Visual inspection method and visual inspection device

Abstract

To provide a visual inspection method using a visual inspection device which can facilitate a visual inspection in the whole circumference of a side surface of a cylindrical body and improve accuracy of the visual inspection when the cylindrical body such as a cap in a conveyance line is the inspection target.SOLUTION: A visual inspection method using a visual inspection device comprises: a photographed image acquisition step of imaging a side surface of a cylindrical body using a plurality of imaging units to acquire a plurality of photographed images; and a distortion correction step of creating a distortion correction image by performing planar conversion processing of developing the image of the side surface of the cylindrical body in each photographed image on the plane with coordinate conversion. In the distortion correction step, in a case where irregularities exist on the side surface of the cylindrical body, irregularity reduction processing of reducing a distortion of the image of the side surface of the cylindrical body due to the irregularities is further performed on the basis of the edge end shape in the image of the side surface of the cylindrical body.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a visual inspection method and a visual inspection device. [Background technology]

[0002] A conventional appearance inspection method is known that can precisely correct perspective distortion caused by differences in distance between each part of the object and the camera based on the outer surface shape of the object, and can significantly reduce errors in pattern matching processing by correcting distortion around the image even when multiple images are combined to form a single planar image, thereby enabling highly accurate appearance inspection. This appearance inspection method includes a data input step of previously inputting three-dimensional shape data of the object's inspection surface and its relative position with a CCD camera, an imaging step of capturing multiple images of the entire inspection surface with multiple CCD cameras, with at least some of the images overlapping, an image correction step of correcting distortion in each image based on the three-dimensional shape data and developing them into a single planar image, thereby creating multiple planar images with at least some overlapping, and an image combining step of combining the overlapping portions of the multiple planar images to create a single outer surface image, and is characterized in that the appearance inspection of the object is performed using the outer surface images (see, for example, Patent Document 1).

[0003] A cylindrical body visual inspection method for inspecting the appearance of a cylindrical body is also known. This cylindrical body visual inspection method is characterized by including a reference image acquisition step in which a side image of a reference cylinder is cylindrically developed to obtain a converted image in which the curved surface is flattened, and this step is repeated multiple times by rotating the cylinder to obtain a composite image of the entire circumference of the cylinder as a reference image. Also known is a label inspection method characterized by including a label acquisition step in which label image data of an inspection object to which one or more types of labels are randomly attached are acquired, a setting step in which discrimination areas are set at specific positions on each type of label, an imaging step in which the inspection surface of the inspection object is imaged, a discrimination step in which labels are discriminated based on the discrimination areas in the outer surface image of the imaged inspection surface, and an inspection step in which the labels are inspected using the outer surface image (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-128261 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-151720 [Patent Document 3] Patent Publication No. 2021-096116 Summary of the Invention [Problem to be solved by the invention]

[0005] The inspection methods disclosed in the above Patent Documents 1 to 3 all include a step of capturing an image of the side surface of a cylinder with a camera and acquiring a planar image by unfolding the side surface image based on the acquired side surface image. However, in the inspection methods disclosed in Patent Documents 1 and 3, multiple cameras are used to capture images of the side surface of a cylinder from multiple directions, and a single planar image is acquired by combining planar images obtained by unfolding each side surface image. However, there is a risk that the combined parts of the single planar image will look unnatural. Furthermore, if the side surface of the cylinder to be inspected has uneven parts, there is a risk that the uneven parts will look unnatural when the side surface image is unfolded into a planar image. Furthermore, in the inspection method disclosed in Patent Document 2, it is considered that the side surface of the cylinder is captured using a single camera. In this case, it is impossible to capture the entire circumference of the side surface of the cylinder in a single capture, and it takes multiple cameras to capture the entire circumference of the side surface of the cylinder. For example, if multiple cylindrical objects are being transported on an automatic transport line, the automatic transport line must be stopped each time the cylindrical object is rotated and images are taken multiple times, which can be inefficient.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its ultimate objective is to provide an appearance inspection method and an appearance inspection device that, when inspecting cylindrical objects such as caps on a conveying line, makes it easy to perform an appearance inspection of the entire circumference of the side of a cylindrical object, or that enables improvement in the accuracy of the appearance inspection. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides: A visual inspection method for inspecting the visual appearance of a side surface of a cylindrical body, comprising: an image acquisition step of acquiring a plurality of images by using a plurality of imaging devices to capture images of the side surface of the cylindrical body from different circumferential directions; a distortion correction step of performing a plane transformation process of developing an image of the side surface of the cylindrical body in each of the captured images onto a plane by coordinate transformation to create a distortion-corrected image, This is an appearance inspection method characterized in that, in the distortion correction process, if unevenness exists on the side surface of the cylinder, an unevenness reduction process is further performed to reduce distortion in the image of the side surface of the cylinder caused by the unevenness based on the edge shape in the image of the side surface of the cylinder.

[0008] According to the present invention, in the image acquisition process, it is possible to capture an image of the entire circumference of the side surface of a cylinder, regardless of the orientation of the cylinder. Furthermore, since multiple imaging devices can be used to capture an image of the entire circumference of the side surface of a cylinder, the effort of taking multiple images while rotating the cylinder is eliminated, which is efficient. Furthermore, when the side surface of a cylinder has unevenness, distortion in the image of the side surface of the cylinder caused by the unevenness makes it difficult to perform a visual inspection of the uneven portion, for example. However, in the distortion correction process, the distortion in the image of the side surface of the cylinder is eliminated, making the visual inspection easier or improving the accuracy of the visual inspection.

[0009] The present invention may also be an appearance inspection method further comprising: a compositing step of cutting out overlapping portions of each of the plurality of distortion-corrected images created from the captured images and combining the plurality of distortion-corrected images from which the overlapping portions have been removed to create a single composite image; and a correction step of correcting the composite image of the image of the side surface of the cylindrical body so that a predetermined reference position in the composite image is positioned at one end of the composite image. This makes appearance inspection easier because the compositing step can combine the plurality of distortion-corrected images into a single composite image. Furthermore, the correction step can correct the composite image into a planar image of the side surface of the cylindrical body without overlapping portions, based on the predetermined reference position, so that the same planar image can always be obtained.

[0010] Furthermore, the present invention may be a visual inspection method characterized in that the reference position is the position of a reference mark previously provided on the side surface of the cylindrical body, which makes it easy to determine the reference position.

