四光束镀膜监控系统研究

光学镀膜的关键技术是准确监控膜厚，针对通用镀膜仪膜厚监控的稳定性、精度和自动化程度不高的状况，研究了全新的光电控制分析系统。提出基于双频率调制的四光束光电测试系统，采用双锁相电路系统和复合滤波的综合数字处理系统进行膜厚监控信号处理，并通过控制分析系统实现自动监控。测试结果经方差分析后表明：反映膜厚控制重复性的膜厚标准偏差小于0.55%；信噪比达到1000；数码显示值的线性度非常高，反射率的数码显示分辨极限为0.02%；系统静态漂移的线性程度很高，漂移率小于1.95%/h，静态稳定性优于通用系统2倍。新系统极大地提高了光学薄膜厚度监控系统的静态、动态稳定性、信噪比以及膜厚控制精度。

Optical Thin-film Depositing Monitoring with Four-light Beams

Accurate thin-film thickness (TFT) monitoring is key technique of optical coating. Considering of the poor monitoring conditions of universal coating equipments with low stability, precision and automation level, a new photoelectricity-control-analysis system is developed. Based on double-frequency modulation, a photoelectric test system with four-light beams was put forward. Dual-lock-phase circuit system and comprehensive digital processing system with compound filter were used to process monitoring signals, and all automation-monitoring functions were achieved with control-analysis system. Experimental results show that standard deviation of TFT, which indicates duplication of TFT monitoring, is equal to or less than 0.55%, that signal-noise ratio approaches 1000. A very good linearity of numeral display is obtained and the display resolution limit on reflectivity is 0.02%. The linearity of static drift is very high, the drift ratio is less than 1.95%/h, and the static stabilities of the new system are double superior to the universal system. In short, the static and dynamic stabilities, the signal-noise ratio, and the control precision of TFT are extremely increased.