平面镜、凸透镜和凹透镜。

Plane mirrors, convex lens and concave lens.

正象双凸透镜可以放大那样，双凹透镜也可以缩小。

Just as a double convex lens enlarges so a double concave lens reduces.

目的：观察凹透镜和凸透镜对豚鼠眼球生长和屈光变化的影响，建立透镜诱导型屈光不正动物模型。

Objective: to observe the effect of concave and convex on growing and the refractive developing of guinea pig eyes and to establish lens-induced animal model of myopia or hyperopia.

该方法借助一个焦距较长的凸透镜与被测凹透镜组成无焦系统，可以使准直管出射光束的张角发生改变；

Firstly, a telescope system is made up with a concave lens and a long-focus convex lens, by which the angle of the parallel beam from the collimator can be change.