Multi-depth liquid crystal electrode layer lens

Abstract

A typical liquid crystal lens comprises a liquid crystal sandwiched between a transparent substrate patterned with ring electrodes. Applying a voltage to the electrodes causes the liquid crystal molecules to rotate, changing their apparent refractive index and the focal length of the lens. The ring electrodes are separated by a gap and narrow towards the periphery of the lens. If the ring electrodes are too narrow, they cannot switch the liquid crystal well. To solve this problem, an inventive liquid crystal lens comprises a substrate with a stepped surface that defines concentric liquid crystal regions whose thickness increases with the radius of the lens. Each region is switched by a different set of ring electrodes, which can be on, below, or opposite the stepped surface. Within each region, the ring electrodes become narrower the further they are from the center of the lens. But the width of the ring electrodes also increases with the thickness of the liquid crystal, offsetting the reduction in width that can reduce lens performance.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of priority to U.S. Application No. 62 / 944,483, filed December 6, 2019, which is incorporated herein by reference in its entirety. Background Art

[0003] One type of liquid crystal lens consists of liquid crystals sealed between opposing surfaces of two transparent substrates. The lens includes transparent electrodes and an alignment layer on opposing surfaces of the transparent substrates. The alignment layer aligns the liquid crystal relative to the substrates. One of the transparent electrodes can be patterned, for example, in the shape of a ring or pixel. The other transparent electrode can be unpatterned and serve as a ground plane.

[0004] Applying a voltage to the patterned electrodes generates an electric field across the liquid crystal. The anisotropic liquid crystal molecules are aligning themselves by the electric field, thereby changing the local refractive index. Applying a voltage gradient to the patterned electrodes generates a gradient electric field, where each electrode generates a different electric field than its neighboring electrodes. Because the electric field affects the refractive index of the liquid crystal, the gradient electric field produces a gradient of change in the refractive index in the liquid crystal, which in turn can produce an optical lens effect. The patterned electrodes can be circular, linear, elliptical, or nearly any other shape required to produce a refractive index gradient in the liquid crystal and a corresponding change in the wavefront transmitted through the lens.

[0005] Circular ring electrodes are common in liquid crystal lenses. These ring electrodes are typically formed by photolithography of an indium tin oxide (ITO) layer with a thickness between 5 nm and 200 nm. The ITO layer is deposited on a first transparent substrate, such as fused silica glass, which can withstand vacuum, temperature, and photolithography processes. The patterned electrodes are coated with an insulating layer, such as SiO2 or SU-8 photoresist. This insulating layer covers the ring electrodes and fills the gaps between adjacent ring electrodes, thereby electrically isolating the ring electrodes from each other.

[0006] Buses connect the ring electrodes to a voltage supply. These buses are thin traces of a conductive material, such as nickel, deposited on an insulating layer and photolithographically patterned. Each bus is connected to a corresponding ring electrode through a through-hole formed in the insulating layer. A lens with a small number of electrodes (e.g., 20 or fewer) can have one bus per electrode. In a lens with a large number of electrodes (e.g., hundreds of electrodes), each bus can be connected to a subset of electrodes that are connected to each other via resistive bridges. (For more on resistive bridges, see, for example, U.S. Patent No. 10,599,006 to Van Heugten et al., entitled "Electro-Active Lenses with Raised Resistive Bridges," which is incorporated herein by reference in its entirety.)

[0007] The ring electrodes, bus bars and insulating layer are coated with an alignment layer such as a polyimide resin chemical manufactured by Nissan Chemical Corporation of Tokyo, Japan. The other transparent substrate of the lens can be coated with an unpatterned ITO layer that acts as a ground plane and alignment layer. A liquid crystal material such as Merck MLC-2140 liquid crystal is sealed between the coated surfaces of the transparent substrate to form the lens.

[0008] In a liquid crystal lens with ring electrodes, the ring electrodes become progressively narrower as they move farther from the center of the lens, while the gaps between adjacent ring electrodes are all approximately the same width. One problem with this approach is that the total electric field amplitude decreases with lens radius, because no electric field is generated above the gaps between the ring electrodes. Therefore, beyond a certain distance, for example, at a radius of 10 mm in a typical lens, the ring electrodes become too narrow to generate an effective total electric field: the ratio of the electrode width to the width of the gap between adjacent electrodes becomes too small to generate an effective total electric field at the periphery of the lens.

[0009] For example, if the electrode width is 100 μm and the gap width on either side of the electrode is 3 μm, then at that point about 3% of the electric field acting on the liquid crystal is disrupted, causing a relatively small undesirable optical effect. As the lens gets larger, the gap remains constant, but the electrodes become narrower, causing the ratio of electrode width to gap width to decrease. At a point in the lens where the electrode width is 30 μm and the gap width is still 3 μm, the gap width is 10% of the electrode width, disrupting about 10% of the electric field. 3% disruption may be tolerable, but 10% disruption (and the lens degradation caused by this amount) may not be tolerable. This disruption limits the diameter of the liquid crystal lens, the number of ring electrodes and / or the minimum ring electrode width.

