Stitching Measurement Technique for Large-aperture Aspheric Surface during Grinding Process

Abstract

In order to test large-aperture aspheric surface optice element accurately during grinding process, a comprehensive optimization data processing model of stitching measurement is proposed based on coordinate measuring. Firstly, the stitching model for two segments of surface shape contour is built based on multi-body system theory and least square principle; secondly, the rejecting redundant data model is built based on curvature principle and least square fitting of aspheric equation; then the comprehensive optimization processing model for multiple segments stitching is built; three generatrices of a non-axisymmetry aspherical optical element whose aperture is 176 mm is stitching measured by Taylor Hobson profilometer and the data is processed by the model mentioned in the text. The results show that the maximum average error of the stitching measurement is 0.25 μm, and the minimum average error of the stitching measurement is –0.22 μm which is compared with the single measurement. The error is an order of magnitude higher than the surface shape peak–valley value 2.77 μm of the optic element, and matches the measurement requirements. The experimental results prove the correctness and effectiveness of the comprehensive optimization data processing model of stitching measurement, and the model can be applied in engineering.