Inspection system

Abstract

We provide an inspection system that enables the detection of slight dents inexpensively, quickly, and with high accuracy. [Solution] The inspection system 100 is a system for inspecting the surface (inspection surface Wa) of a workpiece W. The inspection system 100 includes a camera 20 (imaging unit) that images the surface of the workpiece W, a surface illuminator 30 (illumination unit) positioned opposite the camera 20 and irradiating light onto the workpiece W, and an electric actuator 40 (operating unit) that operates the surface illuminator 30 to move it. The workpiece W is positioned between the camera 20 and the surface illuminator 30 and is tilted with respect to the axis of the camera 20. The camera 20 continuously images the surface of the workpiece W while maintaining the relative positions of the camera 20 and the workpiece W, and while the electric actuator 40 is operating the surface illuminator 30. The electric actuator 40 moves the surface illuminator 30 perpendicular to the axis of the camera 20 and in a horizontal direction.

Description

Technical Field

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[0001] The present invention relates to an inspection system.

Background Art

[0002] As a conventional technique, a technique such as Patent Document 1 is disclosed.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As conventional techniques, various techniques have been proposed, but an inspection system capable of detecting loose depressions at low cost, high speed, and high accuracy is desired.

[0005] Therefore, an object of the present invention is to provide an inspection system capable of detecting loose depressions at low cost, high speed, and high accuracy.

Means for Solving the Problems

[0006] The present invention employs the following solution means. Note that the following solution means are merely examples, and the present invention is not limited thereto. Further, the present invention can be an invention including at least one of the invention specific matters shown in the following solution means. Furthermore, elements limiting the invention specific matters can be added to the invention specific matters shown in the following solution means to lower the concept, and elements limiting the invention specific matters can be deleted to raise the concept.

[0007] The inspection system for the solution is, for example, an inspection system for inspecting the surface of a workpiece, comprising: an imaging unit for imaging the surface of the workpiece; an illumination unit positioned opposite the imaging unit and irradiating the workpiece with light; and an operating unit for operating the illumination unit, wherein the workpiece is positioned between the imaging unit and the illumination unit and is tilted with respect to the axis of the imaging unit, and the imaging unit continuously images the surface of the workpiece while maintaining the relative positions of the imaging unit and the workpiece, and while the operating unit is operating the illumination unit. [Effects of the Invention]

[0008] According to the present invention, an inspection system can be provided that enables the detection of slight dents inexpensively, quickly, and with high accuracy. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing the inspection system 100 of the embodiment. [Figure 2] This is a plan view (top view) showing the inspection system 100 of the embodiment. [Figure 3] This is a side view (side perspective) of the inspection system 100 of the embodiment. [Figure 4] This figure shows other configurations (other layouts) of the inspection system 100. [Figure 5] This figure shows the results of continuous imaging by camera 20. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. The following embodiments are shown as preferred examples of inspection systems, and embodiments are not limited to these examples.

[0011] Figure 1 is a perspective view showing the inspection system 100 of an embodiment. The inspection system 100 is a system for inspecting the surface of the workpiece W. Workpiece W is, for example, a cell case (aluminum pressed) for lithium-ion batteries used in hybrid and electric vehicles. Workpiece W is a hollow case with an open top, a bottom, and four sides. Workpiece W measures approximately 70mm in length, 300mm in width, and 40mm in thickness. However, Workpiece W is not limited to metal; it can be applied to any shape or material.

[0012] The inspection system 100 comprises a holding member 10, a camera 20 (imaging unit), a surface illuminator 30 (illumination unit, light source), and an electric actuator 40. The inspection system 100 performs a visual inspection of the workpiece W.

[0013] The holding member 10 is a member that holds the workpiece W. The holding member 10 has a column member 11 that extends in the vertical direction, and supports the workpiece W with an L-shaped member 12 positioned at the top of the column member 11. The workpiece W is a plate-shaped member and is positioned upright with the opening on its upper surface facing downwards.

