Progressive refractive power lens
It has been difficult to manufacture an inside surface progressive-power lens which is as thin as an outside surface progressive-power lens due to a limited configuration of an object-side refractive surface of the inside surface progressive-power lens. However, a thin progressive-power lens with less blur and distortion can be provided at a reduced cost by forming its object-side refractive surface from an aspherical surface which is symmetric with respect to a rotational axis and has a smaller curvature at a distance reference point than that at a near reference point, and by forming an eyeball-side refractive surface from a combination of a progressive surface, an astigmatic refraction surface and an “as-worn” corrective aspherical surface.
1. A progressive-power lens comprising a distance portion, a near portion and an intermediate portion, wherein an object-side refractive surface is formed from a part of an aspherical surface symmetric with respect to a rotational axis and an eyeball-side refractive surface is from a progressive surface; characterized in that there is a relationship shown below between a curvature C 1 at a distance reference point of the object-side refractive surface and a curvature C 2 at a near reference point of the object-side refractive surface:
C1<C2.
2. A progressive-power lens as set forth in claim 1 , characterized in that there is a relationship shown below as to a curvature C 3 at a portion outward from the near reference point of the object-side refractive surface:
C3<C2.
3. A progressive-power lens as set forth in claim 1 or 2 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an aspherical surface element for correcting “as-worn” optical characteristics is added.
4. A progressive-power lens as set forth in claim 3 , characterized in that the aspherical surface element for correcting the optical characteristics at the distance portion is different from that element at the near portion.
5. A progressive-power lens as set forth in claim 3 , characterized in that the aspherical surface element is established considering any one of a vertex distance at the wearing of glasses, a pantoscopic angle at the wearing of glasses and a working distance.
6. A progressive-power lens as set forth in claim 1 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an astigmatism-corrective element is added.
7. A progressive-power lens as set forth in claim 1 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
ΔC1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
8. A progressive-power lens as set forth in claim 1 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
9. A progressive-power lens as set forth in claim 4 , characterized in that the aspherical surface element is established considering any one of a vertex distance at the wearing of glasses, a pantoscopic angle at the wearing of glasses and a working distance.
10. A progressive-power lens as set forth in claim 2 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an astigmatism-corrective element is added.
11. A progressive-power lens as set forth in claim 3 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an astigmatism-corrective element is added.
12. A progressive-power lens as set forth in claim 4 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an astigmatism-corrective element is added.
13. A progressive-power lens as set forth in claim 5 , characterized in that the eyeball-side refractive surface is formed from a progressive surface to which an astigmatism-corrective element is added.
14. A progressive-power lens as set forth in claim 2 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
Δ C 1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
15. A progressive-power lens as set forth in claim 3 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
ΔC1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
16. A progressive-power lens as set forth in claim 4 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
ΔC1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
17. A progressive-power lens as set forth in claim 5 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
ΔC1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
18. A progressive-power lens as set forth in claim 6 , characterized in that curvature variation ΔC 1 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the distance reference point:
ΔC1≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
19. A progressive-power lens as set forth in claim 2 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
20. A progressive-power lens as set forth in claim 3 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
21. A progressive-power lens as set forth in claim 4 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
22. A progressive-power lens as set forth in claim 5 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
23. A progressive-power lens as set forth in claim 6 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.
24. A progressive-power lens as set forth in claim 7 , characterized in that curvature variation ΔC 2 of the object-side refractive surface satisfies a relationship shown below in a range of 5 mm in diameter from a center set at the near reference point:
ΔC2≦0.25/( n− 1)
wherein n indicates a refractive index of a lens base material.