Appearance inspection device and appearance inspection method

Abstract

To provide an appearance inspection device that can shorten an inspection time when inspecting multiple surfaces of an object to be inspected.SOLUTION: The appearance inspection device includes a first imaging apparatus, three or more first lighting devices, a second imaging apparatus, three or more second lighting devices, a control unit, and an image processing unit. The control unit alternately performs first imaging processing and second imaging processing. The first imaging processing includes imaging a first surface of an object to be inspected by the first imaging apparatus while light from one of the first lighting devices is applied onto the object to-be-inspected. The second imaging processing includes imaging a second surface of the object to be inspected by the second imaging apparatus while light from one of the second lighting devices is applied onto the object to be inspected. Thereby, a first image set is obtained from the first imaging apparatus and a second image set is obtained from the second imaging apparatus. The image processing unit inspects the first surface of the object to be inspected on the basis of the first image set and inspects the second surface of the object to be inspected on the basis of the second image set.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to an appearance inspection apparatus and an appearance inspection method.

Background Art

[0002] When performing an appearance inspection for detecting a defect having minute unevenness, the illumination difference stereo method is used (see, for example, Patent Document 1). In the appearance inspection using the illumination difference stereo method, three or more images captured by irradiating illumination light from each of three or more directions are synthesized, a normal line of a surface is obtained from the synthesized image, a normal line image representing the inclination of the normal line of the surface is generated, and an appearance inspection of an object to be inspected is performed based on the normal line image.

[0003] In addition, inspections on a plurality of surfaces of an object to be inspected may be performed in a single inspection. In this case, a camera and three or more lighting devices are prepared corresponding to each surface, and an operation of sequentially lighting the lighting devices and photographing with the camera is sequentially performed for each surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The timing for giving a trigger to the camera and the lighting device is after each photographing is completed, and photographing cannot be performed in parallel, so a lot of time is required for the total photographing, and thus the inspection time becomes long.

[0006] The problem to be solved by the present invention is to provide a technique capable of shortening the inspection time when inspecting a plurality of surfaces of an object to be inspected.

Means for Solving the Problems

[0007] An appearance inspection apparatus according to an embodiment includes a first imaging device, a plurality of first lighting devices, a second imaging device, a plurality of second lighting devices, a control unit, and an image processing unit. The first imaging device images a first surface of an inspection object. The plurality of first lighting devices irradiate illumination light onto the first surface of the inspection object from a plurality of first lighting directions. The second imaging device images a second surface of the inspection object. The plurality of second lighting devices irradiate illumination light onto the second surface of the inspection object from a plurality of second lighting directions. The control unit performs, alternately, a first imaging process of imaging the first surface of the inspection object with the first imaging device while illuminating light from one of the plurality of first lighting devices is applied to the first surface of the inspection object, and a second imaging process of imaging the second surface of the inspection object with the second imaging device while illuminating light from one of the plurality of second lighting devices is applied to the second surface of the inspection object, to obtain a first image set including a plurality of images obtained by the first imaging device with illumination light applied from each of the plurality of first lighting directions and a second image set including a plurality of images obtained by the second imaging device with illumination light applied from each of the plurality of second lighting directions. The image processing unit inspects the first surface of the inspection object based on the first image set, and inspects the second surface of the inspection object based on the second image set.

Advantages of the Invention

[0008] According to the present invention, when inspecting a plurality of surfaces of an inspection object, a technique capable of shortening the inspection time can be provided.

Brief Description of the Drawings

[0009]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings.

[0011] The embodiment relates to a technique applicable to appearance inspection performed in a factory or the like. Appearance inspection is performed for the purpose of ensuring the quality of a product (also referred to as a workpiece), for example, and inspects the appearance of the product in order to determine whether the product is a good product or a defective product. For example, a product is determined to be a good product when there are no defects such as scratches or dirt, or when the defects, if any, are within the allowable range, and is determined to be a defective product when there are defects outside the allowable range. Hereinafter, a defect refers to a defect outside the allowable range.

