SCALAR AND ELECTROMAGNETIC DIFFRACTION POINT-SPREAD FUNCTIONS

We describe an accurate technique for computing the diffraction point- spread function for optical systems. The approach is based on the comb ined method of ray tracing and diffraction, which implies that the com putation is accomplished in a two-step procedure. First, ray tracing i s employed to compute the wave-front error in a reference plane on the image side of the system and to determine the shape of the vignetted pupil. Next the Rayleigh-Sommerfeld diffraction theory, combined with the Kirchhoff approximation and the Stamnes-Spjelkavik-Pedersen method for numerical integration, is applied to compute the field in the reg ion of the image. The method does not rely on small-angle approximatio ns and works well for a pupil of general shape. Both scalar and electr omagnetic computations are discussed and numerical results are present ed. (C) 1998 Optical Society of America.