MRI-R2: Development of Next-generation Imaging Spectrometer Based on a Tunable Liquid Crystal Filter

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。这项研究开发了一种基于电子可调滤光片的固态、频率捷变成像光谱仪。这种仪器被称为液晶(LC)高光谱成像仪(LCHSI)，解决了同时对多个波长的瞬变事件进行成像的难题。LCHSI的核心是法布里-珀罗标准具，其传输特性是通过在注入到缝隙中的液晶衬底上施加电场来控制的。该衬底被蚀刻成四个可单独控制的电隔离区域。然后，将得到的象限滤光片耦合到光束偏转棱镜上，在单个探测器上产生四个窄带图像。每个频道可以以毫秒的节奏单独调谐到数千种窄带颜色组合。因此，该仪器结合了基于色散的高光谱成像仪(HSI)的波长敏捷性和滤光轮相机的成像能力。与竞争对手的多光谱和超光谱系统相比，这种体系结构具有几个优势。同时多通道成像和电子调谐的结合使LCHSI具有极强的通用性。单个光链和固态滤光器的使用降低了尺寸、质量、成本和复杂性。静态滤光片会随着时间的推移而退化，导致其中心波长漂移，导致它们无法使用；因为LC滤光片是可调的，所以它不会退化，只需定期校准。LC滤光片也非常坚固，因此该技术是下一代星载成像系统的候选技术。尽管这项技术的应用非常广泛，但LCHSI的初步演示将在空气动力学领域进行，目标是气辉和极光光谱中的五种常见发射：427.8、557.7、630、732和777.4 nm。732和777.4线路可以在单个象限内调谐，从而测试波长跳跃能力以及带内和带外采样模式。测试将在位于波多黎各阿雷西博和格陵兰岛桑德斯特罗姆的NSF高层大气设施进行。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This research develops a solid state, frequency-agile, imaging spectrometer based on an electronically tunable optical filter. The instrument--referred to as the Liquid-Crystal (LC) Hyperspectral Imager (LCHSI)--solves the difficult problem of imaging transient events at multiple wavelengths simultaneously. At the heart of the LCHSI is a Fabry-Perot etalon whose transmission characteristic is controlled via an electric field applied across a liquid-crystal substrate injected into the gap. The substrate is etched into four electrically-isolated regions which may be individually controlled. The resulting quadrant filter is then coupled to beam diverting prisms to produce four narrow-band images on a single detector. Each channel may be individually tuned at millisecond cadence to thousands of narrow-band color combinations. The instrument thus combines the wavelength agility of a dispersion-based hyperspectral imager (HSI) with the imaging ability of a filter-wheel camera. This architecture has several advantages over competing multi-spectral and hyper-spectral systems. The combination of simultaneous multi-channel imaging and electronic tuning makes the LCHSI extremely versatile. The use of a single optical chain and a solid-state filter reduces size, mass, cost, and complexity. Static filters degrade over time resulting in a drift of their center wavelength, rendering them unusable; since an LC filter is tunable, it does not degrade, and need only be calibrated periodically. The LC filter is also extremely robust; the technology is thus a candidate for next-generation space-borne imaging systems.Although the applications of this technology are extremely broad, the initial demonstration of the LCHSI will be in the field of aeronomy, targeting five common emissions in the airglow and auroral spectrum: 427.8, 557.7, 630, 732 and 777.4 nm. The 732 and 777.4 lines can be tuned in a single quadrant, thus providing a test of the wavelength-hopping capability, as well as the on- and off-band sampling mode. Testing will be carried out at the NSF Upper Atmospheric Facilities at Arecibo, Puerto Rico, and Sondrestrom, Greenland.