PATENT DOCUMENT

Publication Number: US-11086143-B1
Application Number: US-201916436784-A
Country: US
Kind Code: B1

Title: Tunable and foveated lens systems

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. The liquid crystal cells may include arrays of electrodes that extend along one, two, three, four, or more than four directions. Control circuitry may apply control signals to the array of electrodes in each liquid crystal cell to produce a desired phase profile. Each lens may be foveated such that portions of the lens within the user&#39;s gaze exhibit a different phase profile than portions of the lens outside of the user&#39;s gaze. The control circuitry may adjust the location of the optically distinct area so that it remains aligned with the user&#39;s gaze.

Claims:
What is claimed is: 
     
       1. Eyeglasses configured to be worn by a user, the eyeglasses comprising:
 control circuitry; 
 a sensor system that tracks the user&#39;s gaze; and 
 at least one adjustable lens that aligns with a respective one of the user&#39;s eyes, wherein the at least one adjustable lens comprises:
 first, second, and third layers of voltage-modulated optical material, wherein each of the first, second, and third layers of voltage-modulated optical material comprises a first portion that is within the user&#39;s gaze and a second portion that is outside of the user&#39;s gaze; and 
 first, second, and third arrays of electrodes that respectively adjust phase profiles of the first, second, and third layers of voltage-modulated optical material, wherein the first, second, and third arrays of electrodes have different orientations, and wherein the control circuitry uses information from the sensor system to control the first, second, and third arrays of electrodes to adjust a phase profile of the first portion of each of the first, second, and third layers of voltage-modulated optical material without adjusting a phase profile of the second portion of each of the first, second, and third layers of voltage-modulated optical material. 
 
 
     
     
       2. The eyeglasses defined in  claim 1  wherein the control circuitry uses the information from the sensor system to identify a first group of electrodes in the first, second, and third arrays of electrodes that are within the user&#39;s gaze and a second group of electrodes in the first, second, and third arrays of electrodes that are outside of the user&#39;s gaze, and wherein the control circuitry applies control signals to the first group of electrodes without applying control signals to the second group of electrodes. 
     
     
       3. The eyeglasses defined in  claim 1  wherein the voltage-modulated optical material in the first, second, and third layers of voltage-modulated optical material comprises liquid crystal material and wherein the electrodes in the first, second, and third arrays of electrodes comprise elongated strips of indium tin oxide. 
     
     
       4. The eyeglasses defined in  claim 3  further comprising first, second, and third common voltage electrodes, wherein the first layer of voltage-modulated optical material is interposed between the first common voltage electrode and the first array of electrodes, wherein the second layer of voltage-modulated optical material is interposed between the second common voltage electrode and the second array of electrodes, wherein the third layer of voltage-modulated optical material is interposed between the third common voltage electrode and the third array of electrodes. 
     
     
       5. The eyeglasses defined in  claim 1  further comprising:
 control signal lines that distribute control signals to the first array of electrodes. 
 
     
     
       6. The eyeglasses defined in  claim 5  further comprising:
 first and second transparent substrates on opposing sides of the first layer of voltage-modulated optical material; and 
 a strip of conductive material formed along an edge of the first substrate, wherein the strip of conductive material has a distributed resistance. 
 
     
     
       7. The eyeglasses defined in  claim 6  wherein the strip of conductive material is electrically coupled between the control signal lines and the first array of electrodes. 
     
     
       8. The eyeglasses defined in  claim 7  wherein the first array of electrodes has a first pitch and wherein the control signal lines have a second pitch that is larger than the first pitch. 
     
     
       9. The eyeglasses defined in  claim 1  wherein the first array of electrodes comprises top and bottom electrodes separated by an insulator and wherein the top electrodes are staggered relative to the bottom electrodes. 
     
     
       10. The eyeglasses defined in  claim 9  wherein the control circuitry applies control signals to the top and bottom electrodes. 
     
     
       11. The eyeglasses defined in  claim 9  wherein the top electrodes are floating electrodes and the control circuitry applies the control signals to the bottom electrodes. 
     
