JP3930528B2 - Inspection method of article surface - Google Patents

Description

  The present invention relates to a method for inspecting the appearance of an article using an image obtained by photographing the article surface.

  Various methods are generally known as methods for inspecting the state of an article surface. In particular, a method for inspecting the state of an article surface by photographing the article with a CCD camera and processing the image is adopted. Yes. In this case, for example, about 10 points are selected from the pixels indicating the surface to be inspected in the image photographed by the CCD camera, and the average value of the luminances is determined as the standard value. Compared to the above, the state of the article surface is inspected.

  However, according to such a conventional inspection method, the inspection result is not stable due to a change in the surface condition of the article, a change in the external environment such as sunlight or indoor lighting, and the presence or absence of illumination for taking an image. There was a problem. On the other hand, in order to eliminate the influence of the external environment and the like in order to stabilize the test results, a great investment was required.

  An object of the present invention is to provide a method and system capable of inspecting the state of an article surface stably without being affected by the external environment.

  The present inventors photographed a plated surface of a disk-shaped magnet made of a rare earth metal with a CCD camera, observed color irregularities, spots, blisters, chips, etc. in the image, and as a result of various examinations, the surface to be inspected ( The optical measurement value (particularly the plating surface), especially the brightness, varies depending on the external environment and the type of product, but the brightness of the pixel indicating the surface to be inspected in the image taken by the CCD camera is flat or curved. If the curved surface is small, it shows an almost constant value and becomes a normal distribution of about ± 20%. On the other hand, if the surface to be inspected has defects such as spots, blisters, and hair cracks, the defective portion in the image It has been found that the luminance of the pixel indicating the is a unique value.

Based on such knowledge, according to the present invention, a method of inspecting the surface of an article with a CCD camera and inspecting the surface of the article with the image, the pixel from the pixel indicating the surface to be inspected is displayed. When two symmetric or line symmetric pixels are selected, the luminance ratio of the two selected pixels is calculated, and the luminance ratio is outside a predetermined range across a plurality of adjacent pixels. An inspection method is provided , wherein the inspection method is characterized in that the state is determined to be defective .

In this inspection method, it is preferable to compare all the pixels indicating the surface to be inspected. Further, when selecting two pixels, for example, a pixel that is point-symmetric or line-symmetric can be selected. For example, the luminances of the two selected pixels are compared. In that case, the ratio of the luminance of the two selected pixels is obtained, and when a predetermined number of pixels having the ratio outside the predetermined range continues, the state of the article surface can be determined to be defective. When the surface to be inspected of the article is photographed with a CCD camera, the surface to be inspected may be illuminated with a light source. Inspection means comprising a light source that illuminates the image from almost right above the article and a CCD camera located directly above the article, a light source that illuminates the outer peripheral green part of the article, and a CCD camera located directly above the article; And an inspection unit including a light source and a CCD camera arranged around an optical axis inclined obliquely with respect to a direction perpendicular to the surface of the article.

  According to the present invention, it is possible to stably inspect the appearance of an article.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of an inspection system 1 according to an embodiment of the present invention. In this embodiment, it is configured as an inspection system 1 that continuously inspects the appearance of a workpiece W made of an Nd—Fe—B—C based sintered magnet, which is an example of an article.

  The workpiece (rare earth magnet) W has a flat plate shape such as a circle or a square. The workpiece W having such a flat plate shape is formed by cutting a round bar-shaped or square bar-shaped sintered product obtained by firing into slices. For example, the workpiece W has a thickness of about several millimeters and a diameter or a length of one side. Is about 10 mm. For this reason, both the front surface W1 and the back surface W2 of the workpiece | work W are formed in the cut surface.

  In the inspection system 1 shown in FIG. 1, the workpiece W is supplied from the hopper 10 through the alignment feeder 11 and the linear feeder 12 and taken out one by one by the cutting device 13, and the first end of the first conveyor 14 (in FIG. 1). , Workpieces W are supplied one by one to the left end of the first conveyor 14). The alignment feeder 11 is adapted to apply vibration to the workpiece W supplied from the hopper 10 so as to align the surface W1 of the workpiece W with the posture facing upward, and deliver it to the next linear feeder 12. The cutting device 13 rotates counterclockwise in FIG. 1, and the thickness of the workpiece W is inspected by the two thickness inspection devices 15 and 16 during the conveyance.

