Aplanatic lens

aplanatic

a. [物]等光程的,(透镜)消球差的

lens [lɛnz]

n. 透镜，镜头;眼睛中的水晶体;隐形眼镜;汽车的灯玻璃;

Absolutely.

绝对。

First come, first served.

捷足先登。

The only way that they can preserve their history is to recount it as sagas -- legends handed down from one generation of another.These legends are useful because they can tell us something about migrations of people who lived long ago, but none could wri

他们保存历史的唯一办法是将历史当作传说讲述，由讲述人一代接一代地将史实描述为传奇故事口传下来。