[0011] Furthermore, in the present invention, the distortion correction step may also be an appearance inspection method characterized in that it includes a captured image display step of displaying the selected captured image, a correction range display step of displaying a grid-like frame image superimposed on the cylindrical body in the captured image displayed in the captured image display step, and a parameter setting step of setting parameters for calculating the amount of distortion correction for the cylindrical body superimposed and displayed with the grid-like frame image in the correction range display step, and that each of the captured images is corrected to the distortion-corrected image based on the parameters set in the parameter setting step so that the intervals of the grid lines in the grid-like frame image in the X direction are uniform, and then displayed. When creating a distortion-corrected image from an image, it is possible to visually confirm that the distortion at both ends of the side of the cylinder in the captured image has been eliminated. It is also possible to acquire the distortion-corrected image as saved data.

[0012] Furthermore, the present invention may be an appearance inspection method characterized in that, in the correction range display step, the grid-shaped frame image is displayed based on the X-direction length and Y-direction length of the edge shape of the grid-shaped frame image that are set manually or automatically. According to this, when the shape of the side surface of the cylinder is simple, it is possible to manually display the grid-shaped frame image superimposed on the cylinder in the captured image with relatively high accuracy, and when the shape of the side surface of the cylinder is complex, it is possible to automatically display the grid-shaped frame image superimposed on the cylinder in the captured image in a relatively short time.

[0013] Furthermore, the present invention may be an appearance inspection method characterized in that, in the parameter setting step, the parameters include at least one of the distance between one of the plurality of image sensors and the cylinder, the diameter of the top surface of the cylinder, or the inclination of the cylinder with respect to the one image sensor. This makes it possible to easily set parameters, and to easily set the diameter of the cylinder, the distance between the image sensor and the cylinder, the inclination of the cylinder with respect to the image sensor, etc. based on the parameters, and to calculate the amount of distortion correction.

[0014] In addition, in the present invention, the compositing step may be an appearance inspection method including: an image number setting step for setting the number of distortion-corrected images to be combined; a combination range setting step for setting a combination range by cutting out overlapping portions of the distortion-corrected images for the number of distortion-corrected images set in the image number setting step; a distortion adjustment step for expanding the combination range set in the combination range setting step onto a plane and adjusting the distortion; a combination step for combining the distortion-corrected images adjusted in the distortion adjustment step to create and display a combined image; and a combined image adjustment step for adjusting misalignment of each of the distortion-corrected images in the combination step in the X direction and / or the Y direction to create and display the combined image. This allows visual confirmation that there are no overlapping portions or misalignment in the combined distortion-corrected images when creating a combined image from the distortion-corrected images and creating a composite image from the combined images. The composite image can also be acquired as saved data.

[0015] Furthermore, the present invention may be an appearance inspection method characterized in that, in the combined image adjustment step, a range of shading or brightness for which the misalignment is to be adjusted and a range of pixels that constitutes an allowable range for the misalignment are set. This makes it possible to prevent unnecessary adjustment of parts of the combined image where no misalignment occurs, which would instead result in misalignment occurring.

[0016] Furthermore, the present invention may be an appearance inspection method characterized in that in the combined image adjustment step, the magnification of each of the distortion-corrected images is adjusted to a reference magnification. In this way, the magnification is uniform in all regions even in the planar image obtained by correcting the composite image, making the appearance inspection easier or improving the accuracy of the appearance inspection.

[0017] In addition, in the present invention, a combining step of cutting out overlapping portions of each of the distortion-corrected images created from the plurality of captured images of the side surface of the cylindrical body, and combining the distortion-corrected images from which the overlapping portions have been cut out to create a single combined image; The visual inspection method may also include a correction process for correcting the composite image of the image of the side surface of the cylinder so that a predetermined reference position is located at one end of the composite image.

[0018] According to the present invention, independently of capturing an image of the side of a cylinder and creating a distortion-corrected image from each of a plurality of captured images of the side of the cylinder, it is possible to create a composite image from the distortion-corrected image and modify the composite image to obtain a planar image.

[0019] In addition, in the present invention, A visual inspection device for inspecting the visual appearance of a side surface of a cylindrical body, a plurality of imaging devices installed to capture images of the side surface of the cylindrical body from different directions in the circumferential direction; a correction unit that acquires a plurality of captured images from each of the plurality of image capture devices, and performs a plane transformation process to develop an image of the side surface of the cylinder in each of the captured images onto a plane by coordinate transformation, thereby creating a distortion-corrected image; The correction unit may be an appearance inspection device characterized in that, when unevenness is present on the side surface of the cylinder, distortion of the image of the side surface of the cylinder caused by the unevenness is reduced based on the edge shape in the image of the side surface of the cylinder.

[0020] According to the present invention, it is possible to efficiently acquire planar images of the entire circumference of the side surface of a cylinder using a simple device configuration. This solves the problem of areas of the side surface of the cylinder not being able to be inspected because they are not captured in the image acquired by the imaging device, or because the image of the side surface of the cylinder is distorted due to unevenness in the side surface of the cylinder, thereby improving the inspection accuracy of the entire circumference of the side surface of the cylinder.

[0021] The present invention may also provide an appearance inspection device that further includes a compositing unit that cuts out overlapping portions of the plurality of distortion-corrected images created from the captured images and combines the plurality of distortion-corrected images from which the overlapping portions have been removed to create a single composite image, and a correction unit that performs a correction process on the composite image of the side surface of the cylindrical body so that a predetermined reference position in the composite image is positioned at one end of the composite image. This further facilitates appearance inspection, as the compositing unit combines the plurality of distortion-corrected images into a single composite image. Furthermore, the correction unit corrects the composite image into a planar image of the entire circumference of the side surface of the cylindrical body without overlapping portions, based on the predetermined reference position, making it possible to consistently obtain the same planar image.

[0022] In addition, the present invention may be an appearance inspection apparatus characterized in that the reference position is the position of a reference mark previously provided on the side surface of the cylindrical body, which makes it easy to determine the reference position.

[0023] The present invention may also provide an appearance inspection device further comprising: a display unit that displays the captured images acquired from each of the plurality of imaging devices and a grid-like frame image superimposed on the cylindrical body in the captured images; and an input unit that sets parameters for calculating the amount of distortion correction for the cylindrical body superimposed with the grid-like frame image, wherein the correction unit corrects each of the captured images to create the distortion-corrected image based on the parameters set in the input unit so that the grid lines in the grid-like frame image are spaced uniformly in the X direction, and the display unit displays the distortion-corrected image. In this way, when creating the distortion-corrected image from the captured images, it is possible to visually confirm on the display unit that distortion at both ends of the side surface of the cylindrical body in the captured images has been eliminated. Furthermore, the parameters used to create the distortion-corrected image from the captured images can be visually confirmed on the input unit.

