Image inspection device and image inspection method

Abstract

Provided are an image inspection device and an image inspection method that are capable of suppressing inspection omissions due to overexposure. An image inspection device (1) is characterized by comprising: an imaging unit (15); a first illumination unit (14) that emits illumination light from an imaging direction (D14) to an imaging area (A11); a second illumination unit (16) that emits background light through the imaging area (A11); an imaging processing unit (171) that causes the imaging unit (15) to continuously perform first imaging processing for imaging a workpiece while the same is irradiated with both the illumination light and the background light, and second imaging processing for imaging the workpiece while the same is irradiated only with the background light; and an inspection processing unit (172) that sets a potential overexposure area on the basis of a first captured image obtained through the first imaging processing, and that performs image inspection on the potential overexposure area on the basis of a second captured image obtained through the second imaging processing.

Description

Image inspection device and image inspection method

[0001] The present invention relates to an image inspection device and an image inspection method for photographing a workpiece and performing inspection using the photographed image.

[0002] Conventionally, an image inspection device and an image inspection method for photographing and inspecting a workpiece have been known (see, for example, Patent Document 1). In the image inspection device and image inspection method described in Patent Document 1, illumination light is applied to a photographing area where the workpiece is placed, the workpiece is photographed under the illumination light, and an appearance inspection of the workpiece is performed based on the photographed image.

[0003] JP 2016-148598 A

[0004] In the image inspection device and image inspection method described above, there is a possibility that partial highlights may occur in the image of the workpiece in the captured image depending on the shape of the workpiece, etc. This is undesirable because it may lead to missed inspections in appearance inspections based on the image.

[0005] Therefore, the present invention focuses on the above-mentioned problems and aims to provide an image inspection device and an image inspection method that can reduce inspection omissions due to overexposure.

[0006] In order to solve the above problem, the image inspection device is characterized by comprising: a photographing unit that photographs a predetermined photographing area; a first illumination unit that irradiates the photographing area with illumination light from the photographing direction of the photographing unit; a second illumination unit that is arranged on the opposite side of the photographing unit as viewed from the photographing area and irradiates background light over the photographing area onto the photographing unit; a photographing processing unit that causes the photographing unit to successively perform a first photographing process that photographs an inspection target workpiece arranged in the photographing area under illumination with at least the illumination light of the illumination light and the background light, and a second photographing process that photographs an inspection target workpiece under illumination with only the background light; and an inspection processing unit that sets a possible whiteout area in the first photographing image based on the first photographing image obtained in the first photographing process, where the possible whiteout area is likely to be whiteout, and performs image inspection of the possible whiteout area based on the second photographing image obtained in the second photographing process.

[0007] In order to solve the above problem, the image inspection method is characterized by comprising a work placement process in which the work is placed in the photographing area of ​​the above-mentioned image inspection device; a photographing process in which the photographing processing unit causes the photographing unit to perform the first photographing process and the second photographing process consecutively; and an inspection process in which the inspection processing unit sets the area at risk of whiteout based on the first photographed image and performs image inspection of the area at risk of whiteout based on the second photographed image.

[0008] According to the image inspection device and image inspection method described above, it is possible to prevent oversights due to overexposure.

[0009] 1 is a perspective view showing an image inspection device according to an embodiment. FIG. 5 is a plan view showing a workpiece set in the image inspection device shown in FIG. 1 as viewed from the imaging direction. FIG. 6 is a schematic diagram illustrating two captured images taken continuously under the control of the imaging processing unit shown in FIG. 1, and an image inspection performed in an inspection processing unit based on these two captured images. FIG. 7 is a schematic flowchart showing the processing flow of an image inspection method performed in the image inspection device shown in FIG. 1. FIG. 8 is a plan view showing a workpiece other than the twisted shielded pair electric wire set in the image inspection device shown in FIG. 1 as viewed from the imaging direction. FIG. 9 is a schematic diagram illustrating two captured images taken continuously of another example workpiece shown in FIG. 5, and an image inspection based on these two captured images.

[0010] An embodiment of an image inspection device and an image inspection method will be described below.

