JP3100448B2 - Surface condition inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for illuminating a surface to be inspected with bright and dark light whose luminance gradually changes in one direction, and receiving reflected light reflected from the surface to be inspected. To form
The present invention relates to a surface condition inspection apparatus for inspecting the surface condition of the surface to be inspected based on a change in luminance in the received light image.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of irradiating a surface to be inspected with light and inspecting the surface state of the surface to be inspected, for example, for the presence or absence of surface defects such as irregularities, based on the reflected light from the surface to be inspected. . For example, Japanese Patent Application Laid-Open No. 62-233710 discloses that a non-inspection surface is irradiated with light, reflected light from the inspection surface is projected on a screen, and the surface defect of the inspection surface is determined from the sharpness of the projected image. Has been disclosed that automatically detects the

As one of the surface state inspection methods as described above, a surface to be inspected is irradiated with light, a light reflected from the surface to be inspected is received to form a light-receiving image, and a luminance change in the light-receiving image is performed. Is a method for inspecting the surface state of the surface to be inspected on the basis of, in order to improve the inspection efficiency and inspection accuracy, as the light to irradiate the surface to be inspected, not uniform light with uniform brightness, A method using bright and dark light having a brightness gradient in which the brightness gradually changes in one direction has been considered (Japanese Patent Application Nos. 3-134092 and 3-225038).

[0004]

In general, when light is irradiated to a surface to be inspected and light reflected from the surface to be inspected is received to form a light-receiving image, the amount of light reflected from the surface to be inspected is usually large. Also, since the amount of reflected light from the background (a part other than the surface to be inspected) is small, the luminance of the surface to be inspected corresponding to the surface to be inspected in the received image is large (bright), and the luminance of the background region corresponding to the background is small. (Dark), and therefore, when the light to be irradiated on the inspection surface is uniform light having uniform luminance, the inspection surface region and the background region can be clearly distinguished from each other by the luminance difference. Will also be clear.

However, when the light to be irradiated on the surface to be inspected is bright and dark light whose luminance gradually changes in one direction as described above, bright light (luminance) in the region of the inspected surface in the received image. Is large, but the luminance of the inspected surface area where dark light (light with low luminance) is reflected is small, and thus the inspected surface area where the bright light is reflected. The background region and the background region can be clearly identified based on the luminance difference, and the boundary between them is also clear. The two cannot be clearly distinguished,
The boundary between the two is also unclear, resulting in the following problem.

That is, when the inspection surface area and the background area exist in the received light image, the defect may be detected not only from the inspection area but also from the background area due to various causes such as noise. In such a case, it is necessary to output only defects detected in the inspection surface area as true defect information. However, when the boundary between the inspection surface area and the background area is unclear as described above, it is accurately determined in which area the defect detected near the unclear boundary is a defect. Therefore, there is a problem that the inspection accuracy is reduced.

Further, when the relative positional relationship between the object to be inspected and the inspection device is known in advance, for example, when the painted surface of a car carried into the inspection station is inspected by a surface condition inspection device of a robot, The boundary between the inspection surface area and the background area in the received light image can be obtained by the calculation. However, such a boundary detection method is based on the premise that the object to be inspected is always located at a predetermined inspection position that is set in advance. Mounting errors occur,
As a result, there is a problem that the boundary detection accuracy is low, leading to a decrease in defect inspection accuracy.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to accurately detect a boundary between a surface area to be inspected and a background area in a surface state inspection apparatus using light and dark light as described above, thereby improving inspection accuracy. It is another object of the present invention to provide a surface condition inspection apparatus which can achieve the above.

[0009]

In order to achieve the above object, a surface state inspection apparatus according to the present invention irradiates a surface to be inspected with bright and dark light whose luminance gradually changes along one direction,
A surface condition inspection apparatus for receiving a reflected light reflected from the inspection surface to form a light reception image, and inspecting a surface state of the inspection surface based on a luminance change in the light reception image, wherein the light reception image A surface area to be inspected having a luminance with a large difference from the luminance of the background area in the surface area to be inspected, and based on position information relating to the surface area to be inspected, the background of the surface area to be inspected is detected. The image processing apparatus further includes a boundary detection unit that detects a boundary between the latent inspection surface area having a luminance with a small difference from the luminance of the area and the background area.

