Image inspection device and image inspection method

Abstract

To provide an image inspection device and an image inspection method capable of stabilizing adjustment precision of focusing.SOLUTION: An image inspection device 1 comprises: a photographing section 15; a focus confirmation tool 13 that is disposed in a photographing area A11 before a workpiece to be inspected and is used to previously confirm focusing of photographing while a part facing a side of the photographing section 15 when being disposed in the photographing area A11 becomes a confirmed section in a shape in which the position in the depth direction of a field depth of the photographing section is changed in steps; and a focus adjustment section 171 for adjusting focusing such that a target section corresponding to a workpiece in the confirmed section is included in a range of the depth of field on the basis of a tool photographed image obtained by photographing the focus confirmation tool 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[0002] Conventionally, an image inspection device and an image inspection method for photographing and inspecting a workpiece are known (see, for example, Patent Document 1). In the image inspection device and image inspection method described in Patent Document 1, the focus is adjusted so that the workpiece falls within the depth of field of the photographing unit, and the workpiece is photographed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-253903 Summary of the Invention [Problem to be solved by the invention]

[0004] In the image inspection device and image inspection method described above, the focus may be adjusted by the user visually inspecting the captured image of the workpiece, etc. In such focus adjustment, the accuracy of the adjustment often depends on the skill of the user, and there is a problem in that the adjustment accuracy is not stable.

[0005] Therefore, the present invention has been made in view of the above-mentioned problems, and has as its object to provide an image inspection apparatus and an image inspection method that can stabilize the focus adjustment accuracy. [Means for solving the problem]

[0006] In order to solve the above problem, the image inspection device is characterized by comprising: a photographing unit that photographs a specified photographing area; a focus confirmation jig that is placed in the photographing area prior to the work to be inspected and is used to confirm in advance the focus of the photographing of the work by the photographing unit, wherein the part that faces the photographing unit when placed in the photographing area becomes a confirmed part having a shape in which the depth-wise position of the depth of field of the photographing unit changes stepwise or continuously; and a focus adjustment unit that adjusts the focus based on a jig photographed image of the focus confirmation jig placed in the photographing area taken by the photographing unit so that a work-corresponding target part in the confirmed part that corresponds to the placement position of the work is included within the depth of field of the photographing unit.

[0007] In order to solve the above problem, the image inspection method is characterized by comprising a jig placement process in which the focus confirmation jig is placed in the shooting area of ​​the above-mentioned image inspection device, a jig photographing process in which the photographing unit photographs the focus confirmation jig in the shooting area, and a focus adjustment process in which the focus adjustment unit adjusts the focus based on the jig photographed image so that a work-corresponding target portion in the confirmed portion corresponding to the placement position of the work is included within the depth of field of the photographing unit. [Effects of the Invention]

[0008] According to the image inspection device and image inspection method described above, it is possible to stabilize the focus adjustment accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing an image inspection device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a state in which a focus confirmation jig is set in the image inspection device shown in FIG. 1 prior to a workpiece to be inspected. [Figure 3]2 is a diagram showing a state in which a twisted shielded pair electric wire is set as a work to be inspected in the image inspection device shown in FIG. 1. FIG. [Figure 4] FIG. 2 is an explanatory diagram for explaining focus adjustment in the image inspection device shown in FIG. [Figure 5] FIG. 3 is a perspective view showing the focus checking jig shown in FIGS. 1 and 2 ; [Figure 6] 4 is a schematic diagram showing a jig photographed image obtained by photographing the focus confirmation jig shown in FIG. 3. FIG. [Figure 7] 7 is a diagram showing an in-focus image and an out-of-focus image side by side for the area B11 in FIG. 6. FIG. [Figure 8] This figure shows the state in which focus adjustment is performed in the focus adjustment unit, as represented by a graph showing the relationship between the width dimension of the second jig photographed image shown in Figure 6(B) and the measurement position corresponding to each step of the stair-shaped confirmed part in the focus confirmation jig. [Figure 9] 2 is a schematic flowchart showing the flow of processing of an image inspection method performed in the image inspection device shown in FIG. 1. [Figure 10] FIG. 10 is a perspective view showing a focus checking jig according to a second embodiment. [Figure 11] 11 is a schematic diagram showing a jig photographed image obtained by photographing the focus confirmation jig shown in FIG. 10. FIG. [Figure 12] 9 is a graph equivalent to FIG. 8 relating to the first embodiment, showing how focus adjustment is performed in a focus adjustment unit. FIG. [Figure 13] FIG. 11 is a perspective view showing a focus checking jig according to a third embodiment. [Figure 14] 14 is a schematic diagram showing a jig photographed image obtained by photographing the focus confirmation jig shown in FIG. 13. FIG. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] Fig. 1 is a perspective view showing an image inspection device according to a first embodiment, and Fig. 2 is a diagram showing a state in which a focus confirmation jig is set in advance of a workpiece to be inspected in the image inspection device shown in Fig. 1. Also, Fig. 3 is a diagram showing a state in which a twisted shielded pair electric wire is set as a workpiece to be inspected in the image inspection device shown in Fig. 1.

