Multi-object 3D Measurement System Based On Structured Light Field Imaging

In recent years,3D measurement technology has been widely used in many fields such as intelligent manufacturing and inspection,reverse engineering,media entertainment,etc.These applications have placed higher requirements on the accuracy and real-time performance of 3D measurement systems.Achieving the rapid reconstruction of the same batch of multiple objects has important application value.The three-dimensional measurement technology based on structural illumination has become one of the most important methods in three-dimensional shape measurement due to its non-contact,flexible use,high measurement accuracy and other advantages.However,in a multi-target scene,it is difficult for traditional industrial cameras to obtain focus fringe images on the surface of multiple objects at different depths of field at once,which seriously affects the accuracy of the 3D reconstruction results of out-of-focus objects.In response to this problem,this thesis designs multi-object 3D measurement system based on structured light field imaging,which uses light field cameras instead of traditional industrial cameras as image acquisition equipment in 3D imaging.Since the light field camera can record the spatial intensity and angle information of the light at the same time,you can use computational focus and focus stack fusion to obtain the focus fringe images on the surface of multiple objects in the scene,and then use the full-focus fringe image for the three-dimensional reconstruction of multiple objects.Therefore,the goal of threedimensional reconstruction of multiple objects with different depths of field is achieved at one time.The three-dimensional measurement system implemented in this thesis is composed of hardware and software.The hardware part includes light field camera,digital projection module,computer,etc.The software part includes all-focus light field fringe image acquisition module,3D reconstruction calculation module,hardware Control module,etc.This thesis focuses on the software part of the measurement system.In the all-focus light field image acquisition module,the original light field data acquisition,decoding,and correction preprocessing are implemented to obtain four-dimensional light field data,which provides a data basis for the subsequent realization of frequency domain calculation focusing;then,based on the four-dimensional light field information recorded by the light field camera,a method to obtain the all-focus light field image based on frequency domain calculation focusing and focus stack fusion is proposed.In the three-dimensional reconstruction calculation module,the three-dimensional reconstruction of multi-objects combining phase shift profilometry and multi-frequency time-phase expansion is realized based on the all-focus fringe image.In addition,this thesis also studies the influence of the nonlinear error introduced in the image acquisition and calculation process on the phase calculation,discusses the six-step phase shift method that can effectively suppress the nonlinear distortion,and verifies it through simulation.In this thesis,the scene with two objects is selected to experiment with the designed system,and the measurement results are compared with the three-dimensional measurement results recovered by traditional industrial cameras.The experimental results show that the method in this paper can recover the out-of-focus objects better three-dimensional shape,which proves the effectiveness and superiority of the method used in this system.