  The first conveyor 14 conveys the work W from the start end to the end (in the right direction in FIG. 1) with the surface W1 of the work W transferred from the cutting device 13 facing upward. To go. The end of the first conveyor 14 (in FIG. 1, the right end of the first conveyor 14) is connected to the start of the second conveyor 20 (in FIG. 1, the left end of the second conveyor 20). The first conveyor 14 and the second conveyor 20 constitute a conveying device that conveys the workpiece W.

  A reversing device 21 for reversing the workpiece W upside down is disposed at a connection location between the terminal end of the first conveyor 14 and the starting end of the second conveyor 20. The reversing device 21 reverses the workpiece W transferred from the first conveyor 14 so that the back surface W2 of the workpiece W faces upward. The second conveyor 20 conveys the workpiece W, which is thus placed in the posture in which the back surface W2 is directed upward by the reversing device 21, from the start end portion toward the end portion (rightward in FIG. 1).

  Along the first conveyor 14, three inspection means 26, 27, and 28 for inspecting the appearance of the sorting device 25 and the surface W1 of the workpiece W are disposed. The sorting apparatus 25 causes the work W, which has been determined to be in a predetermined range by being inspected by the thickness inspection apparatuses 15 and 16, to be conveyed rightward in FIG. The workpiece W determined to have a thickness exceeding the predetermined range is discharged to the region 30, and the workpiece W whose thickness is determined to be less than the predetermined range is discharged to the region 31. As a result, only the workpiece W having a predetermined thickness is supplied to the next inspection means 26, 27, 28.

  On the other hand, along the second conveyor 20, three inspection means 35, 36, 37 for inspecting the appearance of the work W on the back surface W 2 side and a sorting device 38 are arranged. The sorting device 38 is inspected by the inspection means 26, 27, 28 arranged along the first conveyor 14 and the inspection means 35, 36, 37 arranged along the second conveyor 20. The work W determined to be normal is transported to the storage area 41 through the chute 40 at the end portion of the second conveyor 20, but the work W determined to have a poor appearance is the second conveyor 20. The work W whose outer appearance cannot be determined through the chute 42 at the end portion of the second conveyor 20 is carried out to the region 46 via the chute 45 at the end portion of the second conveyor 20.

  Here, the inspection means 26 arranged along the first conveyor 14 and the inspection means 35 arranged along the second conveyor 20 have the same configuration, and FIG. , 35. A light source 50 is arranged above the workpiece W conveyed by the first conveyor 14 or the second conveyor 20, and the workpiece W is illuminated almost directly from the light source 50. The light source 50 has a ring shape, and the reflected light emitted from the light source 50 to the workpiece W enters the conversion lens 51 disposed at the center of the light source 50, passes through the zoom lens 52, and is moved by the CCD camera 53. Images will be taken. In the inspection means 26 and 35, the conversion lens 51, zoom lens 52 and CCD camera 53 are all directly above the workpiece W (in the inspection means 26, perpendicular to the surface W1 of the workpiece W, In this case, it is positioned perpendicular to the back surface W2. In this way, the inspection means 26 images the surface to be inspected (surface W1) from the direction perpendicular (directly above) the surface W1 of the workpiece W conveyed by the first conveyor 14, and the inspection means 35 The surface to be inspected (back surface W2) is photographed from the direction perpendicular (directly above) to the back surface W2 of the workpiece W conveyed by the second conveyor 20.

