设计了由负轴棱锥、折射率匹配液、正轴棱锥组成的浸液式组合轴棱锥.理论分析表明: 浸液式组合轴棱锥系统与传统轴正棱锥等效, 同时可有效提高最大无衍射传输距离；系统产生的最大无衍射距离与负轴棱锥的底角、折射率, 匹配液的折射率, 正轴棱锥的底角和折射率这五个量有关, 极大地增加了系统设计的灵活性, 拓展了光学材料的选择范围, 降低了光学元件的加工难度.

A composite axicon is presented, which consists of a positive axicon and a negative axicon immersed in index-matching liquid. Analysis results show that it is equivalent to conventional positive axicon, and can be used to generate long-distance nondiffracting Bessel beam.The maximum distance without diffraction depends on not only the refractive index of axicons and index-matching liquid, but also the cut angle of axicons. Therefore, it is a flexible method which not only increases the selection of element material, but also reduces the difficulties of element processing.