OPTICAL LENS BLANK, A BLANK ASSORTMENT AND A METHOD FOR THE PRODUCTION OF LENSES

Abstract

An optical lens blank includes a first and a second lens surface, which are arranged opposite each other and which are delimited at a lens circumference, wherein the first lens surface has a surface geometry that corresponds to a first partial cutout from a first melon shape. A range of blanks consisting of such lens blanks have first lens surfaces of varying degrees of curvature, wherein the different degrees of curvature are based on different melon shapes. Finally, a method for producing a spectacle lens from such an optical lens blank includes mechanically shaping at least the first or second surface, and separating a cutout from the mechanically shaped lens blank.

Claims

1. An optical lens blank comprising a first and a second lens surface, which are arranged opposite each other and which are delimited at a lens circumference, wherein the first lens surface has a surface geometry that corresponds to a first partial cutout from a first melon shape.

2. The lens blank according to claim 1, wherein the first melon shape is elongated.

3. The lens blank according to claim 2, wherein the first melon shape is an ellipsoid.

4. The lens blank according to claim 3, wherein the ellipsoid is an ellipsoid of revolution that is, in particular, spanned by three ellipsoid radii, wherein the first and second ellipsoid radii have a same size, and a size of the third ellipsoid radius differs from the size of the first and second ellipsoid radii.

5. The lens blank according to claim 3, wherein the ellipsoid is a triaxial ellipsoid that is, in particular, spanned by three ellipsoid radii, wherein the first, second and third ellipsoid radii are each of a different size.

6. The lens blank according to claim 5, wherein the two smaller ellipsoid radii from the group of the first, second and third ellipsoid radii lie at an edge of or outside of the first lens surface.

7. The lens blank according to claim 4, wherein the larger ellipsoid radius from the group of the first, second and third ellipsoid radii is at least as large as the diameter of the lens blank.

8. The lens blank according to claim 1, wherein the size ratio between the smallest and the largest ellipsoid radius from the group of the first, second and third ellipsoid radii has a factor of between 1.15 and 4.00, preferably between 1.20 and 3.50, and particularly preferably between 1.25 and 3.00.

9. The lens blank according to claim 1, wherein the first lens surface is convex.

10. The lens blank according to claim 1, wherein the second lens surface is concave.

11. The lens blank according to claim 1, wherein the second lens surface has a surface geometry that corresponds to a partial cutout from a second melon shape.

12. The lens blank according to claim 11, wherein the size of the second melon shape differs by a multiplication factor from the size of the first melon shape, wherein the first melon shape and the second melon shape have the same shape.

13. The lens blank according to claim 12, wherein the first melon shape and the second melon shape have the same spatial orientation and the same center point.

14. A range of blanks consisting of 2 to 20 lens blanks according to claim 1, with first lens surfaces of different degrees of curvature, wherein the different degrees of curvature are based on different melon shapes.

15. A method for producing a spectacle lens from an optical lens blank according to claim 1, comprising the following steps: mechanically shaping at least one of the first lens surface or the second lens surface; separating a cutout from the mechanically shaped lens blank, which cutout has a partial cutout of the first and second lens surfaces, along a frame line.

16. The method according to claim 15, wherein the partial cutout has a vertical sight axis and a horizontal sight axis that intersect in a zero-visual axis, wherein the first and/or second lens surface has a lesser curvature along the vertical sight axis than along the horizontal sight axis.

17. The method according to claim 15, wherein the partial cutout has a vertical sight axis that intersects a zero-visual axis, wherein the curvature of the first and/or second lens surface along the vertical sight axis increases along a direction from a lens upper edge to a lens lower edge.

18. The lens blank according to claim 5, wherein the larger ellipsoid radius from the group of the first, second and third ellipsoid radii is at least as large as the diameter of the lens blank.

