JP2005038178A - Inspection apparatus for reference mark of inspection object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such a device that rapidly and surely detects the location of the center of gravity of a reference mark even when a contour part thereof is chipped or deformed. <P>SOLUTION: The device is provided with an imaging means 3 which photographs the surface of an inspection object having the reference mark 20b, a binarization means 6 which performs the binarization of an image of the reference mark 20b photographed by the imaging means 3, a storage means 16 which previously stores the areas of an inner ring area 22 and outer ring area 23 with respect to the reference mark 20b, and a maximum brightness detection means 14 which detects a location where the difference between the brightness of the inner ring area 22 and the brightness of the outer ring area 23 becomes maximum, and the device detects the location of the center of gravity of the reference mark 20b, based on the shape of an intermediary area in the detected location. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reference mark detection device that detects the position of the center of gravity of a reference mark provided on an inspection object such as a printed circuit board.

  In general, a printed board is provided with a reference mark on its surface. This reference mark is designed to detect whether or not the printed circuit board is accurately mounted on the stage of the printed circuit board inspection apparatus, and to detect the expansion / contraction state of the printed circuit board. It is. Specifically, for example, when detecting only one reference mark, only the position of the reference mark on the stage is detected, and when detecting two reference marks, the angle deviation of the printed circuit board is detected. To detect. Further, when detecting the positions of three or more reference marks, in addition to the positions and angular deviations of these marks, the expansion / contraction state of the base material generated during the formation of the printed circuit board is also detected. As a method for detecting the position of the center of gravity of the reference mark, there is one described in Patent Document 1 below.

The reference mark centroid position detection method described in Patent Document 1 uses what is generally called an area centroid method, and images a reference mark provided on a printed circuit board to form a reference mark. The sum of x coordinates of all pixels is obtained. Then, the center position of the x coordinate of the reference mark is obtained by dividing the sum of the x coordinates by the area of the reference mark, and similarly, the sum of the y coordinates is obtained and divided by the area of the reference mark. The position of the center of gravity of the y coordinate is obtained.
JP-A-5-211397

  By the way, such a fiducial mark may be chipped or deformed in the contour portion in the printed circuit board formation stage. However, in the conventional area centroid method or the like, the sum of the x coordinates and the sum of the y coordinates of the pixels constituting the reference mark is obtained to obtain the center of gravity. If it has occurred, the position of the center of gravity will be displaced. Furthermore, since the area centroid method calculates the sum of the x-coordinates and the sum of the y-coordinates of all the pixels of the reference mark, there is a problem that the calculation amount increases and the processing time becomes long. It was.

  Therefore, the present invention has been made paying attention to the above-described problem, and provides an apparatus capable of detecting the center of gravity position quickly and reliably even when the outline portion of the reference mark is missing or deformed. It is for the purpose.

  That is, in order to solve the above-described problems, the present invention provides an imaging unit that images the surface of an inspection object having a reference mark, and a binarization unit that binarizes an image of the reference mark captured by the imaging unit Storage means for storing an inner luminance detection region and an outer luminance detection region with respect to the reference mark in advance, and a position where the difference between the luminance of the inner luminance detection region and the outer luminance detection region is maximized. Position detection means, and configured to detect the position of the center of gravity of the reference mark based on the shape of the inner luminance detection region, the outer luminance detection region, or the intermediate region therebetween in the detected position.

  With this configuration, when detecting the reference mark, even if the outline portion of the reference mark is chipped or deformed, the center of gravity position is detected without recognizing the pixel of the chipped or deformed portion. As a result, the center of gravity is not displaced. Further, since pixel information of the entire reference mark is not used, the center of gravity position of the reference mark can be quickly detected with a small amount of calculation.

  As a preferred embodiment, the inner luminance detection region is shaped like a ring that exists inside the contour portion of the reference mark.

  According to this configuration, even if a through hole is provided inside the reference mark, the brightness of the mark area other than the through hole can be detected. Therefore, the inner ring area and the outer ring can be detected. It is possible to accurately detect the position of the center of gravity while ensuring a large luminance difference from the region. In addition, since the barycentric position is detected based on the pixel information of the ring-shaped region, it is possible to significantly reduce the amount of calculation compared to the case where the barycentric position is detected based on the pixel information of the entire reference mark.

