Patent Publication Number: US-11662642-B2

Title: Electro-active lenses with raised resistive bridges

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 17/336,792, filed on Jun. 2, 2021, which is a continuation application of U.S. application Ser. No. 16/798,553, filed on Feb. 24, 2020, which is a continuation application of U.S. application Ser. No. 15/431,686, now U.S. Pat. No. 10,599,006, filed on Feb. 13, 2017, which is a bypass continuation application of International Application No. PCT/US2016/060784, filed on Nov. 7, 2016, and entitled “ELECTRO-ACTIVE LENSES WITH RAISED RESISTIVE BRIDGES,” which in turn claims the priority benefit of U.S. Application No. 62/321,501, which was filed on Apr. 12, 2016. Each of these applications is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Electro-active lenses can be made by several methods, including patterning a series of concentric electrodes of conductive material on a first substrate, then sandwiching a layer of liquid crystal between the first substrate and second substrate opposite the first substrate. The second substrate may have one or more circular patterns of conductive material patterned on it, or any other shape to match or exceed the area of the patterned electrodes, allowing an electrical circuit to be formed that creates a voltage field between the two substrates. When an electrical field is applied across the electrodes, the liquid crystal material between the two substrates changes its index of refraction. 
     By applying a gradient of voltage fields at different electrode locations on the lens, a gradient of index of refraction may be created, creating a lens. The higher the number of electrodes that are used, the finer the resolution of gradient of refractive index can be created. This results in a smoother wavefront curvature, and hence provides a better quality optic. 
     However, increasing the number the electrodes also increases the complexity of the electronics as well as the light-blocking elements that supply power to the electrodes, so methods have been developed to allow a small number of power supply lines to apply a voltage gradient across a larger number of electrodes. In particular, N power supply lines can be used to apply a voltage gradient across M&gt;N electrodes with resistive bridges between the electrodes. In these electro-active lenses, every M/Nth electrode is connected to a power supply line, and the other electrodes are coupled to each other with resistive bridges. 
     In conventional electro-active lenses with resistive bridges, the resistive bridges are made in such a manner that the electrode ring is no longer continuous, degrading optical quality. The problem can be partially solved by fabricating the resistive bridges in the same plane as the electrodes, locating the resistors in between adjacent electrodes. In some cases, there are additional shortcomings, including the use of extremely high resistive materials, which are difficult to manufacture in a controllable manner, and the need to fill the entire gap between electrodes with resistive material is required to fill a large area. In general, it is desirable to reduce the gap between electrodes to improve optical performance, but this can exacerbate the difficulty of manufacturing the resistive components. 
     SUMMARY 
     The inventors have recognized that prior-art solutions to the problem of reducing the complexity of the drive channels in electro-active lenses have introduced a new problem: excessive power consumption of the electro-active lenses. Without resistive bridges, a typical lens design may consume only nano-amperes of electrical current. However, the resistive bridges provide a pathway for the electrical current to flow from one drive channel to the others. This extra current flow leads to an undesired increase in the power consumption of the electro-active lens. 
     The inventors have recognized that increasing the resistance of the resistive bridges reduces this increased power consumption. In some cases, the resistance can be increased by increasing the resistor&#39;s size. But fitting the larger resistor into the same plane as the electrodes means that the gaps between the electrodes must be larger, the electrodes must be interrupted, or both for the larger resistor to fit. 
     Unfortunately, creating a larger, high resistance bridge in such a small space very difficult. In addition, interruptions in the electrodes gaps degrade the lens&#39;s optical performance: etching away a portion of the electrode to make space for the resistive bridge degrades the integrity of the electrodes and hence the optical performance of the lens. To further compound the problem, the gap between electrodes is a dimension that should be reduced as much as possible in order to reduce effects that degrade optical performance, further increasing the challenge of increasing the resistance of the resistance bridges. 
     Fortunately, the present technology addresses these problems by providing larger, higher resistance bridges that do not degrade the lens&#39;s optical performance. In these designs, the electrodes can remain continuous and close together. In addition, there is no need to remove or sacrifice surface area from the electrodes to make room for the resistive bridges. 
     Embodiments of the present technology include an electro-optic lens comprising a first substantially transparent substrate, a plurality of electrodes disposed on a surface of the first substantially transparent substrate, an insulating layer disposed on the plurality of electrodes, and a resistive bridge disposed on the insulating layer. The resistive bridge connects a first electrode in the plurality of electrodes with a second electrode in the plurality of electrodes via holes patterned into the insulating layer. In operation, applying a voltage to the first electrode via the resistive bridge causes an electro-active material, such as (bi-stable) liquid crystal, to change its refractive index. 
