A catadioptric magnifier with two magnifications for microfiche reading

We have considered the possibility of using four internal reflections in a single lens to reduce its effective focal length by a very large factor. Hence, by using very shallow curvatures on the lens surfaces, it is possible to obtain very high visual magnification for viewing transmission objects such as microfiche. Some details of such a system are presented here, where a lower magnification is obtained for two internal reflections and a higher magnification for four internal reflections.