Imaging device, surface inspection device, and surface inspection method

Abstract

To provide an imaging device, a surface inspection device, and a surface inspection method capable of generating images required for inspection with a smaller number of times of imaging even in the case of an inspected object having a complex shape.SOLUTION: An imaging device 100 used for a surface inspection device 300 for inspecting a surface state of an inspected object 10 including a mirror surface section includes: multiple pieces of planar or concave lighting 20 that are disposed so as to surround the periphery of the inspected object 10 and project stripe-shaped images to the inspected object 10; and an imaging section 30 that is disposed in a predetermined position relative to the inspected object 10 and images an inspected object to which stripe-shaped images are projected. The surface inspection device 300 further includes an inspection image generation section 200 and processes images imaged by the imaging device 100 and generates inspection images.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an imaging device that images an object to be inspected, the surface of which has specular reflection properties, and a surface inspection device and a surface inspection method that inspect the surface condition of the object to be inspected using the imaging device. [Background technology]

[0002] The following patents are disclosed regarding a surface inspection device that can project a fringe image onto an object having a specular reflection surface, capture the image, and use the captured fringe image to inspect the surface condition of the object. Patent Document 1 (JP 2018-059883 A) discloses a surface inspection device that can inspect the surface condition of a curved portion of an object to be inspected, even if the object has a mirror surface and a three-dimensional shape with a curved portion. The surface inspection device described in Patent Document 1 is a surface inspection device that inspects the surface condition of a three-dimensional object having a mirror surface and a bent portion, and includes an illumination unit that reflects a stripe pattern of light onto the bent portion, an illumination movement unit that moves the illumination to multiple positions relative to the bent portion, an imaging unit that is arranged at a predetermined position relative to the bent portion and images the bent portion into which the stripe pattern is reflected each time the illumination is moved to multiple positions, a calculation unit that differentially processes each of the multiple images captured by the imaging unit and adds together the multiple images after differential processing, and an inspection unit that inspects for defects in the stripe pattern based on the stripe pattern in the image after addition by the calculation unit, and is characterized in that, when the illumination movement unit moves the illumination to multiple positions, the illumination unit respectively positions the illumination units so that the brightness of the stripe pattern other than the defective portion reflected in the bent portion is averaged by adding together the differential images of the stripe pattern.

[0003] Patent Document 2 (JP Patent Publication 08-086634 A) discloses a surface defect inspection device that can detect defects over a wide range within a single screen and can perform more precise defect detection without misdetecting extremely slight irregularities such as the skin of an orange as a defect. The surface defect inspection device described in Patent Document 2 is a surface defect inspection device that irradiates light onto a surface to be inspected, creates a light-receiving image based on the light reflected from the surface to be inspected, and detects defects on the surface to be inspected based on this light-receiving image, and is characterized by comprising: an illumination means for projecting a predetermined light and dark pattern onto the surface to be inspected; an imaging means for converting the light-receiving image obtained by imaging the surface to be inspected into image data of an electrical signal; a boundary area identification means for identifying a boundary area between light and dark areas in the low frequency range of frequency components in the image data; an image enhancement means for extracting only areas in the high frequency range of frequency components in the image data that have a level equal to or higher than a predetermined value; and a defect detection means for detecting, from the areas extracted by the image enhancement means, those parts that are not the boundary areas identified by the boundary area identification means as defects.

[0004] Patent document 3 (JP 2021-056183 A) discloses a workpiece surface defect detection device that can stably detect small surface defects with high accuracy. The surface defect detection device described in Patent Document 3 is characterized by comprising: an image acquisition means for acquiring multiple images of a measured portion of a workpiece while a light and dark pattern generated by a lighting device is moved relative to the workpiece, which is the target for surface defect detection; a feature point extraction means for extracting feature points of the image by applying a binarization process and a threshold value or by applying a corner detection function to each image acquired by the image acquisition means; a tentative defect candidate extraction means for extracting tentative defect candidates by determining multidimensional feature amounts for each feature point extracted by the feature point extraction means; a defect candidate determination means for determining the tentative defect candidate as a defect candidate if there are a predetermined threshold or more of images corresponding to the tentative defect candidates among the multiple images from which the tentative defect candidates are extracted by the tentative defect candidate extraction means; an image synthesis means for creating a synthetic image by synthesizing a plurality of images including the defect candidates determined by the defect candidate determination means; and a detection means for detecting defects based on the synthetic image created by the image synthesis means.

[0005] Patent Document 4 (JP 2011-179982 A) discloses a surface inspection device that has a simple structure and is capable of inspecting surface defects such as surface scratches, peeling paint, and dents quickly, with high accuracy, and at low cost, even on measurement objects that have a high surface reflection, such as automobile bodies and their parts, due to them being coated with a glossy paint. The surface inspection device described in Patent Document 4 includes a measurement environment configuring device that configures a measurement space having curved walls formed from a translucent material, an illumination device that uniformly dims and fully irradiates a measurement object in the measurement space with light from a light source provided outside the curved wall, which passes through the curved wall and is fully irradiated onto the measurement object, a pattern light projection device that projects and reflects pattern light onto the curved wall so that it does not directly hit the measurement object, and projects this reflected pattern light (hereinafter referred to as "reflected pattern light") onto the measurement object, an imaging device that images the measurement object while remaining stationary relative to the measurement object, and which captures a total illumination image of the measurement object fully irradiated by the illumination device and a reflected pattern image of the measurement object onto which the reflected pattern light is projected, and a data processing device that detects surface defects of the measurement object from the total illumination image and the reflected pattern image.

