JP2014106109A - Inspection device, inspection method, inspection program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device, an inspection method, an inspection program and a recording medium capable of suppressing the processing time of defect inspection for inspecting the presence/absence of the defect of an object to be inspected from becoming excessively long, and accurately inspecting the presence/absence of the defect.SOLUTION: An inspection device (100) compares an image for inspection acquired by an imaging part (1) with a reference image preliminarily stored in a reference image storage part (221) to inspect the presence/absence of the defect of an object to be inspected. A determination part (216) defines the pixels under consideration of the reference image and the respective pixels of a peripheral pixel group as the candidates of pixels to be compared with respect to the pixels under consideration of one image for inspection to determine whether or not the pixels under consideration of the image for inspection are normal pixels. A calculating operation control part (217) allows a difference value calculation part (215) to end a difference value calculating operation to the pixels under consideration of one image for inspection when it is determined that the pixels under consideration of the image for inspection are normal pixels by the determination part (216).

Description

  The present invention relates to an inspection apparatus, an inspection method, an inspection program, and a recording medium on which the inspection program is recorded, for inspecting the presence or absence of defects on an inspection object.

  Inspected objects such as circuit boards on which circuit patterns to be mounted on liquid crystal panel displays, photomasks, etc., have defects such as adhesion of foreign matter or irregularities on the surface, etc. Treated as a good product. Therefore, it is necessary to inspect the presence or absence of defects before shipment of the object to be inspected.

  Conventionally, the inspection image acquired by imaging the inspection object is compared with a reference image that represents a state in which the inspection object is prepared in advance, so that the presence or absence of the defect of the inspection object is determined. An inspection apparatus for inspecting has been proposed. In such an inspection apparatus, when there is no difference between the inspection image and the reference image, the inspection object corresponding to the inspection image is determined as a non-defective product, and the inspection image and the reference image are determined. When the difference is recognized, the inspection object corresponding to the inspection image is determined as a defective product having a defect.

  When an inspection object is imaged in an inspection device to obtain an inspection image, luminance unevenness that is not related to defects, i.e., noise, due to the influence of aging deterioration of a lighting device that irradiates light to the inspection object, i.e., noise May occur in the inspection image. In the inspection image, when there is not much difference between the luminance value of the pixel corresponding to the defect and the luminance value of the pixel in which noise occurs, the above inspection apparatus distinguishes the pixel corresponding to the defect and the pixel in which noise occurs. As a result, there is a problem that the presence or absence of a defect in the inspection object cannot be accurately inspected.

  As a technique for solving such a problem, for example, in Patent Document 1, a pixel of interest is selected pixel by pixel from each pixel constituting an inspection image, and the selected pixel of interest (hereinafter referred to as “inspection image attention pixel”). ”), A target pixel of the reference image corresponding to the inspection image target pixel (hereinafter referred to as“ reference image target pixel ”), and a peripheral pixel group adjacent to the reference image target pixel (one for the reference image target pixel). A technique for inspecting the presence or absence of a defect in an object to be inspected is described by comparing luminance values with a pixel group consisting of a plurality of pixels at positions shifted by pixels.

  According to the technique described in Patent Document 1, with respect to one inspection image attention pixel, the luminance value difference value is obtained for each of a total of nine pixels, that is, the reference image attention pixel and each pixel in the peripheral pixel group. Calculate and compare the pixel with the smallest luminance value difference in the reference image and the inspection image attention pixel to determine whether the inspection image attention pixel is a pixel corresponding to the defect of the inspection object By doing this, it is possible to inspect for the presence or absence of a defect in the inspection object.

JP 2001-84379 A

  In recent years, circuit patterns as an example of an object to be inspected have been increasingly miniaturized circuit patterns. When such a circuit board is used as an object to be inspected, it is necessary to inspect for the presence or absence of defects using a high-definition image as an inspection image and a reference image in accordance with miniaturization of a circuit pattern.

  When inspecting the presence or absence of a defect using a high-definition image as an inspection image and a reference image, as in the technique described in Patent Document 1, an inspection image attention pixel, a reference image attention pixel, and the reference image When inspecting the presence / absence of a defect by comparing the luminance value with each pixel in a peripheral pixel group at a position shifted by one pixel with respect to the target pixel, it is possible to accurately inspect the presence / absence of a defect in the inspection object. It may not be possible.

  That is, when the inspection object is imaged to acquire an inspection image, the position of the inspection image may be shifted from the reference image due to vibration of a stage on which the inspection object is placed. When the positional deviation width of the inspection image with respect to the reference image exceeds the length of one pixel, the inspection image attention pixel, the reference image attention pixel, and a peripheral pixel group at a position shifted by one pixel from the reference image attention pixel In the technique described in Patent Document 1 in which the presence or absence of a defect is inspected by comparing the luminance value with each of the pixels, the pixel corresponding to the defect cannot be distinguished from the pixel in which the positional deviation has occurred. As a result, there is a problem that it is impossible to accurately inspect the presence or absence of a defect in the inspection object.

  For example, the range of the peripheral pixel group of the reference image to be compared with the inspection image target pixel in the inspection image is a position shifted by two pixels from a position shifted by one pixel with respect to the reference image target pixel, and a position shifted by three pixels. By enlarging, it is possible to accurately inspect for the presence or absence of a defect in the object to be inspected even when the inspection image is misaligned with respect to the reference image.

