Surface inspection apparatus and surface inspection method

Abstract

The challenge is to efficiently inspect the surface of an object being inspected while it is moving at a predetermined speed. [Solution] The surface inspection device 20 alternately captures multiple images of the object to be inspected 40, alternating between images with a striped pattern projected onto the object and images without the striped pattern projected onto the object. Template matching is performed on the multiple images without stripes using a template image that represents a part of the structure of the object to be inspected 40, thereby calculating correction values ​​in the height direction and correction values ​​in the direction of travel. Then, a corrected inspection image is generated based on the correction values, and the phase corresponding to all pixels is determined using the multiple corrected inspection images, and the three-dimensional coordinates of the object to be inspected 40 are calculated based on the phases. The surface inspection device 20 determines whether or not there is distortion on the surface of the object to be inspected 40 based on the amount of change in the three-dimensional coordinates.

Description

[Technical Field]

[0001] The present invention relates to a surface inspection device and a surface inspection method that can efficiently inspect the surface of an object being inspected that is moving at a predetermined speed. [Background technology]

[0002] Conventionally, it has been necessary to detect and repair defects in the exterior panels of vehicles, such as sheet metal distortion and resin shrinkage. For this purpose, a technique is known that involves capturing multiple images of the vehicle and performing image analysis using the phase-shift method (see, for example, Patent Document 1).

[0003] Specifically, in the phase-shift method, at time t1, a striped pattern is projected onto the vehicle's exterior to capture image 1; at time t2, a striped pattern with a predetermined phase shift is projected onto the vehicle's exterior to capture image 2; and at time t3, a striped pattern with a further predetermined phase shift is projected onto the vehicle's exterior to capture image 3. Image analysis is then performed using these three images, 1 to 3. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-184180 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when measuring vehicles moving on a manufacturing line, the phase shift method cannot be directly applied because the vehicle itself moves during measurement. Therefore, the challenge lies in how to perform image analysis of vehicles moving on conveyor belts, etc. This challenge arises not only when inspecting the exterior of vehicles but also when inspecting the surfaces of various other objects.

[0006] The present invention was made to solve the problems (issues) of the above-mentioned prior art, and aims to provide a surface inspection device and surface inspection method that can efficiently inspect the surface of an object to be inspected while it is moving at a predetermined speed. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a surface inspection apparatus for inspecting the surface of an object to be inspected that moves at a predetermined speed, comprising: stripe pattern projection means for projecting a striped pattern onto the object to be inspected; imaging means for capturing a plurality of striped images including the striped pattern projected from the stripe pattern projection means and reflected on the object to be inspected, and a plurality of non-striped images of the object to be inspected on which the striped pattern is not projected; correction value calculation means for calculating correction values ​​for the pixel positions of the object to be inspected that form a part of each non-striped image based on the plurality of non-striped images; correction inspection image generation means for generating a corrected inspection image for each striped image based on the correction value; and determination means for determining the quality of the surface of the object to be inspected by applying a phase shift method to the plurality of corrected inspection images.

[0008] Furthermore, the present invention is characterized in that, in the above invention, the determination means comprises: a phase calculation means for calculating the phases of a plurality of pixels located at corresponding positions in each of the plurality of corrected inspection images; a coordinate position calculation means for calculating the three-dimensional coordinate position of each pixel of the object to be inspected based on the phases of the plurality of pixels; and a determination means for determining whether the surface of the object to be inspected is good or bad based on the positional relationship between the three-dimensional coordinate position of each pixel of the object to be inspected and the three-dimensional coordinate position of a pixel adjacent to that pixel.

[0009] Furthermore, the present invention is characterized in that, in the above invention, the determination means determines that there is no distortion if the amount of change calculated from the difference between the three-dimensional coordinate position of each pixel of the object to be inspected and the three-dimensional coordinate position of the pixel adjacent to that pixel is smaller than a specific threshold, and determines that there is distortion if the amount of change is larger than a specific threshold.

[0010] Further, in the present invention, in the above invention, the stripe pattern projection means projects a stripe pattern forming the stripe pattern having a sinusoidal luminance distribution with a period corresponding to the moving speed when the inspection object moves on the production line.

