在光学系统中特别是反射系统中经常通过加无光焦度校正板来减少或消除其他元件所产生的像差。讨论了双贴合无光焦度校正板放在主镜前的双反射球面系统，根据像差理论分析了消像差的条件，研究了系统中各种参数的变化对系统高级残余像差的影响。结果表明主镜的相对孔径越大，系统的残余像差增加；正透镜在前的校正板结构优于负透镜在前的结构；选择合适的校正板单透镜的光焦度，可使系统的高级残余像差最小。

Zero-power correctors are often used to balance the aberrations caused by other components. A two-sphere system with a two-lens zero-power corrector placed before the primary mirror is discussed. According to third-order aberration theory,the conditions of the absence of aberrations are analyzed,and the influences of different system parameters to the remaining high order aberrations of the system are investigated. The results show that the bigger the relative aperture of the primary mirror,the bigger the remaining high order aberrations;the structure of the corrector with positive lens in front of the negative one is better than otherwise;and a suitable single lens' power may make the system the lowest aberrations.