3-D SHAPE MEASUREMENT BASED ON DITHERING TECHNIQUE

Projector defocusing technique can eliminate projector nonlinearity in real-time three-dimensional shape measurement. However, the high-frequency harmonics brought by defocusing technique weakens the sinusoidal feature of the defocused fringe patterns, which will bring obvious measurement errors. The dithering algorithm is proposed to generate binary fringe, the projector is defocused properly to achieve approximate sinusoidal fringes. This method improves the sinusoidal property of the defocused fringe patterns. Absolute phase is retrieved by applying this method and phase-shifting algorithm. Simulations and experiments are carried out to verify the proposed method, and results show that phase quality has been improved greatly. Compared with existing methods, the proposed method achieves higher precision and can generate fringe patterns more sinusoidal, which is more proper for projector defocusing technique.