Distance measurement with adjustable range by interferometry with Gaussian beams

We describe a technique for distance measurement in applications that require moderate precision. The technique is based on interference fringes resulting from the differing optical path lengths of two Gaussian beams traveling through the arms of a Michelson interferometer. From a propagation analysis of the beams, we find an expression that relates the distance between two surfaces and the resulting phase map from intensity images, making unnecessary the continuous tracking of the order of interference. The range of measurement of the method can be varied by the proper selection of the focal length of an expanding lens, from a fraction of a millimeter to a few centimeters. (c) 2005 Society of Photo-Optical Instrumentation Engineers.