Calibration of non-Common path aberration using multi-Channel phase diversity technique

This paper provides a method of using multi-channel Phase Diversity technique for online calibration of non-common path aberration of AO system. The PD technique estimate the phase aberration by collecting one or more frames images with short time of exposure at focal plane and out-of-focus plane, meanwhile reconstruct the target image. Under the working condition of closed-loop AO system, the static aberration of imaging path can be detected online by PD algorithm and transfer the wavefront aberration coefficient into the initial form of the deformable mirror, thus compensate for the static aberration of the non-common optical path. The experiment result shows that the imaging quality is improved by a large margin after calibration, the FWHM of the point source target decreased from 8.90 to 7.64; the wavefront RMS of imaging path decreased from 0.133 λ to 0.033 λ, and PV deceased from 0.79 λ to 0.17 λ, in accordance with the wavefront aberration measured by the closed-loop. This fully testified the ability of the application in optical detection of the Phase Diversity. There is no need to modify the original adaptive optical path, and it can precisely solve the system aberration in the condition of high SNR, and is one of the ideal optical detection techniques of large-diameter optical imaging system.