JP4405009B2 - Calibration method of inspection machine with line sensor camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a calibration method for an inspection machine equipped with a line sensor camera.
[0002]
[Prior art]
When mounting electronic components on a printed circuit board, an inspection machine equipped with an imaging device is used to inspect the printed state after solder printing, the mounted state of the mounted component, and the component and solder state after the solder is cured. Has been.
Among them, an inspection machine of the type provided with an area camera can pick up a rectangular imaging region at a time since the CCD element of the area camera has n × n pixels. There are various methods for calibrating this type of inspection machine. For example, as shown in FIG. 5, the area camera 31 has a slightly smaller dimension than the imaging area 32 and has a dimensional accuracy guaranteed. The object 33 is imaged, the dimensions on the image are calculated by recognizing the captured image 34, and the camera scale, that is, the actual dimension per pixel, is calculated from the ratio between the calculated dimension and the actual dimension of the imaging object 32. Is calculated.
[0003]
On the other hand, an inspection machine equipped with a line sensor camera has a line sensor camera CCD element of m × 1 pixel (in the case of a color line sensor camera, n × 3 pixels: 3 pixels are red, green and blue elements, respectively. Therefore, it is necessary to move the line sensor camera or the imaging object in order to image the rectangular imaging area. In this type of inspection machine, calibration is performed in the same manner as described above.
[0004]
[Problems to be solved by the invention]
By the way, in each inspection machine as described above, there is a concern that the tilt of the camera affects the camera scale at the end of the imaging region 32, but in the case of an area camera, the imaging region 32 in the electronic component mounting process. Is about a few millimeters square, so the effect of camera tilt is negligible. However, in the case of a line sensor camera, since the size of the number of pixels m is often large, the difference between the camera scales of the first pixel and the m-th pixel cannot be ignored when the camera is mounted tilted. In this case, there is a problem in that it is necessary to adjust the tilt on mounting of the camera.
[0005]
The present invention solves the above problem, and an object of the present invention is to provide a calibration method that can easily adjust the inclination of a line sensor camera with respect to an imaging target.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention provides an installed calibration when calibrating an inspection machine including a line sensor camera that images a certain area by moving relative to an inspection object along a reading direction. The position of the central inspection point among arbitrary 3 inspection points determined at equal intervals on the surface of the inspection object is taught, and the 3 inspection points on the inspection object are imaged by a line sensor camera. The line sensor camera is relatively moved so that the central axis coincides with the corresponding central inspection point on the captured image, and the three inspection points on the inspection object are imaged by the moved line sensor camera, The distances D2 and D3 between the adjacent inspection points are obtained for the corresponding three inspection points, and the distance D2 / D3 is calculated from the ratio of both distances Calculating the inclination of the test object side of the emission sensor camera, and adjusts a line sensor camera or the image processing means based on the calculated angle theta.
[0008]
By doing so, the inclination of the line sensor camera toward the inspection object can be adjusted.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which an inspection object 2 for calibration is arranged below a line sensor camera 1 of an inspection machine.
The line sensor camera 1 is attached to the moving table 3 and provided along the Y-axis direction facing the inspection object 2, and is moved in the X-axis direction by a driving means (not shown) provided on the moving table 3. The rectangular imaging area 5 can be imaged by the linear imaging area 4 with a single scan in the X-axis direction. Here, the X-axis direction and the Y-axis direction are defined as directions orthogonal to each other in the plane in which the line sensor camera 1 moves as described above, and the Z-axis direction is defined as the direction from the line sensor camera 1 to the inspection object 2. To do.
[0010]
The moving table 3 is provided with an adjusting jig 6 for rotating the moving table 3 in the XY direction and an adjusting jig 7 for rotating in the YZ direction.
The inspection object 2 is a jig whose accuracy is ensured, and the inspection point a, the inspection point b, and the inspection point c are arranged on the substrate 8 at equal intervals so as to enter the rectangular imaging area 5. It can be moved in the Y-axis direction by a driving means (not shown).
[0011]
Hereinafter, the calibration method for the inspection machine will be described with reference to the flowchart of FIG.
First, the inclination of the line sensor camera 1 in the XY direction is calculated.
In the inspection object position teaching step # 1, as shown in FIG. 3A, the left front corner of the glass substrate 8 as viewed from the front of the inspection machine is set as the origin O (0, 0), and the inspection object 2 The position data of inspection point a, inspection point b, and inspection point c are taught. Further, a ′ teaches the center position of the inspection point a, and c ′ teaches position data of the center position of the inspection point c. Here, L is a straight line connecting the center position a ′ and the center position c ′ and is parallel to the Y axis.
[0012]
In the inspection object recognition step # 2, the inspection points a, b, c are imaged by moving the line sensor camera 1 in the X-axis direction, as shown in FIG. A captured image 9 including inspection points a1, b1, and c1 corresponding to c is obtained. Then, the center position a1 ′ of the inspection point a1 and the center position c1 ′ of the inspection point c1 on the captured image 9 are obtained using the camera scale of the design value.
[0013]
Next, in the camera scale calculation step # 3, the distance D0 between the center position a ′ of the inspection point a on the inspection object 2 and the center position c ′ of the inspection point c is obtained, and the inspection on the captured image 9 is performed. A distance D1 between the center position a1 ′ of the point a1 and the center position c1 ′ of the inspection point c1 is obtained, and a camera scale D1 / D0 represented by the ratio between the two is calculated.
[0014]
