title: On the usual approximation used in the Rayleigh-Sommerfeld diffraction theory.
abstract: The complete Rayleigh-Sommerfeld scalar diffraction formula contains (1 - ikR) in the integrand. Usually the wavelength is small compared with the distance of the observation point from the aperture and (1 - ikR) is approximated by -ikR alone. Other approximations usually made in the Rayleigh-Sommerfeld formula are addressed as well. Closed-form solutions, without approximations, are possible wherein interesting consequences of these approximations become apparent.
authors.affiliation: Optical Sciences Center, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Arvind S
authors.initials: AS
authors.lastname: Marathay
authors.forename: John E
authors.initials: JE
authors.lastname: McCalmont