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.

© 2004 Optical Society of America

Fresnel approximation for off-axis illumination of a circular aperture

C. J. R. Sheppard, P. P. Roberts, and Min Gu
J. Opt. Soc. Am. A 10(5) 984-986 (1993)

Focal shift and the axial optical coordinate for high-aperture systems of finite Fresnel number

Colin J. R. Sheppard and Peter Török
J. Opt. Soc. Am. A 20(11) 2156-2162 (2003)

Diffraction by a circular aperture: a generalization of Fresnel diffraction theory

C. J. R. Sheppard and M. Hrynevych
J. Opt. Soc. Am. A 9(2) 274-281 (1992)

Resolution for off-axis illumination

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J. Opt. Soc. Am. A 15(3) 622-624 (1998)

Fresnel diffraction by circular and serrated apertures illuminated with an ultrashort pulsed-laser beam

Min Gu and X. S. Gan
J. Opt. Soc. Am. A 13(4) 771-778 (1996)