JP2014106141A - Defect inspection device and defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device and a defect inspection method capable of accurately detecting a defect in the vicinity of an edge part without providing a mask area in the edge part.SOLUTION: A filter processing unit 9 (filter means) for emphasizing the variation in density of an inspection object by filter processing with an m-row and n-column image filter (m and n are natural numbers equal to or lager than 2) includes: a first filter area summing part 94 which calculates a first addition signal by adding m×n pieces of inspection image data comprising n pieces of image data in a direction orthogonal to a movement direction of the inspection object and m pieces of inspection image data in the movement direction of the inspection object, out of inspection image data; a second filter area summing part 95 which calculates a second addition signal by adding m×n pieces of inspection image data in positions which are spaced from the pieces of inspection image data for the first addition signal in the movement direction of the inspection object by a prescribed number of rows; and a difference calculation part 96 which generates inspection image data after the filter processing on the basis of the difference between the first addition signal and the second addition signal.

Description

  The present invention relates to a defect inspection apparatus using an image processing apparatus and a defect inspection method.

  Conventionally, it is possible to detect wrinkles (defects) on the surface of a steel sheet on the basis of an image signal obtained by photographing the surface of a steel sheet to be passed in a steel sheet manufacturing process with an imaging device such as a CCD (Charge Coupled Device) camera (See Patent Document 1). However, the edge portion (end portion) of the steel sheet is sometimes detected as a defect because it is contaminated or brightness is increased by rubbing the edge portion. Although these are not defects, they often occur long in the plate passing direction of the steel plate and are difficult to distinguish from the edge portion on the image. As described above, there is a problem in that a non-defective product is determined as a defective product by erroneously detecting a so-called edge portion.

Japanese Patent No. 3119581

  In order to solve such a problem, conventionally, a certain area near the edge portion is masked to form a dead zone, and defect detection is not performed to suppress erroneous detection. Specifically, the position information of the edge part is obtained by an edge detector and an edge detection function, the edge part is determined, and the mask is directed from this edge part in a direction perpendicular to the conveying direction (moving direction) of the steel sheet. A width was set and a mask area where defect detection was not performed was set.

  On the other hand, the steel plate passing over the roll causes meandering called a walk. Therefore, it is necessary to set the mask width in anticipation of the meandering amount. For example, in the defect inspection process for a steel sheet, a mask area is about several tens of millimeters from both ends of the steel sheet, and there are areas that are not inspected. However, defects in the vicinity of the edge portion are likely to cause breakage of the steel sheet, and these are included in the mask region, so that there is a problem that a serious defect cannot be detected.

  The present invention has been made in view of the above points, and provides a defect detection apparatus and a defect detection method capable of accurately detecting a defect in the vicinity of an edge portion without providing a mask region at the edge portion. It is.

  In order to solve the above-described problems, a defect inspection apparatus according to the present invention includes a capturing unit that captures the color tone on the surface of an inspection object as inspection image data, and filters the inspection image data with an image filter. Filter means for emphasizing a change in density of the inspection object, and binarization means for binarizing the inspection image data after the filter processing by the filter means based on a preset threshold value. A defect inspection apparatus for detecting defects on the surface of the inspection object based on the data binarized by the binarization means, wherein the filter means includes the inspection object in the inspection image data. A first addition result obtained by adding inspection image data composed of a plurality of pixels in a direction orthogonal to the movement direction of the image and a plurality of pixels in the movement direction of the inspection object; Based on the difference between the first addition result and the second addition result composed of the same number of inspection image data as the first addition result at a position that is a predetermined number of rows away in the moving direction of the inspection object, after the filtering process The inspection image data is generated.

  In the defect inspection apparatus according to the aspect of the invention, the filter unit may include n (n ≧ an integer greater than or equal to 2) images in the direction orthogonal to the moving direction of the inspection object in the inspection image data. A first filter region summation unit for calculating a first addition signal by adding data and m × n inspection image data consisting of m (m ≧ 2 or more) in the moving direction of the inspection object; The first addition signal is a second filter region summing unit that calculates a second addition signal by adding m × n inspection image data at positions separated by a predetermined number of rows in the moving direction of the inspection object; A difference calculating unit that generates the inspection image data after the filtering process based on a difference between the first addition signal and the second addition signal; and m rows of images from the capturing unit with respect to the moving direction of the inspection object Data is read and the first frame is read. A setting line reading unit that outputs to the second filter region summing unit, and outputs to the second filter region summing unit, and outputs to the second filter region summing unit. It is characterized by having.

