JP2015068668A - Appearance inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve inspection with high accuracy by suppressing an influence of gloss of an object.SOLUTION: In an appearance inspection device 1, a composite inspection image is generated from a plurality of individual inspection images of an object 9 which are mutually different in irradiation directions of light from an illumination unit 5. When the composite inspection image is generated, a pixel value of the darkest pixel out of pixels of the plurality of individual inspection images, which correspond to each pixel on the composite inspection image, is determined as the pixel value of the pixel. The composite inspection image is compared with a reference image, and a difference between the composite inspection image and the reference image is detected as a shape defect of the object 9. In the composite inspection image, appearance of a second area shining due to gloss in a boundary part or the like of the object 9 can be suppressed or prevented. Therefore, a first area shining due to the shape defect can be easily extracted from an area different in brightness from its neighborhood. As a result, an influence of gloss of the object 9 can be suppressed to achieve appearance inspection with high accuracy.

Description

  The present invention relates to an appearance inspection apparatus for inspecting the appearance of an object having gloss on the surface.

  2. Description of the Related Art Conventionally, there has been used an apparatus that irradiates light on a three-dimensional object and picks up an image, and inspects the appearance of the object based on an image pickup result. For example, in the appearance inspection apparatus of Patent Document 1, when inspecting the appearance of the dome-shaped solder on the electronic circuit board, the first image is acquired in a state in which parallel light is irradiated from both the left and right sides of the dome-shaped solder, A second image is acquired in a state where parallel light is irradiated from both the front and rear sides of the dome-shaped solder. Then, when a composite image that is an absolute value of the difference between the first image data and the second image data is obtained, and when strip-like shadows exist radially on the composite image, mounting of chip components on the dome-shaped solder A defect is detected.

  In addition, the shape recognition device of Patent Document 2 includes a camera that images an object to be inspected and an illumination unit that rotates around the camera, and sequentially captures the object to be inspected while changing the illumination position of the illumination unit. Is called. In the shape recognition device, the shadow of the protrusion (defective shape) on the object to be inspected changes according to the change in the illumination position, so that the shape of the protrusion can be estimated.

JP 2005-17234 A JP 2009-162573 A

  By the way, as an apparatus for inspecting the appearance of an object, the inspection image of the object (that is, the object to be inspected) acquired by the imaging unit is compared with a reference image that is a good image prepared in advance. There is one that determines the quality of the appearance of an object. In such an apparatus, when an appearance inspection of an object having a glossy surface is performed, the edge portion of the object is brilliant due to the incident angle of illumination light on the object, and becomes brighter than the surrounding parts. . For this reason, even if the shape difference between the object and the non-defective product is a slight shape difference that does not need to be detected as a shape defect, May be judged as bad. In addition, even when the incident angle of the illumination light is slightly different between when the reference image is acquired and when the inspection image is acquired, the brightness at the edge portion differs greatly between the non-defective product and the target object. In some cases, the shape of this is determined to be defective.

  The present invention has been made in view of the above problems, and an object thereof is to suppress the influence of the gloss of an object and realize a highly accurate inspection.

  The invention according to claim 1 is an appearance inspection apparatus that inspects the appearance of an object having gloss on the surface, the illumination unit irradiating light while changing the irradiation direction of light on the object, and An imaging unit that images an object, and an imaging control unit that acquires a plurality of individual inspection images of the object with different light irradiation directions from the illumination unit by controlling the illumination unit and the imaging unit, and An inspection unit that generates a composite inspection image from the plurality of individual inspection images and inspects the appearance of the object based on the composite inspection image and a reference image prepared in advance, and the inspection unit includes the inspection unit, An image composition unit that obtains a representative pixel value based on a pixel value of a pixel of each of the plurality of individual inspection images corresponding to each pixel on the composite inspection image, and determines the representative pixel value as a pixel value of each pixel; The composite inspection image and the reference image Comparing the door, and a detector for detecting a difference between the reference image and the synthetic test image.

  The invention according to claim 2 is the appearance inspection apparatus according to claim 1, wherein the representative pixel value acquired in the image composition unit is the darkest pixel among the pixels of the plurality of individual inspection images. It is a pixel value.