[0011] Further, in the present invention, in the above invention, the imaging means alternately images the image with stripes including the stripe pattern projected from the stripe pattern projection means and reflected on the inspection object, and the image without stripes of the inspection object on which the stripe pattern is not projected.

[0012] Further, in the present invention, in the above invention, the correction value calculation means calculates the correction value for correcting the image with stripes by template matching using a template image which is a part of the structure of the inspection object.

[0013] Further, in the present invention, in the above invention, the corrected inspection image generation means performs correction in the height direction and the traveling direction on the image with stripes based on the correction value, and generates the corrected inspection image.

[0014] Further, the present invention is a surface inspection method for a surface inspection apparatus that inspects the surface of an inspection object moving at a predetermined speed, including a stripe pattern projection step of projecting a stripe pattern forming a stripe pattern onto the inspection object, an imaging step of imaging a plurality of images with stripes including the stripe pattern projected from the stripe pattern projection step and reflected on the inspection object, and a plurality of images without stripes of the inspection object on which the stripe pattern is not projected, a correction value calculation step of calculating a correction value for the pixel position of the inspection object forming a part of each image without stripes based on the plurality of images without stripes, a corrected inspection image generation step of generating a corrected inspection image for each image with stripes based on the correction value, and a determination step of applying a phase shift method to the plurality of corrected inspection images to determine the quality of the surface of the inspection object.

Advantages of the Invention

[0015] According to the present invention, surface distortion and sink marks of an object being inspected while moving at a predetermined speed can be efficiently detected. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a diagram showing an overview of a surface inspection apparatus according to an embodiment. [Figure 2] Figure 2 is a functional block diagram showing the configuration of the surface inspection apparatus shown in Figure 1. [Figure 3] Figure 3 shows the timing of acquiring the examination images. [Figure 4] Figure 4 is an explanatory diagram for illustrating template matching. [Figure 5] Figure 5 is an explanatory diagram illustrating the reference coordinates after template matching. [Figure 6] Figure 6 is an explanatory diagram illustrating the generation of corrected inspection images. [Figure 7] Figure 7 is an explanatory diagram illustrating the phase of the target pixel in the corrected inspection image. [Figure 8] Figure 8 is a flowchart illustrating the processing procedure of the surface inspection device. [Figure 9] Figure 9 is a flowchart illustrating the processing steps for acquiring inspection images. [Figure 10] Figure 10 is a flowchart illustrating the processing steps for calculating the correction value. [Modes for carrying out the invention]

[0017] Embodiments of the surface inspection apparatus and surface inspection method according to the present invention will be described in detail below with reference to the drawings.

[0018] <Overview of Surface Inspection Device 20> An overview of the surface inspection apparatus 20 according to this embodiment will now be described. Figure 1 is a diagram showing an overview of the surface inspection apparatus 20 according to this embodiment. As shown in Figure 1, the surface inspection apparatus 20 is connected to a stripe pattern projection unit 23 and an imaging unit 24, and the stripe pattern projection unit 23 and the imaging unit 24 are installed on a support base 30. The objects to be inspected 40a and 40b (hereinafter sometimes collectively referred to as "objects to be inspected 40") are placed on a belt conveyor 50 and move continuously in the direction of the arrow.

[0019] The surface inspection device 20 turns the stripe pattern projection unit 23 on and off to alternately acquire multiple images with and without stripes (S1). Based on the multiple images without stripes, the surface inspection device 20 calculates a correction value in the height direction and a correction value in the direction of travel (S2). Here, the height direction is the vertical direction of the belt conveyor 50, and the direction of travel is the direction of movement of the arrow on the belt conveyor 50.

[0020] Then, the surface inspection device 20 generates a corrected inspection image based on correction values ​​in the height direction and the direction of travel for the striped image (S3). Subsequently, the surface inspection device 20 calculates the three-dimensional coordinates of the object to be inspected 40 based on the corrected inspection image (S4). For example, to calculate the three-dimensional coordinates, the phase of all pixels in the corrected inspection image is calculated using the phase shift method, and the three-dimensional coordinates of the object to be inspected 40 are calculated based on this phase.

