Optical Technology Of Long-wave Infrared Hyperspectral Imaging

Hyperspectral imager can detect the slightly different substance because of multi-channel spectral imformation. Long-wave infrared is one of the major atmospheric window and important range of spectral features of ground objects. Therefore long-wave hyperspectral imager has important application value, especially in mineral exploration, chemistry and chemical engineering, urban heat flow analysis, military field and so on.At first this paper introduced the domestic and overseas research status and development of long-wave hyperspectral imager. The technology of long-wave hyperspectral imaging will go toward to wide in width and high resolution as same as visiable and short-wave hyperspectral imaging. Through researched long-wave infrared light splitting technology and found the advantages of dispersion spectroscopic methods in long-wave infrared. Then designed a long-wave infrared spectrometer with long slit and small F number by improved Offner structure, and a telescope system which can matched with the spectrometer. And made a deep analysis of the core spectral components-convex blazed grating. At last, background radiation suppression method of long-wave infrared system has been studied, which laid a solid foundation for improving the performance of the instrument.The main research contents and innovation points of the paper as follows:1. Designed an optical system of long-wave infrared spectrometer based on convex blazed grating by improved Offner structure, which is the first one in China and has advanced performance index. The slit length is 60 mm and F number is 2. Its disc of confusion is less than 5μm and the MTF reaches diffraction limit, and its spectrum smile and distortion is less than 10μm.2. Made a deep research in the core spectral components, then put forward a design method of convex grating: optimization design of its diffraction efficiency firstly and then calculating its basic structure parameters. And evaluated the influence of kinds of error to the performance of the instruments. Which laid a foundation for multiple structure convex grating applying flexibly to hyperspectral imager.3. Studied the application of high-order aspheric surface in simplifying optical construction. And designed an approximate telecentric telescope with FOV 60° and F number 2 just using six lens. This telescope is very suitable for advanced hyperspectral imager with wide in width and high resolution.4. Analyzed the background radiation suppression method of long-wave infrared hyperspectral imager. Proposed that combining multiple room temperature suppression methods can elevate the temperature of cooling optical-mechanical system. That combining multiple methods just need cool the system to 200 K will get the same effectiveness as cool the system to 100 K which suppressed the background radiation only by refrigeration.