However, in the technique described in Patent Document 1, the difference value of the luminance value is calculated for each reference image target pixel and each pixel in the peripheral pixel group for one inspection image target pixel. Since each difference value is inspected for the presence or absence of a defect in the inspection object, the range of the peripheral pixel group of the reference image to be compared with the inspection image attention pixel in the inspection image is set to 1 for the reference image attention pixel. If it expanded from a position shifted pixel positions to displaced N pixel, the processing time of the defect inspection (2N + 1) becomes a ^{2/3 2} times the processing time becomes extremely long. For example, when the range of the peripheral pixel group of the reference image to be compared with the inspection image target pixel is expanded from a position shifted by 1 pixel to a position shifted by 5 pixels with respect to the reference image target pixel, the processing time of defect inspection ( ^{2 × 5 + 1) 2/} 3 2 ≒ becomes 13.4 times.

  An object of the present invention is to provide an inspection apparatus and an inspection method capable of suppressing an excessively long processing time for defect inspection for inspecting the presence or absence of defects in an inspection object and accurately inspecting for the presence or absence of defects. And an inspection program and a recording medium on which the inspection program is recorded.

The present invention is an inspection apparatus for inspecting the presence or absence of defects in an object to be inspected,
A reference image storage unit that stores in advance a reference image representing a state in which there is no defect in the inspection object, which is a reference for inspecting the presence or absence of the defect in the inspection object;
An imaging unit that images the object to be inspected and obtains an image for inspection;
An inspection image attention pixel selection unit that selects one inspection image attention pixel from a pixel constituting the inspection image in accordance with a predetermined first order;
A reference image attention pixel selection unit that selects a reference image attention pixel corresponding to the inspection image attention pixel from pixels constituting the reference image;
A peripheral pixel group extraction unit that extracts a peripheral pixel group composed of pixels located within a predetermined range around the reference image target pixel among the pixels constituting the reference image;
A difference value calculation unit that calculates a difference value between luminance values of the reference image target pixel and the peripheral pixel group with respect to a luminance value of the inspection image target pixel according to a predetermined second order;
A determination unit that determines whether or not an absolute value of the difference value is equal to or less than a predetermined threshold every time the difference value is calculated according to the second order by the difference value calculation unit;
A calculation operation control unit that controls a difference value calculation operation of the difference value calculation unit, and when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value, And a calculation operation control unit that ends the difference value calculation operation of the difference value calculation unit according to the second order.

In the inspection apparatus of the present invention, the difference value calculation unit is configured to calculate a difference value with a positive / negative sign as the difference value,
The determination unit calculates a second difference value having a positive / negative sign different from the first difference value after the difference value calculation unit calculates a first difference value having an absolute value larger than the threshold value. In addition, it is determined that the inspection image target pixel is a normal pixel.

Further, the present invention is an inspection method for inspecting the presence or absence of a defect of an object to be inspected, which is executed by the inspection apparatus,
A reference image storage step in which a reference image storage unit stores in advance a reference image representing a state in which there is no defect in the inspection object, which serves as a reference for inspecting the presence or absence of a defect in the inspection object;
An imaging step in which the imaging unit images the object to be inspected and obtains an image for inspection;
An inspection image attention pixel selection step in which an inspection image attention pixel selection unit selects one inspection image attention pixel from a pixel constituting the inspection image according to a predetermined first order;
A reference image attention pixel selection step in which a reference image attention pixel selection unit selects a reference image attention pixel corresponding to the inspection image attention pixel from pixels constituting the reference image;
A peripheral pixel group extracting unit that extracts a peripheral pixel group composed of pixels located within a predetermined range around the reference image attention pixel among the pixels constituting the reference image; and
The difference value calculation unit calculates a difference value between the luminance values of the reference image attention pixel and the peripheral pixel group with respect to the luminance value of the inspection image attention pixel according to a predetermined second order. Steps,
A determination step of determining whether or not the absolute value of the difference value is equal to or less than a predetermined threshold every time the difference value is calculated according to the second order by the difference value calculation unit;
The calculation operation control unit controls the difference value calculation operation of the difference value calculation unit, and when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value, A calculation operation control step of ending the difference value calculation operation of the difference value calculation unit according to the second order with respect to the inspection image attention pixel.

  The present invention is also an inspection program for causing a computer to execute the inspection method.

  The present invention is also a computer-readable recording medium on which the inspection program is recorded.

  According to the present invention, the inspection apparatus is an apparatus for inspecting the presence / absence of a defect in the inspection object, and includes a reference image storage unit, an imaging unit, an inspection image attention pixel selection unit, a reference image attention pixel selection unit, A peripheral pixel group extraction unit, a difference value calculation unit, a determination unit, and a calculation operation control unit are provided.

  The reference image storage unit stores in advance a reference image representing a state in which the inspection object is free of defects. The imaging unit captures an inspection object and acquires an inspection image. The inspection image attention pixel selection unit selects one inspection image attention pixel from the pixels constituting the inspection image according to a predetermined first order. The reference image attention pixel selection unit selects a reference image attention pixel corresponding to the inspection image attention pixel from the pixels constituting the reference image. The peripheral pixel extraction unit extracts a peripheral pixel group including pixels located in a predetermined range around the reference image attention pixel from among pixels constituting the reference image.

  Each time the inspection image attention pixel is selected according to the first order by the inspection image attention pixel selection unit, the difference value calculation unit calculates the reference image attention pixel and the peripheral pixel group with respect to the luminance value of the inspection image attention pixel. The difference value of the luminance value of each pixel is calculated according to a predetermined second order. Each time the difference value is calculated according to the second order by the difference value calculation unit, the determination unit calculates the absolute value of the difference value every time the difference value is calculated according to the second order by the difference value calculation unit. Then, it is determined whether or not it is equal to or less than a predetermined threshold value. The calculation operation control unit that controls the difference value calculation operation of the difference value calculation unit follows the second order with respect to the inspection image attention pixel when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value. The difference value calculation operation of the difference value calculation unit is terminated.

