PATENT DOCUMENT

Publication Number: US-11880111-B1
Application Number: US-202117181911-A
Country: US
Kind Code: B1

Title: Tunable lens systems with voltage selection circuitry

Abstract:
A pair of eyeglasses may include one or more adjustable lenses that are each configured to align with a respective one of a user&#39;s eyes. The adjustable lenses may each include electrically modulated optical material such as one or more liquid crystal cells, each having a phase profile that is adjusted using patterned electrodes. Analog voltages may be provided to the patterned electrodes through variable-resistance conductive paths that are each coupled to a subset of the patterned electrodes. Digital voltage selection circuitry may be used to select which analog voltage to apply to each of the variable-resistance conductive paths from a predetermined set of analog voltages that are generated off of the lens. The digital voltage selection circuitry may include an array of multiplexers, each of which selects a desired voltage based on control signals received from digital control circuitry such a shift register and/or a decoder.

Claims:
What is claimed is: 
     
       1. An adjustable lens configured to be worn in front of a user&#39;s eye, comprising:
 an electrically modulated optical material interposed between first and second transparent substrates; 
 a common electrode on the first substrate; 
 an array of patterned electrodes on the second substrate that adjust a phase profile of the electrically modulated optical material; 
 an array of variable-resistance conductive paths that are each coupled to a respective subset of the patterned electrodes; 
 a switch coupled between two of the variable-resistance conductive paths in the array of variable-resistance conductive paths; and 
 digital voltage selection circuitry that selects an analog voltage from a predetermined set of voltages that are generated off of the adjustable lens and that provides the selected analog voltage to a respective one of the variable-resistance conductive paths. 
 
     
     
       2. The adjustable lens defined in  claim 1 , wherein the digital voltage selection circuitry comprises a multiplexer. 
     
     
       3. The adjustable lens defined in  claim 2  wherein the multiplexer receives the predetermined set of voltages on a set of data input lines. 
     
     
       4. The adjustable lens defined in  claim 3  wherein the digital voltage selection circuitry comprises digital control circuitry that provides control bits to the multiplexer and wherein the multiplexer selects the analog voltage based on the control bits received from the digital control circuitry. 
     
     
       5. The adjustable lens defined in  claim 4  wherein the digital control circuitry comprises a decoder. 
     
     
       6. The adjustable lens defined in  claim 4  wherein the digital control circuitry comprises a shift register. 
     
     
       7. The adjustable lens defined in  claim 4  wherein the digital control circuitry comprises a decoder and a shift register that provides an address signal to the decoder. 
     
     
       8. The adjustable lens defined in  claim 7  wherein the decoder decodes the address signal to the control bits and provides the control bits to the multiplexer. 
     
     
       9. The adjustable lens defined in  claim 1  wherein each of the variable-resistance conductive paths has a serpentine pattern and has first and second opposing ends coupled respectively to first and second metal conductors. 
     
     
       10. The adjustable lens defined in  claim 9  wherein the digital voltage selection circuitry provides the selected analog voltage to a respective one of the variable-resistance conductive paths via the first metal conductor. 
     
     
       11. The adjustable lens defined in  claim 1  wherein the electrically modulated optical material comprises liquid crystal material. 
     
     
       12. An adjustable lens comprising a stack of liquid crystal cells, wherein each liquid crystal cell comprises:
 liquid crystal material interposed between first and second substrates; 
 an array of transparent conductive electrodes that adjust a phase profile of the liquid crystal material; 
 an array of serpentine conductive paths on opposing sides of the array of transparent conductive electrodes, wherein each of the serpentine conductive paths is coupled to a group of the transparent conductive electrodes; and 
 an array of multiplexers, each of which provides a voltage to a respective one of the serpentine conductive paths, wherein the voltage is selected from a predetermined set of voltages that are generated off of the adjustable lens. 
 
     
     
       13. The adjustable lens defined in  claim 12  further comprising an array of decoders, each of which provides control signals to an associated one of the multiplexers. 
     
     
       14. The adjustable lens defined in  claim 13  further comprising an array of shift registers, each of which provides address signals to an associated one of the decoders. 
     
     
       15. The adjustable lens defined in  claim 12  wherein the array of serpentine conductive paths comprises first and second serpentine conductive paths, the adjustable lens further comprising a switch coupled between the first and second serpentine conductive paths. 
     
     
       16. The adjustable lens defined in  claim 12  wherein the array of transparent conductive electrodes and the array of serpentine conductive paths comprise indium tin oxide. 
     
     
       17. Eyeglasses, comprising:
 a housing; 
 an adjustable lens in the housing having a liquid crystal cell, an array of electrodes, and control lines that apply voltages to the array of electrodes to adjust a phase profile of the liquid crystal cell; and 
 off-lens control circuitry in the housing having an operational amplifier that receives a feedback voltage from the adjustable lens and that provides an output voltage to a given one of the control lines based on the feedback voltage and based on a selected input voltage that is generated by the off-lens control circuitry, wherein the adjustable lens comprises first and second variable-resistance conductive paths and a switch coupled between the first and second variable-resistance conductive paths, wherein each of the first and second variable-resistance conductive paths is coupled to a respective subset of the electrodes, and wherein a given one of the first and second variable-resistance conductive paths receives the output voltage from the given one of the control lines. 
 
     
     
       18. The eyeglasses defined in  claim 17  wherein the operational amplifier has a high impedance inverting input and wherein the feedback voltage is fed to the high impedance inverting input of the operational amplifier. 
     
     
       19. The eyeglasses defined in  claim 18  wherein the selected input voltage is one of a predetermined set of input voltages generated by the off-lens control circuitry.