[0010] One way to increase the lens diameter before the electrode width-gap width ratio becomes too small is to increase the thickness of the liquid crystal. As the thickness of the liquid crystal layer increases, the electric field used to switch the liquid crystal material also increases, and the width of the electrode ring used to generate the electric field also increases. Essentially, every dimension of the lens is scaled up except for the gap width, which is generally set by the spatial resolution of the lithography used to pattern the electrodes. Unfortunately, increasing the thickness of the liquid crystal layer makes the lens switch more slowly (i.e., the switching speed of the lens is reduced), which is undesirable and limits the usefulness of this solution. Summary of the Invention

[0011] The present technology enables larger electrode-based liquid crystal lenses while reducing or minimizing the drop in switching speed and preventing the ratio of electrode width to gap width from becoming unacceptably low. The inventive lenses are suitable for use in or as ophthalmic lenses, such as spectacle lenses, contact lenses, and intraocular lenses. They can also be used in mixed, augmented, and virtual reality systems to adjust the apparent position of virtual objects perceived by a viewer, as well as in imaging cameras, night vision sensors, and any other optical devices that utilize lenses.

[0012] The present technology includes an electro-active lens having a first substrate, a second substrate, a liquid crystal material, a ground electrode, and a plurality of ring electrodes. The first substrate has a uniform (e.g., flat or smooth) surface. The second substrate has a stepped surface opposite the uniform surface. The stepped surface has at least a first step and a second step. The liquid crystal material is disposed between the uniform surface and the stepped surface. The ground electrode is disposed on the uniform surface or the stepped surface. The ring electrodes are disposed on the other of the uniform surface or the stepped surface, with at least two ring electrodes for the first step and at least two ring electrodes for the second step. In operation, the ring electrodes apply a voltage to the liquid crystal material. This voltage generates an electric field that causes the liquid crystal molecules to reorient themselves, thereby changing the focal length of the electro-active lens.

[0013] The uniform surface may be a planar surface or a curved surface.

[0014] The stepped surface may be formed by stacking cylinders of different diameters concentric with the optical axis of the electro-active lens. The first step may be taller than the second step by a height selected to provide an optical path distance equal to an integer number of waves at the design wavelength of the electro-active lens.

[0015] The first step may have a circular surface opposite the uniform surface and centered on the optical axis of the electro-active lens, and the second step may have an annular surface concentric with the circular surface and opposite the uniform surface. The circular surface is separated from the planar surface by a first distance, and the annular surface is separated from the uniform surface by a second distance greater than the first distance. A ground electrode may be disposed on the stepped surface, in which case the ring electrodes are disposed on the uniform surface, with at least two ring electrodes for the first step opposing the circular surface, and at least two ring electrodes for the second step opposing the annular surface. Alternatively, the ground electrode may be on the uniform surface, and the ring electrodes may be below the stepped surface, with at least two ring electrodes below the circular surface and at least two ring electrodes below the annular surface. The ground electrode may also be disposed on the uniform surface, and multiple ring electrodes may be disposed on the stepped surface, with at least two ring electrodes on the circular surface and at least two ring electrodes on the annular surface. In this case, the electro-active lens may further include a bus disposed on a cylindrical surface connecting the circular and annular surfaces to connect at least one of the ring electrodes on the circular surface to a voltage supply.

[0016] The ring electrodes for the first step may include a first electrode having a first diameter and a first width, and the ring electrodes for the second step may include a second electrode having a second diameter greater than the first diameter and a second width greater than the first width. There may be at least ten ring electrodes for the first step and at least ten ring electrodes for the second step. Each of the ring electrodes for the first step may have a first area, and each of the at least two ring electrodes for the second step may have a second area greater than the first area.

[0017] The electro-active lens may further include a first resistive bridge connecting two of the ring electrodes for the first step, and a second resistive bridge connecting two of the ring electrodes for the second step. The electro-active lens may further include a first spacer bead having a first diameter between the first step and the uniform surface, and a second spacer bead having a second diameter greater than the first diameter between the second step and the uniform surface.

[0018] This type of electro-active lens can be used to focus incident light. Applying a first voltage to the ring electrodes for a first step actuates a first portion of the liquid crystal material between the first step and a uniform surface. Similarly, applying a second voltage to the ring electrodes for a second step actuates a second portion of the liquid crystal material between the second step and the uniform surface. This changes the focal length of the electro-active lens.

