Study On Measurement Of Aspheric Surface And Algorithm For Data Processing

Aimed at the drawbacks in current aspheric testing technologies, a novel method of measuring coordinates based on macromolecule micro-balls is presented. Some polystyrene micro-balls are adhered on the tested surface, then the aspheric camber is obtained through measuring the coordinates of micro-balls. In order to eliminate the limit of depth of field for measurement range, a beam of laser is focused on a micro-ball, then a quasi-spherical wave is formed by twice refraction on/in the micro-ball. So some circle interference fringes appear after the spherical wave interfering with a datum plane wave. The central position of the circle fringes is measured on a 2D scale plate so that to completely eliminate testing errors caused by linearity error of mechanical guide tracks. The measurement error caused by diameter error of micro-balls might be cut down if stand-substance micro-balls are used for measurement. To calculate and analysis image quality of optical system according to measured value, an algorithm for calculating optical axis of measured surface and coordinate system transform formula are given. To solve the problem that coordinates can not be inputted to optics design software, an algorithm of calculating aspheric parameters from coordinates is presented. An example shows that the aspheric equation can be multi-expressed for a given error, and the errors from the algorithm can be ignored because it is much smaller than the errors from measurement.To apply the novel method of aspheric measurement to the field of robot, a calibration method for micro manipulator system based on single mode optical fiber is developed. A spherical wave from the fiber fixed on the tested element interfered with a datum plane wave, then the images of the circle fringes are collected from two 2D scale plates which are fixed vertically. So 3D calibration for each coordinate system in sub-micron grade is realized in millimeter grade space.