[0011] FIG. 1 is a perspective view showing an image inspection device according to one embodiment, and FIG. 2 is a plan view showing a workpiece set in the image inspection device shown in FIG. 1 as viewed from the imaging direction.

[0012] The image inspection device 1 of this embodiment is an apparatus that photographs a twisted shielded pair electric wire W1 shown in Fig. 2 as a workpiece and measures the position of the workpiece in the photographed image. In this embodiment, the twisted shielded pair electric wire W1 has two electric wires W11 serving as core wires exposed in an untwisted state at one end. In addition, the braided shield W12 covering the two electric wires W11 is exposed in a state where it is folded back to the outside of the outermost covering portion W13 at the base side of the exposed electric wires W11. The image inspection device 1 includes a stand frame 11, a workpiece holder 12, a first illumination unit 14, an imaging unit 15, a second illumination unit 16, and a processing unit 17.

[0013] The stand frame 11 is installed at a predetermined inspection location and is a frame member that supports the workpiece holder 12, the first illumination unit 14, the photographing unit 15, and the second illumination unit 16, and includes a base portion 111 and a support column portion 112. The base portion 111 is a rectangular plate-shaped portion that is placed at the inspection location, and the support column portion 112 is erected on its upper surface, and the second illumination unit 16 is attached to it. The support column portion 112 is an erect rectangular strip-shaped plate member with one end fixed to the base portion 111. The workpiece holder 12, the first illumination unit 14, and the photographing unit 15 are supported on one surface of the support column portion 112 by screws or the like.

[0014] The workpiece holder 12 is a component that chucks and holds the outermost covering portion W13 of the twisted shielded pair electric wire W1, and includes a plate portion 121 and a wire chuck portion 122. The plate portion 121 is a rectangular plate-shaped member, and one short side thereof is supported by the support column portion 112. The plate portion 121 has a central portion that overlaps with the second illumination unit 16 when viewed from the photographing unit 15, and defines a rectangular window 121a covered with a transparent plate. The wire chuck portion 122 is fixed near the end of the rectangular window 121a on the opposite side from the support column portion 112. In this embodiment, the rectangular window 121a defines the photographing area A11 of the photographing unit 15. The wire chuck portion 122 is a component that clamps and holds the vicinity of the exposed portion of the braided shield W12 of the outermost covering portion W13 of the twisted shielded pair electric wire W1 in a chuck direction D12 that is aligned with the length direction D11 of the support column portion 112. The electric wire chuck portion 122 clamps and holds the twisted shielded pair electric wire W1 between a first chuck 122a located on the plate portion 121 side and a second chuck 122b located on the photographing portion 15 side. The twisted shielded pair electric wire W1 held by the electric wire chuck portion 122 is held so that the two electric wires W11 and the exposed portion of the braided shield W12 are positioned on the photographing portion 15 side of the rectangular window 121a of the plate portion 121 (i.e., the photographing area A11).

[0015] The first illumination unit 14 includes an illumination holding plate 141 and a ring illumination 142. The illumination holding plate 141 is a sheet metal member bent into an L-shape in side view, with a support portion 141a corresponding to the short side of the L-shape supported by the support column portion 112. The ring illumination 142 is fixed to an illumination fixing portion 141b corresponding to the long side of the L-shape. The illumination holding plate 141 is supported by the support column portion 112 so that the illumination fixing portion 141b and the ring illumination 142 are positioned between the workpiece holder 12 and the imaging unit 15. This support is achieved by screwing the support portion 141a to the support column portion 112 so that its position can be adjusted in the longitudinal direction D11. A circular imaging window 141c for the imaging unit 15 is formed through the illumination fixing portion 141b in a portion that corresponds to the inside of the ring illumination 142. The ring light 142 is located between the photographing area A11 and the photographing unit 15, and irradiates the photographing area A11 with illumination light in a ring shape from the photographing direction D14 of the photographing unit 15. The twisted shielded pair electric wire W1 placed in the photographing area A11 as a workpiece is illuminated by this illumination light.

