3.5～4.0μm低温光谱带通滤光片的设计与研制

新一代气象卫星对红外带通滤光片的光谱控制提出了很高的要求:滤光片在工作温度(92K)下的光谱曲线被严格限定在一个由内、外框组成的区域之内。分别采用Ge和SiO作为高低折射率膜层材料,设计了含有4个谐振腔的带通膜系来提升通带边缘的陡度;对带通膜系中反射膜层的光学厚度进行了优化调整,压缩了通带内的波纹;根据膜层材料的折射率-温度变化特性,设计出了低温条件下符合光谱要求的带通滤光片。采用真空蒸发和光学极值监控的方法,研制出了92K低温下符合内、外框限制要求的带通滤光片,其通带内的峰值透射率达到93.2%,平均透射率达到91%,波纹幅度控制在5.2%以内。

Design and Fabrication of 3.5~4.0 μm Band-Pass Filter Working at Cryogenic Temperature

There is a very high requirement for the spectrum of the band-pass filter in the new generation meteorological satellite that at working temperature (92 K), the spectrum curve of the filter must be within an area restricted by an inner rim and an outer rim. Using germanium (Ge) and silicon oxide (SiO) as the higher and the lower refractive index materials respectively, a band-pass film system with 4 resonators is designed to obtain steep slopes at pass band boundaries. The ripple in the transmission region is flattened by means of optimizing the thickness of reflecting layers in the band-pass film system. The band-pass filter that satisfies the cryogenic spectrum requirements is designed, based on the refractive index versus temperature characteristic. Using vacuum evaporation technics and photometric extrema monitoring method, the band-pass filter has been developed and it meets the requirement of the inner-outer-rim specification at 92 K. In the transmission region, its maximum transmittance is 93.2%, the average transmittance is 91%, and the amplitude of the ripple is 5.2%.