增透膜的选择

Choosing of film of increasing transmission

在光学器件中,由于器件(如透镜、棱镜)表面的反射作用而使光能损失,为了减少光学器件表面的反射损失,常在器件表面镀上一层透明介质薄膜(称为增透膜),增透膜的效果与介质薄膜的折射率、厚度等相联系。本文以光波的电磁理论为基础,讨论了光波入射介质薄膜的反射,推导出了反射率公式,并进行了讨论。结果表明:当介质薄膜的厚度d=λ04n2(2k+1)时,反射率有最小值Rmin=n1n3-n22(k=0,1,2,…,n1,n2,n3分别为空气、介质薄n1n3+n22膜、光学透镜的折射率,λ0为光波在真空中的波长),而当介质薄膜的折射率n2=n1n3时,反射率R=0,基本上无反射。

The light energy will be lost due to the reflection of the lens's surface in optical devices. A layer of medium film is plated on the surface of such devices (called film of increasing transmission or FIT) in order to reduce the loss of surface reflection.The effect of FIT is relative to the refracting power and the thinkness of the medium film. Based on the electromagnetic theory of light waves,the reflection of light waves entering the medium film is discussed, and the reflectivity is deduced and discussed. The result shows the reflectivity is min \%R\%\-\{min\}=\%n\-1n\-3-n^2\-2n\-1n\-3+n^2\-2~2while the thinkness of medium film \%d=λ\-04n\-2(2k+1)\% (k=0,1,2,\:,n\-1,n\-2,n\-3\% are the refracting power of air, medium film and optical lens, \%λ\-0\% is the vacuum wavelength).The reflectivity \%R=0\% while the refracting power of medium film \%n\-2=n\-1n\-3\%, there is no reflection nearly.