JP3870494B2 - Surface defect inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface defect inspection apparatus, and more particularly to a surface defect inspection apparatus capable of optically and automatically performing an operation of inspecting the state of painting on a body surface in an automobile production process.
[0002]
[Prior art]
Conventionally, inspecting the surface of an automobile body or the like, a human has visually inspected the surface for defects after the painting process. However, various methods have been proposed as a surface defect inspection apparatus for automatically and optically inspecting the coating surface inspection work. For example, there is one disclosed in JP-A-8-086634 (surface defect inspection apparatus). The surface defect inspection apparatus of the conventional example uses a fluorescent lamp, laser, LED, etc. arranged in a straight line as a light source, creates slit light or slit pattern light, and irradiates the surface of the body after painting, It is a device that inspects surface defects by detecting a difference in brightness or a change in brightness that occurs when the surface is uneven.
[0003]
[Problems to be solved by the invention]
However, the conventional example has the following disadvantages. That is, almost all surfaces of the automobile body are uneven curved surfaces. To solve the problem of how to detect defects on curved surfaces, the above conventional example proposes a method for dealing with curved surface defects by performing predetermined image processing in advance when recognizing defects from captured images. Has been. However, in the method of irradiating the inspection light with a light source arranged on a straight line (or on a flat surface), when the image is captured by illuminating the curved surface, the reflected light of uniform light intensity is applied to each part due to the inclination of the curved surface. The inconvenience that it cannot be obtained has arisen.
[0004]
In addition, there is a disadvantage that the illumination pattern of the inspection light on the inspection object is distorted. For this reason, it is difficult to recognize with high accuracy. Furthermore, since the surface defect inspection apparatus according to the conventional example has a plurality of light sources, inspection light is irradiated from a plurality of light sources at the same time, and ambient light other than light on the optical axis hits the defect. Since this is received by the light receiving means, there is a problem that it is impossible to detect with high accuracy.
[0005]
OBJECT OF THE INVENTION
It is an object of the present invention to provide a surface defect inspection apparatus that can improve the disadvantages of the conventional example, and in particular, can irradiate a surface to be inspected with uniform inspection light and inspect surface defects with high accuracy. And
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, illumination means for irradiating a surface of a curved object to be inspected with a predetermined pattern of inspection light and light receiving means for receiving reflected light from the object to be inspected The surface defect inspection apparatus is equipped with at least two sets of light source units as the illumination means and curvature detection means for detecting the curvature of the curved object to be inspected. The light source units are connected to each other via a predetermined bending member that variably sets the direction of the optical axis of the light source unit, and the angle of each light source unit is changed based on the detection value of the curvature detection means. The angle of the inspection light with respect to the surface of the inspection object is adjusted . With the configuration described above, the angle of each light source unit can be arbitrarily adjusted. That is, it is possible to irradiate each region of the inspection surface with inspection light with an appropriate optical axis. The irradiated light is regularly reflected and received by the light receiving means.
[0007]
According to the second aspect of the present invention, it is possible to adjust on / off of light emission for each system arranged in a crossing manner with the connection direction of the light source units in each light source unit based on the detection value of the curvature detection means. To eliminate the influence of ambient light .
[0008]
In the invention of claim 3, wherein, have I adopted the configuration that the main control unit has a luminous intensity adjusting function of adjusting the intensity of each light source unit. By being configured as described above, the light intensity of the light source unit is adjusted according to the distance from the light source unit to the surface of the inspection object and the curvature of the inspection object.
[0009]
Further, the invention described in claim 4 employs a configuration in which the bending member is provided with a predetermined drive motor, and the other configuration is the same as that of the invention described in claim 1, 2 or 3. With the above configuration, the drive motor adjusts the angle of each light source unit according to the curvature of the object to be inspected.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the surface defect inspection apparatus of the present invention includes an illuminating means 7 that irradiates a surface of a curved inspection object 3 with a predetermined pattern of inspection light 5, and reflected light 9 from the inspection object 3. The illumination means 7 is equipped with at least two sets of light source units 7a, 7b... And a predetermined bending member 15 is provided between the light source units 7a, 7b. . This bending member 15 variably sets the direction of the optical axis of each light source unit 7a, 7b. Further, the surface defect inspection apparatus 1 is equipped with a curvature detection means 17 for measuring the curvature of the inspection object 3, and the bending operation of the bending member 15 and the light source unit 7a based on the detection value of the curvature detection means 17. , 7b... Is also equipped with a main control unit 18 for controlling the light emission operation. This will be described in detail below.
