Ross Homocentric Lens

Ross Homocentric lens F.6.5, 7 inch f.l. in a rigid mount with a ring type diaphragm, c. 1912. This lens can be regarded as a logical development from the Rapid Rectilinear lens. The lenses which previously were cemented together in the Rapid Rectilinear lens are now separated from one another and their order interchanged. The curves which had to be the same in the Rapid Rectilinear lens so that the glasses could be cemented together may now be different. Greater freedom is allowed to the designer and advantage has been taken of this to produce an anastigmat with a vastly better field curve and astigmatism correction than that of a Rapid Rectilinear lens, while at the same time a comparatively small amount of zonal spherical aberration remains in the lens.