JP2011153874A - Apparatus, system and method for visual inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a defective area so that it is not interrupted, on the occasion of determining the quality of an inspection object. <P>SOLUTION: In a visual inspection system 1, an image processing part 321 of a visual inspection apparatus 3 prepares a differential binarized image, using a shade image. A first extraction part 322 extracts a pixel group composing the same defective candidate area. A detection part 324 detects a pixel of which the differential absolute value is a threshold or above, as an edge pixel, for each line. A second calculation part 326 determines a projection width in the horizontal direction and a projection width in the vertical direction about the defective area extracted by a second extraction part 325. A determination part 327 determines the inspection object A as faulty when at least either of the projection widths in the horizontal and vertical directions is larger than a reference value. The detection part 324 detects the edge pixel for each line sequentially from a line where a defective width determined by a first calculation part 323 is the maximum, and sets the threshold of a subsequent line so that the threshold of the subsequent line may become lower as the defective width gets narrower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an appearance inspection apparatus that inspects the quality of an inspection object using a gray-scale image obtained by imaging the inspection object, and an appearance inspection system and an appearance inspection method using the appearance inspection apparatus.

  Conventionally, various appearance inspection apparatuses for inspecting pass / fail of an inspection object have been developed and marketed. As an example of a conventional appearance inspection apparatus, a binarization process for binarizing the density value of each pixel is performed on a grayscale image (see FIGS. 16A and 16B) obtained by imaging the inspection object A. Devices for detecting defects are known. The appearance inspection apparatus detects, for example, a short circuit failure between the terminals A1 and A1 of the electronic component by detecting white pixels of the grayscale binarized image (see FIG. 16C) created by the binarization process. The foreign object A2 or the like that is caused is detected, and the quality of the inspection object A is determined.

  As another example of a conventional appearance inspection apparatus, there is known an apparatus that detects a defect by performing a differentiation process for differentiating the density value of each pixel of a grayscale image obtained by imaging an inspection object (for example, Patent Document 1). reference). The appearance inspection apparatus of Patent Document 1 differentiates the density value of each pixel of a grayscale image obtained by imaging a terminal, and classifies the direction of the terminal outline of each pixel into two directions according to the differentiation direction of each pixel. Then, the appearance inspection apparatus of patent document 1 calculates | requires the ratio of the number of each direction of the outline classified into two directions, and determines the presence or absence of the short circuit between terminals with the magnitude | size of the ratio.

JP-A-5-31730

  By the way, since the amount of reflected light changes for each part depending on the size of each part of the defect (metal foreign matter A2) of the inspection object A, in the grayscale image (see FIG. 16B) obtained by imaging the inspection object A, The density value of the pixel in the defective area (defective area) changes. For example, in a thin defect portion, the amount of reflected light decreases and the density value decreases. For this reason, in the conventional visual inspection apparatus, when the binarization process is performed on the grayscale image, the threshold value is a constant value (fixed value). Therefore, in the grayscale binary image, FIG. Like a region C1 and a region C2 shown, one defect is detected in a partially interrupted state. Even when differential processing is performed on a grayscale image, the differential value is small in a thin portion of a defect, and one defect is detected in a partially interrupted state.

  As described above, the conventional visual inspection apparatus has a problem that the size and length of the defect cannot be accurately detected.

  The present invention has been made in view of the above points, and an object of the present invention is to use an appearance inspection apparatus that can detect a defective area without interruption when determining the quality of an inspection object, and this appearance inspection apparatus. To provide an appearance inspection system and an appearance inspection method.

  The invention of an appearance inspection apparatus according to claim 1 is an appearance inspection apparatus that inspects the quality of the inspection object using a grayscale image in which the inspection object is imaged, wherein the pixel and the pixel for each pixel of the grayscale image An image processing unit that obtains a differential absolute value representing a change in density with respect to neighboring pixels of the pixel and binarizes the differential absolute value of each pixel to create a differential binary image, and is identical in the differential binary image A first extraction unit for extracting a pixel group constituting the defect candidate area, and a direction in which an angle between the horizontal direction and the vertical direction of the differential binarized image is small with respect to the longitudinal direction of the defect candidate area. In the differential binarized image, lines are set at predetermined intervals along a second direction orthogonal to the first direction, and the width of the defect candidate region in the second direction is set for each line. A first calculation unit for determining the defect width as A detection unit that detects, as an edge pixel, a pixel having a differential absolute value that is equal to or greater than a threshold value for each line; and a second area that extracts the defect area including the defect candidate area and having the edge pixel for each line as an outline An extraction unit; a first projection width when the defect area is projected onto a line along the first direction; and a second projection width when the defect area is projected onto a line along the second direction. A second calculation unit to be obtained; and a determination unit that determines that the inspection target is defective when at least one of the first projection width and the second projection width is greater than a preset reference value. The detection unit detects the edge pixel for each line in order from the line having the maximum defect width, and when detecting the edge pixel for each line, the smaller the defect width, The threshold is low And sets the threshold value of the next line so that.