In the above-mentioned surface condition inspection apparatus, the boundary detecting means may detect the actual object having a large difference between the luminance of the background area and the luminance of the background area in the inspected surface area in the received light image. Detect the inspection surface area,
Based on the position information regarding the surface area to be inspected, the boundary between the background area and the latent area to be inspected having a small difference in luminance with the luminance of the background area in the area to be inspected is configured to be detected. can do.

The bright and dark light whose brightness gradually changes in one direction may be a bright and dark light whose brightness changes only once or a plurality of times when the brightness changes gradually. Bright and dark light that repeats may be used.

[0012]

When the light and dark light are irradiated as described above, there are a visible surface area to be clearly distinguished from a surface area to be inspected and a background area, and a latent surface area to be unclearly distinguishable. However, according to the surface condition inspection apparatus of the present invention, the boundary detecting means detects the surface area to be inspected based on the luminance difference from the background area, and the position information of the surface area to be inspected, particularly It is possible to detect the unclear boundary between the latent inspection surface area and the background area based on the information on the boundary position between the inspection plane area and the background area, so that it is possible to know the entire boundary between the inspection plane area and the background area. The inspection accuracy can be improved thereby.

The detection of the unclear boundary between the latent inspection surface area and the background area based on the position information of the actual inspection surface area is performed, for example, based on the boundary position information between the actual inspection surface area and the background area. Can be detected by linearly extending, or when there are a plurality of actual inspected surface regions, since there are a plurality of boundaries between the actual inspected surface regions and the background region, the boundaries can be detected. .

Further, since the boundary detection is performed based on image data in the received light image, the boundary detection is performed based on the relative positional relationship between the inspection object and the inspection apparatus. There is no possibility that a boundary detection error occurs due to an error in loading or mounting an object to the inspection position, and high-precision boundary detection is possible.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of a surface condition inspection apparatus according to the present invention. The illustrated surface condition inspection device 2 is a device that inspects the surface condition of the painted surface 6 of the vehicle body of the automobile 4, that is, detects a coating defect such as unevenness existing on the painted surface. Are arranged in the vicinity. Surface condition inspection device 2
Is a robot 10 mounted on a pedestal 8 and the robot 10
Irradiating means 14 and C attached to the distal arm 12
Imaging means 16 such as a CD camera; robot control means 18 for controlling the operation of the robot; image processing means 20 for processing image data of a received image formed by the imaging means 16; Image processing means
And a host computer (total control means) 22 connected to and controlling them.

The robot control means 18 drives and controls a predetermined actuator (not shown) built in the robot 10 based on a command given by the host computer 22. The means 16 is moved along the painted surface 6 of the automobile, which is the surface to be inspected. At this time, light is emitted from the light irradiating means 14 to the surface 6 to be inspected, and the light is reflected from the surface 6 to be inspected serving as a mirror surface. The reflected light is received by the imaging means 16, and the imaging means 16 forms a light-receiving image based on the received reflected light, outputs image data of the received light to the image processing means 20, and outputs the image data.
Reference numeral 20 denotes a processing unit that processes the input image data to determine whether the inspection surface area (the area corresponding to the inspection surface 6) and the background area (the background, that is, the part other than the inspection surface 6 such as the automobile 4 in the inspection station K) (A region corresponding to a mounting table or a floor portion on which the device is placed) and a surface defect in the inspection surface region determined by the detection of the boundary, that is, the presence or absence of a coating defect such as unevenness, and a defect. The position, defect shape, etc. are detected.