     The plurality of electrodes may comprise a plurality of concentric ring electrodes, with the first electrode being a first concentric ring electrode and the second electrode being a second concentric ring electrode. In these cases, the first concentric ring electrode can have a constant width. 
     The plurality of electrodes may be formed a first material having a first sheet resistance and the resistive bridge may be formed of a second material having a second sheet resistance higher than the first sheet resistance. 
     There may be insulating material disposed between the first electrode and the second electrode. This insulating layer may span a gap between the first electrode and the second electrode of less than about 3 microns. 
     The resistive bridge can have a resistance of at least about 2.5 MΩ and a length-to-width ratio of about 25:1. The resistive bridge may include nickel, chromium, indium tin oxide, resistive polymer (e.g., PEDOT:PSS), or any combination or alloy thereof. 
     The resistive bridge can comprise a plurality of resistive segments, with each resistive segment in the plurality of resistive segments being in electrical communication with a corresponding pair of electrodes in the plurality of electrodes. The plurality of resistive segments can include a first resistive segment with a first width and a second resistive segment with a second width greater than the first width. The plurality of resistive segments can also include a first resistive segment with a first length and a second resistive segment with a second length greater than the first length. And at least one resistive segment in the plurality of resistive segments may have a curved or bent edge. 
     Embodiments of the present technology also include a method of making an electro-optic lens. In one example of this method, a plurality of electrodes is formed on a substrate. A layer of insulating material is deposited on the electrodes. Next, a plurality of through holes is formed in the layer of insulating material. Each through hole in the plurality of through holes connects to a corresponding electrode in the plurality of electrodes. A resistive material is deposited on the layer of insulating material and in the plurality of through holes. And the resistive material is patterned to form a plurality of resistors. Each resistor in the plurality of resistors connects to a corresponding electrode in the plurality of electrodes. Optionally, a buss line can be formed in electrical communication with the electrodes and resistors. 
     In some cases, forming the plurality of electrodes comprises forming a plurality of concentric ring electrodes. In these cases, forming the plurality of concentric ring electrodes may comprise forming a first concentric ring electrode separated from a second concentric ring electrode by a gap of less than about 3 microns. Each concentric ring electrode may have a constant width (with the widths being the same or different among the concentric ring electrodes). 
     The resistive material may have a sheet resistance higher than a sheet resistance of the plurality of electrodes. It may be patterned to form at least one resistor having a resistance of at least about 2.5 MΩ, at least one resistor having a length-to-width ratio of about 25:1, or both. In some cases, there may be a first resistor with a first width and a second resistor segment with a second width greater than the first width. Likewise, there may be a first resistor with a first length and a second resistor with a second length greater than the first length. The resistive material may be patterned to form at least one resistor with a curved edge. 
     Another embodiment includes an electro-active contact lens with a base optical element and an electro-active element embedded within the base optical element. The electro-active element includes a plurality of electrodes, an insulating layer disposed on the plurality of electrodes, and a resistive bridge disposed on the insulating layer. The resistive bridge connects a first electrode in the plurality of electrodes with a second electrode in the plurality of electrodes via holes patterned into the insulating layer. 
     It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements). 
         FIG.  1    shows an electro-active lens without resistive bridges between electrodes. 
         FIG.  2 A  shows the electrodes in the electro-active lens of  FIG.  1    without the electrical connections that supply power to the electrodes. 
         FIG.  2 B  shows the electrodes of  FIGS.  1  and  2 A  with buss lines added. 
         FIG.  3    shows an electrical schematic of an electro-active lens without resistive bridges. 
         FIG.  4    shows an electrical current flow through each of the drive channels for the electro-active lens shown in  FIG.  3   . 
         FIG.  5 A  shows a plan view of an electro-active lens with in-plane resistive bridges. 
         FIG.  5 B  shows a schematic of an electro-active lens with resistive bridges R 1  through R 9 . 
         FIG.  6    shows a typical electrical current flow through each of the drive channels for the electro-active lens shown in  FIG.  5   . 
         FIG.  7    shows an electro-active lens with 100 kΩ resistive bridges R 1  through R 9 . 
         FIG.  8    shows a current flow of the electro-active lens shown in  FIG.  7   . 
         FIG.  9    shows an electro-active lens with 2.5 MΩ resistive bridges. 
