Curvature Wavefront Sensing: Simple, Elegant, and Efficient

Curvature sensing is a very simple and elegant method to measure the Laplacian of the wavefront, based on the conservation of flux irradiance. Its implementation does not require any special optical components and as it is a direct measure of intensity in defocused images, photodiodes or other read-noiseless detectors can be used. Because it is a differential measurement, it is insensitive to biases and internal errors. Coupled with bimorph mirrors, it provides the most efficient type of adaptive optics and is perfectly suited to the spatial spectrum of atmospheric turbulence. Nonetheless there are some drawbacks to curvature wavefront sensing, most notably due to spatial aliasing and dynamic range.