[0012] FIG. 1 is a block diagram schematically showing the functional configuration of an appearance inspection apparatus 100 according to an embodiment, and FIG. 2 is a perspective view schematically showing a part of the appearance inspection apparatus 100. As shown in FIG. 1, the appearance inspection apparatus 100 includes photographing units 15 and 25, optical sensors 41 and 42, and an information processing unit 50.

[0013] As shown in FIG. 2, the imaging unit 15 is provided to face the upper surface 91 of the product 90 as the object to be inspected. The imaging unit 15 includes a camera 10 as an imaging device and three lighting devices 11, 12, and 13.

[0014] The camera 10 captures an image of the product 90 from a certain direction to generate an image. In the example shown in FIG. 2, the camera 10 is directed vertically downward, and imaging by the camera 10 is performed with the product 90 positioned directly below the camera 10. In this case, the upper surface 91 of the product 90 is imaged by the camera 10. In this example, the upper surface 91 of the product 90 is shown as a flat surface, but it is not limited thereto. As the imaging device, for example, a digital camera having a CCD (charge coupled device) image sensor or a CMOS (complementary metal oxide semiconductor) image sensor can be used. The image obtained by the camera 10 is output to the information processing unit 50.

[0015] The lighting devices 11 to 13 are configured to illuminate the product 90 from three different lighting directions. Specifically, the lighting devices 11 to 13 are configured to irradiate illumination light onto the upper surface 91 of the product 90 from three different lighting directions. The lighting devices 11 to 13 are arranged at the same height so as to surround the camera 10. The lighting devices 11 to 13 are arranged at equal intervals on the circumference of a virtual circle centered on a point on the optical axis of the camera 10 and perpendicular to the optical axis of the camera 10. Each of the lighting devices 11 to 13 is directed obliquely downward such that its optical axis intersects the optical axis of the camera 10. As the lighting devices 11 to 13, for example, light emitting diodes (LEDs) or incandescent bulbs can be used.

[0016] In the example shown in FIG. 2, the imaging unit 15 further includes a ring-shaped support member 19, and the lighting devices 11 to 13 are realized by a number of LEDs provided along the circumferential direction on the support member 19. Specifically, three equal regions are set on the support member 19, and by controlling the operation of the LEDs for each region, they function as the lighting devices 11 to 13.

[0017] The optical sensor 41 detects the illumination light irradiated from the illumination devices 11 to 13. The optical sensor 41 can be arranged at a location where it can detect the illumination light irradiated from the illumination devices 11 to 13 and the illumination light irradiated from the imaging unit 25 cannot directly reach. The optical sensor 41 is directed toward the illumination devices 11 to 13 and outputs a detection signal indicating the intensity of the light incident on the sensor surface of the optical sensor 41.

[0018] The imaging unit 25 is provided facing the side surface 92 of the product 90. The imaging unit 25 includes a camera 20 as an imaging device and three illumination devices 21, 22, and 23. Since the camera 20 and the illumination devices 21 to 23 are the same as the above-described camera 10 and illumination devices 11 to 13, detailed descriptions thereof are omitted.

[0019] The camera 20 images the product 90 from a certain direction to generate an image. In the example shown in FIG. 2, the camera 20 is directed in the horizontal direction, and imaging by the camera 20 is performed with the product 90 positioned directly beside the camera 20. In this case, the side surface 92 of the product 90 is imaged by the camera 20. In this example, the side surface 92 of the product 90 is shown as a plane, but it is not limited thereto.

[0020] The illumination devices 21 to 23 are configured to irradiate the side surface 92 of the product 90 with illumination light from three different illumination directions. The illumination devices 21 to 23 are arranged at the same distance from the product 90 so as to surround the camera 20. The illumination devices 21 to 23 are arranged at equal intervals on the circumference of a virtual circle centered on a point on the optical axis of the camera 20 and perpendicular to the optical axis of the camera 20. Each of the illumination devices 21 to 23 is directed obliquely sideways so that its optical axis intersects the optical axis of the camera 20.

[0021] The optical sensor 42 detects the illumination light irradiated from the lighting devices 21 to 23. The optical sensor 42 can be arranged at a location where it can detect the illumination light irradiated from the lighting devices 21 to 23 and the illumination light irradiated from the imaging units 15 does not directly reach. The optical sensor 42 is directed toward the lighting devices 21 to 23 and outputs a detection signal indicating the intensity of the light incident on the sensor surface of the optical sensor 42.