[0006] Patent Document 5 (JP 2020-134491 A) discloses an inspection unit that can accurately detect defects even by people who are not skilled in inspection. The inspection unit described in Patent Document 5 is an inspection unit for detecting defects on a target surface, the inspection unit comprising a projection device and a photographing device, the projection device being capable of projecting a projection image onto the target surface by shifting it along a shift direction, the photographing device being capable of photographing the target surface, the projection image including one or more bright areas and one or more dark areas having a lower brightness than the bright areas, the projection image being projected onto the target surface by shifting it one or more times along the shift direction, thereby enabling the projection of bright areas and dark areas at all positions on the target surface, the inspection unit being capable of performing an inspection process and an inspection preparation process, in which the inspection unit projects the projection image onto the target surface by using the projection device while shifting it one or more times along the shift direction and photographs the target surface by using the photographing device, thereby detecting defects, and in the inspection preparation process, the inspection unit projects each of the bright areas and the dark areas one or more times onto at least one predetermined position on the target surface by using the projection device, and photographs two or more images by the photographing device.

[0007] Patent Document 6 (JP Patent Publication No. 2010-085165) discloses a surface inspection device that solves the problem that when detecting uneven defects on the specular surface of an inspected object, the positional relationship of the inspected surface relative to the light irradiation means and imaging means changes over time, causing the captured image to change successively, making it impossible to accurately detect uneven defects. The surface inspection device described in Patent Document 6 is equipped with a light irradiation means for irradiating an object under inspection with light of a light and dark pattern, an imaging means for imaging the light and dark pattern reflected by the object under inspection, and a data processing means for inspecting the surface of the object under inspection based on the captured image including the light and dark pattern captured by the imaging means, wherein the data processing means is characterized by comprising a boundary detection means for detecting boundary points between light and dark areas of the light and dark pattern from areas in the captured image where the light and dark pattern irradiated from the light irradiation means is reflected by the surface of the object under inspection, a boundary master creation means for creating a master of the boundary points of the light and dark pattern from the boundary points, and a defect detection means for detecting defects in the object under inspection by comparing the boundary lines of the light and dark pattern in the captured image with the boundary lines of the master light and dark pattern. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-059883 A [Patent Document 2] Japanese Patent Application Publication No. 08-086634 [Patent Document 3] JP 2021-056183 A [Patent Document 4] JP 2011-179982 A [Patent Document 5] JP 2020-134491 A [Patent Document 6] JP 2010-085165 A Summary of the Invention [Problem to be solved by the invention]

[0009] Conventionally, for objects with mirror-like surfaces, a method has been used in which a fringe image is projected onto the mirror-like surface, then imaged to generate an inspection image. However, when the shape is complex, the area onto which the fringe image is projected is narrow, and the area that can be combined by imaging at the same imaging position is limited. This means that it becomes necessary to project and image the fringe image individually at more locations, which increases the number of imaging attempts and ultimately results in longer inspection times.

[0010] The surface inspection device described in Patent Document 1 inspects for defects in curved parts with mirror-like surfaces by projecting a striped pattern of light onto the curved parts. However, the surface inspection device of Patent Document 1 has a problem that the area onto which the striped pattern of light is projected is narrow because the illumination is a single plane, and furthermore, the illumination must be moved to change the area onto which the striped pattern of light is projected, which results in longer inspection times.

[0011] In the surface defect inspection device described in Patent Document 2, a plurality of illumination devices are provided to expand the area in which a predetermined light and dark pattern is projected. However, as shown in FIG. 26, the illumination devices in Patent Document 2 are configured to project the same light and dark pattern onto the surface to be inspected from the plurality of illumination devices. This is because the objects to be inspected in the surface defect inspection device of Patent Document 2 are mainly automobile bodies, and the curve of the shape along the longitudinal direction of the light and dark pattern is large. However, in the case of an object to be inspected having a more complicated shape, for example, a mirror surface that is curved both in the longitudinal direction of the light and dark pattern and in a direction perpendicular to the longitudinal direction, there is a problem that the shape in the direction perpendicular to the longitudinal direction cannot be accurately synthesized.

[0012] The surface defect detection device described in Patent Document 3 is an invention characterized mainly by the creation of a composite image and the detection of defects using the created composite image. Patent Document 3 also has a linear light attached to surround the peripheral surface of the workpiece except for the bottom surface, and is configured to diffusely illuminate the workpiece with illumination light in a light and dark stripe pattern consisting of illumination and non-illumination that alternate in the movement direction of the workpiece. Therefore, defects in the direction perpendicular to the movement direction of the workpiece (movement direction of the stripe image) may be difficult to find as defects.

