Abstract

The standard autocorrelation method for computing the diffraction optical transfer function (OTF) of optical systems is based on the existence of a Fourier-transform relationship between the field in the exit pupil and the field in the observation plane. Since this relationship holds only in the small-angle approximation, a new autocorrelation method is developed that holds exactly within the Kirchhoff approximation. While the standard method involves the autocorrelation of the field in the exit pupil, the new method involves the autocorrelation of the Fourier transform of the field in the observation plane. The practical implementation of the new method is also discussed. It involves ray tracing to compute the amplitude and the wave front in the exit pupil and an efficient method for computing the autocorrelation integral.

© 1992 Optical Society of America