  According to a second aspect of the present invention, in the first aspect, the first extraction unit extracts a plurality of pixel groups constituting the defect candidate region in the differential binarized image, and includes a plurality of the plurality of pixel groups. The defect candidate area having the largest projection width when projected onto the line along the first direction is selected as the maximum defect candidate area from the defect candidate areas, and the first calculation unit is configured to select the differential 2 The defect width of the maximum defect candidate region is obtained for each line in the digitized image.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the first calculation unit scans from one side for each line in the differentiated binary image, and the pixel value changes. A boundary where the pixel value is changed by scanning from the other side is detected as a second pixel, and an interval between the first pixel and the second pixel is defined as the defect width. It is characterized by seeking.

  According to a fourth aspect of the present invention, there is provided an appearance inspection apparatus according to any one of the first to third aspects, wherein the detection unit has the edge pixel as the defect width obtained by the first calculation unit is narrower. The detection range is set in accordance with the defect width for each line so that the detection range for detecting the noise becomes narrower.

  The invention of the appearance inspection apparatus according to claim 5 is the invention according to any one of claims 1 to 4, wherein when the determination unit determines that the inspection object is defective, The average of the density values of all the pixels included in the rectangular area circumscribing the defect area whose length is the first projection width and whose length in the second direction is the second projection width A third calculation unit that calculates a value as an average density value, and a second determination unit that determines that a metal foreign object is present in the defect area when the average density value is greater than a preset second reference value; It is characterized by providing.

  The appearance inspection apparatus according to claim 6 is the edge pixel of each line when the determination unit determines that the inspection object is defective in the invention according to any one of claims 1 to 4. A fourth calculation unit that obtains an average value of the density values as an average density value; and a second calculation unit that determines that a metal foreign matter is present in the defect area when the average density value is greater than a preset third reference value. 3 determination units.

  According to a seventh aspect of the present invention, there is provided a visual inspection system according to any one of the first to sixth aspects, and a grayscale image in which the inspection target is captured and the inspection target is output to the visual inspection apparatus. And an imaging device.

  The appearance inspection method according to claim 8 is an appearance inspection method for inspecting pass / fail of the inspection object using a grayscale image in which the inspection object is imaged, wherein the pixel and the pixel for each pixel of the grayscale image. A first step of obtaining a differential absolute value representing a change in density with respect to neighboring pixels and binarizing the differential absolute value of each pixel to create a differential binary image; and A second step of extracting a pixel group constituting the same defect candidate region and a direction in which an angle between the horizontal direction and the vertical direction of the differential binarized image is small with respect to the longitudinal direction of the defect candidate region is a first. The line is set at predetermined intervals along a second direction orthogonal to the first direction in the differential binarized image, and the width of the defect candidate region in the second direction is set for each line. The third step for determining the defect width as And a fourth step of detecting, as an edge pixel, a pixel having a differential absolute value equal to or greater than a threshold value for each line, and a defect area including the defect candidate area and having the edge pixel for each line as a contour line. A fifth step of extracting, and a first projection width when the defect area is projected onto a line along the first direction and a second projection when the defect area is projected onto a line along the second direction A sixth step of obtaining a width; and a seventh step of determining that the inspection object is defective when at least one of the first projection width and the second projection width is greater than a preset reference value. In the fourth step, when the edge pixel is detected for each line in order from the line having the maximum defect width, and the edge pixel is detected for each line, the defect width Narrow as the threshold value of the next line and sets the threshold value of the next line to be lower.

  According to the first, seventh, and eighth aspects of the present invention, even if there is a narrow portion in the defect area, the next line according to the defect width for each line in the defect candidate area that forms a part of the defect area The detection unit detects a pixel whose differential absolute value is equal to or greater than the threshold value while changing the threshold value as an edge pixel. Thus, according to the first, seventh, and eighth aspects of the invention, since an appropriate threshold value can be set for each location in the differentiated binarized image, it is possible to prevent the defective area from being detected in an interrupted state. As a result, according to the first, seventh, and eighth aspects of the present invention, the size of the defect area can be obtained with high accuracy, so that the accuracy of the quality determination of the inspection object can be increased.

  According to the second aspect of the present invention, it is possible to reduce the processing load by targeting only the largest defect candidate region among a plurality of defect candidate regions as compared to the case of targeting all defect candidate regions. Can do.

  According to the invention of claim 3, when the first calculation unit obtains the defect width of the defect candidate area, the edge pixel is always detected as an edge pixel by detecting a pixel that is a boundary that changes from the black area to the white area. The conditions for detecting can be specified as described above. Thus, according to the third aspect of the present invention, it is possible to reduce erroneous detection of noise or the like when determining the defect width, and to improve the accuracy of determining the defect width.

  According to the fourth aspect of the present invention, it is possible to reduce erroneous detection of noise when detecting edge pixels by limiting the detection range for detecting edge pixels by the detection unit. As a result, in the invention of claim 4, it is possible to further improve the accuracy of the quality determination of the inspection object.