[0013] In the surface inspection device described in Patent Document 4, "highlights are formed in the areas that are specularly reflected to the observation camera, and the pattern light is reflected very strongly. Conversely, the intensity of the reflected light is extremely weak compared to the highlights in areas other than the specular reflection, making it difficult to capture the reflection pattern required for three-dimensional information measurement." In order to address this issue, the light source light is uniformly dimmed for illumination, and the pattern light is projected and reflected on a curved wall so as not to directly hit the measurement object, and this reflected pattern light (reflected pattern light) is projected on the measurement object. In this case, the difference in intensity between the specularly reflected area and the areas other than the specularly reflected area is small. Therefore, even if the light source is a light source such as a liquid crystal display, the difference in intensity between the specularly reflected area and the areas other than the specularly reflected area is small, and the above issue can be resolved. However, even if the light beam from the pattern light projection device is reflected on a curved wall with a partially curved surface such as a dome or tunnel shape, the incident direction of the pattern light is limited, as can be seen from FIG. 1, and the pattern light cannot be projected on all necessary areas of a three-dimensional inspection object with multiple bends.

[0014] The inspection unit described in Patent Document 5 is characterized in that it obtains contrast, which is the difference between the maximum brightness and the minimum brightness, from two or more images captured by an imaging device, and that the processing device obtains the dark area width in the inspection process based on the contrast obtained by the dark area width adjustment process in the projection preparation process. However, this inspection unit has only one projection device and can only project from one direction, so it cannot project light and dark areas onto all of the target surfaces of objects with more complex shapes.

[0015] The surface inspection device described in Patent Document 6 is intended primarily for inspection of objects with simple shapes, such as cylindrical plastic film rolls, and has only one light irradiation means that can project from only one direction; therefore, it is not possible to project light and dark areas onto all of the target surfaces of objects with more complex shapes.

[0016] The main object of the present invention is to provide an imaging device that, when an inspection image is generated by projecting a fringe image onto an inspection object that includes a mirror surface and capturing the image to generate an inspection image, can project a fringe image onto the inspection object from a wider range of directions to generate the image required for inspection with fewer images even for inspection objects with complex shapes, and a surface inspection device and method using the imaging device. Another object of the present invention is to provide an imaging device that can generate more accurate inspection images for required locations by projecting a finer stripe image onto a portion of an object to be inspected, and a surface inspection device and surface inspection method that use the imaging device. [Means for solving the problem]

[0017] (1) An imaging device according to one aspect is an imaging device used in a surface inspection device that inspects the surface condition of an object to be inspected, including a mirror portion, and includes a plurality of planar or concave-shaped illuminators that are arranged to surround the periphery of the object to be inspected and project a stripe image onto the object to be inspected, and an imaging unit that is arranged at a predetermined position relative to the object to be inspected and images the object to which the stripe image is projected.

[0018] Conventionally, when inspecting the surface condition of a mirror-like object, a method has been used in which a fringe image is projected and captured to generate an inspection image. However, when the shape is complex, the area onto which the fringe image is projected is narrow, and the area where an inspection image can be generated by capturing an image at the same capturing position is limited. This means that it becomes necessary to capture fringe images individually at more capturing positions, which increases the number of captures and results in longer inspection times. In an imaging device according to one aspect, a plurality of flat or concave shaped illuminations are arranged to surround the periphery of an object to be inspected, and a stripe image is projected from each illumination, so that even if the object to be inspected has a complex shape having a plurality of bends, the stripe image can be projected onto a wider range of the surface of the object to be inspected. This makes it possible to expand the range of inspection images that can be generated by imaging at the same imaging position, reduce the number of imaging operations, and shorten the inspection time. In particular, by using a concave illumination, it is possible to project a fringe image onto the object to be inspected from a wider range of angles.

[0019] (2) The imaging device according to the second aspect of the present invention may be configured such that, in the imaging device according to one aspect, the stripe images projected onto the object to be inspected by the multiple illuminations are different for each illumination, and the imaging unit captures an image that is a composite of the multiple stripe images projected by the multiple illuminations.

[0020] Taking an image using multiple illuminations is also described in, for example, Patent Documents 2 and 3, but in the inventions described in Patent Documents 2 and 3, the same stripe image is irradiated onto the object to be inspected using multiple illuminations (see FIG. 26 of Patent Document 2). This is because the object to be inspected in Patent Documents 2 and 3 is an automobile body, and the curved surface is formed mainly in the direction of the stripes in FIG. 26. However, in the case of an object to be inspected with a more complicated shape, the curved surface is not necessarily formed in one direction. Alternatively, the radius of curvature of the curved surface may differ depending on the direction. In such a case, by irradiating the object to be inspected with stripe patterns with different directions and / or stripe intervals from each of the multiple illuminations and capturing an image composed of the multiple stripe images, an accurate inspection image can be generated even when the curved surface is formed in multiple directions or when the radius of curvature of the curved surface differs depending on the direction.

