Progressive refractive power lens

• US 20050099596A1
• Filed: 02/17/2004
• Published: 05/12/2005
• Est. Priority Date: 02/19/2003
• Status: Active Grant

• Current Assignee: Hoya Lens Manufacturing Philippines, Inc. (Hoya Corporation)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kato, Kazutoshi
• Granted Patent: US 7,159,981 B2
• Time in Patent Office: Days
• US Class Current: 351/168
• CPC Class Codes: G02C 7/061 Spectacle lenses with progressively varying focal power
• CPC Class Codes: G02C 7/068 Special properties achieved by the combination of the front and back surfaces

Abstract

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.

Claims

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 C1 at a distance reference point of the object-side refractive surface and a curvature C2 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 C3 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 or 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.

6. A progressive-power lens as set forth in any one of claims 1 through 5, 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 anyone of claims 1 through 6, characterized in that curvature variation Δ

C1 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

C1≦

0.25/(n−

1)

wherein n indicates a refractive index of a lens base material.

8. A progressive-power lens as set forth in anyone of claims 1 through 7, characterized in that curvature variation Δ

C2 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;

Δ

C2≦

0.25/(n−

1)

wherein n indicates a refractive index of a lens base material.