Say we have a lens that has a spherical face on both sides, known as a convex lens.

假设我们有个具有球面的镜头 两侧，称为凸透镜。

This is made possible through something called a lenticular lens – a corrugated sheet in which each ridge is made up of a convex – or outward-curving – lens.

这是通过柱状透镜的东西实现的，柱状透镜是波纹状的板，其每个凸起处都由凸透镜（即向外弯曲的透镜）组。

There are instances in which towers were set up with a mirror inside of a dark room and sometimes with a convex lens in the aperture.

些情况下，人们会黑暗房间内设置带有镜子的塔楼，有时还会开口处安装凸透镜。

But the idea was that you would use a very large convex lens at the end, the object glass, not because That changes optical power, but because you're polishing only the very central part.

但想法是你会末端使用个非常大的凸透镜，即物镜， 不是因为这会改变光学功率，而是因为你只打磨中央部分。

And if you work it out, you would probably have a weak convex lens with about an 18-inch focal length in combination with a pretty strong concave lens with a focal length of about 6 inches.

如果你算下，你可能会得到个焦距大约为18英寸的弱凸透镜，与个焦距约为6英寸的强凹透镜组合。