         FIG.  10    shows a typical electrical current flow through each of the drive channels for the electro-active lens shown in  FIG.  9   . 
         FIG.  11    shows a cross section of an electro-active lens with raised resistive bridges. 
         FIGS.  12 A- 12 C  show different views of the electrodes, resistors, and buss lines of the electro-active lens of  FIG.  11   . 
         FIG.  12 D  shows a raised resistive bridge with curved bridge segments. 
         FIG.  12 E  shows a raised resistive bridge with bridge segments having variable widths. 
         FIG.  13    shows an electro-active contact lens with raised resistive bridges. 
         FIG.  14    shows a process for making an electro-active lens with resistive bridges disposed on an insulating layer above an electrode layer. 
     
    
    
     DETAILED DESCRIPTION 
     This application discloses electro-active lenses, including electro-active contact lenses and electro-active intraocular lenses, with electrodes connected with raised resistive bridges. For instance, the resistive bridges can be disposed on an insulating layer about the electrodes. Placing the resistive bridges and electrodes on opposite sides of an insulating layer offers many advantages over electro-active lenses without resistive bridges and electro-active lenses with conventional resistive bridges. Compared to an electro-active lens without resistive bridges, an electro-active lens with raised resistive bridges can support more electrodes with fewer buss lines. And compared to an electro-active lens with conventional resistive bridges, an electro-active lens with raised resistive bridges can support ring electrodes that are both continuous and closer together because the resistors aren&#39;t disposed between the ring electrodes. Continuous, closely spaced electrodes offer better optical performance than discontinuous or widely spaced electrodes. 
     A raised resistive bridge can be larger too, which means that it is less likely to break when flexed due its larger surface area. A larger raised resistive bridge also has higher resistance and lower power consumption as explained below. In a contact lens or intraocular lens, low power consumption is especially beneficial because of limited available power in such a small device and its subsequently small size battery of power storage device. These raised resistive bridges enable lower power consumption while preserving the optical capabilities that the device&#39;s design provides. 
     In addition, an electro-active lens with raised resistive bridges can be fabricated more easily than an electro-active lens with conventional resistive bridges because raised resistive bridges don&#39;t have to be as precisely sized, shaped, or positioned as conventional resistive bridges. Put differently, a raised resistive bridge can be made with coarser resolution features because it goes over the electrodes and is not part of the optical area. As a result, an electro-active lens with raised resistive bridges can be made using simpler lithography or inkjet printing on flexible surfaces. And because it is on a different level than the electrodes, a raised resistive bridge can also be made from different materials than the electrodes. For instance, the electrodes may be made from a conductive, transparent material, such as indium tin oxide (ITO), and the raised resistive bridge may be made of a material with a higher resistivity than ITO. 
     Electro-Active Lenses without Resistive Bridges 
       FIG.  1    shows an exploded, perspective view of an electro-active lens  100  without resistive bridges. The electro-active lens  100  includes a lower substrate  110  patterned with a set of concentric ring electrodes  205  and conductive connection pads  115 . Conductive buss lines  210  connect respective electrodes  205  with respective conductive connection pads  115 . The electrodes  205 , buss lines  220 , and connection pads  115  may be formed of a transparent conductive material, such as indium tin oxide (ITO), that is deposited onto the lower substrate  110  and patterned using standard lithographic techniques. An upper substrate  130  forms the other half of the lens  110 . The underside of the upper substrate  130  is coated with a layer of transparent conductive material that acts as another electrode (e.g., a ground plane  135 ). A layer of liquid crystal material  120  is sandwiched between the upper substrate  130  and the lower substrate  120  to form the lens  110 . 
     In operation, the individually controllable voltage at each buss line  220  may be utilized to modulate the refractive index of the liquid crystal material  120  between the corresponding ring electrode  220  and the ground plane  135 . For instances, the voltages applied to the buss lines  220  may be selected to generate spherical wave front when the lens  100  is positioned in the path of a plane wave. The voltages may also be selected to deviate from a sphere-only wave front. Such a deviation may be useful in correcting higher order aberrations, one example being spherical aberration. 
       FIGS.  2 A and  2 B  show the concentric circular electrodes  205  of the electro-active lens  100  of  FIG.  1    in greater detail.  FIG.  2 A  shows the lens  100  without the electrical connections yet made to supply power to the electrodes  205 . The circular electrodes  205  are typically made from a transparent but electrically conductive material such as indium tin oxide (ITO), patterned on a transparent substrate, such as glass or plastic. Between each electrode  205  is a gap  210  without conductive material to prevent electrical connection between the electrodes  205 . The gaps  210  (nineteen shown) may be either left unfilled or filled with a non-conductive material, for example, silicon dioxide (SiO 2 ). In many cases, it is desirable to make this gap as small as possible, with typical gap sizes of 1 to 3 microns. Smaller or larger gaps are also possible. In this example, twenty electrodes  205  are shown, but many more are typically used, perhaps hundreds or thousands. 