[0011]
[Lighting means]
First, the illumination means 7 equipped in the surface defect inspection apparatus 1 is divided into light source units 7a, 7b... As shown in FIG. And each light source unit 7a, 7b ... is connected by the bending member 15. As shown in FIG. Further, a predetermined drive motor 19 is engaged with the bending member 15 between the light source units 7a, 7b. This drive motor 19 is for changing the angle of each adjacent light source unit 7a, 7b ... so that it may mention later. Specifically, the rotation shaft (not shown) of the drive motor 19 is fixed to one side (for example, 7a) of two adjacent light source units, and the main body of the drive motor 19 is fixed to the other light source unit (for example, 7b). ing.
[0012]
As shown in FIG. 3, each of the light source units 7 a, 7 b... Includes a plurality of LEDs 21, a substrate 23 that carries the LEDs 21, and a diffusion plate 25 disposed on the front surface of the LEDs 21. The light source units 7a, 7b,... Of the present invention have a rectangular planar shape, and five LEDs 21 are arranged in the width direction as shown in FIG. 3 (A), and long as shown in FIG. 3 (B). Twelve are arranged in the vertical direction. Accordingly, a total of 60 LEDs 21 are provided in one light source unit 7a. The number of LEDs 21 mounted on the substrate 23 is an example, and the number of LEDs 21 can be increased or decreased in both the width direction and the length direction of the light source units 7a, 7b.
[0013]
Moreover, the power line 31 from the luminous intensity adjustment means 33 is connected to each LED21 of the light source units 7a, 7b. More specifically, twelve LEDs 21 arranged in the length direction of the light source units 7a, 7b,... Are connected by the same system power line 31, and LEDs adjacent in the width direction are connected to different system power lines ( (See FIGS. 2 and 3). Therefore, in the surface defect inspection apparatus 1 of the present invention, five power lines are connected to each of the light source units 7a, 7b. For this reason, it is possible to turn on / off the light emission and adjust the luminous intensity for each system. In addition, when the number of LED21 increases, it is necessary to increase the number of the said power lines 31 according to this.
[0014]
The diffusion plate 25 disposed on the front surface of the LED 21 is attached to the substrate 23 via a predetermined leg member 27. The diffusion plate 25 is for diffusing the light emitted from the LED 21 slightly and irradiating the inspection object 3 with the uniform inspection light 5. The luminous intensity of the LED 21 of each light source unit 7a, 7b... Is appropriately controlled by the luminous intensity adjusting means 33, and the inspection light 5 having a different luminous intensity can be irradiated to the inspection object 3 for each light source unit. As shown in FIG. 2, in the surface defect inspection apparatus 1 of the present invention, the number of the light source units 7a, 7b... Is 5 in total, but this is an example and can be an arbitrary number. .
[0015]
A control line 37 from the angle adjustment circuit 35 is connected to each drive motor 19 of the illumination means 7 (see FIG. 2). The control line 37 transmits a control signal for changing the mutual angle of the light source units 7 a, 7 b... From the main control unit 18 to the drive motor 19. Each drive motor 19 is controlled independently based on a control signal from the main controller 18. Accordingly, the light source units 7a, 7b,... Connected to each other can take an arbitrary bent shape. More specifically, the bending angle of each light source unit 7a, 7b... Is determined according to the curvature of the inspection object 3 as will be described later.