[0021] (3) The imaging device according to a third aspect of the present invention may be an imaging device according to one aspect, further comprising one or more flat or concave mirrors that reflect light from the illumination, wherein a fringe image reflected by the mirror is projected onto the object to be inspected, and the imaging unit captures a composite image of the multiple fringe images projected by the multiple illuminations and the mirrors.

[0022] When arranging the lighting so as to surround the periphery of the inspection object, it is difficult to arrange the lighting in the direction in which the imaging unit is arranged or in the direction of the holding unit that holds the inspection object. In such a case, a flat or concave mirror is arranged in the direction in which it is difficult to arrange the lighting, and the fringe image of the lighting is reflected by the mirror and projected onto the inspection object, so that the fringe image can be projected from a wider range of angles. In addition, by projecting the fringe image from the lighting and the mirror, multiple fringe images with different directions and intervals are projected onto the inspection object, and a more accurate inspection image can be generated by capturing an image composed of the multiple fringe images. In particular, by configuring the illumination using a concave mirror, it is possible to project a fringe image onto the object to be inspected from a wider range of angles.

[0023] (4) An imaging device according to a fourth aspect of the present invention is the imaging device according to the third aspect of the present invention, wherein one of the mirrors is disposed on the imaging unit side.

[0024] In this case, by arranging a mirror on the imaging unit side, a fringe image can be reliably projected onto the portion of the image of the object to be inspected that faces the imaging unit, and an accurate inspection image can be generated for this portion.

[0025] (5) An imaging device according to a fifth aspect of the present invention is the imaging device according to the fourth aspect of the present invention, wherein the mirror is a parabolic mirror, and the imaging section is disposed at the center of the mirror.

[0026] A parabolic mirror has the property that when parallel light rays are incident on it, the incident parallel light rays are focused at the focal point of the parabolic mirror. Therefore, when an object to be inspected is placed near the focal point of the parabolic mirror and a stripe image with nearly parallel light rays is projected from the side facing the parabolic mirror, a stripe image with narrow spacing can be projected onto the object to be inspected. Then, by capturing an image of the object to be inspected onto which this narrow-spaced stripe image is projected, a more accurate inspection image can be generated. Furthermore, by locating the imaging section at the center of the mirror, fringe images can be projected symmetrically from above, below, left and right of the parabolic mirror, making it possible to generate fringe images with little distortion on the object to be inspected.

[0027] (6) The imaging device of the sixth invention is the imaging device of the third invention, in which, when the surface of the object to be inspected facing the imaging unit is defined as the front surface, lighting or mirrors may be arranged in all directions of the object to be inspected, including the front, rear, right, left, upward, and downward directions.

[0028] In this case, since the stripe image is projected from all directions, the stripe image is reflected in all parts of the image of the object to be inspected captured by the imaging unit, and therefore the image required for inspection can be generated with fewer captures.

[0029] (7) The imaging device according to the seventh aspect of the present invention is an imaging device according to any one of the aspects to the sixth aspect of the present invention, wherein the imaging section is held by an arm driving section, and the imaging position relative to the object to be inspected can be changed and imaging can be performed by controlling the arm driving section.

[0030] By attaching the imaging unit to an arm drive unit composed of a six-axis collaborative robot or the like, it is possible to use a single imaging unit to capture images of the object to be inspected from any angle and distance.

[0031] (8) A surface inspection apparatus according to another aspect includes, in addition to the imaging device according to the first to seventh aspects of the present invention, an inspection image generating section that processes an image captured by the imaging device to generate an inspection image.

[0032] In a surface inspection device according to another aspect, even if the object to be inspected has a complex shape with multiple bends, by projecting a stripe image over a wider area of ​​the surface of the object to be inspected using multiple illuminations, it is possible to expand the range of inspection images that can be generated by imaging at the same imaging position, reduce the number of images to be captured, and shorten the inspection time.

[0033] (9) A surface inspection method according to yet another aspect is a surface inspection method for inspecting the surface condition of an object to be inspected that includes a mirror portion, and includes a fringe image projection step of projecting a fringe image onto the object to be inspected from a plurality of flat or concave-shaped illumination devices arranged to surround the periphery of the object to be inspected and one or more flat or concave-shaped mirrors that reflect the light of the illumination devices, an imaging step of imaging the object to be inspected onto which the fringe image is projected by an imaging unit arranged at a predetermined position relative to the object to be inspected, and an inspection image generation step of processing the image captured in the imaging step to generate an inspection image.

[0034] In a surface inspection method according to still another aspect, a plurality of flat or concave shaped lights and one or more flat or concave shaped mirrors are arranged to surround the periphery of the object to be inspected, and a fringe image is projected from each of the lights and mirrors, making it possible to project a fringe image over a wider area of ​​the surface of the object to be inspected, even if the object has a complex shape with multiple bends. This makes it possible to expand the range of inspection images that can be generated by imaging at the same imaging position, reduce the number of imaging operations, and shorten the inspection time.

