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

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