Sandwich, double-reference-wave, holographic, phase-shift interferometry.

Phase-shift interferometry has provided a straightforward method for converting interferograms to phase maps. Unfortunately, some of the most powerful pulsed holographic interferometry techniquesare generally not compatible with phase-shift interferometry. One solution is to employ two reference waves, one for each of the two object waves to be interfered, that can be phase stepped during reconstruction. Practical aberration and alignment problems render this approach difficult. A simple 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 geometric aberrations that otherwise render the phase-shift method unusable.