  The present invention relates to an image pickup means for picking up an image of the surface of a printed circuit board having a reference mark, a binarization means for binarizing an image of the reference mark picked up by the image pickup means, and a luminance detection area inside the reference mark in advance. And a storage means for storing the outer brightness detection area, and a position detection means for detecting a position where the difference between the brightness of the inner brightness detection area and the brightness of the outer brightness detection area is maximized. The center of gravity of the reference mark is detected based on the shape of the inner luminance detection area, the outer luminance detection area, or the intermediate area in between, so that the outline portion of the reference mark is missing or deformed. Even in such a case, the center of gravity position can be detected quickly and reliably.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the printed circuit board inspection apparatus 1 in this embodiment captures an image of the reference mark 20b of the printed circuit board 2b with respect to the printed circuit board 2b provided with the reference mark 20b. To process. Then, with respect to the reference mark 20a of the regular printed circuit board 2a that has not been chipped or deformed in advance, as shown in FIG. 3, an inner ring region 22 having a smaller diameter than the contour portion 21, and a large diameter. The outer ring region 23 is set, and the number of pixels for each luminance of the inner ring region 22 and the outer ring region 23 at a predetermined position of the imaged printed board 2b is counted. Then, when the inner ring region 22 and the outer ring region 23 are sequentially moved spirally from this specific position and the movement within the predetermined range is completed, the difference in average brightness between the inner ring region 22 and the outer ring region 23 is Extract the maximum position. Then, based on the shape of the intermediate region 24 between the inner ring region 22 and the outer ring region 23 at the position where the difference in average luminance between the inner ring region 22 and the outer ring region 23 is maximized, the position of the center of gravity of the reference mark 20b. G is detected. Hereinafter, details of the present embodiment will be described.

  FIG. 1 is a block diagram showing a configuration of a printed circuit board inspection apparatus 1 according to the present embodiment.

  The imaging means 3 images the surface of a printed circuit board 2a (hereinafter referred to as “reference printed circuit board”) for generating reference data in advance for inspection or a printed circuit board 2b to be inspected. An image of the imaging area A that is input and set is obtained while viewing the display 8 by the input means 7 such as a mouse. In this embodiment, the imaging means 3 is configured to irradiate light from an oblique direction and receive the reflected light by a CCD camera or the like, as used in a general printed circuit board inspection apparatus. This CCD camera can also be constituted by a CMOS camera or a line sensor.

  The preprocessing unit 4 performs A / D conversion processing on the images of the printed circuit boards 2a and 2b captured by the CCD camera, and temporarily stores the converted data in the image memory 5. A binarizing means 6 is connected to the image memory 5.

  The binarizing means 6 counts the number of pixels for each luminance of the images of the printed circuit boards 2a and 2b stored in the image memory 5. In this binarization, first, as shown in FIG. 2B, a histogram is generated that shows the relationship between the luminance of the captured image and the number of pixels. When generating this histogram, as shown in FIG. 2A, in the captured image, the metal portions (light portions) that become the reference marks 20a and 20b and the base material portions 25a and 25b (dark portions) ), The normal distribution on the bright side and the normal distribution on the dark side exist continuously. For this reason, in this embodiment, the average value P0 is set as a threshold value for the portions P1 and P2 that are the respective peaks of these normal distributions, and an image captured using this threshold value P0 is a white image and a black image. Binarize into an image.

  As shown in FIG. 3A, the inner region setting means 9 sets an inner ring region 22 having a smaller diameter than the contour portion 21 of the regular reference mark 20a. In setting the inner ring region 22, first, binarization processing is performed on the regular reference mark 20a, and the region corresponding to the reference mark 20a in the binarized image is reduced. Further, the inner ring region 22 having a certain width is set by reducing the reduced region.

  Further, the outer region setting means 10 sets the outer ring region 23 having a larger diameter than the contour portion 21 of the regular reference mark 20a, similarly to the inner region setting means 9. In setting the outer ring area 23, first, binarization processing is performed on the regular reference mark 20a, and an area corresponding to the reference mark 20a in the binarized image is enlarged. Further, the outer ring region 23 having a certain width is set outside the intermediate region 24 by enlarging the enlarged region. Information regarding the inner ring region 22 and the outer ring region 23 set in this way is stored in the storage unit 16.

  The inspection area setting unit 11 sets an initial position O for searching for the reference marks 20a and 20b in the rectangular imaging area A set by the input unit 7 such as a mouse. Specifically, first, at the initial position O, the center position of the imaging area A set with the mouse is set as the origin O, and the brightness is set for each luminance in the inner ring area 22 and the outer ring area 23 centered on the origin O. Count the number of pixels. Then, sequentially, the inner ring region 22 and the outer ring region 23 are moved spirally as shown in FIG. 3B by a predetermined number of pixels from the origin, and the number of pixels for each luminance in the region is counted. The counting unit 12 counts the number of pixels for each luminance.

