Research On Linnik Type White Light Microscopic Interferometric Spectral Measuring System And Method

As a kind of new measuring method with characteristics of high efficiency and accuracy,white light spectral interferometry(WLSI)technology is being more and more widely applied to the relative field of Geometry measurement on micro/nano-scale.Different from traditional white light measurement,WLSI turns the measurement of interference fringe to the study of spectrum density function owing to the interference spectrum signal obtained by the spectrometer.That means the information of sample can be extracted by analyzing its interference spectrum properties.Combining the high speed of spectrum analysis with the high precision of interference measurement,WLSI can reach fast measurement with high accuracy.However,the traditional interference structure such as Michelson type or Mirau type can't work well when there are more complex samples or environment.So in this thesis,an unconventional white light microscopy interference spectral measurement system is come up with which is based on Linnik type inference configuration using double long working distance objectives.In this thesis,the main achievements are as follows:1.The research states of micro-nano geometrical parameter measuring technology and white light interference spectral measuring technology were understood deeply.And Linnik type interference was put forward to meet the need of long working distance.2.The basic principle of white light spectral interferometry was analyzed.The basic interference properties of white light,the analysis of interference fringes visibility,the mathematical model of white light microscopy interference and the coherence theory of light were described in detail.And the principles of measuring absolute distance and thin film thickness were introduced briefly.3.The Linnik type white light microscopy spectral measuring system was designed and built.It mainly included four parts: movement mechanism and mechanical support,the microscopic interference optical system,signal acquisition and imaging modules,programs and software.And the main work of programs concludes programming controlling of hardware device for achieving automation system and the optimization and supplement of date processing algorithm.4.The phase signal of this system was researched,and several phase extracting algorithms were introduced and compared.The influence of effective thickness on measuring system,the wavelength correction theory and the nonlinear phase distortion caused by double objectives were analyzed.And the nonlinear phase distortion from the overall phase was extracted under a certain conditions by a series of experiments.The initial estimates theory was introduced based on the frequency of nonlinear phase and local optimization algorithm for measuring the thickness of thin film.5.Experiments of system and environment stability were conducted.The measuring abilities and precision of the system were verified by absolute distance experiments,and the experiments of measuring thickness of thin film sample were completed.The necessity of eliminating nonlinear phase caused by double objectives and the feasibility of the system and measuring method were verified.