[0016] The photographing unit 15 photographs the photographing area A11 through the photographing window 141c of the lighting holding plate 141. When the twisted shielded pair electric wire W1 is placed as a work in the photographing area A11 as described above, the photographing unit 15 photographs the work. The photographing unit 15 includes a camera holding unit 151, a camera 152, and a photographing lens 153. The camera holding unit 151 is supported near the tip of the support column portion 112 and holds the camera 152 at a position where it can photograph through the photographing window 141c of the lighting holding plate 141. The camera 152 is a component that photographs the photographing area A11 and holds a cylindrical photographing lens 153 facing the photographing window 141c. The photographing lens 153 is a component that collects subject light passing through the photographing window 141c and sends it to the camera 152.

[0017] The second illumination unit 16 is a member with a rectangular block-like appearance that is located on the opposite side of the imaging unit 15 as viewed from the imaging area A11, specifically on the top surface of the base portion 111 of the stand frame 11. The second illumination unit 16 irradiates background light from its light-emitting surface 161 on the imaging unit 15 side over the imaging area A11 toward the imaging unit 15. The twisted shielded pair electric wire W1 placed in the imaging area A11 as the work is illuminated by this background light from the opposite side of the imaging direction D14.

[0018] The processing unit 17 is a control part that controls the operation of each unit in the image inspection device 1 and performs various inspection processes through image analysis of the image captured by the photographing unit 15. In this processing unit 17, the control part that controls the operation of the first illumination unit 14, the photographing unit 15, and the second illumination unit 16 constitutes the photographing processing unit 171, and the control part that performs image inspection based on the photographed image constitutes the inspection processing unit 172.

[0019] The photography processing unit 171 causes the photography unit 15 to continuously perform the following first photography process and second photography process on the twisted shielded pair electric wire W1 arranged in the photography area A11. The first photography process is a process of photographing under illumination with both the illumination light from the first illuminator 14 and the background light from the second illuminator 16. On the other hand, the second photography process is a process of photographing under illumination with only the background light from the second illuminator 16. In order to continuously perform these photography processes, the photography processing unit 171 controls the timing of continuous shooting by the photography unit 15 and the timing of turning on and off the first illuminator 14 and the second illuminator 16, particularly the timing of turning on and off the first illuminator 14, so as to synchronize them with each other.

[0020] The inspection processing unit 172 performs the following image inspection based on the two captured images obtained by the above-mentioned continuous imaging.

[0021] Fig. 3 is a schematic diagram illustrating two captured images successively captured under the control of the image capturing processing unit shown in Fig. 1, and an image inspection performed in the inspection processing unit based on the two captured images. Fig. 3(A) shows a first captured image G11 obtained in a first image capturing process performed under illumination with both illumination light and background light, and Fig. 3(B) shows a second captured image G12 obtained in a second image capturing process performed under illumination with only background light.

[0022] The first photographed image G11 shown in Fig. 3A shows the twisted shielded pair electric wire W1 illuminated by both the illumination light and the background light, making it easy to capture its external features, while the second photographed image G12 shown in Fig. 3B shows the twisted shielded pair electric wire W1 illuminated only by the background light, creating a silhouette.

[0023] The inspection processing unit 172 performs the following processing on these two captured images. First, the inspection processing unit 172 performs an appearance inspection of the twisted shielded pair electric wire W1 as the workpiece based on the first captured image G11 obtained in the first imaging processing. Furthermore, the inspection processing unit 172 sets a whiteout possibility area A12 in the first captured image G11 where whiteout is likely to occur.

[0024] In this embodiment, the twisted shielded pair electric wire W1 as the workpiece has a protruding portion W14 that may cause a microscopic object W15 to protrude and be overexposed during photography. In the example of Fig. 3, the protruding portion W14 is a folded portion of the braided shield W12, and the microscopic object W15 is a strand portion that has frayed and protruded from the braided shield W12. When illuminated by illumination light, such a strand portion blends into the background light and becomes overexposed during photography. Note that Fig. 3(A) illustrates the microscopic object W15, which does not appear in the first photographed image G11 due to overexposure, for illustrative purposes.