Description:
This application claims the benefit of U.S. provisional patent application No. 62/985,240, filed Mar. 4, 2020, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to optical systems, and, more particularly, to devices with tunable lenses. 
     Eyewear may include optical systems such as lenses. For example, eyewear such as a pair of glasses may include lenses that allow users to view the surrounding environment. 
     It can be challenging to design devices such as these. If care is not taken, the optical systems in these devices may not be able to accommodate different eye prescriptions and may not perform satisfactorily. 
     SUMMARY 
     Eyeglasses may be worn by a user and may include one or more adjustable lenses each aligned with a respective one of a user&#39;s eyes. For example, a first adjustable lens may align with the user&#39;s left eye and a second adjustable lens may align with the user&#39;s right eye. Each of the first and second adjustable lenses may include one or more liquid crystal cells or other voltage-modulated optical material. Each liquid crystal cell may include a layer of liquid crystal material interposed between transparent substrates. Control circuitry may apply control signals to an array of electrodes in the liquid crystal cell to adjust a phase profile of the liquid crystal material. 
     Analog voltages may be provided to the array of electrodes through variable-resistance conductive paths that are each coupled to a subset of the patterned electrodes. The variable-resistance conductive paths may have a serpentine pattern. Digital voltage selection circuitry may be used to select which analog voltage to apply to each of the variable-resistance conductive paths from a predetermined set of analog voltages that are generated off of the lens. The digital voltage selection circuitry may include an array of multiplexers, each of which selects a desired voltage for a given one of the variable-resistance conductive paths based on control signals received from digital control circuitry such a shift register and/or a decoder. By using digital voltage selection circuitry that selects the desired analog voltage from a predetermined set of analog voltages, the number of signal paths between off-lens control circuitry and on-lens circuitry may be reduced, and the need for excessive analog circuitry on valuable lens real estate may be reduced. 
     The eyeglasses may include a housing, an adjustable lens in the housing having a liquid crystal cell, an array of electrodes, and control lines that apply voltages to the array of electrodes to adjust a phase profile of the liquid crystal cell. The eyeglasses may include off-lens control circuitry in the housing having an operational amplifier that receives a feedback voltage from the adjustable lens and that provides an output voltage to a given one of the control lines based on the feedback voltage and a selected input voltage that is generated by the off-lens control circuitry. The operational amplifier may be used to ensure that the output voltage provided to each control line matches the selected input voltage. 
     Liquid crystal materials are herein used by way of an example of an electrically modulated optical material. Other electrically modulated optical materials can be used in place of the liquid crystals described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of illustrative system that includes eyeglasses with adjustable lenses in accordance with an embodiment. 
         FIG.  2    is a cross-sectional side view of an illustrative liquid crystal cell that may be used to form an adjustable lens in accordance with an embodiment. 
         FIG.  3    is a cross-sectional side view of an illustrative liquid crystal module having first and second liquid crystal layers with antiparallel liquid crystal alignment orientations in accordance with an embodiment. 
         FIGS.  4  and  5    are graphs showing how an adjustable lens may be adjusted so that its refractive index varies as a function of position to produce a desired lens profile in accordance with an embodiment. 
         FIG.  6    is a top view of an illustrative adjustable lens component having arrays of electrodes that extend along first and second directions in accordance with an embodiment. 
         FIG.  7    is a top view of an illustrative adjustable lens component having arrays of electrodes that extend along first, second, and third directions in accordance with an embodiment. 
         FIG.  8    is an exploded perspective view of an illustrative adjustable lens having first, second, and third liquid crystal cells, each with an associated orientation of electrodes, in accordance with an embodiment. 
         FIG.  9    is an exploded perspective view of an illustrative adjustable lens having first, second, and third liquid crystal modules, each with an associated orientation of electrodes, in accordance with an embodiment. 
         FIG.  10    is a perspective view of a foveated adjustable lens system in accordance with an embodiment. 
         FIG.  11    is a top view of an illustrative adjustable lens system having a subset of electrodes driven such as to create a lens patch with variable optical power that aligns with a user&#39;s gaze in accordance with an embodiment. 
         FIG.  12    is a diagram of an illustrative adjustable lens having an array of electrodes that receive control signals from control signal lines through a resistive strip in accordance with an embodiment. 
         FIG.  13    is a top view of an illustrative adjustable lens having resistive strips along opposing edges of the lens in accordance with an embodiment. 
         FIG.  14    is a top view of an illustrative adjustable lens component in which multiple liquid crystal cells share a common pair of substrates that may be cut and folded in accordance with an embodiment. 
         FIG.  15    is a top view of an illustrative adjustable lens component in which multiple liquid crystal cells share a common pair of substrates that may be cut and folded in accordance with an embodiment. 
         FIG.  16    is a top view of an illustrative adjustable lens component having variable-resistance serpentine paths that each couple a group of finger electrodes to a terminal in accordance with an embodiment. 
         FIG.  17    is a schematic diagram of illustrative digital circuitry that may be used in an adjustable lens component to select a desired voltage from a voltage palette in accordance with an embodiment. 
         FIG.  18    is a schematic diagram of illustrative shift register and decoder circuitry that may be used in an adjustable lens component to select a desired voltage from a voltage palette in accordance with an embodiment. 
         FIG.  19    is a schematic diagram of illustrative circuitry such as an off-lens operational amplifier that may be used to ensure that a voltage provided to an on-lens control line matches a selected input voltage in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative system having a device with one or more electrically adjustable optical elements is shown in  FIG.  1   . System  10  may include a head-mounted device such as eyeglasses  14  (sometimes referred to as glasses  14 ). Glasses  14  may include one or more optical systems such as adjustable lens components  22  mounted in a support structure such as support structure  12 . Structure  12  may have the shape of a pair of eyeglasses (e.g., supporting frames), may have the shape of goggles, may form a housing having a helmet shape, or may have other configurations to help in mounting and securing the components of glasses  14  on the head of a user. 
     Adjustable lens components  22  may form lenses that allow a viewer (e.g., a viewer having eyes  16 ) to view external objects such as object  18  in the surrounding environment. Glasses  14  may include one or more adjustable lens components  22 , each aligned with a respective one of a user&#39;s eyes  16 . As an example, lens components  22  may include a left lens  22  aligned with a viewer&#39;s left eye and may include a right lens  22  aligned with a viewer&#39;s right eye. This is, however, merely illustrative. If desired, glasses  14  may include adjustable lens components  22  for a single eye. 