[0021] The surface inspection device 20 then determines whether or not there is distortion on the surface based on the three-dimensional coordinates (S5). For example, if the amount of change calculated from the difference between the three-dimensional coordinate position of each pixel of the object to be inspected 40 and the three-dimensional coordinate position of the pixel adjacent to that pixel is within a predetermined threshold, it is determined to be "no distortion". If the amount of change is greater than the predetermined threshold, it is determined to be "distortion present".

[0022] <Configuration of surface inspection device 20> Next, the configuration of the surface inspection apparatus 20 shown in Figure 1 will be described. Figure 2 is a functional block diagram showing the configuration of the surface inspection apparatus 20 shown in Figure 1. As shown in Figure 2, the surface inspection apparatus 20 has a storage unit 25 and a control unit 26, to which a display unit 21, an input unit 22, a stripe pattern projection unit 23, and an imaging unit 24 are connected. The display unit 21 is a display device such as a liquid crystal display that displays various information. The input unit 22 is an input device such as a mouse or keyboard.

[0023] The striped pattern projection unit 23 is a projection device that projects a striped pattern with a predetermined period onto the object to be inspected 40. The period of the projected striped pattern is determined in accordance with the movement speed of the belt conveyor 50. For example, if the belt conveyor 50 moves at 10 cm / second, the period of the striped pattern is set to 10 cm. Here, the period of the striped pattern is the distance from the point where the brightness of the striped pattern formed by the brightness of light and dark is 256 to the next point where the brightness is 256. Furthermore, the projection of the striped pattern projection unit 23 is controlled on / off by the striped pattern projection control unit 26a, which will be described later.

[0024] The imaging unit 24 is a camera that images the object to be inspected 40. The imaging unit 24 captures multiple striped images, which include the striped pattern projected from the striped pattern projection unit 23 and appearing on the object to be inspected 40, and multiple non-striped images of the object to be inspected 40, on which the striped pattern is not projected.

[0025] The storage unit 25 is a storage device such as a hard disk drive or non-volatile memory, and stores template image data 25a, inspection image data 25b, correction value data 25c, and corrected inspection image data 25d. The template image data 25a is image data for performing template matching. For example, it is image data of a part of the structure of the object to be inspected 40. The inspection image data 25b is image data of the object to be inspected 40. The inspection image data 25b includes an image with stripes when a striped pattern is projected onto the object to be inspected 40 from the striped pattern projection unit 23, and an image without stripes when no striped pattern is projected onto the object to be inspected 40.

[0026] The correction value data 25c is data for the correction values ​​in the height and direction of the striped image included in the inspection image data 25b. The corrected inspection image data 25d is image data in which the striped image included in the inspection image data 25b has been corrected in the height and direction of the striped image based on the correction value data 25c.

[0027] The control unit 26 is a control unit that controls the entire surface inspection apparatus 20, and includes a stripe pattern projection control unit 26a, an inspection image acquisition unit 26b, a correction value calculation unit 26c, a corrected inspection image generation unit 26d, a phase calculation unit 26e, a coordinate position calculation unit 26f, a determination unit 26g, and a display control unit 26h. In practice, by loading these programs into the CPU and executing them, the processes corresponding to the stripe pattern projection control unit 26a, the inspection image acquisition unit 26b, the correction value calculation unit 26c, the corrected inspection image generation unit 26d, the phase calculation unit 26e, the coordinate position calculation unit 26f, the determination unit 26g, and the display control unit 26h are made to execute, respectively.

[0028] The striped pattern projection control unit 26a is a processing unit that controls the on / off projection of a striped pattern onto the object to be inspected 40 in order to acquire inspection image data 25b. The inspection image acquisition unit 26b is a processing unit that controls the imaging unit 24 to capture images of the object to be inspected 40 with the striped pattern projected onto it, and images of the object to be inspected 40 without the striped pattern projected onto it. As will be described in more detail later, the inspection image acquisition unit 26b acquires multiple images with and multiple images without stripes alternately.

