Series of lenses

Details Series of lenses Series of lenses

1996-03-21

1998-12-29

Sugarman, Scott J.

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Ophthalmic lenses or blanks

G02C 706

Patent

active

058546693

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a series of lenses in accordance with the introductory clauses of the independent patent claims.


PRIOR ART

Lenses of the type which the introductory clauses if the independent patent claims start out from comprise (as a rule) a front surface having a continuously varying surface power (progressive surface), which power at a point having the coordinates x=0 mm, y=8 mm) (as chosen within the general framework of the present application) (distance-vision reference point) in a lower region of the distance-vision part along a wound line (primary line) which coincides approximately with the primary line of view, with eyes dropped, i.e. the point at which the line of sight passes through the surface having a continuously varying surface power, with eyes dropped, towards a value suitable for near vision in the upper region of the near-vision part, which is higher--at the near-vision reference the lower region of the distance-vision part. The surface on the concave side presents a spherical or aspherical configuration or, respectively, a toroidal or non-toroidal configuration in the case of an astigmatic prescription.
The designers of progressive lenses have to manufacture such progressive lenses with different values of the surface power at the distance-vision reference point and/or with different increases of the value of the surface power from the distance-vision part towards the near-vision part (referred to as addition Add hereinafter) in order to satisfy the requirements of different vision defects or the different degrees of presbyopia, respectively. Owing to the different materials (silicate glass with a refractive index of 1.525, silicate glass with a high refraction whose refractive index amounts to 1.6 or even 1.7, for instance, as well as plastic materials) and in view of a great number of base lines and additions (as a rule from 0.5 dpt to 3.5 or 4 dpt, in steps of 0.25 dpt in typical cases), a "complete range" typically demands the calculation and production of 100 different surfaces, normally, however, by far more than 100.
In the past the lenses of this type, with different surface powers in the distance-vision part and/or with different increases of the surface power from the distance-vision part to the near-vision part, had to be calculated first by computing a progressive surface having a defined surface power and a defined addition, also termed near-vision addition. Starting out from this surface then the other surfaces were calculated, in which the addition or refraction varied, respectively, and which were necessary for the series. In this respect explicit reference is made to the U.S. Pat. No. 2,878,721, inter alia, which mentions explicitly this fact. Here explicit reference is made to this patent as well as to the German Patent DE-A-28 14 936 for the explanation of all the terms not defined here in detail, such as the surface power and the surface astigmatism.
More recently, progressive surfaces have been calculated for each separate surface power at the distance-vision reference point and for each individual addition--e.g. by means of so-called spline interpolation, i.e. by a method other than the derivation of a so-called parent surface by transformation.
In these calculation approaches frequently "performance functions" are employed in which the surface properties are specified from a physiologic point of view. The "reasonable" specification of the surface properties is hence of decisive significance for the calculation.
In accordance with the present invention it has been found that excessively far-reaching demands, e.g. with respect to the size of the distance-vision part, render the optimization of other surface properties more difficult, if not entirely impossible. For a rapid and economic calculation of a plurality of progressive surfaces, the specification of surface properties as a function of the base line (surface power BK in the distance-vision part) and/or the addition is hence of decisive importance.


BRIEF DESCRIPT

REFERENCES:
patent: 2878721 (1959-03-01), Kanolt

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