双视场长波红外光学系统无热化设计

Athermalization Design of Dual-Field-of-View Long Wavelength Infrared Optical System

介绍了凝视面阵双视场长波红外光学系统设计及无热化技术。采用两种不同的光学构型实现视场切换,第一种方案通过轴向移动一组透镜实现视场切换,第二种方案通过旋转变倍插入镜组实现视场切换,对比了它们各自的优缺点。研究发现旋转变倍光学系统光学性能优于轴向两档变倍光学性能,但不适合采用光学被动式无热化设计;两档变倍光学系统在小变倍比的情况下(倍率小于4),各项光学性能良好,且较容易采用光学被动式无热化设计,实现轻量化小型化设计。设计中引入非球面降低系统残余像差,减少了镜组个数,降低了系统成本。光学系统工作波段为7.7～9.7μm,结构紧凑,可达到100%冷光阑效率,像质评定结果表明,光学系统双视场在全温度范围内(-60℃～70℃)像质良好。

An athermalization design of switchable dual-field-of-view optical systems for 8～12 μm wavelength band using infrared focal-plane array （FPA） is presented. In order to switch the field-of-view （FOV）, two different optical configurations are explored and compared. The first scheme is based on the axial motion of a lens group and the second is based on a rotate-in motion of two widely separated lens groups. It is found that the rotate-in scheme achieves better performance than the step-zoom scheme, but the optical passive athermalization misfits this scheme. The step-zoom scheme is easy to use the optical passive athermalization to achieve lighter weight and smaller volume, and the performance is well for small zoom ratio. Aspheric surfaces are utilized to control aberrations and reduce the total lens cost. The results show that the optical system in the 7.7～9.7 μm wavelength band has a compact structure and can achieve 100% cold shield efficiency. The final optical designs along with their modulation transfer function （MTF） are presented, showing excellent imaging performance in dual FOVs at the temperature range between -60 ℃ and 70 ℃.