Point-spread functions of a polarizing microscope equipped with high-numerical-aperture lenses

In an effort to establish the imaging properties of a new type of polarized -light microscope, we recorded images of small, uniaxial, birefringent crys tals. We show that the sequence of in-focus and out-of-focus images, the so -called point-spread function, of a submicroscopic crystal can be used to m easure the orientation of its optic axis in three-dimensional space. By ana logy to conoscopic images out-of-focus images reveal the changes in relativ e phase shift between the extraordinary and the ordinary rays that propagat e at different directions through the crystal. We also present simulated im ages of a pointlike anisotropic scattering particle and compare these with our experimental findings. The theoretical model is based on a complete vec torial theory for partial coherent imaging by use of polarized light and hi gh-numerical-aperture lenses. (C) 2000 Optical Society of America. OCIS cod es: 180.6900, 120.2130, 260.1440, 180.3170, 050.1940.