title: Fresnel diffraction by a circular aperture with off-axis illumination and its use in deconvolution of microscope images.
abstract: The Fresnel approximation for off-axis illumination of a circular aperture is reexamined. The point-spread function for an aberration-free system can be expressed in terms of redefined optical coordinates. An improved expression is given for contours of constant intensity in the focal plane. The variation in axial width of the focal spot with angle of offset is discussed. The predictions are compared with exact calculations of the Rayleigh-Sommerfeld diffraction integral. Limitations for application in deconvolution of microscope images formed with objectives of finite tube length are discussed.
authors.affiliation: Physical Optics Laboratory, School of Physics, University of Sydney, Sydney, NSW 2006, Australia. colin@nus.edu.sg
authors.forename: Colin J R
authors.initials: CJ
authors.lastname: Sheppard
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Cooper