折/衍混合凝视型红外地平仪系统的无热化设计

Athermal Optical Design of Refractive/Diffractive Staring Infrared Earth Sensor System

为了满足地平仪系统轻小、廉价、性能可靠的要求,设计了折/衍混合无热化凝视型红外地平仪系统。利用衍射元件特殊的像差特性和热差特性,采用折/衍混合广角f-θ镜头结构对地平仪系统进行大视场像差、色差和热差校正,采用反远距结构,保证系统具有足够的后工作距。设计结果表明,在温度为20℃时,140°广角f-θ镜头的线性特性小于0.5%;在-20℃～40℃温度变化范围内,空间频率20lp/mm处光学系统的调制传递函数均大于0.52,光学系统的波像差均小于λ/4,系统设计接近衍射极限满足成像要求,优化设计后光学系统的后工作距离为15mm,满足红外光学系统的装配需求。

An athermal optical design of a refractive/diffractive static infrared earth sensor, which meets the requirements such as portability, cheapness and reliability, is presented. The optical system has a wide-angle f-θ structure with a diffractive element introduced, which is beneficial to the correction of the monochromatic, chromatic and athermal aberrations. The inverse telephoto structure is adopted to achieve enough back-working distance. It is shown for the designed optical system that the f-θ linearity is less than 0.5 % at 20 ℃, the field of view is 140°, the modulation transfer functions are greater than 0.52 at the spatial frequency of 20 lp/mm in the temperature range from -20 ℃ to 40 ℃ and the wave-front aberration is less than λ/4 for all situations, with a satisfactory back-working distance of 15 mm. These meet the requirements in the actual applications.