JPH0812050B2 - Substrate mark position detection method - Google Patents

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 detecting system for accurately detecting the position of a mark formed on a board such as a printed board set on a chip mounter.

[0002]

2. Description of the Related Art In a device such as a chip mounter,
Generally, a printed circuit board as a work is mounted on an XY table, and chip parts are mounted while controlling the position with high accuracy. For that purpose, the reference position is formed on the substrate. It is necessary to accurately detect the position of the mark (referred to as "substrate mark").

As a board mark position detecting method therefor, a board mark is imaged by a TV camera, an image scanner or the like, and the barycentric position of a binary image obtained by binarizing the image data thereof is measured, or a board mark image. Conventionally, a template matching method or the like has been adopted in which pattern matching between data and image data of a large number of registered figures (templates) is performed to obtain the amount of relative displacement with respect to the reference position.

[0004]

However, in the method of measuring the position of the center of gravity of a binary image, the image in the vicinity of the edge of the mark changes remarkably depending on the condition of illumination and the change of the image. It was difficult.

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

Therefore, it suffices that the reference substrate is accurately set at the reference position and the template is created from the substrate mark, but this is not guaranteed, and if the reference substrate setting position is misaligned. However, even if the relative positional displacement amount of each substrate is detected and corrected thereafter, there is a problem in that it cannot be corrected to the regular position.

The present invention has been made in view of the above points, and it is possible to increase the degree of freedom in the shape and size of a substrate mark and to accurately detect (measure) the absolute center position of the substrate mark. With the goal.

[0008]

In order to achieve the above object, the first substrate mark position detecting method according to the present invention is
An image including a point-symmetrical substrate mark formed on the substrate is captured, a point-symmetrical first template in which a part or all of the substrate mark is included is created on the image, and one point in the template is created. As a first reference position, the first template is rotated by 180 ° to create a second template, and the point at which the first reference position is rotated by 180 ° is set as a second reference position, Register each of these data.

After that, the photographed image including the inputted board mark is matched with the first template and the second template, respectively, and the first reference position and the second reference position in the respective matched states are obtained. The coordinates of the midpoint of a straight line connecting the position and the position are detected as the center position of the board mark.

Further, according to the second substrate mark position detecting method of the present invention, when an image including a point-symmetrical substrate mark formed on a substrate is captured, a part or all of the substrate mark is displayed on the image. Is set in advance and one point is registered as the first reference position. After that, an image including the board mark is captured and input, and the image in the window is Create a template by rotating it and the first reference position is 1
The point rotated by 80 ° is set as the second reference position, the image and the template are matched, and then the coordinates of the midpoint of a straight line connecting the first reference position and the second reference position is set to the board mark. Detected as the center position of.

[0011]

According to the present invention, the mark on the substrate and the shape of the template or window are point-symmetrical, one point in the template or window is the first reference position, and the image in the template or window is 180 °. A template is created by rotating, and the point obtained by rotating the first reference position by 180 ° is set as the second position, and the input image and each template are matched to obtain the first and second reference positions. By setting the center point to the center position of the substrate mark, the offset between the center of the template and the center of the substrate mark can be canceled and the center position of the substrate mark can be detected with high accuracy.

Further, according to the second board mark position detecting method, it is not necessary to create and register the template in advance, and if only the window and the first reference position are predetermined, the center of the board mark is determined. The position can be detected. Therefore, the number of man-hours required for the operator is reduced, the number of times template matching is performed is halved, and processing becomes faster.
It requires less memory usage. According to these methods, as long as the substrate mark has a point-symmetrical shape, its shape and size are arbitrary.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 3 is a schematic configuration diagram of a substrate position control system that implements the substrate mark position detection system according to the present invention.

In this system, an XY table 2 on which a substrate 1 such as a printed circuit board for electronic equipment is placed, and an X-axis motor and a Y-axis motor (not shown) are driven to drive the substrate 1.
Position control device 3 for controlling the position of T, and T for imaging a predetermined area including the substrate mark M formed at the reference position of the substrate 1.
The V camera 4, a display device 5 such as a CRT that displays an image captured by the V camera 4, and an image processing device 6 that processes the image data and detects the center position of the substrate mark M are configured. .

Then, the image processing device 6 sends the center position detection data of the substrate mark to the position control device 3, whereby the position control device 3 shifts the substrate mark M from the reference position so that the substrate mark M coincides with the reference position. The XY table 2 is controlled by correcting the control data by the amount. The board mark M is formed at a reference position of the board 1 by, for example, a copper foil in a point symmetrical shape, and solder is placed on the board mark M so that an image can be picked up with uniform brightness.