  The invention according to claim 3 is the appearance inspection apparatus according to claim 1, wherein the representative pixel value acquired in the image composition unit is an average of pixel values of pixels of the plurality of individual inspection images. is there.

  According to a fourth aspect of the present invention, in the visual inspection apparatus according to any one of the first to third aspects, brightness of the plurality of individual inspection images is generated before the synthetic inspection image is generated by the inspection unit. The image forming apparatus further includes a correction unit that performs correction to reduce the difference.

  A fifth aspect of the present invention is the visual inspection apparatus according to any one of the first to fourth aspects, wherein the illumination unit includes a plurality of light emitting units having different relative positions with respect to the object, and the imaging The control unit controls the emission of light from the plurality of light emitting units.

  In the present invention, it is possible to suppress the influence of the gloss of the object and realize a highly accurate inspection.

It is a top view of the external appearance inspection apparatus which concerns on one embodiment. It is a side view of an appearance inspection apparatus. It is a block diagram which shows a control part. It is a figure which shows the flow of an external appearance test | inspection. It is a figure which shows an individual test | inspection image. It is a figure which shows a synthetic | combination test | inspection image. It is a figure showing a standard image. It is a figure which shows a difference image.

  FIG. 1 is a plan view showing an appearance inspection apparatus 1 according to an embodiment of the present invention. FIG. 2 is a side view showing the appearance inspection apparatus 1. The appearance inspection apparatus 1 is an apparatus that inspects the appearance of a three-dimensional object 9 having a glossy surface.

  The object 9 is, for example, a metal part formed by forging, and the surface thereof has a matte shape with minute irregularities. In other words, the surface of the object 9 is glossy while irregularly reflecting light. In the example shown in FIGS. 1 and 2, the object 9 is a connector shaft of a crank. The glossiness of the surface of the object 9 is preferably about 20 to about 60. The glossiness is an index that one-dimensionally represents the degree of gloss on the surface of an object by paying attention to the ratio of regular reflection light, the direction distribution of diffuse reflection light, and the like. The glossiness is measured using a gloss meter that conforms to an industrial standard glossiness measurement method such as JIS. On the surface of the object 9, the boundary portion between the upper and lower surfaces and the side surface has a shape from which corners are removed (so-called R shape).

  As shown in FIGS. 1 and 2, the appearance inspection apparatus 1 includes a support unit 2, an imaging unit 4, and an illumination unit 5. The support part 2 is a table having a flat upper surface. The object 9 is supported on the support unit 2 from below by being placed on the upper surface of the support unit 2. The imaging unit 4 is arranged obliquely above the object 9 on the support unit 2 and images the object 9. The imaging unit 4 is a digital camera having, for example, a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).

  The illumination unit 5 includes a plurality of light emitting units 51 disposed obliquely above the object 9. In the example shown in FIGS. 1 and 2, four light emitting portions 51 are provided. The relative positions of the plurality of light emitting portions 51 with respect to the object 9 are different from each other. Each light emitting unit 51 is, for example, an LED (Light Emitting Diode) light source. Each light emitting unit 51 may be another type of light source. The light emission from each light emission part 51 and the emission stop (that is, turning on and off) are individually controlled independently of the other light emission parts 51. In the illuminating unit 5, the light emission from the plurality of light emission units 51 and the emission stop are switched, whereby the object 9 is irradiated with light while changing the light irradiation direction with respect to the object 9.

  FIG. 3 is a block diagram illustrating functions of the control unit 6 of the appearance inspection apparatus 1. The control unit 6 has a general computer system configuration in which a CPU that performs various arithmetic processes, a ROM that stores basic programs, a RAM that stores various information, and the like are connected to a bus line. FIG. 3 also shows a part of another configuration connected to the control unit 6.

