Athermalization Of Infrared Dual-band Dual Field Optical System

The development of infrared imaging system is inseparable from the advancement of optical materials and the continuous improvement of detector.With the single-core and single-band infrared detection approaching the imaging limit,composite optical systems with multi-band and multi-field have gained more attention in the fields of aerospace and defense.The emergence of two-color detectors and wide-spectrum transflective materials has made it possible to reduce the weight of infrared composite detection systems.The infrared dual-band athermalized optical system not only meets the application requirements for dual-band detection,dual-field search and tracking,but satisfies the need of heat-dissipation difference under different temperature conditions,ensuring the recognition speed and recognition ability of the system.At the same time,it can work stably in a wide temperature range.The optical structure of the integrated common optical path and the optical passive athermalization can effectively reduce the weight of the photoelectric load and the size of the device,which is of great significance for the development of the aeronautical optical instrument.Aiming at the non-thermal design of the infrared dual-band variable-magnification system,this paper proposes an optical scheme using an integrated common optical path to establish a secondary imaging structure.The dual-field zoom is located in the front optical path,and adopts a switching structure.The initial system optical path is optimized by two folds to establish a temperature-based multiple structure,and the dual-band dual-field non-thermal design is implemented,and provides excellent imaging performance between-40°C and 60°C.The main research contents of the paper are as follows:(1)The development history,research background and significance of the infrared dual-band athermalized optical system are introduced.The relevant research cases at home and abroad are investigated,and their advantages and disadvantages are compared.The key characteristics of infrared materials are summarized.The influence mechanism of temperature on the refractive index,curvature,medium thickness,lens spacing and aspheric coefficient of optical media is analyzed.(2)The structure type of optical systems are analyzed,and the advantages and disadvantages among the the split aperture,the common aperture and the integrated common optical path are compared,and the moving zoom and switching zoom modes are introduced for the best application scenario.Based on these comparative analyses,a design scheme of infrared dual-band athermalized optical system is proposed,which using integrated common optical path and fast switching zoom.The power distribution of the initial structure of the system is derived and the optical model of the system is preliminarily established.(3)According to the basic theory of optical passive athermalization,several mathematical models of the athermal structure of the optical structure are established.The athermal T-C diagram is established according to the form of the solution,which guides the establishment and optimization of the athermalized optical system.Aiming at dual-band athermalized close-contact system model,the material selection scheme and the power distribution value are given.(4)Using the optical design software Code-V,the simulation optimization environment of the initial optical system is established,and the multiple structures of the optical system under different temperature conditions are established in different fields of view.When uniformly optimized,it can maintain same focal length and ideal image quality between-40°C and 60°C.The simulated ray tracing is performed on the finally optimized optical system.And the optical surface of the infrared refrigerating optical system which is easy to generate cold reflection and ghost image is further optimized and adjusted to suppress the generation of stray light.The imaging capability of the established system and the optical axis accuracy of the switching zoom group are analyzed,and the results meet the requirements for use.