痕量气体掩星探测高光谱成像光谱仪光学系统设计

Optical system design of hyperspectral imaging spectrometer for trace gas occultation detection

痕量气体作为大气的重要成份,对地球的生态起着重要作用。为了实现宽波段、高光谱全天时连续测量,本文设计了一款在掩星探测模式下工作的高光谱成像光谱仪。该系统为共狭缝的双通道结构,紫外-可见光通道采用单凹面光栅结构、红外通道采用利特罗与浸没光栅结合结构,有效地减小了体积。利用软件对光学结构进行优化,优化结果表明:光谱仪在250~952 nm波段范围内工作,其中紫外-可见光通道工作波段为250~675 nm、光谱分辨率优于1 nm、MTF在奈奎斯特频率为20 lp/mm处均高于0.58、全视场各波长处RMS值均小于21μm;红外通道工作波段为756~952 nm、光谱分辨率优于0.2 nm、MTF在奈奎斯特频率为20 lp/mm处均高于0.76、全视场各波长处RMS值均小于6μm,均满足设计要求。结果表明该高光谱成像光谱仪系统可以实现对痕量气体的掩星探测。

Trace gases,as important constituents of the atmosphere,play an important role in the ecology of the planet.In order to realize the requirements of wide-band,hyperspectral and all-weather continuous measurement,a hyperspectral imaging spectrometer operating in occultation detection mode is designed in this paper.The system is a dual-channel structure with a common slit,the UV-visible channel adopts a single concave grating,and the infrared channel adopts a structure combining Littrow and immersion grating,which effectively reduces the volume.The software is used to optimize the optical structure,and the optimization results show that the spectrometer operates in the range of 250−952 nm wavelengths,of which the UV-visible channel operates in the wavelength range of 250−675 nm,the spectral resolution is better than 1 nm,the MTFs are all higher than 0.58 at a Nyquist frequency of 20 lp/mm,and the RMS values at various wavelengths of the full-field-of-view are all less than 21μm;the infrared channel operates in the wavelength band of 756−952 nm,the spectral resolution is better than 0.2 nm,the MTF is higher than 0.76 at the Nyquist frequency of 20 lp/mm,and the RMS value at each wavelength in the whole field of view is less than 6μm,all of them meet the design requirements.It can be seen that the hyperspectral imaging spectrometer system can realize the occultation detection of trace gases.