ABSTRACT
The imagery obtained from ground or spaceborne optical telescopes systems depends upon the shape of the wavefront emerging from their exit pupils. There are both extrinsic and intrinsic factors influencing wavefront shape (such as medium and/or optical system induced aberration). An instrument which measures wavefront shape is called a wavefront sensor. Wavefront sensor measurements provide a single pass end-to-end diagnosis of an optical imaging system. The aberration content of the beam in the exit pupil is determined and expressed mathematically in terms of a polynomial. Such information provides a convenient means for calculating far-field behavior such as Strehl ratio, encircled energy, and modulation transfer function. A comparison can then be made between theoretical and empirical values of these parameters. This chapter provides information on various techniques employed by wavefront sensors, and how such sensors can be used in optical metrology.