     
       12. Eyeglasses configured to be worn by a user, comprising:
 control circuitry; and 
 at least one adjustable lens that aligns with a respective one of the user&#39;s eyes, wherein the at least one adjustable lens comprises:
 a first liquid crystal module having a first array of electrodes oriented along a first direction; 
 a second liquid crystal module having a second array of electrodes oriented along a second direction; and 
 a third liquid crystal module having a third array of electrodes oriented along a third direction, wherein the first, second, and third directions are different. 
 
 
     
     
       13. The eyeglasses defined in  claim 12  wherein each of the first, second, and third liquid crystal modules comprise:
 a first liquid crystal cell having a first liquid crystal alignment orientation; and 
 a second liquid crystal cell having a second liquid crystal alignment orientation that is antiparallel to the first liquid crystal alignment orientation. 
 
     
     
       14. The eyeglasses defined in  claim 12  further comprising a sensor system that tracks a user&#39;s gaze, wherein the at least one adjustable lens comprises:
 a first region having a first optical power; and 
 a second region having a second optical power that is lower in magnitude than the first optical power, wherein the control circuitry adjusts a location of the first region so that it remains aligned with the user&#39;s gaze. 
 
     
     
       15. The eyeglasses defined in  claim 14  wherein the first region has a diameter between 4 mm and 9 mm. 
     
     
       16. Eyeglasses configured to be worn by a user, comprising:
 control circuitry; and 
 at least one adjustable lens that aligns with a respective one of the user&#39;s eyes, wherein the at least one adjustable lens comprises:
 first, second, and third liquid crystal layers; and 
 first, second, and third arrays of electrodes having different orientations, wherein the control circuitry applies first control signals to the first array of electrodes to adjust a phase profile of the first liquid crystal layer, applies second control signals to the second array of electrodes to adjust a phase profile of the second liquid crystal layer, and applies third control signals to the third array of electrodes to adjust a phase profile of the third liquid crystal layer. 
 
 
     
     
       17. The eyeglasses defined in  claim 16  further comprising:
 control signal lines that distribute control signals to the first array of electrodes, wherein the first array of electrodes have a first pitch and wherein the control signal lines have a second pitch that is larger than the first pitch; and 
 a conductive line coupled between the control signal lines and the first array of electrodes, wherein the conductive line has a distributed resistance that defines a voltage value received by each of the electrodes in the first array of electrodes. 
 
     
     
       18. The eyeglasses defined in  claim 16  wherein the first array of electrodes comprises top electrodes and bottom electrodes, wherein the top electrodes overlap gaps between the bottom electrodes, and wherein the bottom electrodes overlap gaps between the top electrodes. 
     
     
       19. The eyeglasses defined in  claim 16  further comprising:
 a sensor system that tracks a location of the user&#39;s gaze, wherein the first, second, and third control signals are based on the location of the user&#39;s gaze. 
 
     
     
       20. The eyeglasses defined in  claim 19  wherein the control circuitry applies the first control signals to a first subset of the first array of electrodes to adjust the phase profile of only a first portion of the first liquid crystal layer, applies the second control signals to a second subset of the second array of electrodes to adjust the phase profile of only a second portion of the second liquid crystal layer, and applies the third control signals to a third subset of the third array of electrodes to adjust the phase profile of only a third portion of the third liquid crystal layer.

