Calibration method and accuracy evaluation of visual target with double screen for straight pipe jacking machine

Aiming at the problem that it was difficult to calibrate the position and attitude relationship between the front and rear photosensitive imaging screens of visual target with dual-screen, a method for calibrating the position and attitude of the photosensitive imaging screen based on points-cloud was proposed. The front and rear photosensitive imaging screens were respectively divided into grid arrays of n rows and n columns. Combining the image 2D coordinates which were obtained in real time by industrial cameras and the spatial 3D coordinates which were measured by a total station to obtain the 2D-3D mapping relationship of each grid corner point on the photosensitive imaging screen, the coordinate point cloud data were acquired. Next, the 3D coordinates of the coordinate point cloud data are converted to the target coordinate frame according to the three common point coordinate frame transformation algorithm, which can determine the positional relationship between the camera and front/rear photosensitive imaging screen. And then the positional relationship between the front and rear photosensitive imaging screens was solved by the grid indexing method. In order to evaluate the accuracy of target attitude measurement, the static repeatability and the absolute measurement accuracy evaluation experiments were designed. The experimental results show that the static repeatability accuracy of the coordinates is 0.13 mm, the absolute accuracy of the coordinates is 0.93 mm, the static repeatability accuracy of the heading angle is 0.01°, and the absolute accuracy of the heading angle is 0.05°. Therefore, the calibration method can realize the accurate calibration of the pose of two spatial planes, which has the characteristics of simple operation and high precision, and can be used for calibration of visual target with double screen.