Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1996-06-28
1999-03-09
Epps, Georgia
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
351176, G02C 706
Patent
active
058808108
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a series of ophthalmic lenses.
STATE OF THE ART
Ophthalmic lenses of the type which are provided (usually) with a front surface having a continuously varying surface power (progressive surface), distance in the point having (within the scope of the present application) the coordinates x=0 mm, y=8 mm (distance reference point) in the lower region of the distance part along a curved line (principle line), which approximately coincides with the principal line of vision when lowering the glance, i.e. the piercing point of the viewing beam when lowering the glance through the surface having continuously varying power, to a value suited for seeing near in the upper region of the near part, which, in the near reference point, is higher by the value Add (dpt) of the addition than the surface power BK in the lower region of the distance part. The surface facing the eye is designed for fulfilling the astigmatic prescription atorically.
Manufacturers of progressive ophthalmic lenses have to fabricate this type of progressive ophthalmic lenses having varying surface power in the distance reference point and/or a varying increase in surface power from the distance part to the near part (hereinafter referred to as addition Add) as well as having varying astigmatic power and axial positions in order to meet the requirements of varying vision errors respectively varying degrees of long-sightedness of old age. Due to the variety of materials (silicate glass having a refractive index of 1.525, high index silicate glass having a refractive index of, e.g., 1.6 or 1.7 as well as plastic) and a multiplicity of basis curves and additions (usually from 0.5 dpt to 3.5 or 4 dpt in gradations of typically 0.25 dpt), it is necessary to calculate and to fabricate typically at least 100, usually however far more different surfaces for a "complete program".
In the past, this type of ophthalmic lenses having varying surface power in the distance part and/or a varying increase in the surface power from the distance part to the near part were calculated by first having calculated a progressive surface having a specific surface power and a specific addition, also referred to as near addition. From this surface, the other surfaces having deviating addition power respectively a deviating surface power needed for the series are derived by means of a transformation procedure. With regard to this, reference is made to U.S. Pat. No. 2,878,721 in which this is expressly mentioned. For the explanation of all terms, such as surface power and surface astigmatism, not individually defined herein reference is explicitly made to this printed publication as well as to DE-A-28 14 936.
For some time, progressive surfaces have been calculated separately for each surface power in the distance reference point and for each addition, by way of illustration by means of splines, thus not derived from a so-called parent surface by means of transformation procedures. The atoric surface, depending on the progressive opposite surface and the axial position, i.e., also the orientation to the progressive opposite surface, is also calculated separately.
In these calculation procedures, "objective functions" in which the surface properties prescribed from physiological considerations are used. Therefore a "reasonable" provision of surface properties is of decisive significance for the calculation.
An element of the present invention is that is was recognized that excessive demands, by way of illustration regarding the size of the distance part, impedes optimization of other surface properties if not prevents it. Thus the provision of surface properties as the function of the fundamental values, such as spherical power, the cylinder and the axial position of the atoric surface including the basis curve (surface power BK in the distance part) and/or the addition of the progressive surface are of decisive significance for quick and economical calculation of a multiplicity of progressive surfaces having a respective atoric
REFERENCES:
patent: 3910691 (1975-10-01), Maitenaz
patent: 5444503 (1995-08-01), Kelch
Altheimer Helmut
Barth Rudolf
Baumbach Peter
Brosig Jochen
Esser Gregor
Epps Georgia
Optische Werke G. Rodenstock
Schwartz Jordan M.
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