  The control unit 6 includes a storage unit 61, an imaging control unit 62, a correction unit 63, and an inspection unit 64. The storage unit 61 stores various information such as a reference image described later. The imaging control unit 62 acquires the image of the object 9 on the support unit 2 by controlling the imaging unit 4 and the illumination unit 5. The imaging control unit 62 includes an emission control unit 621 that individually controls the emission of light from the plurality of light emission units 51 (see FIGS. 1 and 2). The correction unit 63 corrects the image of the object 9. The inspection unit 64 inspects the appearance of the object 9 and detects the shape defect when the object 9 has a shape defect. The inspection unit 64 includes an image composition unit 641 and a detection unit 642.

  FIG. 4 is a diagram showing a flow of appearance inspection of the object 9 by the appearance inspection apparatus 1. When the appearance inspection is performed, first, the object 9 is placed on the support portion 2 as shown in FIG. Subsequently, when the illumination unit 5 is controlled by the emission control unit 621, one light emitting unit 51 among the plurality of light emitting units 51 is turned on, and light is emitted from the light emitting unit 51 to the object 9. Irradiated. Further, the other light emitting portions 51 are turned off. Next, when the imaging unit 4 is controlled by the imaging control unit 62, an image including the object 9 (hereinafter, referred to as “individual inspection image 81”) is acquired as shown in FIG. 5 (step S11). ).

  In the individual inspection image 81 shown in FIG. 5, there is a concave portion (hereinafter referred to as “defect concave portion 91”) that is a shape defect on the object 9, and light from the light emitting portion 51 is reflected by the defective concave portion 91. And shine brighter than the surrounding area. In the individual inspection image 81, an area having a brightness different from that of the surrounding area corresponding to the defect recess 91 is referred to as a “first area 82”. Further, in the individual inspection image 81, a region where the light from the light emitting unit 51 is reflected due to the gloss of the object 9 in a part of the above-described boundary portion or the like of the object 9 and shines brighter than the surrounding part. Occurs. In this manner, a region that is shining (so-called shining) due to gloss at the boundary portion of the object 9 or the like is referred to as a “second region 83”. In FIG. 5, in order to facilitate understanding of the drawing, the object 9 is shaded in parallel and the first region 82 and the second region 83 are painted black. The same applies to FIG.

  When one individual inspection image 81 is acquired, the light emitting unit 51 that is turned on is turned off and the other light emitting unit 51 is turned on under the control of the emission control unit 621. Thereby, the irradiation direction of the light irradiated from the illumination part 5 to the target object 9 is changed (step S12, S13). And it returns to step S11 and the separate test | inspection image 81 of the target object 9 is acquired by the imaging part 4. FIG. In the individual inspection image 81, since the irradiation direction of the light from the illumination unit 5 is different from that at the time of acquisition of the individual inspection image 81 shown in FIG. 5, the position and size of the second region 83 on the object 9 are as shown in FIG. The position and size shown in FIG. On the other hand, since the position and size of the defect recess 91 on the object 9 do not change, the position and size of the first region 82 are approximately the same as the position and size shown in FIG.

  In the appearance inspection apparatus 1, the light emitting unit 51 that is turned on is changed by the control by the imaging control unit 62 until a predetermined number (for example, four) of individual inspection images 81 are acquired (that is, for the object 9). The acquisition of the individual inspection image 81 is repeated (changing the light irradiation direction) (steps S11 to S13). Thereby, the several separate test | inspection image 81 of the target object 9 from which the irradiation direction of the light from the light emission part 51 differs is acquired. The plurality of individual inspection images 81 are sent to the correction unit 63.

  In the correction unit 63, correction for reducing the difference in brightness of the plurality of individual inspection images 81 is performed (step S14). Specifically, for each individual inspection image 81, a total pixel value that is the sum of the pixel values of all pixels is acquired as the overall brightness of the individual inspection image 81. The total pixel values of the plurality of individual inspection images 81 may be different from each other. The difference between the total pixel values of the plurality of individual inspection images 81 is, for example, the difference in the intensity of light emitted from the plurality of light emitting units 51 or the respective distances between the plurality of light emitting units 51 and the object 9. Due to the difference. Therefore, the correction coefficient corresponding to each individual inspection image 81 is set so that the total pixel values of the plurality of individual inspection images 81 are approximately equal to each other (that is, the overall brightness of each individual inspection image 81 is approximately equal to each other). Is determined. Then, by multiplying the pixel values of all the pixels of each individual inspection image 81 by the correction coefficient, each individual inspection image 81 is corrected, and the difference in brightness among the plurality of individual inspection images 81 is reduced. . The plurality of individual inspection images 81 corrected by the correction unit 63 are sent to the inspection unit 64.