により前記第１加算信号を算出し、前記第２フィルタ領域合計部は、

により前記第２加算信号を算出し、前記差分算出部は、前記第１加算信号と前記第２加算信号との差分に基づいて、前記検査対象物の移動方向に対して直交する方向におけるｉ番目の列、前記検査対象物の移動方向におけるｊ番目の行の画素の濃度差Ｂ_ｉｊを演算して、フィルタ処理後の前記検査画像データとして出力することを特徴とする。 Further, the present invention provides the defect inspection apparatus, wherein a density value of pixels in p rows and q columns in the inspection image data is a _qp , and the predetermined number of rows is r (1 ≦ r <m) rows in the inspection image data. When the first filter region total part,

The first addition signal is calculated by the second filter area summation unit,

The second addition signal is calculated by the step, and the difference calculation unit is based on the difference between the first addition signal and the second addition signal, i-th in the direction orthogonal to the moving direction of the inspection object. The density difference B _ij of the pixel in the j-th row in the movement direction of the inspection object is calculated and output as the inspection image data after the filter processing.

  In the defect inspection apparatus according to the present invention, m rows and n columns as the size of the image filter and the predetermined number of rows can be set from the outside.

  Further, the present invention provides the defect inspection apparatus, wherein the preset threshold value is a first threshold value set corresponding to a case where it is determined that a defect on the surface of the inspection object is a dark defect; The second threshold value is set in correspondence with a case where it is determined that the defect on the surface of the inspection object is a bright defect.

  Further, in the defect inspection apparatus, when the density change of the inspection image data in a direction orthogonal to the moving direction of the inspection object exceeds a preset change amount, the column at the time when it exceeds the change amount An edge detection unit that determines an edge part of the inspection object, and two s (an integer greater than or equal to 2) × t (t ≧ 2 or more) with respect to a direction orthogonal to the moving direction of the inspection object A filter processing unit that calculates a difference between (integer) pieces of inspection image data and generates inspection image data after filter processing; and a first mode for performing defect inspection using the filter unit; A second mode in which a defect inspection is performed using an edge detection unit and the filter processing unit, and the defect is detected by switching between the first mode and the second mode. To do.

  In order to solve the above-described problem, the defect inspection method of the present invention includes a step of taking in the shade of color tone on the surface of an inspection object as inspection image data, and filtering the inspection image data with an image filter. And a binarization step for binarizing the inspection image data after the filter processing by the filter step based on a preset threshold value. And a defect inspection method for detecting a defect on the surface of the inspection object based on the data binarized by the binarization means, wherein the filtering step includes the inspection object of the inspection image data. A first addition obtained by adding inspection image data consisting of a plurality of directions in a direction orthogonal to the moving direction of the object and a plurality of directions in the moving direction of the inspection object. Based on the difference between the result and the first addition result, the second addition result consisting of the same number of inspection image data as the first addition result at a position separated by a predetermined number of rows in the moving direction of the inspection object, The inspection image data after the filter processing is generated.

  According to the present invention, since the first addition result and the second addition result obtained adjacent to the moving direction of the inspection object in the inspection image data related to the edge portion have substantially the same density, the filtering process is performed. The difference indicating the density change of the subsequent edge portion is almost zero. On the other hand, in the inspection image data, when there is a defect in the vicinity of the edge portion, the first addition result and the second addition result have different densities, so that the difference indicating the density change of the defective portion after the filter processing is zero. You can get a value that is not. Therefore, it is possible to generate inspection image data after filter processing including an edge portion without providing a mask area at the edge portion, and to detect a defect near the edge portion accurately.

It is a schematic block diagram of the defect inspection apparatus which concerns on this embodiment. 3 is a schematic configuration diagram of a filter processing unit 9 in the image processing apparatus 4. FIG. It is a conceptual diagram which shows an example of test | inspection image data. FIG. 6 is a diagram for explaining a filter processing unit 9;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Configuration of defect inspection equipment]
FIG. 1 is a schematic configuration diagram of a defect inspection apparatus according to the present embodiment.
In the present embodiment, an example of detecting a defective portion (bright defect, dark defect) will be described as an example of detecting the shade of color tone on the surface of the inspection object 1 shown in FIG.
Here, the bright defect means a portion having a lighter color tone than a normal portion where the surface of the inspection object 1 is not stained, dimples or protrusions (unevenness), and is a portion having a high density in inspection image data described later. . On the other hand, the dark defect means a portion having a darker color tone than a normal portion where the surface of the inspection object 1 is not dirty, dents or protrusions (unevenness), and is a portion having a low density in inspection image data described later.

