Multiple Spatial Frequencies Pyramid WaveFront Sensing

A modification of the pyramid wavefront sensor is described. In this conceptually new class of devices the perturbations are split at the level of the focal plane depending upon their spatial frequencies and then, measured separately. The aim of this approach is to increase the accuracy in the determination of some range of spatial frequency perturbations, or a certain classes of modes, disentangling them from the noise associated to the Poissonian fluctuations of the light coming from the perturbations outside the range of interest or from the background in the pupil planes, the latter case specifically when the pyramid wavefront sensor is used with a large modulation. While the limits and the effectiveness of this approach should be further investigated, a number of variations on the concept are shown, including a generalization of the spatial filtering in the point-diffraction wavefront sensor. While the simplest application, a generalization to the Pyramid of the well known spatially filtering in wavefront sensing, is shown to promise a significant limiting magnitude advance, applications are further speculated in the area of eXtreme Adaptive Optics and when serving spectroscopic instrumentation where “light in the bucket” rather than Strehl performance is required.