基于Offner凸面光栅星载CO2成像光谱仪光学系统设计

星载CO₂成像光谱仪具有图谱合一、高空间分辨率、高时间分辨、非接触和长期监测的优点，已成为监测全球温室气体变化的重要手段之一。为解决大视场因入射狭缝较大，信噪比低，成像质量不佳的问题，文中对Offner成像光谱仪的光学系统初始结构设计提出了一种新方案。该方案基于在30 mm狭缝处发出的子午光线、弧矢光线在中心波长处相切，提高入射光线在整个光谱范围内的利用率。利用光学设计软件，设计在1594~1619 nm波段范围内，F数为2.5，光谱系统分辨率为0.1 nm的成像光谱仪。设计结果表明，点列图均方根（RMS）半径小于5 μm，系统在33 lp/mm处的传递函数优于0.7。此外，该系统采用像元合并（即扩展像元）的方法，进一步提高光谱信号的探测强度，该设计方案能够满足应用于星载CO₂成像光谱仪大视场、高光谱分辨率和高信噪比的遥感探测需求。

Optical system design of spaceborne CO2 imaging spectrometer based on Offner convex grating

Spaceborne CO₂ imaging spectrometer has become one of the important means to monitor global greenhouse gas changes due to its advantages of spectrum integration, high spatial resolution, high time resolution, non-contact and long-term monitoring. In order to solve the problems of large incident slit, low signal-to-noise ratio and poor imaging quality in large field of view, a new scheme was proposed for the initial structure design of the optical system of Offner imaging spectrometer. The scheme was based on the tangent of meridian ray and arc sagittal ray emitted at the 30 mm slit at the central wavelength to improve the utilization rate of incident light in the whole spectral range. Using optical design software, an imaging spectrometer with F number of 2.5 and spectral system resolution of 0.1 nm was designed in the range of 1594-1619 nm. The design results show that the root mean square (RMS) radius of the sequence diagram is less than 5 μm, and the modulation transfer function of the system at 33 lp/mm is better than 0.7. In addition, the system uses pixel merging (i.e. extended pixel) method to further improve the detection intensity of spectral signals. The design scheme satisfy remote sensing detection requirements of large field of view, high spectral resolution and high signal-to-noise ratio for spaceborne CO₂ imaging spectrometer.