  The inspection object 1 is a continuous sheet-like metal plate, a film, a cloth, a nonwoven fabric, a resin plate, and the like. In the present embodiment, a steel plate will be described as an example. The inspection object 1 is preferably long, and it is preferable to inspect the fixed line sensor 3 (described later) while the inspection object 1 is traveling in the length direction.

Next, the defect inspection apparatus according to the present embodiment includes an illumination device 2, a line sensor 3, an image processing device 4, a host computer 5, and an output device 6.
The illuminating device 2 is a line-shaped illuminating device arranged so that the longitudinal direction of the light irradiation range on the inspection object 1 is orthogonal to the traveling direction of the inspection object 1. As the illumination device 2, for example, a fluorescent lamp, rod illumination, optical fiber illumination, LED (Light Emitting Diode) illumination, or the like can be used.

The line sensor 3 is a line-shaped optical sensor arranged so that the longitudinal direction of the imaging range is orthogonal to the traveling direction of the inspection object 1.
The line sensor 3 receives reflected light or transmitted light from the inspection object 1 and supplies an electric signal (inspection image data) corresponding to the color tone of the surface of the inspection object 1 to the image processing device 4. In other words, the line sensor 3 outputs an electrical signal corresponding to the light intensity distribution on the surface of the inspection object 1 in units of lines (hereinafter referred to as inspection lines) orthogonal to the traveling direction of the inspection object 1. An example of the line sensor 3 is a CCD camera.
In the illustrated example, the line sensor 3 is arranged on the surface side of the inspection object 1 in the same manner as the illumination device 2 and receives reflected light from the inspection object 1. It is good also as a structure which arrange | positions the illuminating device 2 on the back side of the test target object 1 opposite to the line sensor 3, irradiates light from the back surface of the test target object 1, and the transmitted light is received by the line sensor 3.

  The image processing device 4 processes the signal supplied from the line sensor 3 based on a predetermined program, detects a defective portion of the inspection object 1, and supplies the detection result to the host computer 5. Details of the image processing apparatus 4 will be described later.

  The host computer 5 converts the detection result from the image processing device 4 into a format corresponding to the output form of the output device 6 and supplies it to the output device 6. The output device 6 outputs the inspection result in an appropriate output form. For example, a display or printer that visually displays the inspection result, an alarm device that issues an alarm when a defect is detected, or a combination thereof, An appropriate configuration may be adopted.

[Configuration of Image Processing Device 4]
Next, the image processing apparatus 4 described above will be described in detail.
The image processing apparatus 4 includes a filter processing unit 9, a threshold setting unit 10, a binarization unit 11, a run length encoding unit 12, and a connectivity processing unit 13.
The filter processing unit 9 is supplied with digital data representing, for example, an 8-bit density value (256 gradations), which is inspection image data supplied from the line sensor 3. Difference processing (filter processing) using an image filter is performed to emphasize density changes on the inspection object 1 (details will be described later).

The binarization unit 11 uses the first threshold th1 (bright → dark) set by the threshold setting unit 10 as the inspection image data (hereinafter, referred to as density value _Bij ) in which the defective portion is emphasized by the filter processing unit 9. , And the second threshold th2 (dark → light).
The threshold setting unit 10 includes a first threshold th1 (bright → dark) and a second threshold th2 (dark → bright) from the outside in advance of defect inspection according to the material, thickness, and the like of the inspection object 1. Is set.
There are two types of detection logic in the binarization unit 11. When detecting a bright defect, the binarization unit 11 sets an area having an output level greater than the second threshold th2 to “1”, and when detecting a dark defect, the binarization unit 11 selects an area having a level lower than the first threshold th1. 1 ”. That is, as a result of binarization by the binarization unit 11, the region corresponding to the defective portion is “1” and the region corresponding to the normal portion is “0”.

The run-length encoding unit 12 obtains the address of the change point from the binary data “0” to “1” or “1” to “0” of the binary data by the binarization unit 11. Run-length encoding is performed (see Patent Document 1).
The connectivity processing unit 13 performs connectivity processing on the run-length code that has been run-length encoded by the run-length encoding unit 12. Here, the connectivity processing refers to processing while comparing data in a plurality of continuous scanning lines between the lines. By performing this connectivity process, it is possible to recognize defects in the inspection object and measure morphological features.

