JP2001124700A - Calibration method of inspection machine with line sensor camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration method of adjusting easily the tilt of a line sensor camera of an inspection machine to an object the image of which is to be picked up. SOLUTION: The calibration method of inspection machine with line sensor camera comprises the steps of locating two arbitrary inspection points (a) and (c) onto the surface of an inspection object 2 for calibration, picking up the image of the inspection points (a) and (c) on the inspection object 2, and obtaining a distance D0 between the inspection points (a) and (c) and a distance D1 between two corresponding inspection points a1 and c1 on an picked up image 9 to determine a camera scale represented by a ratio D1/D0 of the two distance and, by using the ratio D1/D0, to determine the tilt to the direction on the read picture represented by an angle 0, the angle formed by a straight line L1 connecting the two inspection points a1 and c1 on the picked up image. Thus, the line sensor camera is rotated by the degree of the angle 0 obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating an inspection machine having a line sensor camera.

[0002]

2. Description of the Related Art In mounting electronic components on a printed circuit board, an image pickup device is provided for inspecting a printed state after solder printing, a mounted state of mounted parts, and a state of parts and solder after solder curing. Inspection machine is used. Among them, the inspection machine of the type equipped with an area camera can collectively image a rectangular imaging area because the CCD of the area camera has n × n pixels. There are various methods for calibrating this type of inspection machine.
As shown in (2), the area camera 31 captures an image of the calibration target 33 whose dimensions are slightly smaller than the imaging region 32 and whose dimensional accuracy is guaranteed. Is calculated, and the camera scale, that is, the actual size per pixel is calculated from the ratio between the calculated size and the actual size of the imaging target 32.

On the other hand, an inspection machine of the type equipped with a line sensor camera has a CCD element of the line sensor camera that has an m.
X 1 pixel (n x 3 for a color line sensor camera)
Pixel: Three pixels indicate red, green, and blue elements, respectively), so that it is necessary to move the line sensor camera or the imaging target in order to image a rectangular imaging area. In this type of inspection machine, calibration is performed in the same manner as described above.

[0004]

By the way, in each of the inspection machines as described above, there is a concern that the inclination of the camera may affect the camera scale at the end of the imaging area 32. Imaging area 32 in component mounting process
Is about several mm square, so that the influence of the camera tilt is within a negligible range. However, in the case of a line sensor camera, the size of the number of pixels m is often large, so if the camera is mounted at an angle, the difference in camera scale between the first pixel and the m-th pixel cannot be ignored. In this case, there is a problem that it is necessary to adjust the inclination at the time of mounting the camera.

An object of the present invention is to solve the above problem and to provide a calibration method capable of easily adjusting the inclination of a line sensor camera with respect to an object to be imaged.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an inspection machine provided with a line sensor camera for imaging a certain area by moving relative to an inspection object along a reading direction. At the time of calibration, the position of any two inspection points determined on the surface of the installed calibration inspection object is taught, and the two inspection points on the inspection object are imaged by a line sensor camera. The distance D0 between the two inspection points on the object and the distance D1 between the corresponding two inspection points on the captured image are obtained, and a camera scale represented by the ratio D1 / D0 of the two distances is calculated. The inclination of the line sensor camera in the reading direction, represented by the angle θ between the straight line connecting the points and the straight line Calculated using the serial ratio D1 / D0, and adjusts the line sensor camera or the image processing means based on the calculated angle theta.

By doing so, the inclination of the line sensor camera in the reading direction can be adjusted, and the camera scale can be obtained during the process. Further, the present invention also provides a method of calibrating an inspection machine equipped with a line sensor camera that captures an image of a certain area by relatively moving the object to be inspected along the reading direction. While teaching the position of the central inspection point among any three inspection points determined at equal intervals on the surface,
The three inspection points on the inspection object are imaged by a line sensor camera, and the line sensor camera is relatively moved so that the central axis coincides with the corresponding central inspection point on the captured image. The three inspection points on the inspection object are imaged, and distances D2 and D3 between adjacent inspection points are obtained for the corresponding three inspection points on the captured image, and the inspection object side of the line sensor camera is obtained from a ratio D2 / D3 of both distances. Calculate the slope to
The line sensor camera or the image processing means is adjusted based on the calculated angle θ.

