Centroiding and Extraction of Tip/Tilt Information from Nonlinear Curvature Wavefront Sensor Measurements
Abstract
The nonlinear curvature wavefront sensor (nlCWFS) uses multiple (typically four) out-of-focus images to reconstruct the phase and amplitude of a propagating light beam. Because these images are located between the pupil and focal planes, they contain tip/tilt information. Rather than using a separate sensor to measure image locations, it would be beneficial to extract tip/tilt information directly and routinely as part of the reconstruction process. In the presence of atmospheric turbulence, recovering precise centroid offsets for each out-of-focus image becomes a dynamic process as image structure is altered by changing aberrations. We examine several tip/tilt extraction methods and compare their precision and accuracy using numerical simulations. We find that the nlCWFS outer measurement planes confer more accurate and reliable tip/tilt information than the inner measurement planes, due to their larger geometric lever arm. However, in practice, finite field of view (detector region of interest) effects bias tip/tilt retrieval when using the outer planes due to diffraction. Using knowledge of the -distance to each plane, we find that applying a best-fit linear model to multiple image centroid locations can offer fast and accurate tip/tilt mode retrieval. For the most demanding applications, a non-linear tip/tilt extraction method that self-consistently uses the speckle field may need to be developed.
Keywords
Cite
@article{arxiv.2407.14657,
title = {Centroiding and Extraction of Tip/Tilt Information from Nonlinear Curvature Wavefront Sensor Measurements},
author = {Caleb A. Abbott and Justin R. Crepp and Stanimir O. Letchev and Connor M. Smith},
journal= {arXiv preprint arXiv:2407.14657},
year = {2024}
}