[0029] The striped pattern projected from the striped pattern projection unit 23 by the striped pattern projection control unit 26a corresponds to the speed at which the object to be inspected 40 moves on the belt conveyor 50. For example, when the object to be inspected 40 is moving at 10 cm / s, the striped pattern has a sinusoidal brightness distribution with a period of 10 cm.

[0030] The correction value calculation unit 26c is a processing unit that calculates correction values ​​for correcting striped images. Specifically, it performs template matching on the striped-free images included in the inspection image data 25b using template image data 25a, which is a part of the structure of the object to be inspected 40, and extracts images that are the same as the template image data 25a included in the striped-free images. Then, it identifies the coordinates of the striped-free image that correspond to the origin coordinates of the template image data 25a. After that, the correction value calculation unit 26c calculates correction values ​​in the height direction and the direction of travel by calculating the difference between the coordinates of the first striped-free image, which was captured first, and the coordinates of the second to fourth striped-free images.

[0031] The corrected inspection image generation unit 26d is a processing unit that generates a corrected inspection image from the striped image based on correction values. As will be described in detail later, the corrected inspection image generation unit 26d corrects the origin coordinates and image region of the striped image based on correction values ​​and generates a corrected inspection image. As a result, a corrected inspection image in which the striped pattern has been shifted is generated.

[0032] The phase calculation unit 26e is a processing unit that calculates the phase for all corresponding pixels using multiple correction images. The coordinate position calculation unit 26f is a processing unit that calculates the three-dimensional coordinates of the object to be inspected 40 based on the phase calculated by the phase calculation unit 26e. Specifically, it calculates the three-dimensional coordinates based on the phase, the distance between the stripe pattern projection unit 23 and the object to be inspected 40, and the distance between the stripe pattern projection unit 23 and the imaging unit 24.

[0033] The determination unit 26g is a processing unit that determines the presence or absence of distortion based on the amount of change in the three-dimensional coordinates of the object to be inspected 40. Specifically, if the amount of change calculated from the difference between the three-dimensional coordinate position of each pixel of the object to be inspected 40 and the pixels adjacent to that pixel is smaller than a predetermined threshold, it is determined that there is "no distortion," and if the amount of change is greater than the predetermined threshold, it is determined that there is "distortion."

[0034] The display control unit 26h is a processing unit that controls the display of the result determined by the determination unit 26g on a predetermined display unit 21. For example, if the determination result is "no distortion", it displays "no distortion" on the predetermined display unit 21, and if the determination result is "distortion present", it controls the display of "distortion present" on the predetermined display unit 21. Note that if the determination result is "no distortion", no display control is required.

[0035] <Timing of acquiring examination images> Next, the timing of inspection image acquisition in the inspection image acquisition unit 26b of the surface inspection device 20 will be explained. Here, we will explain the case in which four striped images and four non-striped images are acquired as inspection images. Figure 3 is a diagram showing the timing of inspection image acquisition. As shown in Figure 3, the surface inspection device 20 turns on the striped pattern projection unit 23 to project a striped pattern onto the object to be inspected 40, and uses the imaging unit 24 to acquire the first striped image A1 of the object to be inspected 40. The surface inspection device 20 acquires the first striped image A1 in 0.05 s.

[0036] Then, the surface inspection device 20 turns off the stripe pattern projection unit 23 and uses the imaging unit 24 to acquire a first stripe-free image B1 on the object to be inspected 40 in which no stripe patterns are projected. The surface inspection device 20 acquires the first stripe-free image B1 in 0.05 s. After that, the surface inspection device 20 pauses imaging using the imaging unit 24 for 0.15 s. In this way, the surface inspection device 20 acquires one striped image and one stripe-free image in 0.25 s.

[0037] The surface inspection device 20 acquires a second striped image and a second striped image, a third striped image and a third striped image, and a fourth striped image and a fourth striped image, in the same manner as when it acquired the first striped image and the first striped image.

