JPH04361104A - Detecting system of position of substrate mark - Google Patents

Abstract

PURPOSE:To increase the freedom of the shape and size of a substrate mark formed on a substrate and, in addition, to enable precise detection of the absolute central position thereof. CONSTITUTION:On a picked-up image 10 containing a point-symmetrically-shaped substrate mark formed on a substrate, a first point-symmetrically-shaped template 11 in which a part or the whole of the substrate mark M is included and a second template 12 obtained by rotating the first template through 180 deg. are prepared and they are registered. Thereafter the inputted image containing the substrate mark M is matched with each of the first and second templates, and the coordinates of the middle point (p) of the straight line connecting a first reference position (a) in the first template 11 and a second reference point (b) obtained by rotating the first position through 180 deg. are detected as the central position of the substrate mark M.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a board mark position detection method for accurately detecting the position of a mark formed on a board such as a printed circuit board set on a chip mounter.

0002

[Prior Art] In devices such as chip mounters,
Generally, a printed circuit board as a workpiece is mounted on an X-Y table, and chip components are mounted while controlling its position with high precision. It is necessary to accurately detect the position of a mark (referred to as a "substrate mark").

[0003] As a method for detecting the position of a board mark for this purpose, there is a method in which the board mark is imaged with a TV camera, an image scanner, etc., and the image data is binarized to measure the center of gravity of a binary image. Conventionally, a template matching method has been adopted in which pattern matching is performed between data and image data of a large number of registered figures (templates) to determine the amount of positional deviation relative to a reference position.

0004

[Problem to be Solved by the Invention] However, with the method of measuring the center of gravity position of a binary image, the image near the edge of the mark changes significantly depending on the illumination conditions and changes in the image, so accurate position detection is difficult. It was difficult.

Furthermore, in the conventional template matching method, the shape and size of the board mark are not only restricted to those registered in advance as a template, but also only the amount of positional deviation relative to the reference position is known. There it is,
It was not possible to detect (measure) the absolute center position of the board mark on the target board.

[0006] For this reason, it would be good if the reference board was set accurately at the reference position and a template was created from the board mark, but there is no guarantee that this would occur, so if the reference board is set at a different position, Even if the subsequent relative positional deviation amount of each board is detected and corrected, there is a problem in that the position cannot be corrected to the normal position.

[0007] The present invention has been made in view of the above points, and an object thereof is to increase the degree of freedom in the shape and size of a board mark, and to enable accurate detection (measurement) of its absolute center position. With the goal.

[0008]

[Means for Solving the Problems] In order to achieve the above object, a first board mark position detection method according to the present invention is as follows:
An image containing a point-symmetrical board mark formed on a board is captured, a first template with a point-symmetrical shape in which part or all of the board mark fits is created on the image, and one point in the first template is created. is set as a first reference position, a second template is created by rotating the first template by 180°, and a point at which the first reference position is rotated by 180° is set as a second reference position, Register each of these data.

[0009] After that, matching is performed between the input captured image including the board mark and the first template and the second template, and the first reference position and the second reference position are determined in a state where each matching is achieved. The coordinates of the midpoint of the straight line connecting the positions are detected as the center position of the board mark.

Further, the second board mark position detection method according to the present invention is such that when an image including a point-symmetric board mark formed on a board is captured, part or all of the board mark is detected on the image. A point-symmetrical window is set in advance, and one point in the window is registered as the first reference position. Then, an image including the board mark is captured and input, and the image in the window is set at 180 degrees. °Create a template by rotating it so that the first reference position is 1
The 80° rotated point is set as the second reference position, and after matching the above image with the template, the coordinates of the midpoint of the straight line connecting the first reference position and the second reference position are set as the board mark. Detected as the center position.

[0011]

[Operation] According to the present invention, the mark on the substrate and the template or window are made point-symmetrical, one point in the template or window is taken as the first reference position, and the image in the template or window is rotated 180°. Create a template by rotating it, set the point at which the first reference position is rotated by 180 degrees as the second position, match the input image with each of the templates, and set the first and second reference positions. By setting the midpoint as the center position of the board mark, the offset between the center of the template and the center of the board mark can be offset, and the center position of the board mark can be detected with high accuracy.