     The lens  100  may include an insulating layer (not shown) on top of the circular electrodes  205  and gaps  210 . This insulating layer may be made from a material that does not conduct electricity but is optically transparent, for example, a 125 nm thick layer of SiO 2  deposited over the electrodes  205 . A series of holes  200  (twenty shown) are patterned in the insulating layer to expose a section of each underlying electrode  205 . The purpose of these holes  200  is explained below with respect to  FIG.  2 B . 
       FIG.  2 B  shows the electrodes  205  with buss lines  220  (twenty shown) connected to respective electrodes  205  via respective holes  200 . Buss lines  220  are made from an electrically conductive material, for example, nickel. They are typically about 10 microns wide, but can be narrower (e.g., 1 micron) if space is limited and power conduction is low or wider (e.g., 100 microns) if power conduction is higher. Each buss line  220  may be up to 10 mm long, depending on the circuit design. 
     In operation, the buss lines  220  provide electrical power to the electrodes  205 . Each buss line  220  delivers power only to its designated electrode  205  and not to any other electrode  205 . The insulating layer prevents the buss lines  220  from shorting out or connecting to the other electrodes below it, and only allows connection of the buss line  220  to the desired electrode  205  through the via hole  200  in the insulating layer. 
     The example lens  100  shown in  FIGS.  1  and  2    uses one buss line per electrode. In this example design of twenty electrodes, providing twenty buss lines and twenty electrical drive channels is manageable, but when the lens has many more electrodes, using one buss lines per electrode can become problematic. Additional buss lines can degrade the lens&#39;s optical quality by blocking light and adding undesired diffraction sources, and every additional electrical channel adds complexity and cost to the electronics. These problems can be mitigated by adding resistors between electrodes, allowing only a subset of the electrodes to be connected to the buss lines. The electrodes that aren&#39;t connected to the buss lines are powered by current delivered via resistive bridges and adjacent electrodes. This reduces the number of buss lines and electrical drive channels, but can increase the electrical power consumption as described in greater detail below. 
       FIG.  3    shows a typical electrical schematic of an electro-active lens without resistive bridges (e.g., lens  100  in  FIGS.  1  and  2   ). Drive signals are provided by analog output voltage sources  5 ,  10 ,  15 ,  20 ,  25 ,  30 ,  35 ,  40 ,  45  and  50 . These voltage sources are supplied by a controller (not shown), such as an application-specific integrated circuit (ASIC) embedded or electrically coupled to the electro-active lens. Capacitors C 1  through C 10  on the left side of the schematic in  FIG.  3    represent the capacitance created by the liquid crystal layer (not shown) modulated by the electrodes. The ground symbol shows the ground plane to be the substrate opposite to the patterned-with-electrodes substrate as well as the opposite potential of the analog outputs. 
     The drive signal in this example is a square wave oscillating at 100 Hz, with the peak to peak voltage amplitude being, from voltage source  5  through  50 , 0.57, 0.62, 0.69, 0.76, 0.83, 0.0.92, 1.03, 1.13, 1.27 and 1.5 volts, respectively. These voltages are determined by the desired gradient of retardation in the liquid crystal to create the desired optical effect. There is a relationship between the liquid crystal response and voltage referred to as the Threshold Voltage, typically referred to as the V 10 -V 90  specification, indicating the voltage range needed to move the liquid crystal molecules through 80% of its range. The voltages may be adjusted to compensate for other design variables, such as the distance from the electrodes to the liquid crystal or the liquid crystal layer thickness. 
       FIG.  4    shows a typical electrical current flow through each of the drive channels for an electro-active lens without resistive bridges like those illustrated in  FIGS.  1 - 3   . The maximum electrical current seen is 120 nano-Amperes (120×10 −9  A). If the electro-active lens&#39;s control circuitry draws another 130 nano-Amperes, this current is low enough that the lens  100  can operate for about 40 hours using a 10-microamp hour battery, which is small enough to be embedded in an electro-active ophthalmic lens, such as an electro-active contact lens or electro-active intraocular lens. 
