US 4,315,673 AGranted

Progressive power ophthalmic lens

AssigneeOptische Werke G. Rodenstock

InventorsGunther Guilino, Rudolf Barth

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Abstract

In the disclosed lens, one lens surface is divided into an upper distance-vision portion FT, a lower near-vision portion NT, and a varying or transitional region PB between the two other portions. In the upper distance-vision portion, the surface contains a far reference point B.sub.F and exhibits predetermined average distance-vision surface refractive powers D.sub.F. The lower near-vision portion contains a near-vision reference point B.sub.N and has predetermined average near-vision surface refractive powers D.sub.N. The transitional region exhibits average surface refractive powers D.sub.P which effect a smooth transition from the distance-vision portion to the near-vision portion. The surface is divided into a temporal portion and a nasal portion by a principal meridian M which forms an umbilical line.

Claims20

Dependent claims

A lens for eyeglasses, comprising a surface having an upper distance vision portion FT containing a far reference point B.sub.F and given average distance-vision portion surface refractive powers D.sub.F, said surface having a lower near-vision portion NT containing a near reference point B.sub.N given average near-vision surface refractive powers D.sub.N, said surface having a progression region PB located between said distance portion FT and said near portion NT with average surface refractive powers D.sub.P which effect a smooth transition from said distance portion FT to said near portion NT, said surface being divided into a temporal portion and a nasal portion by a principal meridian M which forms an umbilical point line, characterized in that said surface fits the following equation in a cylindrical system of coordinates (y, .rho., .phi.):

##EQU12## wherein all a.sub.n (y) are chosen such that .rho.(0,y) is an umbilical point line and describes the curve f(y) of the principal meridan M,
k(y) is a function which monotonously ascends, preferably in the range of 3 to 10 from said near portion NT to said distance portion FT or is a number which is constant, preferably in the range of 3 to 10, over the entire surface, and the curve of the curvature of said principal meridian M ##EQU13## fits the equation
F(y)=A[1-(1+e.sup.-c(y+d)).sup.-m ]
wherein
A=D.sub.N -D.sub.F
and the numbers c, d, m are chosen so that said far reference point B.sub.F is located above a center point 0 of said surface, so that, above the far reference point B.sub.F, the average surface power D.sub.F along said principal meridian M is constant up to .+-.0.25 diopters, so that said near reference point B.sub.N is located below said center point 0 of said surface, and so that, below said near reference point B.sub.N, the average surface power D.sub.N along said principal meridian M is constant up to .+-.0.25 diopters.

3 more elements

##EQU40## wherein a.sub.n (y) for n>>2 equals zero and .rho.(.phi.,y) is an umbilical point line and the curve f(y) of the principal meridian (M) describes,
a.sub.o (y)=f(y)+g(y)/k.sup.2 (y)
a.sub.1 (y)=-g(y)/k.sup.2 (y) ##EQU41## and k(y) is a monotonously ascending function from the near portion (NT) to the distance portion (FT) or a number constant over the entire surface.

Dependencies are inferred from the claim text.