[0024] Furthermore, in the present invention, the visual inspection device may be characterized in that the display unit displays the grid-shaped frame image based on the X-direction length and the Y-direction length of the edge shape of the grid-shaped frame image that are manually or automatically set in the input unit. According to this, when the shape of the side surface of the cylindrical body is simple, it is possible to manually and relatively accurately determine the shape of the cylindrical body in the captured image. It is possible to display a grid-like frame image superimposed on the cylinder in the captured image, and if the shape of the side of the cylinder is complex, it is possible to automatically and in a relatively short time display a grid-like frame image superimposed on the cylinder in the captured image.

[0025] Furthermore, in the present invention, the appearance inspection apparatus may be characterized in that the parameters set in the input unit include at least one of the distance between one of the plurality of image sensors and the cylinder, the diameter of the top surface of the cylinder, or the inclination of the cylinder with respect to the one image sensor. This makes it possible to easily set parameters, and to easily set the diameter of the cylinder, the distance between the image sensor and the cylinder, the inclination of the cylinder with respect to the image sensor, etc. based on the parameters, and to calculate the amount of distortion correction.

[0026] Furthermore, the present invention may be an appearance inspection apparatus characterized in that the input unit sets the number of distortion-corrected images to be combined and the range to be combined by cutting out overlapping portions of each of the distortion-corrected images for that number of distortion-corrected images, and then the combining unit expands and adjusts the distortions in the range to be combined set by the input unit onto a plane by coordinate transformation, combines the adjusted distortion-corrected images to create a combined image, and adjusts misalignment of each of the distortion-corrected images in the combined image in the X direction and / or the Y direction to create the combined image, and the display unit displays the combined image and then displays the combined image. This makes it possible to visually confirm on the display unit that there are no overlapping portions or misalignment in the combined portions of the distortion-corrected images when creating a combined image from the distortion-corrected images.

[0027] Furthermore, in the present invention, the visual inspection device may be characterized in that the compositing unit creates the composite image by setting, in the input unit, a range of shading or brightness for which the misalignment is to be adjusted and a range of pixels that is an allowable range for the misalignment. This makes it possible to prevent unnecessary adjustment of parts in the combined image where no misalignment occurs, which would instead result in misalignment occurring.

[0028] In addition, in the present invention, the visual inspection device may be characterized in that the synthesis unit adjusts the magnification of each of the distortion-corrected images to a reference magnification, whereby the magnification is uniform across all regions of the planar image acquired from the correction unit, making visual inspection even easier.

[0029] In addition, in the present invention, a synthesis unit that cuts out overlapping portions of each of distortion-corrected images created from a plurality of captured images of the side surface of the cylindrical body, and synthesizes the plurality of distortion-corrected images from which the overlapping portions have been cut out, to create a single synthetic image; The visual inspection device may also include a correction unit that performs correction processing on the composite image so that a predetermined reference position in the composite image of the image of the side surface of the cylinder is located at one end of the composite image.

[0030] The visual inspection device of the present invention may also be configured to include a synthesis unit and a correction unit, independent of the multiple image capture devices and correction unit.

[0031] The above means for solving the problems can be used in combination with each other whenever possible. [Effects of the Invention]

[0032] According to the present invention, when a cylindrical object such as a cap on a conveying line is to be inspected, it is possible to easily inspect the appearance of the entire circumference of the side surface of the cylindrical object, or to improve the accuracy of the appearance inspection. This makes it possible to: [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a functional block diagram showing an example of a visual inspection apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the procedure of the appearance inspection method using the appearance inspection apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is an explanatory diagram specifically showing the procedure in the flowchart shown in FIG. [Figure 4] FIG. 4 is a diagram for supplementarily explaining the procedure for creating a planar image from the captured image shown in FIG. [Figure 5] FIG. 5 is a flowchart showing in more detail the flow of the distortion correction process shown in FIG. [Figure 6] Figures 6A and 6B are explanatory diagrams showing an example of the content displayed on the display unit of the UI in the distortion correction process shown in Figure 2. Figure 6C is an enlarged view for explaining the shape of the end of the side surface of the workpiece in the captured image shown in Figure 6A. [Figure 7] FIG. 7 is a flowchart showing in more detail the flow of the synthesis steps shown in FIG. [Figure 8] 8A and 8B are explanatory diagrams showing an example of the content displayed on the display unit of the UI in the combining step shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0034] [Application example] An outline of an application example of the present invention will be explained below with reference to some of the drawings. The present invention can be applied to a visual inspection device 1 as shown in Fig. 1. Furthermore, by using the visual inspection device 1, the present invention can be applied to a process as shown in the flowchart of Fig. 2.

[0035] FIG. 1 is a functional block diagram showing an example of an appearance inspection device 1 to which the present invention can be applied. The appearance inspection device 1 in this application example is broadly configured to include multiple cameras 10a-10f, a computing unit 11 (e.g., a CPU), a UI (User Interface) 12, and a memory unit (not shown) that stores and accumulates the results of computations performed by the computing unit 11. In this application example, the appearance inspection device 1 is used for side inspection (e.g., appearance inspection to check for dirt or scratches on the side of the workpiece 2) of the workpiece 2 (e.g., a cap), which is the object of inspection and corresponds to the cylindrical body in this invention. Furthermore, in this application example, side inspection is part of the entire production process, and the appearance inspection device 1 is used to inspect the sides of multiple workpieces 2, one by one, as they are continuously transported by a conveyor belt 3 (e.g., a conveyor). Note that dotted arrows in FIG. 1 indicate functional flows. Also, in FIG. 1, the cameras 10a-10f, the workpiece 2, and the conveyor belt 3 are shown in a schematic top view.

[0036] The cameras 10a-10f are used to capture images of the workpiece 2 as the first step in side surface inspection. The cameras 10a-10f are installed at a height that captures the side surface of the workpiece 2 and are positioned around the workpiece 2 as it passes a predetermined position. The cameras 10a-10f capture images of the workpiece 2 as it passes the predetermined position, so that the entire periphery of the side surface of the workpiece 2 is captured comprehensively in multiple captured images (shown in FIG. 3) acquired from each of the cameras 10a-10f. While the cameras 10a-10f preferably capture images simultaneously, they may also capture images at different times. The distance WD from the camera 10a to the center of the workpiece 2 is approximately 130 mm, and the same applies to the other cameras 10b-10f. In this application example, the number of cameras 10a-10f is six, but this number is not limited as long as the entire periphery of the side surface of the workpiece 2 is captured comprehensively. In addition, above the predetermined position, there is a light (not shown) for illuminating the workpiece 2 when it passes through the predetermined position. The distance from the lighting to the top surface of the workpiece 2 is approximately 5 mm. Here, the cameras 10a to 10f correspond to the multiple imaging devices of the present invention.

