JP2001056297A - Surface inspection method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly and accurately detect and discriminate the defect contents of the surface of an object by a single inspecting device by simultaneously applying irradiation of yellow light in plane shape from a yellow light source and linear blue light from a blue light source, picking up the image of reflected light by a color camera with an RGB output function, and analyzing the image. SOLUTION: Light from a surface yellow light source A is applied to irradiate the surface of an inspected body E, with broadening surrounded by two dotted lines a1, a2. The mutual directions of the yellow light source A and a color camera C are so set that an incidence angle (t) of yellow light a2 toward a focus position (e) of the camera C coincides with an image pickup angle (v) of the camera C. The camera C also picks up the image of irregularly reflected yellow light c2. Light from a linear blue light source B is applied to irradiate the focus position (e), and the camera C picks up the image of only blue light irregularly reflected toward the camera C in the focus position (e) and traveling as shown by c1. RGB output from the camera C and further monochromatic luminance output from a monochromatic camera D if necessary are subjected to OR processing or the like to analyze the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously and automatically inspecting the surface of an object and an apparatus used for the method.

[0002]

2. Description of the Related Art Conventionally, the inspection of the surface of an object such as a metal plate has been mainly performed by visual observation by a human. However, many methods using an apparatus have been proposed. A method of detecting a surface defect by detecting a change in the luminance of light reflected on the surface of the inspection object using a color camera and a chromaticity change of light reflected on the surface of the inspection object using a color camera and a single illumination And inspecting the surface for defects using a laser beam, and measuring the intensity and angle of the reflected light to inspect the surface for defects.

First, in a human visual inspection, there is an individual difference, and it is practically impossible to perform an inspection at the same level over the entire surface of an inspection object even for the same person, resulting in unevenness in defect detection. On the other hand, with an inspection method that combines a monochrome camera and a single illumination, it is not possible to detect a defect unless the contrast is clear, and it is difficult to detect a low-contrast defect such as a thin film. The defect cannot be detected because there is almost no difference in contrast.

Inspection methods using a color camera and a single illumination can detect a color difference even if there is a low-contrast defect, for example, a yellow film on a white background. Similarly, in the case of a streak defect parallel to the traveling direction, a color difference is also hardly generated, and in many cases, it cannot be detected. Further, in the inspection method using laser light, since the laser light has a specific wavelength, the detection rate for the color is low, and the method is expensive.

[0005] Further, as an improved method of the inspection method combining the above color camera and a single illumination, a three color light source of three primary colors of red, green and blue for irradiating the object surface and one color camera having an RGB output function are provided. There is also a method of detecting the surface state by analyzing the RGB output using the method described in Japanese Patent Application Laid-Open No. H5-1880.
06). However, this method also has a difficult positional relationship between each light source, object, and camera to obtain uniform illumination in the camera's imaging range, and the same defect reflects differently depending on the position of the object. , You have to add complicated processing.

There are various types of defects on the surface of an object which actually occur. However, these conventional methods have advantages and disadvantages. Therefore, only a certain type of defect is targeted, or a plurality of inspection methods are used in combination. is the current situation. Further, with a single inspection method, different types of defects are often regarded as similar changes, and it has been difficult to accurately determine the type of defect.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for efficiently detecting and discriminating a defect on the surface of an object and its type, which have been difficult to detect at the same time.

[0008]

According to the present invention, there is provided a method of performing image processing on RGB output using one color camera.
The above-mentioned problem has been solved by using two types of blue light, one of the primary colors, and yellow light, which is a combination of the other two primary colors, and irradiating the former linearly and the latter planarly.

That is, the present invention simultaneously irradiates a yellow light from the yellow light source in a planar shape and a blue light from the blue light source in a linear shape to the inspection target portion on the surface of the object to be inspected, and reflects the reflected light to one unit. RGB
This is a surface inspection method characterized in that images are taken with a color camera having an output function, and defects on the surface of the object to be inspected are detected by image analysis of RGB output. A yellow light source for irradiating, a blue light source for linearly irradiating blue light to an inspection target portion on a surface of an inspection object,
One color camera and RGB having RGB output function
A surface inspection device having an output image analysis device.

