Progressive-power lens
An eye-side refractive surface 11 of a distance portion is concave and at least part of an eye-side refractive surface 3 of a near portion is a convex region 31 where one or both of principal meridians of the surface are convex. This provides a back surface progressive-power lens capable of solving disadvantages in terms of lens thickness, external appearance and the like in a back surface progressive-power lens in which the eye-side refractive surface is formed of a progressive-power surface.
1. A progressive-power lens comprising:
an object-side refractive surface; and
an eye-side refractive surface, the eye-side refractive surface including:
a distance portion having a power to view distant objects;
a near portion having a power to view near objects; and
an intermediate portion between the distance portion and the near portion,
wherein the distance portion is concave,
wherein at least a part of the near portion is a convex region,
wherein the eye-side refractive surface includes an aspherical surface to correct astigmatism due to the convex region, and
wherein a ratio of a surface area of the convex region within a circle to a surface area of the circle is less than or equal to 30%, the circle having a radius of 25 mm for a geometrical center of the progressive-power lens.
2. The progressive-power lens according to claim 1 , wherein an absolute value of maximum surface power of a principal meridian of the convex region is not greater than 2 dioptres.
3. The progressive-power lens according to claim 2 , wherein the absolute value is not greater than 1.5 dioptres.
4. The progressive-power lens according to claim 1 , wherein the ratio is less than or equal to 20%.
5. The progressive-power lens according to claim 1 , wherein the ratio is less than or equal to 15%.
6. The progressive-power lens according to claim 1 , wherein the object-side refractive surface is a spherical surface or a rotationally-symmetric aspherical surface.
7. The progressive-power lens according to claim 1 , wherein the eye-side refractive surface includes a cylindrical power.
8. The progressive-power lens according to claim 1 , wherein the eye-side refractive surface includes a prismatic power.
9. The progressive-power lens according to claim 1 , wherein the progressive power lens is in a meniscus shape.
10. The progressive-power lens according to claim 1 , wherein the distance between the distance portion and the near portion is 10 mm˜16 mm.
11. The progressive-power lens according to claim 1 , wherein the distance between the distance portion and the near portion is 19 mm˜25 mm.
12. A progressive-power lens comprising:
an object-side refractive surface; and
an eye-side refractive surface, the eye-side refractive surface including:
a distance portion having a power to view distant objects;
a near portion having a power to view near objects; and
an intermediate portion between the distance portion and the near portion,
wherein the distance portion is concave,
wherein at least a part of the near portion is a convex region,
wherein the eye-side refractive surface includes an aspherical surface to correct astigmatism due to the convex region, and
wherein the distance between the distance portion and the near portion is 19 mm˜25 mm.