[0037] The calculation unit 11 is configured with a correction unit 110, a synthesis unit 111, and a correction unit 112. The correction unit 110 acquires captured images from each of the cameras 10a-10f. Because the captured images are of the side surfaces of the workpiece 2, distortion occurs at both ends of the side surfaces of the workpiece 2 in the captured images toward the depth of the captured images, making them appear blurred compared to the center of the side surfaces of the workpiece 2. The correction unit 110 develops the side surfaces of the workpiece 2 into a flat surface by coordinate transformation, and if the side surfaces of the workpiece 2 have irregularities, similarly develops the irregularities into a flat surface by coordinate transformation, thereby creating a distortion-corrected image (shown in FIG. 3) from the captured images. This correction eliminates distortions at both ends of the side surfaces of the workpiece 2 in the captured images and distortions caused by the irregularities. The synthesis unit 111 acquires multiple distortion-corrected images from the correction unit 110. The multiple distortion-corrected images each have overlapping portions, and the synthesis unit 111 combines the distortion-corrected images by cutting out the overlapping portions, and adjusts the misalignment of each of the combined distortion-corrected images to create a single composite image (shown in FIG. 3). The correction unit 112 acquires the composite image from the synthesis unit 111. Reference marks (shown in FIG. 3) are marked on the side of the workpiece 2, and the correction unit 112 corrects the composite image to a planar image (shown in FIG. 3) of the entire periphery of the side of the workpiece 2 without overlapping portions, based on the reference marks. Note that the appearance inspection device 1 includes multiple calculation units 11, and the correction unit 110, synthesis unit 111, and correction unit 112 may be included in each of the multiple calculation units 11. Details will be described below with reference to FIGS. 3, 6A, 6B, 8A, and 8B.

[0038] The UI 12 is configured with a display unit 121 and an input unit 122. The display unit 121 acquires and displays the captured image, distortion-corrected image, composite image, and planar image from the calculation unit 11. This allows the user of the visual inspection device 1 to visually check the process from the captured image to the creation of a planar image. The input unit 122 instructs the calculation unit 11 on the algorithm required to create a planar image from the captured image based on the set parameters. Details will be described below with reference to Figures 6A, 6B, 8A, and 8B.

[0039] 2 is a flowchart showing the procedure of an appearance inspection method using an appearance inspection device 1 to which the present invention can be applied. Only an outline of the flow will be explained in this application example, and details will be explained in the following examples.

[0040] In the appearance inspection method using the appearance inspection device 1 of this application example, as described above, first, cameras 10a-10f are used to capture an image of the workpiece 2 so that the entire periphery of the side of the workpiece 2 is captured comprehensively, including overlapping portions, and then the captured images are acquired from each of cameras 10a-10f. Next, the side of the workpiece 2 is expanded into a plane using coordinate transformation. If the side of the workpiece 2 has unevenness, the unevenness is expanded into a plane using coordinate transformation as well, thereby creating a distortion-corrected image from the captured image. Next, the overlapping portions in each distortion-corrected image are cut out, and the distortion-corrected images are combined. The misalignment of each of the combined distortion-corrected images is adjusted to create a single composite image. Finally, based on the reference marks marked on the side of the workpiece 2, the composite image is corrected to a planar image of the entire periphery of the side of the workpiece 2 without overlapping portions.

[0041] As described above, the appearance inspection device 1 and the appearance inspection method using the appearance inspection device 1 in this application example make it possible to capture an image of the entire circumference of the side of the workpiece 2 regardless of the orientation of the workpiece 2 on the conveyor belt 3 and without the need to stop the conveyor belt 3 and rotate the workpiece 2. In addition, by combining multiple captured images acquired from each of the cameras 10a-10f, it is possible to acquire a highly accurate planar image of the entire circumference of the side of the workpiece 2 without any overlapping portions.

[0042] [Example] The appearance inspection method and the appearance inspection device 1 according to the embodiment of the present invention will be described in more detail below with reference to the drawings (including the drawings that have been explained in the above application examples). Note that the appearance inspection method and the appearance inspection device 1 according to the present invention are not intended to be limited to the following configurations.

[0043] <Appearance inspection method using an appearance inspection device> Returning to the explanation of FIG. 2, the procedure of the visual inspection method using the visual inspection apparatus 1 according to this embodiment will now be described in detail with reference to FIG. 2. In this flowchart, first, the cameras 10a-10f capture an image of the workpiece 2, including overlapping portions, when the workpiece 2 being transported by the conveyor belt 3 passes a predetermined position, so that the entire periphery of the side of the workpiece 2 is captured comprehensively. Then, the correction unit 110 acquires the captured images from each of the cameras 10a-10f. At this time, the image is captured so that the reference mark marked on the side of the workpiece 2 is captured in at least one of the captured images (S101). Here, S101 corresponds to the captured image acquisition step in the present invention. Next, the correction unit 110 develops the side of the workpiece 2 into a plane by coordinate transformation. If the side of the workpiece 2 has irregularities, the correction unit 110 also performs a plane transformation process to develop the irregularities into a plane by coordinate transformation. This creates a distortion-corrected image in which distortions at both ends of the side of the workpiece 2 in the captured image and distortions caused by the irregularities are eliminated (S102). Here, S102 corresponds to the distortion correction step in the present invention. Next, the composition unit 111 acquires the distortion-corrected images from the correction unit 110, cuts out the overlapping portions of each distortion-corrected image, combines the distortion-corrected images, and adjusts the misalignment of each of the combined distortion-corrected images to create a single composite image (S103). Here, S103 corresponds to the composition step in the present invention. Finally, the correction unit 112 acquires the composite image from the composition unit 111, cuts out the range from a predetermined end of the composite image to the reference mark so that the reference mark is located at the predetermined end, and adds and adjusts the cut-out range to the other end of the composite image opposite the predetermined end, thereby correcting the image to a planar image of the entire periphery of the side surface of the workpiece 2 without overlapping portions (S104). Here, S104 corresponds to the correction step in the present invention.