  Further, the inspection means 27 arranged along the first conveyor 14 and the inspection means 36 arranged along the second conveyor 20 are basically the same as the inspection means 26 and 35 described in FIG. As shown in FIG. 3, the work W is illuminated by a ring-shaped light source 55, the reflected light enters the conversion lens 56, passes through a zoom lens 57, and is then moved to the work W by the CCD camera 58. Images are taken. These conversion lens 56, zoom lens 57 and CCD camera 58 are all directly above the workpiece W (perpendicular to the front surface W1 of the workpiece W in the inspection means 27, and back surface W2 in the inspection means 36). The inspection means 27 takes an image from a direction perpendicular to the surface W1 of the workpiece W conveyed by the first conveyor 14, and the inspection means 36 uses the second conveyor 20 to An image is taken from a direction perpendicular to the back surface W2 of the work W being conveyed. However, in these inspection means 27 and 36, the light source 55 has a large diameter (compared to the light source 50) and irradiates light from the periphery of the work W to the outer peripheral green portion of the work W. In the form shown in the figure, light is irradiated downward at an angle of 45 ° with respect to the outer peripheral green portion of the workpiece W. As a result, the light emitted from the light source 55 is reflected by the outer periphery green portion of the workpiece W, so that the CCD camera 58 captures the outer periphery green portion of the workpiece W.

  In addition, the inspection means 28 arranged along the first conveyor 14 and the inspection means 37 arranged along the second conveyor 20 are basically the same as the inspection means 26 and 35 described in FIG. As shown in FIG. 4, the workpiece W is illuminated by a ring-shaped light source 60, the reflected light enters the conversion lens 61, passes through the zoom lens 62, and is then moved by the CCD camera 63. Images are taken. However, the inspection means 26 and 35 and the inspection means 27 and 36 described above irradiate the workpiece W with light from directly above, and the conversion lenses 51 and 56, the zoom lenses 52 and 57, and the CCD cameras 53 and 58 are provided. All of the inspection means 28 and 37 are arranged directly above the workpiece W (perpendicular to the front surface W1 or the rear surface W2 of the workpiece W). As shown in FIG. The conversion lens 61, the zoom lens 62, and the CCD camera 63 are all arranged around the optical axis Y inclined obliquely by α ° with respect to the direction X perpendicular to the front surface W1 or the rear surface W2 of the workpiece W. Is different. In this case, the inclination angle α is, for example, about 5 ° to 10 °.

  As the light source 50 of these inspection means 26 and 35 and the light source 60 of the inspection means 28 and 37, for example, ring illumination of a halogen lamp is used, and as the light source 55 of the inspection means 27 and 36, for example, inner diameter irradiation of a halogen lamp. Illumination is used.

  In these inspection means 26 and 35, inspection means 27 and 36, and inspection means 28 and 37, conversion lenses 51, 56, and 61 are, for example, CV-05 (0.5 times), CV-025 manufactured by Seiwa Optical Co., Ltd. (0.25 times) lens is used. In this case, a CV-025 (0.25 times) lens is used for a point-symmetric workpiece W having a maximum diameter of 32Φ or less, and a CV- is used for a point-symmetric workpiece W having a maximum diameter of 16Φ or less. It is preferable to change the lens to be used according to the size of the workpiece W, the inspection standard, or the like, such as using a 05 (0.5 times) lens.

  Further, in these inspection means 26, 35, inspection means 27, 36 and inspection means 28, 37, zoom lenses 52, 57, 62 are, for example, MS-501 (0.75-4.5) manufactured by Seiwa Optical Co., Ltd. A high resolution zoom lens is used. As the CCD cameras 53, 58, 63, for example, CS3910 (resolution 1280 × 1030) manufactured by Tokyo Denshi, FC-1300 (resolution 1280 × 1030) manufactured by Takenaka System, XC-7500 (resolution 512 × 480) manufactured by SONY, etc. Is used. It should be noted that the first FHC-331LV may be used as an image input board for the CS3910 manufactured by Tokyo Denshi and the FC-1300 manufactured by Takenaka System, and the first RICE-001 used as the image input board for the XC-7500 manufactured by SONY. It is good to use.

  As shown in FIG. 1, images taken by these inspection means 26, 35, inspection means 27, 36 and inspection means 28, 37 are input to the control device 70. The control device 70 inspects the surface of the workpiece W as will be described later based on the image thus input, and controls the sorting device 38 disposed at the end portion of the second conveyor 20 based on the inspection result. As a result, as described above, only the work W having a normal appearance is carried out to the storage area 41, the work W having a bad appearance is carried out to the area 43, and the work W whose appearance cannot be determined is carried out to the area 46. It is like that.

