Spherical warm shield design for infrared imaging systems |
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| Institution: | 1. Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan;2. Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 117105, Russia;3. Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 111005, Russia;4. Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580, Japan;5. Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA;1. P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow 119991, Russia;2. Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region 141701, Russia;1. State Key Laboratories of Transducer Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, PR China;2. Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, PR China;3. University of Chinese Academy of Sciences, Beijing 100049, PR China;4. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Chang Ning Rd., Shanghai 200050, PR China;1. School of Electrical Engineering, Henan University of Science and Technology, Luoyang 471023, China;2. China Academy Key Laboratory of Science and Technology on Infrared Detector, China Airborne Missile Academy, Luoyang 471009, China |
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| Abstract: | The F-number matching is the primary means to suppress stray radiation for infrared imaging systems. However, it is difficult to achieve exact F-number matching, owing to the restriction from detectors, or multiple F-number design. Hence, an additional shield is required to block the certain thermal radiation. Typical shield is called flat warm shield, which is flat and operates at room temperature. For flat warm shield, it cannot suppress stray radiation while achieving F-number matching. To overcome the restriction, a spherical reflective warm shield is required. First of all, the detailed theory of spherical warm shield design is developed on basis of the principle that stray radiation cannot directly reach the infrared focal plane array. According to the theory developed above, a polished spherical warm shield, whose radius is 18 mm, is designed to match an F/2 infrared detector with an F/4 infrared imaging system. Then, the performance and alignment errors of the designed spherical warm shield are analyzed by simulation. Finally, a contrast experiment between the designed spherical warm shield and two differently processed flat warm shields is performed in a chamber with controllable inside temperatures. The experimental results indicate that the designed spherical warm shield cannot only achieve F-number matching but suppress stray radiation sufficiently. Besides, it is demonstrated that the theory of spherical warm shield design developed in this paper is valid and can be employed by arbitrary infrared imaging systems. |
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| Keywords: | Spherical warm shield Infrared imaging system Stray radiation Radiometric calibration |
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