光學薄膜為現今科技的重要技術之一，被廣泛地應用在日常生活中，例如眼鏡鍍膜和鏡頭上抗反射膜等應用，為了實現設計薄膜的光學特性，在製程過程中使用光學監控來輔助鍍膜為一有效的方法。因為鍍膜過程中，會因為腔體環境、溫度等原因造成材料之光學常數有些微變化，如果只固定材料折射率監控厚度是不足以鍍製高品質之薄膜。因此在此研究中，我們會利用穿透率隨時間產生的變化來計算即時之折射率，並將其應用於反射係數監控中，利用此方法鍍製窄帶濾波片，其成果中心波長誤差小於0.5奈米、中心波長之穿透率誤差小於1.5%以及半高寬誤差小於1.4奈米。
研究中亦將其應用於鍍製更困難的雙腔窄帶濾波片，其成果中心波長誤差為0.15奈米、穿透率誤差為2.18%，以及半高寬誤差為0.2奈米，結果可知將即時監控折射率之方法應用於反射係數監控法擁有更高的準確性以及重複性。

Optical thin film is an important technology and it is widely used in daily life. For example, the anti-reflection (AR) coating on the glasses and camera lens. Owing to achieve the design properties of optical film, the optical monitoring assisted deposition is an effective method. In the coating process, the changes of chamber environment and temperature will cause changes in refractive index of materials. If the refractive index is fixed in the monitoring process, the results will different to the design.
In this research, the real-time refractive index was calculated by the transmittance information, and applies to the reflection coefficient monitoring to deposit the narrowband filters. The error of monitoring wavelength is less than 0.5 nm, and the difference of transmittance and FWHM is less than 1.5 percent and 1.4 nm, respectively.
We also apply the method to deposit the dual-cavity narrowband filter. The error of monitoring wavelength is 0.15 nm, the difference of transmittance and FWHM is 2.18 percent and 0.2 nm, respectively.
In conclusion, the reflection coefficient monitoring applied the real-time refractive index could been a very high accuracy and repeatability method.

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