     Adjustable lenses  22  may be corrective lenses that correct for vision defects. For example, eyes  16  may have vision defects such as myopia, hyperopia, presbyopia, astigmatism, higher-order aberrations, and/or other vision defects. Corrective lenses such as lenses  22  may be configured to correct for these vision defects. Lenses  22  may be adjustable to accommodate users with different vision defects and/or to accommodate different focal ranges. For example, lenses  22  may have a first set of optical characteristics for a first user having a first prescription and a second set of optical characteristics for a second user having a second prescription. Glasses  14  may be used purely for vision correction (e.g., glasses  14  may be a pair of spectacles) or glasses  14  may include displays that display virtual reality or augmented reality content (e.g., glasses  14  may be a head-mounted display). In virtual reality or augmented reality systems, adjustable lens components  22  may be used to move content between focal planes from the perspective of the user. Arrangements in which glasses  14  are spectacles that do not include displays are sometimes described herein as an illustrative example. 
     Glasses  14  may include control circuitry  26 . Control circuitry  26  may include processing circuitry such as microprocessors, digital signal processors, microcontrollers, baseband processors, image processors, application-specific integrated circuits with processing circuitry, and/or other processing circuitry and may include random-access memory, read-only memory, flash storage, hard disk storage, and/or other storage (e.g., a non-transitory storage media for storing computer instructions for software that runs on control circuitry  26 ). 
     If desired, control circuitry  26  may include one or more energy storage devices such as one or more batteries and capacitors. Energy storage devices in eyeglasses  14  may be charged via a wired connection or, if desired, eyeglasses  14  may charge energy storage devices using wirelessly received power (e.g., inductive wireless power transfer, using capacitive wireless power transfer, and/or other wireless power transfer configurations). 
     Glasses  14  may include input-output circuitry such as eye state sensors, range finders disposed to measure the distance to external object  18 , touch sensors, buttons, microphones to gather voice input and other input, sensors, and other devices that gather input (e.g., user input from viewer  16 ) and may include light-emitting diodes, displays, speakers, and other devices for providing output (e.g., output for viewer  16 ). Glasses  14  may, if desired, include wireless circuitry and/or other circuitry to support communications with a computer or other external equipment. If desired, a sensor system such as sensor system  24  may be used to gather input during use of glasses  14 . Sensor system  24  may include an accelerometer, compass, an ambient light sensor or other light detector, a proximity sensor, a scanning laser system, and other sensors for gathering input during use of glasses  14 . Sensor system  24  may be used to track a user&#39;s eyes  16 . For example, sensor system  24  may include one or more digital image sensors, lidar (light detection and ranging) sensors, ultrasound sensors, or other suitable sensors for tracking the location of a user&#39;s eyes. As an example, sensor system  24  may be used by control circuitry  26  to gather images of the pupils and other portions of the eyes of the viewer. The locations of the viewer&#39;s pupils and the locations of the viewer&#39;s pupils relative to specular glints from light sources with known positions or the rest of the viewer&#39;s eyes may be used to determine the locations of the centers of the viewer&#39;s eyes (i.e., the centers of the user&#39;s pupils) and the direction of view (gaze direction) of the viewer&#39;s eyes. In some arrangements, sensor system  24  may include a wavefront sensor that measures the aberrations of a user&#39;s eyes. Control circuitry  26  may then adjust the optical properties of lens component  22  to correct the user-specific aberrations detected by the wavefront sensor. 
     Control circuitry  26  may also control the operation of optical elements such as adjustable lens components  22 . Adjustable lens components  22 , which may sometimes be referred to as adjustable lenses, adjustable lens systems, adjustable optical systems, adjustable lens devices, tunable lenses, etc., fluid-filled variable lenses, and/or may contain electrically adjustable material such as liquid crystal material, volume Bragg gratings, or other electrically modulated material that may be adjusted to produce customized lenses. Each of components  22  may contain an array of electrodes that apply electric fields to portions of a layer of liquid crystal material or other voltage-modulated optical material with an electrically adjustable index of refraction (sometimes referred to as an adjustable lens power or adjustable phase profile). By adjusting the voltages of signals applied to the electrodes, the index of refraction profile of components  22  may be dynamically adjusted. This allows the size, shape, and location of the lenses formed within components  22  to be adjusted. 
     A cross-sectional side view of an illustrative adjustable lens component is shown in  FIG.  2   . As shown in  FIG.  2   , component  22  may include liquid crystal cell  40 . Liquid crystal cell  40  may have a layer of voltage-modulated optical material such as liquid crystal layer  34 . Liquid crystal layer  34  may be interposed between transparent substrates such as upper substrate  32  and lower substrate  30 . Substrates  32  and  30  may be formed from clear glass, sapphire or other transparent crystalline material, cellulose triacetate, transparent plastic, or other transparent layers. Component  22  may have a pattern of electrodes that can be supplied with signals from control circuitry  26  to produce desired voltages on component  22 . In the example of  FIG.  2   , these electrodes include elongated electrodes (e.g., strip-shaped electrodes) such as electrodes  38  on substrate  30  that run along the X dimension and a common electrode such as common electrode  36  on substrate  32  (e.g., a blanket layer of conductive material on substrate  32 ). Electrodes  36  and  38  may be formed from transparent conductive material such as indium tin oxide, conductive polymers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PPS), or other transparent electrode structures and may be located on outer and/or inner surfaces of substrates  32  and  30 . 
     At each location of electrode strips  38  in component  22 , a desired voltage may be applied across liquid crystal layer  34  by supplying a first voltage to electrode  38  and a second voltage (e.g., a ground voltage) to common electrode  36 . The liquid crystal between the two electrodes will receive an applied electric field with a magnitude that is proportional to the difference between the first and second voltages on the electrodes. By controlling the voltages on electrodes  38  and common electrode  36 , the index of refraction of liquid crystal layer  34  of component  22  can be dynamically adjusted to produce customized lenses. 
     In the example of  FIG.  2   , strip-shaped electrodes  38  (sometimes referred to as finger electrodes, patterned electrodes, etc.) extend parallel to the X-axis. This allows the index-of-refraction profile (sometimes referred to as the phase profile) of liquid crystal cell  40  to be modulated in the Y-dimension by applying the desired voltages to each finger electrode  38 . 
     When an electric field is applied to the liquid crystals of layer  34 , the liquid crystals change orientation. The speed at which a given liquid crystal material can be reoriented is limited by factors such as the thickness of layer  34  (e.g., thickness T 1  of  FIG.  2   , sometimes referred to as the cell gap). To increase the tuning speed of liquid crystal layer  34  while still achieving a suitable tuning range, adjustable lens component  22  may include two or more liquid crystal cells  40  stacked on top of one another. This type of arrangement is illustrated in  FIG.  3   . 
     As shown in  FIG.  3   , adjustable lens component  22  may include liquid crystal module  44 . Liquid crystal module  44  may include two or more liquid crystal cells  40 . Each liquid crystal cell may include liquid crystal layer  34  interposed between upper substrate  32  and lower substrate  30 . Finger electrodes  38  may be formed on each lower substrate  30  and may extend parallel to the X-axis. Common electrode  36  may be formed on each upper substrate  32 . If desired, common voltage electrode  36  may be formed on lower substrate  30  and finger electrodes  38  may be formed on upper substrate  32 . The example of  FIGS.  2  and  3    is merely illustrative. 
     The cell gap of each liquid crystal cell  40  in module  44  may be less than that of liquid crystal cell  40  of  FIG.  2   . For example, liquid crystal layers  34  of module  44  in  FIG.  3    may each have a thickness T 2 , which is less than thickness T 1  of liquid crystal layer  34  in cell  40  of FIG.  2 . The reduced cell gap increases the tuning speed of liquid crystal layers  34  while still maintaining satisfactory tuning range (sometimes referred to as lens power range). 
