JPH04134255A - Surface defect inspection device - Google Patents

Abstract

PURPOSE:To sense a defective part with the opening excluded simply and shortly by irradiating the same region to be inspected with beams of illumination light having different intensity levels, and comparing each surface image obtained from reflected light corresponding to each beam of irradiated light. CONSTITUTION:The light case from an illumination apparatus 23 is reflected by a coating film 27 over the surface of a car body 26, and the locational relationship between the illumination apparatus 23 and a CCD camera 24 is controlled so that the beams from reflection are received by this CCD camera 24. In this manner, the camera 24 receives the beams of light reflected by the coating film 27 due to its mirror-face reflectivity and produces a light receipt image in the region to be inspected of the coating film 27. At this time, the difference in the lightness/darkness level is calculated, and the regular reflecting direction of the light changes at a defective part eventually existing in coating within the region to be inspected, and the camera 24 will no more receive the reflected beams otherwise to be received upon regular reflecting. Therefore, a darker part than surroundings is produced in the light receipt image.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention irradiates the surface to be inspected with illumination light and performs image processing on the image obtained by imaging the irradiated area. The present invention relates to a surface defect inspection device that automatically inspects the presence or absence of surface defects on an inspection surface.

[Prior Art] Conventionally, defects such as unevenness occurring on the surface of a product or part have generally been detected by visual inspection by an inspector. However, this visual inspection based on human vision requires a lot of time and effort, is inefficient, and has the problem that the inspection results are influenced by the subjectivity and skill level of the inspector.

As a way to replace this visual inspection by humans with automatic inspection using a surface reduction device, the surface to be inspected is irradiated with illumination light, the irradiated area is imaged with a video camera, etc., and the resulting image is subjected to image processing. A surface defect inspection apparatus has been devised that automatically inspects the surface to be inspected for the presence or absence of surface defects by performing the following steps.

Basically, in this type of device, if there is a surface defect in the light irradiation part, the part of the light receiving surface corresponding to the defective part of the camera light receiving surface that receives the reflected light from the surface to be inspected will not reflect the light. Focusing on the fact that the amount of light received is reduced compared to surrounding healthy surface areas, the defective area is detected as a dark (black) area on the light-receiving image that has a different brightness from the surrounding area.

However, in the above-mentioned type of inspection equipment, the portion of the inspection surface corresponding to the light-receiving surface where the amount of reflected light received is small compared to the surrounding area is determined to be defective. If an opening is provided, this opening will also be detected as a defect.

In other words, to explain the case of detecting surface defects on the painted surface of a car body, for example, the car body after painting has different shapes and sizes due to the attachment of parts that will be retrofitted after the inspection process. Various holes remain, and when the above-mentioned inspection device inspects the painted surface of the vehicle body for surface defects, all of these mounting holes will be detected as defects. For this reason, there is a problem in that it is difficult to automate the inspection process, or even to make it unmanned using a robot or the like.

[Problem to be solved by the invention] To solve this problem, basic patterns such as the shape and size of all the above-mentioned mounting holes are stored in the memory of the inspection device in advance, and defects are detected. In some cases, it may be possible to identify defects and openings such as mounting holes by comparing the detection pattern with the basic pattern described above, but in this case, the memory capacity of the inspection device (image processing device) There are also problems in that the processing program becomes large and the processing time becomes long.

In addition, in Japanese Patent Application Laid-Open No. 2-73139, a predetermined bright and dark striped pattern is projected onto the surface to be inspected, and the resulting image is
By performing image processing including repetition of image contraction processing and image expansion processing, an image including the machined hole (opening) and the defective part and an image showing only the machined hole are created for the same inspected part. It has been proposed to obtain an image that excludes the machined hole and shows only the defective portion by performing a logical product of each corresponding pixel of both images. However, even in this case, it is necessary to repeat complicated processing, so there is still a problem that it is not possible to solve the problems of an enlarged processing program and a long time of image processing.

