四光束镀膜监控系统

Optical thin-film depositing monitoring systems with four-light beams

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,研究了一套新的光电控制分析系统。设计了基于双频调制的四光束光电测试系统,采用双锁相电路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<0.55%;信噪比达到1 000;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<1.95%/h,静态稳定性优于通用系统2倍。提出的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。

By considering the poor monitoring conditions of universal coating equipments with low stability, precision and automation level, a new kind of photoelectricity-control-analysis system was developed. Based on double-frequency modulation, a photoelectric test system with four-light beams was put forward. A dual-lock-phase circuit system and a comprehensive digital processing system with compound filter were used to process monitoring signals, and all automation-monitoring functions were achieved with a control-analysis system. The experimental results show that standard deviation of Thin Film Thickness（TFT） is equal to or less than 0.55%, and signal-noise ratio approaches to 1 000. 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 are double superior to that of universal system. It is concluded that proposed system has advantages of the static and dynamic stabilities, the signal-noise ratio, and the control precision for TFT.