非制冷长波红外热像仪折衍混合双视场光学系统设计

根据衍射光学元件具有大的负向色散特性,将衍射光学元件应用于红外双视场光学系统中,根据傅里叶光学分析衍射光学元件(DOE)的消色差,列表对比折射透镜与衍射光学透镜的特性,并给出变倍比为4∶1可用作非制冷红外热像仪的光学系统的具体设计实例.系统采用切入式变焦方式,在短焦时切入2片透镜实现宽视场,通过引入二元面和非球面提高了成像质量.设计结果表明:在空间频率11 lp/mm处,短焦距40 mm时,各个视场的MTF值均大于0.6;长焦距160 mm时,各个视场的MTF值均大于0.7,宽视场和窄视场都具有较好的成像质量.

Design of refractive/diffractive dual FOV optical system for uncooled LWIR thermal imager

Because of the large negative dispersive characteristic of diffractive optical elements, they are applied to infrared dual-FOV systems. The fundamental principle of chromatic aberration for diffractive optical elements is analyzed according to Fourier optics. The characteristic of refractive lens and diffractive optical lens is compared. A sample design of a optical system with zoom ratio 4∶1 which can be used in uncooled infrared thermal imager is presented. The manner of zoom is accomplished by exchanging two lenses into the wide FOV system configuration. The binary surface and aspheric surface is used to improve the image quality. The design result shows that when spatial frequency is 11lp/mm and the short focus is 40mm, the MTF value of each FOV is bigger then 0.6; when the long focus of 160mm, the MTF value of each FOV is bigger then 0.7; and both the wide-FOV and narrow-FOV have high image quality.