By the way, the intensity (luminous intensity) is applied to the same inspected area including the defective part.
When illumination lights of different levels are irradiated, the brightness level of the defective portion in each image obtained from the reflected light corresponding to each irradiation light differs depending on the intensity level of the irradiation light. On the other hand, in the case of an opening provided in the car body, the opening does not originally provide reflected light, or even if it does, the reflected light is very small, so if the intensity level of the irradiated light differs, the brightness and darkness on the image There is almost no difference in level. Therefore, by comparing the above two images,
It is possible to identify whether a black dot on the image is a defective part or an opening such as a mounting hole.

Therefore, the present invention irradiates the same inspection area with illumination light of different intensity levels and compares each image obtained from the reflected light corresponding to each irradiation light.
The object of this invention is to provide a surface defect inspection device that can detect only defective portions by excluding the openings in a simple manner and in a short period of time.

[Means for Solving the Problems] Therefore, the first invention of the present application irradiates the surface to be inspected with illumination light and performs image processing on the image obtained by imaging the irradiated portion. In the surface defect inspection apparatus for inspecting the presence or absence of surface defects on the surface to be inspected, a light irradiation means capable of irradiating the same inspection area of the surface to be inspected with irradiation light having different intensity levels; and the irradiation light having different intensity levels. a video signal generation means for receiving reflected light corresponding to each of the above, and converting each of the obtained light reception images into video signals, and a correspondence between the two light reception images based on each video signal output from the video signal generation means. and an image information processing means having an arithmetic unit that calculates the difference in brightness level between each pixel.

Further, the second invention of the present application is the first invention,
A plurality of sets of the light irradiation means and video signal generation means are provided, and each video signal generation means receives reflected light from the light irradiation means of the same set, which corresponds to the light irradiated onto the same inspection area by each of the light irradiation means. They are held at corresponding positions where they can receive only the reflected light corresponding to the irradiated light.

"Effects of the Invention According to the first invention of the present application, each corresponding pixel is It is possible to calculate the difference in brightness level between the two images, and from this calculation result, it is possible to obtain an image that shows the difference in brightness level between the two images.Then, on this image, there are parts where the data is almost zero (0). In other words, by excluding areas where there is almost no difference in brightness level on the image even if the intensity level of the irradiated light is different, and performing defect determination, openings such as mounting holes are excluded from the determination target, and only defective areas can be detected. As a result, the above-mentioned opening can be easily and quickly determined without causing problems such as an increase in memory capacity or processing program, or a long image processing time, unlike conventional methods. Only defective parts can be detected by excluding them from the target.

According to a second invention of the present application, in the first invention, a plurality of sets of the light irradiation means and the video signal generation means are provided, and each video signal generation means is directed to the light irradiation means of the same set. Since they are held at corresponding positions, by setting the intensity levels of the irradiation light from each of the light irradiation means to be different, images of the same inspection area can be simultaneously captured with different intensity levels of the irradiation light. This makes it possible to shorten inspection time.

[Example] Hereinafter, a case where an example of the present invention is applied to an inspection device for inspecting the presence or absence of surface defects on the painted surface of an automobile body will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a car body painting inspection station in an automobile manufacturing line according to this embodiment. As shown in this figure, the inspection station 20 includes a robot device 21 mounted on a pedestal B An illuminator 23 as a light irradiation means and a CCD camera 24 as a video signal generation means are attached to the tip arm 22 of the robot device 21 via a support fitting 25.

As shown in the block diagram of FIG. 2, the robot device 21 is connected to the host computer 1 via a robot controller 2 that controls actuators (not shown) of the device 21, and the illuminator 23 is It is connected to the host computer 1 via a voltage switch 6. Further, the host computer 1 is connected to an image processing device 3 having an image processing processor 4 and an image memory 5, and the CCD camera 24.

In the above configuration, when the painted vehicle body 26 is brought into the inspection station 20, the host computer
The robot controller 2 is operated based on a command from the controller 2, and an actuator (not shown) of the robot device 21 is driven by a control signal from the controller 2. The illuminator 23 and camera 24 are connected to the vehicle body 26.
It is moved while tracing the coating surface 27 of. At this time, the light emitted from the illuminator 23 is reflected by the coating surface 27 on the surface of the vehicle body 26, and this reflected light is
The positional relationship between both 23 and 24 is controlled so that the CD camera 24 receives the light.