  Now, in the inspection system 1 configured as described above, the workpieces W with the surface W1 facing upward are supplied one by one to the starting end of the first conveyor 14 by the cutting device 13. And only the workpiece | work W whose thickness is in the predetermined range is conveyed by the 1st conveyor 14 rightward in FIG.

  During this conveyance, the appearance on the surface W1 side of the workpiece W is inspected by the inspection means 26, 27, and 28. That is, the light is first illuminated by the light source 50 of the inspection means 26, the image of the surface W 1 of the work W is taken by the CCD camera 53, and the image is input to the control device 70. Thus, the image A of the surface W1 of the workpiece W photographed by the CCD camera 53 and input to the control device 70 has a circular shape as shown in FIG. 5, for example, when the shape of the surface W1 of the workpiece W is circular. The surface (surface W1 of the workpiece W) is projected, and, for example, when the shape of the surface W1 of the workpiece W is a quadrangle, a rectangular test surface (the surface W1 of the workpiece W) is projected as shown in FIG. It will be.

  The control device 70 selects any two pixels a and b from the pixels indicating the surface to be inspected (the surface W1 of the workpiece W) in the image A, and compares them to compare the surface of the workpiece W. Inspect W1. In this case, if the surface to be inspected (surface W1 of the workpiece W) is a point-symmetric shape such as a circular shape, two pixels a and b that are point-symmetric about the center point O are selected as shown in FIG. Compare them one by one. Specifically, the example shown in FIG. 5 will be described in detail. The pixel a1 and the pixel b1 are compared, the pixel a2 and the pixel b2 are compared, the pixel a3 and the pixel b3 are compared, and the pixel a4 and the pixel b4 are compared. , Compare pixel a5 and pixel b5, compare pixel a6 and pixel b6, compare pixel a7 and pixel b7, compare pixel a8 and pixel b8, compare pixel a9 and pixel b9, and compare pixel a10 and pixel b9 compare b10, compare pixel a11 and pixel b11, compare pixel a12 and pixel b12, compare pixel a13 and pixel b13, compare pixel a14 and pixel b14, compare pixel a15 and pixel b15, Pixel a16 and pixel b16 are compared. In this way, all the pixels a1 to a16 and b1 to b16 indicating the surface to be inspected (the surface W1 of the workpiece W) are compared.

  If the surface to be inspected (surface W1 of the workpiece W) is a line-symmetric shape such as a quadrangle, two pixels that are line-symmetric about the center line L are selected as shown in FIG. Compare one by one. Specifically, the example shown in FIG. 6 will be described in detail. The pixel a1 is compared with the pixel b1, the pixel a2 is compared with the pixel b2, the pixel a3 is compared with the pixel b3, and the pixel a4 is compared with the pixel b4. , Compare pixel a5 and pixel b5, compare pixel a6 and pixel b6, compare pixel a7 and pixel b7, compare pixel a8 and pixel b8, compare pixel a9 and pixel b9, and compare pixel a10 and pixel b9 compare b10, compare pixel a11 and pixel b11, compare pixel a12 and pixel b12, compare pixel a13 and pixel b13, compare pixel a14 and pixel b14, compare pixel a15 and pixel b15, The pixel a16 and the pixel b16 are compared, the pixel a17 and the pixel b17 are compared, and the pixel a18 and the pixel b18 are compared. In this way, all the pixels a1 to a18 and b1 to b18 indicating the surface to be inspected (the surface W1 of the workpiece W) are compared.

  And when comparing each pixel a and b in this way, the brightness | luminance B of each two selected pixels a and b is compared, respectively, of the surface W1 of the workpiece | work W shown by each pixel a and b. Each part can be inspected throughout. That is, when there is no defect on the surface W1 of the workpiece W, the luminance of each pixel a, b indicating the surface to be inspected (the surface W1 of the workpiece W) in the image A taken by the CCD camera 53 is If the surface W1 is a flat surface or a curved surface having a small curvature, the surface W1 shows a substantially constant value and a normal distribution of about ± 20%. On the other hand, when there are defects such as uneven color, spots, blisters, hair cracks, and chippings on the surface W1 of the work W, the pixels a and b indicating the positions where the defects are present have unique values for the luminance B. It will be. Accordingly, the ratio of the luminance B of each pixel a, b indicating the surface to be inspected (the surface W1 of the workpiece W) is obtained, and if all the ratios are within a predetermined range (from a normal distribution of about ± 20%). If the surface W1 of the workpiece W is not defective, on the other hand, if there is a portion where the ratio is outside the predetermined range, pixels that deviate from the normal distribution of about ± 20% are detected. In some cases, it is possible to determine that the surface W1 of the workpiece W is defective.

