轻小型可见/近红外实时成像光谱仪的光学系统设计

Design of Optical System for Miniature Visible/Near-Infrared Real-Time Imaging Spectrometer

为了解决传统成像光谱仪难以实现光谱和图像信息实时获取的问题,设计一款可见/近红外宽谱段视频型成像光谱仪系统。系统利用多狭缝分光成像技术,将目标光谱图像进行区域划分,代替传统的推帚型成像光谱仪,实现光谱维的大视场成像。采用低色散光学玻璃和双胶合透镜实现宽谱段光学系统的像差校正。前置望远物镜系统采用复杂的双高斯结构,实现小畸变设计和不同视场狭缝处能量的均匀分布。为了同时获取高空间分辨率的实时视频监控和高光谱分辨率,利用分光棱镜将前置望远物镜的像分为两路,一路直接由高分辨率全色相机接收,另一路进入分光系统由灰度相机接收。采用三块棱镜作为分光元件,通过优化材料组合和实际光线控制,获得了萤石-熔石英-萤石理想棱镜组合,实现了光路同轴性和良好色散线性度。设计结果为光学系统的光谱范围为400-1000 nm,F数为3.5,前置望远物镜奈奎斯特频率处设计调制传递函数（MTF）大于0.5,畸变小于0.1%,像面照度均匀性高于98%。整个系统奈奎斯特频率处设计MTF大于0.44,平均光谱分辨率为10 nm。

In order to solve the problem in traditional spectral imaging spectrometers that the spectral and image information cannot be acquired at the same time, a new type of real-time imaging spectrometer working in visible/near-infrared wide spectral range is designed. Different from traditional push-broom imaging spectrometers, the system is with multi-slits imaging technology that the spectral image of target is divided into several areas to achieve large field of spectrum. The system reasonably adopts low-dispersion optical glass and doublet lens to achieve aberration correction among wide spectral range. The front telescope objective system is a combination of complex double Gaussian structure to achieve small distortion and uniform illumination at slits for different fields of view. The image of telescope objective system is divided into two parts by prisms, and high spatial resolution of video monitoring and high spectral resolution of spectrometer are obtained. One part is received by a high-resolution panchromatic camera and the other is received by a grayscale camera. Triplet prisms are used as dispersion components. By optimizing the angle of prisms and controlling the actual light, a coaxial optical path and dispersion linearity is achieved with CaF2-silica-CaF2 structure. The results are as follows： spectral range of the optical system is 400~1000 nm, F number is 3.5, modulation transfer function （MTF） of distortion is lower than 0.1%, illumination uniformity at image plane is higher than 98%, and MTF of the front telescope objective system is more than 0.5 at the Nyquist frequency. The designed MTF of the optical system is more than 0.44 at the Nyquist frequency and spectral resolution is 10 nm.