SANDWICH, DOUBLE-REFERENCE-WAVE, HOLOGRAPHIC, PHASE-SHIFT INTERFEROMETRY

Phase-shift interferometry has provided a straightforward method for c onverting interferograms to phase maps. Unfortunately, some of the mos t powerful pulsed holographic interferometry techniques are generally not compatible with phase-shift interferometry. One solution is to emp loy two reference waves, one for each of the two object waves to be in terfered, that can be phase stepped during reconstruction. Practical a berration and alignment problems render this approach difficult. A sim ple method that employs a second hologram, sandwiched with the first, which produces the required two reference waves during reconstruction, is presented. The process compensates for both chromatic and geometri c aberrations that otherwise render the phase-shift method unusable.