[0012] The image inspection device 1 of this embodiment is an apparatus that photographs a twisted shielded pair electric wire W1 shown in Fig. 3 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 as core wires exposed in an untwisted state at one end, and the end coating of each electric wire W11 is removed to form an exposed conductor portion W12. The image inspection device 1 includes a stand frame 11, a workpiece holder 12, a focus confirmation jig 13, 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 vicinity of the exposed wire portion of the outermost sheathed 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 wire portion of the outermost sheathed portion W13 of the twisted shielded pair electric wire W1 in a chuck direction D12 that is aligned with the longitudinal direction D11 of the support column portion 112. The electric wire chuck portion 122 holds the twisted shielded pair electric wire W1 by clamping it between a first chuck 122a located on the plate portion 121 side and a second chuck 122b located on the imaging unit 15 side. Note that Fig. 3 shows the electric wire chuck portion 122 with the second chuck 122b removed so that the twisted shielded pair electric wire W1 to be held can be seen. The twisted shielded pair electric wire W1 held by the electric wire chuck portion 122 is held such that the exposed conductor portions W12 of the two electric wires W11 are positioned on the imaging unit 15 side of the rectangular window 121a of the plate portion 121 (i.e., the imaging area A11).

[0015] The focus checking jig 13 is placed in the photographing area A11 as shown in Figures 1 and 2 prior to the twisted shielded pair electric wire W1, which is the workpiece to be inspected, and is used to check in advance the focus of photography by the photographing unit 15. The focus checking jig 13 will be described again later with reference to another drawing.

[0016] 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, and a support portion 141a corresponding to the short side of the L-shape is 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 fixing the support portion 141a with screws in a state where its position can be adjusted in the length direction D11 of the support column portion 112. 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 twisted shielded pair electric wire W1 as the workpiece, the focus confirmation jig 13, and the photographing unit 15, and irradiates the workpiece and the focus confirmation jig 13 with illumination light in a ring shape from the photographing direction D14 of the photographing unit 15.

[0017] The photographing unit 15 photographs the photographing area A11 through the photographing window 141c of the illumination 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. On the other hand, when the focus confirmation jig 13 is placed in the photographing area A11 prior to the twisted shielded pair electric wire W1, the photographing unit 15 photographs the focus confirmation jig 13. Here, in this embodiment, the twisted shielded pair electric wire W1 is photographed under illumination from the ring illumination 142 of the first illumination unit 14 and the second illumination unit 16, which will be described later. On the other hand, the focus confirmation jig 13 is photographed under illumination from only the second illumination unit 16, with the ring illumination 142 turned off.

[0018] 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 take pictures 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.

[0019] The second illumination unit 16 is a member with a rectangular block-like appearance that is fixed to the opposite side of the photographing unit 15 from the twisted shielded pair electric wire W1 and the focus confirmation jig 13, specifically to the upper 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 photographing unit 15 side, through the twisted shielded pair electric wire W1 and the focus confirmation jig 13, onto the photographing unit 15.

[0020] 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. Here, in this processing unit 17, a control part that adjusts the focus based on the jig-photographed image of the focus confirmation jig 13 placed in the photographing area A11 photographed by the photographing unit 15 constitutes a focus adjustment unit 171 that adjusts the focus. The focus adjustment at this time is a process performed on the photographing unit 15 so that the image of the twisted shielded pair electric wire W1 is captured under the following conditions.

[0021] FIG. 4 is an explanatory diagram for explaining focus adjustment in the image inspection apparatus shown in FIG.

[0022] 4 shows the wire W11 of the twisted shielded pair wire W1 as the workpiece and the depth of field range A12 of the imaging unit 15. In the example of FIG. 4, focus is adjusted so that the wire W11 including the exposed conductor portion W12 and a part of the outermost sheath portion W13 on the imaging unit 15 side fit within the depth of field range A12. The depth of field range A12 after such adjustment is a range in which the lower end of the exposed conductor portion W12 in the drawing is the lower limit position A121 and the upper end of the outermost sheath portion W13 in the drawing is the upper limit position A122 in the depth direction D13 of the depth of field along the imaging direction D14. The focus adjustment unit 171 in the processing unit 17 drives the imaging lens 153 of the imaging unit 15 to change its focal length, thereby moving the depth of field range A12 in the depth direction D13 of the depth of field. Then, the focus adjustment unit 171 controls the photographing lens 153 so that the depth of field range A12 is positioned as described above for the twisted shielded pair electric wire W1.