Furthermore, according to the second board mark position detection method, there is no need to create and register a template in advance, and the center of the board mark can be determined by determining only the window and the first reference position in advance. Can detect location. Therefore, the number of man-hours required by the operator is reduced, and the number of times template matching is performed is halved, resulting in faster processing.
It also requires less memory capacity. According to these methods, the shape and size of the board mark can be arbitrary as long as it is point symmetrical.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic configuration diagram of a substrate position control system implementing the substrate mark position detection method according to the present invention.

This system comprises an
a position control device 3 that controls the position of the substrate 1; and a position control device 3 that controls the position of the substrate 1;
It is composed of a V-camera 4, a display device 5 such as a CRT that displays an image captured by the camera on a display, and an image processing device 6 that processes the image data and detects the center position of the board mark M. .

Then, the image processing device 6 sends the center position detection data of the board mark to the position control device 3, and thereby the position control device 3 adjusts the deviation from the reference position so that the board mark M matches the reference position. The X-Y table 2 is controlled by correcting the control data by the amount. The board mark M is formed in a point-symmetric shape using copper foil, for example, at a reference position on the board 1, and solder is placed thereon so that the mark M is imaged with uniform brightness.

Next, a substrate mark position detection method according to a first embodiment of the present invention will be explained with reference to FIGS. 1, 2, and 4. A portion including a board mark M (a circular mark in this example) to be used as a reference for positioning on the board 1 set on the X-Y table 2 shown in FIG. 3 is imaged by the TV camera 4, and Image of board mark M indicated by a solid line (hereinafter, for convenience, this image will also be referred to as "board mark M")
A photographed image 10 of a predetermined area including the area is obtained. This image data is A/D converted and stored in an image memory within the image processing device 6, and is also displayed on the screen of the display device 5.

[0017] Therefore, the operator uses the keyboard or pointing device (
(mouse) etc., specify a point-symmetrical area (square in this example) where the board mark M will partially or completely (in this example, all) fit, as shown by the broken line in Figure 1, and An image is set as the first template 11, and it is registered in the memory, and one point a therein (in this example, the upper left corner point) is set as the first reference position.

Next, as shown in FIG. 2, the first template 11 is rotated by 180° about its center (
The image data is registered in the memory as the second template 12, and point b, which is the first reference position rotated by 180°, is set as the second reference position.

Then, the photographed image 10 of the board for which the position of the board mark M is to be detected is matched with the first and second templates 11 and 12 registered as described above. Since matching with the first template 11 has been achieved for the substrate for which a template was created in , it is only necessary to match it with the second template 12. From the next substrate, it is necessary to perform matching with the first template 11 and the second template 12, respectively.

[0020] As a method for performing matching, a conventional template matching method may be used. For example, the template is moved one pitch at a time in the X direction and the Y direction, and each time the photographed image of the area corresponding to the template is moved. The position with the highest degree of correlation may be determined as the matched position.

Alternatively, projection data in the X direction and Y direction are created for the template and the photographed image, and the correlation between the projection data in the X direction and the projection data in the Y direction is calculated. By determining the matching position based on the peak position of the correlation value, it becomes possible to significantly reduce the number of correlation calculations and perform matching in a short time.

When matching is achieved, the first template 11 is at the position shown by the broken line in FIG. 1 with respect to the photographed image 10, and the second template 12 is at the position shown by the dashed line. In this case, since the board mark M is point symmetrical, the first reference position a on the first template 11 and the second reference position b on the second template 12 with respect to its center position (point) p are In the positional relationship, the positive and negative signs are reversed and the distances are equal.

Therefore, the midpoint of the straight line (shown as a thin solid line in FIG. 1) connecting the first reference position a and the second reference position b, that is, the point p equidistant from points a and b, is the substrate mark. M
is the center position. The coordinate values (xp, yp) of the center position p of this board mark M are the coordinates (x1, yp) of the first reference position a.
, y1) and the coordinates (x2, y2) of the second reference position b, it can be easily determined as follows. xp=(x1+x2)/2 yp=(y1+y2
)/2

FIG. 4 is a flowchart of a process for detecting the position of a board mark by the image processing device 6 shown in FIG. This process sets the first template as described above (including determining the first reference position a),
Rotate it 180° and synthesize the second template (
(including the determination of the second reference position b), the photographed images are input, the first template and the second template are sequentially matched, and the first reference position a and the second reference position in the matching state are The coordinate value of the midpoint of the reference position b is calculated to detect the center position p of the board mark.