[0022] Referring to FIG. 1 again, the information processing unit 50 includes a control unit 51 that controls the imaging units 15 and 25, an image processing unit 52 that performs an appearance inspection on the product 90 based on the images obtained by the imaging units 15 and 25, and an output unit 53 that outputs the result of the appearance inspection. The information processing unit 50 can be implemented by a computer such as a personal computer (PC) or a server.

[0023] The control unit 51 controls the imaging units 15 and 25 so that the lighting devices 11 to 13 and 21 to 23 are lit one by one in a predetermined order to image the product 90 with the cameras 10 and 20. The control unit 51 obtains a first image set including three images of the upper surface 91 of the product 90 taken with the illumination light applied from each of the three illumination directions, and a second image set including three images of the side surface 92 of the product 90 taken with the illumination light applied from each of the three illumination directions.

[0024] The image processing unit 52 performs an appearance inspection on the product 90 based on the first image set obtained by the imaging unit 15 and the second image set obtained by the imaging unit 25, and determines whether the product 90 is a non-defective product or a defective product. For example, the image processing unit 52 performs an appearance inspection on the upper surface 91 of the product 90 based on the first image set obtained by the imaging unit 15, performs an appearance inspection on the side surface 92 of the product 90 based on the second image set obtained by the imaging unit 25, determines that the product 90 is a non-defective product when it is determined that there are no defects on both the upper surface 91 and the side surface 92 of the product 90, and determines that the product 90 is a defective product when it is determined that there is a defect on either the upper surface 91 or the side surface 92 of the product 90.

[0025] The above-mentioned appearance inspection can be performed using the illuminance difference stereo method or an image synthesis technique similar thereto. Since the illuminance difference stereo method is a well-known technique, a detailed description thereof will be omitted. For example, the image processing unit 52 synthesizes three images included in the first image set, obtains the normal line of the surface from the synthesized image, generates a normal line image representing the inclination of the normal line of the surface, and inputs the normal line image into the learned first inference model to detect whether there is a defect on the upper surface 91 of the product 90. Similarly, the image processing unit 52 synthesizes three images included in the second image set, obtains the normal line of the surface from the synthesized image, generates a normal line image representing the inclination of the normal line of the surface, and inputs the normal line image into the learned second inference model to detect whether there is a defect on the side surface 92 of the product 90. As the first inference model and the second inference model, for example, a deep neural network (DNN) such as R-CNN (Region Convolutional Neural Network) or SSD (Single Shot MultiBox Detector) can be used.

[0026] The output unit 53 outputs the result of the appearance inspection of the product 90. For example, the output unit 53 displays information indicating whether the product 90 is a good product or a defective product on a display device (not shown).

[0027] Figure 3 schematically shows the imaging sequence according to this embodiment. As shown in Figure 3, the control unit 51 performs, alternately, a first imaging process of imaging the upper surface 91 of the product 90 with the camera 10 while irradiating the upper surface 91 of the product 90 with illumination light from one of the illumination devices 11 to 13, and a second imaging process of imaging the side surface 92 of the product 90 with the camera 20 while irradiating the side surface 92 of the product 90 with illumination light from one of the illumination devices 21 to 23, thereby obtaining a first image set including three images of the upper surface 91 of the product 90 imaged with illumination light applied from each of the three illumination directions, and a second image set including three images of the side surface 92 of the product 90 imaged with illumination light applied from each of the three illumination directions. Specifically, the control unit 51 turns on the illumination device 11 and images the product 90 with the camera 10, turns off the illumination device 11, turns on the illumination device 21 and images the product 90 with the camera 20, turns off the illumination device 21, turns on the illumination device 12 and images the product 90 with the camera 10, turns off the illumination device 12, turns on the illumination device 22 and images the product 90 with the camera 20, turns off the illumination device 22, turns on the illumination device 13 and images the product 90 with the camera 10, and turns off the illumination device 13 and turns on the illumination device 23 and images the product 90 with the camera 20.