[0025] The inspection processing unit 172 sets the potentially overexposed areas A12 by pattern matching processing of the folded portion of the braided shield W12, which is assumed to be the potentially protruding portion W14. The inspection processing unit 172 uses this pattern matching processing to identify the image of the potentially protruding portion W14 in the first captured image G11 and sets a rectangular matching area A13 surrounding the identified portion. Then, the inspection processing unit 172 sets a pair of rectangular areas adjacent to the matching area A13 so as to sandwich the matching area A13 in the cross direction D15 relative to the twisted shielded pair electric wire W1 as the potentially overexposed areas A12. The width of each potentially overexposed area A12 in the cross direction D15 is set to the minimum necessary width that is narrower than the matching area A13. Meanwhile, the length of each potentially overexposed area A12 along the twisted shielded pair electric wire W1 is determined based on the expected size and shape of the potentially protruding portion W14 and the minute object W15. In the example of FIG. 3 , the length of the potentially overexposed areas A12 is set to be approximately the same as the length of the matching area A13.

[0026] Next, the inspection processing unit 172 applies the pair of likely whiteout areas A12 set as described above to the silhouette-shaped second captured image G12 and inspects each likely whiteout area A12 for the presence or absence of a microscopic object W15 through image inspection. In the silhouette-shaped second captured image G12, the wire portion of the braided shield W12 serving as the microscopic object W15 appears as a black line. Using this, the inspection processing unit 172 inspects for the presence or absence of a microscopic object W15 by calculating the color area of ​​the black portion in the likely whiteout area A12.

[0027] In the image inspection device 1 shown in FIG. 1, the inspection of the twisted shielded pair electric wire W1 as the workpiece is performed by the following image inspection method, which includes the inspection of the above-mentioned minute object W15.

[0028] FIG. 4 is a schematic flowchart showing the flow of processing of the image inspection method performed in the image inspection apparatus shown in FIG.

[0029] 4, first, a work placement step (S11) is performed in which a twisted shielded pair electric wire W1 is placed as a work in a photographing area A11 of the image inspection device 1. Next, an imaging step (S12) is performed in which the photographing processing unit 171 causes the photographing unit 15 to successively perform a first photographing process (S121) and a second photographing process (S122).

[0030] After the photographing step (S12), an inspection step (S13) is performed by the inspection processing unit 172. In this inspection step (S13), first, an appearance inspection (S131) ​​is performed based on the first photographed image G11, and an area A12 where whiteout is likely to occur is set (S132) based on the first photographed image G11. Furthermore, an inspection (S133) of the area A12 where whiteout is likely to occur is performed based on the silhouette-shaped second photographed image G11.

[0031] Up to this point, we have taken the twisted shielded pair electric wire W1 as an example of the workpiece to be inspected, and have described inspecting the presence or absence of fine particles W15 that cause whiteout, where the wire portions that have frayed and protruded from the braided shield W12 are the fine particles. However, the workpiece is not limited to the twisted shielded pair electric wire W1, and the image inspection device 1 shown in Figure 1 can also inspect the presence or absence of fine particles that cause whiteout, for other example workpieces such as the following.

[0032] Fig. 5 is a plan view showing a workpiece other than the twisted shielded pair electric wire set in the image inspection device shown in Fig. 1, as viewed from the imaging direction. Fig. 6 is a schematic diagram illustrating two images successively captured of the workpiece of the other example shown in Fig. 5, and image inspection based on those two images. Fig. 6(A) shows a first captured image G21 obtained by a first imaging process for the workpiece of the other example, and Fig. 6(B) shows a second captured image G22 obtained by a second imaging process for the workpiece of the other example.

[0033] In the examples of Figures 5 and 6, a single terminal-attached electric wire W2 is illustrated as the workpiece held by the electric wire chuck portion 122 of the workpiece holder 12. This terminal-attached electric wire W2 is an electric wire W21 with a connector terminal W22 crimped to the end thereof. The terminal-attached electric wire W2 is held so that the tip of the terminal-attached electric wire W2 with the connector terminal W22 crimped thereto is positioned on the photographing unit 15 side of the rectangular window 121a (i.e., photographing area A11) of the plate portion 121. In this terminal-attached electric wire W2, the exposed conductor portion W211 at the end of the electric wire W21 and the crimped portion W23 of the connector terminal W22 form a protrusion potential portion W24 that may cause a fine particle W25 to protrude and result in overexposed highlights. Note that Figure 5 shows this crimped portion W23 in a state before crimping, and Figure 6 shows it in a state after crimping. In this example, the fine object W25 is a strand portion that has frayed from the exposed conductor portion W211, which is a twisted wire.