The present invention also includes a mode in which the reflected light obtained by the above-described method is imaged by a monochrome camera, and image processing of black-and-white luminance is also performed, thereby improving the inspection efficiency.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to specific examples shown in FIGS. 1 and 2. In the specific example described here, the above-mentioned reflected light is imaged by a monochrome camera.
In this embodiment, black-and-white luminance image processing is also performed. FIG.
FIG. 2 is a plan view showing a mutual positional relationship between a yellow light source, a blue light source, an object to be inspected, a color camera, and a monochrome camera, and FIG. It is the figure shown graphically.

First, a description will be given with reference to FIG. The test object E moves in the direction indicated by the arrow f, and as a result, the color camera C
The monochrome camera D scans the surface of the inspection object. In this example, the yellow light source A and the blue light source B are oriented in a direction opposite to the arrow f at a fixed angle with respect to the surface of the test object, and the color camera C and the monochrome camera D are aligned with the arrow f. In the same direction, they face the surface of the test object at constant and different angles. However, the mutual position of the light source and the camera may be opposite to that in this example, that is, the light source may be in the same direction as the arrow f and the camera may be in the opposite direction to the arrow f. Also, in FIG. 1, the two light sources are drawn as rectangles that can cover the lateral width of the test object. However, the width that the camera can cover is limited, and in the case of FIG. Needless to say, it is necessary to install a plurality of pairs of color cameras and monochrome cameras according to the width.

Next, a description will be given with reference to FIG. The yellow light source A is a planar light source, and is indicated by two dotted lines on the surface of the test object E in the figure.
The light is radiated in a range surrounded by a1 and a3, and the mutual orientation of the yellow light source A and the color camera is specularly reflected with respect to the surface of the test object, that is, the yellow light traveling toward the focal position e of the camera.
It is assumed that the incident angle t of a2 coincides with the imaging angle v of the color camera. Accordingly, the color camera captures yellow light specularly reflected at the focal position e and proceeds like c1. However, since the yellow light is illuminated in a planar shape, not only the specularly reflected yellow light but also other than the focal position e is captured. It also captures yellow light that has been scattered and reflected in the direction of the color camera at the position, for example, advancing like c2.

The blue light source B is a linear light source and has a focal position e.
However, the mutual orientation of the blue light source B and the color camera does not have a relationship of regular reflection with respect to the surface of the inspection object. Therefore, the color camera scatters and reflects in the direction of the color camera at the focal position e and c1. As a result, only the blue light that has advanced as described above is imaged. In the figure, the yellow light is indicated by a line for convenience,
It goes without saying that the light has a certain width.

On the other hand, the focal position of the monochrome camera D is the same as that of the color camera, but the mutual directions of the two light sources do not have a regular reflection relation to the surface of the object to be inspected. Therefore, in the monochrome camera, at the focal position e, the blue light and the yellow light scattered and reflected in the direction of the monochrome camera at the focal position e, and scattered and reflected in the direction of the monochrome camera at any of the irradiation portions of the yellow light and the yellow light, as in d1. Thus, the advanced yellow light is imaged.

The surface inspection apparatus of the present invention can output RGB output from a color camera and, if necessary, black and white luminance output from a monochrome camera in addition to these light sources and cameras.
Although the apparatus is configured by combining apparatuses for performing image processing by performing R operation processing or the like, there is no particular limitation on such an image analysis apparatus, and any apparatus that is generally used for this kind of purpose can be used.

Next, a description will be given with reference to FIG. 3 which schematically shows the types of defects and the output waveform of the camera. The upper part of FIG. 3 shows an example in which examples of four defects g, h, i, and j having different characteristics on the surface of the inspection object are vertically arranged in the traveling direction of the inspection object. The defect g is a defect having the same color as the object to be inspected but without surface gloss, the defect h is a defect having the same surface gloss as the object to be inspected but having a black color, and the defect i is a defect having a progression of the object to be inspected. A groove-like streak defect parallel to the direction, and defect j is a light color unevenness defect.

