Real-time Measurement of Two-dimensional Displacement by the Quad Aperture Laser Speckle Interferometry

Abstract

Aiming to develop a new laser speckle interferometer which can non–contactly measure two–dimensional in–plane displacement in real–time, a new phase detector for measuring the two–dimensional phase of interference image based on two–dimensional Fourier transform was proposed and built as an analogue electronic circuit. The detected phase error for a pure two–dimensional sinusoidal intensity image was less than 4.2deg at 100Hz of measuring frequency. An actual interference image obtained with the laser speckle interferometer was also examined then the measuring error was less than 15 microns.