[0034] For such a workpiece, the inspection processing unit 172 sets the overexposed area A22 as follows: First, a pattern matching process is performed on the crimped portion W23 of the terminal-attached electric wire W2. The inspection processing unit 172 uses this pattern matching process to identify the image of the protrusion-possible portion W24 in the first captured image G21 and set a rectangular matching area A23. Then, a pair of rectangular areas adjacent to the matching area A23 so as to sandwich the protrusion-possible portion W24 in the cross direction D15 relative to the terminal-attached electric wire W2 are set as the overexposed area A22. In this example, based on the assumption that the bare wire portion will protrude from the crimped portion W23, the overexposed area A22 is set narrower than the matching area A23 and longer than the matching area A23.

[0035] According to the image inspection device 1 and image inspection method of the embodiment described above, the overexposed areas A12 and A22 are set based on the first captured images G11 and G21, which are acquired under illumination light from the shooting direction D14 and allow easy capture of the workpiece's features. Then, image inspection of the overexposed areas A12 and A22 is performed based on the second captured images G12 and G22, which are acquired under background light only, immediately following the first captured images G11 and G21. Because the first captured images G11 and G21 and the second captured images G12 and G22 are captured consecutively, the position of the workpiece image is the same between these two images. Therefore, the overexposed areas A12 and A22 set based on the first captured images G11 and G21 can also be applied to the second captured images G12 and G22. Furthermore, the second captured images G12 and G22 provide silhouette images that allow easy capture of the workpiece's outline due to the background light, so that even areas that would be overexposed under illumination light are clearly visible. Therefore, by performing image inspection of the areas A12 and A22 where whiteout is likely to occur based on the second captured images G12 and G22, it is possible to reduce oversights due to whiteout.

[0036] In this embodiment, the inspection processing unit 172 performs pattern matching processing to identify images of the possible protrusion portions W14, W24 in the first captured images G11, G21, and sets adjacent areas of these images as possible whiteout areas A12, A22. The inspection processing unit 172 then inspects the possible whiteout areas A12, A22 in the second captured images G12, G22 to determine whether or not minute objects W15, W25 protrude from the possible protrusion portions W14, W24. This configuration makes it possible to effectively identify images of the possible protrusion portions W14, W24 and set the possible whiteout areas A12, A22 by pattern matching the first captured images G11, G21, which make it easy to capture the characteristics of the workpiece.

[0037] In this embodiment, the inspection processing unit 172 not only sets the overexposed areas A12, A22 but also performs an appearance inspection of the workpiece based on the first captured images G11, G21. With this configuration, the first captured images G11, G21, which easily capture the characteristics of the workpiece, can also be used for the appearance inspection of the workpiece, making it possible to perform a wide range of inspections of the workpiece.

[0038] The above-described embodiments merely show typical examples of the image inspection device and image inspection method. The image inspection device and image inspection method are not limited to these, and can be implemented in various modifications.

[0039] For example, in the above-described embodiment, the image inspection device 1 is exemplified as an example of an image inspection device, which photographs the twisted shielded pair electric wire W1 and the electric wire with terminal W2 as workpieces and performs various inspections. However, the image inspection device is not limited to these, and may photograph and inspect electric wires other than the twisted shielded pair electric wires and the electric wire with terminals, or any member other than electric wires as workpieces.

[0040] Furthermore, in the above-described embodiment, as an example of an image inspection device, an image inspection device 1 is exemplified in which illumination light in the shooting direction D14 is irradiated by the ring illumination 142 and background light is irradiated by the rectangular block-shaped second illumination unit 16. However, the image inspection device is not limited to this, and the specific shapes of various illuminations are not important.

[0041] In the above-described embodiment, the photographing processing unit 171 is exemplified as an example of the photographing processing unit, which causes the photographing unit 15 to perform the first photographing process (S121) in which photographing is performed under illumination with both illumination light and background light. However, the photographing processing unit is not limited to this, and the photographing processing unit may perform photographing under illumination with only illumination light in the first photographing process.

