基于液晶光栅的大视场红外凝视成像系统设计

A large field of view infrared staring imaging system based on liquid crystal grating

分视场成像的中波红外凝视成像系统为解决红外光学系统很难同时满足大视场、高分辨率的问题,将多个子视场分时成像于同一个探测器中,然而目前该系统还存在着无法实现无缝拼接和液晶快门阵列结构复杂的缺点。本文在此基础上提出了一种新的基于液晶光栅的大视场中波红外凝视成像系统设计。通过在一次像面处加入矩形视场光阑并将其后移,使原有的0.28°的视场缺失减小至0°,实现图像的无缝拼接。快门阵列采用双光栅快门结构,使其无需复杂的位置关系,并将液晶快门阵列放置于平行光路中,可消除其所引入的色差与偏振带来的主光线间纵向位移影响。采用所提出的方法,设计出了F数为3.25,焦距为130 mm,波长范围为4.25~4.75μm,全视场对角线为10.8°的红外凝视成像系统,其各子视场单元MTF均为0.3@30 lp/mm以上。最终通过仿真结果表明,该系统具有分视场成像的功能,且成像质量良好。

To solve the problem of difficulty for infrared optical systems to simultaneously meet the requirements of large field of view and high resolution.the mid wave infrared staring imaging system with split field of view imaging images multiple sub fields of view at different times in the same detector.However,the system still has the drawbacks of inability to achieve seamless splicing and complex structure of liquid crystal shutter arrays.On this basis,this article proposed a new design of a large field of view mid wave infrared staring imaging system based on liquid crystal polarization gratings.By adding a rectangular stop at the first image plane and moving it backwards,the original 0.28°field of view loss was reduced to 0°.It achieved seamless splicing.The shutter array adopted a dual grating shutter structure,which eliminates the need for complex positional relationships.The liquid crystal shutter array was placed in a parallel light path to eliminate the longitudinal displacement between the main light rays caused by chromatic aberration and polarization.Using the proposed method,a mid-wave infrared staring imaging system was designed with an F-number of 3.25,a focal length of 130 mm,a wavelength range of 4.25μm to 4.75μm,and a full field of view diagonal of 10.8°.The MTF of each sub field of view unit is above 0.3@30 lp/mm.The final simulation results show that the system has the function of split field imaging and fine imaging quality.