It is shown , through the analysis of their surface power and astigmatism , that the shape of the meridian line has significant influence upon the distributions of surface power and astigmatism . their keystone distortion is small . in this way , pal meeting different circumstances can be designed 最后，举例设计了光焦度增量为2 . 50m ~ ( - 1 )的几种渐变镜片，通过对设计结果分析研究，指出可得到梯形畸变较小的pal镜片，子午线光焦度渐增多项式参数的选取会影响镜片球面度和柱面度的大小和分布，由此，可设计满足不同使用要求的渐变镜片。
