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折/衍混合红外双视场光学系统设计

Design of the Dual FOV IR Optical System with Hybrid Refractive/Diffractive

【作者】 唐大为

【导师】 王淑荣; 孙强;

【作者基本信息】 中国科学院研究生院(长春光学精密机械与物理研究所) , 光学工程, 2010, 硕士

【摘要】 红外成像系统具有环境适应性好、隐蔽性好、抗干扰能力强,以及能在一定程度上识别伪装目标等优点,其在军事上被广泛应用于红外夜视、红外侦察以及红外制导等方面。对于红外系统的需求日益增加,要求也不断提高,客观上促进了红外变焦系统发展。红外变焦光学系统按变焦过程中焦距是否连续变化分为连续变焦、两档变焦、三档变焦等。红外两档变倍光学系统相对连续变焦系统具有径向尺寸小、切换速度快、成像质量好、装配简单等特点,具备大视场搜索目标,小视场仔细观察目标的功能。另一方面,由于红外材料价格昂贵,同时系统透镜片数过多,会导致系统透射比下降,在这种情况下,衍射光学元件所具有的消色差、简化系统结构等优点,使得在传统红外多视场光学系统中引入衍射元件成为解决上述问题的有效途径。故而研究成像质量好、轻量化、折/衍混合的红外双视场系统设计具有重要的意义。本文介绍了衍射混合红外变焦系统的国内外发展情况,分析了中波红外系统的设计关键并在此基础上提出折/衍混合和二次成像的光学结构,并从衍射元件衍射效率出发,分析了加工公差对系统成像质量的影响,以此作为设计中使用衍射面的依据。同时阐述了变焦系统高斯理论运算,以此获得双视场光学系统的初始结构参数,然后根据设计要求,设计出了轻量化的折/衍混合的中波红外双视场系统,简述了设计过程,评价了系统的像质,并分析了系统冷反射强度和测温精度,估算出了红外系统的作用距离。最后研究了红外光学系统无热化技术中的三种温度补偿方式,分析了三种温度补偿方法的优缺点,并结合设计要求选取主动温度补偿方式,给出了系统温度补偿曲线。

【Abstract】 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.

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