[0014] Camera 20 is a device that images the surface of the workpiece W (inspection surface Wa). The image of the surface of the workpiece W (inspection surface Wa) captured by camera 20 is stored in memory (not shown).

[0015] The surface illuminator 30 is positioned facing the camera 20 and is a device that illuminates the workpiece W with light. The surface illuminator 30 has a light-emitting surface 31 that is wider (length L2 in the left-right direction) than the thickness (length L1) of the workpiece W. The size, shape, and position of the camera 20 and the surface illuminator 30 can be changed as needed.

[0016] The electric actuator 40 is a device that operates to move the surface illumination 30. Specifically, the electric actuator 40 includes a motor (not shown), and by driving this motor, the slide member 42 can be moved left and right along the guide member 41. Since the slide member 42 is fixed to the lower part of the surface illumination 30, the electric actuator 40 can drive the motor to move the surface illumination 30 left and right (in the horizontal direction).

[0017] FIG. 2 is a plan view (top view) showing the inspection system 100 of the embodiment. FIG. 3 is a side view (side view) showing the inspection system 100 of the embodiment. As shown in FIGS. 2 and 3, the workpiece W is disposed between the camera 20 and the surface illumination 30 and is inclined with respect to the axis C (optical axis, camera axis) of the camera 20. Specifically, the workpiece W is disposed at a predetermined angle θ with respect to the axis C of the camera 20. The predetermined angle θ is preferably, for example, 5 to 15 degrees.

[0018] The camera 20 continuously images (successively images) the surface of the workpiece W (the region including the inspection surface Wa) while maintaining the relative positions of the camera 20 and the workpiece W (for example, in a state where the camera 20 and the workpiece W are not moved, or in a state where the positions of the camera 20 and the workpiece W are maintained even if they are moving), and while the electric actuator 40 is operating the surface illumination 30. For example, an encoder pulse signal emitted from the electric actuator 40 may be used for continuous imaging, and it may be a continuous description with invariability at equal intervals.

[0019] The electric actuator 40 moves the surface illumination 30 vertically with respect to the axis C of the camera 20 and in the horizontal direction (see arrow A). Before the imaging by the camera 20 starts, the electric actuator 40 disposes the surface illumination 30 at the initial position. During the imaging by the camera 20, the electric actuator 40 moves the surface illumination 30 by a predetermined amount (for example, about 40 mm) from the initial position toward the final position. After the imaging by the camera 20 ends, the electric actuator 40 moves the surface illumination 30 from the final position toward the initial position (returns the surface illumination 30 to the original position). Note that the predetermined amount and the predetermined angle θ can be arbitrarily changed according to the shape of the workpiece W, the arrangement positions of the workpiece W, the camera 20, the surface illumination 30, and the like.

[0020] As described above, the inspection system 100 includes a camera 20 that captures an image of the inspection surface Wa of the plate-shaped workpiece W to be inspected, a surface illumination 30 that serves as a light source, and a one-axis electric actuator 40 that operates the surface illumination 30. The plate-shaped workpiece W to be inspected is arranged at a predetermined angle θ with respect to the axis C of the camera 20. Then, while moving the surface illumination 30 in the direction of arrow A by a predetermined amount with the electric actuator 40, continuous imaging is performed with the camera 20.

[0021] As shown in FIG. 2, when the inspection system 100 is viewed from above, the workpiece W is arranged at a predetermined angle θ with respect to the axis C of the camera 20. Therefore, as shown in FIG. 3, when the inspection system 100 is viewed from the side, the workpiece W is in a state where the inspection surface Wa is directed toward the camera 20 by the amount of the predetermined angle θ.