[0044] FIG. 3 is an explanatory diagram specifically illustrating the steps in the flowchart shown in FIG. 2. In the captured image acquisition step S101, the correction unit 110 acquires captured images 4a-4f from each of the cameras 10a-10f. Here, as described above, the workpiece 2 has a reference mark 21 marked on its side, and the reference mark 21 must appear in at least one of the captured images 4a-4f. Furthermore, the workpiece 2 has irregularities at the top and slightly below the center of its side, and the irregularities slightly below the center of the side have circle, triangle, and square shapes drawn on them. These shapes are distorted because they are drawn along the shape of the irregularities. Shapes are also drawn on parts of the side of the workpiece 2 that do not have irregularities. Note that letters may be written on the side of the workpiece 2 instead of shapes.

[0045] In the distortion correction step S102, the correction unit 110 creates distortion-corrected images 5a-5f from each of the captured images 4a-4f. Because the side of the workpiece 2 has a curved shape, distortion occurs at both ends of the side of the workpiece 2 in the captured images 4a-4f toward the depth of the captured images 4a-4f. Therefore, by developing the side of the workpiece 2 into a plane using coordinate transformation and creating distortion-corrected images 5a-5f from the captured images 4a-4f in which the side of the workpiece 2 has a substantially rectangular shape, the distortion at both ends of the side of the workpiece 2 in the captured images 4a-4f is eliminated. Here, developing the side of the workpiece 2 into a plane in the captured images 4a-4f means stretching the side of the workpiece 2 horizontally in the orientation shown in FIG. 3 in the captured images 4a-4f. At this time, both ends of the side of the workpiece 2, which have a large degree of distortion, are stretched horizontally to a greater extent than the center of the side of the workpiece 2, which has a small degree of distortion. For example, when comparing the captured image 4b ​​and the distortion-corrected image 5b, the reference marks 21 near both ends of the side of the workpiece 2 are stretched horizontally to a large extent, while the star shape near the center of the side of the workpiece 2 is stretched horizontally to a small extent. As a result, the distortion of the reference marks 21 is eliminated in the distortion-corrected image 5b. Similarly, the unevenness of the side of the workpiece 2 is also eliminated by coordinate transformation. As a result, the distortion of the circle, triangle, and square figures drawn along the uneven shape is eliminated in the distortion-corrected images 5a-5f.

[0046] In the combining step S103, the combining unit 111 creates one combined image 6 from the distortion-corrected images 5a-5f, and then creates one combined image 7 from the combined image 6 through a combined image adjustment step (part of the steps in the combining step S103, shown in FIG. 6A). Because the distortion-corrected images 5a-5f each contain overlapping portions, the overlapping portions are cut out and the combined images 5a-5f are combined to create one combined image 6 from the distortion-corrected images 5a-5f. In this case, the area enclosed by two vertical dotted lines in the orientation of FIG. 3 in each of the distortion-corrected images 5a-5f is defined as the area to be combined, and the remaining area (the area from each of the two vertical dotted lines to the edge) is defined as the area to be cut out. In addition, the combined image 6 is created so that the distortion-corrected images 5a-5f (distortion-corrected image 5a in the example of FIG. 3) including the fiducial mark 21 is positioned at the left end in the orientation of FIG. 3. Since there is a misalignment in each of the combined distortion-corrected images 5a-5f, the position of each of the distortion-corrected images 5a-5f is adjusted vertically and horizontally to eliminate the misalignment, and a composite image 7 is created from the combined image 6.

[0047] In the correction step S104, the correction unit 112 corrects the composite image 7 into a planar image 8. The area X from the left edge of the composite image 7 to the reference mark 21 is cut out so that the reference mark 21 is positioned at the left edge in the planar image 8, and the area X is added to the right edge of the composite image 7. By adjusting for misalignment, the image is finally corrected into a planar image 8 of the entire periphery of the side surface of the workpiece 2 without any overlapping portions. Instead of cutting out the area X in the correction step S104, the distortion-corrected image 5a including the reference mark 21 may be positioned at the left edge, and then the distortion-corrected image 5a positioned at the left edge may be added to the right edge, and the entire composite image 7 may be moved or coordinate-converted so that the reference mark 21 is positioned at the left edge. If the reference mark 21 is included in the distortion-corrected image 5f, the distortion-corrected image 5f may be added to the left edge, and the entire composite image 7 may be moved or coordinate-converted so that the reference mark 21 is positioned at the left edge. Alternatively, instead of performing coordinate conversion, the image to the left of the reference mark 21 in the distortion-corrected image 5a positioned at the left edge may be deleted. Furthermore, the image to the right of the reference mark 21 in the distortion-corrected image 5a added to the right edge may be deleted. Here, the "predetermined end" in the present invention refers to the left edge of the composite image 7 and the planar image 8. Furthermore, if the reference mark 21 is located closer to the right edge of the composite image 7 than the left edge, the reference mark 21 may be similarly corrected to be located at the right edge in the planar image 8. Furthermore, if the reference mark 21 is located in two locations, near the left and right edges of the composite image 7 (for example, it is conceivable that the reference mark 21 appears in the captured image 4a and the captured image 4f, and the combined image 6 was created without cutting out the range in which the reference mark 21 appears from each of the distortion-corrected images 5a and 5f), the range X may be similarly cut out, and then the range from the right edge to the reference mark 21 closest to the right edge may also be cut out from the composite image 7 to correct it to the planar image 8. Furthermore, as long as the reference position for correcting the composite image 7 to the planar image 8 is clear, the reference mark 21 does not need to be marked on the side of the workpiece 2. The reference mark 21 corresponds to the predetermined reference position in the present invention.

[0048] Here, a supplementary explanation will be given of the procedure for creating the planar image 8 from the captured images 4a-4f shown in FIG. 3 using FIG. 4. Since the orientation of the multiple workpieces 2 on the conveyor belt 3 is not constant during conveyance, the reference mark 21 marked on the side of the workpiece 2 can be captured by any of the cameras 10a-10f, but it is not clear which camera 10 can capture the reference mark 21. As an example, captured images 4 in patterns 1 to 4 that show the same reference mark 21 as the reference mark 21 in the planar image 8 (i.e., the reference mark 21 that is not cut out from the distortion-corrected image 5 in the synthesis step S103) are shown enclosed in a square. In each of patterns 1 to 4, the captured images 4 enclosed in a square are different, that is, the cameras 10 that captured the reference mark 21 are different. However, regardless of which camera 10 is used to capture the reference mark 21, in the correction step S104, The composite image 7 is corrected to a planar image 8 in which the reference mark 21 is positioned at the left end, so that the same planar image 8 is always acquired. Because the same planar image 8 is always acquired regardless of the orientation of the workpiece 2 on the conveyor belt 3, it is easy to compare differences in the positions of stains and scratches when, for example, multiple planar images 8 are lined up and visually inspected, improving the accuracy of the appearance inspection.