Description:
This application claims the benefit of provisional patent application No. 62/683,520, filed Jun. 11, 2018, 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. 
     In some arrangements, each adjustable lens may include three or six liquid crystal cells, each having an associated array of electrodes. The electrodes in the liquid crystal cells may be oriented along three different directions. If desired, arrangements with fewer than three or more than three directions may be used. 
     The adjustable lenses may be foveated such that the liquid crystal within the user&#39;s gaze is controlled to exhibit a different optical power than the liquid crystal outside of the user&#39;s gaze. The control circuitry may track the user&#39;s gaze with a sensor system and may adjust the location of the optically distinct area of the adjustable lenses so that it remains aligned with the user&#39;s gaze. 
     Such optical powers can be helpful to users exhibiting presbyopia, a condition whereby the user&#39;s eyes are no longer able to adjust their focal power to bring into focus objects at significantly different distances. Glasses able to compute the deficiency in the user&#39;s accommodation can correct for this deficiency through applying distinct optical power. Limiting the spatial extent of the differing optical power can reduce disorienting visual sensations caused by changes in magnification applied to images of the world as seen through the glasses. 
     Further, a user&#39;s eyes may exhibit static or focus-dependent optical defects known as “higher-order aberrations” that are not in general correctable by any static prescription, but can be partially or completely correctable by the portion of variable phase that follows a user&#39;s gaze. 
     In some arrangements, adjustable lenses may include one or more liquid crystal modules each having first and second liquid crystal cells. The first liquid crystal cell may have a liquid crystal layer with a first liquid crystal alignment orientation and the second liquid crystal cell may have a liquid crystal layer with a second liquid crystal alignment orientation that is antiparallel to the liquid crystal alignment orientation. 
     The adjustable lenses may have transparent electrodes such as high aspect ratio indium tin oxide electrodes that are supplied with control signals by the control circuitry. Control signal lines may be used to distribute the control signals to the electrodes. The electrodes may have a first pitch, and the control signal lines may have a second pitch that is larger than the first pitch. A conductive strip or serpentine path having a resistance that varies along its length may be coupled between the control signal lines and the electrodes. The voltage value received by a given one of the electrodes may be determined at least partly based on a weighted average of the voltages at the two nearest signal lines, the weights being determined by the relative proximities of the signal lines. This permits spatially continuous high spatial resolution signals using a coarser grid of applied control signals. 
     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 cross-sectional side view of an illustrative liquid crystal cell having staggered top and bottom electrodes that are driven with common control signals in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of an illustrative liquid crystal cell having staggered top and bottom electrodes, where the top electrodes are floating electrodes and the bottom electrodes are driven with control signals, in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative liquid crystal cell having staggered top and bottom electrodes that are driven independently of one another in accordance with an embodiment. 
         FIG. 17  is a cross-sectional side view of illustrative adjustable lens components having adjustable lenses that compensate for lens tilt in a fixed lens in accordance with an embodiment. 
         FIG. 18  is a cross-sectional side view of illustrative adjustable lens components having adjustable lenses stacked with a fixed lens in accordance with an embodiment. 
         FIG. 19  is a perspective view of an illustrative adjustable lens component with multiple liquid crystal cells each having a unique electrode orientation in accordance with an embodiment. 
         FIG. 20  is a top view of illustrative liquid crystal cells in an adjustable lens component that modulate different polarization angles in accordance with an embodiment. 
         FIG. 21  is a top view of an illustrative liquid crystal cell having a first liquid crystal alignment orientation to modulate light of a first polarization angle in accordance with an embodiment. 
         FIG. 22  is a top view of an illustrative liquid crystal cell having a second liquid crystal alignment orientation to modulate light of the first polarization angle in accordance with an embodiment. 
         FIG. 23  is a top view of an illustrative liquid crystal cell having a first liquid crystal alignment orientation to modulate light of a second polarization angle in accordance with an embodiment. 
