Heterodyne speckle interferometer for full-field velocity profile measurements of a vibrating membrane by electronic scanning

Dynamic deformation measurements were carried out by combining full-field speckle interferometry and heterodyne interferometry. A digital demodulation technique based on the evaluation of the instantaneous frequency have been implemented in the digital signal processor of a complementary metal-oxide semiconductor (CMOS)-based camera to extract velocity measurements from phase modulated optical carrier signals. The purpose of this experimental investigation was to demonstrate a full-field laser vibrometer system that could replace electro-mechanical scanning with electronic scanning within a programmable stand-alone and relatively low-cost digital camera. Velocity profiles of a vibrating membrane in the order of few microns per second were reconstructed automatically by performing an electronic scanning of the surface over the image sensor.