[0038] <About template matching> Next, template matching in the correction value calculation unit 26c of the surface inspection device 20 will be explained. Figure 4 is an explanatory diagram for illustrating template matching. As shown in Figure 4(a), the surface inspection device 20 reads template image data 25a, which is a part of the structure of the object to be inspected 40, from the storage unit 25. Here, the origin coordinates (Xt0, Yt0) of the template image are set to the upper left position of the image.

[0039] Then, as shown in Figure 4(b), the surface inspection device 20 reads out the first stripe-free image B1 and performs template matching in the direction of the arrow based on the template image. Here, template matching involves scanning the template image over the first stripe-free image B1, calculating the similarity at each position, and detecting the position with the highest similarity. For calculating the similarity, methods such as calculating the cross-correlation coefficient or the sum of squared errors can be used.

[0040] <Calculation of Correction Value> Next, the calculation of the correction value of the surface inspection device 20 will be explained. Figure 5 is an explanatory diagram for explaining the reference coordinates after template matching. As shown in Figure 5(a), when the surface inspection device 20 performs template matching using the first striped image B1, it identifies the reference coordinates of the striped image B1 corresponding to the origin coordinates of the template image at the position where the similarity between the template image and the striped image B1 is greatest as (Xn1, Yn1).

[0041] Furthermore, as shown in Figure 5(b), when the surface inspection device 20 performs template matching using the second stripe-free image B2, it identifies the reference coordinates of the stripe-free image B2 corresponding to the origin coordinates of the template image at the position where the similarity between the template image and the stripe-free image B2 is greatest as (Xp2, Yp2).

[0042] The surface inspection device 20 then calculates a correction value h1 = Xp2 - Xn1 in the direction of travel and a correction value V1 = Yp2 - Yn1 in the height direction, based on the reference coordinates (Xn1, Yn1) of the first stripe-free image B1 and the reference coordinates (Xp2, Yp2) of the second stripe-free image B2.

[0043] The surface inspection device 20 specifies the reference coordinates of the third non-striped image B3 and the fourth non-striped image B4 according to the above-described procedure. Then, correction values h2 in the traveling direction and V2 in the height direction are calculated based on the reference coordinates of the first non-striped image B1 and the reference coordinates of the third non-striped image B3.

[0044] Furthermore, the surface inspection device 20 calculates correction values h3 in the traveling direction and V3 in the height direction based on the reference coordinates of the first non-striped image B1 and the reference coordinates of the fourth non-striped image B4.

[0045] <Generation of corrected image> Next, generation of the corrected inspection image by the surface inspection device 20 will be described. Here, correction in the traveling direction will be described. FIG. 6 is an explanatory diagram for explaining generation of the corrected inspection image. As shown in FIG. 6(a), when the surface inspection device 20 generates the first corrected inspection image C1 based on the first striped image A1, the origin coordinates (X

[0046] , 01 , 02 , 01 , , 01 , 01 , 02 , 01 , f1 , 01 , , 01 , , 01 , 01 , 02 , 01 , 02 , 02 , Y 01 ) of the first striped image A1 are shifted by the third correction value h3 to coordinates (X 01 + h3, Y 01 ), which are set as the corrected origin coordinates (X’ 01 , Y’ 01 ) of the first corrected inspection image C1, and all pixels in the region having the origin coordinates (X 01 , Y 01 ) and the coordinates (X’ 01 , Y’ f1 ) as diagonals are deleted to generate the corrected inspection image C1.

[0046] When the surface inspection device 20 generates the corrected inspection image C2 based on the second striped image A2, as shown in FIG. 6(b), the origin coordinates (X 02 , Y 02 ) of the second striped image A2 are shifted by the difference (h3 - h1) between the third correction value h3 and the first correction value h1 to coordinates (X 02 + (h3 - h), Y 01 ), which are set as the corrected origin coordinates (X’ 02 , Y’ 02) and the origin coordinates (X 02 , Y 02 ) and coordinates (X' 02 , Y' f2 Delete all pixels in the region that is diagonally opposite to ).

[0047] Furthermore, the surface inspection device 20 determines the final coordinate (X) of the second striped image A2. f2 , Y f2 ) and coordinates (X f2 -h1, Y 02 Delete all pixels in the region with the diagonal of ) and generate a corrected inspection image C2.