         FIG. 24  is a top view of an illustrative liquid crystal cell having a second liquid crystal alignment orientation to modulate light of a second polarization angle in accordance with an embodiment. 
         FIG. 25  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. 26  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. 27  is a cross-sectional side view of an illustrative adjustable lens component in which multiple liquid crystal cells share a pair of flexible substrates that are laminated together in accordance with an embodiment. 
         FIG. 28  is a top view of an illustrative liquid crystal cell having a slightly distorted electrode pattern to reduce visibility of artifacts arising from unwanted diffraction 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 ). 
     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) 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. 
       FIGS. 14, 15, and 16  show other ways of mitigating optical effects that may arise from the existence of gaps between finger electrodes  38 . 
     As shown in  FIG. 14 , finger electrodes  38  include top finger electrodes  38 T and bottom finger electrodes  38 B. An insulating layer such as insulator  60  (e.g., a layer of inorganic material such as silicon nitride or other suitable material) may be interposed between top electrodes  38 T and bottom electrodes  38 B. Electrodes  38 T and  38 B may be staggered relative to one another such that gaps between top electrodes  38 T are overlapped by bottom electrodes  38 B, and gaps between bottom electrodes  38 B are overlapped by top electrodes  38 T. In the example of  FIG. 14 , both top electrodes  38 T and bottom electrodes  38 B are controlled together using the same control signal via conductive path  58 . 
     In the example of  FIG. 15 , top electrodes  38 T are staggered relative to bottom electrodes  38 B, but only one set of electrodes is driven and the other set is left floating. For example, top electrodes  38 T may be floating electrodes (e.g., not electrically connected to a voltage supply), and bottom electrodes  38 B may be driven using control signals via conductive path  58 . In the configuration of  FIG. 15 , insulator  60  may be chosen such that it is slightly conductive such that any static charge that accumulates on top electrodes  38 T has a high-resistance path to ground. 
     In the example of  FIG. 16 , top electrodes  38 T and bottom electrodes  38 B are independently controlled. Top electrodes  38 T may be driven with control signals via conductive path  58 T, whereas bottom electrodes  38 B may be driven with control signals via conductive path  58 B. 
     If desired, adjustable lens components may be stacked with fixed lens components. As shown in  FIG. 17 , for example, adjustable lens component  22  may include first lens  22 - 1 , second lens  22 - 2 , and third lens  22 - 3 . Lenses  22 - 1  and  22 - 2  may be adjustable lens components each having a structure of the type described in connection with  FIGS. 1-16 . Lens  22 - 3  may be a fixed lens component. This type of arrangement may be used to modify the overall optical power of lens components  22 . For example, adjustable lenses  22 - 1  and  22 - 2  may each have a lens power ranging from −1 diopter to +1 diopter and fixed lens  22 - 3  may be a fixed corrector optic having a lens power of +2 diopter. Combinations of fixed correctors can also serve to reduce the angle of traversal of light through the adjustable lens component, which may perform better when angles of traversal are closer to the normal axis. In this example, the combined optical power of lens component  22  would be 0 diopter to +4 diopter. This is merely illustrative, however. In general, any suitable number of adjustable lens components may be combined with any suitable fixed lens optic to achieve the desired lens power range. 
     If desired, adjustable lens component  22  may be used in conjunction with a progressive lens. This type of arrangement may serve to reduce the optical power needed from adjustable lens component  22 . 
     In arrangements of the type shown in  FIG. 17  where adjustable lens components  22  include both adjustable and fixed lenses, the adjustable lenses may be used to compensate for aberrations associated with fixed lens  22 - 3 , such as lens tilt. As shown in  FIG. 17 , for example, a viewer&#39;s eyes  16  may view objects in direction  62 , which is offset from optical axis  60  of fixed lens  22 - 3 , causing lens tilt (e.g., an effect in which the position of the focal point shifts). Control circuitry  26  may be configured to adjust the centers and phase profiles of adjustable lenses  22 - 1  and  22 - 2  to compensate for the lens tilt aberration of fixed lens  22 - 3 . 
     In the example of  FIG. 18 , control circuitry  26  may detect that the user&#39;s gaze is aligned with optical axis  60  of fixed lens  22 - 3 , so no tilt correction may be needed from adjustable lenses  22 - 1  and  22 - 2 . 
