Research On Three-dimensional Reconstruction Method Of Structured Light Based On Multi-frequency Heterodyne

The structured light three-dimensional measurement technology has the advantages of non-contact,high efficiency and high precision.It is widely used in emerging technology fields such as 3D printing,biomedicine,virtual reality and industrial inspection.Among them,fourier transform profilometry and phase measurement profilometry are the most representative 3D measurement methods and are also the current research hotspots.In this paper,the phase measurement profilometry is selected as the research object.With the aim of improving the accuracy,anti-noise performance and stability of measurement,the phase error compensation of nonlinear response and the phase error correction method of multi-frequency heterodyne are studied.Specific research contents are as follows:Firstly,the basic principles of phase measurement profilometry are introduced,including phase shift method,multi-frequency heterodyne method,camera calibration,and mapping method from phase to 3D point cloud.Theoretically,the phase error of the multi-frequency heterodyne method is mainly derived from the nonlinear response of the system and environmental noise,which provides a theoretical basis for the subsequent phase error correction method.Secondly,this thesis mainly suppresses and corrects the phase error from two aspects.On the one hand,the dual four-step phase shift method is used to suppress the phase error caused by the nonlinear response.The principle is that the phase errors generated by two groups of grating stripes with a certain phase shift can cancel each other out.On the other hand,for the phase error caused by the multi-frequency heterodyne method phase unwrapping process,a correction method based on multi-level fringe series correction is proposed.The specific process is as follows: the phase period of the synthetic fringe is used to coarsely correct the first-order fringe order.By optimizing the quantization rounding function and utilizing the absolute phase containing phase error,the second-order fringe order is finely corrected.The target absolute phase can be calculated more accurately according to the corrected fringe order.Finally,in order to verify the effectiveness of our method,a three-dimensional structured light test platform is built.On the test platform,the traditional heterodyne method and our method are used to conduct the three-dimensional reconstruction experiment of the flat board and the circuit board.The experimental results are compared and analyzed.The experimental results show that our method can effectively suppress the phase error of the multi-frequency heterodyne method,improve the phase calculation accuracy and further improve the accuracy and reliability of 3D reconstruction.