Experimental Evaluation of Differential OTF (dOTF) Wavefront Sensing

Differential Optical Transfer Function (dOTF) is an image-based non-iterative technique for measuring the complex pupil field. The technique relies on the difference between two PSF images when a small modification is introduced near the pupil’s edge. The nature of the modification is of minor importance and can consist of a transmission blockage or a phase shift introduced by poking a single DM actuator. Even without calibration, dOTF yields an accurate estimate of the complex amplitude over the pupil plane. We experimentally evaluate the technique in several different optical systems, using both transmission and phase modifications to the pupil, and different modification areas and poke depths. The experiments include pupil blockages with bits of wire or a needle inserted just inside the pupil’s outer edge, with more sophisticated measurements possible using a continuous Boston Micromachines DM and a segmented IrisAO DM. The wavefront measurement accuracy is estimated, and the effect of poke depth and field modification convolution demonstrated. One test is designed to be very difficult for iterative techniques, by including a wildly offset and unknown pupil relative to the DM. This paper is the experimental companion to Codona’s dOTF theory paper [AS12-AS106-208].