     If desired, adjustable lens components  22  may be configured to zoom (e.g., magnify). For example, control circuitry  26  may adjust the phase profile of adjustable lens  22 - 1  to mimic a concave lens and may adjust the phase profile of adjustable lens  22 - 2  to mimic a convex lens. The convex lens may converge light rays onto the concave lens, which then spreads the rays out to create a magnified image for the user&#39;s eyes  16 . 
     If desired, adjustable lens components  22  may include multiple liquid crystal cells  40 . In general, a greater number of liquid crystal cells  40  in adjustable lens component  22  will lead to greater variable phase depth, the ability to correct higher-order aberrations, and the ability to modulate multiple polarization angles. Greater variable phase depth may in turn allow for a greater dioptric range and the ability to control a larger gaze area  46  using a smaller voltage range. 
     As described in connection with  FIGS. 6 and 7 , the use of multiple liquid crystal cells  40  in adjustable lens components  22  allows for multiple orientations of electrodes (e.g., finger electrodes  38 ). In general, a greater number of electrode orientations will allow lens component  22  to correct more higher-order aberrations using a smaller voltage range. 
     In some arrangements, each liquid crystal cell  40  in an adjustable lens component  22  may have a different electrode orientation. When no two liquid crystal cells  40  in lens component  22  share the same electrode orientation, incidental refractive effects radiating from the actively controlled gaze region  46  may be more spread out and therefore less perceivable to the user. 
       FIG. 19  shows an example of an illustrative adjustable lens component  22  with multiple unique electrode orientations. As shown in  FIG. 19 , adjustable lens component  22  may include multiple liquid crystal cells  40 . Each liquid crystal cell  40  may include finger electrodes  38  with a given orientation. The orientation of electrodes  38  in each cell  40  may be different from the orientation of electrodes  38  of every other cell  40  in lens component  22 . 
     If desired, the orientation of electrodes  38  in each cell  40  may, if desired, be offset from the liquid crystal alignment orientation (e.g., liquid crystal alignment orientation  72 ) of liquid crystal layer  34  in cell  40 . In particular, electrodes  38  may be oriented at an angle θ (e.g., a non-zero angle) relative to liquid crystal alignment orientation  72 . It may also be beneficial to ensure that electrodes  38  are oriented at angles θ other than 90 degrees relative to the liquid crystal alignment orientation of liquid crystal layer  34 . Avoiding zero degree and 90 degree angles between electrodes  38  and liquid crystal alignment orientation  72  may ensure that liquid crystal molecules twist uniformly in a particular direction in response to an applied electric field (rather than some liquid crystal molecules twisting in one direction while other liquid crystal molecules twist in a different direction, which can result in visual artifacts at the boundaries between the two twist directions). This is merely illustrative, however. If desired, electrodes  38  may be oriented at 0 degrees or 90 degrees relative to liquid crystal alignment orientation  72 . 
     In some arrangements, adjustable lens components  22  may be used to modulate different linear polarizations. As shown in  FIG. 20 , for example, one or more liquid crystal cells  40  in lens component  22  may modulate light of a first polarization  70 A, and one or more liquid crystal cells in lens component  22  may modulate light of a second polarization  70 B. In one illustrative example, first polarization  70 A may be angled at 135 degrees relative to the X-axis of  FIG. 20  and second polarization  70 B may be angled at 45 degrees relative to the X-axis of  FIG. 20 . With this arrangement, horizontally and vertically polarized light (e.g., light emitted from liquid crystal displays) may be equally modulated by each pair of liquid crystal cells  40  containing polarization  70 A and polarization  70 B. This is, however, merely illustrative. If desired, lens component  22  may modulate more than two polarizations, may modulate only one polarization, and/or may modulate other polarization angles (e.g., in addition to or instead of the polarization angles of  FIG. 20 ). Arrangements in which lens component  22  modulates polarization  70 A and polarization  70 B are sometimes described herein as an illustrative example. 
     The polarization modulated by a given liquid crystal cell  40  may be determined by its liquid crystal alignment orientation. To modulate polarization  70 A, liquid crystal cell  40  may have liquid crystal alignment orientation  72 A 1  of  FIG. 21  (e.g., a liquid crystal alignment orientation oriented at 135 degrees relative to the X-axis of  FIG. 21 ) or liquid crystal alignment orientation  72 A 2  of  FIG. 22  (e.g., a liquid crystal alignment orientation antiparallel to liquid crystal alignment orientation  72 A 1 ). To modulate polarization  70 B, liquid crystal cell  40  may have liquid crystal alignment orientation  72 B 1  of  FIG. 23  (e.g., a liquid crystal alignment orientation oriented at 45 degrees relative to the X-axis of  FIG. 23 ) or liquid crystal alignment orientation  72 B 2  of  FIG. 24  (e.g., a liquid crystal alignment orientation antiparallel to liquid crystal alignment orientation  72 B 1 ). 