  In the inspection apparatus of the present invention configured as described above, the inspection image acquired by the imaging unit is compared with the reference image stored in advance in the reference image storage unit, thereby determining whether there is a defect in the inspection object. At the time of inspection, the determination unit determines that not only the reference image attention pixel but also each pixel in the peripheral pixel group is a candidate pixel for comparison with respect to one inspection image attention pixel, and the inspection image attention pixel is a normal pixel. It is determined whether or not. Therefore, the inspection apparatus can accurately inspect for the presence or absence of a defect in the object to be inspected even when the inspection image is misaligned with respect to the reference image.

  Furthermore, in the inspection apparatus of the present invention, the calculation operation control unit follows the second order for one inspection image attention pixel when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value. The difference value calculation operation of the difference value calculation unit is terminated. The difference value calculation unit controlled by the calculation operation control unit does not calculate the difference value for all the pixels of the reference image target pixel and the peripheral pixel group, but the absolute value of the difference value is less than or equal to the threshold value by the determination unit When it is determined that the difference value calculation operation for one inspection image pixel of interest is completed, it is possible to prevent the processing time of the defect inspection for inspecting the presence or absence of the defect of the inspection object from becoming too long. Can do.

  According to the invention, the inspection method is executed by the inspection apparatus. The inspection method of the present invention includes a reference image storage step executed by the reference image storage unit, an imaging step executed by the imaging unit, and an inspection image attention pixel selection step executed by the inspection image attention pixel selection unit. A reference image attention pixel selection step executed by the reference image attention pixel selection unit, a peripheral pixel group extraction step executed by the peripheral pixel group extraction unit, a difference value calculation step executed by the difference value calculation unit, and a determination A determination step executed by the unit, and a calculation operation control step executed by the calculation operation control unit.

  In the inspection method of the present invention, the inspection step acquired by the imaging step and the reference image stored in advance in the reference image storage step are compared to determine whether or not there is a defect in the inspection object. Then, with respect to one inspection image attention pixel, not only the reference image attention pixel but also each pixel in the peripheral pixel group is determined as a pixel candidate for comparison, and it is determined whether or not the inspection image attention pixel is a normal pixel. . Therefore, in the inspection method, it is possible to accurately inspect the presence / absence of a defect in the inspection object even when the inspection image is misaligned with respect to the reference image.

  Furthermore, in the inspection method of the present invention, in the calculation operation control step executed by the calculation operation control unit, when it is determined in the determination step that the absolute value of the difference value is equal to or less than the threshold value, one inspection image target pixel is detected. Then, the difference value calculation operation of the difference value calculation unit according to the second order is terminated. The difference value calculation unit controlled by the calculation operation control unit does not calculate the difference value for all the pixels in the reference image target pixel and the surrounding pixel group, but the absolute value of the difference value is equal to or less than the threshold value in the determination step. When it is determined that the difference value calculation operation for one inspection image pixel of interest is completed, it is possible to prevent the processing time of the defect inspection for inspecting the presence or absence of the defect of the inspection object from becoming too long. Can do.

  According to the invention, the inspection program is a program for causing a computer to execute the inspection method. Such an inspection program can suppress the processing time of the defect inspection for inspecting the presence or absence of a defect in the inspection object from being excessively long and can accurately inspect the presence or absence of the defect. Can be controlled by software.

  According to the present invention, the recording medium is a computer-readable medium on which the inspection program is recorded. Therefore, the inspection apparatus can be realized on the computer by the inspection program read from the recording medium.

It is a block diagram which shows the structure of the test | inspection apparatus 100 which concerns on 1st Embodiment of this invention. 3 is a flowchart showing an inspection method executed by the inspection apparatus 100. 3 is a flowchart showing an inspection method executed by the inspection apparatus 100. FIG. 10 is a diagram for explaining operations of an inspection image attention pixel selection unit 212, a reference image attention pixel selection unit 213, and a peripheral pixel group extraction unit 214. It is a figure for demonstrating the determination operation | movement of the determination part. It is a figure for demonstrating the determination operation | movement of the determination part.

  FIG. 1 is a block diagram showing a configuration of an inspection apparatus 100 according to the first embodiment of the present invention. The inspection apparatus 100 of this embodiment is an apparatus for inspecting the presence / absence of a defect in the inspection object W. Examples of the inspected object W include a circuit board on which a circuit pattern mounted on a liquid crystal panel display, a photomask, or the like is formed. The inspection device 100 includes an imaging unit 1, an image processing device 2, an output device 3, and a transport unit 4.

  The transport unit 4 is a part for moving the object W to be inspected relative to the imaging unit 1, and includes a stage 41, a stage moving mechanism 42, a base 43, and a drive control device 44.

  The stage 41 is a so-called XYθ stage placed on the base 43, and is movable in the main scanning direction and the sub-scanning direction, and further in the rotation direction. Such a stage 41 has a flat plate-like outer shape, and places an object W to be inspected and held on the upper surface thereof. A plurality of suction holes (not shown) are formed on the upper surface of the stage 41. By forming a negative pressure (suction pressure) in the suction holes, the object to be inspected W placed on the stage 41 is fixedly held. The

  The stage moving mechanism 42 is a mechanism that moves the stage 41 by transmitting the driving force from the drive control device 44 to the stage 41. For example, the stage moving mechanism 42 includes a motor provided on each axis of XYθ of the stage 41.

