JPH04113260A - Method and apparatus for detecting surface defect - Google Patents

Abstract

PURPOSE:To enable detection of color shading due to stain or the like, in addition to a surface flaw of a substance to be inspected, by detecting a surface defect of the substance by discriminating a change in the value of an electric signal of each light-sensing element for a detected three-primary-color component light. CONSTITUTION:A red light source 3R and a blue light source 3B are provided respectively in the left and right opposite directions to a color detecting camera 2 disposed above a substance 1 to be inspected. A reflected light from the substance picked up by an image pickup lens 21 of the color detecting camera 2 is separated into its spectral components through filters 22R, 22G and 22B for R, G and B and applied as components lights of three primary colors of R, G and B to linear array photosensors 23R, 23G and 23B for R, G and B respectively. An inspection control device 5 conducts mutual comparison of color component data of red, green and blue signals with one another and executes discrimination as to whether the relevant surface position of the substance 1 to be inspected is a sound part or a defective part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for detecting surface defects such as scratches and uneven coloring on the surface of an object to be inspected, such as a steel plate.

[Prior Art] Surface defects on steel sheets include, for example, surface defects such as scratches and scratches, and color unevenness.

Conventional methods for detecting these surface defects include magnetic flaw detection, which applies a magnetic field to the object to be inspected and detects leakage magnetic flux from the defective part, or detects changes in the magnetic coupling coefficient between the detection coil and the object to be inspected. Various methods have been proposed, including optical detection methods that utilize the fact that when the surface of an object to be inspected is irradiated with a minute laser beam and scanned, the irradiation intensity changes greatly at the defective part.

[Problem to be solved by the invention] In the magnetic flaw detection method described above, it is difficult to detect areas where the cross-sectional shape locally changes, such as surface flaws, or areas where foreign matter of different material is mixed, such as inclusions. When a magnetic field is applied to any part of the magnetic field, leakage magnetic flux occurs. Further, changes in the magnetic coupling coefficient between the detection coil and the object to be inspected occur in any of the above portions.

In this way, the magnetic flaw detection method detects not only surface defects but also internal defects, and both are detected, so it is not suitable for conducting an inspection that focuses on surface defects only.

In addition, in this detection method, if the distance between the object to be inspected and the detection part changes, the sensitivity and magnetic coupling coefficient of the detector will change, so it is necessary to maintain the distance between the object to be inspected and the detector at a constant value. A mechanism is necessary. Therefore, magnetic flaw detection equipment has the problem of being large-scale and expensive.

In addition, optical detection methods and magnetic flaw detection methods using laser beams can detect defects in local shape changes such as surface flaws, but defects in which there is no change in shape or material such as color unevenness. There was a problem that it could not be detected.

Furthermore, an optical defect detection device using a laser beam is also expensive, and there is a problem in that it cannot be easily introduced from an economical point of view.

The present invention has been made to solve these problems, and is a surface defect detection method that can detect not only surface defects of an object to be inspected, but also surface color unevenness due to dirt, etc., and which can be configured at a low cost. and equipment.

[Means for Solving the Problems] A surface defect detection method according to claim 1 of the present invention irradiates a plurality of monochromatic lights from different directions onto the same position on the surface of an object to be inspected, and the irradiation position is detected by a camera. The reflected light photographed within the field of view is separated into three primary color components of red, green, and blue, and the intensity level of each separated color component light is detected as an electrical signal by a plurality of light receiving elements arranged in an array. ,
A surface defect on the object to be inspected is detected by determining changes in the value of the electric signal for each light receiving element of the detected three primary color component lights.

In the surface defect detection method according to claim 2 of the present invention, in the method according to claim 1, each of the plurality of monochromatic lights irradiated onto the same position of the object to be inspected is a linearly focused light beam, and The array light-receiving element that detects the intensity level of each of the three primary color component lights as an electrical signal is a linear array in which a plurality of light-receiving elements are linearly arranged for each color component.

The surface defect detection device according to claim 3 of the present invention includes a plurality of monochromatic light irradiating means for irradiating a plurality of monochromatic lights from different directions to the same position on the surface of an object to be inspected, and the irradiation position is within the field of view of a camera. a photographing means for photographing the reflected light; a spectroscopic means for dividing the photographed reflected light into three primary color components of red, green, and blue; an array light receiving sensor that receives light with a plurality of light receiving elements and detects the intensity level of the received light as an electrical signal for each light receiving element, and an electrical signal for each light receiving element of the three primary color components detected by the array light receiving sensor. and a defect detection means for detecting a surface defect of the object to be inspected by determining a change in the value of .

