Multi-focal spectacle lens having at least one progressive surface
First Claim
1. A multi-focal continuous-focus spectacle lens with at least one progressive surface of progressively varying power which is so shaped that spaced lens regions of different but constant viewing distances pass progressively and continuously into each other, characterized by the fact that said lens has two separate progressive zones (5,6) of continuously varying optical power, which zones are spaced from each other and change the dioptric powers of three viewing-distance regions (upper 2 , middle 3, lower 4) continuously into each other, each of said viewing-distance regions being of substantially constant dioptric power, and that the progressive surface is twice continuously differentiable nasally and temporally at least up to a horizontal viewing angle of substantially 25°
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Abstract
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.
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17 Claims
- 1. A multi-focal continuous-focus spectacle lens with at least one progressive surface of progressively varying power which is so shaped that spaced lens regions of different but constant viewing distances pass progressively and continuously into each other, characterized by the fact that said lens has two separate progressive zones (5,6) of continuously varying optical power, which zones are spaced from each other and change the dioptric powers of three viewing-distance regions (upper 2 , middle 3, lower 4) continuously into each other, each of said viewing-distance regions being of substantially constant dioptric power, and that the progressive surface is twice continuously differentiable nasally and temporally at least up to a horizontal viewing angle of substantially 25°
Specification