  Here, usually, defects such as uneven color, spots, blisters, hair cracks, and chips are often formed in a considerable range on the surface W1 of the workpiece W. For this reason, uneven colors, stains, blisters, hairs, etc. When a defect such as a crack or a chip exists, the luminance of each pixel a and b indicating the surface to be inspected (the surface W1 of the workpiece W) in the image A is continuously unique across the plurality of pixels a and b. Often shows a value. Therefore, the state of the surface W1 of the workpiece W may be determined to be defective when the ratio of the luminance B is out of a predetermined range across a plurality of adjacent pixels a and b.

  In this way, the inspection by the image photographed by the CCD camera 53 of the inspection means 26 is performed, and subsequently, the image is illuminated by the light source 55 of the inspection means 27 and the outer peripheral green portion of the surface W1 of the workpiece W is illuminated by the CCD camera 58. Is photographed and the image is input to the control device 70. In this way, the image A ′ of the outer peripheral green portion of the surface W1 of the workpiece W taken by the CCD camera 58 and input to the control device 70 is, for example, as shown in FIG. 7 when the shape of the surface W1 of the workpiece W is circular. A thin and continuous surface to be inspected (a green portion on the outer periphery of the surface W1 of the workpiece W) is projected. For example, when the shape of the surface W1 of the workpiece W is a quadrangle, as shown in FIG. A thin and continuous surface to be inspected (the outer peripheral green portion of the surface W1 of the workpiece W) is projected.

  Then, the control device 70 selects any two pixels a and b from the pixels indicating the surface to be inspected (the outer peripheral green portion of the surface W1 of the workpiece W) in the image A ′ as before. The surface W1 of the workpiece W is inspected by comparing them. In this case, if the surface W1 of the workpiece W is a point-symmetric shape such as a circular shape, two pixels a and b that are point-symmetric about the center point O are selected as shown in FIG. Compare. Specifically, the example shown in FIG. 7 will be described in detail. The pixel a1 and the pixel b1 are compared, the pixel a2 and the pixel b2 are compared, the pixel a3 and the pixel b3 are compared, and the pixel a4 and the pixel b4 are compared. , Compare pixel a5 and pixel b5, compare pixel a6 and pixel b6, compare pixel a7 and pixel b7, compare pixel a8 and pixel b8, compare pixel a9 and pixel b9, and compare pixel a10 and pixel b9 Compare b10. In this way, all the pixels a1 to a10 and b1 to b10 indicating the surface to be inspected (the outer peripheral edge portion of the surface W1 of the workpiece W) are compared.

  If the surface W1 of the workpiece W is a line-symmetric shape such as a quadrangle, two pixels that are line-symmetric about the center line L are selected and compared with each other as shown in FIG. Specifically, the example shown in FIG. 8 will be described in detail. The pixel a1 and the pixel b1 are compared, the pixel a2 and the pixel b2 are compared, the pixel a3 and the pixel b3 are compared, and the pixel a4 and the pixel b4 are compared. , Compare pixel a5 and pixel b5, compare pixel a6 and pixel b6, compare pixel a7 and pixel b7, compare pixel a8 and pixel b8, compare pixel a9 and pixel b9, and compare pixel a10 and pixel b9 Compare b10. In this way, all the pixels a1 to a10 and b1 to b10 indicating the surface to be inspected (the outer peripheral edge portion of the surface W1 of the workpiece W) are compared.

