Design Of The Dual FOV IR Optical System With Hybrid Refractive/Diffractive

With the advantages of good adaptability to environment, easy to conceal, strong anti-interference ability, and identifying camouflage target to a certain extent, infrared imaging systems have been applied to the infrared night-vision, infrared reconnaissance and infrared guidance in the military field widely. The demand for infrared system is increasing and the requirements are improving, which promoted the development of infrared zoom system objectively. According to whether the focal length changes continuously or not in zooming process, the IR zoom system consists of continuous zoom system, dual field, and three-field-of-view, etc. Compared with the continuous varifocal optical system, DFOV optical system has the advantages of small radial dimensions, fast switching speed, good imaging quality and simplicity to assemble, etc. It achieves searching goals at wide FOV and observing goals at narrow FOV. On the other side, because of the high cost of infrared materials and the low transmission ratio when using too many lenses, diffractive optical elements (DOE) are introduced into the traditional optical system with multiple fields of views, which simplified the system and well corrected the chromatic aberration . So it's significant to study an IR DFOV optical system with hybrid refractive / diffractive, good imaging and lightweight.In this paper, the author firstly introduced the development of IR varifocal optical system with hybrid refractive / diffractive at home and abroad, and then put forward the hybrid refractive / diffractive and re-imaging optical structure after analyzing the key points for IR optical system. Then based on the diffraction efficiency, the analysis of influence resulting from machining tolerance was studied as DOE design criterion. In order to acquire the initial structure parameters for DFOV optical system the Gaussian theoretical operations of the zoom system were also discussed. Then according to the design requirements, a lightweight mid-IR DFOV optical system was designed with hybrid refractive / diffractive, and the optimization process was stated, and the image quality was also evaluated, while the narcissus intensity ratio and the thermometric accuracy were analyzed, and finally the working distance of IR optical system was estimated. At last three compensating methods of athermalization technology for IR optical system were studied, and a comparison of their advantages and disadvantages were also made respectively, finally adopting the positive athermalization technology according to specified technical requirements and the temperature compensation curves were showed out.