Progressive power lens

• US 5,719,657 A
• Filed: 03/13/1997
• Issued: 02/17/1998
• Est. Priority Date: 11/19/1993
• Status: Expired due to Term

• Current Assignee: Seiko Optical Products Kabushiki Kaisha
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Izawa, Yasunori, Shirayanagi, Moriyasu
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US08/816,888
• Time in Patent Office: 341 Days
• Field of Search: 351/169, 351/168, 351/170, 351/171, 351/172
• 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

Abstract

A progressive power lens whose distance viewing vertex power is a negative value and in which a surface refractive power Pf_m in the main meridional plane in a distance viewing portion is larger than a surface refractive power Pf_s in a plane perpendicular to the main meridional plane (Pf_m >Pf_s). A surface refractive power Pn_m in a section in the main meridional plane in a near viewing portion is smaller than the surface refractive power Pn_s in a plane perpendicular to the main meridional plane (Pn_m <Pn_s).

Claims

1. A progressive power lens whose distance vertex power is negative,

wherein a surface refractive power Pf_m at a point along the main meridian in the main meridional plane in a distance viewing portion of said progressive power lens is larger than a surface refractive power Pf_s at the point along the main meridian in a plane perpendicular to said main meridional plane in a distance viewing portion,

wherein a surface refractive power Pn_m at a point along the main meridian in said main meridional plane in a near viewing portion of said progressive power lens is smaller than a surface refractive power Pn_s at the point along the main meridian in a plane perpendicular to said main meridional plane in a near viewing portion, and wherein said surface refractive powers Pf_m, Pf_s, Pn_m and Pn_s are determined in accordance with a shape of a surface of said progressive power lens.

2. A progressive power lens according to claim 1, wherein a value of a surface refractive power Pm in said main meridional plane is identical to a surface refractive power Ps in said plane perpendicular to said main meridional plane at a point proximate to a specific point on the main meridian at which there is no prismatic power.

3. A progressive power lens according to claim 1, wherein a near vertex power S_N is negative, and wherein the following relationship exists at a point within said near portion;

space="preserve" listing-type="equation">Pn.sub.m (-20)-Pn.sub.s (-20)<

-0.1

wherein

Pn_m (-20) represents a sectional surface refractive power at a point, on the main meridian, downward 20 mm from a prism reference point of said progressive power lens in said near portion, and,

Pn_s (-20) represents a sectional surface refractive power at a point along the main meridian, in a direction perpendicular to said main meridian, downward 20 mm from a prism reference point of said progressive power lens in said near portion.

4. A progressive power lens according to claim 1, wherein the near vertex power S_N is equal to or more than zero (S_N ≦

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

space="preserve" listing-type="equation">Pn.sub.m (-20)-Pn.sub.s (-20)<

-0.2

wherein

Pn_m (-20) represents a sectional surface refractive power at a point, on the main meridian, downward 20 mm from a prism reference point of said progressive power lens in said near portion, and,

Pn_s (-20) represents a sectional surface refractive power at a point along the main meredian, in a direction perpendicular to said main meridian, downward 20 mm from a prism reference point of said progressive power lens in said near portion.

5. A progressive power lens according to claim 1, wherein the distance vertex power S_F (D) is;

space="preserve" listing-type="equation">-2≦

S.sub.F ≦

0,

and wherein the following relationship exists at a point within the distance portion;

space="preserve" listing-type="equation">Pf.sub.m (15)-Pf.sub.s (15)>

0.1,

wherein

Pf_m (15) represents a sectional surface refractive power at a point, on the main meridian, upward 15 mm from a prism reference point of said progressive power lens in said distance portion, and,

Pf_s (15) represents a sectional surface refractive power at a point along the main meridian, in a direction perpendicular to said main meridian, upward 15 mm from a prism reference point of said progressive power lens in said distance portion.

6. A progressive power lens according to claim 1, wherein the distance vertex power S_F (D) is;

space="preserve" listing-type="equation">-6<

S.sub.F <

-2,

and wherein the following relationship exists at a point within the distance portion;

space="preserve" listing-type="equation">Pf.sub.m (15)-Pf.sub.s (15)>

0.2,

wherein

Pf_m (15) represents a sectional surface refractive power at a point, on the main meridian, upward 15 mm from a prism reference point of said progressive power lens in said distance portion, and,

Pf_s (15) represents a sectional surface refractive power at a point along the main meridian, in a direction perpendicular to said main meridian, upward 15 mm from a prism reference point of said progressive power lens in said distance portion.

7. A progressive power lens whose distance vertex power is negative,

wherein a surface refractive power P_m in a section of the main meridional plane, and a surface refractive power P_s in a section perpendicular to the main meridional plane satisfy the following relationship:

space="preserve" listing-type="equation">Δ

P(15)-=P(-20)>

0.3

wherein

space="preserve" listing-type="equation">Δ

P=Pm-Ps

wherein

Δ

P(15) represents a difference between sectional surface refractive powers Pm and Ps at a point upward 15 mm from a prism reference point of said progressive power lens, and,

Δ

P(-20) represents a difference between sectional surface refractive powers Pm and Ps at a point downward 20 mm from a prism reference point of said progressive power lens.