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一、引言基于波长调制法膜厚控制系统的原理,对于所监控的膜层,当其光学厚度为监控波长的四分之一,或其整数倍时,控制仪表的指示应为零值。此时极值法仪表的指示应为极值。
I. INTRODUCTION Based on the principle of wavelength modulation film thickness control system, when the optical thickness of the film to be monitored is one quarter of the monitoring wavelength or an integral multiple thereof, the indication of the control instrument should be zero. At this point the method of extreme law instrumentation should be extreme.