A negative lens provided with an annular perimetrical surface having a modified vergency and process to carry out same

摘要

A negative lens (110, 410) and particularly a lens to correct a very short-sightedness the rear face of which is . provided with a central spherical concave surface (12) and an annular perimetrical surface (112, 412), this latter being shaped differently from the former to modify its vergency either to remedy well known drawbacks of conventional negative lens or to correct also the long-sightedness of the myopic person who is wearing that negative lens.;The refraction defects of a myopic eye is in any case corrected by the suitable central concave surface (12). A consecutive annular perimetrical surface (112) is suitably shaped convexly in order that the modified vergency of same may eliminate or so attenuate the disagreeable appearance of concentric circles that these latter can hardly be seen by an observer. The rear face of negative lens (110) is in this case shaped as a continuous concave-convex surface.;When that consecutive annular perimetrical surface (412) is shaped again concavely with a bend radius suitably greater than said central concave surface, then the person who is wearing such a negative lens (410) may also correct his long-sightedness by turning his eyes therethrough. The rear face of negative lens (410 is in this case shaped as a continuous concave-concave surface.