Data processing for point-based in situ metrology of freeform optical surface

Freeform surfaces are widely used in advanced optical systems and the point-based metrology methods are often used for freeform surface measurement. In order to accurately process the measured data from point-based metrology system, the coordinate matching and surface fitting are essential. To ensure the matching efficiency and accuracy, we use a two-step coordinate matching method: pre-adjustment and accurate adjustment. We also develop an improved Newton iterative (INI) fitting algorithm to generate initial value and improve the fitting speed. The simulation and experiment verify the correctness and feasibility of the data processing.