  And also when comparing each pixel a and b which shows the outer periphery part of the surface W1 of the workpiece | work W in this way, by comparing the brightness | luminance B of two pixels a and b respectively selected, Each location of the outer peripheral edge of the surface W1 of the workpiece W indicated by the pixels a and b can be inspected. Also in this case, the ratio of the luminance B of each pixel a, b indicating the surface to be inspected (the outer peripheral edge portion of the surface W1 of the workpiece W) is obtained, and the ratio is determined to be defective at the outer peripheral edge portion of the surface W1 of the workpiece W. It becomes possible to determine whether or not there is. Further, when the ratio of the luminance B is outside a predetermined range over a plurality of adjacent pixels a and b, the state of the outer peripheral edge portion of the surface W1 of the workpiece W may be determined to be defective.

  Further, after the inspection by the image taken by the CCD camera 58 of the inspection means 27 is performed in this way, the image is further illuminated by the light source 60 of the inspection means 28 and the image of the surface W1 of the workpiece W is taken by the CCD camera 63. , The image is input to the control device 70. Thus, the image A of the surface W1 of the workpiece W taken by the CCD camera 63 and input to the control device 70 is, for example, circular as described above with reference to FIG. 5 if the shape of the surface W1 of the workpiece W is circular. The surface to be inspected (surface W1 of the workpiece W) is projected, and if the shape of the surface W1 of the workpiece W is square, for example, as described above with reference to FIG. The surface W1) is projected.

  Then, in the control device 70, as in the previous case, also in this image A, any two pixels a and b are selected from the pixels indicating the surface to be inspected (the surface W1 of the workpiece W) and compared. Thus, the outer peripheral green portion of the surface W1 of the workpiece W is inspected. In this case, if the surface W1 of the workpiece W is a point-symmetric shape such as a circular shape, the pixel a1 and the pixel b1, the pixel a2, and the pixel b2 that are point-symmetrical with respect to the center point O as described above with reference to FIG. , Pixel a3 and pixel b3, pixel a4 and pixel b4, pixel a5 and pixel b5, pixel a6 and pixel b6, pixel a7 and pixel b7, pixel a8 and pixel b8, pixel a9 and pixel b9, pixel a10 and pixel b10, pixel By comparing a11 and pixel b11, pixel a12 and pixel b12, pixel a13 and pixel b13, pixel a14 and pixel b14, pixel a15 and pixel b15, pixel a16 and pixel b16, respectively, the surface to be inspected (surface W1 of work W ) Are compared for all the pixels a1 to a16 and b1 to b16.

  If the surface W1 of the workpiece W is a line-symmetric shape such as a square shape, the pixel a1 and the pixel b1, the pixel a2 and the pixel b2, which are line-symmetric with respect to the center line L, as described above with reference to FIG. Pixel a3 and pixel b3, pixel a4 and pixel b4, pixel a5 and pixel b5, pixel a6 and pixel b6, pixel a7 and pixel b7, pixel a8 and pixel b8, pixel a9 and pixel b9, pixel a10 and pixel b10, pixel a11 Pixel b11, pixel a12 and pixel b12, pixel a13 and pixel b13, pixel a14 and pixel b14, pixel a15 and pixel b15, pixel a16 and pixel b16, pixel a17 and pixel b17, pixel a18 and pixel b18, respectively Thus, all the pixels a1 to a18 and b1 to b18 indicating the surface to be inspected (the surface W1 of the workpiece W) are compared.

  In this case, as described above with reference to FIG. 4, in the inspection unit 28, the illumination 60, the conversion lens 61, the zoom lens 62, and the CCD camera 63 are all inclined with respect to the surface W <b> 1 of the workpiece W. Therefore, for example, if the surface W1 of the workpiece W has irregularities, light and dark appear in the pixels a and b indicating the surface to be inspected (the surface W1 of the workpiece W) due to the irregularities.

  For this reason, the control device 70 can determine the presence or absence of unevenness on the surface W1 of the workpiece W from the image taken by the CCD camera 63 of the inspection means 28. Also in this case, the ratio of the luminance B of each pixel a, b indicating the surface to be inspected (the surface W1 of the workpiece W) is obtained, and there is no defect (unevenness) on the surface W1 of the workpiece W by the ratio. It becomes possible to judge whether. In addition, when the ratio of the luminance B is outside a predetermined range over a plurality of adjacent pixels a and b, the state of the surface W1 of the workpiece W may be determined to be defective.