     Electro-Active Lenses with In-Plane Resistive Bridges 
       FIG.  5 A  shows a plan view of electrodes  34  connected by in-plane resistive bridges  38  in a (prior art) electro-active lens from U.S. Pat. No. 9,280,020 to Bos et al., which is incorporated herein by reference in its entirety. The electrodes  34 , in-plane resistive bridges  38 , and a central disk electrode  35  are formed by patterning an electrode layer  30  on a substrate  22 . As shown in a close-up region  2 - 2 , the in-plane resistive bridges  38  span gaps  36  (e.g., open spaces) between adjacent electrodes  34 , making it possible to reduce the number of input connections  70  between the electrodes  34  and the voltage source (not shown). 
     The close-up  2 - 2  also shows that the in-plane resistive bridges  38  create discontinuities, such as variations in width and (sharp) corners, that prevent the electrodes  34  from being perfect rings. If the resistive bridges  38  are large enough, these breaks or discontinuities can degrade the electro-active lens&#39;s optical performance and the electrode&#39;s electrical performance. Typically, in-plane resistive bridges that deliver good optical performance are typically 2 microns wide and 4 microns long. However, a resistor of this size is only about two squares of resistive material, making it difficult to use materials with a high enough resistivity or sheet resistance to provide the desired resistance to keep power consumption low as explained below. Increasing the area increases the resistance, but also necessitates a larger gap between electrodes  34 , a larger discontinuity in each resistor  38 , or both. As shown in  FIG.  5 A , intruding into the electrode  34  to lengthen the resistor  38  can provide the area to increase the resistor&#39;s length-to-width ratio so a larger amount of resistive material can be used, resulting in higher resistance, but the integrity and performance of the electrodes  34  is then compromised. The electrodes  38  shown in  FIG.  5 A  are typically 30 microns long and 3 microns wide (about 10 squares), which provides decent resistance but degrades optical performance. 
       FIG.  5 B  shows an electrical schematic of an electro-active lens with in-plane resistive bridges R 1  through R 9 . Each of these resistors has a resistance value of 2,000 ohms. These resistive bridges are formed in the same plane as the electrodes between adjacent electrodes. At this resistance value, they can have dimensions small enough not to degrade the electro-active lens&#39;s optical quality. That is, they are small enough to fit within the gap between electrodes and do not diffract or scatter enough incident light to obstruct or occlude a user&#39;s ability to see clearly through the lens. But the resistors increase the lens&#39;s current consumption dramatically. 
       FIG.  6    shows the typical electrical current flow through each of the drive channels for the electro-active lens shown in  FIG.  5   . The maximum electrical current is 117 micro-Amperes (117×10 −6  A). At this current consumption, the electro-active lens would deplete a 10-microamp hour battery in about five minutes, which is too short to be practical for most ophthalmic applications. 
       FIG.  7    shows an electrical schematic of an electro-active lens with in-plane resistive bridges R 1  through R 9  with resistance values of 100,000 ohms each. These resistive bridges are larger and thus are more likely to degrade the lens&#39;s optical performance. The increased resistance cuts the lens&#39;s current consumption, but not by enough to make the lens practical for ophthalmic applications. 
       FIG.  8    shows the current flow of the lens shown in  FIG.  7   . Although the resistance is substantial, the peak current consumption is almost 2.5 micro-Amperes (2.5×10 −6  A), which is more than twenty times higher than the current consumed by the lens without resistive bridges shown in  FIG.  3   . Even at this current consumption level, this electrode/resistor configuration would have a battery life that is too short for use in contact lenses or intraocular lenses. 
       FIG.  9    shows an electrical schematic of an electro-active lens with the resistive bridges modified to each have 2,500,000 ohms of resistance (2.5 MΩ). These resistive bridges are about 50 microns long by 2 microns wide, which is large enough to degrade the electro-active lens&#39;s optical performance. At this resistance, the electrical current begins to approach the resistance between electrodes in an electro-active lens without resistive bridges in the circuit. But the resistive bridges are also large enough that the electrodes must be farther apart or bent or curved for the resistive bridges to fit between them. Pushing the electrodes farther apart or changing their shape degrades the lens&#39;s optical quality, making the lens unsuitable for many ophthalmic applications. 
       FIG.  10    shows the typical electrical current flow through each of the drive channels for the electro-active lens described in  FIG.  9   . The maximum electrical current is 200 nano-Amperes (200×10 −9  A), which approaches the level of power consumption of a lens without resistive bridges. The current consumption is low enough for the lens&#39;s battery life to roughly match that of an electro-active lens without resistive bridges, but the lens&#39;s optical quality is worse than that of an electro-active lens without resistive bridges. As result, even though the lens with 2.5 MΩ in-plane resistive bridges has a battery life long enough for use as a contact lens or intraocular lens, it can&#39;t be used as a practical contact lens or intraocular lens. 