     If desired, the liquid crystal alignment orientation (sometimes referred to as a rubbing direction) of liquid crystal cells  40  in module  44  may be antiparallel. In particular, liquid crystal molecules  42 A of upper liquid crystal cell  40  may have a first liquid crystal alignment orientation, and liquid crystal molecules  42 B of lower liquid crystal cell  40  may have a second liquid crystal alignment orientation that is antiparallel to the first liquid crystal alignment orientation. This type of arrangement may help reduce the angle dependency of phase retardation in module  44 . 
     At each location of finger electrode  38  in component  22 , a desired voltage may be applied across each liquid crystal layer  34  by supplying a first voltage to finger electrode  38  and a second voltage (e.g., a ground voltage) to common electrode  36 . The liquid crystal between the two electrodes will receive an applied electric field with a magnitude that is proportional to the difference between the first and second voltages on the electrodes. By controlling the voltages on electrodes  38  and common electrode  36 , the index of refraction of each liquid crystal layer  34  of component  22  can be dynamically adjusted to produce customized lenses. Because finger electrodes  38  extend along the X-dimension, the phase profile of each liquid crystal cell  40  may be modulated in the Y-dimension by applying the desired voltages to each finger electrode  38 . 
     Overlapping portions of the two liquid crystal layers  34  in module  44  may be controlled using the same or different voltages to achieve the desired index of refraction at that portion of module  44 . For example, finger electrode  38 A of upper liquid crystal cell  40  in module  44  may overlap finger electrode  38 B of lower liquid crystal cell  40  in module  44 . A first voltage V 1  may be applied across a portion of upper liquid crystal layer  34  overlapping finger electrode  38 A, and a second voltage V 2  may be applied across a portion of lower liquid crystal layer  34  overlapping finger electrode  38 B. Voltages V 1  and V 2  may be different or may be the same. Control circuitry  26  may determine the ratio of V 1  to V 2  based on the desired index of refraction at that portion of the liquid crystal module  44  and based on the disposition of the user&#39;s eyes  16 . 
       FIGS.  4  and  5    show examples of illustrative index-of-refraction profiles that may be generated by adjustable lens component  22  of  FIG.  2    and/or by adjustable lens component  22  of  FIG.  3   . In the example of  FIG.  4   , refractive index n has been varied continuously between peripheral lens edges Y 1  and Y 2 . In the example of  FIG.  5   , refractive index n has been varied discontinuously to produce an index-of-refraction profile appropriate for forming a Fresnel lens. These examples are merely illustrative. If desired, other suitable index-of-refraction profiles may be used using adjustable lens components of the type shown in  FIGS.  2  and  3   . 
     In the examples of  FIGS.  2  and  3   , adjustable lens component  22  includes electrodes that extend in one direction (e.g., the X-dimension of  FIGS.  2  and  3   ), allowing adjustable lens component  22  to modulate the phase profile of component  22  along one direction (e.g., the Y-dimension of  FIGS.  2  and  3   ). If desired, adjustable lens component  22  may include electrodes that extend in multiple directions, thus allowing adjustable lens component  22  to modulate the phase profile of component  22  along multiple directions. 
       FIG.  6    is a top view of illustrative adjustable lens component  22  having first finger electrodes  38 - 1  oriented along a first direction and second finger electrodes  38 - 2  oriented along a second direction different from the first direction. First finger electrodes  38 - 1  may, for example, be oriented at 90-degree angles relative to second finger electrodes  38 - 2 , or other suitable orientations may be used. Each set of electrodes may modulate the phase profile of a liquid crystal layer along an associated dimension. Adjustable lens component  22  of the type shown in  FIG.  6    with two orientations of electrodes may therefore be used to create phase profiles that vary along two dimensions. For example, electrodes  38 - 1  may produce a first quadratic phase profile along a first dimension and electrodes  38 - 2  may produce a second quadratic phase profile along a second dimension, thus providing lens components  22  with a combined phase profile matching that of a crossed-cylinder lens, with a spherical profile where the cylinders overlap (as an example). 
       FIG.  7    is a top view of an illustrative adjustable lens component  22  having first finger electrodes  38 - 1  oriented along a first direction, second finger electrodes  38 - 2  oriented along a second direction, and third finger electrodes  38 - 3  oriented along a third direction. Finger electrodes  38 - 1 ,  38 - 2 , and  38 - 3  may, for example, be separated by 60-degree angles or may have other suitable orientations. Each set of electrodes may modulate the phase profile of a respective liquid crystal layer along an associated dimension. Adjustable lens components  22  of the type shown in  FIG.  7    with three orientations of electrodes may therefore be used to create phase profiles that vary along three dimensions. 
     The examples of  FIGS.  6  and  7    in which lens component  22  includes two and three orientations of electrodes, respectively, are merely illustrative. If desired, lens component  22  may include one, two, three, four, five, six, more than six, or any other suitable number of orientations of electrodes to enable lens component  22  to achieve different phase profiles across any suitable number of dimensions. Lens components  22  with multiple orientations of electrodes may be configured to simultaneously correct for optical aberrations such as defocus, astigmatism, coma, trefoil, spherical, and/or other aberrations. Arrangements in which adjustable lens components  22  include three orientations of electrodes are sometimes described herein as an illustrative example. 
       FIGS.  8  and  9    show exploded perspective views of illustrative lens components  22  with three orientations of electrodes. In the example of  FIG.  8   , adjustable lens components  22  include three liquid crystal cells  40 . Each liquid crystal cell  40  may have a structure of the type described in connection with  FIG.  2   , with finger electrodes  38 - 1 ,  38 - 2 , and  38 - 3  oriented along three different directions. For example, finger electrodes  38 - 1  may be oriented at 0 degrees relative to the X-axis, finger electrodes  38 - 2  may be oriented at 120 degrees relative to the X-axis, and finger electrodes  38 - 3  may be oriented at 60 degrees relative to the X-axis. This is merely illustrative, however. In general, electrodes  38 - 1 ,  38 - 2 , and  38 - 3  may have any suitable orientation. 
     In the example of  FIG.  9   , adjustable lens components  22  include three liquid crystal modules  44 . Each liquid crystal module  44  may have a structure of the type described in connection with  FIG.  3   . In particular, each liquid crystal module  44  may include an upper liquid crystal cell  40  and a lower liquid crystal cell  40 . The liquid crystal layers of the upper and lower liquid crystal cells  40  may, if desired, have antiparallel liquid crystal alignment orientations. As shown in  FIG.  9   , finger electrodes  38 - 1 ,  38 - 2 , and  38 - 3  of liquid crystal modules  44  are oriented along three different directions. For example, finger electrodes  38 - 1  may be oriented at 0 degrees relative to the X-axis, finger electrodes  38 - 2  may be oriented at 120 degrees relative to the X-axis, and finger electrodes  38 - 3  may be oriented at 60 degrees relative to the X-axis. This is merely illustrative, however. In general, electrodes  38 - 1 ,  38 - 2 , and  38 - 3  may have any suitable orientation. 
     The foregoing examples in which lens components  22  have a rectangular shape ( FIG.  6   ) or a hexagonal shape ( FIGS.  7 ,  8 , and  9   ) are merely illustrative. If desired, lens component  22  (e.g., substrate  30 , substrate  32 , liquid crystal layer  34 , etc.) may have circular shapes, triangular shapes, pentagonal shapes, oval shapes, ergonomic shapes, convex shapes, or any other suitable shape. Arrangements in which lens components  22  are hexagonal are sometimes described herein as an illustrative example. 
