Method for designing a lens shape and spectacle lens

Patent metadata

Field	Value
Publication number	US-10775641-B2
Application number	US-201815986456-A
Country	US
Kind code	B2
Filing date	May 22, 2018
Priority date	Nov 23, 2015
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

A computer-implemented method for providing a lens shape for an ophthalmic lens is disclosed. Further, there is provided a method for angular smoothing of a surface determined by carrier lines radially outwards of a prescription zone bordered by a first boundary line. In addition, there is provided an ophthalmic lens, in particular, a spectacle lens. Moreover, a method for minimizing the difference in thickness between two ophthalmic lenses for the same spectacles is provided. A computer program product and a machine-readable storage medium are provided as well.

First claim

The invention claimed is:

1. A computer-implemented method for providing a lens shape for an ophthalmic lens, the method comprising:
a) providing a predetermined lens shape of an ophthalmic lens having a front surface and a back surface, wherein the predetermined lens shape includes a predetermined shape of the front surface and a predetermined shape of the back surface within a prescription zone of the back surface bordered by a first boundary line, such that the ophthalmic lens satisfies predetermined optical properties within the prescription zone;
b) determining a carrier point on the back surface within the prescription zone and a plurality of carrier lines each extending from the carrier point into a respective direction;
c) determining a transition zone of the back surface, wherein the transition zone extends radially outwards from the first boundary line towards the outer edge of the ophthalmic lens and ends at a second boundary line bordering the transition zone radially outwards;
d) for each carrier line, setting a desired constant curvature gradient over the transition zone;
e) for each carrier line, determining a curvature profile of the back surface between the first boundary line and an outer edge of the ophthalmic lens along the carrier line, wherein the curvature profile in the transition zone is determined based on the respective desired constant curvature gradient; and
f) flattening a profile of the curvature of the prescription zone in the direction of the carrier lines along the first boundary line via approximation by a polynomial function, a spline function, or a Fourier series to obtain a flattened curvature profile and to provide for angular smoothing of the back surface radially outwards of the first boundary line, wherein the flattened curvature profile is set as a radially inward starting curvature value for each carrier line.

2. The method according to claim 1 , wherein a curvature along the carrier line between the second boundary line and the outer edge is essentially constant and equals the curvature along the carrier line in the transition zone at the second boundary line.

3. The method according to claim 1 , wherein the desired constant curvature gradient is set based on the curvature of the prescription zone at the first boundary line and a boundary condition for the curvature within the transition zone.

4. The method according to claim 1 , wherein the desired constant curvature gradient is set based on the curvature of the prescription zone at the first boundary line and a curvature target to be reached at the second boundary line, and wherein the curvature target is at least one of zero or a curvature of the front surface.

5. The method according to claim 1 , wherein the curvature gradient is set to be negative in case the ophthalmic lens is a minus lens and the curvature gradient is set to be positive in case the ophthalmic lens is a plus lens.

6. The method according to claim 1 , wherein the curvature profile is determined by determining a cubic spline from the first boundary line to the second boundary line, wherein the cubic spline includes a plurality of sections each described by a cubic polynomial, and wherein the cubical polynomials are determined section-wise from the first boundary line to the second boundary line.

7. A computer-implemented method for providing a lens shape for an ophthalmic lens, the method comprising:
a) providing a predetermined lens shape of an ophthalmic lens having a front surface and a back surface, wherein the predetermined lens shape includes a predetermined shape of the front surface and a predetermined shape of the back surface within a prescription zone of the back surface bordered by a first boundary line, such that the ophthalmic lens satisfies predetermined optical properties within the prescription zone;
b) determining a carrier point on the back surface within the prescription zone and a plurality of carrier lines each extending from the carrier point into a respective direction;
c) determining a transition zone of the back surface, wherein the transition zone extends radially outwards from the first boundary line towards the outer edge of the ophthalmic lens and ends at a second boundary line bordering the transition zone radially outwards;
d) for each carrier line, setting a desired constant curvature gradient over the transition zone:
e) for each carrier line, determining a curvature profile of the back surface between the first boundary line and an outer edge of the ophthalmic lens along the carrier line, wherein the curvature profile in the transition zone is determined based on the respective desired constant curvature gradient and
f) flattening a profile of the curvature of the prescription zone in the direction of the carrier lines along the first boundary line via approximation by a polynomial function, a spline function, or a Fourier series to obtain a flattened curvature profile and to provide for angular smoothing of the back surface radially outwards of the first boundary line, wherein the flattened curvature profile is set as a radially inward starting curvature value for each carrier line,
wherein the curvature profile is determined by determining a cubic spline from the first boundary line to the second boundary line, wherein the cubic spline includes a plurality of sections each described by a cubical polynomial, and wherein the cubical polynomials are determined section-wise from the first boundary line to the second boundary line such that a sagittal height, a slope, and a curvature of the back surface along the carrier line are continuous, and the curvature gradient is reset to the desired constant curvature gradient for each polynomial at the radially inwards end of each section.

8. The method of claim 1 , wherein a length of the transition zone along each carrier line is constant, resulting in the second boundary line bordering the transition zone radially outwards, and the second boundary line being radially offset from the first boundary line by the length of the transition zone.

9. The method according to claim 8 , wherein the length of the transition zone is within a range of at least 10 mm up to and including 20 mm.

10. The method according to claim 1 , wherein the constant curvature gradient has a magnitude in a range of at least and including 0.05 diopters/mm up to and including 1.5 diopters/mm.

11. The method according to claim 6 , wherein the length of each section is within a range of at least and including 0.5 mm up to and including 2 mm.

12. The method according to claim 1 , wherein the method further comprises:
checking, for each carrier line, whether a thickness of the ophthalmic lens at least at one of an outer edge or an intended frame line along which the ophthalmic lens is to be edged is above a predefined threshold and, if not, changing a magnitude of the desired constant curvature gradient.

13. The method according to claim 1 , wherein the ophthalmic lens is an uncut finished spectacle lens.

14. The method according to claim 1 , wherein a curvature profile of the predetermined lens shape of the back surface is preserved within the first boundary line.

15. The method according to claim 1 , wherein at least a sagittal height of the prescription zone of the back surface transitions continuously at the first boundary line into each carrier line.

16. The method according to claim 8 , wherein the length of the transition zone is measured within a tangential plane oriented tangentially to the carrier point of the back surface.

17. The method according to claim 1

Assignees

• Zeiss Carl Vision Int Gmbh

Inventors

• Spratt Ray Steven
• Ellinger Philipp
• Wietschorke Helmut
• Nolan Angela
• Varnas Saulius

Classifications

• G02C2202/04

  Lenses comprising decentered structures · CPC title

• G02C7/028 Primary

  Special mathematical design techniques · CPC title

• G02C7/063

  Shape of the progressive surface · CPC title

• G02C7/027

  considering wearer's parameters · CPC title

• G02C7/024 Primary

  Methods of designing ophthalmic lenses · CPC title