Research On High Dynamic Range Fringe Projection Three-dimensional Measurement

Fringe projection 3D shape measurement technique is a widely used three-dimensional measurement method.Because of its non-contacting,high-accuracy and high-speed,it has a great application prospect in industrial production,information security,medical diagnosis and so on.However,the traditional 3D measurement with fringe projection has certain requirement for optical properties of the objects' surfaces.It's hard to achieve high-accuracy results for objects with high reflection because of the saturation in fringe images.Objects with high reflectivity exist widely,such as ceramics and plastics,and it's hard for traditional fringe projection 3D measurement to obtain a high result when measuring these objects.So researchers on the method for accurate measurement of objects with high reflectivity has great practical significance and value.In this thesis,the high dynamic range 3D measurement technique for fringe projection system is studied based on fringe projection system.The main work and innovations of this thesis are as follows:1.A new method of adaptive fringe projection high dynamic range 3D measurement based on binary search is proposed.In traditional adaptive fringe projection methods,the best projection intensity is calculated by estimating the response curve of the camera and the projector,which is time-consuming and unaccurate.In this thesis,the binary-search is used to realize a high-accuracy and high-speed searching for the best projection gray value.Besides that,the accurate coordinates matching between camera and projector is hard to realize with saturation in traditional adaptive fringe projection methods.To solve this problem,the method that changing the projection intensity to a low value which saturation do not exist and carry out the matching is proposed.The deficiency of the traditional adaptive fringe projection method is made up.With the proposed method,the adaptive fringe images could be obtained with a high-accuracy.With the generated fringe images,the saturation could be eliminated and high-quality phase could be obtained.2.For the non-repeatable measurement,which means only the saturated fringe images are obtained,a high dynamic range 3D measurement method based on improved phase-shift method and image inpainting is proposed.Traditional improved phase-shift method proposed to project inverse fringes to realize high dynamic measurement,which reduces the applicability of this method.By analyzing the phase-shift method,we proposed that the improved phase-shift could be applied to phase-shift measurement system with more than four phase step.And with the improved phase-shift method,the phase of saturation image pixels with low-saturation could be obtained.And to calculate the phase of high-saturated image pixels which could not be solved by improved phase-shift method,we proposed to repair the saturation images and then the phase of high-saturated pixels could be obtained with the inpainted fringe images.A new inapinting method is proposed to inpaint the saturated fringe images: first,the images is inpainted with the image intensities calculated from the phase of the low-saturated pixels,and then,further inpainting is carried out with the help of the image inpainting algorithm based on integral variational(TV)model.With the proposed inpainting method,the problem that traditional inpainting method could not realize high-accuracy inpainting when the inpainted areas is very big.When only the saturated fringe images are obtained,the proposed high dynamic range 3D measurement method based on improved phase-shift method and image inpainting could effectively reduce the phase error caused by saturation.