Evaluation of phase-shifting techniques for a self-referencing interferometer wavefront sensor

Abstract

The Air Force Research Laboratory is developing a Self-Referencing Interferometer (SRI) wavefront sensor (WFS) for applications requiring laser propagation in strong scintillation. This paper compares several phase-shifting techniques that can be used to capture interference patterns and examines their effects on SRI WFS performance. These techniques include temporal, spatial, and spatial-temporal phase shifting. Temporal phase shifting allows for straightforward setup, alignment, and calibration, though its performance is degraded by changes in the atmosphere between measurements. Spatial phase shifting effectively freezes the atmosphere, but requires more rigorous camera calibration and alignment. Spatial-temporal phase shifting balances the benefits and challenges of both methods. This paper includes a discussion of the tradeoffs involved in selecting an appropriate phase-shifting approach for a given application. Laboratory results demonstrate the advantages and disadvantages of each technique in evaluation of SRI WFS performance.