Dynamic measurements of small displacements by laser interferometry

Abstract

A descriptive survey of optical noncontact detection of small dynamic displacements is made from the practical point of view of the use of laser interferometry. Photodetection processes are mentioned briefly for the purpose of understanding the time-averaging effect on the time-varying optical interference. Principles of optical homodyne, heterodyne, and two-frequency interferometry are reviewed for measurements of small dynamic displacements. Merits and demerits of these detection techniques are discussed by consideration of the minimum detectable amplitude for a simple harmonic motion.