Research On Key Technologies Of Large Field Of View White Light Interferometry For 3D Topography Measurement

Large-scale and high-precision 3D topography measurement technology plays an important role in the field of ultra-high-precision machining inspection.The research and development of related instruments and equipment is related to the national core competitiveness and is of great significance to the development of China's manufacturing industry.The research object of this paper is the ultra-high precision measurement with large field of view in decimeter scale,lateral resolution in micron scale and elevation resolution in nanometer scale.The basic theory of this paper is white light interferometry.The purpose of this paper is to break through the key technologies in the field of high-precision 3D topography measurement with large field of view,including the design and measurement technology of large field of view double telecentric Michelson interference lens,the design technology of wide spectral range and high collimation uniform illumination system,and the 3D topography calculation method suitable for stray light interference superposition and spectral degradation.The main work of this study is as follows:1.This paper introduces the research background and application fields of 3D topography measurement technology,systematically reviews the realization mechanism of 3D topography measurement technology,analyzes the advantages and disadvantages of existing technology,summarizes the distribution framework of international mainstream measurement technology,introduces the development status of 3D topography measurement technology at home and abroad,and explains the technical blank in the field of"large field of view and high precision 3D topography measurement"in China.2.Innovatively put forward Michelson white light interference structure integrating illumination and imaging,and analyze the applicability of Michelson white light interference structure based on interference superposition theory and partially coherent light theory.Different from the previous formula,a new idea of using zero-order fringe extremum and spatial delay to solve the vector height distribution is put forward.The potential influencing factors of interferogram are discussed,the basic characteristics of interference field are analyzed,it is pointed out that interference superposition will cause the offset of the envelope pole,and the feasibility of using zero-order extremum solution and offset compensation to improve the calculation accuracy of vector height of three-dimensional topography is analyzed.3.The optimization design of Michelson white light interference system with integrated illumination and imaging is completed.The system characteristics are analyzed in detail under the conditions of wide spectrum and large field of view,and the boundary limits of optical system are defined.The imaging system is designed and tested,and the system distortion is better than 0.03%under the condition of large field of view imaging when the target spatial resolution is 45lp/mm,The MTF value has a probability of higher than 90%reaching 0.6.The spatial resolution characteristics of the lens in full field of view are verified by the resolution plate method and interferometer measurement method.In the illumination optical system,the complex Kohler illumination structure is used to achieve quasi-uniform illumination in the area of 100mm×100mm,the illumination unevenness is less than 3%,the incident angle of illumination light relative to the normal of the measurement plane is less than 1°,and the total radiation energy density is 475W/m~2.4.The physical simulation model of large field-of-view double telecentric Michelson interferometric imaging system is constructed.By using this model,the influence of step value of spectral integration wavelength of light source on interferogram,the influence of spectral bandwidth on fringe contrast and the influence of multiple interference superposition on interferometric measurement values are analyzed.It is found that stray light interference field will be produced on two working faces of the beam splitter prism near the focal plane of the object side.The degradation effect of the superposition of stray light interference field on the interference field of the target signal is emphatically analyzed,and the possible causes of fringe distortion and fringe broadening are studied and analyzed.5."Multi-peak linkage zero-order pole offset compensation method"is proposed and verified,and the algorithm is calibrated,verified and tested.Michelson white light interferometry test system is built,and the development of system driver software is completed.The existing three-dimensional topography calculation methods are summarized.According to the standard step topography processing results of interpolation method,barycenter method and Fourier transform method,the influence of multiple interference superposition effect and spectral degradation effect on interferogram is compared and analyzed."Multi-peak linkage zero-order pole offset compensation method"is proposed and verified,and the measurement results of this method are given.Finally,the applicability of this method is analyzed.