Lens where the light rays obey the relation H=KFθ

Claim 1

A lens adapted to transmit an angularly varying beam of light originating from a point on the optical axis thereof and essentially at a focal point of said lens in a path parallel to the optical axis of said lens on the image side thereof, said lens having a predetermined focal length F, the angle between the incident beam and the optical axis of the lens being θ and the height of the image beam from the optical axis being H, said quantities bearing a relationship H = KFθ, said lens from the angularly varying light source consisting of a first bi-convex element and a second concave-convex element having its image side surface defined on a greater radius than its object surface and the axial spacing between said lenses on the optical axis being between two and ten percent of the equivalent focal length of the overall lens, and the curvature of the facing surfaces of the lens elements are equal to or greater than 0.30 of the equivalent focal length of said lens and equal to or less than 0.37 of the equivalent focal length of said lens, and K is approximately unity, the index of refraction of both of said lens elements referred to the D-line of sodium being greater than 1.6, whereby coma is introduced into said lens and said lens is taken out of the sine condition.