[0022] FIG. 4 is a diagram showing another configuration (another layout) of the inspection system 100. The inspection system 100 with another configuration includes a transport pallet 50 (transport unit) that transports the workpiece W. The transport pallet 50 can be arranged in place of the holding member 10. The transport pallet 50 is a flat rectangular parallelepiped member that transports the workpiece W. The transport pallet 50 includes wheels or the like (not shown) for moving on a rail (not shown). In addition, two pins (not shown) are provided on the transport pallet 50, and the opening on the upper surface of the workpiece W is fitted into and fixed to the two pins.

[0023] The transport pallet 50 is fixed on a transport conveyor (pitch conveyor) (not shown) and transported by pitch. The cycle time for pitch transport is, for example, about 1.3 seconds, and the transport conveyor repeats intermittent operations such as stopping for about 0.7 seconds and moving for about 0.6 seconds. Imaging by the camera 20 is performed during the stop time of pitch transport. The workpiece W is transported from the top to the bottom in the figure by pitch transport, and while the workpiece W reaches the central position (the third position from the top in the figure) and stops, light is irradiated by the surface illumination 30, the surface illumination 30 is moved by the electric actuator 40, and continuous imaging is performed by the camera 20. The surface illumination 30 may continue to emit light, or it may only emit light at the timing of imaging.

[0024] Furthermore, in the example shown in Figure 4, one side of the workpiece W in the longitudinal direction (inspection surface Wa) is being imaged. Although not specifically shown, the other side of the workpiece W in the longitudinal direction, and the front and rear sides of the workpiece W in the short direction can also be imaged in a separate process. This allows for inspection of all four sides (front, rear, left, and right) of the workpiece W.

[0025] In other configurations of the inspection system 100, the inspection surface Wa of the workpiece W is perpendicular to the transport direction B in which the transport pallet 50 transports the workpiece W. Also, the camera 20 and surface illumination 30 are tilted with respect to the transport direction B (tilted by a predetermined angle θ with respect to a direction perpendicular to the transport direction B). The predetermined angle θ is the same as the angle described above, and is preferably, for example, 5 to 15 degrees.

[0026] Figure 5 shows the results of continuous imaging by camera 20. Figure 5(A) shows the actual workpiece W, and Figures 5(B) to 5(F) show the results of continuous imaging by the camera 20. In the illustrated example, five images (Figures 5(B) to 5(F)) are shown as the result of continuous imaging, but in reality, it is possible to capture tens to hundreds of images of one inspection surface Wa of one workpiece W during the pitch transport stop time. By obtaining multiple images with different imaging angles in less than one second or a few seconds, it becomes possible to detect slight dents and other defects quickly and with high accuracy.

[0027] As shown in Figure 5(A), the inspection surface Wa of the actual workpiece W has three gentle indentations D1 to D3 (see circles in the figure). Specifically, gentle indentation D1 is located on the front side of the upper section of the inspection surface Wa. Gentle indentation D2 is located near the center of the middle section of the inspection surface Wa. Gentle indentation D3 is located on the back side of the lower section of the inspection surface Wa.

[0028] As shown in Figure 5(B), in the first image (for example, an image taken at an illumination position where light is specularly reflected), contrast is not obtained, making it difficult to detect a slight depression. As shown in Figure 5(C), the second image has better contrast than the first image, making it possible to detect the slight indentations D1-D3. As shown in Figure 5(D), in the third image, the gentle indentation D1 in the upper section is easily detectable. As shown in Figure 5(E), in the fourth image, the gentle indentation D2 in the middle section is easily detectable. As shown in Figure 5(F), in the fifth image, the gentle indentation D3 in the lower section is easily detectable. Note that the number of images required to easily detect a slight indentation varies depending on the individual workpiece W and the imaging environment.

[0029] In this way, by gradually moving the surface illumination 30, the camera 20 can clearly image the slight indentation. Then, by using the obtained image for image determination by an image determination unit (not shown), the detectability of the slight indentation can be improved.

[0030] As described above, this embodiment has the following advantages. (1) According to this embodiment, the camera 20 continuously images the inspection surface Wa of the workpiece W while maintaining the relative position of the camera 20 and the workpiece W, and while the electric actuator 40 is operating the surface illumination 30, thus enabling the detection of slight dents inexpensively, quickly, and with high accuracy.

