红外中带滤光片的结构、带宽估算及调整

中波红外波段在航天、气象、遥感等领域有着重要的应用，为了提高信噪比，系统中经常使用高质量的红外中带滤光片。相对带宽是红外中带滤光片重要的指标，主要取决于光学薄膜的膜系结构和具体设计。首先给出双截止组合型、F-P型、多半波型等几种膜系结构，归纳了相对带宽估算公式。同时从实用性出发，对一些具体膜系结构进行了相对带宽估算和综合分析，结果表明多半波结构最为可行。针对多半波结构，提出了间隔层膜料和光学厚度的选择、采用等效膜、调整膜层折射率等相对带宽调整的方法。最后，利用上述相对带宽调整方法对红外中带滤光片进行了设计，给出了实际镀制结果，滤光片相对带宽指标满足设计要求。

Structure, bandwidth estimation and adjustment of medium bandpass infrared filter

The medium infrared band is widely used as an observation channel in applications such as space flight, meteorology and remote sensing. High quality medium bandpass infrared filters are often adopted in optical systems to improve signal-to-noise ratio. Relative bandwidth is a key specification for the medium bandpass infrared filter, which depends on the film structure and its design. Several film structures such as double cut-off structure, F-P structure, multi-half-wave structure are given, and their bandwidth estimation formulas are concluded. The relative bandwidths of the multi-half-wave structures were estimated and analyzed. The results indicate that half-wave structure is the most feasible solution. Relative bandwidth adjustment methods are put forward, such as using interval layer material, selecting optical thickness, using equivalent film, adjusting film refractive index. A medium infrared filter is designed with the suggested relative bandwidth adjustment method. The coating result shows that the relative bandwidth specification of the film meets the design requirement.