[0035] There is no particular limitation on the method of generating an inspection image by processing an image captured by an imaging device to generate an inspection image. For example, as described in Patent Document 2, boundary areas between light and dark areas in the low frequency region are obtained from an image of an object to be inspected captured by an imaging unit, and areas in the high frequency region where the level is equal to or higher than a predetermined value are detected. From the areas with high levels in the high frequency region, only those areas that are not boundary areas between light and dark areas are extracted, and this image can be used as an inspection image for detecting defective areas. Also, a method of generating an inspection image using a plurality of images of the inspection object 10 onto which different stripe images are projected can be used. For example, the method described in Patent Document 1 can be used in which a first-order differential process is performed on each of the images of the inspection object onto which different stripe images are projected, and the differential values ​​of the plurality of images are added to generate an inspection image.

[0036] (A) The imaging device according to the Ath aspect of the present invention is the imaging device according to the third aspect of the present invention, wherein the illumination is a concave display, and the edge of the concave display may be mirror-finished.

[0037] By configuring the illumination using a concave display such as a liquid crystal display, the fringe image projected onto the object to be inspected can be freely changed. However, if the illumination is configured with a concave display, the edges of the display do not emit light. Therefore, the fringe image is not projected onto the part of the object where the edges of the display are reflected. In contrast, in the imaging device according to the seventh invention, the edges of the display are mirror-finished to reflect the fringe image from the opposing illumination or mirror, so that the fringe image can be projected onto the part of the object where the edges of the display are reflected. As a method for mirror finishing the edges, for example, a mirror sheet may be attached.

[0038] (B) The imaging device according to the Bth aspect of the present invention is the imaging device according to the one aspect to the sixth aspect of the present invention, and may further include a holding section that holds the object to be inspected rotatably along a vertical axis.

[0039] When imaging an object having a complex shape, it is necessary to image the object from various angles in the horizontal direction. In the imaging device according to the Bth aspect of the present invention, the object to be inspected is rotated in the vertical direction by the holding section and imaged, so that the object to be inspected can be imaged from various angles in the horizontal direction using a single imaging section.

[0040] (C) An imaging device according to a Cth aspect of the present invention is the imaging device according to the Bth aspect of the present invention, wherein the holding section is movable up and down in the vertical direction while holding the object to be inspected.

[0041] When imaging an object having a complex shape, it is necessary to image the object from various angles in the vertical direction. In the imaging device according to the Cth aspect of the invention, the object to be inspected is moved up and down in the vertical direction by the holding section and imaged, so that the object to be inspected can be imaged from various angles in the vertical direction using a single imaging section. [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 is a schematic block diagram showing an example of the configuration of an imaging device and a surface inspection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic perspective view showing an example of an internal arrangement of an imaging device. [Diagram 3] 5A to 5C are schematic diagrams showing examples of stripe images of each illumination. [Figure 4] 4 is a schematic side view showing an example of the configuration of an imaging unit and an arm driving unit. FIG. [Diagram 5] 13 is a schematic side view showing another example of the configuration of the imaging unit and the arm driving unit. FIG. [Figure 6] FIG. 4 is a schematic side view showing an example of the configuration of a holding portion. [Figure 7] 10 is a flowchart showing an example of a flow of imaging and surface inspection of an object to be inspected. [Figure 8] 11 is an image showing an example of an imaging result of an object to be inspected onto which a fringe image is projected. [Figure 9] 13 is an image showing another example of an imaging result of an object to be inspected onto which a fringe image is projected. [Figure 10] 13 is an image showing yet another example of an imaging result of an object to be inspected onto which a stripe image is projected. [Figure 11] 4 is an image showing an example of an inspection image of an object to be inspected generated by an inspection image generating unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Furthermore, when the reference numerals are the same, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0044] (Imaging device 100) FIG. 1 is a schematic block diagram showing an example of the configuration of an imaging device 100 and a surface inspection device 300 according to the present embodiment. Figure 2 is a schematic oblique view showing an example of the internal arrangement of the imaging device 100, Figure 3 is a schematic diagram showing an example of a stripe image of each illumination, Figure 4 is a schematic side view showing an example of the configuration of the imaging section 30 and the arm driving section 60, Figure 5 is a schematic side view showing another example of the configuration of the imaging section 30 and the arm driving section 60, and Figure 6 is a schematic side view showing an example of the configuration of the holding section 50.

[0045] 1 and 2, an object to be inspected 10 is fixed to a holder 50, and faces an imaging section 30 fixed to an arm driving section 60. The object to be inspected 10 is a member that includes a mirror surface portion. The inspection object 10 is surrounded by a ceiling light 20a, a rear light 20b, and a front light 20c, a mirror 40a on the side of the imaging unit 30, a mirror 40b below the inspection object 10, and a mirror 40c on the opposite side of the imaging unit 30 as viewed from the inspection object 10. The illuminations 20a, 20b, and 20c are configured with concave displays. By making the illumination 20 concave, a stripe image can be projected onto the inspection object 10 from a wider range of angles.

