Diffracted-light contrast enhancement: a re-examination of oblique illumination.

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 produced on a research grade microscope is of very high quality, comparable to that obtained with DIC. Copyright 1999 Wiley-Liss, Inc.