  In the inspection unit 64, a composite inspection image is generated from the plurality of individual inspection images 81 corrected by the correction unit 63 (step S15). Specifically, a plurality of pixels located at the same pixel position in a plurality of corrected individual inspection images 81 are extracted by the image composition unit 641 of the inspection unit 64, and the pixel is based on the pixel values of the plurality of pixels. A representative pixel value corresponding to the position is acquired. In the present embodiment, four pixels located at the same position are extracted from the four individual inspection images 81, and the pixel value of the darkest pixel among the four pixels is acquired as the representative pixel value. The representative pixel value is a pixel value of a pixel located at the above-described pixel position in the composite inspection image.

  In the image composition unit 641, for all pixel positions on the individual inspection image 81, representative pixel values corresponding to the pixel positions (that is, the pixel value of the darkest pixel) are acquired by the same method as described above, and the representative pixels The value is determined as the pixel value of the pixel located at each pixel position of the composite inspection image. In other words, the representative pixel value is acquired by the image composition unit 641 for each pixel on the composite inspection image based on the pixel values of the pixels of the plurality of individual inspection images 81 corresponding to each pixel. Is determined as the pixel value of each pixel of the composite inspection image. Thereby, the synthetic | combination test | inspection image 84 shown in FIG. 6 is acquired.

  As shown in FIG. 6, in the composite inspection image 84, the pixel value of the darkest pixel of the plurality of individual inspection images 81 is set as the representative pixel value at each pixel position. The second region 83 that is positioned (that is, a region that is lost due to the gloss of the object 9) does not appear. Alternatively, the second area 83 is reduced in the composite inspection image 84. On the other hand, the first region 82 (that is, the region that shines brighter than the surrounding region due to the defect recess 91) located at approximately the same position in the plurality of individual inspection images 81 corresponds to the object 9 in the composite inspection image 84 as well. Appears at the position to be.

  In the inspection unit 64, the appearance of the object 9 is inspected based on the composite inspection image 84 and the reference image 80 prepared in advance shown in FIG. 7 (step S16). The reference image 80 is acquired by performing the above-described steps S11 to S15 for a non-defective product 90 that is an object having no shape defect. That is, the reference image 80 is a composite inspection image generated by a method similar to the generation of the above-described composite inspection image 84 from a plurality of individual inspection images of non-defective products 90 having different irradiation directions of light from the illumination unit 5. . In FIG. 7, in order to facilitate understanding of the drawing, the non-defective product 90 is given a parallel oblique line. As shown in FIG. 7, the reference image 80 does not include the first region 82 due to the shape defect and the second region 83 due to the gloss of the object.

  In the above-described appearance inspection by the inspection unit 64, the detection unit 642 obtains the difference between the composite inspection image 84 shown in FIG. 6 and the reference image 80 shown in FIG. 7, and is binarized by a predetermined threshold value. A difference image 85 shown in FIG. 8 is generated. Specifically, the difference data between the image data of the composite inspection image 84 and the image data of the reference image 80 is obtained and binarized to generate image data of the difference image 85. In the difference image 85, a portion that matches the non-defective product 90 of the object 9 does not appear, and a first region 82 corresponding to the defect recess 91 appears. In FIG. 8, in order to facilitate understanding of the drawing, the object 9 is indicated by a two-dot chain line, and the first region 82 is painted black. Then, the detection unit 642 detects the first region 82 on the difference image 85 as a shape defect in the object 9. In other words, the detection unit 642 compares the composite inspection image 84 with the reference image 80, and detects a difference between the composite inspection image 84 and the reference image 80 as a shape defect of the object 9.

