长波红外广角地平仪镜头的光学设计

介绍适用于非致冷凝视式焦平面阵列的长波红外(LWIR)广角地平仪镜头的光学设计.其工作波长范围10～16μm,全视场角为135°.采用"负-正-正"型式的反远距像方远心光路镜头结构,仅有三块非球面锗透镜构成.能够很好地解决广角镜头轴外像差校正和像面照度均匀性问题.此镜头结构简单、体积很小、后工作距离大,成像质量接近于衍射极限,在20lp/mm空间频率处的调制传递函数值超过0.6,像高与视场角关系偏离线性的相对误差不超过15%.文中还分析了此镜头的加工和装调公差.

Optical design of a wide-angle lens for long-wave infrared earth sensors

This article describes the optical design of a wide-angle lens suitable for long-wave infrared (LWIR) earth sensor whose operating wavelength range is 10 to 16 microns, and full angle of view is up to 135 degrees, having an uncooled staring focal plane array. The optical system only consists of three germanium lenses with a "negative-positive-positive" reversed telephoto telecentric structure in the image space. This type of wide-angle lens can balance the correctness of off-axis aberrations against the evenness of illumination at its image plane very well. The designed lens has the advantages of simplicity, compactness and long back working distance. Its imaging quality is nearly diffraction limited, so that its modulated transfer function (MTF) value is higher than 0.6 at the 20 lines/mm spatial frequency in the image plane, and the relative error of the linearity between its image height and field angle is lower than 15%. Its manufacture and alignment tolerance are also analyzed with the CODE V optical design software.