Multifocal ophthalmic lens

Claim 1

A pair of multifocal eyeglasses which utilizes varying focal lengths to provide accommodation for both near and far distances while allowing the user to view both near and far distances through the center of the lens or any part of the lens comprising: a pair of first and second lens elements, said lens elements including a first liquid crystal layer disposed adjacent said first lens, a second liquid crystal layer disposed adjacent said second lens and first and second electrodes connected to each of said first and second liquid crystal layers, said first and second lenses being substantially coextensive with said first and second liquid crystal layers, respectively, said liquid crystal layers capable of changing in orientation to present a variable index of refraction under the action of an applied electric field; a voltage supply source for applying a voltage to said electrodes to vary the index of refraction presented by said first and second liquid crystal layers, such that in response to application of said variable voltage to said electrodes, the focal length of said first and second lenses changes; means for varying said voltage applied to said electrodes to determine the focal length of the lens elements including means for tracking the movement of the eyes of the user, such that a convergent movement of the eyes for near and distant vision and parallel lateral movement of both eyes is detected, said means for tracking the movement of the eyes including a first light source mounted adjacent said first lens element for generating a beam of light to impinge upon the sclera of the user's eye adjacent and to the side of the limbus of that eye when the user is looking straight ahead at distant objects, a second light source mounted adjacent said second lens element for generating a beam of light directed to impinge upon the cornea of the other eye of the user, adjacent and to the side of the limbus of that eye when the user is looking straight ahead at distant objects, and at least one photodiode light detector mounted adjacent each said lens element for detecting light from said first and second light sources that is reflected from each eye and for producing output signals; and means responsive to said tracking means for generating a control signal for application to said voltage supply source including amplifier means for amplifying the signals from said photodiodes and processing means for providing the control signal based upon the relative intensity of light sensed by said photodiodes, said processing means being programmed such that no change in the control signal occurs when parallel lateral movement of both eyes is detected to prevent unwanted change of the focal length of said lens.