  The imaging unit 1 captures an inspected object W to acquire an inspection image, and is a CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) two-dimensional image sensor, one-dimensional image sensor, scanner. Etc. The imaging unit 1 is disposed above the stage 41 and captures an inspection image by capturing an image of the inspection object W transported and moved by the stage 41 while being held on the stage 41.

  The image processing apparatus 2 is realized by a personal computer (PC), for example, and includes an image comparison unit 21 and a storage unit 22.

  The image comparison unit 21 inspects the presence / absence of a defect in the inspection object W by comparing the inspection image acquired by the imaging unit 1 with a reference image stored in advance in a reference image storage unit 221 described later. Part. The image comparison unit 21 includes an inspection image correction unit 211, an inspection image attention pixel selection unit 212, a reference image attention pixel selection unit 213, a peripheral pixel group extraction unit 214, a difference value calculation unit 215, a determination unit 216, and a calculation. An operation control unit 217 is included.

  The inspection image correction unit 211 performs deformation processing such as movement and rotation on the inspection image in order to correct the positional deviation of the inspection image acquired by the imaging unit 1 with respect to the reference image.

  The inspection image attention pixel selection unit 212 selects each pixel constituting the inspection image as an inspection image attention pixel one pixel at a time in accordance with a predetermined first order. For each pixel constituting the inspection image, a coordinate value representing a position in the inspection image is set. For example, when the inspection image is viewed from the front, the coordinate value of the pixel located at the upper left is (0 , 0), a coordinate value is set in which the right side of (0, 0) is the positive direction of the X coordinate and the lower side of (0, 0) is the positive direction of the Y coordinate.

  When the inspection image is a rectangular image composed of Xn pixels in the positive direction of the X coordinate and Yn in the positive direction of the Y coordinate, which is a total of (Xn × Yn) pixels, the inspection image is focused The pixel selection unit 212 starts from a pixel having a coordinate value (0, 0) as a starting point, and (0, 0), (1, 0), (2, 0)... (Xn−3, 0) (Xn−2, 0) ), (Xn−1,0) in the order of (Xn−1,0), the inspection image attention pixel is selected one by one, and then the coordinate value (0,1), (1,1), (1, 2,1)... (Xn-3,1), (Xn-2,1), (Xn-1,1) are selected pixel by pixel for inspection one by one in the order, and (0, Yn) in the same manner. -1), (1, Yn-1), (2, Yn-1) ... (Xn-3, Yn-1), (Xn-2, Yn-1), (Xn-1, Yn-1) Image for inspection one pixel at a time To select the eye pixels.

  The reference image attention pixel selection unit 213 selects a reference image attention pixel which is a pixel corresponding to the inspection image attention pixel from each pixel constituting the reference image stored in advance in a reference image storage unit 221 described later. As with the inspection image, each pixel constituting the reference image has a coordinate value representing a position in the reference image. When the reference image is viewed from the front, the coordinate value of the pixel located at the upper left is As (0, 0), a coordinate value is set such that the right side of (0, 0) is the positive direction of the X coordinate and the lower side of (0, 0) is the positive direction of the Y coordinate. The reference image attention pixel selection unit 213 selects a pixel having the same coordinate value as the inspection image attention pixel selected by the inspection image attention pixel selection unit 212 as the reference image attention pixel.

  The peripheral pixel group extraction unit 214 extracts a peripheral pixel group including a plurality of pixels located within a predetermined range around the reference image target pixel from among the pixels of the reference image. The peripheral pixel group extraction unit 214 extracts, for example, a total of 24 pixels at positions shifted by two pixels with respect to the reference image target pixel as the peripheral pixel group.

  Each time the inspection image attention pixel selection unit 212 selects the inspection image attention pixel according to the first order, the difference value calculation unit 215 performs the reference image attention pixel and the peripheral pixels with respect to the luminance value of the inspection image attention pixel. The difference value of the luminance value of each pixel of the group is calculated according to a second order that is determined in advance. The difference value calculation unit 215 is configured to calculate a difference value with a positive / negative sign as the difference value.

  Specifically, when the difference value calculation unit 215 starts the difference value calculation operation, first, of the pixels of the reference image attention pixel and the peripheral pixel group, the coordinates at which the X coordinate value and the Y coordinate value are minimum A pixel having a value (this coordinate value is assumed to be “(Xj, Yj)”) is selected as a difference value calculation target pixel, and a difference value of luminance values between the selected pixel and the inspection image attention pixel is calculated. . The difference value calculation unit 215 selects pixels for which a difference value is to be calculated pixel by pixel in the order of (Xj, Yj), (Xj + 1, Yj), (Xj + 2, Yj)... (Xj + n, Yj), and the selected pixels And a difference value of luminance values between the inspection image attention pixel and the inspection image attention pixel. Next, the difference value calculation unit 215 performs pixel-by-pixel order in the order of coordinate values (Xj, Yj + 1), (Xj + 1, Yj + 1), (Xj + 2, Yj + 1)... (Xj + n, Yj + 1) with the Y coordinate value increased by “1”. The difference value calculation target pixel is selected, and the difference value of the luminance value between the selected pixel and the inspection image attention pixel is calculated. Next, the difference value calculation unit 215 similarly selects pixels for which difference values are to be calculated one by one in the order of (Xj, Yj + n), (Xj + 1, Yj + n), (Xj + 2, Yj + n)... (Xj + n, Yj + n). Then, the difference value of the luminance value between the selected pixel and the inspection image target pixel is calculated. In this way, the difference value calculation unit 215 performs the reference image for the luminance value of the inspection image attention pixel every time the inspection image attention pixel is selected according to the first order by the inspection image attention pixel selection unit 212. A difference value between the luminance values of the pixel of interest and each pixel in the peripheral pixel group is calculated in accordance with a predetermined second order.

