Manipulations of Wavefront Propagation: Useful Methods and Applications for Interferometric Measurements and Scanning.

Phase measurements obtained by high-coherence interferometry are restricted by the 2 π ambiguity, to height differences smaller than λ /2. A further restriction in most interferometric systems is for focusing the system on the measured object. We present two methods that overcome these restrictions. In the first method, different segments of a measured wavefront are digitally propagated and focused locally after measurement. The divergent distances, by which the diverse segments of the wavefront are propagated in order to achieve a focused image, provide enough information so as to resolve the 2 π ambiguity. The second method employs an interferogram obtained by a spectrum constituting a small number of wavelengths. The magnitude of the interferogram's modulations is utilized to resolve the 2 π ambiguity. Such methods of wavefront propagation enable several applications such as focusing and resolving the 2 π ambiguity, as described in the article.