Electric method for testing co-phasing error of segmented mirrors

Implementation of optical co-phase among segmented mirrors in synthetical aperture optical system is the guarantee of its imaging with high resolution. In this paper, an electric testing method for co-phasing error among segmented mirrors was analyzed in the theory and proved in experiment. According to the principle of capacitance micrometer method, the co-phasing error between two adjacent segments was measured. With this method, the co-phasing error within 200 μm could be tested and the 5 nm co-phasing error could be resolved. An experimental system, to measure the co-phasing error with the electric method, was set up. In this system, some precise components, used to adjust the position of segmented mirror, were built up so that the implementation of the co-phasing could be realized. Using a phase-shift Fisba interferometer, the effects of the co-phase error testing and the piecing together of segmented mirror with the built experimental setup were verified experimentally. And the experimental results indicate that the use of capacitance micrometer method in testing the co-phase error is feasible. The testing method has wide measurement range and high sensitivity, but the complexity of the used optical system does not increase when compared with the optical testing method.