[0016]
[Curvature detection means]
Next, the curvature detection means 17 will be described. This curvature detection means 17 is for detecting the curvature of the surface of the inspection object 3. Specifically, as shown in FIG. 4, three sensors 41, 42, and 43 are arranged on the same line. The sensors 41, 42, and 43 are distance meters using laser light, and irradiate the surface of the inspection object 3 with laser light, and measure the delay time of the returning laser light to reach the inspection object surface. The distance is measured. The number of sensors 41, 42, and 43 is not limited to three, and may be four or more.
[0017]
FIG. 4B is a diagram showing the principle of curvature measurement of the inspection object 3 using the curvature detection means 17. As described above, the distances L ₁ , L ₂ , L ₃ to the surface of the inspection object 3 are measured by the _three sensors 41, 42, 43, respectively. The curvature measurement unit 44 calculates the curvature from the obtained value. At this time, if the distance between the sensor 41 and the sensor 42 is H1, and the distance between the sensor 42 and the sensor 43 is H2, the radius of curvature R of this region can be obtained from the following equation.
[0018]
R = (M ₁ × M ₂ × M ₃ ) / {2 × H ₁ × (L ₃ -L ₂ ) + 2 × H ₂ × (L ₁ -L ₂ )}
here,
M1 = {H ₁ ² + (L ₁ -L ₂ ) ² } ^1/2
M2 = {H ₂ ² + (L ₃ -L ₂ ) ² } ^1/2
M3 = {(H ₁ + H ₂ ) ² + (L ₁ -L ₃ ) ² } ^1/2
[0019]
[Light receiving means]
Next, the light receiving means 11 used in the surface defect inspection apparatus 1 according to the present embodiment will be described. The light receiving means 11 receives reflected light 9 reflected from the surface of the inspection object 3 and forms an image. Specifically, a CCD camera is used in this embodiment. As shown in FIG. 1, the light receiving means 11 is positioned in a direction in which the reflected light 9 of the inspection light 5 is reflected. Then, the image information obtained by the light receiving means 11 is transmitted to the defect recognition unit 45.
[0020]
[Principle of defect inspection]
FIG. 5 shows the regular reflection characteristics of a circular curved surface. Here, two points a and b on the curved surface will be described. That is, it is assumed that the inspection light 5a is irradiated to the point a from one light source unit of the illumination unit 7. The inspection light 5a is reflected at a point a with the same reflection angle as the incident angle.
The reflected light 5b is reflected to the light receiving means 11 side. Further, it is assumed that the inspection light 5b irradiated to the point b from a different light source unit is regularly reflected at the point b and reflected to the light receiving means 11 side as in the case of the point a. At this time, there is a relationship represented by the following equation between the angles θ ₁ , θ ₂ and θ ₃ in FIG.
[0021]
θ ₃ = θ ₁ + θ ₂
[0022]
That is, if the light source unit for point a and the light source unit for point b are respectively positioned so as to satisfy the above equation, the inspection lights 5a and 5b emitted from the respective light source units are specularly reflected together and the light receiving means 11 Reflect to the side. Therefore, the reflected light 9a and 9b from different points (here, a and b) in the light receiving means 11 are all regular reflected light. Accordingly, the reflected lights 9a and 9b reflected at the points a and b are both reflected light having the same luminous intensity.
[0023]
FIG. 6 is a specific example showing the regular reflection characteristics when the curvature of the inspection object 3 is R = 100 mm. The installation angle θ ₁ (see FIG. 5) of the light receiving means (CCD camera) is set to 20 degrees. Point a to point f indicate the reflection surface of the surface of the inspection object 3. The dotted line in the figure indicates the optical axis from the light source unit (not shown) for each point from point a to point f. Straight lines (hereinafter referred to as “illumination surfaces”) 47a, 47b... Perpendicular to the optical axis were drawn at positions 100 mm and 200 mm away from the curved surface. An extension line of the illumination surface 47c on the optical axis with respect to the point c is indicated by a one-dot chain line.