     Electro-Active Lenses with Raised Resistive Bridges 
       FIGS.  11 - 12    show electro-active lenses and concentric ring electrodes with raised resistive bridges and how they may be used in an electro-active lens. Rather than the resistors being within a gap between electrodes or connected at a break point in each electrode, there is an insulating layer between the resistor and the electrodes, which are connected through the vias in the insulating layer. This yields continuous electrode rings because there is no need to remove surface area from the electrodes to make room for the resistors. It also enables resistors with a larger ratio of length to width. This longer length-to-width ratio allows the resistors to be fabricated with a very high overall resistance and a smaller sheet resistance. For example, for a material with a sheet resistance of 100 kΩ per square, which is a common, easily fabricated type of material, the resistor between buss line connection points can have a resistance of 2.5 MΩ with a length-to-width ratio of 25:1. Other resistances and length-to-width ratios are also possible, depending on the resistive bridge material and lens design criteria, which may include desired battery life. 
     One other advantage of raising the resistive bridges to a level above (or below) the electrodes is that the resistive bridge material can be different than that of the electrodes. This allows the material to be selected for the electrodes that has the desired optical qualities but perhaps low resistance, and a different material selected for the resistors that has high resistance but perhaps low optical quality. Since the resistors comprise such a miniscule area of the lens, they can even be made of an opaque material without having a meaningful impact on the lens&#39;s optical quality. 
       FIG.  11    shows a cross section of a portion of an electro-active lens with a raised resistive bridge (resistor)  350 . This resistive bridge  350  is electrically connected to several electrodes  305   a - 305   e  (collectively, electrodes  305 ), which are patterned onto a substrate  310 . In an ophthalmic lens, such as a contact lens, there may be tens to hundreds of electrodes  305  spanning a width of about 10-20 mm, with each electrode  305  having widths on the order of microns to millimeters (e.g., 0.5 μm, 1 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9, μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm, 250 μm, 500 μm, 1 mm, 1.5 mm, 2 mm, or any other value or range up between about 0.5 μm and about 2 mm). Depending on the implementation, the electrodes  305  may of identical or different widths, possibly with a disc-shaped electrode at the center of the lens. 
     Unlike in an electro-active lens with conventional resistive bridges, the electrodes  305  shown in  FIG.  11    are each of uniform width, with no discontinuities. In addition, the gaps between adjacent electrodes are also relatively small. For instance, these gaps may range in size from nanometers to microns (e.g., 100 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 1 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9, μm, or 10 μm or any other value or range up to about 10 μm). The electrodes  305  may be relatively thin, e.g., less than 200 nanometers (nm), and preferably less than 40 nm. 
     An insulating layer  300  is blanketed over the electrodes  305 , and buss line via holes  330   a  and  330   b  (collectively, buss line via holes  330 ) are patterned into the insulating layer  300 . For instance, the insulating layer  300  may be a 120 nm thick layer of silicon dioxide or a 0.5 μm thick layer of SU-8. Resistor via holes  340   a - 340   c  (collectively, resistor via holes  340 ) are also patterned into the insulating layer  300 . The resistive bridge  350  is then formed such that the underlying electrodes  305  are connected through the resistive bridge  350  through the via holes  330  and  340 . Buss lines  315   a  and  315   b  (collectively, buss lines  315 ) connect through the via holes  330   a  and  330   b , respectively, to both the resistive bridge  350  and the electrodes  305   a  and  305   e . Electrodes  305   a  and  305   e  are powered directly by buss lines  315   a  and  315   b , while electrodes  305   b - 305   d  are powered indirectly through the resistive bridge  350 . 
     The sheet resistance of the resistive bridge  350  may range of from approximately 0.1 MΩ per square to approximately 100 MΩper square or more. The sheet resistance of the insulating layer  300  is greater than approximately 10 18 Ω per meter, and ideally infinite. The resistance of the electrodes  305  is less than approximately 200Ω per square. Other measures of resistance may be used depending on the optical effects sought to be achieved. The resistive layer may be relatively thin, e.g., less than 200 nanometers (nm), and preferably less than 40 nm. 