[Configuration of Filter Processing Unit 9]
Next, the above-described filter processing unit 9 will be described in detail. FIG. 2 is a schematic configuration diagram of the filter processing unit 9 in the image processing apparatus 4.
The filter processing unit 9 includes a memory 91, a setting line reading unit 92, a filter size setting unit 93, a first filter region totaling unit 94, a second filter region totaling unit 95, and a difference calculation unit 96.

A memory 91 (capture means for capturing the color tone on the surface of the inspection object as inspection image data) captures and stores the inspection image data digitized into 8 bits from the line sensor 3 for each inspection line (row). .
The setting line reading unit 92 sets a start line (starting line) when each of the first filter region totaling unit 94 and the second filter region totaling unit 95 starts filter processing.
The starting row at which each of the first filter region totaling unit 94 and the second filter region totaling unit 95 starts the filtering process is a predetermined number of rows (number of rows) set by the filter size setting unit 93 in the first filter region totaling unit 94. Different lines depending on r). That is, the starting row where the second filter region starts the filtering process is the movement of the inspection object 1 by r rows as the number of image data rows with respect to the starting row where the first filter region totaling unit 94 starts the filtering process. The line preceding the direction.

The first filter region summation unit 94 and the second filter region summation unit 95 each have image filters of m rows and n columns (m and n are integers of 2 or more). The size (number of rows m and number of columns n) of the image filter is set by the filter size setting unit 93 in the first filter region totaling unit 94 and the second filter region totaling unit 95. Note that the number of rows m, the number of columns n, and the number of rows r (1 ≦ r <m) are determined by the user in consideration of the material of the inspection object 1 and the size of the expected result before starting the defect inspection. Then, it is set by inputting from outside the image processing apparatus 4. Note that the condition r <m is that if r = m, it is easy to overlook defects at the boundary portion of the region to be filtered, and therefore the boundary portion is accurately detected as r <m.
The first filter region summation unit 94 calculates the total value of m × n (a plurality of pixels) of the density values (hereinafter, a _qp ) of the pixels in the p rows and q columns of the inspection image data by the following formula. Then, a first addition signal (first addition result) is generated.

Further, the second filter area summation unit 95 calculates the total value of m × n pixel density values a _qp of the pixels in the p rows and q columns of the inspection image data, that is, the same number of pixels as the first addition signal, by the following equation. Then, a second addition signal (second addition result) is generated.

The difference calculation unit 96 calculates the inspection image data after the filter processing based on the following formula based on the difference between the first addition signal and the second addition signal.
B _ij = first addition signal−second addition signal B _ij is inspection image data after filter processing for the j-th row, and the pixel in the i-th column indicated by the pixel number (pixel No.) i in the line direction. This is a density difference from a pixel adjacent in the moving direction of the inspection object 1.

With the configuration described above, the filter processing unit 9 emphasizes the density difference between the normal part and the defective part in the image of the inspection object 1 by (m × n) times.
Further, in the inspection image data related to the edge portion, the first addition signal and the second addition signal obtained adjacent to the moving direction of the inspection object have substantially the same density. For this reason, the difference indicating the density change of the edge portion after the filter processing is almost zero, so that the edge portion is not erroneously determined as a defect, and the edge portion need not be inspected for inspection. In order to explain this point in detail, the operation when m = n = 2 and r = 1 in the above configuration will be described below as an operation of the embodiment.

[Operation of the embodiment]
FIG. 3 is a conceptual diagram illustrating an example of inspection image data. FIG. 4 is a diagram for explaining the filter processing unit 9.
FIG. 3A shows inspection image data captured by the memory 91. In FIG. 3 (a), the part delimited by a broken line in the horizontal direction indicates one line (row) of the inspection image data. Also, in FIG. 3A, four lines are shown as line (j−1), line j, line (j + 1), and line (j + 2) from the front to the rear with respect to the moving direction of the inspection object 1. Yes.
Further, in FIG. 3A, a portion delimited by a broken line in the vertical direction indicates one column of inspection image data. A portion divided by the row and the column is one pixel, and the pixel No. of the line sensor 3 is assigned to the pixels in one line as shown in FIGS. 3B to 3D.
FIG. 3A shows an edge portion of the inspection object 1, a bright defect 35A, a dark defect 35B, and a dark defect 35C. Note that, as shown in FIG. 3A, the dark defect 35C is a defect that is near the edge portion of the inspection target 1 and is included in the mask region, and thus is not an inspection target. It is a flaw. In addition, here, the defect included in the mask region is described as the dark defect 35C, but the defect may be a bright defect.