  According to the invention of claim 5, when the average density value inside the rectangular area is larger than the second reference value, the second determination unit determines that the metal foreign matter exists in the defect area, so that the defect area Whether the foreign substance is a metal or another substance can be identified.

  According to the invention of claim 6, when the average density value of the edge pixels of the defect area is larger than the third reference value, the third determination unit determines that the metal foreign matter exists in the defect area, whereby the defect area It is possible to identify whether the foreign substance present in the metal is a metal or another substance.

It is a block diagram which shows the structure of the external appearance inspection system which concerns on Embodiment 1. FIG. It is a figure for demonstrating operation | movement of the external appearance inspection system which concerns on the same as the above. It is a figure which shows the pixel in the case of using a differential filter in the differential binarized image which concerns on the same as the above. It is a figure which shows the relationship between a defect width and a threshold value in the external appearance inspection system which concerns on the same as the above. It is a flowchart which shows the external appearance inspection method using the external appearance inspection system which concerns on the same as the above. 10 is a flowchart illustrating an appearance inspection method using the appearance inspection system according to the second embodiment. It is a figure for demonstrating operation | movement of the external appearance inspection system which concerns on Embodiment 3. FIG. It is a flowchart which shows the external appearance inspection method using the external appearance inspection system which concerns on the same as the above. It is a block diagram which shows the structure of the external appearance inspection system which concerns on Embodiment 4. It is a figure for demonstrating operation | movement of the external appearance inspection system which concerns on the same as the above. It is a flowchart which shows the external appearance inspection method using the external appearance inspection system which concerns on the same as the above. It is a block diagram which shows the structure of the external appearance inspection system which concerns on Embodiment 5. FIG. It is a figure for demonstrating operation | movement of the external appearance inspection system which concerns on the same as the above. It is a flowchart which shows the external appearance inspection method using the external appearance inspection system which concerns on the same as the above. (A) is a figure which shows the grayscale image of the test object to which the metal foreign material adhered, (b) is a figure which shows the differential binarized image created from the grayscale image of (a), (c) is a nonmetallic foreign material (D) is a figure which shows the differential binarized image created from the light and shade image of (c). It is a figure for demonstrating operation | movement of the conventional external appearance inspection apparatus.

(Embodiment 1)
The appearance inspection system according to the first embodiment is a system for inspecting pass / fail of an inspection target. As shown in FIG. 1, the appearance inspection system 1 of this embodiment includes an imaging device 2, an appearance inspection device 3, a display device 4, and an operation input device 5. An inspection object A shown in FIG. 1 is an electronic component having a plurality of terminals A1. The appearance inspection system 1 inspects the presence or absence of a short circuit between the terminals A1 and A1 particularly in the electronic component that is the inspection target A.

  The imaging device 2 is a CCD (Charge Coupled Device) camera, for example, and images the inspection target A. Image data of a grayscale image 6 (see FIG. 2A) obtained by imaging the inspection object A is output from the imaging device 2 to the appearance inspection device 3.

  The appearance inspection apparatus 3 includes an image capturing unit 31, a calculation unit 32, a storage unit 33, an image output unit 34, and an input interface 35. The appearance inspection apparatus 3 inspects the quality of the inspection object A using the grayscale image 6.

  The image capturing unit 31 is connected to the output side of the imaging device 2 and captures the grayscale image 6 captured by the imaging device 2.

  The calculation unit 32 includes an image processing unit 321, a first extraction unit 322, a first calculation unit 323, a detection unit 324, a second extraction unit 325, a second calculation unit 326, and a determination unit. 327. The computing unit 32 is constituted by a central processing unit (CPU) of a computer, for example.

  The image processing unit 321 calculates, for each pixel of the gray image 6, a differential absolute value abs representing a density change between the pixel and the peripheral pixel (a pixel around the pixel). Specifically, first, the image processing unit 321 performs the following differential operation using a differential filter. The differential filter of the present embodiment is a 3 × 3 filter. Examples of the differential filter include a Prewitt filter and a Sobel filter. The image processing unit 321 uses the center pixel P0 shown in FIG. 3 as a pixel of interest, and uses the density values of eight pixels (hereinafter referred to as “near 8”) P1 to P8 adjacent to the center pixel P0 in the horizontal direction (X direction). The density change ΔX and the density change ΔY in the vertical direction (Y direction) are obtained by the following equations 1 and 2. In Equations 1 and 2, P1 to P8 indicate the density values of the corresponding pixels P1 to P8.

  Subsequently, the image processing unit 321 obtains the differential absolute value abs (P0) of the pixel P0 by Expression 3.

  As is apparent from Equation 3, the differential absolute value abs (P0) represents the change rate of the density value in the vicinity region of the pixel P0. That is, the differential absolute value abs becomes larger as the density change is larger in the grayscale image 6.

  In addition, the differential filter of this embodiment is not limited to a 3x3 filter, For example, a 5x5 filter etc. may be sufficient.