  The counting unit 12 counts the number of pixels for each luminance in the inner ring region 22 and the outer ring region 23 that are sequentially moved spirally by the inspection region setting unit 11. Then, the information on the number of pixels for each luminance is stored in the storage unit 16 together with the position information of the inner ring region 22 and the outer ring region 23 for which the count is performed.

  The average value calculating means 13 calculates the average brightness of the inner ring area 22 and the outer ring area 23 based on the number of pixels for each brightness counted by the counting means 12. Information on the average luminance is stored in the storage unit 16 together with the position information of the inner ring region 22 and the outer ring region 23.

  The maximum brightness detecting means 14 calculates the difference in average brightness between the inner ring area 22 and the outer ring area 23 stored in the storage means 16, and the brightness of all the inner ring areas 22 and the outer ring areas 23 is calculated. Of the differences, the maximum position is output.

  Based on the position detected by the maximum brightness detecting means 14, the center-of-gravity position detecting means 15 extracts an intermediate area 24 between the inner ring area 22 and the outer ring area 23 at that position. Usually, when the inner ring region 22 is completely included inside the reference marks 20a and 20b, the average brightness of the inner ring region 22 and the outer ring region 23 is the maximum value, and the inner ring region 22 and the outer ring region 23 are the maximum values. The contour portion 21 of the reference mark 20b exists in the intermediate region 24 between the two. Therefore, if the center of gravity position of the intermediate region 24 is detected, it becomes the center of gravity position G of the reference mark 20b.

  Next, the flow of detecting the center of gravity of the reference mark in the printed circuit board inspection apparatus 1 configured as described above will be described with reference to FIGS. In the description, first, a method for setting information relating to the inner ring region 22 and the outer ring region 23 based on the regular printed circuit board 2a serving as a reference will be described with reference to FIG. 4, and then the printed circuit board 2b to be inspected. A flow for detecting the gravity center position G of the reference mark 20b will be described with reference to the drawings.

<Flow of generating inner ring area and outer ring area>
First, the printed circuit board 2a having the reference mark 20a that is not chipped or deformed is set, and the surface of the reference printed circuit board 2a is irradiated with light to obtain an image provided on the surface (step T1). At this time, the imaging area A having the reference mark 20a is set while viewing the display 8 by the input means 7 such as a mouse, and an image of the area A is captured. The acquired image is A / D converted by the preprocessing means 4 (step T2), and the converted image information is written in the image memory 5. Then, the number of pixels for each luminance is counted, and a histogram as shown in FIG. 2B is generated (step T3). Next, an average value P0 is calculated from the peak values P1 and P2 of the generated histogram, and the captured image is binarized into a white image and a black image (step T4). Then, for the portion corresponding to the reference mark 20a in the binarized image, first, the preset reduction magnification is accumulated to set the outer peripheral portion of the inner ring region 22, and further from there A predetermined reduction ratio is integrated to set the inner periphery of the inner ring region 22 (step T5). Similarly, the preset enlargement magnification is integrated to set the inner peripheral portion of the outer ring region 23, and the enlargement magnification is further integrated therefrom to set the outer peripheral portion of the outer ring region 23. (Step T6). Then, information regarding the inner ring region 22 and the outer ring region 23 set in this way is stored in the storage means 16 (step T7). Thereafter, the reference printed circuit board 2a is removed, and the printed circuit board 2b to be inspected is checked. The center of gravity position G of the reference mark 20b can be detected.

<Inspection process of printed circuit board to be inspected>
Next, a method for detecting the gravity center position G of the reference mark 20b of the printed circuit board 2b to be inspected will be described. First, when detecting the gravity center position G of the reference mark 20b of the printed circuit board 2b to be inspected, similarly, the printed circuit board 2b is set in the printed circuit board inspection apparatus 1, and the surface of the printed circuit board 2b is irradiated with light. The surface image is taken (step T10). In this case as well, an image of the imaging area A having the reference mark 20b is taken while viewing the display 8 by the input means 7 such as a mouse. Then, the acquired image is A / D converted by the preprocessing means (step T11), and the information is written in the image memory 5. Next, based on the acquired image, the number of pixels for each luminance of the inner ring region 22 centered on the initially set position O is counted to calculate an average value, and the pixels for each luminance of the outer ring region 23 are calculated. The number is counted and the average value is calculated (step T12). Then, as shown in FIG. 3B, the inner ring region 22 and the outer ring region 23 are moved spirally by several pixels with reference to the initially set O position, and the number of pixels for each luminance at each position is determined. Similarly, the average value of luminance is calculated by counting (steps T12 to T13). When the calculation of the average brightness of all the inner ring areas 22 and the outer ring areas 23 in the imaging area A is completed, the average brightness of the inner ring area 22 and the average brightness of the outer ring area 23 at these positions are calculated. The position where the difference is maximum is detected (step T14). Then, assuming that the contour portion 21 of the actual reference mark 20b exists in the intermediate region 24 between the inner ring region 22 and the outer ring region 23 at this position, the gravity center position G of the intermediate region 24 is calculated. (Step T15).