     In arrangements where adjustable lens component  22  of the type shown in  FIG. 20  modulates multiple polarizations (e.g., polarizations  70 A and  70 B of  FIG. 20 ), it may be desirable to alternate between polarizations from one liquid crystal cell to the next. It may also be desirable to alternate between liquid crystal alignment orientations. 
     For example, in arrangements where component  22  of  FIG. 19  includes eight liquid crystal cells  40 , the top cell  40  may modulate polarization  70 A, may have liquid crystal alignment orientation  72 A 1 , and may have electrodes  38  oriented at 11.25° relative to liquid crystal alignment orientation  72 A 1 ; the second cell  40  may modulate polarization  70 B, may have liquid crystal alignment orientation  72 B 1 , and may have electrodes  38  oriented at 33.75° relative to liquid crystal alignment orientation  72 A 1 ; the third cell  40  may modulate polarization  70 A, may have liquid crystal alignment orientation  72 A 2 , and may have electrodes  38  oriented at 56.25° relative to liquid crystal alignment orientation  72 A 1 ; the fourth cell  40  may modulate polarization  70 B, may have liquid crystal alignment orientation  72 B 2 , and may have electrodes  38  oriented at 78.75° relative to liquid crystal alignment orientation  72 A 1 ; the fifth cell  40  may modulate polarization  70 A, may have liquid crystal alignment orientation  72 A 1 , and may have electrodes  38  oriented at 101.25° relative to liquid crystal alignment orientation  72 A 1 ; the sixth cell  40  may modulate polarization  70 B, may have liquid crystal alignment orientation  72 B 1 , and may have electrodes  38  oriented at 123.75° relative to liquid crystal alignment orientation  72 A 1 ; the seventh cell  40  may modulate polarization  70 A, may have liquid crystal alignment orientation  72 A 2 , and may have electrodes  38  oriented at 146.25° relative to liquid crystal alignment orientation  72 A 1 ; and the eighth cell  40  may modulate polarization  70 B, may have liquid crystal alignment orientation  72 B 2 , and may have electrodes  38  oriented at 168.75° relative to liquid crystal alignment orientation  72 A 1 . 
     The use of an even number of liquid crystal cells  40  for each polarization state may permit equal complements of the two antiparallel liquid crystal alignment orientations modulating a particular polarization. For example, in the eight-cell example just described, the first and fifth cell pair (with liquid crystal alignment orientation  72 A 1  and modulating polarization angle  70 A) and the third and seventh cell pair (with liquid crystal alignment orientation  72 A 2  and modulating polarization angle  70 A) are each individually able to express spherical power where they intersect. This in turn allows component  22  to express a variable fraction of the spherical power preferentially in either of the two antiparallel liquid crystal alignment orientations (which may be useful in situations where the viewing angle is such that one liquid crystal alignment orientation performs better than the other antiparallel liquid crystal alignment orientation). 
     The eight-cell example is merely illustrative. If desired, there may be greater or fewer than eight liquid crystal cells  40  in lens component  22 . The same principals of evenly spaced electrode orientations, alternating polarizations from one cell to the next, and alternating liquid crystal alignment orientations may be applied, if desired. In the eight-cell example, the eight orientations of electrodes  38  are evenly spaced at 22.5° intervals. In a lens component  22  with 4N liquid crystal cells  40 , the angular spacing between electrode orientations may be 180°/(4N). If N is greater than two, then each antiparallel liquid crystal alignment orientation may be able to express spherical power in the actively controlled gaze region  46 . Each of two linear polarizations may be modulated by 2N cells, with an equal and alternating selection from the two possible antiparallel liquid crystal alignment orientations that modulate that polarization. In the eight-cell example described above, N=2. If desired, N may be 3, 6, or any other suitable number). 
     In arrangements where lens component  22  only modulates one linear polarization, only 2N liquid crystal cells  40  may be needed, the angular spacing between electrode orientations may be 180°/(2N), and cells can alternate between the two antiparallel liquid crystal alignment orientations for that polarization. These examples are merely illustrative, however. If desired, other arrangements and combinations of polarizations, liquid crystal alignment orientations, and electrode orientations may be used. 
