Piston phasing in segmented telescopes

The next generation of optical telescope will provide a high-resolution imaging of celestial objects by using synthetic aperture. Measuring the piston error between the segments of the synthetic aperture becomes more and more important. We present a piston error detection method based on analyzing the intensity distribution of the image plane, which is adaptable to any segmented and deployable primary mirror telescope. The method's capture range is the coherence length of the light source used in the imaging system, and the accuracy is of nanoscale. Experiment has been carried out to validate the feasibility of this method.