会聚透镜使光线会聚于一点，即焦点。

To adjust or come to a focus.

用一厚的简单会聚透镜很容易观察色差。

It's an easy matter to observe chromatic aberrations, with a thick, simple converging lens.

由数个照明单元加上会聚透镜则构成一个基本的照明系统。

Several such lighting units make a basic lighting system of projector.