19. The lens blank according to claim 11, wherein the second melon shape is an ellipsoid.

20. The range of lens blanks according to claim 15, wherein different lens blanks of the range have respective first lens surfaces and second lens surfaces with different degrees of curvature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further features, details and advantages of the disclosure will become clear from the wording of the claims and also from the following description of illustrative embodiments with reference to the drawings, in which:

[0036] FIG. 1 shows a schematic view of how a first lens surface of an optical lens blank relates to a melon shape;

[0037] FIG. 2 shows a cross section through an optical lens blank; and

[0038] FIG. 3 shows a schematic view of how a first lens surface of an optical lens blank relates to a triaxial ellipsoid.

DETAILED DESCRIPTION

[0039] It will be seen from the schematic view in FIGS. 1 and 3 how a first lens surface 2 of an optical lens blank 1 relates to a first melon shape 10. The lens blank 1 has a first and a second lens surface 2, 3 which are arranged opposite each other and which are delimited at a circumference 4. The lens circumference 4 and therefore also the lens blank 1 have a circular basic shape. The first lens surface 2 is convex and the second lens surface 3 is concave.

[0040] In particular, the first lens surface 2 has a lens surface geometry that corresponds to a partial cutout T1 from the first melon shape 10. The position of the partial cutout T1 is indicated on the outer envelope of the first melon shape 10. It will be seen that the first melon shape 10 is elongated, in particular in the direction of the x coordinate axis.

[0041] The first melon shape 10 is an ellipsoid. This ellipsoid according to FIG. 1 is an ellipsoid of revolution which is in particular spanned by three ellipsoid radii R1, R2, R3, wherein the first and second ellipsoid radii R1, R2 are the same size, and the size of the third ellipsoid radius R3 differs from the size of the first and second ellipsoid radii R1, R2. Here, the third ellipsoid radius R3 in the direction of the x coordinate axis is larger than the first and second ellipsoid radii R1, R2 of identical size which point in the direction of the y coordinate axis and the z coordinate axis. This also means that the ellipsoid and the first melon shape 10 are not spheres or balls.

[0042] As an alternative to the embodiment shown in FIG. 1, the ellipsoid can also be configured as a triaxial ellipsoid according to FIG. 3. This too is spanned by three ellipsoid radii R1, R2, R3, wherein however the first, second and third ellipsoid radii R1, R2, R3 are each of a different size. The first ellipsoid radius R1 in the y coordinate axis is larger than the second ellipsoid radius R2 in the z coordinate axis. If the first melon shape 10 is elongated, as is the case here, and the ellipsoid is triaxial, the elongation is understood in the direction of the largest ellipsoid radius. This is the third ellipsoid radius R3 in FIG. 3.

[0043] Regardless of whether the ellipsoid is an ellipsoid of revolution or a triaxial ellipsoid, in FIGS. 1 and 3 the equator Q is as it were spanned by the first and second ellipsoid radii R1, R2. The point of intersection of the ellipsoid with the x coordinate axis or the two points of the ellipsoid at the greatest distance from the center point M of the ellipsoid form the two poles P1, P2 of the ellipsoid.

[0044] As will be seen from the position of the partial cutout T1, the two smaller ellipsoid radii R1, R2 from the group of the first, second and third ellipsoid radii R1, R2, R3, or the equator Q, lie outside of the first lens surface 2. As can also be seen, the larger or largest ellipsoid radius R3 from the group of the first, second and third ellipsoid radii R1, R2, R3 is at least as large as the diameter D of the lens blank 1. Preferably, the size ratio between the smallest and the largest ellipsoid radius from the group of the first, second and third ellipsoid radii R1, R2, R3 preferably gives a factor of between 1.15 and 4.00, more preferably between 1.20 and 3.50, and particularly preferably between 1.25 and 3.00.

[0045] The concave second lens surface 3 has a surface geometry that corresponds to a partial cutout from a second melon shape. Preferably, the size of the second melon shape differs by a multiplication factor from the size of the first melon shape T1, wherein the first melon shape Ti and the second melon shape have the same shape. Provision can optionally be made that the first melon shape T1 and the second melon shape have the same spatial orientation in respect of the x, y and z coordinate axes and the same center point. The second melon shape is then also an elongated ellipsoid. The latter is either configured as an ellipsoid of revolution or is alternatively a triaxial ellipsoid. As will be seen from the partial cutout T1 indicated in FIGS. 1 and 3, this results in an ellipsoid shell from which the lens blank 1 is obtained.

