The Effect Of Imaging Slit On The Energy Received By Thermal Infrared Hyperspectral Imager

Thermal infrared hyperspectral imaging remote sensing is a new technology developed in recent years.It has become the focus of research with its characteristics of day and night detection and wide spectrum coverage.The features of typical thermal infrared hyperspectral imager are that target is imaged at the slit by a telescope objective as a primary image,and then the image at the slit is imaged again at the detector by a subsequent dispersion and imaging system as a secondary image.The energy of light wave received by the single-row detector(corresponding to a spectral band)is one of hundreds of the energy of light wave passing through the slit,and it is very weak.Therefore,slit is the key device of thermal infrared hyperspectral imager,and its size directly affects the realization of the sensitivity of the whole system.However,the calculation of the received energy of hyperspectral imager pixels based on geometrical optics is quite different from the actual measurement results.This paper studies this phenomenon and the main work is summarized as follows:1.The propagation of light energy in thermal infrared hyperspectral imager was analyzed theoretically and experimentally.The reason why the method based on geometrical optics is no longer suitable for thermal infrared band was pointed out.The influence of slit size on the received energy of thermal infrared hyperspectral imager pixels was studied.2.Finite-difference time-domain(FDTD)method was used to simulate and analyze the influence of slits of different sizes on the received energy of thermal infrared hyperspectral imager pixels,and the reasons were analyzed.The selection rules of slits in the design of thermal infrared hyperspectral imager and the calculation method of the received energy of detector pixels were given.3.Different sizes of slits were made,and the actual experimental device with the same parameters as the simulation system was built,and the energy ratio of the detector pixels was obtained when the slits sizes are different.The final experimental results are consistent with the simulation results,and the difference between the received energy and the simulated energy is not more than 5%.The error source of the experiment is the time noise of the detector pixel,which verifies the validity of the simulation results.