The lower part of FIG. 3 shows output waveforms R ′, G ′, and B ′ when the above four types of defects are imaged by a color camera.
G ′, B ′ and an output waveform W ′ of black-and-white luminance W when an image is captured by a monochrome camera are shown. The output waveforms R ′ and G ′ of R and G of yellow light captured by a color camera after specular reflection and scatter reflection change depending on the color, shape and size of the defect. Although the defect g and the defect h have the same shape and size, there is a difference in the color tone and the like as described above.
The output waveforms R 'and G' are different as shown in FIG. This is because the output waveform R ′ depends on the reflectance of the surface of the object, is greatly affected by the difference in gloss, and is not significantly affected by the difference in luminance, whereas the output waveform G ′ is irregularly reflected on the surface of the object. This is because the luminance difference greatly depends on the brightness and the absorption, but the gloss difference is not so much affected. Also, line-shaped defects such as R and G co-defects i are hardly affected. R,
The reflectance of G is stable, and output waveforms R 'and G' corresponding to the color, shape, and size of the defect can be obtained. , Shape and size.

On the other hand, a blue light source has a short wavelength range,
The output waveform B ′ of B scattered and reflected therefrom changes greatly even with a minute flaw. Defect i is a yellow light source,
Both R ′ and G ′ do not change, but change strongly in the output waveform B ′. In other words, the output waveform B ′ has a specular positional relationship between the light source and the color camera for a defect whose surface on the surface of the object is oblique, such as the defect i, and reacts strongly. The image processing of the output waveform of the brightness by the monochrome camera targets color unevenness with a small contrast difference, gentle unevenness, and the like, and specializes in detection of a defect such as a defect j which has no change in hue.

Thus, yellow light has a wavelength of 500-70.
There is no relatively large peak at 0 nm in the spectral resolution (relative sensitivity), and the defect that is stable and can be imaged at a long wavelength can be imaged. Most defects other than minute scratches, for example, dents,
Detects scratches, rust, oil stains, resin powder, wrinkles. on the other hand,
Blue light has a wavelength of 400 to 500 nm and a spectral density (relative sensitivity) having a peak different from that of a yellow wavelength. A defect which is separated at a short wavelength can be imaged, and a minute flaw defect is detected. Defects with a small rate of change in hue, such as gentle unevenness and light color unevenness on the metal surface, cannot be detected by RGB output image processing, but can be detected by monochrome image processing from monochrome camera imaging. Can be.

As described above, the present invention makes it possible to classify all defects in one inspection and is effective in inspecting the surface of any object. It is valid. Insulating board with copper foil on one or both sides obtained by laminating copper foil on a resin impregnated sheet or a resin sheet containing no base material such as glass cloth or paper, and applying pressure and heat treatment Is a copper-clad laminate, which is mainly used for printed wiring boards, but the surface condition is not strictly flat, and when using a base material, the texture of paper or glass cloth is about several μm on the surface. Making irregularities. That is, the pitch of the cloth, the thickness and the thickness of the substrate,
Also, depending on the method of producing copper foil (electrolytic copper foil, rolled copper foil), the direction in the production process, surface treatment (rust prevention, thermal discoloration prevention), and thickness, there are various differences in the surface condition of the copper clad laminate. However, these differences are reflected in the specific output of specularly or scattered light from the light source to the camera. Such differences in surface state are not all defects, but can be effectively used as information other than defects.

[0022]

According to the present invention, the surface inspection of the inspection contents which could not be realized without using a plurality of inspection apparatuses in the past,
It can be realized with a single inspection device, and the content of the defect can be accurately known. The cause of the defect can be quickly analyzed and countermeasures can be taken, leading to the stabilization of the quality, the improvement of the productivity, and the cost reduction. Is big.

[Brief description of the drawings]

FIG. 1 is a plan view showing a mutual positional relationship among a yellow light source, a blue light source, a test object, a color camera, and a monochrome camera.

FIG. 2 is a side view showing light irradiation and an imaging angle of a camera with an object to be inspected.

FIG. 3 is a diagram schematically showing types of defects and output waveforms of a camera.