FIG. 3B to FIG. 3D show the pixel densities in line (j−1), line j, line (j + 1), and line (j + 2) for each pixel No. The vertical axis represents pixel density, and the horizontal axis represents pixel No.
As shown in FIG. 3B, the pixel density corresponding to the line (j-1) increases as the pixel No. increases with the edge portion of the inspection object 1 as a boundary. There is no constant value.

  As shown in FIG. 3C, the pixel density corresponding to the line j has dark defects 35C near the edge portion of the inspection object 1 as the pixel number increases. The density value is slightly higher in the two-pixel portion that includes it, and then shows a certain value because there is no defect. Further, the pixel density corresponding to the line j increases in density at the two pixels including the bright defect 35A, and returns to the original constant value again. Further, the pixel density corresponding to the line j thereafter shows a constant value, but the density value becomes low at the portion of the two pixels including the dark defect 35B, and returns to the original constant value again.

  As shown in FIG. 3D, the pixel density corresponding to the line (j + 1) is darkened in the vicinity of the edge portion of the inspection object 1 in the same manner as the change in the pixel density corresponding to the line j as the pixel number increases. Since there is a defect 35C, the density value is slightly higher at the two-pixel portion including the dark defect 35C with the edge portion as a boundary, and thereafter shows a constant value because there is no defect. Further, the pixel density corresponding to the line (j + 1) increases in density at the two pixels including the bright defect 35A, and returns to the original constant value again. Further, the pixel density corresponding to the line (j + 1) thereafter shows a constant value, but the density value decreases at the two pixels including the dark defect 35B, and returns to the original constant value again.

  As shown in FIG. 3E, the pixel density corresponding to the line (j + 2) is the edge of the inspection object 1 as the pixel number increases, as in the change in the pixel density corresponding to the line (j-1). The pixel density becomes high at the boundary, and thereafter a constant value is shown because there is no defect.

  As is clear from FIGS. 3C and 3D, the pixel density of the edge portion of the inspection object 1, the dark defect 35B, and the dark defect 35C are all low values and are distinguished from each other. It is difficult to attach. For this reason, conventionally, the edge portion of the inspection object 1 is detected, and mask areas are provided on both sides including the edge portion, so that they are not subjected to defect inspection. Thus, since the dark defect 35C existing in the vicinity of the edge portion of the inspection object 1 shown in FIG. 3A is included in the mask region, it could not be detected as a defect.

4 (a) to 4 (c) show the pixel densities of 2 (= m) adjacent lines out of line (j-1), line j, line (j + 1), and line (j + 2), respectively. The signals (the first addition signal and the second addition signal, respectively) added by the first filter region summation unit 94 and the second filter region summation unit 95 are shown for each pixel No. In each figure, the vertical axis represents pixel density (after addition), and the horizontal axis represents pixel No.
FIG. 4A shows the pixel density when the pixel No. of the line (j−1) shown in FIG. 3B increases and the pixel No. of the line j shown in FIG. 3C increases. The pixel density is the sum of these pixel densities.
FIG. 4B shows a case where the pixel density of the line j shown in FIG. 3C increases and the pixel No. of the line (j + 1) shown in FIG. 3D increases. The pixel density is the sum of these pixel densities.
In FIG. 4C, the pixel density when the pixel No. of the line (j + 1) shown in FIG. 3D increases and the pixel No. of the line (j + 2) shown in FIG. 3E increase. The pixel density is the sum of the pixel density when going.

Each of FIG. 4A to FIG. 4C shows the result of addition performed by the first filter region summation unit 94 and the second filter region summation unit 95. However, the setting line reading unit 92 is set so that the reading of the pixel density of the line by each filter region totaling unit is read by shifting by one line (= r).
That is, when the first filter area summation unit 94 reads the pixel density of the line j and the pixel density of the line (j + 1) and sums them (FIG. 4B shows the first addition signal as the sum result), the second The filter area summation unit 95 reads and sums the pixel density of the line (j−1) and the pixel density of the line j (FIG. 4A shows the second addition signal as the summation result).

