借助于不同的色散公式，运用改进的单纯形法拟合分光光度计测得的透过率光谱曲线，来获得薄膜的光学常数和厚度。用科契公式分别对电子束蒸发的TiO2和反应磁控溅射的Si3N4，以及用德鲁特公式对电子束蒸发制备的ITO薄膜进行了测试，结果表明测得的光学常数和厚度，与已知的光学常数以及台阶仪测得的结果具有很好的一致性。这种方法不仅简便，而且不需要输入任何初始值，具有全局优化的能力，对厚度较薄的薄膜也可行。采用不同的色散公式可以获得各种不同薄膜的光学常数和厚度，这在光学薄膜、微电子和微光机电系统中具有实际的应用价值。

Based on the dispersion equations，“Downhill Simplex” method is utilized to measure the thickness and optical constants of thin film by fitting the curve of measured transmission spectrum. TiO2, Si3N4 thin films deposited by electron gun evaporation and reactive magnetron sputtering respectively are measured with Cauthy formula and ITO film deposited by electron gun evaporation with Drude formula. Experiments show that the results got by this method and by α-step apparatus agree well. No initial input is necessary for this simple method to realize the global optimization. With various dispersion formula, it is also suitable for many kinds of films with thinner thickness, which will be useful in thin film optics, microelectronic and micro-optical electro-mechanical system (MOEMS).