Three-dimensional shape measurement of complex surfaces based on defocusing and phase-shifting coding

Abstract

Binary fringe defocused projection is a promising method for high-speed, high-accuracy three-dimensional (3D) shape measurement because of the advantages of superfast projection and capability to overcome the nonlinear gamma of the projector. However, the application of this approach for complex surface measurement remains a challenge. Thus, a method that combines binary fringe and phase coding fringe based on defocusing is proposed to achieve fast-speed, high-accuracy 3D shape measurement of complex surfaces. However, in the case of defocusing, as the number of phase coding fringe cycles increases, the fringe order k(x, y) becomes difficult to judge, errors occur in the jump area, and the periodic dislocation problem becomes worse, ultimately leading to phase unwrapping error. A phase-shifting coding method is thus presented to resolve these issues. This method not only alleviates the difficulty in judging the fringe order as a result of defocusing but also resolves the correction problem, and in turn, the periodic dislocation problem. Thus, measurement accuracy is improved. Experimental results demonstrate the feasibility and superiority of the proposed method.