Carl-Zeiss-Stiftung

Gerhard Furter

Hans Lahres

The invention contemplates a multi-focal spectacle lens having two progressive zones which are spatially separated from each other and which provide smooth transition of dioptric power, from one to the next of three different viewing-distance regions. This progressive surface is calculated in accordance with the technique of spline analaysis and is twice continuously differentiable. Such a progressive lens, which is illustratively described for use at computer-screen work stations, has an upper viewing-distance region designed for distant vision, a middle viewing-distance region designed for viewing the computer screen as well as a document arranged alongside the screen, and a lower viewing-distance region designed for near-vision requirements of keyboard operation. Laterally of the near-vision region the power of the lens decreases so that documents lying to the side of the keyboard can also be seen sharply, without moving one's head.

Multi-focal spectacle lens having at least one progressive surface

Eyeglass lenses for persons suffering from severe ametropia. The lenses have a convexly shaped object-side front surface (4) and an eye-side rear surface (3) which is aspherically corrected in the central region (6) which comprises at least the main field of view. From this region the rear surface passes into a region in which its meridional inclination approaches the inclination of the front surface. The entire rear surface of the lens is continuously differentiable twice. Such a lens has an appearance which is fully satisfactory esthetically and makes it possible to keep the overall magnification of the system consisting of the eye and the eyeglass lens closer to 1 than in the case of previously known lenses. Aberrations are optimally corrected within a sufficiently large region, and no disturbing discontinuities in the fields of view occur.

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Aalen, Germany

Gerhard Furter