The light irradiating means 14 has a light emission surface 14a.
Emit light and dark light that changes gradually along one direction above.
Specifically, as shown in FIG. 2, the light irradiating means 14 includes a plurality of fluorescent lamps (particularly limited to fluorescent lamps) as light sources provided in a box 24 having an open front (light emitting surface) side. , And an optical filter 28 and a diffusion screen 30 provided on the front side of the fluorescent lamps 26 and closing the front of the box 24. Above optical filter
The reference numeral 28 indicates that the light emitted from each fluorescent lamp 26 changes its luminance gradually along one direction of the light emitting surface 14a (in this embodiment, the X direction in the drawing), that is, from bright to dark or from dark to dark. In order to convert into light and dark light that gradually changes to light, the light transmittance gradually changes at each position in the X direction (the light transmittance is the same at each position in the Y direction). . Accordingly, the light emitted from the light irradiation means 14 of this embodiment is, for example, as shown in FIG.
The left and right ends of the diffusion screen 30 shown in FIG. 2 are the bright and dark lights whose brightness gradually changes from large to small from the other end (the right end of the diffusion screen 30 shown in FIG. 2).

The diffusing screen 30 is for diffusing the light transmitted through the optical filter 28 and irradiating the painted surface (inspection surface) 6 of the automobile with bright and dark light evenly.
The brightness gradient of the bright and dark light formed by the optical filter 28 is set in advance to a predetermined gradient in order to improve the accuracy of defect detection. However, when the painted surface 6 has a curved surface shape, Since the amount of reflected light changes depending on the magnitude of the curvature, and the luminance gradient in the received image changes, the curvature of the painted surface 6 is adjusted so that the luminance gradient in the received image does not lower the defect detection accuracy. Accordingly, it is desirable to set a transmittance change gradient of the optical filter 26 so as to irradiate light and dark light having a predetermined brightness gradient.

Next, the formation of a received light image by the image pickup means 16 and the detection of a surface defect based on the received light image will be described. FIGS. 4 and 5 are diagrams showing a light irradiation state by the light irradiation unit 14 and an imaging state by the imaging unit 16 when a convex defect 32 and a concave defect 34 exist on the inspection surface (painted surface) 6, respectively. .

As described above, the light emitting means 14 emits light from the light emitting surface.
14a, the luminance gradually changes along the X direction (in this embodiment, the luminance decreases from the left end to the right end in the X direction in FIGS. 4 and 5; Bright and dark light is irradiated onto the surface 6 to be inspected, and the reflected light from the surface 6 to be inspected is received by the imaging means 16 to form an image (light-receiving image) of the surface 6 to be inspected by the reflected light. You. In the figure, S is a light irradiation area by the light irradiation means 14, F is a field of view of the imaging means 16, and a light receiving image of this field of view F is formed in the imaging means 16.

The light irradiating means 14 is arranged opposite to the inspected surface 6 so as to irradiate bright and dark light onto the inspected surface 6 as shown in the figure, and the imaging means 16 is reflected from the inspected surface 6. They are arranged to face the surface 6 to be inspected so as to receive light and form a light-receiving image, and both 14 and 16 maintain a constant positional relationship with each other and have an appropriate positional relationship with the surface 6 to be inspected. In the secured state, it is moved along the inspection surface 6 and a defect inspection is performed.

FIGS. 6 and 7 correspond to FIGS. 4 and 5, respectively.
FIG. 3 is a diagram showing a light receiving image in FIG. As shown in these figures, the light receiving image 36 along the X ₁ direction in which the luminance of light emitted through the light exit plane 14a of the light irradiation unit 14 corresponding to the X direction of changing from large to small, the luminance It gradually changes from large to small. In FIGS. 6 and 7, the brightness is higher as the density of the vertical lines n is lower, and the brightness is lower as the density of the vertical lines n is higher.

In the light receiving image 36 as described above, if there are defects 32 and 34 on the surface 6 to be inspected, the defects 32 and 34 change the regular reflection direction of the light from the light irradiating means 14 and thereby the light receiving image An area 32A corresponding to the defects 32 and 34 in 36,
The luminance at 34A is different from the surrounding luminance, and the luminance change state is different from the surrounding luminance change state.