  The image processing unit 321 creates a differential binarized image 7 by binarizing the differential absolute value abs of each pixel with a predetermined threshold. FIG. 2B shows the differential binarized image 7. In the differential binarized image 7 in FIG. 2B, the pixel having the differential absolute value abs above the threshold is white, and the pixel having the differential absolute value abs below the threshold is black. In the white portion of the differentiated binarized image 7, there are a plurality of defect candidate areas 72, each of which is a candidate for the defect area B, along with the outline 71 of each terminal A 1.

  The first extraction unit 322 shown in FIG. 1 extracts a plurality of pixel groups constituting the same defect candidate region 72 in the differentiated binarized image 7 by labeling processing. The labeling process is a process for recognizing a set of white pixels as a graphic component. The first extraction unit 322 checks whether each pixel is white or black in order from the upper left of the differentiated binarized image 7, and attaches the same label to the connected pixels among the white pixels. . The first extraction unit 322 projects the projection width in the horizontal direction (lateral direction in FIG. 2B) and the vertical direction (in FIG. 2) for each of the plurality of defect candidate regions 72 existing in the differentiated binarized image 7. The projection width in the vertical direction (b) is obtained. The projected width in the horizontal direction refers to the width when projected onto a line along the horizontal direction. The projected width in the vertical direction refers to the width when projected onto a line along the vertical direction. The first extraction unit 322 selects a defect candidate area 721 having the largest horizontal projection width as a maximum defect candidate area from among the plurality of defect candidate areas 721 to 723 (see FIG. 2C). In the present embodiment, since the angle between the longitudinal direction of the maximum defect candidate region 721 and the horizontal direction is smaller than the angle between the longitudinal direction and the vertical direction, the horizontal direction is the first direction and the vertical direction is the second direction. Direction.

  For each line L, the first calculation unit 323 obtains the vertical width of the maximum defect candidate region 721 as the defect width δ (see FIG. 2D). Each line L is set at predetermined intervals along a second direction orthogonal to the first direction in the differentiated binarized image 7. The defect width δ of each line L is stored in the storage unit 33.

  For each line L, the detection unit 324 detects a pixel whose differential absolute value abs is equal to or greater than a threshold value as an edge pixel. At this time, the detection unit 324 extracts the maximum value from the defect width δ stored in the storage unit 33, and detects edge pixels for each line L in order from the line L1 having the maximum defect width δ. Further, when detecting the edge pixel for each line L, the detection unit 324 sets the threshold value of the next line L so that the threshold value of the next line L becomes lower as the defect width δ is smaller. In other words, the detection unit 324 changes the threshold value for each line L so that the threshold value of the next line L becomes lower as the defect width δ is smaller, and detects pixels whose differential absolute value abs is greater than or equal to the threshold value as edge pixels. (See FIG. 2 (e)).

  When the line L having the maximum defect width δ is a line other than the end portion of the maximum defect candidate region 721, the detection unit 324 has one direction from the line L having the maximum defect width δ (for example, FIG. Edge pixels are first detected for each line L in order (in the right direction of e). Thereafter, the detection unit 324 detects edge pixels for each line L in order from the line L having the maximum defect width δ in another direction (for example, the left direction in FIG. 2E). The detection unit 324 may use the above-described method as a method for setting the threshold value of each line L, whether the edge pixel is detected in one direction or the edge pixel is detected in another direction.

  As shown in FIG. 4, the relationship between the defect width δ and the threshold value is such that the larger the defect width δ, the larger the threshold value. For example, in FIG. 2E, when detecting the edge pixel of the line L1, the detection unit 324 sets a threshold value in the line L2 using the defect width δ1 in the line L1. Since the line L1 is the first line, the threshold value in the line L1 is set using the defect width δ1 in the line L1.

  Subsequently, when detecting the edge pixel of the line L2, the detection unit 324 sets a threshold value in the line L3 using the defect width δ2 in the line L2. Furthermore, when detecting the edge pixel of the line L3, the detection unit 324 sets a threshold value in the line L4 using the defect width δ3 in the line L3. In addition, since the defect width δ is not obtained in the lines L4 to L11, the detection unit 324 uses the defect width δ3 in the immediately preceding line L3 among the lines L1 to L3 in which the defect width δ is obtained. The threshold values of the lines L4 to L11 are set.

  As described above, the detection unit 324 can detect an edge pixel by setting a threshold value for each of the lines L1 to L11.

  The second extraction unit 325 extracts the defect area B including the maximum defect candidate area 721 (see FIG. 2E). Specifically, the second extraction unit 325 extracts a region where the edge pixel for each line L is a contour line as the defect region B.

  The second calculation unit 326 calculates a horizontal projection width W1 and a vertical projection width W2 for the defect area B (see FIG. 2F). The horizontal projection width W1 refers to the projection width when projected onto a line along the horizontal direction (lateral direction in FIG. 2F). The projection width W2 in the vertical direction refers to the projection width when projected onto a line along the vertical direction (the vertical direction in FIG. 2F). The horizontal projection width W1 corresponds to the first projection width of the present invention. The projection width W2 in the vertical direction corresponds to the second projection width of the present invention.