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

Therefore, the operator operates a keyboard or pointing device connected to the image processing apparatus.
Using a (mouse) or the like, specify an area of a point-symmetrical shape (square in this example) in which part or all (all in this example) of the board mark M is shown as shown by the broken line in FIG. 1, and within that area Image is set as the first template 11, which is registered in the memory, and one point (point in the upper left corner in this example) a therein is set as the first reference position.

Next, as shown in FIG. 2, a process (composite) of rotating the first template 11 by 180 ° with respect to its center is performed, and the image data thereof is registered in the memory as the second template 12, and A point b, which is the reference position of No. 1 rotated by 180 °, is set as a second reference position.

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

As a method of matching, a conventionally used template matching method may be used. For example, the template is moved in the X direction and the Y direction by one pitch, and a photographed image of an area corresponding to the template is moved each time. The position with the highest degree of correlation may be taken 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 projection data in the X direction and the projection data in the Y direction are correlated with each other. If the matching position is obtained from the peak position of the correlation value, the number of times of correlation calculation can be significantly reduced, and matching can be achieved in a short time.

In the matched state, the first template 11 is in the position shown by the broken line in FIG. 1 and the second template 12 is in the position shown by the chain line in the photographed image 10. In this case, since the substrate mark M has a point-symmetrical shape, the first reference position a on the first template 11 and the second reference position b on the second template 12 with respect to the center position (point) p thereof. As for the positional relationship, the positive and negative signs are reversed and the distances are equal.

Therefore, the midpoint of the straight line connecting the first reference position a and the second reference position b (indicated by a thin solid line in FIG. 1), that is, the point p equidistant from the points a and b is the substrate mark. It is the center position of M. The coordinate value (xp, yp) of the center position p of the substrate mark M is the coordinate (xx) of the first reference position a.
1, y1) and the coordinates (x2, y2) of the second reference position b are simply obtained as follows. xp = (x1 + x2) / 2 yp = (y1 + y2) / 2

FIG. 4 is a flow chart of processing for detecting the substrate mark position by the image processing apparatus 6 shown in FIG. This processing sets the first template as described above (including determination of the first reference position a), rotates it by 180 °, and combines the second template (determination of the second reference position b). After that, the photographed image is input to sequentially match the first template and the second template, and the coordinates of the midpoint of the first reference position a and the second reference position b in the matching state. The value is calculated to detect the center position p of the substrate mark.

According to this method, the offset between the center of the template and the center of the substrate mark can be canceled out, and the center position of the substrate mark can be detected accurately. The substrate mark may have any shape and size as long as it has a point-symmetrical shape.

Next, a substrate mark position detecting method according to a second embodiment of the present invention will be described with reference to FIGS. 5, 6 and 3. In this embodiment, as shown in the flow chart of FIG. 6, only the position and size of the window are set in advance without registering two templates in advance as in the first embodiment.

That is, as shown by the solid line in FIG. 5, when an image including the substrate mark M is picked up, a window having a point-symmetrical shape (square in this example) in which part or all of the substrate mark M is included in the image. The position and size of 13 are set, and one point (point in the upper left corner in this example) 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.
The image inside is rotated 180 ° to synthesize the template 14, and the point obtained by rotating the first reference position a by 180 ° is set as the second reference position b. This template 14 is the second template 1 shown in FIG. 2 in the above-mentioned embodiment.
Although it is the same as that of 2, it is not necessary to register 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. The value is calculated and the center position of the substrate mark M is detected.

According to this embodiment, since it is not necessary to determine and register templates in advance, the operation of the operator is simplified, and the memory for storing the image data of the two templates is also unnecessary. , The image memory capacity is small and the memory resources are saved. Furthermore, since the number of times the template and the input image are matched is only one, the detection process becomes faster.

The shape of the substrate mark used in the present invention is not limited to a circular shape and may be any point-symmetrical shape. Therefore, for example, an ellipse, a square, a rectangle, a rhombus, a parallelogram, a regular hexagon, etc. as shown in FIG. Various shapes such as a cross shape can be arbitrarily used. Similarly, the shape of the template or window may be any shape as long as it is a point-symmetrical shape.

Further, the first reference position a may be determined at any point in the first template 11 or the window 13. For example, it may be any corner point, any point on the outer peripheral line, the center point, or any other point. The second reference position b may be a point obtained by rotating the arbitrarily set first reference position a by 180 ° with respect to the center point.

Further, the accuracy of matching is improved 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, and at least the board marks are not necessary. It suffices to allow a part of M to enter.

In FIG. 8, the substrate mark M is a modified rhombus with four sides curved inward, and the window 13 and the template 14 are formed.
FIG. 9 shows an example in which the substrate mark M is formed into a circle having a position and a size, and FIG.
The relationship with 4 is shown. 8 and 9, parts corresponding to those in FIG. 5 are designated by the same reference numerals.