     In some arrangements, control circuitry  26  may modulate the lens power across the entirety of each lens component  22 . This type of arrangement may be useful in configurations where glasses  14  do not include sensor system  24  for eye tracking and/or when the tuning speed of lens components  22  is not sufficiently high to maintain focus when the user&#39;s eye moves. Modulating the lens power from edge to edge of components  22  may ensure that the image remains in focus even when the user&#39;s eye moves around. 
     In other arrangements, control circuitry  26  may modulate lens power across only a portion of lens component  22 . This type of foveated lens arrangement is illustrated in  FIG.  10   . 
     Viewers are most sensitive to image detail in the main field of view. Peripheral regions of a lens may therefore be provided with a different phase profile than the region of the lens within the user&#39;s gaze. The peripheral regions of the lens that are outside of the viewer&#39;s gaze may, for example, be optically unmodulated, may be provided with a phase profile that is constant across a given area, and/or may be provided with a phase profile that is less spatially varied than the portion of the lens in the direction of the viewer&#39;s gaze. The regions of the lens outside of the user&#39;s gaze may have an optical power magnitude that is less than the optical power magnitude of the lens region within the user&#39;s gaze. By including lower power areas in a variable-power lens, total required variable phase depth and power consumption can be minimized and/or reduced. Further, magnification changes (which could be disorienting to the user) are experienced only over the area of the lens where focal power is modulated. Gaze detection data (e.g., gathered using sensor system  24 ) may be used in determining which portion of lens component  22  is being directly viewed by viewer  16  and should therefore have the optically appropriate prescription and which portions of lens components  22  are in the viewer&#39;s peripheral vision and could be left optically unmodulated or otherwise provided with a phase profile having less spatial variation than the portions of lens components  22  within the viewer&#39;s gaze. 
     As shown in  FIG.  10   , for example, adjustable lens component  22  may have an active area such as active area  48 . Within active area  48 , adjustable lens components  22  may include one or more materials having an electrically adjustable index of refraction (e.g., liquid crystal cells  40  of the type discussed in connection with  FIGS.  2 - 9   ). Control circuitry  26  may dynamically adjust the phase profile of lens components  22 . Active area  48  may include gaze area  46  and peripheral area  50 . Gaze area  46  corresponds to the portions of lens components  22  that are within the user&#39;s gaze, whereas peripheral area  50  corresponds to the portions of lens components  22  that are outside of the user&#39;s gaze (e.g., portions of lens components  22  that are in the user&#39;s peripheral vision). Gaze area  46  of lens components  22  may be provided with a different phase profile than peripheral area  50 . For example, gaze area  46  may be optically modulated to produce a first lens power, while peripheral area  50  may be left optically unmodulated, may be optically modulated to produce a second lens power magnitude that is less than the first lens power magnitude, and/or may be optically modulated to produce a phase profile that is less spatially varied than the phase profile of gaze area  46 . 
     Control circuitry  26  may dynamically adjust the location, size, resolution, or shape of gaze area  46  and peripheral area  50  during operation of glasses  14 . For example, control circuitry  26  may use sensor system  24  to track a user&#39;s gaze and may adjust the location of gaze area  46  so that it remains aligned with the user&#39;s gaze. If desired, the size of gaze area  46  may be based on the size of the foveal region in a user&#39;s eyes, the user&#39;s pupil diameter, and/or the desired phase profile for gaze area  46 . Gaze area  46  may, for example, have a diameter between 4 mm and 9 mm, between 7 mm and 9 mm, between 6 mm and 10 mm, between 4 mm and 8 mm, between 8 mm and 12 mm, greater than 10 mm, less than 10 mm, or any other suitable size. The size of gaze area  46  may be based on a distance between lens components  22  and a user&#39;s eyes  16 , may be based on the size of the user&#39;s pupil  52  (e.g., as measured with sensor system  24  or as inferred based on eye charts, ambient light levels, or other data), and/or may be based on other information. 
     In gaze area  46 , control circuitry  26  may modulate the index of refraction of liquid crystal material  34  to obtain the desired lens power and the desired vision correction properties for the viewer. This may include, for example, controlling each finger electrode  38  independently or controlling small sets of finger electrodes  38  with common control signals. In peripheral area  50 , control circuitry  26  may control larger sets of finger electrodes  38  with common control signals and/or may provide a ground or baseline voltage to finger electrodes  38  (e.g., may deactivate some finger electrodes  38 ). If desired, optical power may be constant across gaze area  46  and phase may be flat across peripheral area  50 . In other suitable arrangements, optical power may be varied across gaze area  46  and/or peripheral area  50 . 
       FIG.  11    is a top view of illustrative adjustable lens components  22  showing how areas of different optical power magnitude may be achieved. As shown in  FIG.  11   , adjustable lens components  22  may include gaze area  46  and peripheral area  50 . Gaze area  46  may have a first lens power magnitude and peripheral area  46  may have a second lens power magnitude that is less than the first lens power magnitude. Gaze area  46  may, for example, align with the foveal region of a user&#39;s eyes  16  (as shown in  FIG.  10   ). Electrodes that overlap (i.e., pass through) gaze area  46  such as electrodes  38 - 1 ,  38 - 2 , and  38 - 3  may be controlled to make a desired prescription within gaze area  46  and electrodes that do not pass through gaze area  46  (not shown in  FIG.  11   ) may be controlled to produce a spatially constant phase or a phase that otherwise has less spatial variation than that of gaze area  46 . 
     Control circuitry  26  may dynamically adjust the location of gaze area  46  based on gaze location information from sensor system  24  by actively identifying which electrodes are within a user&#39;s gaze and which electrodes are outside of a user&#39;s gaze. Electrodes within a user&#39;s gaze (e.g., in area  46 ) may be operated in optically modulated mode, and electrodes outside of the user&#39;s gaze (e.g., in area  50 ) may be operated in constant phase mode or may otherwise be operated to produce a phase profile with less spatial variation than that of gaze area  46 . 
     Whereas lens components with only two different electrode orientations (e.g., lens component  22  of  FIG.  6   ) may be capable of expressing spherical profiles and correcting one of two modes of astigmatism, lens components with three or more electrode orientations may be capable of expressing a greater number of different types of phase profiles (to correct higher order aberrations, astigmatism with any rotational axis, coma, spherical aberration, etc.). Additionally, using more than two electrode orientations may help ease the transition between gaze region  46  (e.g., where the phase profile of liquid crystal layer  34  is actively controlled) and peripheral region  50  (e.g., where the phase profile of liquid crystal layer  34  is not actively controlled). 
     It may be desirable to form finger electrodes with a relatively fine pitch. If care is not taken, large gaps between adjacent finger electrodes  38  can lead to optical defects such as unwanted diffraction and phase profile imperfections.  FIG.  12    shows an illustrative arrangement for obtaining closely spaced finger electrodes  38 . As shown in  FIG.  12   , finger electrodes  38  may receive control signals from control signal lines  56 . The spacing between adjacent control signal lines  56  may be greater than the spacing between finger electrodes  38 . Each control signal line  56  may provide an associated voltage (e.g., V 1 , V 2 , V 3 , etc.) to conductive electrodes  38  through a resistive strip  54 . Resistive strip  54  may be formed from a conductive material such as transparent conductive material (e.g., indium tin oxide), metal (e.g., tungsten, gold, silver, or other suitable metals), polysilicon, or other conductive material. Resistive strip  54  may have distributed resistance levels that vary along length L. Resistive strip  54  may take a serpentine path or a straight path, as illustrated in  FIG.  12   . Resistive strip  54  electrically couples control signal lines  56  to finger electrodes  38  and helps distribute control signals to the array of finger electrodes  38 . Due to the resistance of strip  54 , the voltage applied to electrodes  38  varies (e.g., varies linearly) from V 1  to V 2 , from V 2  to V 3 , etc. For example, an electrode  38  half way between control signal line  56  providing voltage V 1  and control signal line  56  providing voltage V 2  may receive a voltage that is halfway between voltages V 1  and V 2 . 