[0049] FIG. 5 is a flowchart illustrating the distortion correction step S102 shown in FIG. 2 in more detail. FIGS. 6A and 6B are explanatory diagrams illustrating an example of the content displayed on the display unit 121 of the UI 12 in the distortion correction step S102 shown in FIG. 2. Hereinafter, the distortion correction step S102 will be described in detail with reference to FIGS. 6A and 6B using FIG. 5. The input unit 122 is not shown. In this flowchart, first, the input unit 122 selects one of the captured images 4a-4f acquired by the correction unit 110, and the selected captured image 4a (hereinafter, the captured image 4a will be illustrated as an example, but may be replaced with another captured image 4) is displayed on the display unit 121 (S1021). The image displayed on the display unit 121 can also be converted to a monochrome image. Here, S1021 corresponds to the captured image display step in the present invention.

[0050] Next, the input unit 122 is used to select whether to set the outline of the workpiece 2 in the captured image 4a manually or automatically. In the visual inspection device 1, manual setting is possible when only unevenness reduction processing is performed, and automatic setting of the outline of the workpiece 2 is possible when edge detection is performed to perform unevenness reduction processing. The unevenness reduction processing is a process in which the uneven shape of the side surface of the workpiece 2 in the captured image 4a is expanded onto a plane by coordinate transformation to reduce the influence of distortion due to the uneven shape. When manually setting, the horizontal length (hereinafter referred to as the "X direction") and vertical length (hereinafter referred to as the "Y direction") of the outline of the workpiece 2 on the display unit 121 are set in the input unit 122. Based on the captured image 4a and the length settings, the correction unit 110 calculates a grid-like frame image 9 in which the outline of the workpiece 2 is divided by multiple grid lines in the X direction and the Y direction. As shown in FIG. 6A, the display unit 121 displays a grid-shaped frame image 9 superimposed on the workpiece 2 in the captured image 4a displayed in the captured image display step S1021. At the same time, a line representing the center of the grid-shaped frame image 9 in the X direction is also displayed. Note that in FIG. 6A, the grid-shaped frame image 9 is shown with a dashed line to distinguish it from the line representing the center of the grid-shaped frame image 9 in the X direction and the line representing the elevation angle in the Y direction, but it may also be displayed with a solid line. The line representing the elevation angle in the Y direction is a line representing the relative positional relationship in the height direction between the camera 10a and the workpiece 2. For example, if the line representing the elevation angle in the Y direction is displayed below a predetermined position in the captured image 4a of the workpiece 2, it indicates that the camera 10a is positioned so as to look down on the workpiece 2. Conversely, if the line representing the elevation angle in the Y direction is displayed above a predetermined position in the captured image 4a of the workpiece 2, it indicates that the camera 10a is positioned so as to look up on the workpiece 2. Furthermore, when setting automatically using edge coordinates, necessary measurement items are set in the input unit 122, and the contour of the workpiece 2 is calculated by edge measurement. Examples of measurement items include the number of sampling points and tolerance width. In this embodiment, the number of sampling points is the number of squares in the Y direction in the grid-like frame image 9, and the number of points for edge detection determined in advance is divided by the number of squares in the Y direction (number of groups).For example, if the number of points for edge detection is predetermined to be 100 and the number of groups is 5, edges are detected using 20 points per group. If the average edge position of each group, set by the number of sampling points, exceeds the allowable width, the edge is excluded from the target of edge detection. The display unit 121 displays a grid-like frame image 9 based on the results of this edge measurement. An example of the content displayed by the display unit 121 is shown in FIG. 6A (S1022). Note that the display position of the grid lines in the Y direction and the thickness of the grid lines in the grid-like frame image 9 can be set in the input unit 122, and the display unit 121 can display the grid-like frame image 9 reflecting the setting. Here, S1022 corresponds to the correction range display step in this invention. Furthermore, the contour corresponds to the edge shape in this invention.

[0051] 6C shows an enlarged view of the shape of the end of the side surface of the workpiece 2 in the captured image 4a shown in FIG. 6A. FIG. 6C is a diagram for explaining the shape of the end of the side surface of the workpiece 2, and figures drawn on the side surface of the workpiece 2 are omitted. If the side surface of the workpiece 2 has irregularities, the shape of the irregularities at the end of the side surface of the workpiece 2 can be confirmed on the display unit 121 as shown in FIG. 6C. Whether the outline of the workpiece 2 in the captured image 4a is set manually or automatically, the shape of the irregularities is detected based on the set outline, and when creating the distortion-corrected image 5a shown in FIG. 6B from the captured image 4a, this irregularity is developed onto a plane.

[0052] Next, parameters for calculating the amount of distortion correction for the workpiece 2 displayed with the grid-like frame image 9 superimposed thereon in the correction range display step S1022 are set in the input unit 122. Examples of parameters include the distance between the camera 10a and the workpiece 2 (below, the camera 10a is exemplified corresponding to the captured image 4a, but it may be replaced with another camera 10), the diameter of the top surface of the workpiece 2, and the inclination of the workpiece 2 relative to the camera 10a (S1023). Note that since the workpiece 2 may be inclined in the X, Y, and Z directions relative to the camera 10a, it is necessary to consider these three directions when determining the inclination of the workpiece 2 relative to the camera 10a. Conversely, the inclination of the camera 10a relative to the workpiece 2 may also be considered. Here, S1023 corresponds to the parameter setting step in the present invention.

[0053] Based on the parameters set in the input unit 122 in the parameter setting step S1023, the correction unit 110 performs coordinate transformation to develop the side surface of the workpiece 2 into a plane, thereby creating a distortion-corrected image 5a from the captured image 4a. Then, as shown in FIG. 6B, the display unit 121 displays a lattice-shaped frame image 9 developed into a plane, superimposed on the distortion-corrected image 5a. Regarding the lattice-shaped frame image 9, the X-direction spacing of the grid lines in the captured image 4a shown in FIG. 6A (dx in FIG. 6A) is nonuniform. Specifically, the X-direction spacing of the grid lines narrows from the center toward both ends of the side surface of the workpiece 2 in the captured image 4a. During coordinate transformation, the X-direction spacing of the grid lines near both ends of the side surface of the workpiece 2 is stretched to a greater extent, while the X-direction spacing of the grid lines near the center is stretched to a smaller extent. As a result, the X-direction spacing of the grid lines in the distortion-corrected image 5a shown in FIG. 6B (dx' in FIG. 6B) becomes uniform. Similarly, for other captured images 5, the captured image display step S1021, the correction range display step S1022, and the parameter setting step S1023 are applied to create distortion-corrected images 5.