[0042] Furthermore, in the above-described embodiment, the inspection processing unit 172 that sets the likely whiteout areas A12, A22 through pattern matching processing on the first captured images G11, G21 is exemplified as an example of the inspection processing unit. However, the inspection processing unit is not limited to this, and the specific setting processing of the likely whiteout areas based on the first captured images is not limited to this. However, as described above, the likely whiteout areas A12, A22 can be effectively set by using pattern matching processing.

[0043] In this embodiment, the inspection processing unit 172 is exemplified as an example of an inspection processing unit that also performs a visual inspection of the workpiece based on the first captured images G11 and G21. However, the inspection processing unit is not limited to this, and may only perform processing to set areas where overexposure is likely to occur for the first captured images. However, as described above, by also performing a visual inspection based on the first captured images G11 and G21, a wide range of inspections of the workpiece can be performed.

[0044] DESCRIPTION OF SYMBOLS 1 Image inspection device 11 Stand frame 12 Workpiece holding table 14 First lighting unit 15 Photography unit 16 Second lighting unit 17 Processing unit 111 Base part 112 Support column part 121 Plate part 121a Rectangular window 122 Wire chuck part 122a First chuck 122b Second chuck 141 Lighting holding plate 141a Support part 141b Lighting fixing part 141c Photography window 142 Ring lighting 151 Camera holding part 152 Camera 153 Photography lens 161 Light emitting surface 171 Photography processing unit 172 Inspection processing unit A11, A21 Photography area A12, A22 Possible whiteout area A13, A23 Matching area D11 Length direction D12 Chuck direction D14 Photography direction D15 Crossing direction G11, G21 First captured image G12, G22 Second captured image S11 Workpiece placement process S12 Photographing process S13 Inspection process S121 First photographing process S122 Second photographing process S131 Visual inspection S132 Setting of areas where whiteout may occur S133 Inspection of areas where whiteout may occur W1 Twisted shielded pair electric wire (workpiece) W2 Electric wire with terminal (workpiece) W11, W21 Electric wire W12 Braided shield W13 Outermost sheathed part W14, W24 Part where protrusion may occur W15, W25 Fine object W22 Connector terminal W23 Crimped part W211 Exposed conductor part

Claims

1. An image inspection device comprising: a photographing unit that photographs a predetermined photographing area; a first illumination unit that irradiates the photographing area with illumination light from the photographing direction of the photographing unit; a second illumination unit that is arranged on the opposite side of the photographing unit as viewed from the photographing area and irradiates background light over the photographing area onto the photographing unit; a photographing processing unit that causes the photographing unit to successively perform a first photographing process in which an inspection target workpiece arranged in the photographing area is photographed under illumination with at least the illumination light of the illumination light and the background light, and a second photographing process in which the workpiece is photographed under illumination with only the background light; and an inspection processing unit that sets areas in the first photographed image that are likely to be overexposed, based on the first photographed image obtained in the first photographing process, and performs image inspection of the areas that are likely to be overexposed, based on the second photographed image obtained in the second photographing process.

2. The image inspection device described in claim 1, characterized in that the workpiece has a protruding portion that has the potential to cause a minute object to protrude and become overexposed when photographed, and the inspection processing unit performs pattern matching processing on the protruding portion to identify an image of the protruding portion in the first photographed image, sets an adjacent area of ​​the image as the overexposed area, and inspects the presence or absence of the minute object in the image inspection of the overexposed area in the second photographed image.

3. The image inspection device according to claim 1, characterized in that the inspection processing unit performs an appearance inspection of the workpiece in addition to setting the area at risk of overexposure based on the first captured image.

4. An image inspection method comprising: a workpiece placement step of placing the workpiece in the photographing area of ​​the image inspection device described in any one of claims 1 to 3; a photographing step in which the photographing processing unit causes the photographing unit to perform the first photographing process and the second photographing process consecutively; and an inspection step in which the inspection processing unit sets the area at risk of whiteout based on the first photographed image and performs image inspection of the area at risk of whiteout based on the second photographed image.

Images