Piper, J.
Relief phase contrast: A new technique for phase-contrast light microscopy.  Microscopy and Analysis 21: 9-12 (2007).

Relief phase contrast is a new modification of conventional phase contrast which leads to visible improvements of image quality in light microscopy. In particular, the following parameters can be improved: contrast, focal depth, sharpness, three dimensionality, planeness, and halo artifacts. These effects can be achieved when the ring-shaped masks in the condenser are replaced by crescent- or punctate-shaped masks. Several solutions are described which are suitable to create this modification. The achievable improvements of image quality are relevant for all quality levels of objectives. The new technique can be used for phase contrast objectives from different manufacturers, so that the usual limitations of compatibility are eliminated.