[0024]
When it is intended to illuminate the curved surface with the planar illumination means, if the illumination means is placed on the alternate long and short dash line 49, at the point a or the point f, the angle between each optical axis and each illumination surface 47a, 47f is illumination with respect to the point c. The surface 47c is narrower than that in the case of the surface 47c, and there is a disadvantage that uniform illumination cannot be obtained. That is, the inspection light with the highest luminous intensity output from each light source unit is in a direction orthogonal to the alternate long and short dash line. Here, since the optical axis and the one-dot chain line with respect to the point c are substantially orthogonal to each other, the inspection light having a high luminous intensity is irradiated to the point c. On the other hand, the optical axis of the inspection light 5a for the point a and the one-dot chain line are not orthogonal. For this reason, the luminous intensity of the inspection light 5a irradiated to the point a will fall compared with the point c.
[0025]
On the other hand, as shown in FIG. 6, when the illumination surfaces 47a, 47b,... Of each light source unit are orthogonal to the optical axes of the inspection lights 5a, 5b,. 5b ... also has a high luminous intensity. That is, in the illumination means 7 used in the present invention, the angle of each light source unit is adjusted so that the optical axes of the inspection lights 5a, 5b... To the points a, b. In this way, it is possible to always irradiate the inspection lights 5a, 5b... With uniform light intensity, and the reflected light 9a, 9b.
[0026]
Here, the method for obtaining the mutual angle between the light source units will be outlined. As shown in FIG. 5, the angle of the optical axis of each point on the curved surface can be obtained by the following mathematical formula.
[0027]
θ ₃ = θ ₁ + θ ₂
[0028]
From this, in FIG. 6, the angle difference between the optical axes 5c and 5d with respect to the point c and the point d can be obtained by the following equation.
[0029]
θ _3d −θ _3c = θ ₁ + θ _2d −θ ₁ −θ _2c
Therefore,
θ _3d −θ _3c = θ _2d −θ _2c
θ _3d −θ _3c = (x _dc ) / r [r: radius of curvature of inspection object]
Here, x _dc is the distance between points c and d on the curved surface, and is set to a predetermined value in advance. Specifically, if the total length of the region to be inspected for surface defects is x _fa and the number of light source units to be used is five, the following equation can be obtained.
[0030]
x _dc = (x _fa ) / 5
[0031]
From the above, the angle between the light source units of the illumination means can be obtained from the measured value of r, and the optimum angle of each light source unit can be controlled.
[0032]
When a defect is present on the surface of the inspection object 3 by irradiating the inspection light with the above illumination device, the defective portion becomes black. This is because the inspection light is not regularly reflected due to the unevenness of the defect. In particular, in the illumination means 7 of the present invention, since the intensity of the inspection light 5a, 5b,... Irradiated on each part is uniform, surface defect inspection over a wide range can be performed with high accuracy.
[0033]
FIG. 7 is a diagram for explaining a state in which the inspection light 5 is irradiated using the light source units 7a and 7b. In FIG. 7, for convenience of explanation, a case where two light source units 7a and 7b are used will be described. Then, the numbers of Line 1 to Line 10 are assigned to the systems of the LEDs 21 of the respective light source units 7a and 7b. Here, for example, when trying to detect a defect on a curved surface by the light of the LED of Line 2, if all the LEDs of other Lines are also lit, the detection by Line 2 is hindered by the diffused light of the LEDs such as Line 7 and Line 8. There is a disadvantage that it will be. That is, Line 7 is originally intended to irradiate point b, but part of the inspection light emitted from Line 7 is also irradiated to point a, and the intensity of light actually irradiated to point a increases. Because it ends up. This is the same even when a conventionally proposed flat illumination means is used.
[0034]
Therefore, in order to solve this problem, all the other lines are turned off while Line 2 is lit, thereby removing the influence of ambient light. This is an effect obtained by using an LED as a light source. The LED utilizes the characteristic that it can be turned on / off faster than other light sources. When actually inspecting the surface defect, the adjacent lines are sequentially emitted to sequentially inspect the surface defects in different regions. Depending on the shape of the inspection object 3, for example, the line 2 is emitted after the line 1 is emitted. Alternatively, the line 3 may be caused to emit light without emitting the light, or the line 4 may be caused to emit light without causing the line 2 and line 3 to emit light.