[0028] During the exposure of the camera, only one illumination device is turned on. Specifically, during the exposure of the camera 10 in the first imaging process, one of the illumination devices 11 to 13 (for example, the illumination device 11) is turned on, and the remaining ones of the illumination devices 11 to 13 (for example, the illumination devices 12, 13) and the illumination devices 21 to 23 are not turned on. During the exposure of the camera 20 in the second imaging process, one of the illumination devices 21 to 23 (for example, the illumination device 21) is turned on, and the remaining ones of the illumination devices 21 to 23 (for example, the illumination devices 22, 23) and the illumination devices 11 to 13 are not turned on.

[0029] The control unit 51 observes the lighting states of the lighting devices 11 to 13 based on the detection signals from the optical sensor 41. For example, when the light intensity indicated by the detection signal is below a predetermined value, the control unit 51 recognizes that the lighting devices 11 to 13 are turned off, and when the light intensity indicated by the detection signal is equal to or greater than the predetermined value, the control unit 51 recognizes that one of the lighting devices 11 to 13 is turned on. The control unit 51 recognizes that the lighting devices 11 to 13 of the imaging unit 15 are turned off by detecting that the light intensity indicated by the detection signal from the optical sensor 41 has switched from a state equal to or greater than the predetermined value to a state below the predetermined value.

[0030] The control unit 51 observes the lighting states of the lighting devices 21 to 23 based on the detection signals from the optical sensor 42. The control unit 51 recognizes that the lighting devices 21 to 23 of the imaging unit 25 are turned off by detecting that the light intensity indicated by the detection signal from the optical sensor 42 has switched from a state equal to or greater than the predetermined value to a state below the predetermined value.

[0031] In the imaging sequence shown in FIG. 3, the next imaging is performed using the turning-off of the lighting device as a trigger. For example, the control unit 51 turns on the lighting device 11, images the product 90 with the camera 10, and then turns off the lighting device 11. When the control unit 51 recognizes that the lighting device 11 is turned off based on the detection signal from the optical sensor 41, the control unit 51 turns on the lighting device 21, images the product 90 with the camera 20, and then turns off the lighting device 21. When the control unit 51 recognizes that the lighting device 21 is turned off based on the detection signal from the optical sensor 42, the control unit 51 turns on the lighting device 12, images the product 90 with the camera 10, and then turns off the lighting device 12.

[0032] On the other hand, in the imaging sequence according to the prior art shown in FIG. 4, after all the imaging of the upper surface 91 of the product 90 is completed, the imaging of the side surface 92 of the product 90 is performed. Specifically, first, the lighting device 11 is turned on and the product 90 is imaged by the camera 10, then the lighting device 11 is turned off and the lighting device 12 is turned on and the product 90 is imaged by the camera 10, then the lighting device 12 is turned off and the lighting device 13 is turned on and the product 90 is imaged by the camera 10, thereby obtaining three images of the upper surface 91 of the product 90. Subsequently, the lighting device 13 is turned off and the lighting device 21 is turned on and the product 90 is imaged by the camera 20, then the lighting device 21 is turned off and the lighting device 22 is turned on and the product 90 is imaged by the camera 20, then the lighting device 22 is turned off and the lighting device 23 is turned on and the product 90 is imaged by the camera 20, thereby obtaining three images of the side surface 92 of the product 90.

[0033] Referring to FIGS. 5 and 6, the advantages of the imaging sequence according to this embodiment will be described.

[0034] FIG. 5 schematically shows an inspection sequence according to the imaging sequence shown in FIG. 3 according to this embodiment, and FIG. 6 schematically shows an inspection sequence according to the imaging sequence shown in FIG. 4 according to the prior art. In FIGS. 5 and 6, the inspection sequence is shown in a format that displays time in the vertical direction.

