The principle of secondary spectrum is introduced and the equations of designing apochromatism objective lens based on wave aberration are presented.

介绍了二级光谱基本原,给出了波差法设计复消色差物方程组。

A physiotherapeutic apparatus for preventing and treating near sighted eye has a convex lens used as objective lens, lens cone, eyepiece, headgear and lens set.

一种防治视眼器，它有作为物凸透、筒、目，还有头套和透组，它用于人们在上长时间用眼时戴在眼上，可以使被视物像清楚、放大和变远。