  Whenever the difference value is calculated by the difference value calculation unit 215 according to the second order, the determination unit 216 determines whether the inspection image target pixel is a normal pixel corresponding to a normal part other than the defect of the inspection object W. Determine whether or not. The determination unit 216 determines that the inspection image attention pixel is a normal pixel when the absolute value of the difference value calculated by the difference value calculation unit 215 is equal to or less than a predetermined threshold, and the absolute value of the difference value Exceeds the threshold, it is determined that the inspection image target pixel is a defective pixel. The determination unit 216 calculates a second difference value having a positive / negative sign that is different from the first difference value after the difference value calculation unit 215 calculates the first difference value having an absolute value larger than the threshold value. In this case, it is determined that the inspection image target pixel is a normal pixel.

  The calculation operation control unit 217 controls the difference value calculation operation of the difference value calculation unit 215. The calculation operation control unit 217, when the determination unit 216 determines that the inspection image attention pixel is a normal pixel, the difference value calculation unit 215 according to the second order for one inspection image attention pixel. The difference value calculation operation is terminated.

  The storage unit 22 includes a reference image storage unit 221, a threshold storage unit 222, a normal pixel coordinate value storage unit 223, and a defective pixel coordinate value storage unit 224.

  The reference image storage unit 221 stores in advance a reference image that is an image representing a state in which the inspection subject W has no defect. The threshold storage unit 222 stores the threshold used during the determination operation by the determination unit 216. The normal pixel coordinate value storage unit 223 stores a coordinate value representing the position in the inspection image of the inspection image attention pixel determined to be a normal pixel by the determination unit 216. The defective pixel coordinate value storage unit 224 stores a coordinate value representing a position in the inspection image of the inspection image attention pixel determined to be a defective pixel by the determination unit 216.

  The output device 3 is realized by a display device or the like, and stored in the defective pixel coordinate value storage unit 224 and the coordinate value of the inspection image attention pixel representing the normal pixel stored in the normal pixel coordinate value storage unit 223. The coordinate value of the inspection image target pixel representing the defective pixel is output and displayed on the display screen. An operator who operates the inspection apparatus 100 can confirm the position of the pixel corresponding to the defect in the inspection image by confirming each coordinate value output by the output device 3, and as a result, The position of the defect in the body W can be confirmed. The output device 3 may be a recording disk device that records the coordinate values in a file, or a network communication device that transmits information on the coordinate values to an external computer device. Good.

  In the inspection apparatus 100 of the present invention configured as described above, the inspection object W is compared by comparing the inspection image acquired by the imaging unit 1 with the reference image stored in the reference image storage unit 221 in advance. When inspecting for the presence or absence of defects, the determination unit 216 uses not only the reference image attention pixel but also each pixel in the peripheral pixel group as a comparison target pixel candidate for one inspection image attention pixel. It is determined whether or not the pixel is a normal pixel. Therefore, the inspection apparatus 100 can accurately inspect for the presence or absence of a defect in the inspection object W even when the inspection image is misaligned with respect to the reference image.

  Furthermore, in the inspection apparatus 100 according to the present embodiment, the calculation operation control unit 217 determines that one inspection image attention pixel is a normal pixel by the determination unit 216, with respect to one inspection image attention pixel. The difference value calculation operation of the difference value calculation unit 215 according to the second order is terminated. The difference value calculation unit 215 controlled by the calculation operation control unit 217 does not calculate the difference values for all the pixels in the reference image attention pixel and the surrounding pixel group, but the inspection image attention pixel by the determination unit 216. When it is determined that the pixel is a normal pixel, the difference value calculation operation for one image target pixel for inspection is terminated, so that the processing time of the defect inspection for inspecting the presence or absence of the defect of the inspected object W becomes too long. Can be suppressed.

  Next, an inspection method executed by the inspection apparatus 100 will be described. 2A and 2B are flowcharts showing an inspection method executed by the inspection apparatus 100. FIG. The inspection method executed by the inspection apparatus 100 will be described with reference to FIGS. FIG. 3 is a diagram for explaining operations of the inspection image attention pixel selection unit 212, the reference image attention pixel selection unit 213, and the surrounding pixel group extraction unit 214. 4 and 5 are diagrams for explaining the determination operation of the determination unit 216. FIG.

  In step s1 corresponding to the reference image storage step, the reference image storage unit 221 stores the reference image in advance. Next, in step s2 corresponding to the imaging step, the imaging unit 1 captures the inspection object W transported and moved by the stage 41 while being held by the stage 41, and acquires an inspection image. Next, in step s3, the inspection image correction unit 211 performs a deformation process on the inspection image acquired by the imaging unit 1, and corrects the positional deviation of the inspection image with respect to the reference image.

  Next, in step s4, the image comparison unit 21 reads and acquires the reference image stored in the reference image storage unit 221 from the reference image storage unit 221. Next, in step s5, the image comparison unit 21 reads out and acquires the threshold value used in the determination operation by the determination unit 216 in the subsequent step from the threshold storage unit 222.

  Next, in step s6 corresponding to the inspection image attention pixel selection step, the inspection image attention pixel selection unit 212 determines in advance from each pixel constituting the inspection image G1, as shown in FIG. The inspection image attention pixel G11 is selected pixel by pixel according to the first order.

