Measurement of aspheric mirrors using arc-region scanning and data stitching technology

In order to meet the requirements of high efficiency and precision measurement in optical manufacturing, the arc-region scanning and data stitching technology (ASDST) is proposed for the measurement of aspheric mirrors. In the proposed method, the aspheric surface data can be obtained by scanning the arc-regions, through the rotary of the turntable and the lateral motion of a 2D laser displacement sensor. To improve the accuracy of measurement, the data stitching technology by principal component analysis (PCA) and iterative closest point (ICP) is applied to the optical measurement based on the point cloud data of the overlapping region. Based on the idea of sequential splicing, taking a piece of point cloud data as the benchmark, other point clouds are matched to the benchmark successively. Additionally, in order to reduce the hardware error, the pose error calibration of the 2D laser displacement sensor has been accomplished using standard blocks, standard balls, and software compensation. An experiment has been carried out using an off-axis aspheric mirror with 100-mm aperture to demonstrate the feasibility of the proposed arc-region scanning and data stitching technology. The proposed technology provides an efficient and convenient measurement method, which is also applicable for the on-machine measurement of various optical elements.