[0046] The imaging device 100 is equipped with illumination 20a, 20b, 20c and mirrors 40a, 40b, 40c, so that when the surface of the object 10 facing the imaging section 30 is defined as the front surface, illumination 20 or mirror 40 is positioned in all directions, including the front, rear, right, left, upward, and downward directions, of the object 10. The imaging device 100 is disposed in a housing 80, which normally has an opening and closing door (not shown) on the entrance side.

[0047] In this embodiment, lighting 20a, 20b, 20c and mirrors 40a, 40b, 40c are provided, however, lighting 20 may be arranged in four of the six directions with the remaining two directions being mirrors, lighting 20 may be arranged in five directions with the remaining one direction being a mirror, or lighting 20 may be arranged in two directions with the remaining four directions being mirrors.

[0048] (Lighting 20) In this embodiment, the illumination 20 is configured as a concave display, specifically, a liquid crystal display having a concave shape. By configuring the illumination 20 as a display such as a liquid crystal display, the stripe image projected onto the inspection object 10 can be freely changed. However, when the illumination 20 is configured as a display, the edge of the display does not emit light, and therefore the stripe image is not projected onto the part of the inspection object 10 where the edge of the display is reflected. For this reason, in the imaging device 100 of this embodiment, the edge of the display is mirror-finished to reflect the stripe image from the opposing illumination 20 or mirror 40, so that the stripe image can be projected onto the part of the inspection object 10 where the edge of the display is reflected. Note that as a method of mirror-finishing the edge, for example, a mirror sheet may be attached. Furthermore, when the object 10 to be inspected has a complex shape, particularly when the direction of the curved surface is not in one direction, for example, the direction of the stripe images of the ceiling-side light 20a, the back-side light 20b, and the front-side light 20c in Figure 2 may be made different for each light 20. Fig. 3(a) shows an example of a stripe image of the ceiling-side light 20a, Fig. 3(b) shows an example of a stripe image of the back-side light 20b, and Fig. 3(c) shows an example of a stripe image of the front-side light 20c. In Fig. 3, "front" is the direction of the imaging unit 30 as viewed from the inspection object 10, and the arrows show the movement direction of the stripe image when the stripe images are set sequentially. If a defect in the inspection object 10 is perpendicular to the movement direction of the fringe image, it may be difficult to find the defect. In contrast, by making the fringe images and their movement directions of the illuminations 20a, 20b, and 20c different as shown in Figure 3, the defect can be found reliably regardless of the direction of the defect. Alternatively, the stripe images and their movement directions of the respective illuminations 20a, 20b, and 20c may be the same, and the stripe image and its movement direction of FIG. 3(a) and the stripe image and its movement direction of FIG. 3(b) may be alternately switched. Alternatively, when curved surfaces are formed in two directions and the radii of curvature of the curved surfaces are different, the spacing between stripes of the stripe image may be made different for each stripe direction.

[0049] (Mirror 40) In this embodiment, the mirrors 40a and 40b are concave mirrors. The reason why the mirrors 40a and 40b are concave mirrors is that a fringe image can be projected onto the inspection object 10 from a wider angle using the mirror 40 having a relatively small area. In particular, when the mirrors 40a and 40b are parabolic mirrors, when the inspection object 10 is placed near the focal point of the parabolic mirror and a fringe image with nearly parallel rays is projected from the side facing the parabolic mirror, a fringe image with narrow spacing can be projected onto the inspection object 10. Then, by capturing an image of the inspection object 10 onto which this fringe image with narrow spacing is projected, an inspection image with higher accuracy can be generated. If there is a door at the location of mirror 40c, mirror 40c may be disposed on the back side of the door.

[0050] (Surface inspection device 300) Returning to Fig. 1, the surface inspection apparatus 300 includes, in addition to the imaging apparatus 100, a control unit 110, a display operation unit 120, and an inspection image generating unit 200. The control unit 110 controls the holding unit 50 to adjust the angle and height of the inspection object 10 on the horizontal plane, and controls the arm driving unit 60 to adjust the imaging angle and distance of the imaging unit 30 to the inspection object 10. The control unit 110 also sets the stripe images projected by the respective illuminations 20a, 20b, and 20c, and controls the imaging unit 30 to capture images. The display / operation unit 120 displays the images captured by the imaging unit 30 and the test images generated by the test image generating unit 200, and also performs necessary input operations. The control unit 110, the display / operation unit 120, and the inspection image generating unit 200 may be configured as a personal computer or the like connected to the imaging device 100 via a network. Also, at least a part of the functions of the inspection image generating unit 200 may be executed by another computer connected via a network, or a server on a cloud.

