基于自由曲面双波段离轴三反光学系统的优化设计

Optimal Design of Dual-Band Off-Axis Three-Reflection Optical System Based on Free-form Surface

在航空遥感领域中,双波段光学系统是最具代表性的光学系统。与单一波段光学系统相比,双波段系统可以同时探测到背景信号和目标信号,从而获得更准确的信息。采用离轴反射系统这一方案与折射系统相比,在满足更长焦距的同时,又能实现光学系统小型化的目标。本文提出一种基于自由曲面的反射系统作为设计蓝本,能够获得如下优点:视场角更大,光路容易折叠,系统成像质量高,能够达到高分辨率成像以及系统的轻量化设计。本文采用动态光学理论对系统初始结构进行求解并通过对系统元件的倾斜与偏移计算获得离轴系统,系统引入自由曲面获得更加优质的成像质量。系统参数如下:焦距为2000 mm,相对孔径为1/2,视场角为6°×1°,工作波段为3~5μm与8~12μm,选用法国Sofradir公司生产的红外双色焦平面阵列非制冷型探测器;设计结果表明,加入自由曲面后系统的成像质量得到了明显改善,系统在整个工作波段内MTF值在14 lp≥0.3。

In the field of aviation remote sensing,the two-band optical system is the most representative optical system.The dual-band system can detect both the background signal and the target signal to obtain more accurate information compared to a single-band system.Compared with the off-axial reflection system,the optical system is miniaturized while satisfying a longer focal length.Simultaneously,choosing the reflection system of a free surface as the blueprint of telefocal length system design has several advantages,including a large field of view angle,easy optical road folding,and a high system imaging quality,and can achieve high-resolution imaging and light weight design of the system.The system was added to the free-form surface for better image quality.The effective focal length of the system is 2000 mm,the relative aperture is 1/2,the field of view is 6°×1°,and the working bands are 3-5μm and 8-2μm.The selected model is the LA6110 non-refrigeration type detector.The design results show that the free-form surface can greatly improve the imaging quality of the system,and the modulation transfer function in the whole field of view can achieve a modulation transfer function greater than 0.3 at 14 lp/mm.