  As described above, the appearance on the surface W1 side of the workpiece W is comprehensively inspected by the inspection means 26, 27, and 28 during the conveyance by the first conveyor 14. After the inspection by the inspection means 26, 27, and 28 is performed in this way, the workpiece W is conveyed to the terminal end of the first conveyor 14 by the first conveyor 14, and inverted by the inversion device 21. Thereafter, the workpiece W with the back surface W2 facing upward is supplied to the start end of the second conveyor 20. Then, the workpiece W is conveyed rightward in FIG. 1 by the second conveyor 20 with the back surface W2 facing upward.

  During the conveyance by the second conveyor 20, the inspection means 35, 36, and 37 are used to inspect the work W on the back surface W 2 side in the same manner as when the inspection means 26, 27, and 28 are previously inspected on the surface W 1 side of the work W. Each of these tests is performed. Thus, the control device 70 comprehensively determines the state of the work W on the front surface W1 side and the back surface W2 side. Then, when the workpiece W whose external appearance has been inspected on both the front surface W1 side and the rear surface W2 side is conveyed to the end portion of the second conveyor 20, the separation in the separation device 38 is performed under the control of the control device 70. Only the workpiece W having a normal appearance is carried out to the storage area 41. Therefore, according to this inspection system 1, it is possible to easily inspect for the presence or absence of shape defects such as chips, cracks, unevenness, etc. on the front and rear surfaces W1 and W2 of the workpiece W and their peripheral green parts, and the appearance without leisure is normal. Only the workpiece W can be selected and obtained.

  As mentioned above, although an example of preferable embodiment of this invention was demonstrated, this invention is not limited to the form shown above. The object to be inspected is not limited to the workpiece W such as a rare earth magnet, and the present invention can be applied to the appearance inspection of various other articles. Any one of the inspection means 26, 27, 28 may be arranged along the first conveyor 14, or the inspection means 26, 27, 28 may be arranged in any combination along the first conveyor 14. It may be arranged. Similarly, any one of the inspection means 35, 36, and 37 may be disposed along the second conveyor 20, and the inspection means 35, 36, and 37 may be arbitrarily arranged along the second conveyor 20. You may arrange in combination.

  Since the surface to be inspected of an object to be inspected varies in brightness due to color tone, roughness, gloss due to the presence or absence of plating, etc., it is common to install an illumination light source adjacent to the CCD camera. The light source may be a general illumination such as a fluorescent lamp, but it is preferable to uniformly illuminate the surface to be inspected from above with a brightness of 500 lux to 20000 lux with a ring-shaped halogen lamp. The CCD camera requires a color CCD when inspecting the color tone, but a mono-color CCD camera is sufficient when inspecting the surface of the rare earth sintered magnet. The number of pixels of the CCD camera is required to be 300,000 pixels or more, preferably 1 million pixels or more. As the number of pixels increases, fine inspection can be performed but noise also increases. Therefore, selection according to the inspection situation is necessary.

  When photographing with a CCD camera, the aperture is generally fully opened. It is desirable to shoot at a shutter speed of 1/1000 to 1/10000 seconds. If the surface to be inspected has a point-symmetric shape such as a circular shape, it is preferable to select two pixels that are point-symmetric with respect to the center point O and compare them as described with reference to FIG. If the surface to be inspected is a line-symmetric shape such as a quadrangle, it is preferable to select and compare two pixels that are line-symmetric with respect to the center line L, as described with reference to FIG.

  Further, when the luminance of the two selected pixels is compared and inspected, according to the knowledge of the present inventors, if the luminance ratio is between 0.7 and 1.3, it may be judged as normal. However, depending on the type of inspection, the range of the luminance ratio determined to be normal can be arbitrarily set. If this range is too narrow, there is a concern that a good product will be judged as a defective product, and conversely if it is too wide, there is a concern that a defective product will be judged as a good product. Considering these circumstances in advance, it is necessary to appropriately set a threshold value for judging a defective product and incorporate it into a judgment program to judge pass / fail. If these series of operations are performed by a program installed in the control device, it becomes possible to carry out an efficient visual inspection continuously. In addition, it is possible to carry out a more detailed inspection by screening not only in two stages of good and bad but also in three or more stages and repeating the inspection or introducing a part of the visual inspection.

