中波红外宽带通滤光膜通常膜系层数多，膜层总厚度非常大（厚度达到10 μm左右），膜层的镀制工艺难度较大。通过分析红外带通滤光片几种设计方法的特点，并结合实际镀制工艺技术，采用了长波通与短波通及非规整薄膜设计技术相结合的方法，设计了以锗材料为基底的中波3 μm～５ μm宽带通滤光膜。该设计大幅度降低了膜层的总厚度（约为8.65 μm），缩短了膜层的镀制周期，提高了膜层的牢固度；在膜层的镀制工艺过程中，通过改变薄膜材料的蒸发速率、修正蒸发硫化锌材料时电子枪的扫描方式、调整蒸发材料在坩埚中的装载方法，使膜层获得了优异的光谱性能，其通带平均透过率大于96%，截止区域的平均透过率小于1%。

The plating process of the mid-wave infrared broad-band pass filter is difficult because of multi-layers, and the total thickness of film layers is very big ( the thickness is up to about 10 μm). Through analysis of the design features of several infrared band pass filters, and combining with the actual plating technology, the 3 μm～5 μm broad-band pass filter with germanium substrate was designed by using the method of combining long-wave-pass, short-wave-pass and irregular film design technology. The design reduces the total thickness of film ( about 8.65 μm) greatly as well as the deposition time, and the firmness of the film is improved. The film obtains excellent spectral properties by changing the evaporation rate of film materials, correcting the scan mode of the electron gun when vaporizing the ZnS material, and adjusting the loading method of the evaporation material in the crucible. The average transmittance is more than 96% in the passband and less than 1% in cut-off region.