  Next, in step s7, the image comparison unit 21 determines whether or not the selection operation for selecting the inspection image attention pixel by the inspection image attention pixel selection unit 212 is completed. When the difference value calculation operation by the difference value calculation unit 215 described later is performed using all the pixels constituting the inspection image G1 as the inspection image attention pixel G11, the image comparison unit 21 displays the inspection image attention pixel. It is determined that the selection operation for selecting the pixel of interest for inspection by the selection unit 212 has been completed. If the image comparison unit 21 determines that the selection operation has been completed, the process proceeds to step s8. If the image comparison unit 21 determines that the selection operation has not been completed, the process proceeds to step s9.

  In step s8, the output device 3 displays the coordinate value of the inspection image attention pixel G11 representing the normal pixel stored in the normal pixel coordinate value storage unit 223 and the defective pixel stored in the defective pixel coordinate value storage unit 224. The coordinate value of the inspection image attention pixel G11 to be expressed is output, and the defect inspection operation for inspecting the presence or absence of the defect of the inspection object W in the inspection apparatus 100 is finished.

  In step s9, the image comparison unit 21 acquires the luminance value of the inspection image attention pixel G11 selected by the inspection image attention pixel selection unit 212. Next, in step s10 corresponding to the reference image attention pixel selection step, the reference image attention pixel selection unit 213 selects the inspection image selected by the inspection image attention pixel selection unit 212 as shown in FIG. A pixel having the same coordinate value as the target pixel G11 is selected as the reference image target pixel G21.

  Next, in step s11 corresponding to the surrounding pixel group extraction step, the surrounding pixel group extraction unit 214, as shown in FIG. 3B, out of each pixel of the reference image G2, the area around the reference image attention pixel G21. A peripheral pixel group G24 consisting of a plurality of pixels located within a predetermined range is extracted.

  Specifically, the peripheral pixel group extraction unit 214 extracts pixels up to a position shifted by N pixels from the reference image attention pixel G21 (coordinate values are (Xk, Yk)) as the peripheral pixel group G24. , A reference image in a rectangular area whose diagonal is a line segment connecting the first base pixel G22 having the coordinate values (Xk-N, Yk-N) and the second base pixel G23 having the coordinate values (Xk + N, Yk + N). Pixels other than the target pixel G21 are extracted as the peripheral pixel group G24. For example, when pixels up to a position shifted by two pixels with respect to the reference image target pixel G21 are extracted as the peripheral pixel group G24, the peripheral pixel group extraction unit 214 uses the coordinate values (Xk-2, Yk-2). A total of 24 pixels are extracted as a peripheral pixel group G24 in a rectangular area whose diagonal is a line segment connecting the first base pixel G22 and the second base pixel G23 having the coordinate value (Xk + 2, Yk + 2).

  Next, in step s12, the image comparison unit 21 acquires the luminance value of each pixel of the reference image attention pixel G21 and the peripheral pixel group G24.

  Next, in step s13 corresponding to the difference value calculation step, the difference value calculation unit 215 performs the inspection every time the inspection image attention pixel selection unit 212 selects the inspection image attention pixel G11 in the first order. The difference value of the luminance value of each pixel of the reference image attention pixel G21 and the peripheral pixel group G24 with respect to the luminance value of the image attention pixel G11 is calculated according to a predetermined second order. At this time, the difference value calculation unit 215 calculates a difference value with a positive / negative sign as the difference value.

  In step s14 corresponding to the determination step, the determination unit 216 determines whether or not the absolute value of the difference value is equal to or less than a predetermined threshold every time the difference value is calculated by the difference value calculation unit 215 according to the second order. judge. The determination operation by the determination unit 216 will be described with reference to FIG. In FIG. 4, FIG. 4 (a) is a graph showing the luminance value of each pixel constituting the inspection image G1, with the horizontal axis representing the X coordinate value and the vertical axis representing the luminance value, and is surrounded by a broken line. The area A1 to be displayed indicates a range of luminance values in which the absolute value of the difference value is equal to or less than a threshold value. FIG. 4B illustrates the reference image attention pixel G21 selected by the reference image attention pixel selection unit 213 and the peripheral pixel group extracted by the peripheral pixel group extraction unit 214 among the pixels constituting the reference image G2. The luminance value of each pixel of G24 is shown as a graph with the horizontal axis representing the X coordinate value and the vertical axis representing the luminance value, and the area A1 surrounded by the broken line is a luminance value whose absolute value of the difference value is equal to or less than the threshold value. Indicates the range.

  In FIG. 4B, the difference value calculation unit 215 sequentially selects one pixel in the positive direction of the X coordinate from the pixel having the smallest X coordinate value among the pixels of the reference image attention pixel G21 and the peripheral pixel group G24. A pixel is selected for each pixel, and a difference value between the selected pixel and the inspection image attention pixel G11 is calculated. Therefore, the determination unit 216 determines whether or not the inspection image attention pixel G11 is a normal pixel using the difference values calculated in the above order by the difference value calculation unit 215. In FIG. 4B, one pixel of the peripheral pixel group G24 having the smallest X coordinate value selected first by the difference value calculation unit 215 from among the pixels of the reference image target pixel G21 and the peripheral pixel group G24. When the difference value calculation unit 215 calculates the difference value from the inspection image attention pixel G11, the determination unit 216 determines that the absolute value of the difference value is equal to or less than the threshold, and at that time, the inspection image attention pixel G11. Are normal pixels.

  If the determination unit 216 determines in step s14 that the absolute value of the difference value is equal to or less than the threshold value, the process proceeds to step s15. If the determination unit 216 determines that the absolute value of the difference value is not equal to or less than the threshold value, the process proceeds to step s17.

  In step s15, the determination unit 216 determines that the inspection image attention pixel G11 in which the absolute value of the difference value is determined to be equal to or less than the threshold value in step s14 is a normal pixel.

