Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1989-01-11
1990-08-07
Sugarman, Scott J.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
G02C 706
Patent
active
049462709
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a progressive power ophthalmic lens, in which at least one surface contributes to an increase in refractive power from the distant portion via the progressive zone to the reading portion, and in which the radii of curvature of the section curves (horizontal sections) of the surface or surfaces having horizontal planes contributing to the increase in refractive power decrease in the distant portion and increase in the reading portion in the front surface in the main meridian region as a function of the distance from the main meridian and increase in the distant portion and decrease in the reading portion in the rear surface, and in which the course of the change in curvature reverses with increasing distance from the main merdian.
STATE OF THE ART
In general, the problem with progressive power ophthamlic lenses is that the progression, i.e. the increase in refractive power on the main meridian leads to a sharp rise in astigmatism and in distortion in the peripheral regions due to the intersecting resulting from the continuity conditions of the surface.
For this reason, it has already been proposed in U.S. Pat. No. 2,878,721 to let the curvatures of the orthogonal or horizontal sections increase in the distant portion in the front surface with increasing distance from the main meridian and decrease in the reading portion. According to this publication, the result is a circular section between the distant and the reading portion as a transition from the region, in which the radii of curvature increase, to the region, in which the radii of curvature decrease. As a consequence of this concept, the differences between the distant and the reading portions in the peripheral region diminish and in this way there are less aberrations and, in particular, less lower surface astigmatism or distortion values.
A disadvantage of this known concept is, however, that the lines of the same surface refractive power are also curved upward in the region about the main merdian in the distant portion and downward in the reading portion; thus the lines of the same surface refractive power do not run horizontally. In order to reduce the curvature of the lines of the same surface refractive power upward or downward, it has already been proposed in U.S. Pat. No. 2,878,721 that the course of the change in curvature of horizontal or orthogonal sections reverse with increasing distance from the main meridian.
This concept described in U.S. Pat. No. 2,878,721 of changing the radii of curvature of horizontal or orthogonal sections in the main meridian region, the course of which is essentially the same as the course of the horizontal sections, has been adopted by DE-AS No. 20 44 639, DE-OS No. 30 16 935 and DE-OS No. 31 51 766.
Despite the reversal of the course of the change in curvature of the horizotal or orthogonal sections, the known surfaces have the disadvantage that the lines of the same surface refractive power are strongly bent especially in the progressive zone to both sides of the main meridian.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a progressive ophthalmic lens in which the lines of the same surface refractive power run mainly horizontally at least in the main meridian region.
Strikingly, one solution to the aforementioned object is successful by proceeding from an ophthalmic lens and by selecting the surface in such a manner that the course of the change in the curvature of the horizontal sections with increasing distance from the main meridian is yielded by superimposing two functions F.sub.1 (x,y,) and F.sub.2 (x,y). In accordance with the first function F.sub.1 (x,y), the radius of curvature in the front surface initially increases or decreases in the rear surface, whereby the change in the radius of curvature reverses at a distance of approximately 14 to 26 mm. In accordance with the second function F.sub.2 (x,y), the radius of curvature in the front surface initially decreases and increases in the rear surface, w
Barth Rudolf
Guilino Gunther
Stetter Hans
Optische Werke G. Rodenstock
Sugarman Scott J.
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