Design And Application Of Software Of Reverse Engineering Of Optical Coating

In the area of deposition of optical coating, it is very important to acquire the informations about optical constants and thicknesses of optical coating for fabricating the optical coating with high quality. Therefore, how to determine the optical parameters of optical coating precisely and rapidly has always been a focused issue for the researchers. With good global searching capability of the improved genetic algorithm based on elite selection strategy and fast local convergence capability of the non-linear least squares method with Levenberg-Marquardt algorithm, software of reverse engineering has been designed to determine the optical parameters of optical coating using fitting method of whole spectrum.Firstly, in this paper, the reflectance and transmittance formulas of optical coating were rigorously derived from electromagnetic theory, and fundamental theory of determining optical parameters of optical coating using fitting method of whole spectrum was introduced in detail. Then, merit function used in reverse engineering of optical parameters of optical coating was choosed reasonably.Secondly, genetic algorithm and non-linear least squares method have been successfully integrated, and the combined fitting method used in reverse engineering of optical coating has been built. The combined fitting method has avoided reaching a local extremum. At the same time, the problems of uncertainty of results obtained by genetic algorithm and necessity of initial value of non-linear least squares mothod have been solved in the combined fitting mothod.Finally, a stand-alone software of reverse engineering of optical coating has been worked out using Matlab7.8 and Visual C#. The software of reverse engineering of optical coating has been successfully applied to the reverse engineering of antireflection coating, narrow band-pass filter, mirror, beam-splitting coating and some other optical coatings, and all of them reached good results. Based on the relative sensitivity of the optical parameters of optical coating and the fitting degree of reflectance or transmittance, the results have been analyzed detailedly, which proved effectiveness and reliability of the software of reverse engineering of optical coating.