[0023] Such focus adjustment is performed by placing the focus checking jig 13 in the photographing area A11 in advance, without placing the twisted shielded pair electric wire W1 as the work in the photographing area A11.

[0024] FIG. 5 is a perspective view showing the focus checking jig shown in FIGS. 1 and 2. FIG.

[0025] When placed in the photographing area A11, the focus confirmation jig 13 in this embodiment is a roughly rectangular block-shaped member having a band shape in a plan view seen from the photographing unit 15. In this case, the part of the focus confirmation jig 13 that faces the photographing unit 15 when placed in the photographing area A11 is a confirmed portion 131 having a shape in which the position in the depth direction D13 of the depth of field of the photographing unit 15 changes stepwise. Furthermore, this confirmed portion 131 has a staircase shape in which the position in the depth direction D13 of the depth of field changes stepwise in a predetermined direction, specifically, in the band length direction D15 of the band shape in the plan view.

[0026] When adjusting the focus, the focus checking jig 13 is placed in the photographing area A11 so that the strip length direction D15 is aligned with the wire length direction of the twisted shielded pair electric wire W1 when it is arranged. Then, the photographing unit 15 photographs the focus checking jig 13.

[0027] Fig. 6 is a schematic diagram showing jig photographed images obtained by photographing the focus confirmation jig shown in Fig. 3. Fig. 6(A) shows a first jig photographed image G11 obtained under illumination with both the illumination light from the ring illumination 142 of the first illumination unit 14 and the background light from the second illumination unit 16. Fig. 6(B) shows a second jig photographed image G12 obtained under illumination with only the background light from the second illumination unit 16.

[0028] In the first jig photographed image G11 of FIG. 6A, the position of each step of the staircase shape in the confirmed portion 131 in the depth direction D13 of the depth of field from a predetermined reference position 13a (FIG. 5) is indicated by a numerical value. As indicated by these numerical values, the position of the confirmed portion 131 from the reference position 13a increases stepwise in 0.5 mm increments in the strip length direction D15. One of the steps of this staircase shape is the work-corresponding target portion 131a corresponding to the placement position of the twisted shielded pair electric wire W1 when placed in the photographing area A11. In FIG. 6A, as an example, the step located at a height of "+2.0" from the reference position 13a is designated as the work-corresponding target portion 131a. The adjustment by the focus adjustment unit 171 is a process of driving the photographing lens 153 to adjust the focus so that the work-corresponding target portion 131a is included within the depth of field range A12 of the photographing unit 15.

[0029] The second jig photographed image G12 in FIG. 6(B) is a silhouette image of the focus confirmation jig 13 photographed under illumination with only background light from the second illumination unit 16. In this embodiment, the second jig photographed image G12 as this silhouette image is used to determine whether the workpiece corresponding target portion 131a is included within the depth of field range A12. That is, in this embodiment, adjustment by the focus adjustment unit 171 is performed based on the second jig photographed image G12. The processing at this time is performed by utilizing the following properties of the second jig photographed image G12 as a silhouette image.

[0030] Fig. 7 is a diagram showing an in-focus image and an out-of-focus image side by side for area B11 in Fig. 6. Fig. 7(A) shows the in-focus image, and Fig. 7(B) shows the out-of-focus image.

[0031] The images shown in Figures 7(A) and 7(B) are both enlarged images of the edge portion of the second jig-captured image G12 shown in Figure 6. In this case, the image G12-1, which is in focus as shown in Figure 7(A), i.e., the image G12-1 near the center of the depth of field range A12, has its edge G12-1a in a clear, high-density image all the way to the edge. On the other hand, the image G12-2, which is out of focus and away from the center of the depth of field range A12 as shown in Figure 7(B), has its edge G12-2a in a blurred image with a partially reduced image density due to the defocus. Furthermore, the width T11 of the high-density image portion G12-2c, excluding the low-density edge portion G12-2b where the image density has decreased to a predetermined level or more due to the defocus, from the band-shaped second jig-captured image G12, changes depending on the focus state as follows: That is, the width T11 of the high-density image portion G12-2c in the second jig photographed image G12 becomes wider as the portion is in focus, that is, closer to the center of the depth of field range A12.

[0032] The focus adjustment unit 171 first measures the width T11 of the high-density image portion G12-2c in the second jig photographed image G12 at multiple locations in the strip length direction D15 of the focus confirmation jig 13, specifically, for each step of the staircase-shaped confirmed portion 131. At this time, the width T11 of the step that is best in focus is the maximum width, and this maximum-width step moves in the strip length direction D15 when the focus of the photographing unit 15 is changed. The focus adjustment unit 171 adjusts the focus by driving the photographing lens 153 so that the work corresponding target portion 131a, which is predetermined in correspondence with the arrangement position of the twisted shielded pair electric wire W1, has the maximum width.

