Temporally Modulated Holography

Abstract

It is shown that temporal modulation of the object and/or reference wave in holographic interferometry can advantageously control fringe characteristics. The work presented is based on the concept that the hologram recording process acts as a filter applied to the cross correlation between the conjugate of the reference wave spectrum with the object wave spectrum. The filter is determined by the shuttering of the hologram. Specific types of modulation are considered both experimentally and theoretically. With single-sideband suppressed-carrier modulation of either the reference wave or object wave the hologram process can act as a heterodyne detection system for small-amplitude vibrations or as a system with a controllable number of fringes for large-amplitude vibrations. Certain types of modulation, such as sinusoidal phase modulation of the reference wave, are shown to give the relative phases of the object vibrations. Consideration is given to synthesizing general fringe patterns in multiple exposure holograms. Generalized strobe holography is also analyzed.