A large spectrum of living biological specimens are virtually transparent when observed in the optical microscope under brightfield illumination. To improve visibility and contrast in such specimens, microscopists often reduce the opening size of the substage condenser iris diaphragm, but this maneuver is accompanied by a serious loss of resolution and the introduction of diffraction artifacts. Phase contrast was introduced in the 1930's for testing of telescope mirrors, and was adapted by the Carl Zeiss laboratories into a commercial microscope for the first time several years later. This technique provides an excellent method of improving contrast in unstained biological specimens without significant loss in resolution, and is widely utilized to examine dynamic events in living cells.
How I discovered phase contrast. Science 121: 345-349 (1955). Dr. Zernike's Nobel prize address delivered in Stockholm Sweden when he was awarded the 1953 Nobel prize in physics. The brief review provides a light-hearted discussion of events surrounding the discovery and provides several of the first images captured on film using the methodology.
Phase contrast, a new method for the microscopic observation of transparent objects. Part I. Physica 9: 686-698 (1942). The first of two original articles on phase contrast microscopy by the Nobel prize winner Frits Zernike. Written in the early 1940s, this paper reviews specimen contrast, amplitude and phase gratings, oblique and darkfield illumination, and introduces phase contrast.
Phase contrast, a new method for the microscopic observation of transparent objects. Part II. Physica 9: 974-986 (1942). A thorough treatment of the theory underlying phase contrast microscopy. A variety of configurations for phase plates (strips) are discussed, as well as their position in the microscope optical train. The treatise also includes numerous examples of specimen images.
Phase Microscopy 1954-1956. Science 124: 810-814 (1956). An early review of the technique that contains numerous references to original pioneering papers. The discussion includes general aspects, theory, instrumentation, contrast-enhancing technique combinations, general methodology, videos, and the most important applications. This paper is a good source for early references with examples of imagery.
Phase contrast microscopy. European Journal of Physics 6: 139-142 (1985). A practical treatise on phase contrast written for novices in the field. The authors discuss Abbe's theory of image formation, phase contrast microscope configuration, phase plates, and they provide several images of a phase grating under various illumination schemes.
Phase microscopy. Transactions of the American Microscopical Society 65: 99-131 (1946). Although published over 50 years ago, this practical aspects article is still an excellent source of information about the theory and practice of phase contrast microscopy. A solid discussion of theory is supported by experimental results in terms of contrast generation.
The advantages and uses of phase contrast microscopy. Journal of Bacteriology 21: 143-145 (1958). The author discusses the application of phase contrast microscopy in the field of bacteriology accompanied by some of the first images of bacteria captured using the technique. Although this is an early report, it highlights how phase contrast rapidly overtook other contrast methods of the period.
Phase contrast imaging: A generalized perspective. Journal of the Optical Society of America 26A: 1015-1021 (2009). The authors present a novel mathematical approach to describe phase contrast imaging when applied to analyze the interferometric phase contrast technique and phase contrast methods, which are based on spatial filtering of the undiffracted or diffracted light.
Relief phase contrast: A new technique for phase-contrast light microscopy. Microscopy and Analysis 21: 9-12 (2007). The author reports on relief phase contrast, a new modification of conventional phase contrast that leads to visible improvements of image quality in light microscopy. Discussed are contrast, focal depth, sharpness, three dimensionality, planeness, and halo artifacts.
Variation on Zernike's phase-contrast microscope. Applied Optics 39: 2152-2158 (2000). The authors report the design, construction, and testing of a variant phase contrast miroscope where the specimen is illuminated with a white light source through an annular aperture projected onto the entrance pupil of the objective. On the return path, the diffracted light from the specimen is separated from a reference beam.