光学镀膜宽带膜厚监控系统

摘要

Because the target transmissivity (reflectivity) must be determined in advance in any conventional wideband monitoring of optical film thickness, this paper puts forward an imagination of mapping out parameters of film thickness and dispersive coefficients (refractive index) and continuously modifying target transmissivity in a coating time, by which the defect of the conventional wideband monitoring of optical film thickness can be overcome. The system of wideband monitoring of optical film thickness based on modifying target transmisivity has been built up. Its construction and working theory have been discussed . The accuracy of transmissivity measured by the system is higher than 2‰. A series of experiments of monitoring film thickness have been accomplished. It has shown that the accuracy of monitoring by the system is higher, the repeatability is better, and the accuracy of judging the end of coating is higher than1%.%针对过去的宽带膜厚监控法必须依赖镀制前设定的目标透射率（反射率）的固有缺陷，提出了在蒸镀过程中及时拟合出所镀层的膜厚、色散系数（折射率）等参数，并据此不断修正目标透射率（反射率）的设想，从而从根本上克服过去的宽带膜厚监控法的固有缺陷。建立了基于修正膜层目标光谱特性的宽带膜厚监控系统，阐述了它的结构和工作原理。进行了稳定性实验及一系列镀膜监控实验，实验结果表明，该系统透射率的重复测量精度优于2‰，膜厚监控精度较高，重复性好，各层的终点膜厚判定精度优于1%。