  In the inspection system of the present invention described with reference to FIG. 1 and the like, a disk-shaped Nd—Fe—C—B system sintered magnet having a diameter of 6.5 mm and a thickness of 1.0 mm is used as a workpiece while being conveyed at a constant speed of 50 mm / sec. , The appearance of the workpiece was continuously inspected. A CS-3910 CCD camera manufactured by Seiko Optical MS-501 high resolution lens (1,410,000 pixels) is used, and the light source is a HL-28-2000 (28φ) ring-shaped halogen lamp manufactured by Seiwa Optical. It was. The outer shape of the workpiece was enveloped to determine the shape, and the image was taken when the center came to the center of the CCD camera. The aperture is fully open and the shutter speed is 1/2000 sec. A pixel that is point-symmetric is selected, and when the ratio of the luminance of the two is 1.4 or more is abnormal, it is set so that the appearance is judged to be defective when the abnormal pixels continue for 450 or more. 1000 workpieces were inspected according to the present invention. About the test used for an Example, it test | inspected also visually and the test result by visual inspection was made into the correct answer.

  Further, as an inspection method of the comparative example, about 10 points are selected from the pixels indicating the surface to be inspected in the image taken by the CCD camera, and the average value of the luminances is determined as a standard value. The condition of the article surface was inspected by comparing the brightness with this standard value. A comparison of the example of the present invention and the comparative example is as shown in Table 1. In the example of the present invention, both the correct answer rate of the non-defective product and the correct answer rate of the defective product were superior to the comparative example.

It is a top view showing a schematic structure of an inspection system concerning an embodiment of the invention. It is explanatory drawing of a test | inspection means. It is explanatory drawing of a test | inspection means with a large diameter light source. It is explanatory drawing of the test | inspection means with which the optical axis inclined. It is explanatory drawing of the state which selects two pixels which become point-symmetrical about the center point of the workpiece | work whose inspection surface is circular shape. It is explanatory drawing of the state which selects the two pixels which become line symmetrical about the centerline of the workpiece | work whose inspection surface is square shape. It is explanatory drawing of the state which selects two pixels which are point-symmetrical about the center point of the workpiece | work whose inspection surface is circular shape, and has shown the case where an outer periphery green part is test | inspected. It is explanatory drawing of the state which selects two pixels which are line-symmetrical about the centerline of the workpiece | work whose inspection surface is square shape, and has shown the case where an outer periphery part is test | inspected.

Explanation of symbols

W Work a, b Pixel 1 Inspection system 10 Hopper 11 Alignment feeder 12 Linear feeder 13 Cutting device 14 First conveyor 15, 16 Thickness inspection device 20 Second conveyor 21 Reversing device 25, 38 Sorting device 26, 27, 28 , 35, 36, 37 Inspection means 70 Control device

Claims (4)

A method of inspecting the surface of an article with a CCD camera and inspecting the surface of the article with the image, and selecting two pixels that are point-symmetric or line-symmetric from pixels indicating the surface to be inspected in the image And determining the luminance ratio of the two selected pixels, and determining that the state of the article surface is defective when the luminance ratio is outside a predetermined range over a plurality of adjacent pixels. to, inspection method. 2. The inspection method according to claim 1, wherein comparison is made for all of the pixels indicating the surface to be inspected. 3. The inspection method according to claim 1, wherein when the surface to be inspected of the article is photographed by a CCD camera, the surface to be inspected is illuminated by a light source. Inspection means comprising a light source that illuminates the image from almost right above the article and a CCD camera located directly above the article, a light source that illuminates the outer peripheral green part of the article, and a CCD camera located directly above the article; And an inspection means comprising a light source and a CCD camera arranged around an optical axis inclined obliquely with respect to a direction perpendicular to the surface of the article, The inspection method according to claim 1.

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