     Although  FIG.  11    shows the buss lines  315  connecting to resistive bridge  350  inside of buss line via holes  330  in such a manner as sharing the electrode  305 , other configurations can be made by those skilled in the art of via hole design. For example, the resistive bridge could occupy the entire bottom of the via hole with the buss line on top of the resistive bridge material. The buss line could also occupy the entire bottom of the via hole with the resistive bridge on top of the buss line material. Likewise, the resistive bridge could be connected to more or fewer electrodes. 
     Having the resistive bridge  350  above the insulating layer  300  provides more room for resistor construction, allowing higher length-to-width ratios to be used without compromising or interrupting the integrity of the electrodes  305 . All other things being equal, increasing a resistor&#39;s length-to-width ratio increases its resistance. And higher resistance translates to lower current consumption and longer battery life. A higher length-to-width ratio might not be possible if the resistor had to remain within the gap between the electrodes at the plane of the electrodes. 
     Placing the resistive bridge  350  above the insulating layer  300  and electrodes also provides for greater flexibility in material choices for the resistor&#39;s construction and more robust, more forgiving error tolerance when constructing resistors with high resistance. For instance, the resistive bridge  350  can made of a transparent conductive material, such as indium tin oxide, or a layer of material that is thin enough to be translucent, such as a layer of nickel that is microns thick. If the resistive bridge  350  is used in a reflection geometry, or if the resistive bridge  350  is relatively small, it can be made of an opaque material (e.g., a thicker layer of metal). 
       FIGS.  12 A and  12 B  show a plan view of the electrodes  305 , buss lines  315 , buss line via holes  330 , resistor via holes  340 , and resistive bridge  350 . ( FIG.  12 B  is a close-up view.) Buss lines  315  (six are shown) penetrate the insulation layer at buss line via holes  315  in six locations, making electrical connection to the electrodes  305 . A resistive bridge  350  is also connected at buss line via holes  315 . The resistive bridge  350  connects to the unpowered electrodes  305  through resistor-only via holes  340  (fourteen are shown). 
       FIG.  12 C  shows the buss lines  315 , buss line via holes  330 , resistor via holes  340 , and resistive bridge  350  without the electrodes  305 . Although the resistive bridge  350  is shown as set of straight line segments (each of which could be considered as an individual resistive bridge), they could be other shapes and sizes as well to provide better control of the desired resistance. 
     For example,  FIG.  12 D  shows a raised resistive bridge  350 ′ with curved bridge segments  352   a - 352   d  (collectively, curved bridge segments  352 ) that connect adjacent via holes  330  and  340 . In this case, the curved bridge segments  352  form an undulating or sine-like path between a pair of buss line via holes  330 . In other cases, the resistive bridge segments could take a different non-straight (e.g., curved, twisted, or jagged) path from one via hole to the next. Moreover, each bridge segment can have a different curvature or path—some can have larger radii of curvature than others or take paths of different shapes. This would increase the length and resistance of each segment and of the resistive bridge as a whole. The curvature may also affect the resistive bridge&#39;s other electrical properties, including its inductance, capacitance, or both. 
     Similarly,  FIG.  12 E  shows a raised resistive bridge  350 ″ with segments  354   a - 354   d  (collectively, variable-width bridge segments  354 ) whose widths vary from segment to segment. In this case, the segments  354  bulge in the middle, but other shapes could be used as well. This variation may be used to provide resistors to compensate for variations in resistance due to length variations among segments of the resistive bridge. The width of each segment may also be varied deliberately to create non-uniform resistance values from segment to segment. For instance, the segment width may be varied to create a non-linear resistance gradient, such as a parabolic resistance gradient. This parabolic resistance gradient could be used to create a parabolic gradient of the electric field resulting in a lens with even fewer buss lines (and better optical quality). 
     An Electro-Active Contact Lens with Raised Resistive Bridges 
       FIG.  13    shows an electro-active contact lens  1300  with raised resistive bridges  1350 . The electro-active contact lens  1300  includes an electro-active lens element  1302  with an electro-active material, such as nematic or cholesteric liquid crystal, sandwiched between a pair of transparent substrates, just like the lens  100  shown in  FIG.  1   . The liquid crystal could also be contained within a cavity defined by folding a single substrate onto itself. One of the surfaces opposite the liquid crystal material is patterned to include a plurality of concentric ring electrodes made of transparent conductive material as shown in  FIGS.  11  and  12 A . 
