Electronic ophthalmic lens for measuring distance using ultrasound time-of-flight

Abstract

A contact lens having an electronic system is described herein to provide lens accommodation using a distance measurement determined from an ultrasound time of flight signal. In at least one embodiment, the contact lens includes an ultrasound module, a system controller, a timing circuit, and an actuator. In at least one embodiment, the ultrasound module includes at least one transducer configured to emit a sound pressure wave outwardly and receive a reflected sound pressure wave from an object. A timer may track an elapsed time between generation and detection of the sound pressure wave by the at least one transducer to determine the distance to the object. In at least one embodiment, lens accommodation is further achieved using a communication link between a pair of contact lenses to determine a convergence angle based on independent distance measurements generated by each contact lens.

What is claimed is: 
     
         1 . An ophthalmic lens system comprising:
 a first ophthalmic lens; and   a second ophthalmic lens;   each of said first ophthalmic lens and said second ophthalmic lens including:
 at least one ultrasound module configured to generate a time of flight measurement signal; 
 a system controller electrically connected to said ultrasound module, said system controller configured to activate said ultrasound module using at least one preselected sampling frequency; and 
 a communications module in electrical communication with at least one of said ultrasound module or said system controller, said communications module configured to establish a communications link with said other ophthalmic lens; 
   wherein said communications module of said first ophthalmic lens is in signal communication with said communications module of said second ophthalmic lens during use;   wherein said system controller of said first ophthalmic lens receives the time of flight measurement signal generated by at least one ultrasound module on each ophthalmic lens, the time of flight measurement signals defining respective first and second distances to an object from each of said first ophthalmic lens and said second ophthalmic lens, and   wherein the respective first and second distances are used by said system controller of said first ophthalmic lens in combination with an ophthalmic lens separation distance to establish a convergence angle for setting an accommodation level of said first ophthalmic lens and said second lens.   
     
     
         2 . The ophthalmic lens systems according to  claim 1 , wherein said first ophthalmic lens is a first contact lens and said second ophthalmic lens is a second contact lens. 
     
     
         3 . The ophthalmic lens system according to  claim 1 , wherein each ophthalmic lens further includes an actuator electrically connected to said system controller on said ophthalmic lens to adjust a focus of said ophthalmic lens based on the accommodation level setting. 
     
     
         4 . The ophthalmic lens system according to  claim 1 , wherein said system controller on said first ophthalmic lens sets an accommodation level after at least five convergence angles have been established and maintained an angle within a predetermined angle threshold. 
     
     
         5 . An ophthalmic lens comprising:
 a timing circuit configured to produce a timing signal;   a system controller electrically connected to said timing circuit, said system controller configured to receive the timing signal and initiate an ultrasound time of flight measurement;   an actuator electrically connected to said system controller; and   an ultrasound module electrically connected to said system controller, said ultrasound module including:
 at least one transducer configured to emit a sound pressure wave outwardly from said ophthalmic lens and/or receive a reflected sound pressure wave; and 
 a timer configured to track an elapsed time between emission of the sound pressure wave and the first of detection of the reflected sound pressure wave or a time period as measured by said ultrasound module being exceeded; 
   wherein said ultrasound module generates the ultrasound time of flight measurement in response to receipt of an initiation signal from said system controller using said timer.   
     
     
         6 . The ophthalmic lens systems according to  claim 5 , wherein said first ophthalmic lens is a first contact lens and said second ophthalmic lens is a second contact lens. 
     
     
         7 . The ophthalmic lens systems according to  claim 5 , wherein said first ophthalmic lens is a first intraocular lens and said second ophthalmic lens is a second intraocular lens. 
     
     
         8 . The ophthalmic lens according to  claim 5 , wherein said actuator includes a lens accommodation controller electrically connected to said system controller, said lens accommodation controller configured to initiate an accommodation based on the ultrasound time of flight measurement. 
     
     
         9 . The ophthalmic lens according to  claim 8 , wherein said actuator further includes a lens driver electrically connected to said lens accommodation controller, said lens driver adjusts a focus of said ophthalmic lens in response to a signal from said lens accommodation controller. 
     
     
         10 . The ophthalmic lens according to  claim 5 , wherein said lens accommodation controller is configured to compare the ultrasound time of flight measurement to at least one reference time period to establish a distance defined by at least one of a preset value, a calibrated value, or a target processing value to set an accommodation. 
     
     
         11 . The ophthalmic lens according to  claim 5 , wherein said ultrasound module is configured to compare the ultrasound time of flight measurement to a reference time period to establish a distance defined by at least one of a preset value, a calibrated value, or a target processing value to set an accommodation. 
     
