Zonal wavefront sensing using a liquid crystal spatial light modulator

Zonal wavefront sensors of the Shack-Hartmann type have dynamic range and spatial resolution which are determined by the micro lens diameter and focal length. Increase in the spatial resolution requires reduction in the aperture size of each micro lens which effects the dynamic range. This paper presents a zonal wavefront sensing scheme based on an array of gratings that can provide programmable control over both the spatial resolution and the dynamic range. In the proposed scheme the outline of the photodetector array can be independent of the outline of the incident beam whose wavefront is to be measured. In this paper the scheme is implemented using a twisted nematic liquid crystal spatial light modulator.