[0054] FIG. 7 is a flowchart showing the flow of the combining step S103 shown in FIG. 2 in more detail. FIGS. 8A and 8B are explanatory diagrams showing an example of the content displayed on the display unit 121 of the UI 12 in the combining step S103 shown in FIG. 2. Hereinafter, the flow of the combining step S103 will be described in detail using FIG. 7 and with reference to FIGS. 8A and 8B. Note that the input unit 122 is not shown. In this flowchart, first, the number of distortion-corrected images 5 to be combined is set in the input unit 122 (S1031). Note that a maximum of eight images can be set. Here, S1031 corresponds to the image number setting step in the present invention.

[0055] Next, the input unit 122 selects one of the distortion-corrected images 5a-5f acquired by the composition unit 111, and the display unit 121 displays the selected distortion-corrected image 5a (the distortion-corrected image 5a will be exemplified below, but it may be replaced with another distortion-corrected image 5). Furthermore, a composition range in the X direction is set in the input unit 122, and the display unit 121 displays the composition range in the X direction with a dotted line (it may be a solid line or a dash-dot line) as shown in FIG. 8A. The composition unit 111 cuts out an area outside the composition range in the X direction from the distortion-corrected image 5a (S1032). Note that instead of setting a composition range in the X direction individually for each of the distortion-corrected images 5a-5f, a common composition range in the X direction may be set for all of the distortion-corrected images 5a-5f. Here, S1032 corresponds to the composition range setting step in the present invention. The composition unit 111 cuts out the distortion-corrected image 5a by using a dotted line (it may be a solid line or a dash-dot line) as shown in FIG. 8A. The distortion of the synthesis range in the X direction in the normal image 5a is expanded onto a plane by coordinate transformation and adjusted (S1033). Note that here too, the distortion of the synthesis range in the X direction may be adjusted commonly for all of the distortion-corrected images 5a-5f. Here, S1033 corresponds to the distortion adjustment step in this invention.

[0056] Next, the combining unit 111 combines all of the distortion-corrected images 5a-5f, which have had their distortion adjusted within the combined range in the X direction, and the display unit 121 displays the combined image 6 as shown in FIG. 8B. At this time, the order of the distortion-corrected images 5a-5f to be combined and whether or not to combine them by overlapping are set in the input unit 122 (S1034). Here, overlapping refers to the process of complementing and combining the overlapping portions so that the entire circumference of the side surface of the workpiece 2 is captured when the combined image 7 is corrected into the planar image 8 in the correction step S104 shown in FIG. 2. Here, S1034 corresponds to the combining step in this invention.

[0057] The combined portions of the distortion-corrected images 5 in the combined image 6 often have misalignment in the X and Y directions. The combining unit 111 adjusts each of the distortion-corrected images 5 in the X and Y directions to eliminate the misalignment, and the display unit 121 displays the combined image 7 as shown in FIG. 3. To adjust the range of misalignment, the display unit 121 can display two parallel solid lines in the X direction (which may be dotted or dashed lines) superimposed on the combined portions of the combined image 6, as shown in FIG. 8B. The misalignment can be adjusted within the ranges of these two parallel solid lines in the X and Y directions. The range of misalignment adjustment may be set individually for each combined portion in the input unit 122 or may be set commonly for all combined portions. When adjusting the misalignment, the input unit 122 is used to set, for example, the brightness range for which misalignment is to be adjusted and the pixel range within which misalignment is allowed. Furthermore, if the magnifications of the distortion-corrected images 5 in the combined image 6 are different, the combining unit 111 adjusts each magnification to a reference magnification, thereby obtaining a combined image 6 in which the magnification is uniform in all areas (S1035). Here, S1035 corresponds to the combined image adjustment step in this invention. After the combined image 7 is created from the combined image 6, the display unit 121 displays the combined image 7.

[0058] In this embodiment, the UI 12 may also include cameras 10a-10f.

[0059] <Appendix 1> A visual inspection method for inspecting the side surface of a cylindrical body (2), comprising: an image acquisition step (S101) of acquiring images (4a-4f) of the side surface of the cylindrical body from different circumferential directions using a plurality of image capture devices (10a-10f); a distortion correction step (S102) for performing a plane transformation process in which an image of the side surface of the cylinder in each of the captured images is expanded onto a plane by coordinate transformation to create distortion-corrected images (5a-5f); An appearance inspection method characterized in that, in the distortion correction process, if unevenness exists on the side surface of the cylindrical body, an unevenness reduction process is further performed to reduce distortion in the image of the side surface of the cylindrical body caused by the unevenness based on the edge shape in the image of the side surface of the cylindrical body.

[0060] <Appendix 2> a synthesis step (S103) of cutting out overlapping portions of distortion-corrected images (5a-5f) created from a plurality of captured images (4a-4f) of the side surface of the cylindrical body (2) and synthesizing the distortion-corrected images from which the overlapping portions have been cut out to create one synthetic image (7); A visual inspection method comprising: a correction process (S104) for correcting the composite image of the image of the side surface of the cylinder so that a predetermined reference position (21) is positioned at one end of the composite image.

[0061] <Appendix 3> A visual inspection device (1) for inspecting the visual appearance of a side surface of a cylindrical body (2), a plurality of imaging devices (10a-10f) installed to capture images of the side surface of the cylindrical body from different directions in the circumferential direction; a correction unit (110) that acquires a plurality of captured images (4a-4f) from each of the plurality of imaging devices, and performs a plane transformation process to develop an image of the side surface of the cylinder in each of the captured images onto a plane by coordinate transformation, thereby creating distortion-corrected images (5a-5f); The visual inspection device (1) is characterized in that, when unevenness exists on the side surface of the cylindrical body, the correction unit reduces distortion of the image of the side surface of the cylindrical body caused by the unevenness based on the edge shape in the image of the side surface of the cylindrical body.

