Has anyone tried this?

Microscopy Today, Nov. 2006, has an article on DLC -- Diffracted
Light Contrast. It seems its a simple 'oblique' technique, using a
knige-edge at the filter position of the condenser to cast a
diffraction pattern on the specimen. It refers to this abstract:

Diffracted-light contrast enhancement: a re-examination of oblique
illumination.Piekos WB.
Department of Molecular, Cellular and Developmental Biology, Yale
University, New Haven, Connecticut 06520-8103, USA.
barry.piekos@...

A re-examination and modification of the very old oblique
illumination technique has resulted in a method for contrast
enhancement in microscopes, diffracted-light contrast (DLC), which
provides high-contrast, high-resolution images of unstained
biological material. The technique, which utilizes the diffracted
light from the edge of a small, opaque plate, provides shadowcast
images similar to those obtained by Nomarski DIC, anaxial
illumination, modulation contrast, or single-sideband microscopy;
however, it requires only a single additional component, which can be
added to any bright field microscope. The contrast and three-
dimensionality of the final image can be controlled by inserting
differently shaped edges. Any bright field condenser will work with
the technique and, consequently, it is a technique that may be
especially useful with relatively basic, inexpensive laboratory and
teaching microscopes although the image