Research On 3D Measurement Based On Color Phase-Encoded Fringe Projection

3D measurement method is playing a more important role in different domains, such as automatic industrial detection, computer aided design, computer aided manufacturing and reverse engineering. Normally,3D measurement method is divided into contact measurement and non-contact measurement. The 3D measurement based on color digital fringe projection, as one of the non-contact methods, attracts comprehensive attentions because of its high precise, large view-field, fast data-processing. In order to enhance the stability and accuracy of the color fringe projection technology, a lot of attention has been paid to the research on the quality of fringes. An improved fringe-decoding method is proposed to address the influence of the surface color on the fringe intensity and phase. Besides, an enhanced correct method is proposed, with phase as train objects of the neural network, which improve the stability of the decoupling system.1. An improved color stair-phase fringe projecting and phase-unwrapping method is proposed to overcome the adverse effects of the surface color of objects on unwrapping phase. 3 color sinusoidal fringes and 3 color stair-phase fringes are designed, based on the phase domain, each fringe with the same intensity in its three channels. Fringe patterns are projected by DLP projector onto the tested objects and the deformed fringe patterns are captured by a color CCD camera. The wrapped phase, stair phase and their corresponding modulation intensity of each channel are calculated. Comparing the modulation intensity of each channel pixel by pixel and selecting the phase with maximum modulation intensity as new stair phase. The orders of fringes is achieved by using proposed decoding method and matched to the wrapped phase correctly, then the precise unwrapping phase of object is obtained. The result of experiments shows that our method can significantly overcome the influence of the surface color of objects and retrieve the unwrapped phase correctly.2. A improved decoupled method based on BP neural network is proposed to address the problem of cross-talk in the color CCD camera. A new coupled response model, selecting phase as the train object of neural network, has been established to describe the complicated coupled response relationship in the single-CCD camera. Considering that custom correct methods using the fringe intensity as correct object, which is inevitable to the change of environment, needs more trains to complete one measurement. Since the phase domain is stable compared to the intensity, our proposed method selects the phase as the train and correct object of the network. Only needing one train can the system be used to custom measurement. The simulations and experiments demonstrate that the proposed method can eliminate the cross-talk remarkably and stably, and improve the measurement accuracy.3. We developed a 3D measurement based on color digital fringe projection after the theoretical researches on different parts. Our system includes hardware architecture and software system. Abundant experiments has been researched on our system, and the outputs of experiments demonstrate that our 3D measurement system can achieve accurate and continuous height distribution. Besides, by using optimal matching method pixel by pixel, we can restore the vivid color of the measured objects.