Absolute Phase Measurement Method for Digital 3D Profilometry System

Digital 3D profilometry is a non-contact, full-field, and fast method for 3D profile digitization. It has a relatively simple setup and acceptable measurement accuracy. Traditional phase shifting technique uses single frequency fringe pattern for coding the depth information and an unwrapping procedure is required for decoding. Usually, the object has to be a continuous surface without any disconnected part or large height discontinuities. In this paper, a new method of three-frequency fringe pattern is presented to measure objects with complicated structures, which have large surface height discontinuities, or contain separated components. Principles and procedures are described. Experimental application is given and limitations are discussed.