[0033] Figure 8 is a graph showing the relationship between the width dimension of the second jig photographed image shown in Figure 6(B) and the measurement position corresponding to each step of the stair-shaped confirmed part in the focus confirmation jig, illustrating how the focus is adjusted in the focus adjustment section.

[0034] In graph C11 of FIG. 8, the horizontal axis indicates the measurement position (mm) of the width dimension T11 of the high-density image portion G12-2c in the second jig-captured image G12, corresponding to each step of the confirmed portion 131. The numerical values ​​listed as the measurement positions are numerical values ​​listed as positions in the depth direction D13 of the depth of field from the reference position 13a (FIG. 5) in FIG. 6A. The vertical axis of graph C11 indicates the width dimension T11 (mm) of the high-density image portion G12-2c in the second jig-captured image G12. From the width dimension T11 of each measurement position plotted on graph C11, it can be seen that the width dimension T11 of the workpiece-corresponding target portion 131a, which corresponds to the step "+2.0" shown as an example in FIG. 6A, is the widest. This means that the focus was adjusted so that the workpiece-corresponding target portion 131a of the focus confirmation jig 13 is included within the depth of field range A12 of the photographing unit 15.

[0035] Furthermore, in this embodiment, the focus adjustment unit 171 adjusts the focus so that the width dimension T11 of the high-density image portion G12-2c changes in the band length direction D15 of the confirmed portion 131 of the focus confirmation jig 13 as follows: That is, the focus adjustment unit 171 adjusts the focus so that the distribution of the width dimension T11 of the high-density image portion G12-2c becomes a uniform mountain-shaped distribution with the work-corresponding target portion 131a as the apex in the band length direction D15. Graph C11 in FIG. 8 shows that the distribution of the width dimension T11 becomes a uniform mountain-shaped distribution with the work-corresponding target portion 131a as the apex. This means that the maximum width portion (i.e., the work-corresponding target portion 131a) is located near the center, not at the end, of the depth of field range A12. The focus adjustment unit 171 adjusts the focus so that the width dimension T11 becomes a uniform mountain-shaped distribution.

[0036] In the image inspection device 1 shown in FIG. 1, the inspection of the twisted shielded pair electric wire W1 as the workpiece is carried out by the following image inspection method including the above-mentioned focus adjustment.

[0037] FIG. 9 is a schematic flowchart showing the flow of processing of the image inspection method performed in the image inspection device shown in FIG.

[0038] In the image inspection method shown in Fig. 9, first, a jig placement step (S11) is performed by a user, in which the focus confirmation jig 13 is placed in the photographing area A11 of the image inspection device 1. Next, a jig photographing step (S12) is performed, in which the photographing unit 15 photographs the focus confirmation jig 13 in the photographing area A11. Here, in this embodiment, photographing in this jig photographing step (S12) is performed under illumination with only background light from the second illumination unit 16, and a second jig photographed image G12 is obtained as a silhouette image, as schematically shown in Fig. 6(B). Note that this second jig photographed image G12 is repeatedly photographed at regular intervals in parallel with the subsequent focus adjustment process.

[0039] When repeated photographing of the second jig photographed image G12 begins, a focus driving step (S13) is performed in which the focus adjustment unit 171 drives the photographing lens 153 to change the focus in predetermined increments. Then, each time the focus is changed by one increment, a focus determination step (S14) is performed in which it is determined whether or not a predetermined workpiece corresponding target portion 131a is included within the range A12 of the depth of field.

[0040] In the focus determination step (S14), the width dimension T11 of the high-density image portion G12-2c is measured at multiple measurement points, and a determination is made as to whether the workpiece-corresponding target portion 131a has the maximum width. If the workpiece-corresponding target portion 131a has the maximum width, a further determination is made as to whether the distribution of the width dimension T11 is a uniform mountain-shaped distribution. If both determination results are YES, the process proceeds to the next jig / workpiece replacement step (S16). If either determination result is NO, the focus drive step (S13) and focus determination step (S14) are repeated.

[0041] The focus driving step (S13) and the focus determination step (S14) are replaced by a focus adjustment step (S15) that adjusts the focus based on the second jig photographed image G12 so that the workpiece corresponding target portion 131a is included within the range A12 of the depth of field. Upon completion of this focus adjustment step (S15), photographing of the focus confirmation jig 13 since the jig photographing step (S12) is completed.

[0042] In the jig / workpiece replacement step (S16) following the focus adjustment step (S15), the focus confirmation jig 13 is removed from the photography area A11, and the twisted shielded pair electric wire W1 is placed as the workpiece in the photography area A11 by being held by the electric wire chuck unit 122. At this time, the positioning is such that the photographed portion of the twisted shielded pair electric wire W1 is positioned at the target position adjusted by the processing in the focus adjustment step (S15) to be included within the depth of field range A12. Then, a workpiece photography step (S17) is performed in which the photography unit 15 photographs the twisted shielded pair electric wire W1 thus positioned, and an image inspection step (S18) is performed in which various inspections are performed by image analysis of the photography results.