  Next, in step s16 corresponding to the calculation operation control step, the calculation operation control unit 217 determines one inspection image when the determination unit 216 determines that the inspection image attention pixel G11 is a normal pixel in step s16. The difference value calculation operation of the difference value calculation unit 215 according to the second order for the image pixel of interest G11 is terminated, and the process returns to step s6. In the example of FIG. 4B, the difference value calculation unit 215 controlled by the calculation operation control unit 217 includes one pixel of the peripheral pixel group G24 having the smallest X coordinate value selected first, and the inspection image attention pixel. After the difference value with G11 is calculated, the difference value calculation operation is not performed. As described above, the difference value calculation unit 215 controlled by the calculation operation control unit 217 does not calculate the difference values for all the pixels of the reference image attention pixel G21 and the peripheral pixel group G24, but determines the determination unit 216. When it is determined that the inspection image attention pixel G11 is a normal pixel, the difference value calculation operation for one inspection image attention pixel G11 is completed. Therefore, the defect inspection for inspecting the presence or absence of a defect in the inspection object W It is possible to prevent the processing time from becoming too long.

  In step s14, after the determination unit 216 determines that the absolute value of the difference value is not less than or equal to the threshold value, that is, the difference value calculation unit 215 calculates the first difference value having an absolute value greater than the threshold value. In subsequent step s17, the determination unit 216 determines again whether the second difference value calculated by the difference value calculation unit 215 in step s13 is different in sign from the first difference value. The determination operation by the determination unit 216 will be described with reference to FIG. In FIG. 5, FIG. 5 (a) is a graph showing the luminance value of each pixel constituting the inspection image G1, with the horizontal axis representing the X coordinate value and the vertical axis representing the luminance value. The region A1 to be displayed indicates a range of luminance values in which the absolute value of the difference value is equal to or less than a threshold value. FIG. 5B shows the reference image target pixel G21 selected by the reference image target pixel selection unit 213 and the peripheral pixel group extracted by the peripheral pixel group extraction unit 214 among the pixels constituting the reference image G2. The luminance value of each pixel of G24 is shown as a graph with the horizontal axis representing the X coordinate value and the vertical axis representing the luminance value. The area A1 surrounded by the broken line is a luminance value whose difference value is less than or equal to the threshold value. Indicates the range.

  In FIG. 5B, the difference value calculation unit 215 sequentially selects one pixel in the positive direction of the X coordinate from the pixel with the smallest X coordinate value among the pixels of the reference image attention pixel G21 and the peripheral pixel group G24. A pixel is selected for each pixel, and a difference value between the selected pixel and the inspection image attention pixel G11 is calculated. Therefore, the determination unit 216 uses the difference values calculated in the above order by the difference value calculation unit 215 so that the second difference value calculated by the difference value calculation unit 215 is positive or negative with respect to the first difference value. It is determined whether the codes are different.

  If the determination unit 216 determines that the second difference value calculated by the difference value calculation unit 215 is different in sign from the first difference value, as shown in FIG. A pixel located in the vicinity of the inspection image attention pixel G11 in G1 is an edge candidate pixel whose luminance value changes abruptly. The edge candidate pixel is a pixel of the inspection image G1 corresponding to the circuit pattern formed on the inspection object W or the edge portion of the edge of the inspection object W.

  When the determination unit 216 determines that the second difference value is different in sign from the first difference value, the determination unit 216 proceeds to the above-described step s15, and the determination unit 216 determines the normal pixel for the inspection image attention pixel G11. It is determined that If the determination unit 216 determines that the second difference value is not different in sign from the first difference value, the process proceeds to step s18. In step s18, the image comparison unit 21 determines whether the determination operation by the determination unit 216 has ended. If the image comparison unit 21 determines that the determination operation by the determination unit 216 has ended, the process proceeds to step s19. If the image comparison unit 21 determines that the determination operation by the determination unit 216 has not ended, the process proceeds to step s13 described above.

  In step s19, it is determined that the absolute value of the difference value is not equal to or less than the threshold value in step s14, and in step s19 after it is determined in step s17 that the second difference value is not different in sign from the first difference value. The unit 216 determines that the inspection image attention pixel G11 is a defective pixel. Next, in step s20, the calculation operation control unit 217 ends the difference value calculation operation of the difference value calculation unit 215 for one inspection image attention pixel G11, and returns to step s6.

  As illustrated in FIG. 5, when a pixel located in the vicinity of the inspection image attention pixel G11 in the inspection image G1 is an edge candidate pixel whose luminance value changes abruptly, the determination unit 216 performs the second difference value. When the difference between the first difference value and the positive / negative sign is determined to be different, the difference value calculation operation of the difference value calculation unit 215 with respect to one inspection image target pixel G11 is terminated, whereby the defect of the inspected object W is detected. It can be suppressed that the processing time of the defect inspection for inspecting the presence or absence of the defect becomes too long.

  The inspection program that causes the image comparison unit 21 and the storage unit 22 in the image processing apparatus 2 of the inspection apparatus 100 to function is a program that causes the computer including the image comparison unit 21 and the storage unit 22 to function as the inspection apparatus 100. This inspection program can be recorded on a conventionally known computer-readable recording medium.

  By recording the inspection program on a recording medium, a recording medium on which program codes (execution format program, intermediate code program, source program, etc.) for executing defect inspection processing based on the inspection program are recorded is provided in a portable manner. be able to.

  The recording medium may be a memory for the microcomputer to perform processing, for example, a program medium such as a ROM (Read Only Memory), or may be inserted into a program reading device provided as an external storage device in the computer. It may be a program medium that can be read.

