Aspheric lenses

Details Aspheric lenses Aspheric lenses

2000-04-07

2001-01-23

Sugarman, Scott J. (Department: 2873)

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Ophthalmic lenses or blanks

C351S174000

Reexamination Certificate

active

06176577

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to ophthalmic spectacle lenses for distance vision correction.
Prescriptive ophthalmic lenses used for the correction of hypermetropia are positively-powered lenses, thicker at the center than at the edge. When conventional spherical ophthalmic lenses used for this correction increase in prescription strength, they become thick in the center. Lenses with a smaller diameter can be manufactured to a reduced center thickness. Lenses of this type can be manufactured to larger diameters and edged down to smaller diameters because the edging process does not affect center thickness. However, when the lenses are reduced in diameter by edging, the finished edge thickness increases as the diameter decreases. The increase can be determined by the difference in curvature between the anterior and posterior surfaces.
The appearance and the optical performance of the lens can be improved by providing an aspheric surface of revolution on the lens. This approach can be used to produce lenses to larger diameters. For example, M. Jalie, “The Principles of Ophthalmic Lenses”, Chapter 21, 4th Edition, London, The Association of British Dispensing Opticians (1988), describes the optical and cosmetic advantages achieved by lens designs in which one surface is aspheric (typically, but not necessarily, the anterior surface). It is generally desirable that optical performance not be sacrificed when a sphere, or a toroid when correcting for astigmatism, forms the posterior surface. It is also possible to prepare aspheric lenses in a semi-finished form (i.e., as oversized lens blanks), which can be fabricated to a final prescription using optical laboratory machinery.
Aspheric plus-power lenses for correction of hypermetropia that improve optical performance and cosmetic appearance can have spherical or toroidal posterior surfaces. Aspheric surfaces of revolution can be expressed as deformed spheroids, in which the departure from a sphere increases with the distance off-axis. For plus-power lenses (e.g., positive diopter lenses), this departure is in the direction of reduced curvature, below the constant curvature characteristic of spheroids, so that, for example, the center thicknesses of such lenses can be reduced. Examples using deformed spheroids include: lenses having distinct zones of differing curvature that are blended or smoothed in the regions connecting such zones (see, e.g., Bristol, U.S. Pat. No. 5,131,738); lenses having anterior surfaces expressed as surfaces of revolution of polynomials (see, e.g., Davis et al., U.S. Pat. No. 3,960,442); or lenses having anterior surfaces expressed as conicoids (see, e.g., Jalie, U.S. Pat. No. 4,289,387).
SUMMARY OF THE INVENTION
In one aspect, the invention features an ophthalmic lens. The lens includes a diameter D, an optically active central region of diameter D
1
, D
1
being less than D, a border region between D
1
and D, and a rotationally symmetric anterior surface. The lens has a thickness T
1
at D
1
and a thickness T at D. The rotationally symmetric anterior surface is convex throughout the optically active central region and is concave in at least part of the border region between D
1
and D. The lens can be used in the correction of hypermetropia.
The lens is an aspheric lens. An aspheric lens has an aspheric surface. A surface is aspheric when it is generated by rotation of a symmetrical, noncircular, curve about its axis of symmetry.
In another aspect, the invention features an ophthalmic lens series. The series includes a plurality of aspheric lenses. For each lens in the series, D
1
can be constant, T
1
−T can be constant (e.g., between 0.0 mm and 0.2 mm, inclusive), and can have a power of between +0.25 diopter and +8.00 diopter, inclusive. The series can include a finished lens or a semi-finished lens blank.
In another aspect, the invention features a method of manufacturing a lens. The lens includes a diameter D, an optically-active central region of diameter D
1
, D
1
being less than D, and a border region between D
1
and D. The lens has a thickness T
1
at D
1
and a thickness T at D. The method includes selecting a rotationally symmetric anterior surface, and forming a lens having the rotationally symmetric anterior surface and a posterior surface. The rotationally symmetric anterior surface is convex throughout the optically active central region and is concave in at least part of the border region between D
1
and D. The method can include finishing a semi-finished surface of the lens to form a lens having a finished prescription. In other embodiments, the method can include applying an abrasion-resistance coating or an anti-reflection coating to the lens. The selecting and the forming step can be repeated to generate a lens series including a plurality of lenses.
The optically active region within D
1
is a surface of revolution that can be described by a polynomial having only even terms, such as an eighth-order polynomial having only even terms. In certain embodiments, the optically active central region can be a surface of revolution described by a polynomial
z
C
(
r
)=Ar
2
+Br
4
+Cr
6
+Dr
8
,
where r is a radial distance from an optical axis of the lens. A, B, C, and D, together, are chosen to improve the optical performance and reduce the thickness within the optically active region over those values afforded by a spherical surface.
The border region between D
1
and D is a surface of revolution that can be described by a third-order polynomial. In certain embodiments, the border region can be a surface of revolution described by a polynomial
z
B
(
r
)=Er
3
+Fr
2
+Gr+H,
where E, F, G, and H, together, are chosen to substantially smoothly connect the border region to the optically active region. In certain embodiments, A, B, C, D, E, F, G and H can be related by the equations
Ar
1
2
+Br
1
4
+Cr
1
6
+Dr
1
8
=Er
1
3
+Fr
1
2
+Gr
2
+H;
Ar
2
2
+Br
2
4
+Cr
2
6
+Dr
2
8
=Er
2
3
+Fr
2
2
+Gr
2
+H;
Ar
3
2
+Br
3
4
+Cr
3
6
+Dr
3
8
=Er
3
3
+Fr
3
2
+Gr
3
+H; and
Er
4
3
+Fr
4
2
+Gr
4
+H=Er
1
3
+Fr
1
2
+Gr
1
+H+s,
where r
1
is D
1
/2, r
4
is D/2, and each of r
2
and r
3
, independently, are between R
1
and R
4
, and s is a numerical constant that establishes T
1
−T. For example, r
1
, r
2
and r
3
can be in the ratio of 1.00:0.96:0.92.
The difference T
1
−T can be equal to or greater than 0.0 mm and less than or equal to 0.2 mm. The lens can have a power of between +0.25 diopter and +8.00 diopter, inclusive (e.g., in 0.25 diopter increments). The lens can include a polymeric optical material, such as a thermoplastic (e.g., polycarbonate).
The rotationally symmetric anterior curve can be selected from an anterior base curve series. In other embodiments, the lens can further include a concave posterior surface selected from a rear base curve series. When the anterior curve is selected from an anterior base curve series, the lens can include a spherical posterior curve or a toroidal posterior curve. Accordingly, using an anterior base curve series, finished lenses and semi-finished lenses having substantially identical anterior optical surfaces can be manufactured.
The posterior curve can be applied to the posterior surface of a semi-finished lens, for example, using conventional optical laboratory machinery. Accordingly, a lens series covering the prescriptive range can be either an anterior base curve series, in which the posterior surface curvature is changed more frequently than the anterior surface curvature, or a posterior base curve series, in which the anterior surface curvature is changed more frequently than the posterior surface curvature.
The lenses can be reduced in thickness and weight and improved cosmetically while at the same time affording improved vision. The lenses can have satisfactory optical correction within the optically active

Affiliated with

Also associated with

Rating

Aspheric lenses does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Aspheric lenses, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aspheric lenses will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2468382