[0035] As shown in FIG. 6, when taking a picture by triggering a single camera, after turning on the lighting device, an exposure is performed and the image data is stored in the memory, completing one shot. After one shot is completed, the trigger for the next shot is applied, and the shooting proceeds one after another. After three shots of the upper surface 91 of the product 90 using each of the lighting devices 11 to 13 are completed, three shots of the side surface 92 of the product 90 using each of the lighting devices 21 to 23 are taken. Image processing (including image synthesis and inference) using the first image set obtained from three shots of the upper surface 91 of the product 90 using the lighting devices 11 to 13 can be executed in parallel with the shooting by the lighting device 21. After three shots of the side surface 92 of the product 90 using the lighting devices 21 to 23 are completed, image processing using the second image set obtained from three shots of the side surface 92 of the product 90 using the lighting devices 21 to 23 is executed. If one shot takes 50 milliseconds, it takes 350 milliseconds to shoot two surfaces, and including the 30 milliseconds required for image processing, the total is 380 milliseconds.

[0036] In contrast, in the inspection sequence according to the present embodiment, as shown in FIG. 5, since shooting of two surfaces is performed alternately, before the shooting of one surface is completed, the trigger for shooting the other surface can be applied. For example, based on the detection signal from the optical sensor 41, the control unit 51 uses the detection that the lighting device 11 of the imaging unit 15 has turned off as a trigger to turn on the lighting device 21 of the imaging unit 25. The shooting by the camera 20 is performed in parallel with the storage of the image data obtained by the shooting by the camera 10 in the memory. As a result, the total shooting time is shortened. In the example shown in FIG. 5, it takes 170 milliseconds to shoot two surfaces, and including the 60 milliseconds required for image processing, the total is 230 milliseconds.

[0037] In the present embodiment, as described above, by alternately shooting two surfaces, the inspection time can be shortened.

[0038] The appearance inspection device 100 may further include a light shielding plate 71 shown in FIG. 7. The light shielding plate 71 is disposed between the optical sensors 41 and 42. Specifically, the light shielding plate 71 is disposed between the imaging unit 15 and the optical sensor 42 and between the imaging unit 25 and the optical sensor 41. The light shielding plate 71 prevents the illumination light from the illumination devices 11 to 13 from directly reaching the optical sensor 42, and prevents the illumination light from the illumination devices 21 to 23 from directly reaching the optical sensor 41. By providing the light shielding plate 71, false detection of the optical sensors 41 and 42 can be prevented.

[0039] FIG. 8 schematically shows a computer 80 that can implement the information processing unit 50. As shown in FIG. 8, the computer 80 includes, as hardware components, a processor 81, a RAM (Random Access Memory) 82, a program memory 83, a storage device 84, an input / output interface 85, and a bus 86. The processor 81 exchanges signals with the RAM 82, the program memory 83, the storage device 84, and the input / output interface 85 via the bus 86.

[0040] Processor 81 typically includes general-purpose circuits such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). RAM 82 is used by processor 81 as a working memory. RAM 82 includes volatile memory such as SDRAM (Synchronous Dynamic Random Access Memory). Program memory 83 stores programs executed by processor 81, such as an appearance inspection program. For example, ROM (Read-Only Memory) is used as program memory 83. Alternatively, a partial area of storage device 84 may be used as program memory 83. Processor 81 expands the program stored in program memory 83 into RAM 82 and interprets and executes the program. When the appearance inspection program is executed by processor 81, it causes processor 81 to execute the processes described with respect to control unit 51, image processing unit 52, and output unit 53. In other words, processor 81 functions as control unit 51, image processing unit 52, and output unit 53 according to the appearance inspection program.

[0041] Programs such as the appearance inspection program may be provided to computer 80 in a state stored in a computer-readable storage medium. In this case, for example, computer 80 is equipped with a drive for reading data from the storage medium and acquires the program from the storage medium. Examples of the storage medium include magnetic disks, optical disks (such as CD-ROM, CD-R, DVD-ROM, DVD-R), magneto-optical disks (such as MO), and semiconductor memories. Also, the program may be stored in a server on a network and computer 80 may download the program from the server.

[0042] Storage device 84 stores data. Storage device 84 includes non-volatile memory such as a hard disk drive (HDD) or a solid state drive (SSD).

