1. An apparatus, comprising: a binocular viewing head that defines a first imaging optical path and a second imaging optical path; and a polarization exchanging beam splitter pair (PEBSP), the PEBSP including a pair of non-polarizing beam splitters configured so that a first non-polarizing beam splitter is situated to reflect an s-component or a p-component of an incident optical flux and a second non-polarizing beam splitter situated to reflect the s-component and the p-component of the reflected incident optical flux at the first non-polarizing beam splitter as a p-component or an s-component, respectively, at the second non-polarizing beam splitter, a variable waveplate, and a polarizer situated in the second optical path and configured to selectively direct specimen imaging fluxes corresponding to a first polarization state and a second polarization state to an imaging optical system associated with the second optical path.