According to this method, the offset between the center of the template and the center of the board mark can be offset, and the center position of the board mark can be detected with high accuracy. The board mark can have any shape and size as long as it is point symmetrical.

Next, a substrate mark position detection method according to a second embodiment of the present invention will be explained with reference to FIGS. 5 and 6 and FIG. 3. In this embodiment, instead of registering two templates in advance as in the first embodiment, only the position and size of the window are set in advance, as shown in the flowchart of FIG.

That is, as shown by the solid line in FIG. 5, when an image including the board mark M is captured, a point-symmetrical window (in this example, a square) in which part or all of the board mark M is included is created on the image. The position and size of 13 are set, and one point (in this example, the upper left corner point) a is set as the first reference position.

After that, the photographed image including the board mark M from the TV camera 4 shown in FIG. 3 is input, and the window 13 is
The template 14 is synthesized by rotating the images within 180 degrees, and the point where the first reference position a is rotated by 180 degrees is set as the second reference position b. This template 14 is similar to the second template 1 shown in FIG.
This is the same as 2, but there is no need to register it in advance.

Next, the input image and the template 14 are matched, and in the matching state shown by the broken line in FIG. 5, the coordinates of the midpoint p of the straight line connecting the first reference position a and the second reference position b are obtained. The center position of the board mark M is detected by calculating the value.

According to this embodiment, there is no need to predetermine and register templates, which simplifies operator operations, and also eliminates the need for memory to store the image data of the two templates. , the capacity of the image memory is small, which saves memory resources. Furthermore, since matching between the template and the input image only needs to be done once, the detection process becomes faster.

Note that the shape of the board mark used in the present invention is not limited to a circle, but may be a point-symmetric shape, such as an ellipse, a square, a rectangle, a rhombus, a parallelogram, a regular hexagon, as shown in FIG. Various shapes, such as a cross, can optionally be used. Similarly, the template or window may have any shape as long as it is point symmetrical.

Furthermore, the first reference position a may be determined at any point within the first template 11 or window 13. For example, it may be any corner point, any point on the outer periphery, the center point, or any other arbitrary point. The second reference position b may be any point obtained by rotating the arbitrarily set first reference position a by 180 degrees with respect to the center point.

Further, matching accuracy will be better if all the board marks M on the photographed image 10 are included in the first template 11 or the window 13, but this is not essential to the present invention; It suffices if a part of M is included.

In FIG. 8, the board mark M is made into a modified diamond shape with four sides curved inward, and the window 13 and template 14 are
FIG. 9 shows an example in which the board mark M is made into a circle with a position and size that accommodates all of the board marks M, and FIG. 9 shows the window 13 and template 1.
This shows the relationship with 4. Note that in FIGS. 8 and 9, parts corresponding to those in FIG. 5 are given the same reference numerals.

In this example, one point on the circumference of the window 13 is defined as the first reference position a. And photographed image 1
0, rotate the image in this window 13 by 180 degrees as shown in FIG. 9, and synthesize the template 14.
A point at which the first reference position a is rotated by 180 degrees is defined as a second reference position b. After that, as shown in FIG. 8, if the template 14 and the photographed image 10 are matched, the midpoint P of the straight line connecting the first reference position a and the second reference position b will be the center position of the board mark M. becomes.

FIG. 10 shows an example in which the board mark M is square, and the window 13 and template 14 are circular in a position and size that partially accommodates the board mark M, and FIG. 11 shows the relationship between the window 13 and template 14. Show relationships. In addition, in FIGS. 10 and 11, the same reference numerals are given to the parts corresponding to those in FIG. 5, and the explanation thereof will be omitted.

In this example, the center point of the window 13 (the center of the circle) is taken as the first reference position a. In this case as well, as shown in FIG.
If matching is performed, the midpoint P of the straight line connecting the first reference position a and the second reference position b becomes the center position of the board mark M.

