An improved two-step phase-shifting profilometry

An improved two-step phase-shifting profilometry is put forward in three-dimensional (3D) shape measurement. Firstly, two phase-shifted randomly sinusoidal fringe patterns are projected onto the tested object by digital-light-processing (DLP) projector. The fringe patterns modulated with the object's surface are captured by a CCD camera. Secondly, the background and modulation components are obtained by parameter estimation using the least square method; fringe normalization is accomplished by the background bias removal and modulation normalization of a given deformed fringe. Then based on the statics characteristics of fringe gray, the phase step between two phase-shifted randomly sinusoidal fringe patterns is determined by using the inverse cosine function. Then, the phase is extracted from the two frame's normalized patterns and the step value. Finally, the experimental evaluation is conducted to prove the validity and performance of the proposed method. The experimental result is analyzed and compared with that of the method by reference 16. The effectiveness and superiority of the proposed method has been demonstrated.