本文提出用同轴不共焦抛物面——双曲面掠射系统,代替现在流行的同轴共焦系统。利用不共焦引入预定量的球差,可以抵消一部分轴外球差。与Wolter-I型(象面离焦)相比较,在0～15弧分视场内象质有显著改善,在15～20弧分视场象质相同。指出用MTF评价,可以比用线扩散函数或均方根弥散圆(rms)更准确地评价这类系统的象质。本文还讨论了光阑设置及望远镜口径尺寸公差计算方法。把口径误差表示为焦点与端面的相对位移,可以定量计算口径误差对象质的影响。计算结果与国外已发表的数据基本符合。镜面口径差的公差与圆度公差比口径公差的要求严格一个数量级以上,抛物面比双曲面的口径差的公差严格4～5倍。 In this paper, the coaxial non-confocal paraboloid-hyperboloid grazing system is proposed to replace the currently popular coaxial confocal system. The use of non-confocal introduction of a predetermined amount of spherical aberration can offset part of the axial spherical aberration. Compared with the Wolter-I type (defocusing of the image plane), the image quality is significantly improved in the 0-15 arc minutes field of view, with the same field of view in 15-20 arc minutes. It is pointed out that with the MTF evaluation, the image quality of such systems can be evaluated more accurately than with line spread functions or rms dispersions (rms). This article also discusses the diaphragm aperture and telescope aperture size tolerance calculation method. The caliber error is expressed as the relative displacement of the focal point and the end face, which can quantitatively calculate the influence of the caliber error object quality. The calculation results basically accord with the published data in foreign countries. The difference between the mirror surface diameter tolerance and the circularity tolerance is more than one order of magnitude more strict than the diameter tolerance, and the paraboloid is 4 to 5 times more strict than the tolerance of the hyperboloid diameter difference.