Visible/Infrared Multi-Band Co-Aperture Zoom System Design

The visible light system and the infrared system have different working bands,the visible light system and the infrared system detect the target characteristic information is not consistent,which can not meet the modern photoelectric detection and imaging system for target detection and recognition requirements.The fusion of visible light system and infrared system has a good complementarity.In addition,the zoom system can realize large field of view detection and small field of view recognition and tracking.The fusion of visible and infrared multi-band systems with zoom systems is an important research direction in recent years.In order to satisfy the requirements of modern optical imaging system and identify small vehicles in the range of 1～10km,a visible light,medium wave and long wave three-band co-aperture zoom system is designed in this paper which based on the reflectivity structure.The main research contents are as follows:(1)Three ways of fusion of visible light system and infrared system and four types of zoom system are analyzed.Zemax software is used to simulate the visible light,medium wave and long wave three-band common aperture zoom system.Among them,the optical imaging device of visible light system has working wavelength of 0.48～0.65μm,focal length range of 47mm-470mm,target surface resolution ratio of 1280×1024,pixel size of 4.7μm,and infrared system has working wavelength of 3～5μm and 8～10μm,focal length of 62.5mm～625mm,target surface resolution ratio of 320×240,pixel size of 25μm.(2)The optical transfer function curve(MTF),spot diagram,field curve and distortion of the visible light,medium wave and long-wave infrared three-band co-aperture zoom system were simulated and analyzed by Zemax software,and the zoom curve of the system was fitted by Matlab software.The results show that the MTF curves of visible light are all higher than 0.35 at the Nyquist frequency of 1061p/mm,the MTF curves of mid-wave infrared are all higher than 0.4 at the Nyquist frequency of 201p/mm,and the MTF curves of long-wave infrared are all higher than 0.5 at the Nyquist frequency of 201p/mm,and the maximum root mean square spot radius is 36.927μm.The field curvature and distortion of the system are well corrected,and the zoom curve of the system is smooth and has no inflection point,which meets the design requirements.(3)An optical passive compensating thermal desorption technique is used to design the medium wave and long wave infrared systems in the temperature range of-40℃～60℃.The MTF curves of the mid-wave infrared system were all higher than 0.35,and the MTF curves of the long-wave infrared system are all higher than 0.37 after athermalization,and the MTF curves of the system do not decrease significantly after the athermalization design,indicating that the system has a good effect of non-thermal design.(4)The tolerance of the system is analyzed by the sensitivity method.The results show that the MTF curves of the visible light system are all higher than 0.32 when the Nyquist frequency is 1061p/mm.MTF curves of the mid-wave infrared system are all higher than 0.4.The MTF curve values of the long-wave infrared system are all higher than 0.52,and the MTF curve values of the system in each band do not change significantly,indicating that the tolerance distribution of the system is reasonable.