That is, when the defect is a convex defect 32, as shown in FIG. 4, the convex defect 32 acts as a so-called convex mirror. Bright light from the mirror is specularly reflected and enters the imaging means 16,
On the other hand, from the right side 32b of the defect 32, the dark light from the low-luminance portion 40 of the light irradiation means 14 is specularly reflected and enters the imaging means 16,
Convex defect corresponding region 32A in the received-light image 36 as shown in the Results Figure 6, the left area (convex defect region 32A in which the luminance of the entire light receiving image 36 becomes smaller toward the X ₁ direction 32
Area corresponding to the left side 32a) has a higher luminance than the surrounding area,
Right side area of area 32A (area corresponding to right side 32b of convex defect 32)
Has lower brightness than the surroundings.

In the case where the defect is a concave defect 34, as shown in FIG. 5, the concave defect 34 acts as a so-called concave mirror. Dark light is specularly reflected and is incident on the imaging means 16,
On the other hand, from the right surface 34b of the defect 34, bright light from the high luminance portion 38 of the light irradiation means 14 is specularly reflected and enters the imaging means 16,
Consequently view in received-light image 36 of the as shown in 7 concave defects corresponding region 34A is left area of the region 34A in which the luminance of the entire light receiving image 36 becomes smaller toward the X ₁ direction (concave defects 34
Area corresponding to the left side 34a) has lower brightness than the surrounding area,
The right side area of the area 34A (the area corresponding to the right side 34b of the convex defect 34)
Is brighter than the surroundings.

The received light image 36 as described above is input from the imaging means 16 to the image processing means 20, and the image processing means 20 detects a defect based on the input received light image data.

[0028] That is, the image processing unit 20 performs the entire scan by performing sub-scanning along the perpendicular Y ₁ direction received-light image 36 inputted to the X ₁ direction with main scanning along the X ₁ direction . In this case, the defect corresponding region 32A, the main scanning line (pixel row) not passing through 34A luminance in L ₁ (image signal level) in the received-light image 36 shown in FIGS. 6 and 7 X ₁
It simply decreases linearly in the direction,
Brightness in the main scanning line L ₂ passing through a convex defect corresponding regions 32A in FIG. 6, convex defect corresponding region as shown in FIG. 8
After increased once at 32A moiety greatly decreases and also will be increased, also the brightness of the differential value in the main scanning line L ₂ (the difference in brightness comrades of adjacent pixels on the main scanning line L ₂₎ in FIG. 9 As shown in the figure, the area once increases in the convex defect corresponding area 32A, then decreases greatly, and then increases and decreases.

The concave defect corresponding area 34A in FIG.
Brightness in the main scanning line L ₂ passing through is larger increased to also becomes possible to decrease after once decreased by concave defects corresponding region 34A portion as shown in FIG. 10, also the brightness of the differential value at the main scanning line L ₂ As shown in FIG. 11, once decreases at the concave defect corresponding region 34A, then increases greatly and then decreases and increases.

Therefore, the light receiving image 36
, And the luminance on each main scanning line is differentiated. When the differentiated value exceeds a predetermined threshold value (+ Th, -Th) (see FIGS. 9 and 11), a defect is detected at the position where the difference is exceeded. Exists,
And when the differential value exceeds + Th, it is a convex defect and −
If it exceeds Th, it can be detected that the defect is a concave defect.

Next, detection of the boundary between the inspection surface area and the background area based on the light receiving image 36 will be described. Figures 12, 13
FIG. 3 is a plan view showing the relationship between the automobile 4 to be inspected and the received light image 36.

When the painted surface 6 of the automobile 4 is inspected as a surface to be inspected, the automobile 4 is usually placed on the floor of an inspection station or on an inspection table and inspected. When the painted surface 6 is inspected, the light receiving image 36 includes the inspected surface region 44 corresponding to the inspected surface 6 and a background (a part other than the inspected surface 6, for example, a floor or an inspection table on which the automobile 4 is mounted). ) Is present in the background area 46.

In this case, it is checked whether the defect detected by the above-described method is located in the inspection surface area 44 or the background area 46, and the defect located in the background area 46 is regarded as noise or the like. It is desirable to detect only the defect located in the inspection surface area 44 as a true defect or to inspect only the inspection surface area 44 because it is caused and not a true defect. It is necessary to know the boundary between the inspection surface area 44 and the background area 46 in the light receiving image 36.