  Further, when the first filter area summation unit 94 reads and sums the pixel density of the line (j + 1) and the pixel density of the line (j + 2) (FIG. 4 (c) shows the first addition signal as the summation result). The second filter area summation unit 95 reads and sums the pixel density of the line j and the pixel density of the line (j + 1) (FIG. 4B shows the second addition signal as the summation result).

In FIG. 4D and FIG. 4E, the difference calculation unit 96 is input from the first addition signal input from the first filter region summation unit 94 and the second filter region summation unit 95, respectively. The result of taking the difference from the second addition signal is shown.
FIG. 4D shows inspection image data after the filtering process for the j-th row, and the moving direction of the inspection object 1 of the pixel in the i-th column indicated by the pixel number (pixel No.) i in the line direction. Is a density difference between pixels adjacent to (line (j−1) and pixel in line (j + 1)). FIG. 4E shows the inspection image data after the filtering process for the (j + 1) -th row, and the inspection object of the pixel in the i-th column indicated by the pixel number (pixel No) i in the line direction. 1 is a density difference between pixels adjacent to one movement direction (pixels in line j and line (j + 2)).

Here, when these FIG.4 (d) and FIG.4 (e) are seen, the density | concentration difference of the edge part of the test object 1 is zero. Therefore, the binarization unit 11 uses the first threshold th1 (bright → dark) and the second threshold th2 (dark → bright) shown in each drawing to output the output result B _ij (after the filter processing) of the difference calculation unit 96. (Inspection image data)), any defect of the bright defect 35A, the dark defect 35B, and the dark defect 35C can be detected without erroneously detecting the edge portion of the inspection object 1. In particular, the dark defect 35C in the vicinity of the edge portion of the inspection object 1 is not included in the defect inspection because it is a defect included in the conventional mask region, but in the present embodiment, the first addition signal and the second A dark defect is detected by performing binarization processing based on the difference from the addition signal.
In the binarization unit 11, in the case of the bright defect 35 </ b> A, it is detected that the bright defect starts on the line j by being larger than the first threshold th <b> 1 as shown in FIG. 4D, and is shown in FIG. Thus, it is detected that the light defect ends in the line (j + 1) by becoming smaller than the second threshold th2.

  Further, in the case of the dark defect 35B and the dark defect 35C, the binarization unit 11 detects that the dark defect starts in the line j by becoming smaller than the second threshold th2, as shown in FIG. As shown in FIG. 4E, it is detected that the dark defect ends at the line (j + 1) by becoming larger than the first threshold th1.

  These determination results are processed by the run-length encoding unit 12, the connectivity processing unit 13, and the host computer 5, and in the output device 6, the bright defect 35A and the dark defect 35B are detected on the inspection image data. It is displayed how large the coordinates (i, j) exist (in this case, 2 × 2). Further, the edge portion of the inspection object 1 is erroneously detected as a defect and is not displayed on the output device 6. Therefore, it is not necessary to provide a mask region corresponding to the edge portion to prevent erroneous detection, and a defect located in the vicinity of the edge portion (in this case, the dark defect 35C) can be accurately detected.

  As described above, the defect inspection apparatus according to the present invention includes a memory 91 (capture means) that captures the color tone of the surface of the inspection object as inspection image data, and m rows and n columns (m, n) with respect to the inspection image data. n is a natural number greater than or equal to 2) and a filter processing unit (filter unit) that performs a filtering process to emphasize the density change of the inspection object, and after the filtering process by the filtering unit based on a preset threshold value A defect inspection unit including a binarization unit 11 (binarization unit) for binarizing inspection image data, and detecting defects on the surface of the inspection object based on the binarized data by the binarization unit Device.

  This filter means includes n (n is an integer greater than or equal to 2) image data in the line direction (direction orthogonal to the moving direction of the inspection object) and m in the moving direction of the inspection object in the inspection image data. A first filter region summation unit 94 (first filter region summation portion) for calculating a first addition signal by adding m × n inspection image data composed of (m ≧ 2), and a first addition A signal is a second signal that adds m × n inspection image data at positions separated by r (1 ≦ r <m) rows (predetermined number of rows) in the moving direction of the inspection object to calculate a second addition signal. A filter area totaling unit 95 (second filter area totaling unit), a difference calculating unit that generates inspection image data after filter processing based on a difference between the first addition signal and the second addition signal, and an inspection target from the capturing unit Read out m rows of image data in the moving direction of the object Output to the first filter area summing unit, and a setting line reading unit 92 (reading out m rows of image data, each of which differs from the m rows of image data by a predetermined number of rows, and outputting the data to the second filter region summing unit. Setting line reading unit).

