Machine-vision-based automatic levels compensation error verification

Algorithms for locating the center position of the crosshair image are studied, and a method based on machine vision to verify the compensation error of automatic levels is proposed. An illumination device is added behind the reticle of the automatic level. The reticle image is focused to infinity, imaged on the focal plane of the lens of the collimator, and images are captured using a CCD camera. Moreover, the necessary processing is performed to locate the center position of the crosshair image by the gray squared center of gravity method and the iterative weighted fitting method to obtain the subpixel level position coordinates. The metrological verification of the compensation error is completed after calibrating the angular grid values of the CCD in the x and y directions, the error angles of the x and y axes, and the parameters of the collimator coordinate system and attitude. The experimental results show that the machine vision-based method meets the requirements of the metrological verification of the compensation error of automatic levels, and the accuracy of the measurement results is higher than the traditional optical method.