In this way, the CCD camera 24 receives the reflected light reflected by the coating surface 27 of the vehicle body 26 due to the specular reflectance of the coating surface 27, and creates a light-receiving image of the area to be inspected on the coating surface 27. . At this time, if there is a paint defect in the area to be inspected, the direction of specular reflection of light changes at the defect, and the reflected light that would normally be reflected and received without this defect changes. The CCD camera 24 no longer receives light. For this reason, a black (dark) part appears in the light-receiving image compared to the surrounding area.

This received light image is converted by the COD camera 24 into a video signal that changes depending on the brightness, and then input to the image processing processor 4 of the image processing device 3, where the processor 4 performs image processing.

By identifying the black portions in the image using image processing technology, the defects can be automatically detected.

In this embodiment, as described above, the host computer 1
A voltage switch 6 is interposed between the test area and the illuminator 23, and by switching the illumination voltage with the switch 6, the area to be inspected can be irradiated with illumination light having different intensities (luminous intensities). Then, by detecting defects in the same manner as described above for the same inspection area while changing the intensity of the illumination light, as shown in FIG. If there is a defect, the mounting hole 11 can be identified as a paint defect 12 on the coating surface 27 and excluded from the defect determination.

Hereinafter, a method for identifying the mounting hole 11 and excluding it from defect determination will be explained with reference to the flowchart of FIG. 4.

When the system starts, first in step t1, the voltage switch 6 is set to, for example, the low voltage side, and the area to be inspected is
irradiate and image the area. At this time, as shown in FIG. 5a, the coating defect portion 12 on the coating surface 27 appears as a relatively black portion P1 compared to the surrounding area. On the other hand, in the mounting hole 11, the reflected light corresponding to the irradiated light is not obtained, or even if it is obtained, the reflected light is very small, so that it is projected as a blacker part Q1 than in the case of the paint defect part 12. This image Z is stored in the image memory 5 of the image processing device 3 (step #2).

Next, in step #3, the voltage switch 6 is switched to the high voltage side, and the same area to be inspected as above is irradiated and imaged. At this time, as shown in FIG. 5b, the defective portion 12 is imaged brightly as the intensity level of the irradiated light is increased, but it is also imaged as a portion P that is darker than the surrounding area. On the other hand, in the attachment hole ti, since almost no reflected light corresponding to the irradiated light is originally obtained, the portion Q is projected as black, to the same extent as in the case of the image Z1 obtained by imaging at the low voltage. This image Z is stored in the image memory 5 (step #4).

Then, in step #5, both the above images Z + , Z
! Based on the data, image processing is performed to exclude the mounting hole 11 from defect determination. That is, the image processing device 3 stores both images 2. ．． 2. A calculation unit (not shown) is provided for calculating the difference in brightness level between corresponding pixels of , and image processing is performed based on the calculation result, and as shown in FIG. ．． ．． 2.
An image Z showing a difference in brightness level (Z-20) is obtained.

At this time, as can be clearly seen from the graph in FIG. 6, the brightness (darkness) of the image portion P corresponding to the defective portion 12 differs depending on the difference in the intensity level of the irradiated light, so that both images Z A difference occurs between I and Z t, and this difference is displayed as a darker area than the surrounding area, as indicated by P3 in FIG. 5c. On the other hand, in the case of the image portion Q corresponding to the mounting hole 2, both images Z1. Since there is almost no difference in brightness in Z2, it is canceled by the image processing described above and is no longer displayed on the image Z3 obtained as the difference between the two images Rzl and zt. That is, the data for the portion Q corresponding to the mounting hole 11 (the broken line portion in FIG. 5c) is zero (0). This image Z.

is stored in the image memory 5 (step #6).

Thereafter, in step #7, it is determined whether or not there is a coating defect in the area to be inspected, and the location of the defect is specified.

At this time, it is sufficient to exclude the area where the data is zero (0) in the image Z3 and perform analysis for defect determination using the image Z1 or the image Z.

