Theoretical study of detection of a dipole emitter through an objective with high numerical aperture

The problem of detecting electric dipole emitters (such as a fluorescing mo lecule) through a microscope objective with a high numerical aperture is co nsidered. Exact vector-wave-optics results of the field distribution of the electromagnetic field in image space are derived. On the basis of these re sults, the collection-efficiency function (CEF) is calculated. This calcula tion is compared with a semigeometric approximation of the CEF, for which a new analytical formula is presented. The derived results are important for applications such as fluorescence correlation spectroscopy and single-mole cule fluorescence detection with a confocal microscope. (C) 2000 Optical So ciety of America.