[0046] With a lens blank as shown in FIGS. 1 and 3, high-quality spectacle lenses can be produced by first mechanically shaping the second lens surface 3, or alternatively the first lens surface 2, or alternatively both the first and the second lens surface 2, 3. The necessary machining depends on the visual defect of the subsequent wearer of the spectacle lens. To this end, an individual prescription is in most cases established for correcting the visual defect. Based on the prescription, the desired surface geometry of the spectacle lens is calculated. After the surface geometry has been produced, a cutout is separated from the machined lens blank 1, which cutout in each case has a partial cutout of the first and second lens surface 2, 3. The circumference geometry of the lens blank 1 is machined until a frame line 5 is obtained. A spectacle lens is then obtained that has a vertical sight axis V and a horizontal sight axis H, which intersect in a zero-visual axis N (the spectacle lens wearer looking straight ahead). The vertical sight axis V is preferably oriented along and particularly preferably parallel to the plane that is spanned by the x and z coordinate axes and by the second and third ellipsoid radii R2, R3. The horizontal sight axis H is preferably oriented along and particularly preferably parallel to the plane that is spanned by the y and z coordinate axes and by the first and second ellipsoid radii R1, R2.

[0047] In addition, the horizontal sight axis H should be oriented at a distance from the plane that is spanned by the y and z coordinate axes. The vertical sight axis V preferably lies closer to the plane that is spanned by the x and z coordinate axes than the horizontal sight axis H lies to the plane that is spanned by the y and z coordinate axes.

[0048] In the present configuration, the curvature of the first lens surface 2 along the vertical sight axis V increases continuously from a lens upper edge 6 of the frame line 5 to a lens lower edge 7 of the frame line 5. Along the horizontal sight axis H, the curvature increases continuously from the inside outward. The curvature in the horizontal also becomes greater from the lens upper edge 6 to the lens lower edge 7.

[0049] The partial cutout T1 is also chosen such that all the curvatures along the vertical sight axis V are smaller than those along the horizontal sight axis H.

[0050] By grading the surface curvatures, or the first and second melon shapes 10 from which these are obtained, it is possible to assemble a range of blanks consisting of several first and second lens surfaces 2, 3 with different degrees of curvature. Depending on the visual defect to be corrected, and possibly also on the desired spectacle frame, it is then possible to select a suitable lens blank 1 from the range of blanks.

[0051] FIG. 2 shows a cross section through an optical lens blank 1 of the kind described above, in particular along the vertical sight axis V. It will also be seen here how the first and second lens surfaces 2, 3 lie opposite each other and are delimited at the lens circumference 4. The first lens surface 2 is based on a circular partial section T1 as is indicated on the envelope of the first melon shape 10 in FIG. 1. The geometry of the second lens surface 3 also corresponds to a circular partial section from the envelope of a melon shape. In this way, the optical lens blank 1 is configured as a round disc with a diameter D.

[0052] FIG. 2 also shows the spectacle lens which is to be produced and which is obtained by machining the second lens surface 3 to give a prescription surface 8 and adapting the lens circumference 4 to a frame line 5. Seen in cross section, a lens upper edge 6 and a lens lower edge 7 of the frame line 5 can be seen. Moreover, FIG. 2 shows where the zero-visual axis N lies, along which the subsequent wearer of the spectacles sees when looking straight ahead.

[0053] The embodiments of the disclosure described above and illustrated in the accompanying drawing figures do not limit the scope of the invention, since these embodiments are merely examples of embodiments of the disclosure. The invention is encompassed by the appended claims and their legal equivalents. Any equivalent embodiments lie within the scope of this disclosure. Indeed, various modifications of the present disclosure, in addition to those shown and described herein, such as other combinations and modifications of the elements described, will become apparent to those of ordinary skill in the art from the description. Such embodiments, combinations, and modifications also fall within the scope of the appended claims and their legal equivalents.