Research on Calibration Method of Line-Structured Light Based on Multiple Geometric Constraints

Abstract

Line-structured light calibration is an important step in the process of the visual measurement of structured light, and in the calibration process, the light plane equation is fitted by the camera coordinates of the data points on the light plane. There is error in solving the spatial coordinates of the data points, and the existing methods generally cannot effectively find the deviation points in the fitted data points, which leads to deviation when solving the parameters of the light plane equation. To correct the error caused by the deviation point in the calibration, this paper established a calibration method based on geometric constraints. In the method, the first constraint was that all fit points involved in the fitting had a certain consistency, and a part of the error points could be filtered by the distance from the data point to the light plane. In order to further improve the calibration accuracy, the laser was moved on a linear guide, the optimized objective function was established by the second geometric constraint, and the constraint was the relationship that the light plane at each position was parallel. In the experiment, a high-precision gauge block was used as the measured object, and the measurement results could be obtained. The calibration method can improve the calibration accuracy according to the experimental results.

A Method for Measuring Shaft Diameter Based on Light Stripe Image Enhancement

“…, the image coordinate system   In the visual system for measuring shaft diameter, the pixel values in the shaft-diameter image do not have a physical meaning, making it difficult to directly obtain dimensional information for the shaft parts. Therefore, the purpose of establishing a camera-based imaging system is to project the information points from the pixel plane into the real three-dimensional space [35,36], giving the image specific physical significance from which shaft-diameter information can be acquired. In this paper, to reduce errors caused by inaccurate calibration of the camera-based imaging system during the projection process, Zhang's two-step calibration method [18] is adopted.…”

Line structured light calibration method based on circular targets

“…Wang et al 8 used a checkerboard grid plane as a calibration target, and by changing the attitude of the robot and the calibration target, the uni-responsive matrix between the target plane and the image plane was obtained, and, finally, the 3D coordinates of the center point of the light bar were used to complete the fitting of the light plane. Li et al 9 designed a calibration target consisting of a checkerboard grid and a black plane. The laser is moved by a linear guide to obtain multiple parallel light plane equations, and finally an objective function is established to complete the optimization of the parameters of the light plane equations.…”