消谱线弯曲长波红外成像光谱仪设计

Design of long-wave infrared imaging spectrometer with eliminating spectral curvature

为了实现遥感目标的长波红外高光谱成像,有效消除平面光栅产生的谱线弯曲,设计了离轴透镜消谱线弯曲长波红外平面光栅成像光谱仪。分别计算了平面光栅和离轴透镜产生的谱线弯曲,分析了谱线弯曲随相关参量的变化关系,并基于此设计了消谱线弯曲的初始结构。通过优化设计得到的光学系统的通光孔径为100mm,F数为2,光谱分辨率为20nm,空间分辨率为150μrad,冷光阑效率为100%,成像质量接近衍射极限,系统谱线弯曲由原有的180μm以上变为14.3μm以内。该项设计获得了具有普适性的消谱线弯曲公式,证明了离轴透镜具备校正谱线弯曲的特殊功能。最后的设计结果表明,在满足系统成像质量要求且不增加系统复杂度的前提下,采用离轴透镜的平面光栅光谱仪的系统谱线弯曲小于探测器像元尺寸的1/2,满足使用要求。

To achieve the long wave infrared hyperspectral imaging for remote sensing targets and to e- liminate the spectral curvature of a plane grating effectively, a long wave infrared imaging spectrome ter with an off-axis lens was designed. The spectral curvatures from the plane grating and a single off- axis lens were calculated, respectively, and the relationships between spectral curvatures and relative parameters were analyzed, then an initial structure for eliminating spectral curvature was designed. The optical system optimized shows an aperture of 100 mm, F number of 2, spectral resolution of 20 nm, spatial resolution of 150μm, and a cold aperture efficiency of 100% . Moreover, its image qual- ity is close to the diffraction limit and the spectral curvature of system changes from more than 180μm to less than 14. 3μm. The design obtains a universal eliminating spectral curvature formula, andproves that the off-axis lens has the function to eliminate spectral curvature. It concludes that the ima- ging spectrometer of plane grating using off-axis lens can offer a spectral curvature less than half the pixel size of the detector without increasing the system complexity, which meets the use request on the premise of satisfying imaging quality.