  According to the present invention, the first addition signal, which is an output signal of the first filter region summation unit, obtained adjacent to the moving direction of the inspection object in the inspection image data related to the edge portion, and the second filter Since the second addition signal, which is the output signal of the region summing part, has substantially the same density, the difference indicating the density change of the edge part after the filter processing calculated by the difference calculating part is substantially zero. On the other hand, in the inspection image data, when there is a defect in the vicinity of the edge portion, the first addition signal and the second addition signal have different densities, so that the difference indicating the density change of the defective portion after the filter processing is zero. You can get a value that is not. Therefore, it is possible to generate inspection image data after filter processing including an edge portion without providing a mask area at the edge portion, and to detect a defect near the edge portion accurately.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

  For example, the above-described defect inspection apparatus is provided with an edge detection unit to detect an edge portion, and (s × t) (s and t are integers of 2 or more) image data in the line direction with respect to filter processing. It is good also as a structure further provided with the 2nd filter process part (filter process part) which performs the filter process which takes a difference. In this case, an operation mode in which defect detection is performed using the line detection unit and the second filter processing unit is referred to as a second mode. On the other hand, in the first mode, the above-described edge processing may not be detected, and the filter processing may be performed by the above-described filter processing unit. And it is good also as a structure which provides a change switch in the image processing apparatus 4 so that switching between a 1st mode and a 2nd mode may be switched prior to a defect detection.

  In addition, in the density change for each line (row) stored in the memory 91 (see, for example, FIG. 3B), the edge detection unit presets the density change of the inspection image data when the pixel number is increased. If it exceeds the amount of change, it is determined that the row that exceeds the change amount is the edge portion of the inspection object. Thereby, the coordinates (pixel No.) of the edge part in the line direction, that is, the column number can be obtained. Then, by setting the width for masking the edge portion based on the width assumed as the meandering amount with respect to the number of this column and not determining the defect in this setting range, the mask function can be functioned. it can. If the pixel No. obtained by edge detection changes within a predetermined range in the column direction (movement direction of the inspection object), it can be determined that the inspection object does not meander, If the predetermined range is exceeded, it can be determined that the inspection object is meandering (meandering follow-up function).

  In this way, in the defect inspection apparatus having the first mode and the second mode, first, the edge portion is detected using the second mode, and the edge portion is perpendicular to the moving direction of the inspection object. A predetermined width in consideration of the amount of meandering is provided on the outside with respect to the direction, and a region including the outside of the inspection object is set as an inspection object in the first mode. In the first mode, as described above, the defect inspection is performed with the region including the edge portion as an inspection target without masking the edge portion. Thus, by detecting the defect by switching between the first mode and the second mode, the edge portion is not erroneously detected as a defect, and the defect is present in any region inside or outside the edge portion. Even if there is a defect, it is possible to detect the defect, and for example, it is possible to exclude a defect located outside.

However, even in the first mode alone corresponding to the above-described embodiment, the edge portion can be detected as a defect. For example, defect detection is performed by changing the first threshold th1 and the second threshold th2 (which threshold is set near the center to widen the defect inspection range in the binarization unit). As a result, in the vicinity of the pixel No corresponding to the edge portion, the edge portion can be detected as a defect in the binarizing portion if the output signal of the difference calculating portion is not zero. Further, it is also possible to determine that the inspection target is meandering by detecting the change in the pixel No. at the edge portion by using the edge portion detection function as in the second mode.
In addition, regarding the determination of whether or not meandering, the first threshold value th1 and the second threshold value th2 are set so that bright defects and dark defects can be detected as in the above embodiment (the inspection range is narrowed). ), It is also possible by performing defect detection. In other words, when the inspection object greatly meanders, the edge portion is determined to be a defect. In such a case, it may be determined that the object is meandering.