[0043] The input / output interface 85 is an interface for communicating with an external device. The input / output interface 85 is connected to the imaging units 15, 25 and the optical sensors 41, 42 via a cable. The processor 81 controls the imaging units 15, 25 and the optical sensors 41, 42 via the input / output interface 85. The processor 81 acquires an image from the imaging units 15, 25 and a detection signal from the optical sensors 41, 42 via the input / output interface 85. Further, the input / output interface 85 may be connected to an output device such as an input device and a display device. Note that the input / output interface 85 may include a wireless module, and the computer 80 may communicate with the imaging units 15, 25 and the optical sensors 41, 42 wirelessly.

[0044] Note that the processor 81 may include a dedicated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array) instead of or in addition to the general-purpose circuit, and at least a part of a series of processes may be realized by the dedicated circuit.

[0045] As described above, in the appearance inspection apparatus 100, the control unit 51 performs the first imaging process of imaging the upper surface 91 of the product 90 with the camera 10 in a state where the illumination light from one of the illumination devices 11 to 13 of the imaging unit 15 is applied to the upper surface 91 of the product 90, and the second imaging process of imaging the side surface 92 of the product 90 with the camera 20 in a state where the illumination light from one of the illumination devices 21 to 23 of the imaging unit 25 is applied to the side surface 92 of the product 90 alternately, thereby obtaining a first image set including three images obtained by the camera 10 with illumination light applied from each of three different illumination directions and a second image set including three images obtained by the camera 20 with illumination light applied from each of three different illumination directions. The image processing unit 52 inspects the upper surface 91 of the product 90 based on the first image set by the illuminance difference stereo method and inspects the side surface 92 of the product 90 based on the second image set by the illuminance difference stereo method.

[0046] In the above configuration, the first imaging process and the second imaging process can be performed in parallel during processing other than exposure. For example, it is possible to perform the second imaging process while writing the image data obtained by the first imaging process into the memory. As a result, the total imaging time can be shortened, and as a result, the processing time required for the appearance inspection of each product can be shortened.

[0047] In the above-described embodiment, the case where each imaging unit 15, 25 includes three lighting devices has been described, but each imaging unit 15, 25 may include four or more lighting devices. The greater the number of lighting devices included in each imaging unit 15, 25, the higher the effect of shortening the inspection time.

[0048] In the above-described embodiment, the case where two surfaces are inspection targets has been described, but three or more surfaces may be inspection targets.

[0049] FIG. 9 schematically shows an appearance inspection apparatus 100 and an imaging sequence in the case where three surfaces are inspection targets. As shown in FIG. 9, the appearance inspection apparatus 100 includes an imaging unit 35 and an optical sensor 43 in addition to the configuration shown in FIG. 1.

[0050] The imaging unit 35 is provided to face the side surface 93 of the product 90. In the example shown in FIG. 9, the side surface 93 is adjacent to the upper surface 91 and the side surface 92. The imaging unit 35 includes a camera 30 and three lighting devices 31, 32, and 33. Since the camera 30 and the lighting devices 31 to 33 are the same as the camera 10 and the lighting devices 11 to 13 described above, detailed descriptions thereof are omitted.

[0051] The camera 30 images the product 90 from a certain direction to generate an image. The camera 30 is directed in the horizontal direction, and imaging by the camera 30 is performed in a state where the product 90 is positioned directly beside the camera 30. In this case, the side surface 93 of the product 90 is imaged by the camera 30. In this example, the side surface 93 of the product 90 is shown as a plane, but it is not limited thereto.

[0052] The lighting devices 31 to 33 are configured to irradiate the side surface 93 of the product 90 with illumination light from three different illumination directions. The lighting devices 31 to 33 are arranged at the same distance from the product 90 so as to surround the camera 30. The lighting devices 31 to 33 are arranged at equal intervals on the circumference of a virtual circle centered on a point on the optical axis of the camera 30 and perpendicular to the optical axis of the camera 30. Each of the lighting devices 31 to 33 is directed obliquely sideways so that its optical axis intersects the optical axis of the camera 30.

[0053] The light sensor 43 detects the illumination light irradiated from the lighting devices 31 to 33. The light sensor 43 is directed toward the lighting devices 31 to 33 and outputs a detection signal indicating the intensity of the light incident on the sensor surface of the light sensor 43. The control unit 51 detects the illumination state of the lighting devices 31 to 33 based on the detection signal from the light sensor 43.

