Technology Research, Based On The Optical Media Features Of The Theory Of Spectral Interference Measurements

This article studies the measuring technique of optical medium based on spectrum interference theory. Base on the process of building physical model,theoretical derivation,mathematical simulation and experiments,a general optical measuring technique based on interference theory and spectrum measurement is presented. As a result of interference of light,the spectrum distribution of light will change in some condition when it pass through some medium,and the change is determined by the parameter of the medium. So we can determine the parameter of the medium by measuring the spectrum variation. This is the main idea of the measuring technique. This article separately introduce the measuring technique of optical isotropic medium and optical anisotropic medium.This article has three parts. The fist part studies the measuring theory of optical anisotropic medium. If a optical anisotropic medium wafer is put into the mid of a polarizer and a analyser,the spectral transmission of the optical system can calculated. The transmission is determine by the birefringence and the thickness of the medium. So we can determine the thickness of medium by measure the spectral transmission. This part firstly studies the relation between spectral transmission of the optical system and the thickness of medium. Then a linear search algorithm base on analysing of the shape of curve is discussed. The simulation results show that the fitting error and the computing time of the algorithm satisfy the practical measuring requirements.The second part of the article studies the measuring technology of multi-layer thin film system. The structure and the thickness and optical constants of each layer determine the reflectance of the thin film system. We made simulation of the determination of layer thickness of thin film system from is spectral reflectivity curve. The selected algorithm includes simulated annealing algorithm,genetic algorithm,Conjugate Gradient algorithm and DFP algorithm. The simulation results indicate that combination of simulated annealing algorithm and Conjugate Gradient has the best computational efficiency.The second part introduce the measurement system and the software. The measurement system includes light source,optical system,spectrometer and computer. The software have four modules including spectrum measurement module,data processing module,optimizing computing module and parameter setting module. The experiment results of quartz wafer show that this measurement technology have many merits such as high-precision,quick and convenience.