As described above, according to this embodiment, there is almost no difference in the brightness level on the image Z3 even if the intensity level of the irradiation light is different, that is, the portion where the data is almost zero (0) on the image Z3. By excluding the defective parts and performing defect determination by 1 step, openings such as the mounting hole 11 are excluded from the determination target, and defective parts! It is possible to detect only 2. As a result, the above-mentioned opening II can be easily and quickly excluded from the determination target, without causing problems such as an increase in memory capacity or processing program, or a long image processing time, as in the past. It is possible to detect only the portion 12.

In the above embodiment, one set of the illuminator 23 and the camera 24 were used to switch the intensity level of the irradiated light, but as shown in FIG. ) illuminators 33a and 33b and cameras 34a and 34b
are provided, and the cameras 34a and 34b are connected to each illuminator 3 described above.
The cameras 3a and 33b are held at corresponding positions that can receive only the reflected light corresponding to the irradiated light from the same set of cameras 33a and 33b among the reflected light corresponding to the irradiated light to the same inspection area 37. At the same time, by setting the intensity levels of the illumination light from each of the illuminators 33a and 33b to be different, it is possible to simultaneously perform imaging of the same inspection area 37 while changing the intensity level of the illumination light. Inspection time can be shortened.

In addition, a conductive substance is added to the paint applied to the surface of the car body, and prior to the above-mentioned surface defect inspection of the paint film surface, a negative charge is applied to the painted workpiece (car body), and a positive electrode is connected to the robot arm. By moving this positive electrode along the car body surface while keeping a predetermined minute distance from the paint film surface, the convex paint defects are scorched and discolored, and the above inspection device detects the defects. When detecting the defective portion, the convex defective portion can be more easily detected. The degree of discoloration of this defective portion can be adjusted by controlling the voltage, and the discolored portion is removed in a post-process repair work.

Note that the above embodiment identifies convex paint defects and mounting holes, but the present invention identifies concave paint defects and mounting holes, and excludes the mounting holes from defect determination. It can also be effectively applied to detect only defective parts.

Further, although the above-mentioned embodiments are limited to the inspection of paintwork on automobile bodies, the present invention is not limited to the above-mentioned case, but can be widely applied to defect inspections on the surfaces of other general objects.

[Brief explanation of the drawing]

The drawings are for explaining the present invention in detail, so FIG. 1 is a perspective view of an automobile body paint inspection station, FIG. 2 is a block diagram of a surface defect inspection device, and FIG.
The figure is an explanatory diagram of the arrangement of the surface to be inspected, an illuminator, and a camera, FIG. 4 is a flowchart explaining the operation of the above-mentioned surface defect inspection device, and FIGS. FIG. 6 is a graph showing the brightness level of each image, and FIG. 7 is an explanatory diagram of the arrangement of the inspected surface, illuminator, and camera showing another embodiment of the present invention. 3... Image processing device, 4... Image processing processor,
6... Voltage switcher, 23, 33a, 33b... Illuminator, 24. 34a, 34b-CCD camera, 27=-paint film surface, 37... Area to be inspected, 2. ．． 2. ．． 23...
image.

Claims (2)

[Claims] (1) In a surface defect inspection device that inspects the presence or absence of surface defects on the surface to be inspected by irradiating the surface to be inspected with illumination light and performing image processing on the image obtained by imaging the irradiated area. , a light irradiation means capable of irradiating the same inspection area of the inspection surface with irradiation light of different intensity levels; and a light irradiation means capable of irradiating the same inspection area of the inspection surface, and receiving reflected light corresponding to the irradiation light of different intensity levels, and each of the obtained received light images. An image comprising a video signal generation means for converting each into a video signal, and a calculation section for calculating the difference in brightness level between corresponding pixels of both light-receiving images based on each video signal output from the video signal generation means. 1. A surface defect inspection device comprising: information processing means. (2) A plurality of sets of the above-mentioned light irradiation means and video signal generation means are provided, and each video signal generation means receives the same set of reflected light corresponding to the irradiation light of the above-mentioned light irradiation means on the same inspection area. 2. The surface defect inspection apparatus according to claim 1, wherein the surface defect inspection apparatus is held at a corresponding position where only the reflected light corresponding to the irradiation light from the irradiation means can be received.