Design Of Low-light And Infrared Fusion Common Aperture Optical System

Today’s battlefields have increasingly strict requirements for target detection and identification.However,battlefield camouflage has made target detection face more severe challenges.If only a single band of imaging is used,it cannot meet the needs of the battlefield.Low-light imaging and long-wave infrared imaging are complementary to each other.Dual-band fusion imaging technology has become an important direction for future development.First,this article explains two methods that can achieve dual-band imaging:dual-channel imaging and common-aperture imaging.Through a comparative analysis of the two methods,it is found that the common-aperture imaging system achieves low-light /infrared imaging for the same target in the same field of view,and the dual-band image formed by it is favorable for later image fusion.In order to meet the needs of battlefield use,this paper identifies vehicles 5km away and proposes a high-resolution common-aperture solution: in the front of the optical system adopts the Cassegrain system common-aperture design,and the light emitted by the detection target surface is reflected by the card reflection system.Then use the spectroscopic system to split the light and transmit the low-light and long-wave infrared to their respective optical path structures for imaging.Secondly,this paper makes a theoretical calculation of the technical parameters of the optical system.According to the selection of the optical system and the specific parameters of the detector,the basic parameters of the low-light optical system and the long-wave infrared optical system were calculated.After detailed calculations,the parameters of the optical system in this paper are as follows: the working range of the low-light optical system is 0.4 to 0.8 μm,the focal length is 164 mm,and the F / # is 4;the working wavelength of the long-wave infrared optical system is 8 to 12 μm,the focal length is 125 mm,F / # Is 3.1.Then,the optical design is performed according to the basic parameters of the optical system.The design results show that the MTF at the Nyquisy frequency of 28lp/mm in low-light optical system is greater than 0.5,and the MTF at the Nyquisy frequency of28lp/mm in long-wave infrared is greater than 0.2,which meets imaging requirements.For the long-wave infrared optical system,it adopts the athermal difference method of active electromechanical.So the system has good imaging quality in the operating temperature range.The rang of operating temperature is 40℃ to 60℃.Finally,this paper designs the mechanical structure of the completed optical system.The mechanical structure is divided into four parts: a common-aperture Cassegrain system,a spectroscopic system,a low-light imaging system,and an infrared imaging system.The mechanical structure has a focusing structure,which can achieve clear images of targets at different distances,and it can be processed and adjusted.