Next, in the angle calculation step # 4 of the XY plane, a straight line L ′ parallel to the Y-axis direction passing through the center position a1 ′ of the inspection point a1 on the captured image 9, and the center position a1 ′ of the inspection point a1 A straight line L1 connecting the center position c1 ′ of the inspection point c1 is obtained, and an angle θ formed by the straight line L ′ and the straight line L1 is obtained using L′ cos θ = L1.
Thereafter, in the XY adjustment step # 5, the moving table 3 is rotated in the XY direction by the adjustment jig 8 by an amount corresponding to the obtained angle θ, whereby the line sensor camera 1 is moved in the XY direction. Adjust the tilt.
[0015]
The above-described steps # 1 to # 5 are repeated until the accuracy in which the inclination of the line sensor camera 1 in the XY direction is required is satisfied.
Next, the inclination of the line sensor camera 1 in the YZ direction is calculated. Here, as shown in the upper part of FIG. 4A, the line sensor camera 1 is tilted in the YZ direction with respect to the inspection object 2 including the inspection points a, b, and c. .
[0016]
In the inspection object recognition process # 6, the inspection points a, b, c are imaged by moving the line sensor camera 1 in the X-axis direction, as shown in the lower part of FIG. A captured image including inspection points a2, b2, and c2 corresponding to b and c is obtained. Then, the center position b2 ′ of the inspection point b2 on the captured image is obtained here using a camera scale as a design value.
[0017]
Then, in the camera center alignment step # 7, the inspection object 2 is moved in the Y-axis direction so that the center position b2 ′ of the inspection point b2 and the center axis 10 of the line sensor camera 1 coincide on the captured image.
In the angle calculation step # 8 of the YZ plane, the inspection points a, b, and c are picked up again by the line sensor camera 1 moved to the position shown in the upper part of FIG. 4B, and shown in the lower part of FIG. Thus, a captured image including the inspection points a3, b3, and c3 corresponding to the inspection points a, b, and c is obtained.
[0018]
Then, a center position a3 ′ in the Y-axis direction of the inspection point a3, a center position b3 ′ in the Y-axis direction of the inspection point b3, and a center position c3 ′ in the Y-axis direction of the inspection point c3 are obtained, and the obtained center position a3 ′ The ratio between the distance D2 between the center position b3 ′ and the distance D3 between the center position b3 ′ and the center position c3 ′ is calculated, and the inclination of the line sensor camera 1 in the YZ direction is calculated based on the calculated value. Is calculated.
[0019]
Thereafter, in the YZ adjustment step # 9, the moving table 3 is rotated in the YZ direction by the adjustment jig 9 by an amount corresponding to the obtained angle θ, whereby the line sensor camera 1 is moved in the YZ direction. Adjust the tilt.
The above steps # 6 to # 9 are repeated until the accuracy required for the tilt of the line sensor camera 1 in the YZ direction is satisfied.
[0020]
As described above, in the inspection machine equipped with the line sensor camera 1, the inclination of the line sensor camera 1 with respect to the inspection object 2 can be adjusted, and the camera can be adjusted during the adjustment process using a mechanism unique to the line sensor camera 1. The scale can be calculated accurately.
In the above-described embodiment, an example of an inspection machine configured to move the line sensor camera 1 in the X-axis direction and move the inspection object 2 in the Y-axis direction has been described. However, the line sensor camera 1 is moved in the Y-axis direction. To move the inspection object 2 in the X axis direction, or to move the inspection object 2 in the X axis direction and the Y axis direction while the line sensor camera 1 is fixed, or the inspection object 2 Calibration can be similarly performed even with an inspection machine that is fixed and moves the line sensor camera 1 in the X-axis direction and the Y-axis direction.
[0021]
It is also possible to adjust the tilt in the XY direction after adjusting the tilt in the YZ direction of the line sensor camera 1.
Further, the inclination of the line sensor camera 1 can be adjusted by adjusting the image processing means instead of rotating the line sensor camera 1.
[0022]
【The invention's effect】
As described above, according to the present invention, the inclination between the line sensor camera and the inspection object is calculated by teaching the position of the inspection point determined on the surface of the inspection object for calibration and recognizing it by imaging. Can be adjusted. Further, the camera scale can be obtained in the step of calculating the inclination.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an inspection machine including a line sensor camera in which a calibration method according to an embodiment of the present invention is performed.
FIG. 2 is a flowchart illustrating the calibration method.
FIG. 3 is an explanatory diagram showing a method of calculating the tilt of the line sensor camera in the XY coordinate system in the calibration method.
FIG. 4 is an explanatory diagram showing a method of calculating the tilt of the line sensor camera in the YZ coordinate system in the calibration method.
FIG. 5 is an explanatory view showing a calibration method conventionally performed in an inspection machine of a type provided with an area camera.
[Explanation of symbols]
1 Line sensor camera 2 Inspection object 9 Captured image
10 Central axes a, b, c Inspection points
a1, b1, c1 inspection points
a2, b2, c2 inspection points
a3, b3, c3 inspection points

Claims (1)

When calibrating an inspection machine equipped with a line sensor camera that images a certain area by moving relative to the inspection object along the reading direction,
Teach the position of the central inspection point among any three inspection points set at equal intervals on the surface of the inspection object for calibration,
Three inspection points on the inspection object are imaged by a line sensor camera,
Move the line sensor camera relatively so that the center axis coincides with the corresponding center inspection point on the captured image,
The three inspection points on the inspection object are imaged by the line sensor camera after movement,
The distances D2 and D3 between adjacent inspection points are obtained for the corresponding three inspection points on the captured image, and the inclination of the line sensor camera toward the inspection object side is calculated from the ratio D2 / D3 of both distances.
A calibration method for an inspection machine having a line sensor camera, wherein the line sensor camera or the image processing means is adjusted based on the calculated angle θ.

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