       FIG.  13    is a top view of lens components  22  showing how resistive strip  54  may be located at one or more edges of the lens. For example, first and second strips may be coupled to first and second opposing ends of finger electrodes  38  to drive finger electrodes  38  from both sides. This is, however, merely illustrative. If desired, strip  54  may only be located on one side of lens  22 , may be located on three or more sides of lens  22 , or may extend continuously around the perimeter of lens  22 . Resistive strip  54  may, for example, be formed on each substrate  30  in lens  22  to distribute control signals to each orientation of electrodes  38 . 
     Control circuitry  26  may provide control signals to control signal lines  56 , which may in turn apply voltages to finger electrodes  38  through resistive strip  54 . Control circuitry  26  may include one or more integrated circuits mounted directly to lens  22  (e.g., in a chip-on-glass arrangement) or may include one or more integrated circuits mounted to a separate substrate and coupled to lens  22  through one or more flex circuits or other types of paths. 
     In arrangements where lens component  22  includes multiple liquid crystal cells  40 , it may be desirable to use a flexible substrate (e.g., for substrate  30  and/or substrate  32  in each cell  40 ). For example, substrate  30  and/or substrate  32  may be formed from flexible materials such as a flexible polymer (e.g., polyimide or other suitable polymer), cellulose triacetate (TAC), or other suitable flexible material. The use of a flexible substrate in liquid crystal cells  40  may allow for thinner substrates (e.g., 40 microns or other suitable thickness) that are still robust. Additionally, flexible substrates can be deformed or bent in one or more dimensions, which may allow lens component  22  to be embedded in or laminated to a standard lens in eyeglasses with a meniscus shape (e.g., convexo-concave eyeglasses or other contoured eyeglasses). 
     Flexible substrates may also alleviate the challenge of electrically interfacing with each liquid crystal cell  40  in lens component  22 . For example, multiple liquid crystal cells  40  in lens component may share a common pair of substrates formed from flexible material that has been bent and folded. 
       FIG.  14    shows an example of an illustrative lens component  22  with twelve liquid crystal cells  40  that share a common pair of flexible substrates. For example, first and second sheets of flexible material  88  may be used to form substrates  30  and  32 , respectively, of liquid crystal cells  40 - 1 ,  40 - 2 ,  40 - 3 ,  40 - 4 ,  40 - 5 ,  40 - 6 ,  40 - 7 ,  40 - 8 ,  40 - 9 ,  40 - 10 ,  40 - 11 , and  40 - 12  of adjustable lens component  22 . By cutting flexible material  88  along the solid lines of  FIG.  14    and folding flexible material  88  along the dashed lines of  FIG.  14   , the 12 liquid crystal cells  40  may be stacked to form lens component  22 , as shown in the lower portion of  FIG.  14   . Prior to folding flexible material  88 , a single rubbing process may be performed, such that all liquid crystal cells  40  have liquid crystal alignment orientation  72  prior to folding. After being cut and folded, lens component  22  may modulate light of two polarizations, with two antiparallel liquid crystal alignment orientations for each polarization. Additionally, electrodes  38  in each of the twelve liquid crystal cells  40  may be oriented such that the twelve liquid crystal cells  40  have twelve distinct electrode orientations after lens component  22  is folded. 
     The fact that all twelve liquid crystal cells  40  share a common pair of flexible substrates may simplify electrical connections, allowing conductive traces to pass through some or all of the twelve cells to couple to pad  86  (e.g., where lens component  22  is coupled to external circuitry). If desired, angled edge  90  may be located adjacent to the bridge of a user&#39;s nose when worn by the user. 
       FIG.  15    shows another illustrative geometry that may be used for lens component  22 . As in the example of  FIG.  14   , lens component  22  of  FIG.  15    includes twelve liquid crystal cells  40 , which may include substrates  30  and  32  formed from common sheets of flexible material  88 . Flexible material  88  may be cut along the solid lines of  FIG.  15    and folded along the dashed lines of  FIG.  15    to form a stack of twelve liquid crystal cells  40 . Prior to being folded, a single rubbing process may be used so that all cells  40  initially have liquid crystal alignment orientation  72 . After being cut and folded, lens component  22  may modulate light of two polarizations, with two antiparallel liquid crystal alignment orientations for each polarization. Additionally, electrodes  38  in each of the twelve liquid crystal cells  40  may be oriented such that the twelve liquid crystal cells  40  have twelve distinct electrode orientations after lens component  22  is folded. 
     The fact that all twelve liquid crystal cells  40  share a common pair of flexible substrates may simplify electrical connections, allowing conductive traces to pass through some or all of the twelve cells to couple to pad  86  (e.g., where lens component  22  is coupled to external circuitry). In the example of  FIG.  15   , lens component  22  has first and second pads  86 . When lens component  22  is cut and folded, first and second pads  86  may be located on opposite sides of lens component  22 . Additionally, the use of first and second pads  86  helps simplify electrical connections to the twelve cells  40 . A first set of traces  96  may couple the top six cells  40  to one pad  86 , while a second set of traces  96  may couple the bottom six cells  40  to the other pad  86 . 
     The examples of  FIGS.  14  and  15    are merely illustrative. If desired, other geometries and folding arrangements may be used, and/or component  22  may include more or less than twelve liquid crystal cells  40 . 
     In arrangements where adjustable lens component  22  includes multiple liquid crystal cells  40 , it may be challenging to provide the desired control signals to finger electrodes  38 . Even when a resistive strip  54  ( FIG.  12   ) is used to distribute control signals from a control signal line  56  to multiple finger electrodes  38  (thereby allowing for fewer control signal lines  56  than finger electrodes  38 ), there still may be many control signal lines  56  for each liquid crystal cell  40 . For example, each liquid crystal cell  40  may include 100 to 200 control signal lines  56 , 200 to 300 control lines  56 , 300 to 400 control lines  56 , more than 400 control lines  56 , less than 40 control lines  56 , or other suitable number of control lines  56 . When combined with other liquid crystal cells  40 , there may be thousands (e.g., more than 3000, more than 4000, less than 4000, or other suitable number) of control lines  56  in a single adjustable lens component  22 , which may only be a few centimeters wide (e.g., 3 cm to 4 cm wide, 2 cm to 5 cm wide, more than 5 cm wide, less than 5 cm wide, etc.). 
     To reduce the number of signal paths needed from off-lens control circuitry (e.g., portions of control circuitry  26  in eyeglasses  10  that are not located on lens  22 ) to control signal lines  56  on lens component  22 , adjustable lens component  22  may include digital control circuitry and multiplexers that are used to select a desired voltage for each control signal lines  56  from a “palette” of voltages (e.g., a predetermined set of desired voltages to select from, similar to an artist&#39;s palette of colors to select from) that are generated by the off-lens control circuitry (e.g., portions of control circuitry  26  that are not physically located on lens component  22 ). The set of voltages in the voltage palette may be predetermined in the sense that the voltages are determined by the off-lens control circuitry before being conveyed to lens component  22  (e.g., via a connector such as a flexible printed circuit). However, the set of voltages in the voltage palette need not be static and may, if desired, be adjusted dynamically by the off-lens control circuitry during operation of lens  22 . 
