Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2000-06-16
2001-10-23
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000
Reexamination Certificate
active
06305800
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved single vision ophthalmic lens. The invention particularly relates to methods of surface correction to improve the optical performance of a single vision ophthalmic lens by reducing optical aberrations, such as those associated with power and astigmatic errors, together with lenses produced by such methods.
BACKGROUND OF THE INVENTION
Conventional single vision lenses do not adequately correct for optical aberrations apparent to the wearer when viewing objects, through the lens, at oblique angles. This results from the lens surfaces not being the ideal shape to fully correct for the wearer's specific needs of power, cylinder correction and fitting requirements for off-axis vision.
Attempts have been made to correct such errors in the prior art with limited success, and have most often resulted in compromises that either do not fully correct the entire lens surface or that inadequately address the optical aberrations and errors.
Typically, prior art attempts introduced corrections by aspherising one or both of the lens surfaces for spherical or toric corrections. For example, typical prior art methods have relied on aspherising the two principle toric meridians of the lens back surface, improving the optical performance of these meridians independent of each other. This method has proven to be deficient in that the regions between the two principle meridians are not sufficiently optically optimised in the same way as the vision along the principle meridians.
Other methods have typically included minimising astigmatism on a grid of points on the lens surface using optical ray tracing techniques, following which a twice continuously differentiable spline surface (satisfying the data at each point) is fitted. However, it is only possible to satisfy these conditions for a limited range of simple surfaces that cover only a fraction of all surfaces that are of interest to the ophthalmic industry. In other cases, such an approach normally requires the fitting of a smoothing spline surface in an attempt to approximate the calculated data at each point, without satisfying it exactly. As a result, the optics of such a surface often significantly deviates from the optimal case.
It is an object of the present invention to provide an improved single vision ophthalmic lens that overcomes the difficulties identified above with prior art single vision ophthalmic lenses.
SUMMARY OF THE INVENTION
The present invention provides an ophthalmic lens element having a first surface and an atoroidal or generally aspheric second surface. The second surface is described by a symmetric polynomial whose coefficients have been chosen to minimise a merit function constructed of the sum of a particular optical aberration over substantially the entire surface thereof.
The present invention also provides a method of designing an ophthalmic lens element having a first surface and an atoroidal or generally aspheric second surface. The method includes selecting a symmetric polynomial for the second surface, selecting a merit function relating to at least one optical aberration, minimising the merit function over the substantially entire surface thereof to generate a modified surface function, and shaping the second surface to the modified surface function.
It has been found that in order to reduce optical aberrations visible to wearers, it is necessary to apply the appropriate corrections over substantially the entire ophthalmic lens element, rather than just the two principle cylinder meridians. This has the beneficial effect of making a larger area of the lens surface to have tolerable levels of optical aberrations.
REFERENCES:
patent: 4195919 (1980-04-01), Shelton
patent: 5220359 (1993-06-01), Roffman
patent: 5715032 (1998-02-01), Isenberg
patent: 3622757 (1987-01-01), None
patent: 3729845 (1989-03-01), None
patent: 94/25887 (1994-11-01), None
Miller Anthony Dennis
Varnas Saulius Raymond
Burns Doane Swecker & Mathis L.L.P.
Sola International Holdings Ltd.
Sugarman Scott J.
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