Abstract
Calibration is one of the most important technologies for line-structured light vision sensor. The existing calibration methods depend on special calibration equipments, whose accuracy determines the calibration accuracy. It is difficult to meet the requirements of universality and field calibration with those methods. In order to solve these problems, a new calibration method based on the combined target for line-structured light multi-vision sensor is proposed. Each line-structured light multi-vision sensor is locally calibrated by combined target with high precision. On the basis of global calibration principle and the characteristics of the combined target, global calibration and local calibration are unified. The unification avoids the precision decrement caused by coordinate transformation. And the occlusion problem of 3D reference objects can be avoided. An experimental system for 3D multi-vision measurement is set up with two sets of vision sensor and its calibration matrix is obtained. To improve the calibration accuracy, the method of acquiring calibration points with high precision and error factors in calibration are analyzed. After being calibrated, the experimental system is finally tested through a workpiece measurement experiment. The repeatability of this system is 0.04 mm, and it proves that the proposed calibration method can obtain high precision. Moreover, by changing the structure of the combined target, this calibration method can adapt to the different multi-vision sensors, while the accuracy of the combined target is still guaranteed. Thus, this calibration method has the advantages of universality and field calibration.
Highlights
Line-structured light vision sensor is non-contact and real-time sensor that has the advantages of high precision and active controllability
When the laser plane of a line-structured light vision sensor is projected onto a workpiece surface to be measured, the laser plane would produce distortion strip due to modulation caused by the size of the workpiece
Several calibration points on the laser plane are first collected with high precision
Summary
Line-structured light vision sensor is non-contact and real-time sensor that has the advantages of high precision and active controllability. Structure is in agreement with the vision sensor to be calibrated In this method, several calibration points on the laser plane are first collected with high precision. 2. Calibration method based on combined target The calibration process for line-structured light vision sensor includes calibration for camera intrinsic parameters and calibration for the position relationship between laser plane and camera. That is the mathematical model of the line-structured light vision sensor In this equation, the world coordinates (Xwi, Ywi) and their corresponding image coordinates (ui, vi) are known. The proposed calibration method for line-structured light multi-vision sensor based on combined target provides n calibration points both in three-dimensional world coordinates (Xwi, Ywi, Zwi) and two-dimensional image coordinates (ui, vi).
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