  As described above, in the appearance inspection apparatus 1, a plurality of individual inspection images 81 of the object 9 having different irradiation directions of light from the illumination unit 5 are acquired, and a composite inspection image is obtained from the plurality of individual inspection images 81. 84 is generated. When generating the composite inspection image 84, for each pixel on the composite inspection image 84, a representative pixel value is acquired based on the pixel values of the pixels of the plurality of individual inspection images 81 corresponding to each pixel, and the representative pixel The value is determined as the pixel value of each pixel. Thereby, it is possible to suppress or prevent the second regions 83 appearing at different positions on the object 9 in the plurality of individual inspection images 81 from appearing on the composite inspection image 84.

  In the appearance inspection apparatus 1, a difference between the composite inspection image 84 and the reference image 80 is detected as a shape defect of the object 9. In the composite inspection image 84, as described above, since the appearance of the second region 83 is prevented or suppressed, the first region 82 and the second region 83, which are different in brightness from the surrounding regions, have a first defect caused by a shape defect. One area 82 can be easily extracted. As a result, it is possible to suppress the influence of the gloss of the object 9 and realize a highly accurate appearance inspection.

  As described above, in the appearance inspection apparatus 1, the representative pixel value acquired by the image composition unit 641 is the pixel value of the darkest pixel among the pixels of the plurality of individual inspection images 81. Thereby, it is possible to further suppress or prevent the second region 83 from appearing on the composite inspection image 84. As a result, the influence of the gloss of the object 9 can be further suppressed, and the accuracy of the appearance inspection of the object 9 can be improved.

  In the appearance inspection apparatus 1, the representative pixel value acquired when the composite inspection image 84 is generated is not necessarily the pixel value of the darkest pixel among the pixels of the plurality of individual inspection images 81. For example, when the plurality of individual inspection images 81 are acquired, if the illumination unit 5 is positioned on the approximately opposite side of the imaging unit 4 with the object 9 interposed therebetween, the representative acquired when the composite inspection image 84 is generated. The pixel value is preferably the average of the pixel values of the plurality of individual inspection images 81. In this way, when the light from the illumination unit 5 is backlit with respect to the surface to be inspected of the object 9 and the imaging unit 4, as described above, the average of the pixel values is used as the representative pixel value. Further, the influence of the gloss of the object 9 can be further suppressed, and the accuracy of the appearance inspection of the object 9 can be improved.

  In the appearance inspection apparatus 1, the correction unit 63 performs correction to reduce the difference in brightness of the plurality of individual inspection images 81 before the generation of the composite inspection image 84 by the inspection unit 64. Thereby, in the plurality of individual inspection images 81, there is an influence due to a difference in intensity of light emitted from the plurality of light emitting units 51, a difference in distance between the plurality of light emitting units 51 and the object 9, or the like. Can be removed or suppressed. As a result, when the composite inspection image 84 is generated, the representative pixel value corresponding to each pixel can be obtained with high accuracy, and the accuracy of the appearance inspection of the object 9 can be further improved.

  As described above, the illumination unit 5 includes a plurality of light emitting units 51 having different relative positions to the object 9. Then, the emission control unit 621 controls the emission of light from the plurality of light emission units 51, whereby the light irradiation direction from the light emission unit 51 can be easily changed. Moreover, the illumination part 5 which can change easily the irradiation direction of the light with respect to the target object 9 can be manufactured at low cost.

  Various changes can be made to the appearance inspection apparatus 1 described above.

  For example, in the appearance inspection apparatus 1, when acquiring the individual inspection image 81, two or more light emitting units 51 among the plurality of light emitting units 51 may be turned on. In the illuminating unit 5, by changing the number of light emitting units 51 that are turned on, not only the direction of light irradiation from the illuminating unit 5 to the object 9 but also the brightness of the light irradiated onto the object 9 is easy. Can be changed.

