针对大口径、长焦距、宽视场平行光管高像质的应用需求，提出一种采用离轴三反射镜结构的平行光管。从共轴三反理论出发，推导出系统的初始结构；并且在用zemax软件优化时，提出一种基于ZPL语言优化离轴量的方法。设计出一个焦距10 m，视场2°×1°的离轴三反平行光管。设计结果表明，系统像质接近衍射极限，全视场波像差RMS值优于λ/200(λ=632.8 nm)，系统总长度小于f′/3，为大口径、长焦距、宽视场光管设计提供了一种设计方法。

For the application demand of high image quality collimator with large diameter, long focal length and wide field, an off-axis three-mirror configuration for the light collimator was proposed. Based on the coaxial three-mirror configuration theories, the computation of the initial structure of the system was dervied, and a method of optimizing the off-axis amount was put forward by using the ZPL language of zemax software. A wide field off-axis three-mirror light tubes was designed, with focal length of 10 m, F-number of 28.57. Results show that the modulation transfer function of this system is near the diffraction limit, within the field 2°×1°, the full field wave-front aberration is less than λ/200(λ=632.8 nm), the total length of the system is less than f ′/3, providing a possibility design of long focal length, large diameter, and wide field of view light collimator.