However, when the bright and dark light whose luminance gradually changes as described above is used, as shown in FIG. 13, the luminance of the background area 46 is small in the light-receiving image 36 and the inspection surface area 44 is small. the brightness toward the X ₁ direction changes from large to small depending on the brightness of the dark light reflected (intensity enough density of the horizontal line p in FIG. 13 is sparse is large, the luminance is small enough is dense) Therefore, the region 44a where the luminance is high in the inspection surface region 44 (FIG. 12)
) Can be clearly distinguished from the background region 46 based on the luminance difference and the boundary between them can be clearly known.
Of the area 44b (see FIG. 12) having a small luminance, the luminance is not much different from the luminance of the background area 46, and therefore cannot be clearly distinguished from the background area 46 based on the luminance difference. Also can not know clearly.

Therefore, in the surface condition inspection apparatus 2, the image processing means 20 is provided with a boundary detection means 48, and the boundary detection means 48 detects the unclear boundary q.

The above-mentioned boundary detecting means 48 is provided to detect the surface area of the surface to be inspected (the luminance difference from the background area 46 is large) having a luminance that is large in difference from the luminance of the background area 46 in the area to be inspected 44 in the received light image 36. 44a
Is detected, and based on the positional information on the actual inspected surface area 44a, the potential inspected surface area (the difference between the background area 46 and the A boundary q between 44b and the background area 36 is detected.

An embodiment of the boundary detection by the boundary detecting means 48 will be described with reference to a flowchart shown in FIG. First, the received light image 36 input in S1
Is binarized. That is, the image signal level (luminance) of each pixel is divided according to whether it is equal to or greater than a predetermined threshold value Th, and pixels equal to or greater than Th are set to “1”, and pixels smaller than Th are set to “0”. As a result of this binarization, a large luminance portion or the like caused by noise or the like in the above-described surface area to be inspected 44a and the defect corresponding areas 32A and 34A becomes "1" (white area in the figure on the right side of S1). The area 44b and the background area 46 are "0"
(The hatched portion in the figure on the right side of S1). Then, in S2, among the "1" regions in the binary image, a "1" region having an area equal to or larger than a predetermined value is detected.
As a result, of the “1” region, only the actual inspection surface region 44a is detected.

After detecting the surface area 44a to be inspected as described above, the boundary q between the surface area 44b and the background area 46 is detected from the position information of the surface area 44a.
In this detection, the background region 46 is located at approximately which portion of the imaging information known in advance, that is, the received light image 36, and the apparent inspected surface region 44a and the latent inspected surface region 44b are located at approximately which portion. Is performed with reference to the information. Such information includes information indicating which part of the painted surface 6 of the automobile 4 the light-receiving image 36 is photographing, and to which direction the light / dark light from the light irradiating means 14 gradually changes from light to dark. , And the received light image 36 is
Which part of the painted surface 6 is photographed can be obtained from the approximate position of the automobile 4 on the inspection station and the positions of the light irradiation means 14 and the imaging means 16 by the robot.

In the case of the present embodiment, S
Lower ring portion of the second right manifestation inspected surface region 44a as shown in figures are positioned on the lower side of the potential test surface area 44b and manifestation test surface area 44a (boundary) r ₁ and can know that there is a boundary q and right limbus (boundary) r right boundary r ₂ of the upper extension on the potentially test surface region 44b and the background area 46 of the _two, first manifested in S3 track limbus of the inspected surface area 44a in the direction of arrow D, the in S4 1 st corner points c ₁ and second look corner point c _2, whereby the manifest test surface area 44a and the background area 46 A boundary r ₂ is detected, and subsequently, in S5, the boundary r ₂
Is extended upward, that is, a straight line connecting the coordinates of c ₁ and c ₂ is extended upward, and the extended portion is detected as the boundary q.

When the boundary q is detected, the surface area to be inspected 44 is determined based on the boundary q in S6 as shown in the figure on the right side of S6. The defect is detected by such a method, and the detected defect data is output from the image processing means 20.

Next, another embodiment of the boundary detection will be described. In the above-described embodiment, the light irradiating means 14 irradiates the light with gradual change in luminance only once, but the light irradiating means 14 has a plurality of gradual changes in luminance as shown in FIG. It may be one that emits bright and dark light that is repeated several times. Note that the length of the line segment m in the drawing indicates the magnitude of the luminance.

