Design of MWIR step-zoom detection imaging system with a large FPA

For novel cooled 640×512 large focal plane array staring focal plane array (FPA) infrared detector with the picture clement size of 15 μm×15 μm,a mid-wave infrared step-zoom detection imaging system with a large FPA was presented in the paper.The manner of variational fov was accomplished by switching two lenses into the narrow fov system layout with mechanism framework.The parameters of the novel system are 4.0 f/number, 800mm/400mm effective focal length (EFL) and 3.7-4.8 μm spectrum region，100% cold shield efficiency.Image quality and thermal Analysis was evaluated by Code-v optical design software.At the spatial frequency 33lp/mm,the Modulation Transfer Function(MTF) was above 0.15 both the long EFL and short EFL in the working temperature range -35°C～55°C.