     The electro-active lens element  1302  also includes a raised resistive bridge  1350  disposed on an insulating layer as shown in  FIG.  11   . This raised resistive bridge  1350  includes segments that connect the electrodes to each other and to buss lines  1320 , also as shown in  FIGS.  11  and  12 A . The buss lines  1320  connect in turn to a bus  1322 , which connects to a processor (here, an ASIC  1324 ) via a flexible printed circuit board (PCB)  1326 . The flexible PCB  1326  also connects the ASIC  1324  to a ring-shaped power battery  1328  and a ring-shaped antenna  1330 , both of which are concentric with the electro-active lens element  1302  as shown in  FIG.  13   . All of these components are completely or partially embedded in a base optical element  1304 . This base optical element  1304  may provide additional optical power—i.e., it may function as a fixed lens—and can be formed of any suitable material, include soft hydrogels like those used in soft contact lenses. 
     In operation, the ASIC  1324  actuates the electro-active lens element  1302  in response to signals received by the antenna  1330  or generated by one or more sensors (not shown) embedded in the electro-active contact lens  1300 . The ASIC  1324  controls the optical power provided by the electro-active lens element  1302  by modulating the voltages applied to the electrodes via the buss  1326 , buss lines  1320 , and raised resistive bridges  1350 . Because the raised resistive bridges  1350  are in a different plane than the electrodes, they can be relatively large (e.g., 2.5 MΩ) without degrading the lens&#39;s optical performance. At this size, they also limit current consumption to reasonable rates (e.g., on the order of 100-200 nA), which makes it possible for the battery  1328  to go long stretches (e.g., 40 hours or more) between rechargings (e.g., via the coil-shaped antenna  1330 ) or before the electro-active contact lens  1300  is thrown away. 
     Making an Electro-Active Intraocular Lens with Raised Resistive Bridges 
       FIG.  14    shows a process  1400  for making an electro-active intraocular lens with raised resistive bridges. In step  1402 , conductive material (e.g., ITO) is deposited on a transparent substrate, such as a piece of flexible polymer. The electrode material is lithographically pattern to form electrodes (e.g., concentric ring-shaped electrodes) in step  1404 . Next, in step  1406 , a layer of insulating material, such as silicon dioxide, is deposited on the patterned electrodes. Through-holes are lithographically patterned into the insulating layer in step  1408 . In step  1410 , resistive material is disposed on the insulating layer and in the through-holes, forming electrical connections to the electrodes. Suitable resistive materials include, but are not limited to, alloys of nickel and chromium, ITO doped with oxygen, combinations of metals with oxides, and resistive polymers, such as poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). The resistive material is patterned lithographically to form raised resistive bridges in step  1412 , A layer of conductive material is disposed on the resistive bridges and exposed insulating layer in step  1414  and patterned to form the buss lines in step  1416 . 
     CONCLUSION 
     While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. 
     The above-described embodiments can be implemented in any of numerous ways. For example, embodiments of designing and making the technology disclosed herein may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers. 
     Further, it should be appreciated that a computer may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, a computer may be embedded in a device not generally regarded as a computer but with suitable processing capabilities, including a Personal Digital Assistant (PDA), a smart phone or any other suitable portable or fixed electronic device. 
     Also, a computer may have one or more input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include printers or display screens for visual presentation of output and speakers or other sound generating devices for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or in other audible format. 
     Such computers may be interconnected by one or more networks in any suitable form, including a local area network or a wide area network, such as an enterprise network, and intelligent network (IN) or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol and may include wireless networks, wired networks or fiber optic networks. 
     The various methods or processes (e.g., of designing and making the technology disclosed above) outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and/or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine. 
     In this respect, various inventive concepts may be embodied as a computer readable storage medium (or multiple computer readable storage media) (e.g., a computer memory, one or more floppy discs, compact discs, optical discs, magnetic tapes, flash memories, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other non-transitory medium or tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments of the invention discussed above. The computer readable medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present invention as discussed above. 
     The terms “program” or “software” are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of embodiments as discussed above. Additionally, it should be appreciated that according to one aspect, one or more computer programs that when executed perform methods of the present invention need not reside on a single computer or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present invention. 
     Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments. 
     Also, data structures may be stored in computer-readable media in any suitable form. For simplicity of illustration, data structures may be shown to have fields that are related through location in the data structure. Such relationships may likewise be achieved by assigning storage for the fields with locations in a computer-readable medium that convey relationship between the fields. However, any suitable mechanism may be used to establish a relationship between information in fields of a data structure, including through the use of pointers, tags or other mechanisms that establish relationship between data elements. 
     Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. 
     All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. 
     As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. 
     As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. 
     In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.