, the light emitted from the test object (1) is reflected at the surface, and a virtual image (7) is formed at the point (2b) at a symmetrical position with respect to the test object (1) surface. The camera (3) is placed so as to directly face the virtual image (7), and the photographic lens (3a)
), light is incident and an image is formed.

At this time, the light emitted from point (2b)
Reflected light between the point (IC) and the point (1d) on the surface of the lens enters the photographing lens (3a) and forms an image.

In order to fit the width direction of the test object (1) within the angle of view of the photographing lens (3a) of one camera (3), the pattern (
The width of 2) needs to be larger than the width of the object to be examined (1).

Next, when there is a defect on the surface of the object to be inspected (1), the distortion of the pattern (2) on the photographing screen (8) will be explained with reference to FIG.

FIG. 3 is a side view showing the optical path when there is a defect on the surface of the object to be inspected (1). In general, a portion with a reflection defect can be understood as a microscopic surface that is inclined with respect to a mirror surface. The cosmetic reflection of flat plate materials for cosmetics and building materials is large, gently sloping undulations, which are mainly understood as reflections caused by continuous microsurfaces with small but gradually changing angles of inclination over a wide range. be able to. In other words, for large, gently sloping undulations, the direction of reflected light from adjacent, continuous microscopic surfaces gradually changes in each direction, including the plane of incidence and the direction perpendicular to the plane of incidence.

In FIG. 3, a point (1c) on the surface of the test object (1),
When there is a defect in (1b) or (1d), it means that the defective part is inclined with respect to the mirror surface. pattern(
2) The light emitted from the point (2b) above is the object to be tested (1)
The reflected light from each point (IC), (1b), and (1d) enters from the photographing lens (3a). Each point (IC), (1b),
(1d) has a defect and reflects in a different direction than would be reflected on a perfect surface. For example, point (IC)
, (1b), (1d) The light reflected at point (8C)
, (8b), and (8d), and the image is not focused on one point (8a) on the photographing screen (8). Point (2b) is the shooting screen (
8) It is not imaged on the focal plane when it is a perfect surface on the top,
This results in what is called "out of focus."

Next, pattern (2) will be explained.

Geometric repeating patterns such as those illustrated in FIGS. 4(a), (b) and (c) are suitable. In particular, the spot pattern shown in (a), which repeats circles on the base like a Go stone, has high detection sensitivity when visually detected, making it easy to make accurate judgments, and easy to process information in the detection device. It is.

The circles are repeated at equal intervals in two orthogonal directions. In other words, a circle with the same diameter is placed at each intersection of folds in which a plurality of parallel lines lined up at equal intervals are orthogonal to each other, and no lines are drawn, creating a polka dot-like figure. The appropriate diameter of the circle is about 0.5 to 0.7 times the distance between the parallel lines.

Next, the intensity distribution of light on the photographing screen (8) will be explained with reference to FIG.

FIGS. 5(a), 5(b), and 5(c) are diagrams showing the light intensity distribution on the photographing screen (8) of a plurality of circles arranged at equal intervals on the pattern (2).

The horizontal axis shows the position of the circle, and the vertical axis shows the intensity.

(a) for a surface without defects, (b) for a surface with defects and (C) for a surface with severe defects.

In (a), the light intensity is distributed only in a range corresponding to the diameter of the circle. In (b), the main light intensity is distributed in a range corresponding to the diameter of the circle, but the light intensity is also distributed in other ranges. In (C), the light intensity in the range corresponding to the diameter of the circle is significantly reduced, and the light intensity in other ranges is widely distributed.

FIGS. 5(d), (e), and (f) are plan views showing the intensity distribution of light. They correspond to (a), (b) and (C), respectively.

In (d), the intensity of light is distributed on the photographic screen (8) in a circle corresponding to the diameter of the circle on the dowel pattern (2). In (e), the diameter of the circle is shorter in one direction and longer in the direction perpendicular to it, but it is not yet in clear contact with the adjacent circle. In (f), the diameter of the circle is shorter in one direction and longer in the direction perpendicular to it, and the circle is connected to the adjacent circle so that there are no clear boundaries.

Figures 6 to 9 regarding the test results obtained in this example.
This will be explained using figures. The one shown in Fig. 6(a) is a 30 cmM30 specimen with no defects on the surface of the test material (1).
It is a plate material with a mirror finish of cm. In the image on the photographic screen (8), as shown in FIG. 6(b), a plurality of circles of pattern (2) appear exactly as a plurality of circles. Nothing appears on the screen on which image processing has been performed in the detection device (4). Therefore, it is detected that no defects exist, and a pass judgment is made.