  The determination unit 327 compares the horizontal projection width W1 obtained by the second calculation unit 326 with the reference value. Further, the determination unit 327 compares the projection width W2 in the vertical direction obtained by the second calculation unit 326 with the reference value. When at least one of the comparison result that the projection width W1 in the horizontal direction is larger than the reference value and the comparison result that the projection width W2 in the vertical direction is larger than the reference value is obtained, the determination unit 327 determines the inspection object A Is determined to be defective. The reference value is a value set in advance in the storage unit 33 before determination by the determination unit 327. The reference value to be compared with the horizontal projection width W1 and the reference value to be compared with the vertical projection width W2 may be the same value or different values.

  The storage unit 33 stores image data of the grayscale image 6 (see FIG. 2A) captured by the image capturing unit 31, or the differential binarized image 7 (FIG. 2) generated by the image processing unit 321. (B)) is stored. Further, the storage unit 33 stores the defect width δ obtained by the first calculation unit 323 for each line L. The image output unit 34 outputs the grayscale image 6 and the differentiated binarized image 7 to the display device 4. A user instruction is input to the input interface 35 from the operation input device 5.

  Next, an appearance inspection method for determining the quality of the inspection object A using the appearance inspection system 1 according to the present embodiment will be described with reference to FIG. First, the imaging device 2 images the inspection object A (S1 in FIG. 5). Subsequently, the image processing unit 321 of the appearance inspection apparatus 3 obtains a differential absolute value abs of each pixel of the grayscale image 6 (see FIG. 2A), binarizes the differential absolute value abs of each pixel, and performs differentiation 2 A digitized image 7 (see FIG. 2B) is created (S2). Thereafter, the first extraction unit 322 extracts a plurality of pixel groups constituting the same defect candidate region 72 in the differentiated binarized image 7 (S3). Further, the first extraction unit 322 obtains the projection width of each defect candidate area 72 (S4), and selects the maximum defect candidate area 721 from the plurality of defect candidate areas 72 (S5).

  Thereafter, the first calculation unit 323 sets lines L at predetermined intervals along the vertical direction in the differentiated binarized image 7. The first calculation unit 323 obtains the vertical width of the maximum defect candidate region 721 for each line L as the defect width δ (S6). At this time, the first calculation unit 323 selects the line L1 (see FIG. 2D) having the maximum defect width δ from the plurality of lines L (S7).

  Thereafter, the detection unit 324 detects an edge pixel for each line L (S8). At this time, the detection unit 324 detects edge pixels for each line L in order from the line L1 with the largest defect width δ, and when detecting the edge pixels of each line L, the smaller the defect width δ, the more The threshold of the next line L is set so that the threshold of the line L becomes low.

  After that, the second calculation unit 326 linearizes the edge pixels of each line L (S9), and extracts a defect region B in which the edge pixels for each line L become a contour line (S10). Thereafter, the second calculation unit 326 calculates a horizontal projection width W1 and a vertical projection width W2 for the defect region B (S11). Thereafter, the determination unit 327 determines whether or not the horizontal projection width W1 and the vertical projection width W2 are larger than the reference value (S12). When at least one of the horizontal projection width W1 and the vertical projection width W2 is larger than the reference value, the determination unit 327 determines that the inspection target A is defective (S13). When both the horizontal projection width W1 and the vertical projection width W2 are equal to or less than the reference value, the determination unit 327 determines that the inspection target A is a non-defective product (S14).

  As described above, according to the appearance inspection system 1 of the present embodiment, even if there is a narrow portion in the defect region B, the threshold value of the next line L according to the defect width δ for each line L in the defect candidate region 72. The detection unit 324 detects a pixel whose differential absolute value abs is equal to or greater than a threshold value as an edge pixel. Thereby, in the appearance inspection system 1 of this embodiment, since an appropriate threshold value can be set for each place in the differentiated binarized image 7, it is possible to prevent the defect area B from being detected in an interrupted state. As a result, in the appearance inspection system 1 of the present embodiment, the size of the defect area B can be obtained with high accuracy, so that the accuracy of the quality determination of the inspection object A can be increased.

  Further, according to the present embodiment, by targeting only the maximum defect candidate region 721 among the plurality of defect candidate regions 72, the appearance inspection apparatus 3 can compare with the case where all the defect candidate regions 72 are targeted. The processing load can be reduced.

  As a modification of the present embodiment, the appearance inspection system 1 may target all of the plurality of defect candidate areas 72. According to the above modification, the load of the arithmetic processing in the appearance inspection apparatus 3 increases, but the size of the defect area B can be obtained with higher accuracy.

(Embodiment 2)
The appearance inspection system 1 according to the second embodiment relates to the first embodiment in that the differential binarized image 7 is scanned from both (upper and lower) for each line L to detect a boundary where the pixel value changes. It differs from the appearance inspection system 1. In addition to the above, the appearance inspection system 1 of the present embodiment is the same as the appearance inspection system 1 of the first embodiment. The appearance inspection system 1 according to the present embodiment is shown in FIG. 1 in the same manner as the appearance inspection system 1 according to the first embodiment.