  DESCRIPTION OF SYMBOLS 1 ... Inspection object, 2 ... Illuminating device, 3 ... Line sensor, 4 ... Image processing device, 5 ... Host computer, 6 ... Output device, 9 ... Filter processing part, 10 ... Threshold setting part, 11 ... Binarization part , 12 ... Run-length encoding unit, 13 ... Connectivity processing unit, 91 ... Memory, 92 ... Setting line reading unit, 93 ... Filter size setting unit, 94 ... First filter region summing unit, 95 ... Second filter region summing 96: Difference calculation unit 35A: Bright defect, 35B, 35C ... Dark defect, th1 ... First threshold, th2 ... Second threshold

Claims (7)

Capture means for capturing the shade of the color tone on the surface of the inspection object as inspection image data;
Filter means for applying a filtering process to the inspection image data with an image filter to emphasize density change of the inspection object;
Binarization means for binarizing the inspection image data after the filter processing by the filter means based on a preset threshold value, and based on the data binarized by the binarization means A defect inspection apparatus for detecting defects on the surface of the inspection object,
The filter means includes
A first addition obtained by adding inspection image data composed of a plurality of pixels in a direction orthogonal to the moving direction of the inspection object and a plurality of pixels in the moving direction of the inspection object among the inspection image data. Based on the difference between the result and the first addition result, the second addition result consisting of the same number of inspection image data as the first addition result at a position separated by a predetermined number of rows in the moving direction of the inspection object, A defect inspection apparatus that generates the inspection image data after the filter processing. The filter means includes
Among the inspection image data, n (n is an integer greater than or equal to 2) image data in a direction orthogonal to the movement direction of the inspection object and m (m is greater than or equal to 2) in the movement direction of the inspection object. A first filter region summation unit that adds m × n inspection image data consisting of (integer) to calculate a first addition signal;
The first addition signal is a second filter area summing unit that calculates a second addition signal by adding m × n inspection image data at positions separated by a predetermined number of rows in the moving direction of the inspection object;
A difference calculation unit that generates the inspection image data after the filter processing based on a difference between the first addition signal and the second addition signal;
The m rows of image data are read from the capturing means in the moving direction of the inspection object and output to the first filter area summing unit, and each of the m rows of image data differs from the m rows of image data by the predetermined number of rows. a setting line reading unit that reads out image data of m rows and outputs the image data to the second filter region totaling unit;
The defect inspection apparatus according to claim 1, further comprising: A _qp , a density value of pixels in p rows and q columns in the inspection image data,
When the predetermined number of rows is r (1 ≦ r <m) in the inspection image data,
The first filter area total part is:

To calculate the first addition signal,
The second filter region total part is:

To calculate the second addition signal,
The difference calculation unit
Based on the difference between the first addition signal and the second addition signal, the i-th column in the direction orthogonal to the movement direction of the inspection object, the j-th row in the movement direction of the inspection object The defect inspection apparatus according to claim 2, wherein a density difference B _{ij of a} pixel is calculated and output as the inspection image data after the filter processing.   4. The apparatus according to claim 2, wherein the image filter has a size of m rows and n columns and the predetermined number of rows can be set from the outside. 5. Defect inspection equipment.   The preset threshold value is a first threshold value set corresponding to a case where a defect on the surface of the inspection object is determined to be a dark defect, and a defect on the surface of the inspection object is a light defect. 5. The defect inspection apparatus according to claim 1, wherein the defect inspection apparatus is a second threshold value that is set in correspondence with a case where the determination is made. When the density change of the inspection image data in the direction orthogonal to the moving direction of the inspection object exceeds a preset amount of change, it is determined that the row when the density change exceeds the preset amount is the edge portion of the inspection object. An edge detector;
After filtering the difference between two s (integers greater than or equal to 2) × t (integers greater than or equal to t ≧ 2) pieces of inspection image data in the direction orthogonal to the moving direction of the inspection object A filter processing unit for generating inspection image data of
A first mode for performing defect inspection using the filter means; and a second mode for performing defect inspection using the edge detection unit and the filter processing unit;
Detecting a defect by switching between the first mode and the second mode;
The defect inspection apparatus according to any one of claims 1 to 5, wherein A capture step for capturing the shade of the color tone on the surface of the inspection object as inspection image data;
A filter step of emphasizing a change in density of the inspection object by applying a filtering process to the inspection image data with an image filter;
A binarization step for binarizing the inspection image data after the filter processing by the filter step based on a preset threshold value, and based on the binarized data by the binarization means A defect inspection method for detecting defects on the surface of the inspection object,
The filtering step includes
Of the inspection image data, a first addition result obtained by adding inspection image data consisting of a plurality of directions orthogonal to the movement direction of the inspection object and a plurality of movement directions of the inspection object; Based on the difference between the first addition result and the second addition result made up of the same number of inspection image data as the first addition result at a position separated by a predetermined number of rows in the moving direction of the inspection object, A defect inspection method, wherein the inspection image data is generated.

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