[0051] (Imaging unit 30 and arm driving unit 60) 4 and 5 are schematic side views showing an example of the configuration of the imaging unit 30 and the arm driving unit 60. In FIG. 4, a concave mirror 40a is provided at the tip of the arm driving unit 60, and the imaging unit 30 is provided at the center of the concave mirror 40a. On the other hand, FIG. 5 is the same as FIG. 4 in that a concave mirror 40a is provided at the tip of the arm driving unit 60, but the imaging unit 30 is arranged at an incline above the tip of the arm driving unit 60 so that the inspection object 10 can be imaged from an obliquely upward direction. Therefore, when the fringe image projected by the concave mirror 40a is to be imaged from the front, the configuration of FIG. 4 is desirable, and when the fringe image projected by the concave mirror 40a is to be imaged from an obliquely upward direction, the configuration of FIG. 5 is desirable. It is preferable to use a six-axis collaborative robot as the arm driving unit 60. In this case, the imaging angle and imaging distance can be freely set for the object 10 to be inspected by axial rotation and translation shown in Figs. The predetermined position of the imaging section 30 refers to the position in FIG. 4 where the inspection object 10 is imaged from the front, or the position in FIG. 5 where the inspection object 10 is imaged from obliquely above.

[0052] (Holding part 50) 6 is a schematic side view showing an example of the holding unit 50, the concave mirror 40b arranged at the tip of the holding unit 50, and the inspection object 10 fixed to the holding unit 50. The holding unit 50 is capable of rotating the held inspection object 10 along the vertical axis and moving it up and down in the vertical direction. Therefore, the imaging device 100 is configured to be able to image the inspection object 10 from any angle in the horizontal and vertical directions by cooperating the holding unit 50 and the arm driving unit 60 equipped with the imaging unit 30. A concave mirror 40b is disposed below the inspection object 10, and a stripe image of the illumination 20a etc. is reflected by the concave mirror 40b and projected onto the inspection object 10. Therefore, even when the inspection object 10 is imaged from an obliquely downward direction, the stripe image can be reliably projected onto the imaging portion of the inspection object 10.

[0053] (Imaging and surface inspection flow) 7 shows a flowchart of imaging and surface inspection using the imaging device 100 and the surface inspection device 300. The following will be described with reference to the flowchart in FIG. (Step S01) Set the imaging position of the imaging unit 30 with respect to the object under inspection 10. Specifically, the holding unit 50 rotates the object under inspection 10 in accordance with the imaging direction and moves it up and down, and then the arm driving unit 60 sets the direction and position of the imaging unit 30 in accordance with the imaging angle and imaging distance. (Step S02) Set the stripe image to be displayed on the illuminations 20a, 20b, and 20c. Usually, the direction, interval, and phase (position of the black stripes) of the stripe image are set before the first capture, and the phase is changed little by little from the second capture onwards. (Step S03) The imaging unit 30 images the object to be inspected 10. (Step S04) An inspection image required for inspection is generated using the image of the inspection object 10 onto which the captured fringe image is projected. The inspection image generation method will be described in detail later. (Step S05) Based on the generated inspection image, necessary inspections such as the presence or absence of defects are performed. The inspection may be performed by an operator looking at the inspection image and making a judgment, or the size and depth of the defect may be measured from the inspection image and the judgment may be made based on whether the measured value exceeds a threshold value, or the judgment may be made using AI or the like. (Step S06) The phase of the fringe image is changed little by little and imaging is repeated until the required number of fringe images are captured. The required number of fringe images varies depending on the object 10 to be inspected and the required resolution, but is, for example, about eight. (Step S07) After the required number of fringe images have been captured at the current imaging position, the inspection image generation process, and the inspection is completed, the imaging position is changed and fringe images are captured again. After the required number of fringe images have been captured at the imaging positions, the inspection image generation process, and the inspection is completed, the inspection is terminated. The number of imaging positions that require inspection is about 10 to 60, depending on the object 10 to be inspected. Therefore, the total number of images to be captured is about 80 to 480. Furthermore, when generating an inspection image using multiple images, in the flowchart of Figure 7, after completing capturing the required number of stripe images in step S6, it is necessary to perform the inspection image generation process (step S4) and inspection (step S5).

[0054] (Inspection image generation method) There is no particular limitation on the method for processing the image of the inspection object 10 onto which the fringe image is projected to generate an inspection image, but for example, the following method can be used. As described in Patent Document 2, from an image of the object to be inspected 10 captured by the imaging section 30, the boundary areas between light and dark areas in the low frequency region are obtained, and areas in the high frequency region where the level is equal to or higher than a predetermined value are detected. From the high level areas in the high frequency region, only the areas that are not boundary areas between light and dark areas are extracted, and this image can be used as an inspection image for detecting defective areas. Furthermore, as described in Patent Document 6, boundary points between light and dark areas of a light and dark pattern can be detected from an image of the object to be inspected 10 captured by the imaging unit 30, a master of the boundary line of the light and dark pattern can be created from this boundary point, and the boundary line of the light and dark pattern in the captured image can be compared with the boundary line of the master, thereby extracting only the parts where the shape of the light and dark pattern in the captured image has changed, and using this image as an inspection image for detecting defective parts.

[0055] The above is a method of generating an inspection image using one image of the object to be inspected 10 onto which a stripe image is projected, but a method of generating an inspection image using multiple images of the object to be inspected 10 onto which different stripe images are projected can also be used. However, when generating an inspection image using multiple images, in the flowchart of Figure 7, after completing capturing the required number of stripe images in step S6, the inspection image generation process (step S4) and inspection (step S5) must be performed. For example, as described in Patent Document 1, it is possible to use a method in which a first-order differential process is performed on an image of an object to be inspected 10 onto which different stripe images are projected, and the differential values ​​of the multiple images are added together to generate an inspection image. In this case, let I(xy) be the brightness at point (x, y) of the captured image, Ix(x, y) be its differential value in the x direction, and Iy(x, y) be its differential value in the y direction. Let Ixy be the magnitude of the differential value at point (x, y) of each captured image.

