Deviation of Zone Lenses Produced by Polarization

Abstract

ZONE lenses are systems of alternate opaque or phase-retarding rings, which are usually made in one of the following ways: (a) by describing larger circles on cardboard and photographically reproducing them, (b) by photographing Newton fringes occurring between a slightly convex lens and an optical flat, or (c) following Wood¹, but cutting out narrow ring circles on a previously coated surface by means of a turntable or lathe. The least distance, (d), resolved by a zone lens is given by: where λ is the wave-length and B the focal length/diameter. Since the focal length is proportional to the square of the radius of the innermost zone², small zone lenses will have higher resolving power. Thus, the originals made are usually further reduced photographically in one or two subsequent steps.