基于短波红外高光谱遥感应用的新型轻小型可扫描光谱分色元件研究

Applications of SWIR hyperspectral remote sensing technology in fields of UAV systems, military reconnaissance, deep-space exploration, etc. put forward higher requirements for miniaturization and lightening of hyperspectral imagers. Tunable Fabry-Perot filters (TFPF) studied in this project adopt time-modulation method for adjusting spectrum and the adjustable filter performance are realized by changing the length of Fabry-Perot (F-P) cavity. This new type of light-small and scannable spectral-splitting elements can greatly simplify the spectral-splitting system of spectral imaging equipment and accelerate the miniaturization and lightening progress of imaging spectrometers. However, in the process of changing the length of F-P cavity, the requirements of strict maintaining of parallelism in the order of 1/10 μrad between the two mirrors and precise control of the change of cavity length in accuracy of nanometer have always been cruxes which limit the applications of large-aperture TFPF in hyperspectral remote sensing. This research intends to use capacitive feedback and piezoelectric driving to adjust the air gap thickness and parallelism between the two mirrors of F-P cavity. High-precise parallelism between two mirrors and speedy&accurate adjustment of the cavity length will be achieved by nanoscale high-accuracy control of output displacement of piezoelectric actuators, ensuring high spectral resolution and fast passband switching speed of the TFPF. Research results of this project will be of great importance in expanding application platforms and environments of hyperspectral imagers.

短波红外高光谱遥感技术在无人机系统、军事侦察和深空探测等领域的应用，对高光谱成像仪的小型化轻量化提出了更高的要求。本项目研究的Fabry-Perot（F-P）可调谐滤波器，采用时间调制方式进行光谱调控，通过改变F-P腔的腔长实现可调滤波。该新型轻小型可扫描光谱分色元件能大大简化成像光谱设备的分光系统，加速成像光谱仪的小型化轻量化进程。然而，在F-P腔的腔长改变过程中镜面间1/10μrad级平行度的严格保持和腔长变化量的nm级高精度控制一直是限制大通光口径的F-P可调谐滤波器在高光谱遥感中获得应用的关键。本项目拟利用电容反馈和压电驱动调节F-P腔的空气间隙厚度和镜面间平行度，通过对压电致动器输出位移的nm级高精度控制来保证镜面间的高精度平行和腔长的快速精确调节，实现F-P可调谐滤波器的高光谱分辨率和迅捷的通带切换速度。项目研究成果将对拓展高光谱成像仪的应用平台和应用环境具有重要意义。

国内应用于航空航天遥感的高光谱成像仪普遍采用棱镜或光栅分光，分光系统占据空间较大，整机比较笨重。近年来，随着轻小型无人机遥感及微纳卫星技术的飞速发展，开发新一代低成本智能灵巧型高光谱成像仪已经成为未来高光谱遥感技术发展的必然趋势。本项目面向短波红外空间遥感应用，旨在研发一种新型的基于时间分光技术的轻小型可扫描的光谱分色元件，通过简化成像光谱设备的分光系统，加速高光谱遥感仪器的小型化和轻量化进程。所研究的可调谐F-P滤波器（TFPF）基于F-P腔的通带波长可随其腔长变化的选择性滤波原理，采用时间调制方式进行光谱调控，通过改变F-P腔的腔长实现可调滤波。在项目实施过程中，对TFPF的多级透射峰、反射镜结构设计和制备、高精密装配、腔长和平行度控制等问题等逐一展开了系统性研究，已获得具有自主知识产权的TFPF多级透射峰抑制技术和宽光谱范围大口径TFPF高精密装配技术，并针对研发需求开发出了一款TFPF扫描滤波专用设计软件。研制出通光孔径30mm，工作光谱范围为1.8~2.5μm，各通道峰值透射率＞70%，光谱分辨率~5nm@FWHM，光谱采样间隔~5nm，在700nm宽的波长范围内具备单通道扫描能力的短波红外TFPF。研究成果对开发新一代低成本、灵活机动、集成化、实时性强的智能灵巧型高光谱成像仪具有积极意义。