Novel method of phasing segmented mirrors

A novel approach of co-phasing segmented mirrors using a Dispersed Rayleigh Interferometer (DRI) which is used for measuring the optical path difference between two parallel beams is proposed. Basic principle of DRI is introduced and configuration of co-phasing segmented primary mirrors for a Cassegrain telescope is presented. A fringe processing method called Two-Dimension Fringe analyzing (TDFA) is proposed to analyze Dispersed Rayleigh Interference Pattern (DRIP) automatically. A bread board including a co-phasing error generator and a DRI is established to demonstration the approach proposed. Preliminary results using the DRI established show that, measurement range reaches , repeatability is better than 2nm in whole range under condition of S/N=20 and can be accepted when S/N>8, and measurement error standard deviation in range is 5.8nm (S/N=20). All of the data imply that DRI is a wide-range and high-accuracy method for co-phasing of segmented mirror, and can be used in the orbit for its compact c onfiguration and no movement element.