Dark field X-ray microscopy: the effects of condenser/detector aperture

In order to visualize the functionality of a biological cell, it is often d esirable to label specific proteins. In this work we concentrate on the opt ical theory of visualizing colloidal gold labels with soft X-ray microscope s, where scattering from small gold spheres used as labels dominates the im age. Using numerical simulations of bright and dark field imaging, we compa re different configurations of condenser and objective lenses in transmissi on X-ray microscopes, and configurations of detector and objective lens in scanning transmission X-ray microscopes. It is verified that the contrast o f small, closely spaced features is strongly affected by changes in these c onfigurations; the optimum situation is to have the condenser aperture (in TXM) or detector aperture (in STXM) equal to 3/2 that of the objective nume rical aperture. (C), 2001 Elsevier Science B,V, All rights reserved.