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US4950057A
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Progressive multi-focal ophthalmic lens
Assignee: Pentax Corp
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Filing: 1989-12-20
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Granted: 1990-08-21
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Expires: 2009-12-20
Abstract
Abstract A progressive multi-focal ophthalmic lens having a front refracting surface and a rear refracting surface one of which is a progressive surface whose refractive power changes continuously with the other being a non-progressive surface. The progressive surface is formed as a Fresnel lens surface composed of microscopic steps so that the macroscopic shape of the progressive surface generally conforms to that of the non-progressive surface.
Inventors
- 👤 Moriyasu Shirayanagi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:06
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/18; G02B5/1876; G02B5/189; G02B5/1895; G02C; G02C7/00; G02C7/02; G02C7/06; G02C7/061; G02C2202/00; G02C2202/20
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
69 words
In a progressive multi-focal ophthalmic lens having a front refracting surface and a rear refracting surface one of which is a progressive surface whose refractive power changes continuously with the other being a non-progressive surface, the improvement wherein said progressive surface is formed as a Fresnel lens surface composed of microscopic steps so that the macroscopic shape of said progressive surface generally conforms to that of said non-progressive surface.
Claim 2
Dependent Claim
69 words
In a progressive multi-focal ophthalmic lens having a front refracting surface and a rear refracting surface one of which is a progressive surface whose refractive power changes continuously with the other being a non-progressive surface, the improvement wherein said progressive surface is formed as a Fresnel lens surface composed of microscopic steps so that the macroscopic shape of said progressive surface generally conforms to that of said non-progressive surface.
Claim 3
Dependent Claim
23 words
A progressive multi-focal ophthalmic lens according to claim 1 wherein said front refracting surface is progressive and said rear refracting surface is non-progressive.
Claim 4
Dependent Claim
23 words
A progressive multi-focal ophthalmic lens according to claim 1 wherein said front refracting surface is non-progressive and said rear refracting surface is progressive.
Claim 5
Dependent Claim
81 words
A progressive multi-focal ophthalmic lens according to claim 1 wherein said Fresnel lens surface has a macroscopic shape expressed by: ##EQU12## assuming an orthogonal coordinate system, with the central axis of the lens as the x-axis, and the y- and z-axes being perpendicular to the x-axis and crossing each other at right angles in a plane tangent to said Fresnel lens surface, where Fm is a Fresnel coefficient, and X 0 is expressed by: ##EQU13## where An is an asphericity coefficient.
Claim 6
Dependent Claim
51 words
A progressive multi-focal ophthalmic lens according to claim 4 wherein X 1 is approximately equal to: ##EQU14## where R 1 is the radius of curvature of the Fresnel lens surface, and the non-progressive surface has an x-coordinate expressed by: ##EQU15## where Tc is the thickness of the lens at its center.
Claim 7
Dependent Claim
11 words
A progressive multi-focal ophthalmic lens according to claim 5 wherein Lm=0.
Claim 8
Dependent Claim
73 words
A progressive multi-focal ophthalmic lens according to claim 4 whose refractive power is expressed by a spherical power S of +3.00 D and an addition power Add of 2.75 D and wherein X 1 is approximately equal to: ##EQU16## where R 1 is the radius of curvature of the Fresnel lens surface, and the non-progressive surface has an x-coordinate expressed by: ##EQU17## where Tc is the thickness of the lens at its center.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-08-20 | 1994-02-19 | 1994-08-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-08-20 | 1998-02-19 | 1998-08-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-08-20 | 2002-02-19 | 2002-08-21 | $7700.00 | Window Closed / Lapsed |