Phase contrast set 10x/40x, BMS D3

Phase contrast is the method used in light microscopy and was developed on the principle that if you speed up a direct light path, you can cause destructive interferences patterns in a viewed image. These patterns make details in the image appear darker against a light background. To cause these interferences patterns, a system of rings located both in the objective lens and in the condenser system must overlap. When aligned correctly, light waves emited from a light source reach your cornea one-half of the wavelength out of phase, resulting in a specimen with details that are greatly enhanced. Phase contrasting is only useful on the specimen that is colorless as well as transparent in nature and usually difficult to distinguish from its
surroundings. Such specimens are referred to as “Phase objects”. Examples of phase objects include cell parts in protozoans, bacteria sperm tails and other types of unstained cells.