Feedback Stabilized Phase-Measuring Holographic Interferometry
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
A closed-loop feedback technique is disclosed for stepping and stabilizing a phase-shifting device for use in phase-measuring holographic interferometry. The current limitation in phase-measuring holographic interferometry is related to the accuracy with which the average interference phase introduced by a phase-stepping device can be determined and controlled. Fig. 1 schematically shows implementation of the closed-loop technique to a conventional realtime holographic interferometry system. In addition to a video camera which views the interference wavefront, a second non-integrating point detector is used to monitor the average phase of the wavefront. A high frequency, low (Image Omitted) amplitude sinusoidal voltage is applied to a piezoelectric translator (PZT), which is the phase-shifting device.