A neoteric approach to interferometric phase imaging unencumbered by phase ambiguities is presented. This technique utilizes an actively controlled angular displacement glass plate positioned in the reference arm of an environmentally stabilized pseudoheterodyne Mach–Zehnder interferometer. The plate is continually adjusted to maintain a constant interferometric output phase, as a phase object in the sample arm is raster scanned. Using a source, unwrapped phase images of translucent samples ranging from approximately thick were obtained. This system is incorporated into a conventional near-field scanning optical microscope, which permits simultaneous phase, intensity, and surface morphology studies.
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