Lens illustrating article on receiver

摘要

The lens assembly (1-16) is used for radiology work. A first group of lenses on the long conjugation side have a negative index of refraction. There is a second group on the short conjugation side a positive index of refraction, and a stop is mounted between them. The second group of lenses comprises two partial groups of positive refraction, the one on the short-conjugation side sliding with the receiver for focussing. The first group comprises two or more lenses. The radial centre of the surface of the first group towards the stop, and that of the last face of the lens on the conjugation side are at the latter side. The dispersion of the lenses of the first group is alternatively high and low.