ABSTRACT
Adaptive optics, described simply, but not totally accurately, as “a method of automatically keeping the light focused,” was first proposed in the 1950s. Limited by technology, it wasn’t until the 1970s when adaptive optics real-time, closed-loop systems first went from the laboratory into the field. This chapter is a discussion of physical optics, aberrations, and Fraunhofer and Fresnel diffraction, with concepts such as the Strehl ratio and the modulation transfer function defined and introduced. Wavefront representations in mathematical form, such as Zernike polynomials, are presented. The principle of interference, central to adaptive optics wavefront measurement, is introduced. Also introduced are general terms used in radiometry and specific terms used in adaptive optics, such as beam divergence, power-in-the-bucket, jitter, and brightness.