[0043] According to the image inspection device 1 and image inspection method of the first embodiment described above, focus adjustment is performed based on the second jig photographed image G12 of the focus confirmation jig 13, which is placed in the photographing area A11 prior to the workpiece. This adjustment is performed by the focus adjustment unit 171, without user intervention, by adjusting the focus so that the workpiece-corresponding target portion 131a of the focus confirmation jig 13 is included within the depth of field range A12 of the photographing unit 15. Because the focus adjustment unit 171 performs this focus adjustment in advance based on the second jig photographed image G12, the target position that includes the workpiece placement position within the depth of field range A12 does not change even if the workpiece is photographed repeatedly thereafter. In other words, according to this embodiment, the focus adjustment accuracy can be stabilized.

[0044] In this embodiment, the second jig photographed image G12 for adjusting the focus is a silhouette image photographed under illumination with only background light from the second illumination unit 16. With this configuration, it is possible to clearly distinguish between in-focus and out-of-focus edge portions in the second jig photographed image G12, thereby further stabilizing the focus adjustment accuracy.

[0045] In this embodiment, the focus adjustment unit 171 adjusts the focus so that the width dimension T11 of the high-density image portion G12-2c in the workpiece-corresponding target portion 131a in the second jig photographed image G12 becomes the maximum width. According to this configuration, the focus can be adjusted effectively based on the width dimension T11 of the high-density image portion G12-2c.

[0046] Furthermore, in this embodiment, the focus adjustment unit 171 adjusts the focus so that the distribution of the width dimension T11 becomes a uniform mountain-shaped distribution with the workpiece-corresponding target portion 131a at its apex. According to this configuration, by bringing the distribution of the width dimension T11 closer to a uniform mountain-shaped distribution, the workpiece-corresponding target portion 131a can be brought closer to the center of the depth of field range, thereby improving the accuracy of focus adjustment.

[0047] In this embodiment, the focus confirmation jig 13 has a step shape in which the position of the confirmed portion 131 in the depth direction D13 changes stepwise in a predetermined direction (strip length direction D15). According to this configuration, the workpiece corresponding target portion 131a can be easily set by selecting one step from a plurality of steps forming the step shape.

[0048] This concludes the description of the first embodiment, and next we will describe the second embodiment. The second embodiment differs from the first embodiment in the shape of the jig used to adjust the focus. Below, this second embodiment will be described, focusing on the differences from the first embodiment. Note that illustrations and descriptions of the configuration of the image inspection device 1 and the image inspection method, which are equivalent to those of the first embodiment, will be omitted, but the following description will refer to the various components shown in Figures 1 to 9 as appropriate.

[0049] Fig. 10 is a perspective view showing a focus confirmation jig according to the second embodiment, and Fig. 11 is a schematic diagram showing a jig photographed image obtained by photographing the focus confirmation jig shown in Fig. 10. Fig. 11(A) shows a first jig photographed image G21 obtained under illumination with both illumination light from the ring illumination 142 of the first illumination unit 14 and background light from the second illumination unit 16. Fig. 11(B) shows a second jig photographed image G22 obtained under illumination with only background light from the second illumination unit 16. Fig. 12 is a graph equivalent to Fig. 8 relating to the first embodiment, showing how focus is adjusted by the focus adjustment unit.

[0050] The focus confirmation jig 23 in this embodiment is a rectangular block-shaped member roughly equivalent to the focus confirmation jig 13 in the first embodiment. However, in this embodiment, the confirmation target portion 231 that faces the photographing unit 15 when placed in the photographing area A11 has a shape different from that in the first embodiment. That is, the confirmation target portion 231 in the focus confirmation jig 23 has a flat slope shape in which the position in the depth direction D13 of the depth of field of the photographing unit 15 changes continuously in a predetermined direction (strip length direction D15). Furthermore, the block thickness of the focus confirmation jig 23 is slightly thicker than that of the focus confirmation jig 13 in the first embodiment, and the gradient of the flat slope shape is greater than the stepped gradient of the focus confirmation jig 13.

[0051] The first jig photographed image G21 obtained by photographing such a focus confirmation jig 23 is a simple rectangular image of the confirmed portion 231 without divisions in the strip length direction D15, as shown in Fig. 11(A). Also, as shown in Fig. 11(B), the second jig photographed image G22 is a silhouette image substantially equivalent to that of the first embodiment.

