Apodization and the point-spread autocorrelation function

Abstract

A novel function, the point-spread autocorrelation function (PSAF), which is closely related to the point-spread function, of a high numerical aperture microscope objective is introduced. The function is both experimentally measured and theoretically modeled for various apodization conditions. These include varying the effective numerical aperture of the objective, applying annuli of different size, and illuminating the objective with a spatially nonuniform intensity distribution. An excellent agreement between experimental data and theoretical modeling is obtained without the use of any fitting parameters. The PSAF technique is sensitive to the various apodization conditions, affecting both the width of the PSAF signal and the amplitude of the sidelobes. A potential use of the technique is the measurement of the effective numerical aperture and the optimization of the illumination conditions in complex microscopical systems.