[0054] The control unit 51 controls the imaging units 15, 25, 35 so that the lighting devices 11 to 13, 21 to 23, 31 to 33 are lit one by one in a predetermined order to image the product 90 with the cameras 10, 20, 30. For example, the control unit 51 lights the lighting devices one by one in the order of lighting device 11, lighting device 21, lighting device 31, lighting device 12, lighting device 22, lighting device 32, lighting device 13, lighting device 23, lighting device 33 to image the product 90 with the cameras 10, 20, 30.

[0055] The image processing unit 52 determines whether the product 90 is a non-defective product or a defective product based on the first image set obtained by the imaging unit 15, the second image set obtained by the imaging unit 25, and the third image set obtained by the imaging unit 35. The image processing unit 52 performs an appearance inspection of the side surface 93 of the product 90 based on the third image set obtained by the imaging unit 35. The image processing unit 52 determines that the product 90 is a non-defective product when there are no defects on any of the upper surface 91, side surface 92, and side surface 93 of the product 90, and determines that the product 90 is a defective product when there is a defect on any of the upper surface 91, side surface 92, and side surface 93 of the product 90.

[0056] In this way, by sequentially photographing the three surfaces to be inspected, the processing time can be shortened in the same manner as described above. The greater the number of surfaces to be inspected, the higher the effect of shortening the processing time.

[0057] When the direction of the defect is limited to a specific one direction, such as when the shape of the defect to be detected is elongated in one direction, the illumination difference stereo method with the direction limited may be used. In that case, the inspection is performed by arranging two lighting devices opposite to each camera.

[0058] FIG. 10 schematically shows a part of the appearance inspection apparatus 100 and a photographing sequence according to a further embodiment. In FIG. 10, the same reference numerals are given to the same components as those shown in FIG. 2, and detailed descriptions thereof are omitted. In the appearance inspection apparatus 100 shown in FIG. 10, the photographing unit 15 includes a camera 10 and two lighting devices 11 and 12, and the photographing unit 25 includes a camera 20 and two lighting devices 21 and 22. The lighting devices 11 and 12 face each other via the camera 10, and the lighting devices 21 and 22 face each other via the camera 20.

[0059] The appearance inspection apparatus 100 turns on the lighting device 11 and images the upper surface 91 of the product 90 with the camera 10, turns off the lighting device 11, turns on the lighting device 21, and images the side surface 92 of the product 90 with the camera 20, turns off the lighting device 21, turns on the lighting device 12, and images the upper surface 91 of the product 90 with the camera 10, turns off the lighting device 12, turns on the lighting device 22, and images the side surface 92 of the product 90 with the camera 20. Thereby, a first image set including two images of the upper surface 91 of the product 90 imaged with illumination light applied from each of the two illumination directions, and a second image set including two images of the side surface 92 of the product 90 imaged with illumination light applied from each of the two illumination directions are obtained. The appearance inspection apparatus 100 performs an appearance inspection on the upper surface 91 of the product 90 based on the first image set by the illumination difference stereo method with the direction limited, and performs an appearance inspection on the side surface 92 of the product 90 based on the second image set by the illumination difference stereo method with the direction limited.

[0060] In the inspection sequence according to a further embodiment, as shown in FIG. 11, photographing two surfaces alternately takes 110 milliseconds to photograph the two surfaces, and including the 60 milliseconds required for image processing, the total is 170 milliseconds.

[0061] On the other hand, when photographing the upper surface 91 of the product 90 twice as shown in FIG. 12 and then photographing the side surface 92 of the product 90 twice, as shown in FIG. 13, it takes 230 milliseconds to photograph the two surfaces, and including the 30 milliseconds required for image processing, the total is 260 milliseconds.

[0062] Thus, even when each lighting unit includes two lighting devices, by performing photographing in accordance with the photographing sequence according to the embodiment, the inspection time can be shortened.

[0063] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0064] 100... Appearance inspection device, 10, 20, 30... Cameras, 11 - 13, 21 - 23, 31 - 33... Lighting devices, 15, 25, 35... Photographing units, 19... Support member, 41, 42, 43... Optical sensors, 50... Information processing unit, 51... Control unit, 52... Image processing unit, 53... Output unit, 71... Light shielding plate, 80... Computer, 81... Processor, 82... RAM, 83... Program memory, 84... Storage device, 85... Input / output interface, 86... Bus.