[0052] In graph C21 of Fig. 12, the horizontal axis indicates the measurement position (mm) of the width dimension of the high-density image portion in second jig-captured image G22, and the vertical axis indicates the width dimension (mm). However, unlike the horizontal axis of graph C11 of Fig. 8 in the first embodiment, the measurement position indicated on the horizontal axis is the height dimension from the bottom surface of focus confirmation jig 23. Furthermore, the width dimension indicated on the vertical axis is larger than width dimension T11 on the vertical axis of graph C11 of Fig. 8 in the first embodiment, depending on the thickness of focus confirmation jig 23.

[0053] In this embodiment, the target portion 231 of the focus confirmation jig 23 has a flat, inclined surface shape, enabling width measurement at any position in the depth direction D13 of the depth of field. Accordingly, in this embodiment, width measurements are performed at multiple measurement points with shorter measurement intervals than in the first embodiment. The width measurement results at these multiple measurement points are plotted in graph C21 of FIG. 12. The maximum width, which is the apex of the width distribution in this graph C21, is measured for the workpiece-corresponding target portion 231a, and the focus is adjusted so that the distribution becomes a uniform mountain-shaped distribution. Note that the target portion 231 of the focus confirmation jig 23 in this embodiment does not have a shape that serves as a guide for setting the workpiece-corresponding target portion 231a, such as the stair-shaped steps of the target portion 131 in the first embodiment. Therefore, the focus confirmation jig 23 has two through-holes 232 in the depth direction D13, arranged side by side in the strip length direction D15, as a guide for this position.

[0054] It goes without saying that in the second embodiment described above, as in the first embodiment, the focus adjustment accuracy can be stabilized by adjusting the focus in advance using the focus confirmation jig 23.

[0055] In this embodiment, the confirmed portion 231 of the focus confirmation jig 23 has a flat inclined surface shape. With this configuration, the flat inclined surface shape allows measurement of the width dimension at any measurement point in the depth direction D13 of the depth of field, thereby improving the resolution of focus adjustment.

[0056] Next, a third embodiment will be described. In the third embodiment, the shape of the jig used for adjusting the focus is also different from that in the first embodiment, and the following description of the third embodiment will focus on the differences from the first embodiment. Note that, in the third embodiment as well, illustrations and descriptions of the configuration of the image inspection device 1 and the image inspection method, which are equivalent to those in the first embodiment, will be omitted, and the description will be made with appropriate reference to the various components shown in Figures 1 to 9.

[0057] Fig. 13 is a perspective view showing a focus confirmation jig according to the third embodiment, and Fig. 14 is a schematic diagram showing a jig photographed image obtained by photographing the focus confirmation jig shown in Fig. 13. Fig. 14(A) shows a first jig photographed image G31 obtained under illumination with both the illumination light from the ring illumination 142 of the first illumination unit 14 and the background light from the second illumination unit 16. Fig. 14(B) shows a second jig photographed image G32 obtained under illumination with only the background light from the second illumination unit 16.

[0058] The focus confirmation jig 33 in this embodiment includes a protruding base portion 332 and a plurality of protrusions 333. The protruding base portion 332 includes a rectangular main body plate 332a, the long side of which faces the imaging unit 15 when placed in the imaging area A12 and is formed in a stepped shape, and a pair of legs 332b that hold both ends of the main body plate 332a. The focus confirmation jig 33 is installed so that the pair of legs 332b rests on the imaging area A12.

[0059] A plurality of protrusions 333 are attached one-to-one to a plurality of steps in the stepped portion of the main body plate 332a. In the focus checking jig 33, these plurality of protrusions 333 form a checked portion 331 for adjusting the focus. The plurality of protrusions 333 are arranged in a predetermined direction (strip length direction D15) with each protruding toward the imaging unit 15, and the apex positions of the hemispherical tip portions 333a change stepwise in the depth direction D13 of the depth of field.

[0060] As shown in FIG. 14(A), the first jig photographed image G31 obtained by photographing such a focus confirmation jig 33 is an image in which the hemispherical tips 333a of multiple protrusions 333 are lined up in a row in the strip length direction D15 on the top of the protrusion base portion 332. Also, as shown in FIG. 11(B), the second jig photographed image G32 is a silhouette image in which the inside of the outline of the first jig photographed image G31 is blackened. In this embodiment, the diameter of the protrusions 333 is longer than the thickness of the main plate 332a of the protrusion base portion 332. Therefore, in the silhouette image of the second jig photographed image G22, a portion of the outer periphery of each protrusion 333 protrudes from the main plate 332a in the thickness direction D31. As a result, the position of each protrusion 333 is clearly visible in the silhouette image of the second jig photographed image G22. In this embodiment, when adjusting the focus, one of the plurality of protrusions 333 is set as the workpiece corresponding target portion 331a. In Fig. 14, as an example, the protrusion 333 located in the center of the arrangement is set as the workpiece corresponding target portion 331a.