[0035]
[Surface defect inspection process]
Next, the method of the surface defect inspection apparatus of the present invention will be described with reference to FIG.
First, the curvature detection means 17 detects the curvature of the surface of the inspection object 3 (see FIG. 3). Based on the detected curvature, the illumination control unit 34 adjusts the optical axis angle and luminous intensity of the inspection light 5 with respect to the surface of the inspection object of each of the light source units 7a, 7b. The adjusted inspection light 5 is irradiated on the surface of the inspection object 3. The reflected light 9 reflected from the surface of the inspection object 3 is picked up by a CCD camera as the light receiving means 11 to obtain an image.
And the presence or absence of a surface defect is determined based on the obtained image.
[0036]
FIG. 8 shows an image capturing method. The light source units 7a, 7b... Of the illuminating means 7 are sequentially turned on line by line, and the image at that time is taken with the CCD camera as described above and taken into the memory of the defect recognition unit 45. The captured image is a two-dimensional image of M × N dots and is represented by a density value of 2 ^N gradations per dot. For example, if N = 8, 256 gradations (0 to 255) are obtained. Here, generally, 0 is black and 255 is white. FIG. 9 shows a case where a defect inspection is performed at three locations on the inspection object.
[0037]
When one line image is captured and defect recognition is performed, the next line is turned on, and image capture and defect recognition are performed. Thereafter, the process is repeated sequentially. FIG. 9 shows a flowchart of defect determination. That is, after capturing an image (step S1), a recognition block is drawn (step S2). In this extraction of the recognition block, the inspection light is irradiated by the 1-line LED, and only the whitened portion is set as the recognition target, and the others are not recognized. The following processing is performed only for the recognition target portion.
[0038]
After rendering the recognition block, a binarization process is performed in which a certain density value is set as a threshold value, pixels below the threshold value are set to 0 (black), and pixels above the threshold value are set to 255 (white) (step S3). The threshold is determined using a mode method, a P-tile method, a discriminant analysis method, or the like, which is generally used in image processing techniques. After the binarization process, a labeling process is performed (step S4). In the labeling process, a portion where pixels having a density value of 0 are connected as one lump, and the area (number of lump pixels) is calculated.
[0039]
Next, among the clusters of black pixels obtained as a result of the labeling process, those having an area equal to or larger than a predetermined value are drawn as defects (step S5). This is because the defect on the surface of the inspection object 3 is usually formed with slight irregularities, and the inspection light 5 irradiated to the defect is not specularly reflected but reflected in different directions, and reflected light 9 by the light receiving means 11. This is because the defect area becomes black. FIG. 10 shows an original image at the time of recognition (FIG. 10A) and an image example after binarization processing (FIG. 10B), respectively. FIG. 10 shows a case where two defects are detected within the inspection range of the inspection object 3.
[0040]
【The invention's effect】
As described above, in the surface defect inspection apparatus of the present invention, the illumination means for irradiating the surface of the curved inspection object with a predetermined pattern of inspection light, and the light receiving means for receiving reflected light from the inspection object, And at least two sets of light source units as light sources, and the light source units are connected to each other via a predetermined bent member. Thereby, it is possible to irradiate the inspection light at an arbitrary angle with respect to the surface of the object to be inspected, and it is possible to obtain specular reflection light having a uniform luminous intensity even on different inspection surfaces, and in the curved surface portion of the object to be inspected. However, it is possible to recognize the defect and to improve the recognition accuracy. That is, since the intensity of the image by the reflected light in each region is uniform, the work is simplified even when image processing is performed. Furthermore, by positioning the illuminating means once, an excellent effect is obtained that a wide range of defects can be continuously inspected.
[0041]
In the present invention, the surface defect inspection apparatus is equipped with a curvature detection means for measuring the curvature of the inspection object, and the bending operation of the bending member and the light emission operation of the light source unit are controlled based on the detection value of the curvature detection means. Equipped with a main control unit. For this reason, the optical axis direction of the suitable light source unit according to the curvature of the surface of the object to be inspected can be obtained, and the excellent effect that the efficiency and speeding up of the defect inspection can be improved is produced.
