Liquid crystal lens with enhanced electrical drive

Abstract

Adaptive spectacles include a spectacle frame and first and second electrically-tunable lenses, mounted in the spectacle frame and having respective focal powers and optical centers that are determined by control voltages applied thereto. Control circuitry is configured to apply the control voltages so as to shift the optical centers of the electrically-tunable lenses responsively to the focal powers of the electrically-tunable lenses.

1 . Adaptive spectacles, comprising:
 a spectacle frame;   first and second electrically-tunable lenses, mounted in the spectacle frame and having respective focal powers and optical centers that are determined by control voltages applied thereto; and   control circuitry, which is configured to apply the control voltages to the electrically-tunable lenses so as to shift the optical centers of the electrically-tunable lenses responsively to the focal powers of the electrically-tunable lenses.   
     
     
         2 . The spectacles according to  claim 1 , wherein the control circuitry is configured to shift the optical centers of the first and second electrically-tunable lenses downward when the focal powers of the electrically-tunable lenses are increased. 
     
     
         3 . The spectacles according to  claim 1 , wherein the control circuitry is configured to reduce a distance between the optical centers of the first and second electrically-tunable lenses when the focal powers of the electrically-tunable lenses are increased. 
     
     
         4 . The spectacles according to  claim 1 , wherein each of the first and second electrically-tunable lenses comprises:
 an electro-optical layer, having an effective local index of refraction at any given location within an active area of the electro-optical layer that is determined by a voltage waveform applied across the electro-optical layer at the location; and   conductive electrodes disposed over opposing first and second side of the electro-optical layer,   wherein the control circuitry is coupled to apply the control voltages to the conductive electrodes.   
     
     
         5 . The spectacles according to  claim 4 , wherein the electro-optical layer comprises a liquid crystal. 
     
     
         6 . The spectacles according to  claim 4 , wherein the control circuitry is configured to apply the control voltages between the conductive electrodes so as to generate a phase modulation profile in the electro-optical layer that causes rays of optical radiation that are incident on the electrically-tunable lenses to converge or diverge with a given focal power, while varying an amplitude of the control voltages for the given focal power responsively to an angle of incidence of the rays that impinge on the electrically-tunable lenses from a direction of interest. 
     
     
         7 . The spectacles according to  claim 4 , wherein the control circuitry is configured to change the electrically-tunable lenses from a first focal power to a second focal power by concurrently applying overshoot control voltages to each of a plurality of the conductive electrodes for different, respective transition periods, followed by application of the control voltages corresponding to the second focal power. 
     
     
         8 . The spectacles according to  claim 4 , wherein the control circuitry is configured to apply the control voltages between the conductive electrodes so as to generate a phase modulation profile in the electro-optical layer that causes rays of optical radiation that are incident on the electrically-tunable lenses to converge or diverge with a given focal power, and to change the electrically-tunable lenses from the given focal power to zero focal power by concurrently applying a predefined maximum high voltage to all of the conductive electrodes on the first side of the electro-optical layer, followed by application of a predefined low voltage thereto. 
     
     
         9 . The spectacles according to  claim 4 , wherein the control voltages comprise waveforms selected so as to cause the electrically-tunable lenses to function as Fresnel lenses. 
     
     
         10 . An optical method, comprising:
 providing spectacles including first and second electrically-tunable lenses mounted in a spectacle frame and having respective focal powers and optical centers that are determined by control voltages applied thereto;   receiving an input indicative of a distance from an eye of a person wearing the spectacles to an object viewed by the person; and   responsively to the distance, automatically modifying the control voltages so as both to tune the focal powers and to shift the optical centers of the electrically-tunable lenses.   
     
     
         11 . The method according to  claim 10 , wherein automatically modifying the control voltages comprises shifting the optical centers of the first and second electrically-tunable lenses downward when the distance is less than a predefined threshold distance. 
     
     
         12 . The method according to  claim 10  wherein automatically modifying the control voltages comprises reducing a distance between the optical centers of the first and second electrically-tunable lenses when the distance is less than a predefined threshold distance. 
     
     
         13 . The method according to  claim 10 , wherein each of the first and second electrically-tunable lenses comprises:
 an electro-optical layer, having an effective local index of refraction at any given location within an active area of the electro-optical layer that is determined by a voltage waveform applied across the electro-optical layer at the location; and   conductive electrodes disposed over opposing first and second side of the electro-optical layer,   wherein the control voltages are applied to the conductive electrodes.   
     
     
         14 . The method according to  claim 13 , wherein the electro-optical layer comprises a liquid crystal. 
     
     
         15 . An optical method, comprising:
 providing spectacles including first and second electrically-tunable lenses mounted in a spectacle frame and having respective focal powers and optical centers that are determined by control voltages applied thereto; and   applying the control voltages so as to shift the optical centers of the electrically-tunable lenses responsively to the focal powers of the electrically-tunable lenses.   
     
     
         16 . The method according to  claim 15 , wherein applying the control voltages comprises shifting the optical centers of the first and second electrically-tunable lenses downward when the focal powers of the electrically-tunable lenses are increased. 
     
     
         17 . The method according to  claim 15 , wherein applying the control voltages comprises reducing a distance between the optical centers of the first and second electrically-tunable lenses when the focal powers of the electrically-tunable lenses are increased. 
     
     
         18 . The method according to  claim 15 , wherein each of the first and second electrically-tunable lenses comprises:
 an electro-optical layer, having an effective local index of refraction at any given location within an active area of the electro-optical layer that is determined by a voltage waveform applied across the electro-optical layer at the location; and   conductive electrodes disposed over opposing first and second side of the electro-optical layer,   wherein the control voltages are applied to the conductive electrodes.   
     
     
         19 . The method according to  claim 18 , wherein the electro-optical layer comprises a liquid crystal.