Research On The Fast-speed, High-accuracy 3-D Shape Measurement

With the perfect fusion of the optical, mechanical and electrical integration, optical non-contact 3-D shape measurement method is thoroughly studied and widely used.Traditional fringe projection profilometry(FPP) method has a good measuring effect for the static objects which has been matured application in industrial measurement. But it’s difficult to achieve fast-speed, high-accuracy 3-D shape measurement. With the development of the industrial automation, it is more important to achieve fast-speed,high-accuracy 3-D shape measurement. Rapid measurement has been widely application in security field(face and fingerprint identification), medical diagnosis(heart beat monitoring), products online monitoring(the passing rate of the industrial products) and etc. The defocused binary fringe projection method has been extensively studied as its ultra-fast measurement speed and high measurement accuracy. This paper aimed to the key research issues of the fast-speed, high-accuracy 3-D shape measurement based on the defocused binary fringe projection method.The main content of this paper is as follows:1. The binary fringe plus gray-code fringe defocused projection method is proposed to achieve fast-speed, high-accuracy 3-D shape of the complex surface. For a long time, binary fringe defocused projection method is just mainly applied to the 3-D shape measurement which the surface topography is relatively simple, it still remains a challenge to the complex objects. This paper aimed to the key technology research on the 3-D shape measurement of complex surface based on the defocused binary fringe projection method, A method that combines binary fringe and gray-code fringe based on defocusing is proposed to achieve fast-speed, high-accuracy 3-D shape of the complex surfaces. As the problem of the edges of Gray code fringe become smooth and exist transition area owing to defocus, which lead to errors of the solved fringe order k(x, y),the positive and inverse Gray code fringes are used to achieve the edge detection of the gray-code fringe. Finally, the 3-D shape of the complex surface can be achieved. By the research of the proposed method, it can expand the 3-D shape measurement of the complex surface using the defocused binary fringe projection method.2. Binary color-code fringe defocused projection method is proposed to achieve fast-speed, high-accuracy 3-D shape measurement of the object. A widely used method in fast-speed 3-D shape measurement, color-code fringe projection requires the projection of only one image. Binary color-code fringe defocused projection method is proposed. As the projected fringe is compounded by binary fringes, the projection speed can greatly enhance from 120 Hz to tens of kHz because it only has two grayscale values(0 and 255).A standard sinusoidal color-code fringe can be generated by properly defocusing the binary color-code fringe, it can overcome the influence of the nonlinear Gamma, as well as high harmonics and high-frequency noise and ultimately improving measurement accuracy. Experiment results show that the proposed method can get a higher result in measurement speed and accuracy compared with the traditional method.