[0042]
Moreover, the main control part of the surface defect inspection apparatus of this invention has a luminous intensity adjustment function which adjusts the luminous intensity of each light source unit. For this reason, the outstanding effect that the optimal luminous intensity of a light source unit can be adjusted according to the distance from the illumination means to each inspection area | region of a to-be-inspected object, and the curvature of a surface is produced.
[0043]
Furthermore, since the bending member is equipped with a predetermined drive motor, the angle of each light source unit can be adjusted automatically, and the excellent effect that the automation of the surface defect inspection line can be promoted is produced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a perspective view showing illumination means used in the surface defect inspection apparatus disclosed in FIG. 1;
3 is a detailed view of the illumination unit disclosed in FIG. 2, FIG. 3 (A) shows a front view of the illumination unit, and FIG. 3 (B) shows a side view.
4A and 4B are diagrams showing curvature detection means used in the surface defect inspection apparatus disclosed in FIG. 1, FIG. 4A shows a perspective view, and FIG. 4B shows a front view.
FIG. 5 is an explanatory diagram showing regular reflection characteristics of inspection light.
FIG. 6 is a diagram illustrating a relationship between an optical axis of inspection light and reflected light.
FIG. 7 is a diagram for explaining an inspection light irradiation method in actual defect inspection.
8 is a diagram showing an image captured by the light receiving means disclosed in FIG. 1. FIG. 8A shows a case where the inspection light is irradiated to the left of the inspection object, and FIG. ) Shows a case where the inspection light is irradiated on the center of the inspection object, and FIG. 8C shows a case where the inspection light is irradiated on the right side of the inspection object.
FIG. 9 shows a flowchart of defect inspection.
10A and 10B are diagrams showing an image of defect inspection, FIG. 10A shows an original image, and FIG. 10B shows an image after binarization processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surface defect inspection apparatus 3 Inspected object 5 Inspection light 7 Illumination means 7a, 7b, 7c, 7d, 7e Light source unit 9 Reflected light 11 Light reception means 15 Bending member 17 Curvature detection means 18 Main control part

Claims (4)

In a surface defect inspection apparatus comprising an illumination unit that irradiates a predetermined pattern of inspection light onto the surface of a curved inspection object, and a light receiving unit that receives reflected light from the inspection object,
This surface defect inspection apparatus is equipped with at least two sets of light source units as the illuminating means and with curvature detection means for detecting the curvature of the curved object to be inspected. The angle of the inspection light with respect to the surface of the object to be inspected by changing the angle of each light source unit based on the detection value of the curvature detection means while connecting through a predetermined bending member that variably sets the direction of the optical axis of the unit A surface defect inspection apparatus characterized by adjusting the above . In a surface defect inspection apparatus comprising an illumination unit that irradiates a predetermined pattern of inspection light onto the surface of a curved inspection object, and a light receiving unit that receives reflected light from the inspection object ,
This surface defect inspection apparatus is equipped with at least two sets of light source units as the illuminating means and with curvature detection means for detecting the curvature of the curved object to be inspected. While connecting through a predetermined bending member that variably sets the direction of the optical axis of the unit, on the basis of the detection value of the curvature detection means, in each light source unit, for each system lined up intersecting the connection direction of the light source unit A surface defect inspection apparatus capable of adjusting on / off of light emission . In a surface defect inspection apparatus comprising an illumination unit that irradiates a predetermined pattern of inspection light onto the surface of a curved inspection object, and a light receiving unit that receives reflected light from the inspection object ,
This surface defect inspection apparatus is equipped with at least two sets of light source units as the illuminating means and with curvature detection means for detecting the curvature of the curved object to be inspected. Surface defect inspection characterized in that the light intensity of each light source unit can be adjusted based on the detection value of the curvature detection means while being connected via a predetermined bending member that variably sets the direction of the optical axis of the unit apparatus.   4. A surface defect inspection apparatus according to claim 1, wherein the bending member is provided with a predetermined drive motor.

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