随着航空航天遥感相机的分辨率及视场要求的不断提高，离轴四反光学系统受到越来越多的关注。而传统设计方法在离轴系统方面逐渐显示出局限性，因此引入了一种新型的设计方法—微分方程设计方法。首先介绍了微分方程设计方法的原理及设计思路，并加入焦距约束因素，创新性地提出同轴四反光学系统模型；并根据微分方程方法设计了一款焦距为100 mm、弧矢方向视场角为40°，子午方向视场角为10°的大视场离轴四反射镜光学系统，该系统在50 lp/mm 处的调制传递函数(MTF)均在0.606 以上。经过实验验证，与传统的设计方法相比，微分方程设计方法不但计算简洁、有效，而且在离轴系统的结构参数计算及面型计算方面有广泛的应用前景。

With the improvement of requirements in resolution and system′s viewing about aerospace remote camera, off-axis four mirrors optical system has attracted more and more attention. Traditional design method in the off-axis system is gradually reaching its limitations. Therefore, a new design method based on differential equations is presented. Firstly, it introduces the principle and design idea of this design method by differential equations, and the restriction factor of the focal length, then an innovative coaxial four mirrors model is put forward. Finally, according to the differential equations method, a large field of view off-axis four mirrors optical system is designed, in which focal length is 100 mm, the field angle in sagittal direction is 40°, the field angle in meridian direction is 10°, the modulation transfer function (MTF) is above 0.606 at the 50 lp/mm. By experimental verification, the design method of differential equations is not only simple and effective in computation, but which also has a wide application prospect in the calculation of structure parameters of off-axis system and surface calculation.