[0048] When the surface inspection device 20 generates a corrected inspection image C3 based on the third striped image A3, the origin coordinates (X) of the third striped image A3 are as shown in Figure 6(c). 03 , Y 03 The coordinate (X) is shifted by the difference (h3 - h2) between the third correction value h3 and the first correction value h1. 03 +(h3-h2), Y 03 ) is the corrected origin coordinate (X' of the third corrected examination image C3. 03 , Y' 03 ) and the origin coordinates (X 03 , Y 03 ) and coordinates (X' 03 , Y' f3 Delete all pixels in the region that is diagonally opposite to ).

[0049] Furthermore, the surface inspection device 20 determines the final coordinate (X) of the third striped image A3. f3 , Y f3 ) and coordinates (X f3 -h2, Y 03 Delete all pixels in the region with the diagonal of ) and generate a corrected inspection image C3.

[0050] When the surface inspection device 20 generates a corrected inspection image C4 based on the fourth striped image A4, the origin coordinates (X) of the fourth striped image A4 are as shown in Figure 6(d). 04 , Y 04 The correction origin coordinates of the fourth corrected inspection image C4 are set to ).The surface inspection device 20 then sets the final coordinates (X) of the fourth striped image A4. f4, Y f4 ) and coordinates (X f4 -h3, Y 04 Delete all pixels in the region with the diagonal of ) to generate corrected inspection image C4. Note that, similar to the correction in the direction of travel, the height correction value should be used to correct the Y-axis direction of the striped images A1-A4.

[0051] <Calculation of the phase of the target pixel> Next, the calculation of the phase of the surface inspection device 20 will be explained. Figure 7 is an explanatory diagram for explaining the phase of the target pixel in the corrected inspection image. As shown in Figure 7, the surface inspection device 20 converts the brightness of the corrected inspection images C1 to C4 into a phase at the coordinates of a specific pixel. For example, if the brightness of a specific pixel in the corrected inspection image C1 is 255, the phase is set to 0°, and if the brightness of a specific pixel in the corrected inspection image C2 is 128, the phase is set to 90°.

[0052] Furthermore, if the brightness of a specific pixel in the corrected inspection image C3 is 0, the phase is set to 180°, and if the brightness of a specific pixel in the corrected inspection image C4 is 128, the phase is set to 270°. The surface inspection device 20 then applies a sine wave based on the characteristics of the phase and brightness values ​​of the obtained stripe pattern, and calculates the phase of the target image by comparing it with the sine wave (dashed line) of the projected stripe pattern.

[0053] The surface inspection device 20 performs a phase transformation from the same brightness value for all pixels of the corrected inspection images C1 to C4 and calculates the phase of the target pixel. The surface inspection device 20 calculates the three-dimensional coordinates of the surface of the object to be inspected 40 based on the relationship between the obtained phase of each pixel and the three-dimensional positions of the stripe pattern projection unit 23 and the imaging unit 24. The method for obtaining three-dimensional coordinates from the phase using the phase shift method is a well-known technique and will not be explained here.

[0054] <Processing procedure for surface inspection device 20> Next, the processing procedure of the surface inspection device 20 will be described. Figure 8 is a flowchart illustrating the processing procedure of the surface inspection device 20. As shown in Figure 8, the surface inspection device 20 performs inspection image acquisition processing to acquire four images with stripes and four images without stripes (step S101). Then, the surface inspection device 20 performs correction value calculation processing using the four images without stripes (step S102).

[0055] Subsequently, the surface inspection device 20 generates a corrected inspection image based on the correction value (step S103). Then, the surface inspection device 20 calculates the phase for each pixel based on the four corrected inspection images (step S104). After that, the surface inspection device 20 calculates the three-dimensional coordinates of the object to be inspected 40 based on each phase (step S105).