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[0056] Furthermore, as described in Patent Document 5, it is also possible to calculate the difference between the maximum and minimum luminance values ​​for each pixel in multiple images projected with different stripe images, and create an inspection image in which the luminance is the difference between the maximum and minimum luminance values ​​for each pixel. In this case, the area where no defects are formed will have high brightness when white stripes are projected and low brightness when black stripes are projected, so the difference between the maximum and minimum brightness values ​​will be large, and the brightness of the inspection image will be high. On the other hand, in the area where defects with irregularities such as bumps and dents are formed, the difference in brightness between when white stripes are projected and when black stripes are projected will be small, and the brightness of the inspection image will be low. Therefore, defects can be detected by detecting areas in the inspection image where the brightness is lower than a predetermined value.

[0057] Figures 8 to 10 show an example of a fringe image of the inspection object 10 captured by changing the phase of the fringes. Also, Figure 11 shows an inspection image generated by combining eight fringe images of the inspection object 10 including those shown in Figures 8 to 10. Since the surface of the inspection object 10 is mirror-finished, when the inspection object 10 is imaged normally, the illumination 20 and surrounding objects are reflected due to mirror reflection, making it difficult to tell whether the inspection object 10 has scratches or not. However, in Figure 11, the scratches on the inspection object 10 (area surrounded by a frame) are clearly visible, making this an ideal inspection image for the surface condition.

[0058] In the present invention, the object to be inspected 10 corresponds to the "object to be inspected", the surface inspection device 300 corresponds to the "surface inspection device", the imaging device 100 corresponds to the "imaging device", the lights 20, 20a, 20b, 20c correspond to "lighting", the imaging section 30 corresponds to the "imaging section", the mirrors 40, 40a, 40b, 40c correspond to "mirrors", the arm driving section 60 corresponds to the "arm driving section", and the inspection image generation section 200 corresponds to the "inspection image generation section".

[0059] Although the preferred embodiment of the present invention is as described above, the present invention is not limited thereto. It is understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the actions and effects of the configuration of the present invention are described in the present embodiment, these actions and effects are merely examples and do not limit the present invention. [Explanation of symbols]

[0060] 10. Inspection item 20, 20a, 20b, 20c lighting 30 Imaging unit 40,40a,40b,40c mirror 60 Arm drive unit 80 Case 100 Imaging device 200 Inspection image generation unit 300 Surface Inspection Equipment

Claims

1. An imaging device used in a surface inspection device that inspects a surface state of an object to be inspected that includes a mirror surface, A plurality of planar or concave illuminators are arranged to surround the periphery of the inspection object and project a fringe image onto the inspection object; an imaging section that is arranged at a predetermined position with respect to the object to be inspected and that images the object to be inspected onto which the fringe image is projected.

2. a fringe image projected onto the inspection object by the plurality of illuminations differs for each of the illuminations; The imaging device according to claim 1 , wherein the imaging section captures an image obtained by combining a plurality of stripe images projected by a plurality of the illuminations.

3. Further, the illumination device includes one or more mirrors having a flat or concave shape for reflecting light of the illumination, The fringe image reflected by the mirror is projected onto the object to be inspected; The imaging device according to claim 1 , wherein the imaging section captures an image obtained by combining a plurality of the illuminations and a plurality of the fringe images projected by the mirror.

4. The imaging device according to claim 3 , wherein one of the mirrors is disposed on the imaging section side.

5. the mirror is a parabolic mirror, The imaging device according to claim 4 , wherein the imaging section is disposed at the center of the mirror.

6. 4. The imaging device of claim 3, wherein the lighting or the mirror is arranged in all directions of the object to be inspected, including the front, rear, right, left, top, and bottom, when the surface of the object to be inspected facing the imaging unit is defined as the front surface.

7. 7. The imaging device according to claim 1, wherein the imaging section is held by an arm driving section, and the imaging position with respect to the object to be inspected can be changed and imaging can be performed by controlling the arm driving section.

8. 7. A surface inspection apparatus comprising: an imaging device according to claim 1; and an inspection image generating unit that processes an image captured by the imaging device to generate an inspection image.

9. A surface inspection method for inspecting a surface state of an object to be inspected that includes a mirror surface portion, comprising: a fringe image projection step of projecting a fringe image onto the object to be inspected from a plurality of flat or concave shaped illuminations arranged to surround the periphery of the object to be inspected and one or a plurality of flat or concave shaped mirrors that reflect the light of the illuminations; an imaging step of imaging the object onto which the fringe image is projected, by an imaging unit disposed at a predetermined position with respect to the object; and an inspection image generating step of processing the image captured in the imaging step to generate an inspection image.

Images