     For example, lens component  22  may have 12 liquid crystal cells  40  and may modulate two polarizations (e.g., lens component  22  may have 4N liquid crystal cells  40  where N=3). In another suitable arrangement, lens component  22  may have 12 liquid crystal cells  40  and may modulate one polarization (e.g., lens component  22  may have 2N liquid crystal cells  40  where N=6). In these examples, the angular spacing between the electrode orientations may be 15° or other suitable angle. If desired a minimum angle (e.g., 7.5° or other suitable angle) between any liquid crystal alignment orientation and any electrode orientation may be imposed to avoid nonuniform twisting of liquid crystal molecules. 
     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. 25  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. 25  and folding flexible material  88  along the dashed lines of  FIG. 25 , the 12 liquid crystal cells  40  may be stacked to form lens component  22 , as shown in the lower portion of  FIG. 25 . 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 (e.g., polarizations  70 A and  70 B of  FIG. 20 ), 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. 26  shows another illustrative geometry that may be used for lens component  22 . As in the example of  FIG. 25 , lens component  22  of  FIG. 26  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. 26  and folded along the dashed lines of  FIG. 26  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 (e.g., polarizations  70 A and  70 B of  FIG. 20 ), 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. 26 , 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. 25 and 26  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 . 
       FIG. 27  is a cross-sectional side view of an illustrative lens component  22  showing how a pair of liquid crystal cells  40  may share substrates formed from sheets of flexible material  88 . As shown in  FIG. 27 , liquid crystal cell  40 - 1  and liquid crystal cell  40 - 2  each have substrates  30  and  32 . Substrate  30  and/or substrate  32  may be formed form a common sheet of flexible material  88  that is shared between liquid crystal cell  40 - 1  and liquid crystal cell  40 - 2 . The sheets of flexible material  88  may have a bend region  84  between the two liquid crystal cells. If desired, a minimum bend radius R may be imposed to reduce the mechanical stress on signal lines in bend region  88 . To provide additional mechanical stability to lens component  22 , an adhesive layer such as optically clear adhesive  82  may be used to laminate adjacent liquid crystal cells  40 - 1  and  40 - 2 . If desired, liquid crystal cells  40  in lens component  22  may be planar (as shown in the example of  FIG. 27 ), or liquid crystal cells  40  may be curved. 
     In some arrangements, finger electrodes  38  in a given liquid crystal cell  40  may be strictly parallel to one another. In other arrangements, finger electrodes  38  may follow slightly distorted paths (e.g., paths that are not strictly parallel to one another). An example of this type of arrangement is illustrated in  FIG. 28 . As shown in  FIG. 28 , electrodes  38  may deviate from a strictly parallel arrangement (e.g., electrodes  38  may have slightly different angles relative to the X-axis of  FIG. 28 ). This type of arrangement may help reduce the visibility of artifacts that can arise from unwanted diffraction of light passing through liquid crystal cell  40 . If desired, the deviation of electrodes  38  (e.g., the angle between any one electrode  38  in cell  40  and any other electrode  38  in cell  40 ) may be smaller than the difference between the angle of electrodes  38  and liquid crystal alignment orientation  72 , which may help avoid discontinuities in the twist direction of liquid crystal molecules in cell  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: 20190610
Publication Date: 20210810
Grant Date: 20210810
Priority Date: 20180611
Inventors: GILL, Patrick R.
KANGAS, Miikka M.
KOLLER, JEFFREY G.
Miles, Alexander A.
HORIE, YU
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/13471", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13306", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02C2202/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02C7/083", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02C7/081", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133345", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133526", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1343", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1337", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133526", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02C7/081", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133345", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1343", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1337", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 77179065