The object shown in Figure 7(a) is the test object (1) with the same dimensions.
The so-called "waviness" defect (work 1) shown on the surface of
)have. The image on the shooting screen (8) is shown in Figure 7(b)
As shown in the figure, it corresponds to defect (11)! In (12), the multiple circles of pattern (2) do not appear accurately as multiple circles. A defect image that is almost reversed in black and white is detected on the screen where image processing is performed in the detection device (4). Therefore, it is detected that a defect exists and is a defect called a gentle "undulation." Next, a pass/fail determination is made by comparing with preset criteria, and a fail determination is made.

The one shown in FIG. 8 has a defect (21) called a so-called "waviness" shown on the surface of a test object (1) of the same size. This is a case where the direction of the defect (21) is different from the direction of the pattern (2) shown in FIG. 7(a), and the defect is sharp. As shown in FIG. 8(b), the image on the photographing screen (8) shows that the circles of pattern (2) do not appear exactly as multiple circles at the position (22) corresponding to the defect (21). . A defect image that is almost reversed in black and white is detected on the screen where image processing is performed in the detection device (4). Therefore, it is detected that there is a defect and that it is a sharp "undulation" similar to a "wrinkle". Next, a pass/fail determination is made by comparing with preset criteria, and a fail determination is made. In this way, defects have directionality, and can be sufficiently detected in any direction.

The one shown in FIG. 9 has a minute defect (31) on the surface of a test object (1) of the same size.

The image on the photographic screen (8) shows the pattern (2) at the position (32) corresponding to the defect (31), as shown in FIG. 9(b).
The multiple circles in a) do not exactly appear as multiple circles. However, it is limited to a narrow area. A minute defect image is detected on the screen subjected to image processing in the detection device (4). Therefore, the presence of a defect is detected. However, next, a pass/fail determination is made by comparing with preset criteria, and a pass/fail determination is made. This material to be inspected (1) was determined to be acceptable based on the visual inspection results of the inspector.

In this way, according to this example, the surface of a wide flat plate material for decorative and building materials with a width of 30 crri could be inspected without detecting local defects, and pass/fail was automatically determined.

G1 Effect of the Invention According to the present invention, a regular repeating pattern such as a pattern having a wide area and repeating circles at equal intervals in two orthogonal directions enables the production of wide flat plate materials for decorative and building materials. Surface defects are easily visible on a CRT, and multiple L
Since it is detected and displayed in the ED, large images covering a wide area,
Defects over a wide range of flat plate materials, such as gently sloping undulations, directional irregularities in molding, or long linear irregularities, can be detected with clear responses without differing from the visual inspection results of inspectors.・I was able to make a judgment.

Since the camera captures a wide range of images of the surface of the object to be inspected, it was possible to inspect the surfaces of wide flat plates for cosmetics and building materials without dividing the inspection area.

In addition, since the depth of focus can be increased by selecting a photographic lens, the effects of changes in the thickness of the object to be examined, vertical shake due to movement, etc. are small.

The device could be configured and installed using inexpensive equipment such as patterns and cameras.

In addition, pass/fail judgments are automatically made based on the detection results, so
Automatic judgment was performed, reducing the burden on inspectors.

[Brief explanation of drawings]

Fig. 1 is a side view showing the concept of a specular inspection device according to an embodiment of the present invention, Fig. 2 is a view showing the relationship between a pattern and a camera, and Fig. 3 is a view showing the relationship between defects and image blur. , FIG. 4 is a diagram showing a pattern, FIG. 5 is a diagram showing a light intensity distribution, and FIGS. 6 to 9 are diagrams showing defects. [Explanation of symbols of main parts] 1...Object to be tested 2...Pattern 3...Camera 4...Detection device 5...Judgment device (CI) Figure (b) Figure

Claims (3)

[Claims] (1) A pattern, a photographing means for photographing a reflected image of the pattern on the surface of the object to be inspected, and receiving and processing the output of the reflected image photographed by the photographing means to detect defects on the surface of the object to be inspected. 1. A mirror surface inspection apparatus comprising: a detection means for detecting a pattern, wherein the pattern is a pattern in which elementary figures are regularly repeated. (2) The specular inspection apparatus according to claim 1, wherein the pattern is a pattern in which circles are repeated at equal intervals in two orthogonal directions. (3) The specular inspection apparatus according to any one of claims (1) and (2), further comprising determining means for determining whether or not the size of the defect detected by the detecting means exceeds a preset standard.