Dynamic interferometric wavefront sensor for strong turbulence conditions based on polarization imaging sensor

Adaptive Optics (AO) systems for the compensation of optical turbulence in the atmosphere have been proven to work well within certain boundaries. Under strong turbulence conditions, AO based on conventional gradient wavefront sensors such as the Shack-Hartmann combined with linear least-squares reconstructors have shown to perform poorly due to the occurrence of phase singularities, that inherently cannot be reconstructed by the least-squares method. Directwave-front sensors, measuring phase differences directly rather than the gradient, avoid this problem of reconstruction. The self-referencing point-diffraction interferometer, a concept for direct-wavefront sensing that relies on the principle of spatial filtering to generate a (theoretically) unaberrated reference wave from the incoming aberrated wavefront, was early identified as a strong contender for an advanced wavefront sensor in strong turbulence conditions. Several authors have presented such systems. They make use of either the Fourier-transform method or instantaneous phase-shifted interferograms imaged by a complex optical set-up on a single image sensor. This paper evaluates a dynamic self-referencing point-diffraction interferometer based on a pixelated polarization filter array imaging sensor for instantaneous spatial phase-shifting, promising a simpler optical set-up than other instantaneous phase-shifting approaches while retaining the advantage of less computational requirement compared with Fourier-transform methods.