Claims

1. A first imaging device that images a first surface of an object to be inspected; A plurality of first lighting devices that irradiate illumination light onto the first surface of the object to be inspected from a plurality of first lighting directions; A second imaging device that images a second surface of the object to be inspected; A plurality of second lighting devices that irradiate illumination light onto the second surface of the object to be inspected from a plurality of second lighting directions; A first imaging process of imaging the first surface of the object to be inspected with the first imaging device while illuminating light from one of the plurality of first lighting devices is applied to the first surface of the object to be inspected, and a second imaging process of imaging the second surface of the object to be inspected with the second imaging device while illuminating light from one of the plurality of second lighting devices is applied to the second surface of the object to be inspected. By alternately performing these processes, a first image set including a plurality of images obtained by the first imaging device with illumination light applied from each of the plurality of first lighting directions and a second image set including a plurality of images obtained by the second imaging device with illumination light applied from each of the plurality of second lighting directions are obtained. A control unit; An image processing unit that inspects the first surface of the object to be inspected based on the first image set and inspects the second surface of the object to be inspected based on the second image set; An appearance inspection device comprising the above.

2. During the exposure of the first imaging device in the first imaging process, one of the plurality of first lighting devices is turned on, and the remaining of the plurality of first lighting devices and the plurality of second lighting devices are not turned on. During the exposure of the second imaging device in the second imaging process, one of the plurality of second lighting devices is turned on, and the remaining of the plurality of second lighting devices and the plurality of first lighting devices are not turned on. The appearance inspection device according to Claim 1.

3. A first optical sensor that detects illumination light emitted from the plurality of first lighting devices; A second optical sensor that detects illumination light emitted from the plurality of second lighting devices; Further comprising: The control unit starts the second imaging process in response to detecting that one of the plurality of first lighting devices has turned off during the first imaging process based on the output from the first optical sensor, and starts the first imaging process in response to detecting that one of the plurality of second lighting devices has turned off during the second imaging process based on the output from the second optical sensor. The appearance inspection apparatus according to claim 1.

4. The appearance inspection apparatus according to claim 3, further comprising a light shielding plate that blocks the illumination light emitted from the plurality of first illumination devices from reaching the second photosensor and blocks the illumination light emitted from the plurality of second illumination devices from reaching the first photosensor.

5. The plurality of first illumination devices include three or more first illumination devices that irradiate illumination light onto the first surface of the inspection object from three or more first illumination directions. The plurality of second illumination devices include three or more second illumination devices that irradiate illumination light onto the second surface of the inspection object from three or more second illumination directions. The control unit alternately performs the first imaging process and the second imaging process, thereby obtaining a first image set including three or more images obtained by the first imaging device with illumination light applied from each of the three or more first illumination directions, and a second image set including three or more images obtained by the second imaging device with illumination light applied from each of the three or more second illumination directions. The control unit inspects the first surface of the inspection object based on the first image set by the illuminance difference stereo method, and inspects the second surface of the inspection object based on the second image set by the illuminance difference stereo method. The appearance inspection apparatus according to claim 1.

6. A first imaging process of imaging the first surface of the inspection object with a first imaging device while illuminating the first surface of the inspection object with illumination light from one of a plurality of first illumination devices that irradiate illumination light onto the first surface of the inspection object from a plurality of first illumination directions, and a second imaging process of imaging the second surface of the inspection object with a second imaging device while illuminating the second surface of the inspection object with illumination light from one of a plurality of second illumination devices that irradiate illumination light onto the second surface of the inspection object from a plurality of second illumination directions are alternately performed, thereby obtaining a first image set including a plurality of images obtained by the first imaging device with illumination light applied from each of the plurality of first illumination directions and a second image set including a plurality of images obtained by the second imaging device with illumination light applied from each of the plurality of second illumination directions. Inspecting the first surface of the inspection object based on the first image set. Inspecting the second surface of the object to be inspected based on the second image set; An appearance inspection method comprising the above.

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