Internal Stray Radiation Analysis of Uncooled Thermal Infrared Imaging Spectrometer

The cooled thermal infrared imaging spectrometer use blacken surface to absorb the stray radiation of outside the field of view and reduces the thermal radiation by decreasing the temperature. Though the system performance is high, it has problems such as high cost, large power consumption, large volume, and low reliability. The uncooled thermal infrared imaging spectrometer, which has the advantages of small size, low cost and long lifetime, has great potential to monitor high temperature targets such as forest fires,but the high emissivity of blacken surface will become a huge thermal radiation source, which will affect the imaging performance seriously. Its application and development are constrained by the disadvantages such as low signal to noise ratio, high infrared stray radiation and so on. In this paper, we present an uncooled long-wave infrared imaging spectrometer working between 3 mu m and 14 mu m. The system is composed of three components, including baffle, foreoptics and spectrometer. We adopt two different mechanical surface processing methods, i.e. the black nickel coating method and the surface polishing method. Then we analyzed the influence of the two methods on the internal thermal radiation at 300K, and compared two methods with the analysis results of the blacken method. We find that the radiation of the black nickel coated surface can reduce stray radiation by 20%, while the polished surface can reduce stray radiation by 50%. According to the analysis results, we can find that the polished surface method has better radiation suppression performance than the black nickel coating method for the designed uncooled thermal infrared imaging spectrometer.