长焦距大变倍比中波红外变焦距系统设计

为实现红外连续变焦距系统变倍比大、焦距长和系统结构简单的需求,在光学系统中引入衍射元件(DOE),设计了一套3.7～4.8μm波段折/衍混合连续变焦光学系统。该系统突破了传统折射式中波红外变焦系统难以同时满足变倍比大、焦距长、系统结构简单等要求的局限,其变倍比为20×,可在35～700mm焦距范围内连续变焦,仅包含6片透镜和2片平面反射镜。在空间频率17lp/mm处,系统在全焦距范围内调制传递函数MTF>0.5;变焦过程中系统弥散斑直径均方根值小于20μm,表明该系统成像质量良好。

Design of long focal length large zoom ratio MWIR zoom optical system

In order to achieve the needs of high zoom ratio and long focal length with simple structure in infrared continuous zoom optical system,diffractive surface was employed in optical system.A hybrid refractive-diffractive zoom optical system working in 3.7-4.8 μm was designed,the system breaks through the limitations of traditional refractive zoom lens system which can not simultaneously satisfy the requirements of high zoom ratio,long focal length and simple structure.The zoom ratio of the system is 20×,and it can realize 35-700 mm continuous zoom.The optical system consists of zoom objective lens system and a re-imaging system,just including six lenses and two plane mirrors.The modulation transfer function(MTF) is above 0.5 in all focal distance at the spatial frequency of 17 lp/mm.The RMS of spot diameter is less than 20 μm in the zoom process,which proves that the image quality of the optical system is good.