Study On Improvement Of Accuracy In Dynamic Three Dimensional Measurement Based On Infrared Fringe Projection

Optical three-dimensional(3D)measurement is a non-contact measurement method with the advantages of high speed,high precision and high resolution.It is widely used in industrial automatic detection,product quality control,reverse engineering,biomedicine,cultural relic protection,anthropometry and film special effects.Dynamic high-speed optical 3D measurement technology has a more extensive application prospect,but it cannot fully meet the requirements of practical application at the present stage.With the continuous development of computer technology and optoelectronic technology,the emergence of various high-performance devices and data processing algorithms,the dynamic optical 3D topography measurement technology will develop faster and better.The fringe projection dynamic 3D measurement is one of the most widely studied techniques,mainly including phase measurement profilometry and Fourier transform profilometry.Phase measurement profilometry has high precision but slow speed.Fourier transform profilometry has high measuring speed but low measuring precision.Therefore,high precision dynamic 3D measurement is mainly based on phase measurement profilometry.The phase shift error caused by motion is a key factor affecting the accuracy of dynamic 3Dmeasurement.Infrared light is a common light source in the 3D measurement of human face to reduce the influence of visible light on the subject.In fact,the response of black and white industrial camera to infrared light is obviously lower than that of visible light.To obtain high-quality images,the exposure time of the camera is longer,and the phase shift error caused by motion is more obvious.In this thesis,the improvement of accuracy of phase measurement profilometry based on infrared fringe projection in dynamic 3D shape measurement is studied.The main contents of this thesis are as follows:(1)The basic principle of phase measurement profilometry is introduced,and the influence of motion on the measurement accuracy of phase measurement profilometry is analyzed.(2)The phase extraction algorithm is discussed,and a method is proposed to improve the 3D measurement accuracy of dynamic scene with phase shift assisted by windowed Fourier analysis.The actual phase shift between the deformed fringes was estimated by the windowed Fourier analysis method,and the phase distribution of the deformed fringes was estimated by the least square method.(3)Although the measurement accuracy of the dynamic part of the phase is improved,the measurement accuracy of the static part of the phase is reduced by using the phase shift estimation method in the actual 3D scene measurement.A method for increasing accuracy of full-field phase is proposed.The dynamic and static parts of the scene is separated and dealt with different methods.In the dynamic part,the phase shifting method assisted by windowed Fourier analysis is used,while in the static part,the standard phase shifting method is used to calculate the phase of the deformed fringe.(4)A dynamic3 D measurement system based on infrared fringe projection was set up to verify the correctness of the proposed method.The main innovations of this thesis are as follows :(1)The windowed Fourier analysis is proposed to estimate the actual phase shift between dynamically deformed fringes,which effectively improves the estimation accuracy of phase shift and thus improves the accuracy of dynamic 3D measurement of phase measurement profilometry.(2)The method of dynamic and static separation is proposed,which effectively improves the 3D measurement accuracy of scenes containing both dynamic and static parts.