[0061] In this embodiment, the width dimension T31 in the width direction D31, which is perpendicular to both the depth direction D13 and the band length direction D15, is measured for the silhouette portion G221 of each of the multiple protrusions 333 in the second jig photographed image G22. As in the first and second embodiments, the width dimension T31 is the width dimension of the high-density image portion excluding the low-density edge portion. The measurement results are represented by discrete plotted points, similar to those shown in graph C11 of FIG. 8. Based on the measurement results of these discrete plotted points, the focus is adjusted so that the width dimension T31 of the preset workpiece-corresponding target portion 331a becomes the maximum width and the distribution of the width dimensions T31 becomes a uniform mountain-shaped distribution.

[0062] It goes without saying that, in the third embodiment described above, as in the first embodiment, the focus adjustment accuracy can be stabilized by adjusting the focus in advance using the focus confirmation jig 33.

[0063] In this embodiment, the confirmed portion 331 of the focus confirmation jig 33 has an array of multiple protrusions 333, and the tip position of each protrusion changes stepwise in the depth direction D13. With this configuration, by selecting one protrusion 333 from the multiple protrusions 333, the workpiece corresponding target portion 331a for focus adjustment can be easily set.

[0064] The first to third embodiments described above are merely representative examples of the image inspection device. The image inspection device and image inspection method are not limited to these, and can be implemented in various modifications.

[0065] For example, in the first to third embodiments described above, an image inspection device 1 that photographs a twisted shielded pair electric wire W1 as a work and performs various inspections is exemplified as an example of an image inspection device. However, the image inspection device is not limited to these, and may photograph and inspect an electric wire other than a twisted shielded pair electric wire or any member other than an electric wire as a work. Furthermore, although the first to third embodiments do not specify specific inspection contents, the specific inspection contents are not important as long as inspection is performed based on a photographed image of the work.

[0066] Furthermore, in the above-described first to third embodiments, as an example of an image inspection device, an image inspection device 1 is exemplified in which the irradiation light in the shooting direction D14 is performed by the ring illumination 142 and the background light is performed 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.

[0067] Furthermore, in the above-described first to third embodiments, the focus adjustment unit 171 is exemplified as an example of a focus adjustment unit, which adjusts the focus based on the second jig photographed images G12, G22 captured as silhouette images under illumination with only background light. However, the focus adjustment unit is not limited to this, and may adjust the focus based on a jig photographed image captured under illumination with only illumination light from the photographing direction, or under illumination with both this illumination light and background light. However, as described above, by adjusting the focus based on the second jig photographed images G12, G22 captured as silhouette images, the accuracy of focus adjustment can be further stabilized.

[0068] Furthermore, in the above-described first to third embodiments, as an example of a focus adjustment unit, a focus adjustment unit 171 is exemplified which adjusts the focus so that the width dimension T11 of the high-density image portion G12-2c in the work-corresponding target portion 131a becomes the maximum width. However, the focus adjustment unit is not limited to this, and any specific adjustment mode is acceptable as long as it adjusts the focus so that the work-corresponding target portion is included within the depth of field of the imaging unit. However, as described above, by adjusting the focus so that the width dimension T11 of the work-corresponding target portion 131a becomes the maximum width, it is possible to effectively adjust the focus.

[0069] Furthermore, in the above-described first to third embodiments, the focus adjustment unit 171 is exemplified as an example of a focus adjustment unit, which adjusts the focus so that the distribution of the width dimension T11 becomes a uniform mountain-shaped distribution with the workpiece corresponding target portions 131a, 231a, and 331a at the apex. However, the focus adjustment unit is not limited to this, and the focus may be adjusted without depending on the distribution shape of the width dimension. However, as described above, by adjusting the focus based on the distribution shape of the width dimension T11, the accuracy of the focus adjustment can be improved.

[0070] Furthermore, in the first to third embodiments described above, the following is given as an example of the focus confirmation jig. That is, in the first embodiment, a focus confirmation jig 13 in which the confirmation target portion 131 has a staircase shape is given as an example, and in the second embodiment, a focus confirmation jig 23 in which the confirmation target portion 131 has a flat slope shape is given as an example. Furthermore, in the third embodiment, a focus confirmation jig 33 in which the confirmation target portion 331 is formed by an array of multiple protrusions 333 is given as an example. However, the specific shape of the focus confirmation jig can be set arbitrarily as long as the confirmation target portion facing the imaging unit has a shape in which the position in the depth direction of the depth of field changes stepwise or continuously. However, as described above, the focus confirmation jig 13 in which the confirmation target portion 131 has a staircase shape and the focus confirmation jig 33 in which the confirmation target portion 331 has an array of multiple protrusions 333 make it easy to set the workpiece corresponding target portions 131a, 331a. Furthermore, as described above, the focus checking jig 23 in which the checked portion 131 has a flat inclined surface shape can improve the resolution of focus adjustment. [Explanation of symbols]

