04637697 is referenced by 213 patents and cites 13 patents.

A bifocal contact lens has diffractive power added to the basic refractive power provided by the material of the lens and the basic curvature of its front and rear surfaces. The diffractive power arises from concentric zones, each providing an asymmetric retardation of light across the zone width to direct design wavelength light predominantly into a required order and sign of diffraction, while other wavelength light is predominantly transmitted at zero order. Design wavelength light from an object at one distance can then be focused by way of diffraction of that order and sign, and other wavelength light from an object at another distance can be focused by way of zero order transmission. Preferably the zones are defined, and the asymmetric retardation provided, by a rear surface contour having steps but which approximates to the required basic curvature.

Title
Multifocal contact lenses utilizing diffraction and refraction
Application Number
368362
Publication Number
4637697
Application Date
October 19, 1983
Publication Date
January 20, 1987
Inventor
Michael H Freeman
Wales
GB
Agent
Mark P Stone
F Eugene Davis IV
Assignee
Pilkington P E
GB
IPC
G02B 27/44
G02B 3/08
G02C 7/06
G02C 7/04
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