[0031] (2) According to this embodiment, the electric actuator 40 moves the surface illumination 30 perpendicular to the axis C of the camera 20 and in a horizontal direction, so the illumination angle can be easily changed and gentle depressions can be clearly imaged. In this embodiment, the surface illumination 30 is moved without moving the camera 20 and the workpiece W. However, even when the workpiece W was moved without moving the camera 20 and the surface illumination 30, it was not possible to clearly image the gentle depressions. One reason for this is that illumination is linear and also diffuse, so moving the illumination changes the illuminance profile more easily than moving the workpiece W, making it easier to clearly image the gentle depressions. In experiments conducted by the inventors, when the workpiece W was moved (unless the relative positions of the camera 20 and the workpiece W were maintained), the gentle depressions could not be clearly imaged, but when the surface illumination 30 was moved (while the relative positions of the camera 20 and the workpiece W were maintained), the gentle depressions could be clearly imaged.

[0032] (3) According to this embodiment, the workpiece W is positioned at an angle of 5 to 15 degrees with respect to the axis C of the camera 20, so that the angle can be set within this range to make it easier to detect slight indentations. If the angle is less than 5 degrees, the imaging range may become too narrow, and if it is greater than 15 degrees, the workpiece W may be facing the camera 20 too much, making it difficult to detect slight indentations.

[0033] (4) According to this embodiment, the surface illumination 30 has a light-emitting surface 31 that is wider (length L2 in the left-right direction) than the thickness (length L1) of the workpiece W. By making the surface illumination 30 wide, the light from the surface illumination 30 can be sufficiently irradiated onto the inspection surface Wa, making it easier to detect slight indentations.

[0034] (5) According to this embodiment (another configuration of the inspection system 100), the inspection surface Wa of the workpiece W is perpendicular to the transport direction B in which the transport pallet 50 transports the workpiece W, so the workpiece W can be transported efficiently in a straight line.

[0035] (6) Mild dents and scratches are difficult to detect with non-contact inspection. Generally, with cameras, defect inspection is performed by facing the inspection surface and using coaxial incident illumination or low-angle illumination, but the contrast between light and dark is poor, and high detection accuracy cannot be achieved. In addition, there is a known method of performing three-dimensional inspection by scanning the inspection surface with a two-dimensional displacement sensor, but the high cost of building the system and the time required for scanning are bottlenecks.

[0036] Therefore, in this embodiment, continuous imaging is performed while moving the surface illumination 30 with an electric actuator 40, so as to capture images that are easy to distinguish from good products. This provides the following effects. (a) Automated inspection is possible with a relatively inexpensive configuration. (b) It is effective for detecting slight dents on flat surfaces, but depending on the position of the surface illumination, it can also be effective for detecting impact marks, scratches, etc. (c) Since the inspection image can be handled by the camera's imaging conditions, the detection performance is not affected by the material or surface roughness of the object being inspected. (d) There is a degree of flexibility in the size of the object being inspected. (e) Inspection can be performed while the object is being transported, and it is easy to apply to equipment that transports the workpiece W at high speed. (f) For mild indentation defects that are difficult to detect, inspection with fewer misjudgments can be achieved.

[0037] (7) When performing an automatic visual inspection of slight indentations on a metal surface using image inspection, the inspection surface Wa of the workpiece W is tilted slightly with respect to the axis C of the camera 20, and the surface illumination 30 installed behind it is operated perpendicular to the axis C of the camera 20, so that the inspection surface Wa of the workpiece W is continuously imaged by the camera 20. As a result, a high-contrast image sufficient for defect detection can be obtained compared to the conventional known method of facing the inspection surface of the workpiece directly with the camera. The intention of continuously imaging while the surface illumination 30 is operating is to address the variability and diversity of the indentation patterns that constitute the defects.

