Measurement and analysis of defocused point spread functions and optical transfer functions of a microscope

The defocused point spread functions and optical transfer functions of a microscope were measured and analyzed. The main purpose of the analysis was to verify the accuracy of analytical approximations of these functions, which were presented but not extensively studied in the literature. The measured results were compared with those calculated by Castleman's (1979) theoretical approximation, in the space and frequency domains, graphically and numerically. The results showed that for the numerical apertures used, the theoretical functions were close to the measured functions, and thus Castleman's theoretical approximation is a fairly good approximation. These defocused point spread functions are being used for the optical sectioning as part of microscope image visualization system described by Li, Agathokils, Peet, Jensen and Sahota (see Proceedings of 1993 Canadian Conference on Electrical and Computer Engineering, p.1013-1016, Sept. 1993, Vancouver).