Abstract
In this paper we present two numerical methods for the calculation of Gaussian field incident on a pinhole. The first method is based on Kirchhoff's Huygens aperture field method and the other on the spectrum of plane wave approach. Numerous calculations proved that Kirchhoff's Huygens method is faster and gives accurate results in the Fraunchofer region. The plane wave spectrum is the only one giving valid results ranging from the radiating aperture to, theoretically any distance, but the computational time is rapidly increasing for distances where the other method gives accurate and fast results.