JPH0232203A - Height correcting method for two-dimensional image processing - Google Patents

Abstract

PURPOSE:To accurately measure the position and attitude of a work by correcting a measurement error which is caused by the difference in height between two reference points for measuring the position and attitude of the work with a position correcting value based upon the height of the work and height information on a camera which are found in advance. CONSTITUTION:The work 4 which differ in position height between the two reference points is lighted 2 and picked up by the camera 3 and the position and attitude (rotation angle) of the work 4 are read in a visual sensor 17. The sensor position 11 of the camera 3 is found by using a jig which has a smaller hole in a lower sensor than in an upper sensor. Then the difference 6 at one measurement point which is generated when calibration by a jig 7 for calibration is performed with the height 10 (attitude) of one measurement point is corrected with the height 9 of the measurement point and data on the height 8 from a measurement table to the camera 3 which are found previously.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to position correction when measuring the position and orientation of a workpiece using a TV left camera visual device, and is applicable to industrial robots, etc. This is used for visual position correction.

(Prior art) As a prior art related to the present invention, the position and posture of the workpiece are
When measuring using the V left camera visual device, it is necessary to have two or more positions where the workpiece can be measured, and if the height (h) of the two points is the same, use the same jig as that height. By performing calibration, the position and posture (
(rotation angle) can be determined correctly, but if the heights (h) of the two locations are different, the error will vary depending on the height of the point on the workpiece being measured, as shown in FIG.

For this reason, by taking a sufficient height (h) from the measuring table to the camera relative to the height (h) of the workpiece, the error can be reduced. 4 is a workpiece, h is the height of two points on the workpiece, H is the height of the camera, and the camera 3a shown by the dotted line is raised to reduce errors.

(Problems to be Solved by the Invention) However, the method for measuring the workpiece described above requires (1) the height (H) from the measuring platform to the camera to be sufficiently larger than the height h of the workpiece; subject to location constraints.

(2) Since the position of the lighting device must be raised by raising the position of the camera, it is necessary to increase the illuminance of the lighting device.

(3) Since the height H from the measurement stand to the camera is high, the camera is likely to vibrate, reducing measurement accuracy.

There is a problem.

The present invention can be used to measure the height of a workpiece by raising the height of the camera (using a lens with a long focal length). The technical challenge is to develop a method that can accurately measure by correcting the height information from the viewing platform to the camera.

[Structure of the invention]

(Means for solving the problem) The technical means taken to solve the above technical problem are as follows. In other words, when measuring the position and orientation of a workpiece in two-dimensional image processing, the measurement error caused by the difference in the height of the two reference points for measuring the position and orientation is calculated using the height of the workpiece and the height of the camera. This is a method of correcting the position based on information.

(Function) By illuminating the workpiece, measuring the position and orientation of the workpiece with a visual sensor, and adding data such as the height of the workpiece to the data obtained from the position, the position based on the height of the workpiece can be determined. The error is corrected and the robot picks up the object according to the position data.In order to measure the position and orientation (rotation angle) of the object, at least two measurement points are required, and the heights of these two points are If they are the same, the robot coordinate system and the visual coordinate system are matched (calibrated) using the same jig to measure the height.

However, if the heights of the two points are different, there will be a difference between the visually measured position and the actual position. Therefore, here we will explain how to distinguish between the two measurement points to determine the position and orientation. Assuming that the height of the two points is different, the height of the measurement point is known in advance from the drawing to determine the positional error of the other measurement point that will occur when calibration is performed at the height of one measurement point (posture). This is corrected by providing height data from the measurement platform to the camera.

(Example) Examples will be described below.

FIG. 1 is a system diagram of this embodiment, where 1 is a robot, 2 is a lighting device, 3 is a camera, 4 is a workpiece, 15 is a workpiece mounting table, 17 is a visual device, and 18 is a robot controller.

Figure 2 shows the position of the workpiece 4 when viewed with the camera, and the deviation between the apparent position and the actual position. B) shows the workpiece is missing. 5 in (a) is the true position of the workpiece, 6 in (b) is the visually measured position of the workpiece, and 16 is the error between the true position of the workpiece and the visually measured position.

(A), (B), and (C) in Figure 4 show the positional relationship between the workpiece and the camera, 7 is the calibration jig, 8 is the height from the measurement table to the camera, and 9 is the measurement hole. IO is the height of the calibration jig 7, 1
1 is the center position of the camera.

Fig. 5 is a simplified representation of the measurement situation of the workpiece shown in Fig. 4. Since this shape is a similar triangle, as a similar triangle, A: B = △H: H, so, The height 8 of the camera, the height 9 of the measurement point, and the height 10 of the jig in FIG. 4 are known from the drawing data.

Therefore, as a way to find the center position of the camera, a jig 1 with a small hole in the upper part is closer to the center of the lower part as shown in Figure 6.
3 is placed on a measuring table as shown in FIG. 7, and placed in a position where the bottom part can be seen through the hole at the top, and the position is visually measured and taken as the center position 11 of the camera. So, by substituting the value into equation (1), we get:

Now, if we ask about the X coordinate, becomes.

Similarly, when calculating the Y coordinate, becomes.

Therefore, the apparent position (χ
, y) can be converted into the true position (X, Y) of the workpiece.

〔Effect of the invention〕

The present invention has the following effects.

■Reducing constraints on equipment installation without having to raise the camera position 2. No need to increase illuminance due to the height of the lighting device 3. Reduce measurement errors due to the height of the measurement position be able to.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the system of this embodiment, Fig. 2 is an explanatory diagram of workpiece misalignment, Fig. 3 is an explanatory diagram of the conventional example, and Fig. 4 (a), (b), and (c) are illustrations of the present embodiment. An explanatory diagram in the coordinate form of an example,
5 is an explanatory diagram of the main part of FIG. 4, FIG. 6 is an explanatory diagram of position adjustment, and FIG. 7 is an external perspective view of FIG. 6. 3...Camera. 4...Work. 8.9...Two reference heights.

Claims (1)

[Claims] In two-dimensional image processing, when measuring the position and orientation of a workpiece using a visual device, measurements occur due to differences in the heights of two reference points for measuring the position and orientation of the workpiece. A height correction method in two-dimensional image processing in which errors are corrected based on the height of a workpiece and height information of the camera.