In this example, one point on the circumference of the window 13 is set as the first reference position a. And photographed image 1
Input 0, rotate the image in this window 180 by 180 degrees as shown in FIG. 9, and synthesize the template 14,
A point obtained by rotating the first reference position a by 180 ° is referred to as a second reference position b. After that, if the template 14 and the captured image 10 are matched as shown in FIG. 8, the midpoint P of the straight line connecting the first reference position a and the second reference position b is also the center position of the substrate mark M. Becomes

FIG. 10 shows an example in which the substrate mark M has a square shape, and the window 13 and the template 14 have a circular shape having a position and a size in which the substrate mark M partially enters, and FIG. 11 shows the window 13 and the template 14. Show the relationship. 10 and 11, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In this example, the center (center of the circle) of the window 13 is the first reference position a. Also in this case, as shown in FIG. 10, the template 14 and the captured image 1
If it is matched with 0, the midpoint P of the straight line connecting the first reference position a and the second reference position b is also the substrate mark M.
It becomes the center position of.

In addition, the image data in the window 13 is set to 1
Instead of synthesizing the template 14 by rotating it by 80 °, it is shown in (B) for scanning of an image for normal matching (left → right, top → bottom) shown in FIG. 12 (A). A similar template can be obtained by performing reverse scanning (right → left, bottom → up).

Further, by applying the present invention, it is also possible to make the substrate mark a shape that is not point-symmetric, for example, an equilateral triangle, and make the shape of the first template or window similar to the substrate mark. In this case, the image (0 °) in the first template or window and the reference position are rotated by 120 ° and 240 ° respectively to create a template and a reference position, and each template is matched with the captured image. The point at the same distance from is the center position of the substrate mark.

By doing so, the center position of the substrate mark can be detected more accurately, but a large capacity of the image memory for storing the image data of the template is required, and the number of times of matching the template is large. Therefore, the processing time will be a little longer.

[0041]

As described above, according to the present invention, the absolute center position of the substrate mark can be detected with high precision, so that the position of the substrate set in the chip mounter or the like can be adjusted with high precision. . Further, the substrate mark may have any shape and size as long as it has a point-symmetrical shape, so that the degree of freedom is high.

Further, according to the second aspect of the invention, it is not necessary to determine and register the template in advance, so that the operator can easily operate and the image memory capacity can be reduced. Furthermore, since the number of times the template and the input image are matched is only one, the detection process becomes faster.

[Brief description of drawings]

FIG. 1 is a photographed image and a first image according to a first embodiment of the present invention.
It is explanatory drawing of the matching state with a 2nd template.

FIG. 2 is an explanatory view showing the relationship between the first template and the second template of the same.

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

4 is a flow chart of processing for detecting the center position of a substrate mark by the method of the first embodiment shown in FIG. 1 in the image processing apparatus 6 of FIG.

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

6 is a flow chart of processing for detecting the center position of the substrate mark by the method of the second embodiment shown in FIG. 5 in the image processing apparatus 6 of FIG.

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 view similar to FIG. 5, showing an example in which the substrate mark is formed into a modified rhombus in which four sides are curved inward, and the window and the template are formed into a circle having a position and a size in which all the substrate marks fit.

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

FIG. 10 is a view similar to FIG. 5, showing an example in which the substrate mark is square and the window and the template are circular with a position and size of a part of the substrate mark.

FIG. 11 is an explanatory view 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 present invention.

[Explanation of symbols]

1 substrate 2 XY table 3 position control device 4 TV camera 5 display device 6 image processing device 10 captured image 11 first template 12 second template 13 window 14 template M substrate mark a first reference position b second Reference position p Center position of PCB mark

Claims (2)

[Claims] 1. An image including a point-symmetrical substrate mark formed on a substrate is taken, and a point-symmetrical first template in which a part or all of the substrate mark is included is created on the image. , One point thereof is used as a first reference position, the first template is rotated by 180 ° to create a second template, and the first reference position is 180 °.
The rotated point is used as the second reference position, these data are registered respectively, and then the image including the board mark to be input is matched with the first template and the second template, respectively. A board mark position detecting method, wherein the coordinates of the midpoint of a straight line connecting the first reference position and the second reference position in a matched state are detected as the center position of the board mark. . 2. When a picture including a board mark having a point-symmetrical shape formed on a board is taken, a point-symmetrical window into which a part or all of the board mark is placed on the image is preset and One of the points is registered as a first reference position, and then an image including the board mark is captured and input, the image in the window is rotated 180 ° to create a template, and the template is generated. The reference position of 1 is 1
The point that is rotated by 80 ° is set as the second reference position, the image and the template are matched, and then the first reference position is set.
Board mark position detection method, wherein the coordinates of the midpoint of a straight line connecting the reference position and the second reference position are detected as the center position of the board mark.