In this manner, the inclination of the line sensor camera toward the inspection object can be adjusted.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a state where 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 driving means (not shown) provided on the moving table 3. The rectangular imaging area 5 can be imaged by the linear imaging area 4 by one 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, and the Z-axis direction is defined as the direction from the line sensor camera 1 to the inspection object 2. I do.

The moving table 3 has the X
An adjustment jig 6 for rotating in the −Y direction and an adjustment jig 7 for rotating in the YZ direction are provided. The inspection object 2 is a jig with high accuracy, 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 is movable in the Y-axis direction by a driving means (not shown).

Hereinafter, a method of calibrating the above-described inspection machine will be described with reference to a flowchart of FIG. First, the XY tilt of the line sensor camera 1 is calculated. In the position teaching step # 1 of the inspection object,
As shown in FIG. 3A, the left front corner of the glass substrate 8 viewed from the front of the inspection machine is set as the origin O (0, 0), and the inspection point a, the inspection point b,
The position data of the inspection point c is taught. Further, a 'teaches the position data of 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 that connects the center position a ′ and the center position c ′, and indicates a straight line that is parallel to the Y axis.

In the inspection target object recognition step # 2, the inspection points a, b, and c are imaged by moving the line sensor camera 1 in the X-axis direction, and the inspection points a, b, and c as shown in FIG. , B, c, the captured image 9 including the inspection points a1, b1, c1 is obtained. And
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 determined using the camera scale of the design value.

Next, in a 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 determined, and the captured image 9 is obtained. The distance D1 between the center position a1 'of the upper inspection point a1 and the center position c1' of the inspection point c1 is obtained, and the camera scale D represented by the ratio between the two is obtained.
1 / D0 is calculated.

Next, in an angle calculation step # 4 of the XY plane, the center position a of the inspection point a1 on the captured image 9 is determined.
1 ′, a straight line L ′ parallel to the Y-axis direction, a center position a1 ′ of the inspection point a1 and a center position c of the inspection point c1
1 ′ is obtained, and an angle θ between 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 moved by the adjustment jig 8 in the XY direction by an amount corresponding to the obtained angle θ.
Direction, thereby adjusting the tilt of the line sensor camera 1 in the X-Y direction.

The above steps # 1 to # 5 are repeated until the inclination of the line sensor camera 1 in the XY directions satisfies the required accuracy. 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 center axis 10 of the line sensor camera 1 is inclined in the YZ direction with respect to the inspection target 2 including the inspection points a, b, and c. .

In the inspection object recognition step # 6, the inspection points a, b, and c are imaged by moving the line sensor camera 1 in the X-axis direction, and the inspection is performed as shown in the lower part of FIG. A captured image including inspection points a2, b2, and c2 corresponding to points a, b, and c is obtained. Then, the center position b of the inspection point b2 on the captured image
Here, 2 ′ is obtained using the camera scale of the design value.

Then, in the camera centering step # 7, the center position b of the inspection point b2 on the captured image
The inspection object 2 is moved in the Y-axis direction so that 2 ′ coincides with the central axis 10 of the line sensor camera 1. YZ
In the plane angle calculation step # 8, the inspection points a, b, and c are imaged again by the line sensor camera 1 moved to the position shown in the upper part of FIG. 4B, and as shown in the lower part of FIG. A captured image including the inspection points a3, b3, and c3 corresponding to the inspection points a, b, and c is obtained.

Then, the center position a3 'of the inspection point a3 in the Y-axis direction, the center position b3' of the inspection point b3 in the Y-axis direction, and the center position c3 'of the inspection point c3 in the Y-axis direction.
Is calculated, and the ratio of the calculated distance D2 between the center position a3 'and the center position b3' to the distance D3 between the center position b3 'and the center position c3' is calculated, and the line is calculated based on the calculated value. The inclination of the sensor camera 1 in the YZ direction is calculated.

