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AssigneeOptische Werke G. Rodenstock
InventorsAndrea Welk, Peter Baumbach, Walter Haimerl, Herbert Pfeiffer, Gregor Esser, Helmut Altheimer, Rainer Dorsch, Martin Zimmerman, Norbert Awrath, Jochen Brosig, Werner Mueller, Martin Wechs, Stephan Haser, Winfried Nikolaus
Estimating the term…
A spectacle lens is provided with a region (distance portion) designed for viewing at greater distances and, in particular, “to infinity”, a region (near portion) designed for viewing at short distances and, in particular, “reading distances”, and a progression zone disposed between the distance portion and the near portion, in which the power of the spectacle lens increases from the value in the distance reference point located in the distance portion to the value at the near reference point located in the near portion along a line (principal meridian) curving towards the nose. The invention is marked by specific conditions for the astigmatic deviation and/or the mean “as worn” power being observed.
Spectacle lens comprising:
Spectacle lens wherein:
Dependencies are inferred from the claim text.
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Shape of the progressive surface: properties on the principal line
Bifocal; multifocal ; progressive: spectacle lenses with progressively varying focal power
Spectacles
Term end not estimated
The present invention relates to a progressive spectacle lens.
Progressive spectacle lenses (also called varifocal lenses, multifocal lenses etc.) are usually understood to be spectacle lenses having a different (smaller) power in the region through which a spectacle wearer views an object located at a greater distance—hereunder designated as a distance portion—than in the region (near portion) through which the spectacle wearer views a near object.
Located between the distance portion and the near portion is the so-called progressive zone in which the power of the spectacle lens continuously increases from that of the distance portion to that of the near portion. The magnitude of the power increase is also designated as the power addition.
In the following the invention will be described by way of example, without limitation of the general inventive concept, with the aid of embodiments with reference to the drawings to which attention is expressly drawn concerning the disclosure of all details of the invention not described more explicitly in the text.
FIG. 1 shows the astigmatic deviation of a spectacle lens in accordance with the invention;
FIG. 2 shows the mean “as worn” power of this spectacle lens;
FIGS. 1 and 2 show the astigmatic deviation and the mean “as worn” power of an example of embodiment of the invention within a circle of 20 mm radius around a point lying 4 mm below the so-called centration point. The distance reference point and the near reference point are indicated by circles; their positions may be seen in the respective Figures.
In FIG. 1 the so-called astigmatic deviation, i.e. the “residual astigmatism” of the system spectacle lens/eye, is represented by so-called iso-lines, beginning with the iso-line 0.25 dpt. The iso-lines indicate the deviation of the astigmatism with respect to magnitude and cylinder axis from the cylindrical prescription—which is 0 dpt in the case of an eye free from astigmatism.
In FIG. 2 the mean “as worn” power D, i.e. the mean value of the reciprocals S′1 and S′2 of the back focal lengths minus the reciprocal of the object distance, that is the front focal length S,