  The inspection program stored in the recording medium may be a method in which the microprocessor accesses the recording medium and executes it, or the microprocessor reads out the program code from the recording medium, and the read program code is The inspection program may be executed by being downloaded to the program storage area of the microcomputer. It is assumed that this download program is stored in the main device in advance.

  Here, the program medium is a recording medium configured to be separable from the main body, and includes a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a flexible disk and a hard disk, a CD-ROM (Compact Disc-Read Only Memory). ), Optical disc systems such as MO (Magneto Optical disc), MD (Mini Disc), DVD (Digital Versatile Disc), IC (Integrated Circuit) cards (including memory cards), card systems such as optical cards, or mask ROM, It may be a medium that carries a fixed inspection program including a semiconductor memory such as an EEPROM (Erasable Programmable Read Only Memory), an EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), or a flash ROM.

  In addition, if the computer has a system configuration capable of connecting to a communication network including the Internet, the recording medium may be a medium that dynamically carries the program code so as to download the program code from the communication network. When the inspection program is downloaded from the communication network in this way, the download program is stored in the main device in advance or installed from another recording medium. In addition, the inspection program can be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  In the above, the inspection apparatus 100 has been described as an apparatus for inspecting the presence / absence of a defect in the inspection object W, but the present invention is not limited to this application. The technique according to the inspection apparatus 100 of the present invention can be applied to suppress the influence of noise caused by rain in an application of image comparison when a rainy day landscape is taken with a stereo camera. In addition, the inspection apparatus 100 of the present invention can accurately perform image comparison even when image displacement or distortion occurs due to the influence of movement or rotation, so this technique is installed in a robot. It is also conceivable to apply the present invention to an image recognition device, an image recognition device as a component of an autopilot device mounted on an automobile, and the like.

DESCRIPTION OF SYMBOLS 1 Imaging part 2 Image processing apparatus 3 Output device 4 Carrying part 21 Image comparison part 22 Storage part 100 Inspection apparatus 211 Inspection image correction part 212 Inspection image attention pixel selection part 213 Reference image attention pixel selection part 214 Peripheral pixel group extraction part 215 Difference value calculation unit 216 Determination unit 217 Calculation operation control unit 221 Reference image storage unit 222 Threshold storage unit 223 Normal pixel coordinate storage unit 224 Defective pixel coordinate storage unit

Claims (5)

An inspection device for inspecting the presence or absence of a defect in an inspection object,
A reference image storage unit that stores in advance a reference image representing a state in which there is no defect in the inspection object, which is a reference for inspecting the presence or absence of the defect in the inspection object;
An imaging unit that images the object to be inspected and obtains an image for inspection;
An inspection image attention pixel selection unit that selects one inspection image attention pixel from a pixel constituting the inspection image in accordance with a predetermined first order;
A reference image attention pixel selection unit that selects a reference image attention pixel corresponding to the inspection image attention pixel from pixels constituting the reference image;
A peripheral pixel group extraction unit that extracts a peripheral pixel group composed of pixels located within a predetermined range around the reference image target pixel among the pixels constituting the reference image;
A difference value calculation unit that calculates a difference value between luminance values of the reference image target pixel and the peripheral pixel group with respect to a luminance value of the inspection image target pixel according to a predetermined second order;
A determination unit that determines whether or not an absolute value of the difference value is equal to or less than a predetermined threshold every time the difference value is calculated according to the second order by the difference value calculation unit;
A calculation operation control unit that controls a difference value calculation operation of the difference value calculation unit, and when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value, An inspection apparatus comprising: a calculation operation control unit that terminates the difference value calculation operation of the difference value calculation unit according to the second order. The difference value calculation unit is configured to calculate a difference value with a positive / negative sign as the difference value,
The determination unit calculates a second difference value having a positive / negative sign different from the first difference value after the difference value calculation unit calculates a first difference value having an absolute value larger than the threshold value. 2. The inspection apparatus according to claim 1, wherein the inspection image target pixel is determined to be a normal pixel. An inspection method for inspecting the presence or absence of a defect in an object to be inspected, executed by the inspection apparatus according to claim 1,
A reference image storage step in which a reference image storage unit stores in advance a reference image representing a state in which there is no defect in the inspection object, which serves as a reference for inspecting the presence or absence of a defect in the inspection object;
An imaging step in which the imaging unit images the object to be inspected and obtains an image for inspection;
An inspection image attention pixel selection step in which an inspection image attention pixel selection unit selects one inspection image attention pixel from a pixel constituting the inspection image according to a predetermined first order;
A reference image attention pixel selection step in which a reference image attention pixel selection unit selects a reference image attention pixel corresponding to the inspection image attention pixel from pixels constituting the reference image;
A peripheral pixel group extracting unit that extracts a peripheral pixel group composed of pixels located within a predetermined range around the reference image attention pixel among the pixels constituting the reference image; and
The difference value calculation unit calculates a difference value between the luminance values of the reference image attention pixel and the peripheral pixel group with respect to the luminance value of the inspection image attention pixel according to a predetermined second order. Steps,
A determination step of determining whether or not the absolute value of the difference value is equal to or less than a predetermined threshold every time the difference value is calculated according to the second order by the difference value calculation unit;
The calculation operation control unit controls the difference value calculation operation of the difference value calculation unit, and when the determination unit determines that the absolute value of the difference value is equal to or less than the threshold value, And a calculation operation control step of ending the difference value calculation operation of the difference value calculation unit according to the second order for the inspection image attention pixel.   An inspection program for causing a computer to execute the inspection method according to claim 3.   The computer-readable recording medium which recorded the test | inspection program of Claim 4.

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