Symmetrically weighted center of gravity for Shack-Hartmann wavefront sensing on a laser guide star
Abstract
Phase local gradient measurements in a Shack-Hartmann (SH) wavefront sensor (WFS) are achieved by tracking the displacements of a spot in each sub-aperture. This can be done by comparing the position of its center-ofgravity (COG) to a reference position. A commonly used method for position tracking is the weighted (W) COG in which the original image is multiplied by a weighting function, before centroiding. However, it can be shown that, if the spot centered on its COG is not even, the WCOG estimator is biased. We propose a new method for spot centroiding with a direct application to wavefront sensing on a LGS: the symmetrically weighted (SW) COG, in which the weighting function is taken as the symmetrical version of the spot, with respect to its COG.
- Publication:
-
Adaptive Optics Systems II
- Pub Date:
- July 2010
- DOI:
- 10.1117/12.856706
- Bibcode:
- 2010SPIE.7736E..56G