     
         12 . The ophthalmic lens according to  claim 5 , wherein said system controller is configured to compare the ultrasound time of flight measurement to a reference time period to establish a distance defined by at least one of a preset value, a calibrated value, or a target processing value to set an accommodation. 
     
     
         13 . The ophthalmic lens according to  claim 5 , wherein said timer includes a resettable counter, said resettable counter configured to be reset to zero upon initiation of the ultrasound time of flight measurement by said system controller. 
     
     
         14 . The ophthalmic lens according to  claim 13 , wherein said ultrasound module further includes:
 a digital signal processor including said resettable counter;   a switched oscillator having a programable frequency electrically connected to said digital signal processor; and   a burst generator electrically connected to said switched oscillator, said burst generator for gating said switched oscillator for a fixed amount of time to define a burst length, and   wherein said resettable counter is configured to count pulses from said switched oscillator to track the elapsed time between output of the sound pressure wave and the first of detection of the reflected sound pressure wave or a time period being exceeded.   
     
     
         15 . The ophthalmic lens according to  claim 14 , wherein said ultrasound module further includes:
 a driver electrically connected to said burst generator;   a multiplexer having at least one switch, said multiplexer electrically connected to said driver and said at least one transducer;   an amplifier electrically connected to said multiplexer; and   an analog signal processor electrically connected to said amplifier and said digital signal processor, and   wherein said at least one switch is configured to actuate by a generated burst through said driver and enable signal communication between said at least one transducer and said amplifier.   
     
     
         16 . The ophthalmic lens according to  claim 14 , wherein said ultrasound module further includes:
 a driver electrically connected to said burst generator and said at least one transducer;   an amplifier electrically connected to said at least one transducer; and   an analog signal processor electrically connected to said amplifier and said digital signal processor, and   wherein said amplifier and said analog signal processor are configured to at least one of:
 activate at a select time after said at least one transducer outputs the sound pressure wave, or 
 activate at the same time as said at least one transducer outputs the sound pressure wave and said digital signal processor is configured to initiate a lock out period to reduce false detection by said ultrasound module of extraneous sound pressure waves. 
   
     
     
         17 . The ophthalmic lens according to  claim 16 , wherein said analog signal processor is configured to transmit a reflected sound pressure wave detection signal to said digital signal processor; and
 wherein said digital signal processor stops counting the pulses from said switched oscillator upon the first of receiving the reflected sound pressure wave detection signal or the time period being exceeded.   
     
     
         18 . The ophthalmic lens according to  claim 17 , wherein at least one output from said digital signal processor is provided to said system controller to initiate a lens accommodation. 
     
     
         19 . The ophthalmic lens according to  claim 17 , wherein said analog signal processor includes at least one of a frequency selective filter, an envelop detector, an integrator, a level comparator, or an analog-to-digital converter. 
     
     
         20 . The ophthalmic lens according to  claim 5 , wherein said actuator includes an alert mechanism, and
 wherein said system controller is configured to send an initiation signal to said actuator in response to proximity of an object in front of a wearer of said ophthalmic lens.   
     
     
         21 . A method for operation of a first ophthalmic lens and a second ophthalmic lens, each of the first ophthalmic lens and the second ophthalmic lens including an ultrasound module, a system controller, a communications module, and an actuator, the method comprising:
 generating the first and second time measurement signals respectively by the ultrasound modules of each ophthalmic lens;   transmitting the first and second time measurement signals to the system controller of the second ophthalmic lens;   establishing respective first and second distances to an object from each of the ophthalmic lenses using the first and second time measurement signals by the system controller of the second ophthalmic lens;   calculating a convergence angle using a ophthalmic lens separation distance and the respective first and second distances to the object by the system controller of the second ophthalmic lens;   comparing the convergence angle to a reference convergence angle to establish an accommodation level; and   initiating the actuators to adjust a focus of the ophthalmic lenses when the accommodation level is different than a current accommodation level of the ophthalmic lenses.   
     
     
         22 . The method according to  claim 21 , further comprising repeating generating, transmitting, establishing, and calculating a plurality of times to confirm that the convergence angle remains within a predefined range prior to comparing the convergence angle and initiating the actuators. 
     
     
         23 . The method according to  claim 21 , further comprising calibrating the reference convergence angle of the ophthalmic lenses based on the first and second distances to an object held during the calibration of the first ophthalmic lens and the second ophthalmic lens.