The surface defect detection device according to claim 4 of the present invention is the device according to claim 3, in which a plurality of monochromatic light irradiating means irradiates the same position of the object to be inspected, and each monochromatic light is irradiated at the irradiation position. a plurality of linear monochromatic light irradiating means for irradiating linearly focused light beams;
The array light receiving sensor detects the intensity level of each primary color component light as an electric signal, and includes a linear array light receiving sensor in which a plurality of light receiving elements are linearly arranged for each color component.

[Function] In the display defect detection method and apparatus according to claims 1 and 3 of the present invention, the plurality of monochromatic light irradiation means emit a plurality of monochromatic lights in different directions to the same position on the surface of the object to be inspected. and the photographing means photographs the reflected light with the irradiation position within the field of view of the camera. The spectroscopy means separates the photographed reflected light into three primary color components of red, green, and blue, and the array light receiving sensor receives each of the separated three primary color component lights with a plurality of light receiving elements arranged in an array. , the received light intensity level of each light receiving element is detected as an electrical signal. The defect detection means detects surface defects of the object to be inspected by determining changes in electrical signals for each light receiving element of the three primary color component lights detected by the array light receiving sensor.

In the display defect detection method and apparatus according to claim 2 and claim 4 of the present invention, the display defect detection method and apparatus according to claim 1 and claim 3 respectively
As a plurality of monochromatic light irradiating means for irradiating the same position of the object to be inspected in the method and apparatus according to the above, the linear monochromatic light irradiating means irradiates a luminous flux in which each monochromatic light is linearly focused at the irradiation position. . In addition, the spectroscopic 3
As an array light receiving sensor that detects the intensity level of each primary color component light as an electric signal, a linear array light receiving sensor performs signal detection using a plurality of light receiving signals arranged linearly for each color component.

"Example" Figure 1 is a block diagram of a surface defect detection device showing an example of the present invention, and Figures 2 (a) and (b) show the reflection of light at a surface sound part and a surface defect part, respectively. FIG.

In Figs. 1 and 2, 1 indicates an object to be inspected such as a steel plate;
2 is R (red), G (green), B (
This is a color detection camera that detects signals of three primary color components (blue).

FIG. 3 is a block diagram showing an embodiment of the color detection camera according to the present invention, and numeral 21 is a block diagram showing an embodiment of the color detection camera according to the present invention. Photographic lens that supplies reflected light to the next stage filter, 22
R, 22G, and 22B are R, G, and B filters that separate the incident light into the three primary colors of R, G, and H, respectively;
3R, 23G, and 23B each have a linear array light-receiving element that converts the optical signal into an electrical signal and outputs it when irradiated with light separated into three primary colors, and a linear array light-receiving element that converts the optical signal into an electrical signal and outputs it, and sequentially shifts the electrical signal that has been converted from optical to electrical. This is a linear array light-receiving sensor for R, G, and B, which has a built-in shift register that outputs signals. In addition, these three linear array light receiving sensors 23R,
Each of the linear array light receiving elements in 23G and 23B has, for example, 1024 light receiving elements arranged in a straight line,
Each element outputs an electrical signal with a voltage corresponding to the intensity of the irradiated light, and this voltage signal is sequentially taken out via a shift register.

24R, 24G, and 24B are amplifiers for R, G, and B, respectively, and each of the linear array light receiving sensors 23R
, 23G, and 23B are each amplified and output to the outside. A scanning control circuit 25 generates a shift clock signal to be supplied to each shift register in the R, G, and B linear array light receiving sensors 23R, 23G, and 23B based on an external scanning control signal. and output it. For example, the frequency is 60Hz (periodic 18.7m5
), 1024 shift clock signals are generated and output based on the scan control signals for each.

In Fig. 1, 3R is a red light source with a wavelength of 600 rv or more, 3B is a blue light source with a wavelength of 500 na+ or less, and 4R and 4B are cylindrical lenses (C
ylindrical Lens).

FIG. 4 is a diagram illustrating the shape of a cylindrical lens and its luminous flux. As shown in FIG. 4, a cylindrical lens (also referred to as a columnar lens) has a parallelogram in longitudinal cross section, so that no refraction occurs in the generatrix direction (vertical direction in the figure). However, since the cross section is surrounded by straight lines and circular arcs, refraction occurs in the direction perpendicular to the generatrix (left and right directions in the figure). Therefore, after refraction, the incident parallel light rays are focused at the focal line position into a linear light beam in the generatrix direction.

