ABSTRACT
Wavefront sensors, one of the three main components of a closed-loop adaptive optics system, are discussed in this chapter in detail. A short discussion of choosing the appropriate wavelength for sensing, dependent upon the application, is initially provided, and the chapter continues with details of detector technology such as figures-of-merit and noise sources. Detector technology for wavefront sensing includes solid-state devices such as photovoltaic or photoconductive sensors. To sense complicated wavefronts, these detectors can be incorporated into CCD or CMOS arrays. Position sensitive detectors and other thermal detectors are discussed as they apply to wavefront sensing and analysis. Using arrays requires the introduction of various algorithms for sensing the position of the light detected on the array. Algorithms for centroiding, thresholding, spatial filtering, and windowing are discussed in detail, while introducing correlation-based algorithms, such as the correlation tracker for extended sources. Besides direct detection, included in this chapter is a discussion of phase diversity, deconvolution, and machine learning as it applies to adaptive optics wavefront sensing.