In this case, the binarized image of the received light image 36 as shown in FIGS. 12 and 13, for example, is as shown in FIG. Therefore, in such a case, for example, the right boundary r _{2 of} the three detected inspection surface areas 44a is detected.
Are obtained, for example, the coordinates of an arbitrary point on three boundaries r ₂ are obtained, a line segment including the plurality of points is obtained by the least square method, and each potential inspection surface area 44b is placed on the line segment.
The boundary q between the image and the background area 46 is detected as being located.

[0043]

As described above, the surface condition inspection apparatus according to the present invention detects an actual inspection surface area having a luminance having a large difference from the luminance of the background area among the inspection surface areas in the received image, as described above. Boundary detection means for detecting a boundary between a latent inspection surface area having a small difference in luminance with a luminance of a background area of the inspection surface area and the background area based on the position information regarding the actual inspection surface area Therefore, the boundary detection means detects the surface area to be inspected based on the luminance difference from the background area, and detects the position information of the surface area to be inspected, particularly the position between the surface area to be inspected and the background area. Based on the boundary position information, it is possible to detect an unclear boundary between the latent inspection surface area and the background area, thereby enabling detection of only true defects in the inspection surface area, thereby improving inspection accuracy. Can be.

Since the boundary detection is performed based on the image data of the received light image, the boundary detection can be performed with high accuracy without being affected by an error in loading the inspection object to the inspection position or a mounting error. Detection becomes possible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a light irradiation unit in FIG. 1;

FIG. 3 is a diagram showing a luminance distribution in the light irradiation unit of FIG. 2;

FIG. 4 is a diagram showing an example of a relationship between a light irradiation unit and an imaging unit in FIG.

FIG. 5 is a diagram showing another example of the relationship between the light irradiation unit and the imaging unit in FIG.

FIG. 6 is a view showing a received light image formed by the image pickup means in FIG. 4;

FIG. 7 is a diagram showing a light-receiving image formed by the imaging unit in FIG. 5;

8 shows the brightness on the line L ₂ in FIG. 6

9 is a diagram illustrating a differential value of luminance on the line L ₂ in FIG. 6

10 is a view showing luminance on the line L ₂ in FIG. 7

11 is a diagram illustrating a differential value of luminance on the line L ₂ in FIG. 7

FIG. 12 is a diagram illustrating a relationship between a surface area to be inspected and a background area in a received light image;

FIG. 13 is a diagram showing luminance in a received light image.

FIG. 14 is a flowchart showing the procedure of boundary detection.

FIG. 15 is a diagram showing another example of the light irradiation means.

FIG. 16 is a diagram showing a binarized state of a received light image when the light irradiation unit shown in FIG. 15 is used.

[Explanation of symbols]

 6 Inspection surface 14 Light irradiation means 16 Imaging means 20 Image processing means 48 Boundary detection means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-64559 (JP, A) JP-A-62-294946 (JP, A) JP-A-1-210807 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/91 G06T 7/00

Claims (2)

(57) [Claims] 1. A method of irradiating a surface to be inspected with bright and dark light whose luminance gradually changes in one direction, receiving light reflected from the surface to be inspected, forming a light receiving image, What is claimed is: 1. A surface state inspection apparatus for inspecting a surface state of a surface to be inspected on the basis of a luminance change in an image, wherein: Detecting an inspection surface area, and, based on the position information regarding the surface area to be inspected, the potential inspection surface area having a small luminance difference from the luminance of the background area in the inspection surface area and the background area; A surface condition inspection apparatus comprising a boundary detecting means for detecting a boundary. 2. A method according to claim 1, wherein said boundary detecting means detects a surface area to be inspected in said light receiving image, said surface area having a large difference from a luminance of a background area and a luminance greater than a luminance of said background area. Detecting a boundary between a potential inspection surface area having a small luminance difference from the luminance of a background area in the inspection surface area and the background area based on the position information regarding the actual inspection inspection surface area. The surface condition inspection apparatus according to claim 1, wherein: