Back-surface progressive power lens

• US 6,186,627 B1
• Filed: 12/02/1999
• Issued: 02/13/2001
• Est. Priority Date: 12/03/1998
• Status: Expired due to Term

• Current Assignee: Hoya Lens Thailand Limited (Hoya Corporation)
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Obara, Yoshimi
• Primary Examiner(s): Sugarman, Scott J.
• Application Number:
  US09/453,036
• Time in Patent Office: 439 Days
• Field of Search: 351/168, 351/169, 351/170, 351/171, 351/172, 351/177
• US Class Current: 351/169
• CPC Class Codes: G02C 7/061 Spectacle lenses with progressively varying focal power
• CPC Class Codes: G02C 7/065 Properties on the principal line
• CPC Class Codes: G02C 7/068 Special properties achieved by the combination of the front and back surfaces

Abstract

A back-surface progressive power lens is provided having a negative dioptric power for distance vision, the value of a surface power Pf_m 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 Pf_s of the progressive surface in a plane perpendicular to the main meridional plane at the first point; and the value of a surface power Pn_m 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 Pn_s 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.

Claims

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 Pf_m 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 Pf_s of said progressive surface in a plane perpendicular to said main meridional plane at said first point (Pf_m<

Pf_s);

wherein the value of a surface power Pn_m 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 Pn_s of said progressive surface in a plane perpendicular to said main meridional plane at said second point (Pn_m>

Pn_s); and

wherein said surface power P is defined by the following condition;

2. The progressive power lens according to claim 1, wherein the value of said surface power P_m is identical to the value of said surface power P_s at a point in the close vicinity of a specific point on said main meridian at which there is no prismatic power.

3. The progressive power lens according to claim 1, wherein the value S_Nof a dioptric power for near vision is negative (S_N<

0), and wherein the following relationship exists at a point within said near portion;

4. The progressive power lens according to claim 1, wherein the value S_N of a dioptric power for near vision is greater than or equal to zero (S_N≧

0), and wherein the following relationship exists at a point within said near portion;

5. The progressive power lens according to claim 1, wherein the value S_F of a dioptric power for distance vision is defined by the following condition:

6. The progressive power lens according to claim 1, wherein the value S_F of a dioptric power for distance vision is defined by the following condition:

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 P_m of said progressive surface in the main meridional plane at a point on the main meridian and a surface power P_s of said progressive surface in a plane perpendicular to said main meridional plane at said point on said main meridian satisfy the following condition;