8倍双视场大相对孔径红外折/衍射系统设计

Design of 8× dual field of view zoom and large relative aperture infrared hybrid refractive-diffractive system

针对红外光电跟踪系统的研制要求,设计了一套8～12μm波段折/衍射混合型双视场变焦系统。该系统结构简单、相对孔径大、变倍比高,突破了以往红外变焦系统相对孔径小、变倍比小、结构复杂等缺陷;采用衍射元件的固有特性进行消色差及消热差设计,并利用锗与硫化锌的混合来校正系统色球差,其最终设计的相对孔径(即F数)为1.1,系统变倍比为8。设计结果表明,在空间频率18lp/mm处,-40～70℃温度范围内,宽视场及窄视场MTF均在0.55以上,接近衍射极限;在接受半径为15μm的探测器像元内,能量透过率大于78.5%,表明该系统具有良好的成像质量,在实际使用温度环境下实现了消热差设计。

A set of 8-12 μm infrared hybrid refractive-diffractive dual field of view zoom system was designed based on the triturating requirement of the photoelectric tracking system. The system broke through the flaw that the conventional system always had small relative aperture, small zoom ratio and complex structure. A simple dual field of view system with large relative aperture and high zoom ratio was designed. DOE was used to calibrate the chromatic aberration and temperature difference by its internal characteristics. Ge and ZnS were utilized to calibrate the spherochromatic aberration. The final designed result was that F# was 1.1（relative aperture）, and the zoom ratio is 8x. The result indicates that the MTF is above 0.55 abroad and narrow field of view which is at the spatial frequency of 18 lp/mm, and the MTF is approaching to the diffraction limit. The energy permeance ratio is greater than 78.5% when the system receiving radius in the detecting sensor is smaller than 15μm. It shows that the imaging quality of the zoom system is very good, and it calibrates the temperature difference in real circumstance of the application.