Research On High Frame Rate Sinusoidal Fringe Projection Technology Based On LED Array

With the development of intelligent and information technology,the demand for 3D measurement technology is increasing day by day,especially the non-contact structured light 3D measurement technology.Fringe projection profilometry is one of the most widely used and representative techniques in 3D measurement of structured light projection.The technique uses a projector to project the sinusoidal grating pattern onto the object to be measured,and then uses a camera to capture the deformed fringe image generated by the space modulation of the object to be measured,and obtains the phase diagram by solving it.Finally,three-dimensional data of the object is obtained by using the relationship between phase and depth.Fringe projection profilometry is widely used in high-speed 3D reconstruction due to its advantages of full-field measurement,high precision and good robustness.In this thesis,a high frame rate sinusoidal fringe projection method based on LED chip array is proposed.The LED chip array is controlled by timesharing to generate sinusoidal fringe field satisfying the three-step phase shift relation through the designed projection optical path.The method has the advantages of low cost and simple control.The main contents of this thesis are as follows:1.The 3D reconstruction process of fringe projection profilometry is introduced.The generation of various sinusoidal grating fringe fields and the theory of obtaining the enveloping phase in phase-shifting fringe profilometry are deduced,and the common phase calculation methods included time phase unwrapping algorithm and space phase unwrapping algorithm are deduced.Furthermore,some problems in the threedimensional measurement system of moving objects are discussed.The theory of diffractive optical element design is studied.2.Simulation,design and production of LED chip array projection system.LED chip array is the core device in this research,and the arrangement design,manufacture and control method of LED chip array are the important content of this research.The projection system can generate sinusoidal fringe field through the defocusing of cylindrical mirror or through the interaction of cylindrical mirror and phase plate.The feasibility of the two methods to generate sinusoidal fringe field is verified by theoretical derivation and simulation.In addition,other related modules of the projection system are designed and made.3.The high-speed fringe projection module based on LED chip array proposed in this thesis is experimentally verified.The projection brightness of the projection system determines the frame rate of the projection,so the verification experiment of the projection brightness is carried out.The projection module and the camera are used to construct a 3D measuring system for objects.A high speed 3D measurement system is constructed with LED chip array projection module and high speed camera,and 2000 Hz frame rate measurement is achieved.