[0038] Also, the image data in the window 13 is
Instead of rotating the template 14 by 80 degrees and composing the template 14, for the normal image scanning (left → right, top → bottom) shown in FIG. 12 (A), the image shown in (B) is A similar template can also be obtained by reverse scanning (right to left, bottom to top).

Furthermore, by applying this invention, it is possible to make the board mark a shape that is not point symmetrical, for example, an equilateral triangle, and to make the first template or window similar in shape to the board mark. In this case, templates and reference positions are created by rotating the image (0°) and the reference position in the first template or window by 120° and 240°, respectively, and each template is matched with the photographed image. The point at the same distance from is the center position of the board mark.

[0040] In this way, the center position of the board mark can be detected with higher accuracy, but a large capacity image memory is required to store the image data of the template, and the number of times template matching is performed is also increased. Therefore, the processing time will be slightly longer.

[0041]

[Effects of the Invention] As explained above, according to the present invention, the absolute center position of the board mark can be detected with high precision, so the position of the set board in a chip mounter etc. can be adjusted with high precision. . Further, the board mark can have any shape and size as long as it is point symmetrical, so the degree of freedom is increased.

Furthermore, according to the second aspect of the invention, there is no need to predetermine and register templates, which simplifies operator operations and requires less image memory capacity. Furthermore, since matching between the template and the input image only needs to be done once, the detection process becomes faster.

[Brief explanation of drawings]

[Fig. 1] Photographed images according to the first embodiment of the present invention and the first,
FIG. 6 is an explanatory diagram of a matching state with a second template.

FIG. 2 is an explanatory diagram showing the relationship between the first template and the second template.

FIG. 3 is a schematic configuration diagram of a substrate position control system that implements the substrate mark position detection method according to the present invention.

4 is a flowchart of a process for detecting the center position of a board mark using the method of the first embodiment shown in FIG. 1 in the image processing device 6 of FIG. 3;

FIG. 5 is an explanatory diagram of a matching state between a window, a photographed image, and a template according to a second embodiment of the present invention.

6 is a flowchart of a process for detecting the center position of a board mark using the method of the second embodiment shown in FIG. 5 in the image processing device 6 of FIG. 3;

FIG. 7 is a diagram showing various examples of different shapes of a substrate mark and a first template or window when implementing the present invention.

FIG. 8 is a diagram similar to FIG. 5 showing an example in which the board mark is a modified rhombus with four sides curved inward, and the window and template are circular in a position and size that accommodates the board mark.

FIG. 9 is an explanatory diagram showing the relationship between the window and the template.

FIG. 10 is a diagram similar to FIG. 5 showing an example in which the board mark is square and the window and template are circular at a position and size that partially accommodates the board mark;

FIG. 11 is an explanatory diagram showing the relationship between the window and the template.

FIG. 12 is an explanatory diagram showing another method for creating a template from image data in a window in the second embodiment of the invention.

[Explanation of symbols]

1 board
2 X-Y table 3 Position control device
4 TV camera 5 Display device 6 Image processing device 10 Photographed image
11 First template 12 Second template 13 Window 14 Template
M Board mark a First reference position
b Second reference position p Center position of board mark

Claims (2)

[Claims] 1. An image including a point-symmetrical substrate mark formed on a substrate is captured, and a first template having a point-symmetrical shape in which part or all of the substrate mark is inserted is created on the image. , one point therein is set as a first reference position, the first template is rotated by 180 degrees to create a second template, and the first reference position is set to 180 degrees.
° The rotated point is set as the second reference position, these data are registered respectively, and then the matching between the input image including the board mark and the first template and the second template is performed, respectively. and detecting the coordinates of the midpoint of the straight line connecting the first reference position and the second reference position in a matched state as the center position of the board mark. method. 2. When an image including a point-symmetrical board mark formed on a board is captured, a point-symmetrical window is set in advance in which part or all of the board mark is included, and One point in the window is registered as the first reference position, and then an image including the board mark is captured and input, the image in the window is rotated 180 degrees to create a template, and the first point is A point at which the first reference position is rotated by 180 degrees is set as a second reference position, and after matching the image and the template, a point in the straight line connecting the first reference position and the second reference position is set as the second reference position. A board mark position detection method characterized in that the coordinates of a point are detected as the center position of the board mark.