Height sensitivity in 3D object shape measurement using dual-illumination phase shifting digital holography

Abstract

Phase shifting digital holography (PSDH) is used to record and reconstruct waves free of the zeroth order and twin image-diffractions. In this study, holographic fringes representing surface contours of constant elevation are generated from the phase difference of reconstructed waves when the illumination direction is changed. Important principles and experimental considerations of the technique are described in detail. The height sensitivity, ∆h, which depends on the angle between the two illumination directions, ∆θ, must be chosen according to the requirements of the system. Shape measurements of a flat object, a conical object, and a five-centavo coin have been carried out.