  The first calculation unit 323 of the visual inspection apparatus 3 according to the present embodiment scans from one side (above FIG. 2D) for each line L in the differentiated binary image 7 and changes the pixel value. (Boundary changing from black pixel to white pixel) is detected as the first pixel. Further, the first calculation unit 323 scans from the other side (below in FIG. 2D) and detects a boundary where the pixel value changes (a boundary where the black pixel changes to a white pixel) as the second pixel. To do. From the above, the first calculation unit 323 according to the present embodiment only needs to detect only a boundary that changes from a black pixel to a white pixel, and needs to detect a boundary that changes from a white pixel to a black pixel. Absent. Thereafter, for each line L, the first calculation unit 323 obtains the interval between the first pixel and the second pixel as the defect width δ.

  Next, an appearance inspection method using the appearance inspection system 1 according to the present embodiment will be described with reference to FIG. First, the appearance inspection system 1 of the present embodiment performs the processing from step S1 to step S5 of the first embodiment (S21 to S25 in FIG. 6).

  Thereafter, for each line L, the first calculation unit 323 scans from above to detect the first pixel, and scans from below to detect the second pixel. Thereafter, the first calculation unit 323 obtains the interval between the first pixel and the second pixel as the defect width δ (S26).

  Thereafter, the appearance inspection system 1 of the present embodiment performs the processing from step S7 to step S14 of the first embodiment (S27 to S34).

  As described above, according to the appearance inspection system 1 of the present embodiment, when the first calculation unit 323 obtains the defect width δ of the defect candidate region 72, the pixel that is always the boundary that changes from the black region to the white region is the edge pixel. By detecting as above, the condition for detecting the edge pixel can be specified as described above. Thereby, in the appearance inspection system 1 of the present embodiment, it is possible to reduce erroneous detection of noise or the like when obtaining the defect width δ, and to improve the accuracy of obtaining the defect width δ.

(Embodiment 3)
The appearance inspection system 1 according to the third embodiment is different from the appearance inspection system 1 according to the first embodiment in that the detection range 73 is limited when detecting edge pixels as shown in FIG. In addition to the above, the appearance inspection system 1 of the present embodiment is the same as the appearance inspection system 1 of the first embodiment. The appearance inspection system 1 according to the present embodiment is shown in FIG. 1 in the same manner as the appearance inspection system 1 according to the first embodiment.

  As shown in FIG. 7, the detection unit 324 of the appearance inspection apparatus 3 according to the present embodiment has a narrower detection range 73 for detecting edge pixels as the defect width δ obtained by the first calculation unit 323 is smaller. Thus, the detection range 73 is set for each line L according to the defect width δ.

  Next, an appearance inspection method using the appearance inspection system 1 according to the present embodiment will be described with reference to FIG. First, the appearance inspection system 1 of the present embodiment performs the processing from step S1 to step S7 of the first embodiment (S41 to S47 in FIG. 8).

  Thereafter, the detection unit 324 determines the detection range 73 for each line L according to the defect width δ so that the detection range 73 becomes narrower as the defect width δ obtained by the first calculation unit 323 is smaller ( S48). In the detection range 73, the detection unit 324 detects the edge pixel by changing the threshold value according to the defect width δ for each line L so that the threshold value becomes lower as the defect width δ is smaller (S49).

  Thereafter, the appearance inspection system 1 of the present embodiment performs the processing from step S9 to step S14 of the first embodiment (S50 to S65).

  As described above, according to the appearance inspection system 1 of the present embodiment, the detection unit 324 limits the detection range 73 for detecting edge pixels, thereby reducing detection of noise erroneously when detecting edge pixels. it can. As a result, in the appearance inspection system 1 of the present embodiment, the accuracy of the quality determination of the inspection object A can be further increased.

  As a modification of the present embodiment, the detection range 73 may be applied to the appearance inspection system 1 of the second embodiment.

(Embodiment 4)
Incidentally, FIG. 15A shows a grayscale image 6a of the inspection object A to which a metallic foreign matter (for example, a metal piece) A2 is attached, and FIG. 15B shows a differential image created from the grayscale image 6a. A binarized image 7a is shown. The differential binarized image 7a has a region 75 corresponding to the metal foreign matter A2. Further, FIG. 15C shows a grayscale image 6b of the inspection object A to which non-metallic foreign matter (for example, molding powder) A3 adheres, and FIG. 15D is created from the grayscale image 6b. A differentiated binary image 7b is shown. The differential binarized image 7b has a region 76 corresponding to the metal foreign matter A2. As shown in FIGS. 15B and 15D, with only the differential binarization process, the region 75 is a region corresponding to the metallic foreign matter A2, and the region 76 is a region corresponding to the nonmetallic foreign matter A3. Cannot be identified. For this reason, when inspecting only the presence or absence of the metallic foreign matter A2, the non-metallic foreign matter A3 is also detected, and thus overdetection occurs.