[0062] <Appendix 4> a synthesis unit (111) that cuts out overlapping portions of distortion-corrected images (5a-5f) created from a plurality of captured images (4a-4f) of the side surface of the cylindrical body (2) and synthesizes the distortion-corrected images from which the overlapping portions have been cut out to create one synthesized image (7); and a correction unit (112) that performs correction processing on the composite image of the image of the side surface of the cylinder so that a predetermined reference position (21) is positioned at one end of the composite image. [Explanation of symbols]

[0063] 1: Visual inspection equipment 10a-10f: Camera 11: Arithmetic section 110: Correction unit 111: Synthesis section 112: Correction section 12:UI 121: Display section 122: Input section 2: Work 21: Reference mark 3: Conveyor belt 4a-4f: Captured images 5a-5f: Distortion corrected images 6: Combined image 7: Composite image 8: Planar image 9: Grid frame image

Claims

1. A visual inspection method for inspecting the visual appearance of a side surface of a cylindrical body, comprising: an image acquisition step of acquiring a plurality of images by using a plurality of imaging devices to capture images of the side surface of the cylindrical body from different circumferential directions; a distortion correction step of performing a plane transformation process of developing an image of the side surface of the cylindrical body in each of the captured images onto a plane by coordinate transformation to create a distortion-corrected image, An appearance inspection method characterized in that, in the distortion correction process, if unevenness exists on the side surface of the cylindrical body, an unevenness reduction process is further performed to reduce distortion in the image of the side surface of the cylindrical body caused by the unevenness based on the edge shape in the image of the side surface of the cylindrical body.

2. a combining step of cutting out overlapping portions of each of the plurality of distortion-corrected images created from the captured image, and combining the plurality of distortion-corrected images from which the overlapping portions have been cut out to create one combined image; 2. The visual inspection method according to claim 1, further comprising a correction step of performing a correction process on the composite image of the image of the side surface of the cylinder so that a predetermined reference position is located at one end of the composite image.

3. 3. The visual inspection method according to claim 2, wherein the reference position is the position of a reference mark previously provided on the side surface of the cylindrical body.

4. The distortion correction step includes: a captured image display step of displaying the selected captured image; a correction range display step of displaying a lattice-shaped frame image superimposed on the cylindrical body in the captured image displayed in the captured image display step; a parameter setting step of setting parameters for calculating an amount of distortion correction of the cylindrical body on which the lattice-shaped frame image is superimposed and displayed in the correction range display step, Based on the parameters set in the parameter setting step, each of the captured images is adjusted to a predetermined value so that the intervals of the grid lines in the grid-shaped frame image in the X direction are uniform.

4. The visual inspection method according to claim 2, wherein the distortion is corrected to the distortion-corrected image and displayed.

5. 5. The visual inspection method according to claim 4, wherein in the correction range display step, the grid-shaped frame image is displayed based on the X-direction length and the Y-direction length of the edge shape of the grid-shaped frame image that are set manually or automatically.

6. 6. The appearance inspection method according to claim 4 or 5, characterized in that in the parameter setting step, the parameters include at least one of the distance between one of the plurality of imaging devices and the cylinder, the diameter of the top surface of the cylinder, or the inclination of the cylinder relative to the one imaging device.

7. The synthesis step comprises: an image number setting step for setting the number of the distortion-corrected images to be synthesized; a synthesis range setting step of setting a synthesis range by cutting out overlapping portions of the distortion-corrected images for the number of distortion-corrected images set in the image number setting step; a distortion adjustment step of expanding the distortion of the range to be combined set in the combination range setting step onto a plane by coordinate transformation and adjusting the distortion; a combining step of combining the distortion-corrected images adjusted in the distortion adjusting step to create a combined image and displaying the combined image; and a combined image adjustment step of adjusting the misalignment of each of the distortion-corrected images in the combining step in the X direction and / or the Y direction to create and display the composite image.

8. 8. The appearance inspection method according to claim 7, wherein in the combined image adjustment step, a range of shading or brightness to be adjusted for the misalignment and a range of pixels that constitutes an acceptable range for the misalignment are set.

9. 9. The visual inspection method according to claim 7, wherein in said combined image adjusting step, a magnification of each of said distortion-corrected images is adjusted to a reference magnification.

10. A visual inspection device for inspecting the visual appearance of a side surface of a cylindrical body, a plurality of imaging devices installed to capture images of the side surface of the cylindrical body from different directions in the circumferential direction; a correction unit that acquires a plurality of captured images from each of the plurality of image capture devices, and performs a plane transformation process to develop an image of the side surface of the cylinder in each of the captured images onto a plane by coordinate transformation, thereby creating a distortion-corrected image; The visual inspection device is characterized in that, when unevenness is present on the side of the cylindrical body, the correction unit reduces distortion in the image of the side of the cylindrical body caused by the unevenness based on the edge shape in the image of the side of the cylindrical body.

11. a synthesis unit that cuts out overlapping portions of each of the plurality of distortion-corrected images created from the captured image, and synthesizes the plurality of distortion-corrected images from which the overlapping portions have been cut out, to create one synthetic image; 11. The visual inspection device according to claim 10, further comprising: a correction unit that performs a correction process on the composite image of the images of the side surface of the cylindrical body so that a predetermined reference position is positioned at one end of the composite image.

12. The reference position is preferably the position of a reference mark previously provided on the side surface of the cylindrical body. The visual inspection apparatus according to claim 11,

13. a display unit that displays the captured images acquired from each of the plurality of image capture devices and a lattice-shaped frame image superimposed on the cylindrical body in the captured images; an input unit for setting parameters for calculating the amount of distortion correction of the cylindrical body on which the grid-shaped frame image is displayed superimposed, the correction unit corrects each of the captured images to the distortion-corrected image based on the parameters set in the input unit so that intervals of grid lines in the grid-shaped frame image in the X direction become uniform; 13. The visual inspection apparatus according to claim 11, wherein the display unit displays the distortion-corrected image.

14. 14. The visual inspection device according to claim 13, wherein the display unit displays the grid-shaped frame image based on the X-direction length and the Y-direction length of the edge shape of the grid-shaped frame image that are manually or automatically set in the input unit.

15. 15. The visual inspection device according to claim 13, wherein the parameters set in the input unit include at least one of the distance between one of the plurality of image sensors and the cylinder, the diameter of the top surface of the cylinder, or the inclination of the cylinder relative to the one image sensor.

16. the input unit to set the number of the distortion-corrected images to be combined and the range to be combined by cutting out overlapping portions of the distortion-corrected images for the number of the distortion-corrected images; the combining unit adjusts the distortion of the range to be combined set by the input unit by expanding it onto a plane through coordinate transformation, combines the adjusted distortion-corrected images to create a combined image, and adjusts the misalignment of each of the distortion-corrected images in the combined image in the X direction and / or the Y direction to create the combined image; 15. The visual inspection apparatus according to claim 14, wherein the display unit displays the combined image and then displays the composite image.

17. 17. The visual inspection device according to claim 16, wherein the synthesis unit creates the composite image by setting, in the input unit, a range of shading or brightness to be adjusted for the misalignment and a range of pixels that is an acceptable range for the misalignment.

18. 18. The visual inspection apparatus according to claim 16, wherein the combining unit adjusts the magnification of each of the distortion-corrected images to a reference magnification.

Images