广角f-θ静态红外地平仪镜头的光学设计

为了满足航天器对轻小、价廉,性能可靠的自主导航系统的要求,设计了广角静态红外地平仪系统。该系统选择辐射稳定的14～16.25μm作为工作波段,并设定全视场角为136°,F数为0.61;采用反远距结构,使系统后工作距达到15mm;利用f-θ镜头设计原理,并合理地选用非球面对广角系统进行优化设计,使系统的线性特性的相对误差0.5%;在空间频率为15lp/mm处,系统的调制传递函数0.6,接近衍射极限;在半径为20μm的圆内,系统径向能量85%。另外,采用了像方远心光路,提高了像面的照度均匀性,实现了整个像面照度均匀性99%。设计结果表明,该镜头结构简单、体积小、后工作距大,很好地解决了广角镜头轴外像差平衡问题,实现了地平仪系统的高精度设计。

Optical design of high precision wide-angle lens for static infrared earth sensors

In order to meet the requirements of spacecrafts for autonomous navigation systems with light small,cheap and reliable performance,a wide-angle static infrared horizontal system was designed. The system chose the operating wavelength range of 14 to 16.25 μm to keep a stable radiation,and its full field of view was set as 136° and F number as 0.61. By using a retrofocus structure in image space,the back working distance has been 15 mm in the optical system. On the basis of the design principle of a f-θ lens, the aspheric surface was used to rationally optimize the wide-angle system,then the related error of linear characteristics of the f-θ len is less than 0.5%,and the modulated transfer function is higher than 0.6 at 15 lp/mm in the image plane(approaches diffraction limit). In a circle with radius of 20 μm,the radial energy is higher than 85%. Furthermore,a telecentric optical path was used in the system,which improves the relative illumination to more than 99%. These results show that the designed lens has the advantages of simplicity,compactness and long back working distance,and can balance the correctness of off-axis aberrations.