Reference numeral 5 in FIG. 1 is an inspection control device, which controls the entire surface defect detection device.

FIG. 5 is a block diagram showing an embodiment of the inspection control device according to the present invention, and 51R, 51G, and 51B are buffers for the R signal, G signal, and B signal inputted from the color detection camera 2, respectively. be. 52R152G, 52
B are the buffers 51R and 51G, respectively.

A/D converters for R, G, and B convert analog voltage signals inputted from 51B into digital data, and 53 is a scanning signal amplifier, which supplies the scanning control signal to the color detection camera 2. do. 54 is a controller mainly composed of a microprocessor, etc., and internally includes R,
It includes a G and B data storage section, a data comparison section, a discrimination section, a program storage section, a control section, and a scanning data output section. R
, G, B data storage section stores R, G, and
The B data is temporarily stored, and the read data is supplied to the data comparison section under the control of the control section. The data comparison section is R,
Comparison of data values between different color data in Il and Ij arrangement order of G and B linear array elements, comparison of data values between same color data in front and rear arrangement order, etc. are performed. The determining unit determines whether the part is a healthy part or a defective part based on the comparison result of the data comparing part. The program storage section contains a test program executed by the controller 54.

The control section reads the inspection program from the program storage section and controls the entire controller 54. The test data output section outputs the determination result of the discriminator as test data.

Reference numeral 55 denotes a control data output circuit that outputs control data from the inspection control device 5 to the outside (for example, a transport control device for an object to be inspected). A test data output circuit 56 outputs test data from the test control device 5 to an external device (for example, a printer, a CRT display device, a timer, etc.).

Further, LR and LB in FIG. 1 are linear light beams converged to their focal line positions by cylindrical lenses 4R and 4B, respectively.

The operation in FIG. 1 will be explained with reference to FIGS. 2 to 5.

In FIG. 1, a red light source 3R and a blue light source 3B are provided in opposite directions on the left and right with respect to a color detection camera 2 disposed above an object to be inspected 1. When the monochromatic lights from the red light source 3R and the blue light source 3B pass through the cylindrical lenses 4R and 4B, respectively, as explained in FIG. 4, the light beams LR and LB are linearly focused at their focal line positions. . The two light sources 3R, 3B and the cylindrical lens 4R are arranged so that the focal line positions of these two light beams are at the same position on the surface of the object 1 to be inspected.

4B is placed. In Fig. 1, the object to be inspected 1 is a steel plate, and two linear beams of monochromatic light are adjusted so that they are irradiated at the same linear position on the steel plate in a direction perpendicular to the direction in which the steel plate is conveyed. Ru.

Therefore, at the irradiation position on the surface of the object to be inspected 1, two linear light beams LR and LB are irradiated, and as a result, a light beam of composite light combined in the wavelength range of red light and blue light is irradiated. Become.

The color detection camera 2 detects the two linear light beams LR and L.
B is placed directly above the object to be inspected 1 which is irradiated with the synthesized light beams, and its built-in photographing lens 21 captures the reflected light (combined light) reflected from the surface of the object 1 by which the irradiated light beams are reflected. It has a sufficient viewing angle to allow photographing from any position. The reflected light photographed by the photographing lens 21 is for R.

The light is separated through the G and B filters 22R, 22G, and 22B, and is divided into R, G, and B primary color component lights.
Linear array light receiving sensor 23R123G for
, 23B is irradiated. What is important here is that the array direction of the linear array light receiving elements for R, G, 7 B (direction) must match completely. Next, the range (linear length) to which the linear light beams LR and LB are irradiated matches the field of view of the photographing lens 21.

As a result, each light receiving element in each linear array light receiving element arranged in a straight line is sufficiently irradiated with the reflected light from the irradiation range of the inspected object 1.

Once the mutual positions of the red light source 3R, the blue light source 3B, the cylindrical lenses 4R and 4B, the color detection camera 2, and the object to be inspected 1 are determined, the object to be inspected moves at a predetermined speed in its longitudinal direction (the right side in Fig. 1). direction). Then, the inspection control device 5 operates at a frequency of 60 Hz, for example, according to the inspection program stored in its program storage section.
At each time, a scanning control signal is sent to the scanning control circuit 25 in the color detection camera 2 via the scanning signal amplifier 53. The scan control circuit 25 supplies, for example, 1024 shift clock signals to each shift register in the R, G, and B linear array light receiving sensors 23R, 23G, and 23B within the period of 60t(z). Each linear array light receiving sensor 23R123G, 23B stores a voltage signal proportional to the light intensity of each of the three primary color components reflected from the surface of the object 1 to be inspected for each element (for example, the 1024 elements). , these 1024 stored red signals r, r, r..., green signals g. For corresponding R.