[0071] 1. Image inspection equipment 11 Stand Frame 12 Workpiece holder 13,23,33 Focus check jig 13a Reference position 14 First Lighting Section 15 Photography Department 16 Second Lighting Section 17 Processing section 111 Base part 112 Support column part 121 Plate section 121a Rectangular window 122 Wire chuck part 122a First chuck 122b Second chuck 131,231,331 Confirmed part 131a, 231a, 331a Work Target Section 141 Lighting retaining plate 141a Support part 141b Lighting fixed part 141c Photo window 142 Ring Light 151 Camera holder 152 Cameras 153 Camera Lens 161 Light-emitting surface 171 Focus adjustment unit 232 Through hole 332 Protruding base part 332a body plate 332b Legs 333 Protrusions 333a Tip A11 Photo Area A12 Depth of Field Range A121 Lower limit position A122 Upper limit position B11 area C11,C21 graph D11 Length direction D12 Chuck direction D13 Depth direction D14 Shooting direction D15 Band length direction D31 Thickness direction G11, G21, G31 First jig photograph image G12, G22, G32 2nd jig photograph image G12-1, G12-2 images G12-1a, G12-2a Edge G12-2b Low density edge area G12-2c High density image area S11 Jig placement process S12 Jig photography process S13 Focus drive process S14 Focus determination process S15 Focus adjustment process S16 Jig / Workpiece exchange process S17 Work photography process S18 Image inspection process T11 width dimension W1 Twisted shielded pair wire (work) W11 Electric wire W12 Exposed conductor W13 Outermost covering part

Claims

1. an imaging unit that images a predetermined imaging area; A focus confirmation jig is a jig that is placed in the photography area prior to the workpiece to be inspected and is used to confirm in advance the focus of photography of the workpiece by the photography unit, and the part that faces the photography unit when placed in the photography area is a confirmed part having a shape in which the position in the depth direction of the depth of field of the photography unit changes stepwise or continuously; a focus adjusting unit that adjusts the focus based on a jig photographed image of the focus confirmation jig placed in the photographing area photographed by the photographing unit so that a workpiece corresponding target portion corresponding to the placement position of the workpiece in the confirmed portion is included within the range of the depth of field in the photographing unit; An image inspection device comprising:

2. a first lighting unit that irradiates the photographing area with illumination light from a photographing direction of the photographing unit; a second illumination unit disposed on the opposite side of the photographing unit as viewed from the photographing area, and configured to irradiate background light onto the photographing unit through the photographing area; 2. The image inspection device according to claim 1, wherein the jig photographed image is a silhouette image of the focus confirmation jig photographed by the photographing unit under illumination with only the background light from the second illumination unit.

3. When the focus confirmation jig is placed in the photographing area, it has a band shape in a plan view seen from the photographing unit, and the position in the depth direction of the band shape changes stepwise or continuously in the band length direction, and any part in the band length direction is set as the work corresponding target portion, The image inspection device described in claim 1, characterized in that the focus adjustment unit measures the width dimension of the high-density image portion in the jig-captured image, excluding the low-density edge portion where the image density has decreased to a predetermined level or more due to focus deviation, at multiple locations in the band length direction, and adjusts the focus so that the work-corresponding target portion has the maximum width.

4. The image inspection device described in claim 3, characterized in that the focus adjustment unit adjusts the focus so that the distribution of the width dimensions of the high-density image portion in the band length direction becomes an even mountain-shaped distribution with the work-corresponding target portion as its apex.

5. 2. The image inspection device according to claim 1, wherein the portion to be confirmed in the focus confirmation jig has a stepped shape in which the position in the depth direction changes stepwise in a predetermined direction.

6. 2. The image inspection device according to claim 1, wherein the portion to be confirmed in the focus confirmation jig has a flat slope shape in which the position in the depth direction changes continuously in a predetermined direction.

7. 2. The image inspection device according to claim 1, wherein the confirmed portion in the focus confirmation jig has a plurality of protrusions arranged in a predetermined direction, each of which protrudes toward the imaging portion in the depth direction, and the tip positions of the plurality of protrusions change in stages in the depth direction.

8. a jig placement step of placing the focus confirmation jig in the imaging area of ​​the image inspection device according to any one of claims 1 to 7; a jig photographing step in which the photographing unit photographs the focus confirmation jig in the photographing area; a focus adjustment step in which the focus adjustment unit adjusts the focus based on the jig photographed image so that a workpiece corresponding target portion corresponding to the placement position of the workpiece in the confirmed portion is included within the range of the depth of field in the photographing unit; An image inspection method comprising:

Images