New interferometric algorithm for the measurement of phasing errors in spherical segmented-mirrors system

In segmented-mirror telescopes, wave-front discontinuities caused by segment misalignment are a major problem because they severely degrade optical performance. So for segmented-mirror system, it's necessary to exactly acquire position and gesture of each mirror. In this paper, Hough transform is used to obtain the edge of each segmented mirror, and then each separated segmented can be solely processed. And a new method to calculate tilt, tip and piston of spherical segmented mirror is given. This algorithm is based on the character of acclivitous spherical mirror which turns around any axis in different position and different angle, so it is useful to obtain each spherical segmented mirror's position and gesture. A mount which is allowed to do the segmented mirrors' tilt, tip and piston movement is designed. With the FISBA phase shifting interferometer the phase of whole system can be obtained, and in the method proposed in this paper tilt, tip and piston can be calculated to calibrate the spherical segmented-mirror system.