It is sent to the inspection control device 5 via the G and B amplifiers 24R, 24G, and 24B.

The inspection control device 5 sends the red signal, green signal, and blue signal to corresponding R, G, and B buffers 51R, 5, respectively.
1G, 51B and A/D converter 52R, 52G, 5
Quantized red data R via 2B.

R, R..., green data G, G1. G2... Blue data B, B, B2... are temporarily stored in the R, G, B data storage section in the controller 54.

The controller 54 reads out the color component data of the three primary colors stored in the R, G, B data storage section, compares the data with each other, and determines whether the corresponding surface position of the inspected object 1 is a healthy part or a defective part. Make a judgment.

Figure 2 (a) explains the reflection of light on a healthy part of the surface, and the same degree of scattered light is obtained from the linear red light flux LR and blue light flux LB, and the two reflection intensity distributions are almost the same. Become.

FIG. 2(b) explains the reflection of light at a defective part on the surface, and shows the angle and shape of the flaw on the object to be inspected 1 and the two light beams L.
Due to the relationship between the incident angles of R and LB, the reflected light from one of the monochromatic light beams is strongly reflected in the direction of the color detection camera 2. For example, when the reflection of the light beam LR is stronger, when comparing the data of the three primary colors in the same arrangement order, the value of the red data R is larger than the value of the blue data B.
nru. In addition, when comparing the order of the same color data before and after the arrangement order, the value of R of red data is the value of R
It becomes larger than n-1, and the value of B of the blue data is B. It becomes smaller than the value of -1.

Furthermore, if the defect is color unevenness such as dirt, the reflected light of the two light beams LR and LB may exhibit a different reflection intensity from that of a healthy area, or absorption may occur in one wavelength range. Therefore, based on the normal data in the memorized healthy part,
If data with a relatively larger value or data with a smaller value than the normal data value is obtained, it can be determined that it is a defective part.

In the surface defect detection device according to the embodiment shown in FIG. Defects can be detected with a resolution of 0.1 to 1.2 mm in the width direction.

Also, the moving speed for transporting the inspected object 1 in the direction of the arrow,
Each linear array light receiving sensor 23R, 23G.

If the signal scanning speed for reading out the three primary color signals photo-electrically converted from 23B is synchronized (for example, if the signal scanning repetition frequency is fiOHz, the moving distance of the inspected object 1 in this 1/6o second is (if it is kept constant), a two-dimensional image of the inspected object 1 can be obtained, and the two-dimensional dimensions of the defect can be measured.

The controller 54 outputs test data to the outside (for example, a printer, CRT display device, etc.) via the test data output circuit 56, and also outputs control data to the outside (for example, a transport control device for the object to be inspected) via the control data output circuit 55. It is possible to synchronize the scanning speed at which data is output and the signals of the three primary colors are read out and the moving speed of the conveyed object.

Furthermore, in this embodiment, an example is shown in which one set of surface defect detection devices is used for the inspected object 1, but by installing multiple sets of this device in the width direction of the inspected object 1, it is possible to detect a large width. (for example, about 1 to 2 m) of steel plates can be inspected at one time.

Further, according to this embodiment, an example is shown in which monochromatic light from a red light source and a blue light source is focused into a linear light beam through a cylindrical lens, and a surface defect of the object to be inspected is detected by the combined light of these light beams. However, the present invention is not limited to this.

For example, if the surface of the object to be inspected is placed at a position slightly closer than the focal line position of the cylindrical lens, the rectangular area of the surface of the object to be inspected will be irradiated with a plurality of monochromatic lights. The image is photographed by a normal color video camera, and signals for each color component are read out by performing a two-dimensional scan similar to the rask scan of a television from a two-dimensional array light receiving sensor for three primary colors arranged two-dimensionally within the video camera. , data comparison for each color component of a two-dimensional image can be performed at high speed. In this case, the transport speed of the object to be inspected can be increased to efficiently detect surface defects of the object to be inspected.