  The illumination unit 5 does not necessarily include the plurality of light emitting units 51, and may include one light emitting unit 51 and a moving mechanism that moves the light emitting unit 51 around the object 9. . By changing the position of the light emitting unit 51 by the moving mechanism, the irradiation direction of the light from the illumination unit 5 to the object 9 is changed. Or the illumination part 5 may be provided with the rotation mechanism which rotates the light emission part 51 and the support part 2 which supports the target object 9 horizontally. By the rotation mechanism, the support unit 2 and the imaging unit 4 fixed to the support unit 2 rotate about a rotation axis that passes through the center of the support unit 2 and faces in the vertical direction. Thereby, the irradiation direction of the light from the illumination part 5 to the target object 9 is changed.

  In the appearance inspection apparatus 1, when the difference in brightness among the plurality of individual inspection images 81 is small, the correction by the correction unit 63 may be omitted. Further, the representative pixel value acquired when the composite inspection image 84 is generated is not necessarily the pixel value of the darkest pixel or the average of the pixel values. Based on this, it may be determined in various ways.

  When the position of the object 9 in the individual inspection image 81 is deviated from the position of the non-defective product 90 in the reference image 80, the individual inspection image 81 is matched with the position of the non-defective product 90 by pattern matching or the like. It is preferable that the process is performed. This process is preferably performed before the generation of the composite inspection image 84 (step S15).

  In the appearance inspection apparatus 1 shown in FIG. 1, the appearance inspection is performed on the object 9 stopped on the support unit 2, but the appearance inspection may be performed on the moving object 9. . For example, for an object 9 conveyed on a predetermined movement path by a belt conveyor or the like, an imaging unit while changing a light irradiation direction to the object 9 from the illumination unit 5 arranged along the movement path A plurality of individual inspection images 81 may be acquired by 4. In this case, the object 9 and the non-defective product 90 are aligned by the above-described pattern matching or the like.

  In the above example, the detection of the defect recess 91 has been described, but the shape defect detected by the appearance inspection apparatus 1 may be a protrusion or other various shapes. Also in this case, since the appearance of the second region 83 is suppressed or prevented in the composite inspection image 84, the first region 82 caused by the shape defect can be easily extracted. As a result, it is possible to suppress the influence of the gloss of the object 9 and realize a highly accurate appearance inspection.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 4 Imaging part 5 Illumination part 9 Object 51 Light emission part 62 Imaging control part 63 Correction | amendment part 64 Inspection part 80 Reference | standard image 81 Individual test | inspection image 84 Composite inspection image 641 Image composition part 642 Detection part S11-S16 Step

Claims (5)

An appearance inspection apparatus for inspecting the appearance of an object having gloss on the surface,
An illumination unit that emits light while changing the direction of light irradiation on the object;
An imaging unit for imaging the object;
By controlling the illumination unit and the imaging unit, an imaging control unit that acquires a plurality of individual inspection images of the object with different irradiation directions of light from the illumination unit;
An inspection unit that generates a composite inspection image from the plurality of individual inspection images, and inspects the appearance of the object based on the composite inspection image and a reference image prepared in advance;
With
The inspection unit is
An image composition unit that obtains representative pixel values based on pixel values of pixels of the plurality of individual inspection images corresponding to the pixels on the composite inspection image, and determines the representative pixel values as pixel values of the pixels; ,
A detector that compares the composite inspection image with the reference image and detects a difference between the composite inspection image and the reference image;
An appearance inspection apparatus comprising: The appearance inspection apparatus according to claim 1,
The appearance inspection apparatus, wherein the representative pixel value acquired in the image composition unit is a pixel value of a darkest pixel among the pixels of the plurality of individual inspection images. The appearance inspection apparatus according to claim 1,
The appearance inspection apparatus, wherein the representative pixel value acquired in the image composition unit is an average of pixel values of pixels of the plurality of individual inspection images. The appearance inspection apparatus according to any one of claims 1 to 3,
An appearance inspection apparatus further comprising a correction unit that performs correction to reduce a difference in brightness of the plurality of individual inspection images before the generation of the combined inspection image by the inspection unit. The appearance inspection apparatus according to any one of claims 1 to 4,
The illumination unit includes a plurality of light emitting units having different relative positions with respect to the object,
The appearance inspection apparatus, wherein the imaging control unit controls light emission from the plurality of light emitting units.

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