[0038] (8) In recent years, most equipment is equipped with an image inspection process, so by introducing the inspection system 100 described above, the quality of the workpiece W can be further improved. The inspection system 100 is particularly suitable for visual inspection of workpieces W that have a flat surface. In addition to workpieces W that have a flat surface, workpieces with curved surfaces can also be inspected. For example, the surface of a curved cylindrical rod-shaped workpiece can also be inspected. However, if the curvature of the curved surface is sharp, reflected light may escape from areas other than the top where light is easily shone, so inspection is possible only in limited areas such as the top. Also, if the curvature of the curved surface is gentle, inspection is possible.

[0039] (9) The technology described in Patent Document 1 above involves illuminating the workpiece surface at a shallow angle and imaging it at a shallow angle on the other side. However, Patent Document 1 does not describe how to operate the surface illumination or how to tilt the workpiece.

[0040] [Transformed form] The present invention can be implemented in various ways without being limited to the embodiments described above. (1) The operation unit was described in an example where the illumination unit is moved perpendicular to the axis of the imaging unit and horizontally, but the movement of the operation unit is not limited to this. The operation unit may move the illumination unit forward and backward, left and right, diagonally, or rotate the illumination unit. (2) The inspection system can also detect scratches and other damage in addition to minor dents. (3) The predetermined angle θ for tilting the workpiece may be 1 degree or more and less than 4 degrees, or 16 degrees or more and less than 90 degrees. The predetermined angle θ can be freely changed according to the shape of the workpiece.

[0041] (4) The lighting unit may be a type of lighting other than surface lighting. The width of the light-emitting surface of the surface lighting can be set arbitrarily. (5) The inspection system does not need to have a transport unit. (6) The images captured by the imaging unit may be used for image determination (image processing) by an image determination unit (not shown), or they may be stored in a database so that the user can check them.

[0042] (7) The vertical, horizontal, and orthogonal directions do not need to be perfect; they may be approximately vertical, approximately horizontal, and approximately orthogonal, with a deviation of about plus or minus 5 degrees. [Explanation of Symbols]

[0043] 10 Retaining member 11 Column members 12 L-shaped member 20 cameras 30-sided lighting 31 Light-emitting surface 40 Electric Actuators 41 Guide member 42 Sliding member 50 transport pallets 100 Inspection Systems C Camera axis D1, D2, D3: Slight dents L1 Workpiece thickness L2 Length of the light-emitting surface in the left-right direction Double job Wa Inspection Surface

Claims

1. An inspection system for inspecting the surface of a workpiece, An imaging unit for imaging the surface of the workpiece, An illumination unit is positioned opposite the imaging unit and irradiates light onto the workpiece, It comprises an operating unit that causes the lighting unit to move, The workpiece is positioned between the imaging unit and the illumination unit, and is positioned at an angle with respect to the axis of the imaging unit. The inspection system is characterized in that the imaging unit continuously images the surface of the workpiece while maintaining the relative position between the imaging unit and the workpiece, and while the operating unit is operating the illumination unit.

2. In the inspection system described in claim 1, The inspection system is characterized in that the operating unit moves the illumination unit perpendicular to the axis of the imaging unit and horizontally.

3. In the inspection system described in claim 1, The inspection system is characterized in that the workpiece is positioned at an angle of 5 to 15 degrees with respect to the axis of the imaging unit.

4. In the inspection system described in claim 1, The aforementioned workpiece is a plate-shaped member, and is positioned upright. The inspection system is characterized in that the illumination unit is a surface illumination unit having a light-emitting surface wider than the thickness of the workpiece.

5. In the inspection system described in claim 1, The system includes a transport unit for transporting the aforementioned workpiece, The inspection surface of the workpiece is perpendicular to the transport direction in which the transport unit transports the workpiece. An inspection system characterized in that the imaging unit and the illumination unit are inclined with respect to the transport direction.

Images