       FIG.  16    is a top view of an illustrative lens component  22  showing how resistive strips  54  may distribute control signals from control signal lines  56  to finger electrodes  38  (e.g., patterned electrodes  38  in a given one of liquid crystal cells  40  such as liquid crystal cells  40  of  FIG.  14   ,  FIG.  15   , or any of the other previously described figures). As shown in  FIG.  16   , each resistive strip  54  follows a serpentine path, snaking back and forth between adjacent finger electrodes  38 . Each resistive strip may be coupled to 5-10 electrodes  38 , 10-15 electrodes  38 , 20-25 electrodes  38 , fewer than 20 electrodes  38 , more than 20 electrodes  38 , or other suitable number of electrodes  38 . The opposing ends of each resistive strip  54  may be coupled to a conductor such as conductor  60 . Conductor  60  may be used to supply a voltage from control signal line  56  to resistive strip  54 . Conductor  60  may be formed from metal, a transparent conductive oxide, or other suitable conductive material. 
     Some of conductors  60  may be coupled to first and second adjacent resistive strips  54 , thereby allowing for a smooth voltage profile to be provided across the finger electrodes  38  that are coupled to the first and second adjacent resistive strips  54 . For example, conductors  60 - 1 ,  60 - 2 , and  60 - 3  may be used to apply voltages to a first resistive strip  54  between conductor  60 - 1  and conductor  60 - 2  and a second resistive strip  54  between conductor  60 - 2  and conductor  60 - 3 . This allows resistive strips  54  to distribute a smooth voltage profile across electrodes  38  in region  66 . 
     It may be desirable to have the option to decouple adjacent resistive strips  54  to create an abrupt change in the phase profile across liquid crystal cell  40  when desired. This may be achieved by placing two conductors  60  between some pairs of adjacent resistive strips  54  and coupling the two conductors  60  with a switch such as switch  64 . When switch  64  is open, the resistive strips  54  on opposing sides of switch  64  may be decoupled, thereby allowing for an abrupt phase change profile in that region of liquid crystal cell  40 . When switch  64  is closed, the voltage profile will change more smoothly across the two resistive strips  54  as if there were no break between the two resistive strips  54 . Control signal lines  56 ′ may be used to provide control signals to switch  64  to thereby open and close switch  64  when desired. The use of switches  64  is merely illustrative, however. If desired, switches  64  may be omitted and there may be permanent breaks between some pairs of adjacent resistive strips  54  and/or there may be permanent electrical coupling between adjacent resistive strips  54 . 
     Control signal lines  56  and  56 ′ may have respective terminals that receive a voltage from control circuitry  26 . For example, control signal lines  56  that provide control signals to conductors  60  may each have a terminal such as terminal  62 , and control signal lines  56 ′ that provide control signals to switches  64  may each have a terminal such as terminal  68 . To reduce the number of signal lines between off-lens control circuitry and lens  22 , each terminal  62  may be coupled to a multiplexer and digital control circuitry that select a desired voltage for that terminal  62  from a palette of voltages that are generated off of lens  22  by off-lens control circuitry. This type of arrangement is illustrated in circuitry  124  of  FIG.  17   . 
     As shown in  FIG.  17   , each terminal  62  on lens component  22  may receive a voltage from a multiplexer such as multiplexer  104  that is also located on lens  22 . Multiplexer  104  may select which voltage to output to terminal  62  from a palette of voltages V 1 , V 2 , . . . VN that is generated by off-lens control circuitry such as off-lens control circuitry  122  (e.g., off-lens control circuitry that forms part of control circuitry  26  of  FIG.  1    or other off-lens control circuitry). Off-lens control circuitry  122  may include one or more digital-to-analog converter circuits such as digital-to-analog converter circuits  114  that provide analog voltages V 1 , V 2 , . . . VN on data input lines  116  to multiplexer  104  (where N is equal to the number of data input lines  116  and thus equal to the number of voltages in the voltage palette). The number of data input lines  116  may be any suitable number, depending on the number of voltages it is desired to have in the voltage palette that multiplexer  104  uses for providing voltages to terminal  62 . For example, if a palette of 40 different voltages is desired, there may be 40 different data input lines  116  to each multiplexer  104  (e.g., N may be equal to 40). This is, however, merely illustrative. If desired, N may be equal to 20, 30, 35, 45, 50, 60, 64, more than 64, less than 64, or any other suitable number. 
     The voltages V 1 , V 2 , . . . VN in the voltage palette need not be static and may, if desired, be adjusted dynamically by off-lens control circuitry  122  before being conveyed to lens  22  (e.g., via a flex circuit cable or other suitable connection between off-lens control circuitry  122  and lens component  22 ). For example, V 1  on a first data input line  116  may be equal to −V for one frame of data and may be equal to +V for a subsequent frame of data. In general, off-lens control circuitry  122  may adjust the specific voltage values in the voltage palette in any suitable fashion during operation of lens  22 . 
     Multiplexer  104  may select which one of the voltages on data input lines  116  to output on output line  112  based on control signals from digital control circuitry  108 . Digital control circuitry  108  may receive control bits on input lines  120  and may output control bits to multiplexer  104  on output lines  110 . The control bits on output line  110  may instruct multiplexer  104  which data input line  116  to select for output and/or may instruct multiplexer  104  not to couple any data input line  116  to terminal  62 . Digital control circuitry  108  may include a single shift register that is N bits wide, may include one or more decoders, may include one or more decoders that receive control bits from one or more shift registers or that receive control bits from other circuitry, and/or may include any other suitable type of digital control circuitry for providing control bits to multiplexer  104 . Because multiplexer  104  and digital control circuitry  108  may together be used to select voltages from the palette of voltages generated by off-lens control circuitry  122 , multiplexer  104  and digital control circuitry  108  may sometimes be referred to as voltage selection circuitry  128  or on-lens voltage selection circuitry  128 . If desired, multiplexer  104  may be a break-before-make multiplexer to avoid connecting two data input lines  116  together. 
       FIG.  18    is a schematic diagram of illustrative voltage selection circuitry  128 . In the example of  FIG.  18   , digital control circuitry  108  is implemented using a combination of segmented shift registers such as shift registers  106  and decoders such as decoders  102 . 
     Each shift register  106  may have any suitable number of bits (e.g., 4 bits, 6 bits, 8 bits, more than 8 bits, less than 8 bits, etc.). The structure of decoders  102  may depend on the number of bits in shift registers  106  and the number of voltages in the voltage palette (e.g., the number of data input lines  116 ). If each shift register  106  has M bits and there are N data input lines  116  (and thus N different voltages in the voltage palette), then each decoder  102  will be an M-bit to N-bit decoder. 
