Single vision lenses
View Patent ↗Optical lens element with a prescription zone, suitable for use in wraparound or protective type eyewear. The element may also include a peripheral vision zone, with no prismatic jump between the zones. Design methods for the prescription zone include temporally rotating a prescription section about a vertical axis through the optical center thereof, and/or decentring the optical axis of said prescription section relative to the geometric axis thereof, and providing partial surface correction for astigmatic and/or mean power errors. For prescription powers in the range −6.0 to +6.0 diopters with 0 to 3 cyl, the optical lens element may be designed such that its front surface can be mounted in a frame of constant curvature of at least 5.0 diopters, with its back surface providing good clearance from temples and eyelashes. Applications include ophthalmic sunglass lenses.
1. A method of manufacturing an optical lens element adapted for mounting in a form of the wrap-around or shield type, which method includes
providing mathematical or numerical representation of a front or back surface of an optical lens element including a section designed to provide the desired prescription (Rx) in the prescription zone; and optionally adding thereto a mathematical or numerical representation of a peripheral temporal zone to define a complete lens surface;
rotating and/or decentering the representation of the lens surface to permit mounting in a suitable frame; and
modifying the representation of the lens surface to at least partially correct for errors including astigmatic and mean power errors.
2. A method according to claim 1 , including
providing a mathematical or numerical representation of an aspheric front surface of an optical lens element including a section designed to provide the desired prescription (Rx) in the prescription zone and having appropriate aspheric coefficients to define a peripheral temporal zone;
rotating and/or decentering the representation of the lens surface to permit mounting in a suitable frame;
subsequently providing a mathematical or numerical representation of a prescription (Rx) back surface; and
modifying the representation of the back surface of the lens element to at least partially adjust for errors including astigmatic and mean power errors.
3. A method according to claim 2 , including
providing a mathematical or numerical representation of a surface of an optical lens element including a section designed to provide the desired prescription (Rx) in the prescription zone; and adding thereto
a first mathematical or numerical representation of a peripheral temporal zone thereto; and
a second mathematical or numerical representation of a transition section designed to smoothly blend the prescription zone and peripheral temporal zone to define a complete lens surface;
rotating and/or decentering the representation of the lens surface to permit mounting in a suitable frame; and
modifying the representation of the lens surface to at lease partially adjust for errors including astigmatic and mean power errors.
4. A method according to claim 3 , wherein a surface of the optical lens element is represented by the following formulas
sag−SAG R≦R 0 ,
wherein R is the radius measured from the optical axis and A 2 , A 4 , A 6 , and A 8 are coefficients that define power and asphericity;
sag−SAG+DSAG R≧R 0 ,
wherein R 0 defines the periphery of the temporal region; and
DSAG=B 2 ( R−R 0 ) 2 +B 4 ( R−R 0 ) 4 +B 6 ( R−R 0 ) 6 +B 8 ( R−Ro ) 8
wherein B 2 , B 4 , B 6 , and B 8 are coefficients that define power and asphericity.
5. A method according to claim 4 , wherein the surface is represented by the formula
sag=SAG+α( DSAG ) N for R≧R 0 ,
where α and N≧1 are numerical parameters.