[0056] The surface inspection device 20 determines whether or not there is a change in the amount of change of the three-dimensional coordinates that exceeds a predetermined threshold (step S106). If the surface inspection device 20 determines that there is a change in the amount of change of the three-dimensional coordinates that exceeds a predetermined threshold (step S106: Yes), it determines that there is "distortion" (step S107). If the surface inspection device 20 determines that there is no change in the amount of change of the three-dimensional coordinates that exceeds a predetermined threshold (step S106: No), it determines that there is "no distortion" (step S108).

[0057] The surface inspection device 20 then controls the display of the determination result on a predetermined display unit 21 (step S109).

[0058] <Processing procedure for imaging and processing of inspection images> Next, the processing procedure for the inspection image acquisition process of the surface inspection device 20 will be described. Figure 9 is a flowchart illustrating the processing procedure for the inspection image acquisition process. As shown in Figure 9, the surface inspection device 20 projects a striped pattern onto the object to be inspected 40 (step S201) and captures an image with stripes (step S202).

[0059] Then, the surface inspection device 20 stops projecting the striped pattern (step S203) and captures an image without stripes (step S204). After that, the surface inspection device 20 determines whether a predetermined time has elapsed (step S205). If the predetermined time has not elapsed (step S205: No), it waits until the predetermined time has elapsed. If the predetermined time has elapsed (step S205: Yes), it determines whether four sets of images have been captured (step S206). One set is one pair of images: one with stripes and one without.

[0060] If the surface inspection device 20 has not captured four sets of images (step S206: No), it proceeds to step S201. If it has captured four sets of images (step S206: Yes), it proceeds to step S102 of the main flow (Figure 8).

[0061] <Processing procedure for calculating corrected values> Next, the processing procedure for calculating the correction value of the surface inspection device 20 will be described. Figure 10 is a flowchart illustrating the processing procedure for calculating the correction value. As shown in Figure 10, the surface inspection device 20 reads a template image (step S301). Then, the surface inspection device 20 reads a stripe-free image B1 (step S302).

[0062] Subsequently, the surface inspection device 20 performs template matching (step S303) and identifies predetermined reference coordinates (step S304). Then, the surface inspection device 20 reads the next stripe-free image (step S305) and performs template matching (step S306). After that, the surface inspection device 20 identifies predetermined coordinates (step S307).

[0063] The surface inspection device 20 calculates a correction value based on the identified reference coordinates (step S308). Then, the surface inspection device 20 determines whether or not it has processed all the stripe-free images (step S309). If the surface inspection device 20 has not processed all the stripe-free images (step S309: No), it proceeds to step S305 and processes the next stripe-free image. If the surface inspection device 20 has processed all the stripe-free images (step S309: Yes), it proceeds to step S103 of the main flow (Figure 8).

[0064] As described above, in this embodiment, the surface inspection device 20 alternately captures multiple images of the object to be inspected 40, one with a striped pattern projected onto it and the other without the striped pattern projected onto it. Template matching is performed on the multiple images without stripes using a template image that represents a part of the structure of the object to be inspected 40, thereby calculating correction values ​​in the height direction and correction values ​​in the direction of travel. Then, a corrected inspection image is generated based on the correction values, and the phase corresponding to all pixels is determined using the multiple corrected inspection images, and the three-dimensional coordinates of the object to be inspected 40 are calculated based on the phases. The surface inspection device 20 determines whether or not distortion is present based on the amount of change in the three-dimensional coordinates.

[0065] In the above embodiment, the surface inspection device 20 was described as acquiring four images each of the object to be inspected 40 with and without stripes, but it is sufficient to acquire three or more images.

[0066] Furthermore, although the above embodiment describes a case in which distortion is determined based on the amount of change in the three-dimensional coordinates of the object to be inspected 40, a Fourier transform may be applied based on the phase of the pixels located at the corresponding positions in the corrected inspection image, the high-frequency components of the Fourier transform may be extracted, and if the high-frequency components exceed a predetermined threshold, it may be determined that distortion is present.

