Errors Separation In Ultra-precision Measurement For Small Optical Elements

The optical components such as aspheric element are widely applied in modern optical systems, which brings up higher requirements for machining and testing. Precision of contact measurement is usually in the level of micron and sub-micron, which meet the accuracy requirements, and becomes the main testing means of optical component measurement. Based on small ultra-precision measuring system for optical elements developed by cooperation, errors separation in ultra-precision measurement was studied. The main content comprises:1. A data processing mathematical model is established. Multiform system errors of measuring system were analyzed, such as: linear trend error due to workpiece fixing sloped, rail error, posture errors caused by the inclination and eccentricity between measuring and workpiece coordinate system, were separated and compensated in-order.2. Algorithms of each error separation step were researched. Three radius compensation algorithms were analyzed and compared, as better performance and applicability, fitting method was chose for probe radius compensation. The removal algorithm of posture errors was studied, with the advantages of Quasi-Newton Algorithms and Conjugate Gradient Algorithms, the Levenberg-Marquardt Algorithm approximates more quickly and better. The removal algorithm of the positioning error was simulated, results show that the non-spherical components, the model can accurately calculate the posture error, and is immune from initial parameters, random error and noise.3. Used MATLAB7.0.1 as development environment, data processing mathematical model was realized. Procedures are effective in each part of system errors separation and compensation; finally obtain the surface roughness parameters and error curve. For spherical surface precision can reach about 0.15μm, for aspheric element, precision can reach 0.2μm.