Back-surface progressive power lens
First Claim
1. A progressive power lens having a negative dioptric power for distance vision, wherein a progressive surface is formed on the back surface of said progressive power lens;
- wherein the value of a surface power Pfm of said progressive surface in the main meridional plane at a first point on the main meridian in a distance portion of said progressive power lens is less than the value of a surface power Pfs of said progressive surface in a plane perpendicular to said main meridional plane at said first point (Pfm<
Pfs);
wherein the value of a surface power Pnm of said progressive surface in said main meridional plane at a second point on said main meridian in a near portion of said progressive power lens is greater than the value of a surface power Pns of said progressive surface in a plane perpendicular to said main meridional plane at said second point (Pnm>
Pns); and
wherein said surface power P is defined by the following condition;
4 Assignments
0 Petitions
Accused Products
Abstract
A back-surface progressive power lens is provided having a negative dioptric power for distance vision, the value of a surface power Pfm of the progressive surface in the main meridional plane at a first point on the main meridian in a distance portion of the progressive power lens is less than the value of a surface power Pfs of the progressive surface in a plane perpendicular to the main meridional plane at the first point; and the value of a surface power Pnm of the progressive surface in the main meridional plane at a second point on the main meridian in a near portion of the progressive power lens is greater than the value of a surface power Pns of the progressive surface in a plane perpendicular to the main meridional plane at the second point. The surface power P is defined by the following condition: P=(n−1)/r; wherein “n” represents the refractive index of the progressive power lens, and “r” represents the radius of curvature at one of the first point and the second point on the main meridian in the near portion and the distance portion, respectively.
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Citations
7 Claims
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1. A progressive power lens having a negative dioptric power for distance vision, wherein a progressive surface is formed on the back surface of said progressive power lens;
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wherein the value of a surface power Pfm of said progressive surface in the main meridional plane at a first point on the main meridian in a distance portion of said progressive power lens is less than the value of a surface power Pfs of said progressive surface in a plane perpendicular to said main meridional plane at said first point (Pfm<
Pfs);
wherein the value of a surface power Pnm of said progressive surface in said main meridional plane at a second point on said main meridian in a near portion of said progressive power lens is greater than the value of a surface power Pns of said progressive surface in a plane perpendicular to said main meridional plane at said second point (Pnm>
Pns); and
wherein said surface power P is defined by the following condition;
- View Dependent Claims (2, 3, 4, 5, 6)
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7. A progressive power lens having a negative dioptric power for distance vision, wherein a progressive surface is formed on the back surface of said progressive power lens;
wherein a surface power Pm of said progressive surface in the main meridional plane at a point on the main meridian and a surface power Ps of said progressive surface in a plane perpendicular to said main meridional plane at said point on said main meridian satisfy the following condition;
Specification