[0067] The configurations illustrated in each of the above embodiments are functional schematics and do not necessarily have to be physically represented as shown. In other words, the distributed and integrated forms of each device are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions. [Industrial applicability]

[0068] The surface inspection apparatus and surface inspection method according to the present invention are suitable for efficiently inspecting the surface of an object being inspected that is moving at a predetermined speed. [Explanation of Symbols]

[0069] 20 Surface inspection equipment 21 Display section 22 Input section 23 Striped pattern projection section 24 Imaging Department 25 Memory section 25a Template image data 25b Examination image data 25c Correction Value Data 25d Corrected Inspection Image Data 26 Control Unit 26a Stripe pattern projection control unit 26b Examination Image Acquisition Unit 26c Correction Value Calculation Unit 26d Correction Inspection Image Generation Unit 26e Phase calculation section 26f Coordinate position calculation section 26g Judgment part 26h Display Control Unit 30 Support stand 40, 40a, 40b Items to be inspected 50 Belt conveyor

Claims

1. A surface inspection device that performs surface inspection of an object to be inspected while moving at a predetermined speed, A striped pattern projection means for projecting a striped pattern onto the object to be inspected, An imaging means for capturing multiple striped images including the striped figure projected from the striped figure projection means and projected onto the object to be inspected, and multiple non-striped images of the object to be inspected where the striped figure is not projected, A correction value calculation means calculates a correction value for the pixel position of the object to be inspected that forms a part of each stripe-free image based on the plurality of stripe-free images, For each striped image, a correction inspection image generation means generates a correction inspection image based on the correction value, A determination means for determining the quality of the surface of the object to be inspected by applying a phase shift method to the plurality of corrected inspection images. A surface inspection apparatus characterized by being equipped with the following features.

2. The determination means is, A phase calculation means for calculating the phases of multiple pixels located at corresponding positions in each of the multiple correction inspection images, A coordinate position calculation means that calculates the three-dimensional coordinate position of each pixel of the object to be inspected based on the phase of the plurality of pixels, A determination means for determining the quality of the surface of the object to be inspected based on the positional relationship between the three-dimensional coordinate position of each pixel of the object to be inspected and the three-dimensional coordinate position of a pixel adjacent to that pixel. The surface inspection apparatus according to claim 1, characterized by comprising:

3. The determination means is, The surface inspection apparatus according to claim 2, characterized in that if the amount of change calculated from the difference between the three-dimensional coordinate position of each pixel of the object to be inspected and the three-dimensional coordinate position of a pixel adjacent to that pixel is smaller than a specific threshold, it is determined that there is no distortion, and if the amount of change is larger than a specific threshold, it is determined that there is distortion.

4. The aforementioned striped figure projection means is The surface inspection apparatus according to claim 1, characterized in that it projects a striped figure having a sinusoidal brightness distribution with a period corresponding to the movement speed when the object to be inspected moves along the manufacturing line.

5. The imaging means is The surface inspection apparatus according to claim 1, characterized in that it alternately captures images of a striped image including the striped figure projected from the striped figure projection means and reflected on the object to be inspected, and images of the object to be inspected without the striped figure.

6. The correction value calculation means is The surface inspection apparatus according to claim 1, characterized in that it calculates the correction value for correcting the striped image by template matching using a template image which is a part of the structure of the object to be inspected.

7. The correction inspection image generation means is The surface inspection apparatus according to claim 1, characterized in that it performs height and propagation direction corrections on the striped image based on the correction value to generate the corrected inspection image.

8. A surface inspection method for a surface inspection apparatus that inspects the surface of an object to be inspected while moving at a predetermined speed, A striped pattern projection step in which a striped pattern is projected onto the object to be inspected, An imaging step for capturing multiple striped images including the striped figure projected from the striped figure projection step and reflected on the object to be inspected, and multiple non-striped images of the object to be inspected where the striped figure is not projected, A correction value calculation step, based on the plurality of stripe-free images, calculates a correction value for the pixel position of the object to be inspected that forms a part of each stripe-free image, For each striped image, a correction inspection image generation step is performed to generate a corrected inspection image based on the correction value, A determination step in which a phase shift method is applied to the plurality of corrected inspection images to determine whether the surface of the object to be inspected is good or bad. A surface inspection method characterized by including the following.

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