     Shift registers  106  may receive data signals on lines  132  and may provide enable signals on lines  130 . During operation (e.g., when it is desired to update the phase profile of lens  22 ), data signals are fed into shift registers  106  via lines  132  and the M-bit address signal may be provided to decoders  102  via enable lines  130  and output lines  134 . Each decoder  102  may decode the M-bit address signal from an associated shift register  106  to an N-bit control signal that is output to multiplexer  104  on lines  110 . In some situations, this N-bit control signal will have one high bit (e.g., one “1”) and the rest will be low bits (e.g., all “0”). Multiplexer  104  will couple one of the N data input lines  116  (e.g., the one that is addressed by the high bit in the N-bit signal received from decoder  102 ) to its output line  112 , thereby providing the desired analog voltage to terminal  62 . For example, if the first bit in the N-bit control signal from decoder  102  is high and the rest of the bits are low, multiplexer  104  may couple the first data input line  116  to output line  112  and may thereby provide analog voltage V 1  ( FIG.  17   ) to terminal  62 . In other situations, the N-bit control signal from decoder  102  may instruct multiplexer  104  not to couple any data input line  116  to terminal  62  (e.g., the control signal may be all low bits, if desired). 
     Consider a scenario in which M is equal to 6 and N is equal to 40. In this example, each shift register  104  has 6 bits, there are 40 data input lines  116 , and decoder  104  is a 6-bit to 40-bit decoder. Decoder  102  may decode each 6-bit address signal from shift register  106  to a 40-bit control signal, with  39  “0”s and 1 “1” in the 40-bit signal. This 40-bit control signal may be output on line  110  and may instruct multiplexer  104  which of the 40 data input lines  116  to select and thus which voltage (e.g., V 1 , V 2 , . . . VN of  FIG.  17   ) from the voltage palette to output to terminal  62  via output line  112 . In general, shift registers  106  may have any suitable number of bits and decoder  102  may accommodate any number of data input lines  116 . The example of a 6-bit shift register and a palette of 40 voltages is merely illustrative. 
     As shown in  FIG.  18   , shift registers  106  may include one or more single-bit shift registers for providing control signals (e.g., a high signal or a low signal) to terminals  68  for controlling the state of switches  64 . 
     In arrangements where multiplexer  104  includes analog switches formed from thin-film transistors, the thin-film transistors may have limited ability to source current. Thin-film transistors may be made wider to accommodate higher current requirements, but this may consume excessive real estate on a lens component, where space is limited. To balance this tradeoff, it may be desirable to increase the width of certain thin-film transistors in multiplexer  104  to accommodate higher current levels. In other words, the width of the thin-film transistors in multiplexer  104  that are associated with a subset of the N data input lines  116  may be larger than that of the remaining thin-film transistors in multiplexer  104 . For example, in a scenario where N is equal to 48, multiplexer  104  may include 44 standard-width transistors (or other suitable number) and  4  wide transistors (or other suitable number) that are wider than the standard-width transistors (e.g., four times as wide, three times as wide, or other suitable width). During operation, voltages with the highest anticipated current demands can be allocated to data input lines  116  that are associated with the wider transistors. This is, however, merely illustrative. If desired, all of the transistors in multiplexer  104  may have the same width, or other combinations of transistors with different widths may be used. 
     The example of  FIG.  18    is merely illustrative. If desired, voltage selection circuitry  128  may be implemented using any other type of digital circuitry that can be used to select a given voltage from a predetermined number of previously generated voltages (e.g., analog voltages generated in off-lens control circuitry  122 ). By using digital voltage selection circuitry  128  to select a desired analog voltage from a predetermined set of voltages that are generated off of lens  22 , analog circuitry on lens  22  may be reduced or eliminated, thereby freeing up valuable real estate on lens  22  and reducing the amount of signal lines needed between lens  22  and off-lens control circuitry  122 . 
     Because multiplexers tend to be weak current sources, it may be desirable to program thin-film transistor circuitry on lens  22  using active feedback from an off-lens operational amplifier to ensure that voltages provided to terminals  62  (and thus conductors  60  and variable-resistance conductive paths  54  that are coupled to terminals  62 ) match the desired voltages that are generated off-lens. An example of this type of active feedback circuitry is illustrated in  FIG.  19   . 
     Active feedback circuit  136  includes an off-lens operation amplifier such as operational amplifier  202 . Operational amplifier  202  may, for example, form part of off-lens control circuitry  122  that is located within system  10  (e.g., in housing  12 ) but that is not physically located on lens  22 . The remaining portions of active feedback circuit  136  may be located on lens  22 , if desired. 
     The positive input terminal of operation amplifier  202  may receive a selected input voltage Vin from digital-to-analog converter circuitry  200 . Digital-to-analog converter circuitry  200  may include, for example, one of digital-to-analog converter circuits  114  described in connection with  FIG.  17   , and Vin may, for example, be a selected one of the voltages V 1 , V 2 , . . . VN in the predetermined set of voltages generated off-lens (sometimes referred to as a voltage palette) and provided to lens  22  for adjusting the phase profile of lens  22 . The value of Vin may be any suitable value (e.g., Vin need not be equal to V 1 , V 2 , . . . VN, if desired) and may be generated by digital-to-analog control circuitry with any suitable number of possible outputs (e.g., N outputs, more than N outputs, or less than N outputs). 
     The output voltage Vout of circuit  136  is fed back to the inverting input of operational amplifier  202  as feedback voltage Vfb through switch SW 0 . Using feedback voltage Vfb, operational amplifier  202  may ensure that the output voltage Vout of circuit  136  matches the desired input voltage Vin. Output voltage Vout is provided to one of terminals  62  and may be varied based on the current flowing through transistor  204 . When SW 0  and SW 1  are enabled, operational amplifier  202  outputs Vg to the gate of transistor  204 . Capacitor Cg may be used to hold voltage Vg at the gate of transistor  204 . The gate voltage Vg on transistor  204  controls the amount of current flowing through transistor  204 . Transistor  204  is coupled between voltage Vout and ground voltage VSS. 
     A disable switch  206  (controlled by DISABLE signal) and switch  208  (controlled by bias voltage Vb) are coupled to Vout. When a given region of lens  22  is disabled (e.g., when it is not desired to modulate the phase profile of a given portion of lens  22 ), Vout may be shorted to VCOM via switch SW 2  and no programming is needed. Disable switch  206  may be used to turn off the active feedback so that the output voltage Vout will be equal to common voltage VCOM. If desired, disable switch  206  and switch SW 2  may be omitted (e.g., such that the value of Vout is always programmed by off-lens control circuitry  122 ). 
     It should be understood that liquid crystal material is merely an example of an electrically modulated optical material that may be modulated using electrodes  38  in cells  40 . If desired, cells  40  may include any other suitable type of electrically modulated optical material in place of the liquid crystal material in cells  40 . 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20210222
Publication Date: 20240123
Grant Date: 20240123
Priority Date: 20200304
Inventors: GILL, Patrick R.
HORIE, YU
SMITH, ERIC G.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/137", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13439", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/294", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1345", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/137", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/294", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13439", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1345", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/294", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/29", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13306", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13471", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134336", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/58", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03M1/662", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02C7/083", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02C2202/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02C2202/16", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 89578347