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

介绍了二级光谱的基本原理,给出了波差法设计复消色差物的方程组。

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.

一近视眼的理疗器，它有为物的凸透、筒、，有头套和透组，它用于人们在近距离上长时间用眼时戴在眼上，可以使被视物的像清楚、放大和变远。