Contouring of column by phase-measuring profilometry and four digital images

An improved method is proposed to perform contouring on column basing in phase-measuring profilometry. The four images including body, body and grating, grating, and the reference plane are acquired by a digital camera. The shade area and the shape area of body are also obtained with the processing between four images. The main axis of the projector and the main axis of camera are not crossed and are also not in the same plane to arrange the measuring system easily and conveniently. The unwrapped phase is also easily obtained with the help of an adaptive bandpass filter and a modulation function because phases between adjacent unwrapping points are continual (in generally < 2 pi) in the body area of image. The formulas for the phase subtraction and the geometric points are first provided for the no-cross-axis technique. The experimental results show that this technique is available for practical applications. (c) 2006 Society of Photo-Optical Instrumentation Engineers.