  Therefore, in the appearance inspection system 1 according to the fourth embodiment, the appearance inspection apparatus 3 includes a third calculation unit 361 and a second determination unit 362 as shown in FIG. Or non-metallic substance. In addition to the above, the appearance inspection system 1 of the present embodiment is the same as the appearance inspection system 1 (see FIG. 1) of the first embodiment.

  When the determination unit 327 determines that the inspection target A is defective, the third calculation unit 361, as shown in FIG. 10, includes the inside of the rectangular region 74 circumscribing the defect region B (the hatched portion in FIG. 10). ) Is determined as an average density value. The horizontal length of the rectangular area 74 is the horizontal projection width W1, and the vertical length of the rectangular area 74 is the vertical projection width W2.

  The second determination unit 362 illustrated in FIG. 9 compares the average density value obtained by the third calculation unit 361 with the second reference value. When the average density value is larger than the second reference value, the second determination unit 362 determines that a metal foreign matter exists in the defect region B. When the average density value is equal to or less than the second reference value, the second determination unit 362 determines that nonmetallic foreign matter exists in the defect region B. The second reference value is a value set in advance in the storage unit 33 before the determination by the second determination unit 362.

  Next, an appearance inspection method using the appearance inspection system 1 according to the present embodiment will be described with reference to FIG. First, the appearance inspection system 1 of the present embodiment performs the processing from step S1 to step S14 of the first embodiment (S61 to S74 in FIG. 11).

  When the determination unit 327 determines that the inspection target A is defective, the third calculation unit 361 obtains an average density value of pixels existing inside the rectangular region 74 (S75). Thereafter, the second determination unit 362 determines whether the average density value is greater than the second reference value (S76). When the average density value is larger than the second reference value, the second determination unit 362 determines that a metal foreign matter is present in the defect area B (S77). When the average density value is equal to or smaller than the second reference value, the second determination unit 362 determines that nonmetallic foreign matter exists in the defect region B (S78).

  As described above, according to the appearance inspection system 1 of the present embodiment, the second determination unit 362 determines that the metal foreign matter exists in the defect region B when the average density value inside the rectangular region 74 is larger than the second reference value. By determining, it is possible to identify whether the foreign matter in the defect area B is a metal or another substance.

  As a modification of the present embodiment, the third calculation unit 361 and the second determination unit 362 may be applied to the appearance inspection system 1 of the second and third embodiments.

(Embodiment 5)
In the appearance inspection system 1 according to the fifth embodiment, as shown in FIG. 12, the appearance inspection apparatus 3 includes a fourth calculation unit 371 and a third determination unit 372, so that the foreign matter in the defect region B is metal. Or non-metallic material. In addition to the above, the appearance inspection system 1 of the present embodiment is the same as the appearance inspection system 1 (see FIG. 1) of the first embodiment.

  When the determination unit 327 determines that the inspection target A is defective, the fourth calculation unit 371 uses the average value of the density values of the edge pixels of each line L as the average density value as illustrated in FIG. Ask.

  The third determination unit 372 shown in FIG. 12 compares the average density value with a third reference value. When the average density value is larger than the third reference value, the third determination unit 372 determines that a metal foreign matter exists in the defect region B. When the average density value is equal to or smaller than the third reference value, the third determination unit 372 determines that nonmetallic foreign matter exists in the defect region B. The third reference value is a value set in the storage unit 33 in advance before the comparison and determination by the third determination unit 372.

  Next, an appearance inspection method using the appearance inspection system 1 according to the present embodiment will be described with reference to FIG. First, the appearance inspection system 1 of the present embodiment performs the processing from step S1 to step S14 of the first embodiment (S81 to S94 in FIG. 14).

  When the determination unit 327 determines that the inspection target A is defective, the fourth calculation unit 371 obtains an average density value of the edge pixels of each line L (S95). Thereafter, the third determination unit 372 determines whether or not the average density value is greater than a third reference value (S96). When the average density value is larger than the third reference value, the third determination unit 372 determines that a metal foreign matter is present in the defect area B (S97). When the average density value is equal to or smaller than the third reference value, the third determination unit 372 determines that nonmetallic foreign matter exists in the defect region B (S98).

  As described above, according to the appearance inspection system 1 of the present embodiment, the third determination unit 372 if a metal foreign matter exists in the defect area B when the average density value of the edge pixels in the defect area B is larger than the third reference value. Can determine whether the foreign matter in the defect area B is a metal or another substance.

  As a modification of the present embodiment, the fourth calculation unit 371 and the third determination unit 372 may be applied to the appearance inspection system 1 of the second and third embodiments.