[Effect of the Invention] As described above, in the invention of claim 1 or claim 3, a plurality of monochromatic lights are irradiated from different directions to the same position on the surface of the object to be inspected, and the irradiation position is set in the field of view of the camera. The reflected light photographed as an interior is split into three primary color components of red, green, and blue, and the intensity level of each of the split color component lights is detected as an electrical signal by a plurality of light receiving elements arranged in an array, Since surface defects on the object to be inspected are detected by determining changes in the value of the electric signal for each light receiving element of the detected three primary color component lights, it is possible to detect surface defects on the object to be inspected as well as color unevenness due to dirt, etc. This method also has the effect of realizing a surface defect detection device that is cheaper than devices using conventional methods.

Further, in the invention of claim 2 or claim 4, the plurality of monochromatic lights irradiated to the same position of the object to be inspected are each focused into a linear light beam, and the intensity level of each of the separated three primary color component lights is As an array light receiving sensor that detects each color component as an electric signal, a linear array light receiving sensor in which a plurality of light receiving elements are linearly arranged for each color component is used for detection. This has the effect of providing a surface defect detection device that can be constructed more simply and at lower cost than the device based on the invention of the above invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a surface defect detection device showing an embodiment of the present invention, FIGS. 2(a) and (b) are diagrams illustrating light reflection at a surface healthy area and a surface defect area, and FIG. 3 4 is a block diagram showing an embodiment of the color detection camera according to the present invention.
The figure is a diagram explaining a cylindrical lens and its luminous flux,
FIG. 5 is a block diagram showing an embodiment of the inspection control device according to the present invention. In the figure, 1 is the object to be inspected, 2 is the color detection camera, and 3 is the object to be inspected.
R is a red light source, 3B is a blue light source, and 4R. 4B is a cylindrical lens, 5 is an inspection control device, 21
is a photographing lens, 22R, 22G, 22B are each 3
Filters for primary colors, 23R, 23G, 23B are linear array light receiving sensors for three primary colors, 24R, 24G,
24B is an amplifier for the three primary colors, 51R, 51G,
51B is a buffer for the three primary colors, 52R, 52G,
52B is an A/D converter for each of the three primary colors, 53 is a scanning signal amplifier, 54 is a controller, 55 is a control data output circuit, 56 is an inspection data output circuit, LR and LB are straight lines for red light and blue light, respectively. It is a luminous flux. Agent Patent Attorney Muneharu Sasaki Inspected object 4R4B Litztrical lens 3R Red light source LR, LB Linear light beam Reflection at a healthy surface (b) Reflection at a surface defect Figure 2

Claims (4)

[Claims] (1) A plurality of monochromatic lights are irradiated from different directions to the same position on the surface of the object to be inspected, and the reflected light is photographed with the irradiation position within the field of view of the camera and is separated into the three primary color components of red, green, and blue. , the intensity level of each of the separated color component lights is detected as an electrical signal by a plurality of light receiving elements arranged in an array, and the value of the electrical signal for each of the detected three primary color component lights is changed for each light receiving element. 1. A method for detecting surface defects, the method comprising detecting surface defects on an object to be inspected by determining the . (2) The plurality of monochromatic lights irradiated on the same position of the object to be inspected are each linearly focused light beams, and the array light reception detects the intensity level of each of the separated three primary color component lights as an electric signal. 2. The surface defect detection method according to claim 1, wherein the element is a linear array arrangement in which a plurality of light receiving elements are arranged in a straight line for each color component. (3) a plurality of monochromatic light irradiation means for irradiating a plurality of monochromatic lights from different directions onto the same position on the surface of the object to be inspected; and a photographing means for photographing the reflected light with the irradiation position within the field of view of a camera; , a spectroscopic means for separating the photographed reflected light into three primary color components of red, green, and blue; and a plurality of light receiving elements arranged in an array to receive each of the separated three primary color component lights, each receiving light. An array light receiving sensor that detects the received light intensity level of each element as an electrical signal, and a change in the value of the electrical signal for each light receiving element of the three primary color component lights detected by the array light receiving sensor to detect the object to be inspected. 1. A surface defect detection device comprising: defect detection means for detecting a surface defect. (4) The plurality of monochromatic light irradiation means that irradiate the same position on the object to be inspected are a plurality of linear monochromatic light irradiation means that irradiate a linearly focused beam of monochromatic light at the irradiation position. The array light receiving sensor that detects the intensity level of each of the separated three primary color component lights as an electric signal is a linear array light receiving sensor in which a plurality of light receiving elements are linearly arranged for each color component. 4. The surface defect detection device according to claim 3.