Wednesday, March 07, 2007

Darkfield microscopes employ a special contrast enhancing technique known as dark field illumination to produce beautiful images of normally difficult-to-observe biological specimens. Under phase contrast conditions, the light coming through the specimen is shifted into two beams, one slightly out of phase with the other. This gets a little complicated to explain easily, but as far as equipment concerns, you need two matched items in order to get phase contrast. Similar to the phenomenon of being able to see stars at night but not during the day, darkfield illumination is most often used with samples that are not easily imaged against a light background, and results in samples that appear bright against a dark background. Darkfield microscopy is a very common and economical contrast technique to equip a microscope with, especially for low magnification use. The dark field microscope has found considerable use within the the field of live blood microscopy (sometimes referred to as live cell microscopy or darkfield analysis of live blood). However, dark field illumination is just as useful on an inverted metallurgical microscope, as well as for diatoms, small aquatic organisms and many other biological and metallurgical samples.