DESCRIPTION OF SYMBOLS 1 Appearance inspection system 2 Imaging device 3 Appearance inspection apparatus 321 Image processing part 322 1st extraction part 323 1st calculation part 324 Detection part 325 2nd extraction part 326 2nd calculation part 327 Determination part 361 3rd calculation Part 362 second determination part 371 fourth calculation part 372 third determination part 6, 6a, 6b grayscale image 7, 7a, 7b differential binary image 72 (721, 722, 723) defect candidate area 721 maximum defect Candidate area 73 Detection area 74 Rectangular area A Inspection object B Defect area abs Differential absolute value L (L1 to L11) Line δ (δ1 to δ3) Defect width W1 Horizontal projection width W2 Vertical projection width

Claims (8)

An appearance inspection apparatus that inspects the quality of the inspection object using a grayscale image obtained by imaging the inspection object,
An image for obtaining a differential absolute value representing a density change between the pixel and a pixel around the pixel for each pixel of the grayscale image and binarizing the differential absolute value of each pixel to create a differential binary image A processing unit;
A first extraction unit for extracting a pixel group constituting the same defect candidate region in the differentiated binarized image;
Of the horizontal direction and the vertical direction of the differential binarized image, a direction having a small angle with the longitudinal direction of the defect candidate region is defined as a first direction, and is orthogonal to the first direction in the differential binarized image. A first calculation unit that sets lines at predetermined intervals along the second direction and obtains the width of the defect candidate region in the second direction as a defect width for each line;
A detection unit that detects, as an edge pixel, a pixel whose differential absolute value is greater than or equal to a threshold for each line;
A second extraction unit that extracts the defect region including the defect candidate region and the edge pixel of each line being a contour line;
A second projection width is obtained for a first projection width when projected on the line along the first direction and a second projection width when projected on the line along the second direction with respect to the defect area. A calculation unit;
A determination unit that determines that the inspection target is defective when at least one of the first projection width and the second projection width is greater than a preset reference value;
The detection unit detects the edge pixel for each line in order from the line having the maximum defect width, and when detecting the edge pixel for each line, the narrower the defect width, the more the next line The visual inspection apparatus, wherein the threshold value of the next line is set so that the threshold value becomes low. The first extraction unit extracts a plurality of pixel groups constituting the defect candidate area in the differentiated binarized image, and projects the extracted pixel group onto a line along the first direction from the plurality of defect candidate areas. Select the defect candidate area with the largest projected width as the maximum defect candidate area,
The appearance inspection apparatus according to claim 1, wherein the first calculation unit obtains the defect width of the maximum defect candidate region for each line in the differential binarized image.   In the differential binarized image, the first calculation unit detects a boundary where the pixel value changes from one side for each line as a first pixel, and scans from the other side to change the pixel value. The appearance inspection apparatus according to claim 1, wherein a boundary is detected as a second pixel, and an interval between the first pixel and the second pixel is obtained as the defect width.   The detection unit detects the detection range according to the defect width for each line so that the detection range for detecting the edge pixel becomes narrower as the defect width obtained by the first calculation unit is narrower. The appearance inspection apparatus according to any one of claims 1 to 3, wherein: When the determination unit determines that the inspection target is defective, the length in the first direction is the first projection width, and the length in the second direction is the second projection width. A third calculation unit for obtaining an average value of density values of all pixels included in a rectangular area circumscribing the defect area as an average density value;
5. A second determination unit that determines that a metal foreign matter is present in the defect area when the average density value is larger than a preset second reference value. The visual inspection apparatus according to claim 1. A fourth calculation unit that obtains an average value of density values of the edge pixels of each line as an average density value when the determination unit determines that the inspection target is defective;
5. A third determination unit that determines that a metal foreign matter exists in the defect area when the average density value is larger than a preset third reference value. The visual inspection apparatus according to claim 1. The appearance inspection apparatus according to any one of claims 1 to 6,
An appearance inspection system comprising: an imaging device that images an inspection target and outputs a grayscale image obtained by capturing the inspection target to the appearance inspection device. An appearance inspection method for inspecting the quality of the inspection object using a grayscale image obtained by imaging the inspection object,
For each pixel of the grayscale image, a differential absolute value representing a density change between the pixel and a pixel around the pixel is obtained, and the differential absolute value of each pixel is binarized to create a differential binary image. 1 step,
A second step of extracting pixel groups constituting the same defect candidate region in the differentiated binarized image;
Of the horizontal direction and the vertical direction of the differential binarized image, a direction having a small angle with the longitudinal direction of the defect candidate region is defined as a first direction, and is orthogonal to the first direction in the differential binarized image. A third step of setting lines at predetermined intervals along the second direction and obtaining the width of the defect candidate area in the second direction as the defect width for each line;
A fourth step of detecting, as an edge pixel, a pixel whose differential absolute value is greater than or equal to a threshold value for each line;
A fifth step of extracting a defect region including the defect candidate region and the edge pixel for each line being a contour line;
A sixth step of obtaining a first projection width when the defect area is projected onto a line along the first direction and a second projection width when the defect area is projected onto a line along the second direction; ,
A seventh step of determining that the inspection object is defective when at least one of the first projection width and the second projection width is larger than a preset reference value;
In the fourth step, when the edge pixel is detected for each line in order from the line having the maximum defect width, and the edge pixel is detected for each line, the smaller the defect width, the more the next line The visual inspection method, wherein the threshold value of the next line is set so that the threshold value is low.