Three-dimensional Measurement Algorithm Using Surface Structured Light

Modern industry has reached a new developmental stage as a result of the rapid advancement of science and technology.Real-time,effective,and accurate three-dimensional measurement technology has become essential in industrial automation.Surface structured light technology,a three-dimensional measurement technique using active vision,has been widely applied in a variety of industries,including reverse engineering,industrial automation,and cultural heritage preservation.It still has a lot of issues when dealing with different measuring conditions.Thus,this paper research the three-dimensional measurement technology using surface structured light.For this measurement system,after the sinusoidal fringe patterns are projected on the measured object,optical triangulation method is used to reconstruct the three-dimensional information of the object.Finally,the three-dimensional information of the object is acquired following point cloud processing.Simultaneously,the nonlinear effect and high dynamic range of the projector are investigated in threedimensional measurement system,and the relevant key technologies are experimented and analyzed.(1)The inverse camera method is used for system calibration.The camera distortion model is analyzed and the keyhole imaging model is constructed.A system calibration method for projecting Gray code was elaborated,and the entire system calibration process was described,as well as relevant experimental analysis.(2)The phase retrieval method is researched for surface structured technique using fringe projection.In solving the wrapped phase,convolution demodulation method,Fourier transform method and N-step phase-shift algorithm are studied.In the phase-unwrapping algorithms,path-following method of spatial phase-unwrapping methods and frequency phase-shifting method in time phase solution are studied.Finally,the N-step phase shift algorithm and the multi-frequency phase-shifting method are experimented and analyzed.(3)Although the binary defocusing technique can solve this problem simply and effectively for the nonlinear phase error from projector,the binary defocusing pattern cannot completely replace the sinusoidal fringe pattern.Thus,Phase-based chaos genetic algorithm is used in this paper to optimize the binary defousing pattern generated by dithering technology.Simulations and experiments are both investigated and presented.Experimental results show that the rms error of 0.29-0.61 rad can be reduced by other algorithms.(4)In order to address the high-dynamic problem’s the three-dimensional measurement system using surface structured light technology,this paper proposes using the gray response curve to correct the gray value to improve the dynamic range of a single-frame image,and then use adaptive multi-exposure technology to solve the optimal three exposure times to expand the overall high-dynamic range.On the stepped block,the relevant three-dimensional reconstruction experiment is carried out.The experimental results show that the measurement error is between 0.2mm and 1.6mm for a large and complex object,and can be reduced to0.12 mm for a simple and small object.(5)The point cloud processing technology are researched,including point cloud denoising and smoothing processing.Point cloud registration and surface triangulation reconstruction are primarily studied.Finally,experiments and analysis were carried out on the three-dimensional reconstruction of David’s sculpture and a standard sphere.