An error separation method based on surface matching in large aspheric measurement

Surface matching technique is the base of three-dimension surface error separation, which plays an important role in error compensation of ultra-precision manufacturing and automatic feedback control system. Surface error and surface roughness are key indicators for the evaluation of the quality of optical elements ultra-precision manufacturing. There are variations between the measured data and the actual surface data due to clamped positioning errors. Therefore, it is difficult to improve the manufacturing precision by error compensation based on evaluating the deviation between the measured data and the theoretical surface data directly. So we proposed an error separation technique based on surface matching, which can match the surface generated by fitting the measured data with the theoretical surface. And then we can obtain the spatial transformation parameters between measured surface and the actual surface using genetic algorithm (GA) for optimising. Finally we can separate the spatial errors resulting from the clamped positioning errors of the measurement, and the actual measured surface errors are got.