[Explanation of symbols]

A: Yellow planar light source a1: Yellow light going to the top a2: Yellow light going to the focal position of the camera a3: Yellow light going to the bottom B: Blue linear light source b1: Blue light going to the focal position of the camera C: Color camera c1: Specular reflection light at the focal position of the yellow light camera captured by the color camera and scattered reflected light at the focal position of the blue light camera c2: Focus position of the yellow light camera captured by the color camera D: monochrome camera d1: scattered reflected light at the focal position of the yellow light captured by the monochrome camera and scattered reflected light at the focal position of the blue light camera d2: yellow captured by the monochrome camera E: Inspection object e: Camera focal position t: Incident angle of yellow light a2 v: Color camera imaging angle f: Traveling direction of inspection object g: Defect h : Defect i : Defect j: Defect k: Scan direction of the color camera and the monochrome camera l: Waveform in which defect g is detected m: Waveform in which defect h is detected n: Waveform in which defect i is detected o: Waveform in which defect j is detected R ': Red image signal waveform from specular reflection light and scattered reflection light of yellow light G ': Green image signal waveform from specular reflection light of yellow light and scattered reflection light B': Blue from scattered reflection light of blue light Image signal waveform W ′: Image signal waveform of brightness from scattered reflected light of yellow light and scattered reflected light of blue light

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiichi Kataishi 9-41 Sugiyama, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Inside Electrotechno Co., Ltd. −41 Inside Electrotechno Co., Ltd. (72) Inventor Satoshi Suzuki 9-41, Sugiyama, Nishigomura, Nishishirakawa-gun, Fukushima Prefecture F-term (reference) 2G051 AA37 AA90 AB02 AB07 BA08 BA20 CA03 CA04 CA07 CB01 CB05 DA01 DA06 EA16 EA17

Claims (8)

[Claims] 1. An RGB output function for simultaneously irradiating a yellow light from a yellow light source in a planar shape and a blue light from a blue light source in a linear shape to an inspection target portion on the surface of an object to be inspected and reflecting light from one unit. A surface inspection method characterized in that an image is picked up by a color camera and a defect on the surface of the inspection object is detected by image analysis of RGB output. 2. An RGB output function for simultaneously irradiating a yellow light from a yellow light source in a planar shape and a blue light from a blue light source in a linear shape to an inspection target portion on the surface of an object to be inspected and reflecting light from one unit. RGB images from a color camera and a monochrome camera having a monochrome brightness output function.
A surface inspection method characterized by detecting defects on the surface of an object to be inspected by image analysis of an output and image analysis of a monochrome luminance output from a monochrome camera. 3. The apparatus according to claim 1, wherein the yellow light source and the color camera have a positional relationship of specular reflection with respect to the surface of the inspection object, and the blue light source and the color camera have a positional relationship of scattering reflection with respect to the surface of the inspection object. 1. The surface inspection method according to 1. 4. A yellow light source and a color camera have a positional relationship of specular reflection with respect to the surface of the test object, a blue light source and a color camera have a positional relationship of scattered reflection with respect to the surface of the test object. 3. The surface inspection method according to claim 2, wherein the light source, the blue light source, and the monochrome camera have a positional relationship of scattering and reflection with respect to the surface of the inspection object. 5. The surface inspection method according to claim 1, wherein the object to be inspected is a copper-clad laminate. 6. A yellow light source for irradiating the inspection target portion on the surface of the inspection object with yellow light in a planar manner, a blue light source for irradiating blue inspection light linearly on the inspection target portion of the inspection object surface, RGB
A surface inspection device comprising a color camera having an output function and an image analysis device for RGB output. 7. A yellow light source for irradiating the inspection target portion on the surface of the inspection object with yellow light in a plane, a blue light source for irradiating blue light linearly on the inspection target portion of the inspection object surface, RGB
A surface inspection apparatus comprising: a color camera having an output function, a monochrome camera having a black-and-white luminance output function, and an image analyzer for RGB output and black-and-white luminance output. 8. A yellow light source and a color camera have a positional relationship of specular reflection with respect to the object to be inspected, a blue light source and a color camera have a positional relationship of scattered reflection with respect to the object to be inspected. 8. The surface inspection apparatus according to claim 6, wherein the blue light source and the monochrome camera have a positional relationship of scattering and reflection with respect to the inspection object.