Contrast enhancement in double-beam interferometers

The interferometer fringe contrast ratio C is the most important figure of merit for interferometer performance. Low values of contrast drastically limit the use of double beam interferometers. The large values of contrast present in common path interferometers indicate that this deterioration is due to beam separation produced by nonideal beam splitters. Minimizing the negative effects of such beam splitters by the use of Double Beam Circular Interferometers (DBCI) and the use of plane- parallel beam splitters as well as collimating optics is suggested. Several new types of interferometers are described with improved contrast and stability.