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, thereby adjusting the inclination of the line sensor camera 1 in the YZ direction. the above#
Steps 6 to # 9 are repeated until the inclination of the line sensor camera 1 in the YZ direction satisfies the required accuracy.

As described above, in the inspection machine provided 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 adjustment process is performed by using a unique mechanism of the line sensor camera 1. The camera scale can be accurately calculated during. In the above-described embodiment, the line sensor camera 1
Is moved in the X-axis direction and the inspection object 2 is moved in the Y-axis direction by way of example, but the line sensor camera 1 is moved in the Y-axis direction and the inspection object 2 is moved in the X-axis direction. Or the line sensor camera 1 is fixed and the inspection object 2 is moved in the X-axis direction and the Y-axis direction, or the inspection object 2 is fixed and the line sensor camera 1 is moved in the X-axis direction and the Y-axis. Calibration can be performed in a similar manner even with an inspection machine having a configuration in which the inspection device is moved in both directions.

After adjusting the inclination of the line sensor camera 1 in the YZ directions, it is also possible to adjust the inclination in the XY directions. Further, the inclination of the line sensor camera 1 can be adjusted not by rotating the line sensor camera 1 but by adjusting the image processing means.

[0022]

As described above, according to the present invention, the position of the inspection point determined on the surface of the inspection object for calibration is taught and recognized by imaging.
The inclination between the line sensor camera and the inspection object can be calculated and adjusted. In addition, 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 on 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 a tilt of a line sensor camera in an XY coordinate system in the calibration method.

FIG. 4 is an explanatory diagram showing a method of calculating the inclination of the line sensor camera in the YZ coordinate system in the calibration method.

FIG. 5 is an explanatory diagram showing a calibration method conventionally performed in an inspection machine of a type having an area camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Line sensor camera 2 Inspection object 9 Captured image 10 Central axis a, b, c Inspection point a1, b1, c1 Inspection point a2, b2, c2 Inspection point a3, b3, c3 Inspection point

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Kajiyama 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Suehiro 1006 Kadoma Kadoma, Osaka Pref. Terms (reference) 2F065 AA03 AA37 AA56 CC25 EE00 EE11 FF04 FF61 JJ02 JJ25 MM24 QQ26 TT02 2G051 AA65 AB20 AC15 AC30 CA03 EA30

Claims (2)

[Claims] When calibrating an inspection machine equipped with a line sensor camera that captures an image of a certain area by moving relative to an inspection object along a reading direction, a calibration inspection object installed is calibrated. While teaching the position of any two inspection points determined on the surface, the two inspection points on the inspection object are imaged by a line sensor camera, and the distance D0 between the two inspection points on the inspection object and the captured image And a camera scale represented by the ratio D1 / D0 of the two distances is calculated, and the distance between the straight line connecting the two inspection points on the captured image and the straight line orthogonal to the reading direction is calculated. The inclination of the line sensor camera in the reading direction represented by the angle θ
A method for calibrating an inspection machine equipped with a line sensor camera, comprising: calculating a line sensor camera or an image processing means based on the calculated angle θ by using D0. 2. When calibrating an inspection machine equipped with a line sensor camera that images a certain area by moving relative to the inspection object along a reading direction, the calibration inspection object installed is calibrated. While teaching the position of the central inspection point among any three inspection points determined at equal intervals on the surface, the three inspection points on the inspection object are imaged by a line sensor camera, and the correspondence on the captured image is taken. The line sensor camera is relatively moved so that the central axis coincides with the center inspection point to be moved, and the line sensor camera after moving images three inspection points on the inspection object. The distances D2 and D3 between adjacent inspection points are obtained, and the ratio D2 /
D3 calculates the tilt of the line sensor camera toward the object to be inspected, and adjusts the line sensor camera or the image processing means based on the calculated angle θ. Method.