  As described above, according to the embodiment, the inner ring region 22 and the outer ring region 23 with respect to the reference mark 20a are set in advance, and the surface of the printed board 2b having the reference mark 20b is imaged and binarized. Since the position where the average brightness of the inner ring region 22 and the outer ring region 23 is maximized is sequentially detected to detect the center of gravity position G of the reference mark 20b, the outline portion 21 of the reference mark 20b is missing or deformed. Even when such a situation occurs, the center-of-gravity position G can be obtained accurately. Further, since it is not necessary to acquire the information of all the pixels of the reference mark 20b and detect the center of gravity position as in the prior art, the center of gravity position G can be detected quickly with a small amount of calculation. .

  In this embodiment, the inner luminance detection area and the outer luminance detection area are ring-shaped, so that the luminance detection area is set on the entire inner side of the reference marks 20a and 20b. The amount of calculation can be significantly reduced. In addition, since the inner luminance detection area has a ring shape, even if a through hole or the like exists in the center portion of the reference mark 20b, the reference mark can be accurately obtained without considering the luminance of the portion. The barycentric position G of 20b can be detected.

  In addition, this invention is not limited to the said embodiment, It can implement in a various aspect.

  For example, in the above embodiment, a ring-shaped area is used as the inner luminance detection area. However, the present invention is not limited to this, and a luminance detection area having another shape may be set. In this case, for example, as shown in FIG. 6, only the outer luminance detection region 23 may be configured in a ring shape, and the inner luminance detection region 220 may be configured in a non-hollow circular shape.

  In the above-described embodiment, the reference marks 20a and 20b have been described using circular shapes. However, the shape of the reference marks 20a and 20b is not limited to this, and a rectangular shape 20c as shown in FIG. Similarly, in this case, the inner luminance detection region and the outer luminance detection region can have various shapes. For example, when the through hole 26 exists in the center portion of the rectangular reference mark 20c, The inner luminance detection region 221 may be configured as a circular ring, while the outer luminance detection region 230 may be configured as a rectangular ring corresponding to the contour shape of the reference mark 20c.

  Further, in the above embodiment, the surface of the reference mark 20a of the reference printed circuit board 2a is imaged, and the inner ring region 22 and the outer ring region 23 are set from now on. You may make it set these area | regions via an input means.

  In addition, in the above-described embodiment, the case where the center of gravity position of the reference mark 20b of the printed circuit board 2b is detected has been described. .

Functional block diagram of a printed circuit board inspection apparatus according to an embodiment of the present invention The figure which showed the histogram produced | generated by the counting means in the same form The figure which shows the relationship between the shape of the reference mark in the same form, and an inner ring area | region and an outer ring area | region Flowchart when setting the inner ring region and the outer ring region from the reference printed circuit board in the same form Flowchart for calculating the center of gravity position of the reference mark The figure which shows the shape of the reference mark in another embodiment, and the relationship between an inner ring area | region and an outer ring area | region The figure which shows the shape of the reference mark in another embodiment, and the relationship between an inner ring area | region and an outer ring area | region

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printed circuit board inspection apparatus 2a, 2b ... Printed circuit board (2a: Reference printed circuit board, 2b: Printed circuit board to be inspected)
DESCRIPTION OF SYMBOLS 3 ... Imaging part 4 ... Pre-processing part 5 ... Image memory 6 ... Binarization means 7 ... Input means 8 ... Display 9 ... Inner area | region setting means 10 ... Outer area setting means 11 ... inspection area setting means 12 ... counting means 13 ... average value calculation means 14 ... position detection means 15 ... maximum luminance position detection means 16 ... storage means P0 ..Threshold P1 ... first luminance P2 ... second luminance

Claims (2)

Imaging means for imaging the surface of the inspection object having a reference mark;
Binarization means for binarizing the image of the reference mark imaged by the imaging means;
Storage means for storing an inner luminance detection region and an outer luminance detection region with respect to the reference mark in advance;
A position detecting means for detecting a position where the difference between the brightness of the inner brightness detection area and the brightness of the outer brightness detection area is maximized;
The reference mark detection of the inspection object characterized in that the position of the center of gravity of the reference mark is detected based on the shape of the inner luminance detection region or the outer luminance detection region at the detected position or the intermediate region therebetween. apparatus. The reference mark detection device for an inspection object according to claim 1, wherein the inner luminance detection region is a ring-shaped region existing inside a contour portion of the reference mark.

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