[0019] An alternative electro-active lens includes a first substrate, a second substrate, a liquid crystal material, a ground electrode, and ring electrodes. The first substrate has a uniform surface. The second substrate has a stepped surface having at least two steps opposite the uniform surface. The height difference between the first and second steps is selected to provide an optical path length equal to an integer number of wavelengths at the design wavelength of the electro-active lens. The liquid crystal material is positioned between the uniform surface and the stepped surface. The ground electrode is on the stepped surface. The ring electrodes are on the uniform surface, wherein at least ten of the ring electrodes are opposite the first step and at least ten of the ring electrodes are opposite the second step.

[0020] The ring electrodes opposite the first step may include a first electrode having a first diameter and a first width, and the ring electrodes for the second step may include a second electrode having a second diameter greater than the first diameter and a second width greater than the first width. Each ring electrode for the first step may have a first area, and each ring electrode for the second step may have a second area greater than the first area. There may be at least one hundred ring electrodes for the first step and at least one hundred ring electrodes for the second step. There may also be a first resistive bridge connecting two of the ring electrodes opposite the first step, and a second resistive bridge connecting two of the ring electrodes opposite the second step.

[0021] Another alternative electro-active lens includes a first substrate, a second substrate, a liquid crystal material, a ground electrode, and a ring electrode. The first substrate has a uniform surface. The second substrate has a stepped surface having at least two steps opposite the uniform surface. The liquid crystal material is disposed between the uniform surface and the stepped surface. The ground electrode is disposed on the stepped surface. There are first ring electrodes, each having the same (first) area and disposed on the uniform surface opposite the first step, for applying a first voltage to the liquid crystal material. There are also second ring electrodes, each having the same (second) area and disposed on the uniform surface opposite the second step, for applying a second voltage to the liquid crystal material. The second area is larger than the first area.

[0022] There may be at least one hundred first ring electrodes and at least one hundred second ring electrodes.There may be a first resistance bridge connecting two first ring electrodes and a second resistance bridge connecting two second ring electrodes.

[0023] Yet another electro-active lens comprises: a first substrate having a curved surface; a second substrate having a stepped surface opposite a uniform surface; a liquid crystal material disposed between the curved surface and the stepped surface; a ground electrode disposed on the stepped surface; and a plurality of ring electrodes disposed on the curved surface, wherein at least ten ring electrodes are opposite a first step and at least ten ring electrodes are opposite a second step. The height difference between adjacent steps of the stepped surface can be selected to provide an optical path length equal to an integer number of wavelengths at the design wavelength of the electro-active lens. The electrode opposite the first step can include a first electrode having a first diameter and a first width, and the ring electrode opposite the second step can include a second electrode having a second diameter greater than the first diameter and a second width greater than the first width. Each ring electrode opposite the first step can have a first area, and each ring electrode opposite the second step can have a second area greater than the first area. There can be at least one hundred ring electrodes opposite the first step and at least one hundred ring electrodes opposite the second step. The electro-active lens may also include a first resistive bridge connecting two of the ring electrodes opposite the first step, and a second resistive bridge connecting two of the ring electrodes opposite the second step.

[0024] All combinations of the aforementioned concepts and the additional concepts discussed in more 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 the claimed subject matter appearing at the end of this disclosure are considered to be part of the inventive subject matter disclosed herein. Terms explicitly employed herein that may also appear in any disclosure incorporated by reference should be given the meaning that best fits the specific concepts disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Those skilled in the art will appreciate that the drawings are primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily drawn to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to aid in understanding different features. In the drawings, like reference numerals generally refer to like features (e.g., functionally similar and / or structurally similar elements).

[0026] Figure 1A Shown is a cross-sectional view of a liquid crystal lens with a single ground plane electrode on a stepped surface opposite a ring electrode on a uniform planar surface.

[0027] Figure 1B A cross-sectional view of a liquid crystal lens is shown with a separate ground plane electrode on a stepped surface opposite a ring electrode on a uniform planar surface.

[0028] Figure 2AA cross-sectional view of a liquid crystal lens is shown, wherein a ring electrode on a stepped surface is opposed to a ground plane electrode on a uniform planar surface.

[0029] Figure 2B Show Figure 2A A perspective view of some ring electrodes and a portion of a stepped surface in a liquid crystal lens.

[0030] Figure 2C A cross-sectional view of a liquid crystal lens is shown, where a ring electrode below a stepped surface is opposed to a ground plane electrode on a uniform planar surface.

[0031] Figure 3 A cross-sectional view of a liquid crystal lens is shown, where a single ground plane electrode on a curved stepped surface is opposed to a ring electrode on a uniformly curved surface.

[0032] Figure 4 Shown as Figure 1A-3 Plan view of the ring electrodes, resistive bridges (arcs), bus bars, and steps of the stepped surface in the lens shown in FIG.

[0033] Figure 5A and 5B Shown are ring electrodes and a resistive bridge suitable for use in the inventive liquid crystal lens.

[0034] Figure 6A and 6B Shown are ring electrodes and a spiral resistor bridge suitable for use in the inventive liquid crystal lens.

[0035] Figure 7 A spiral resistor bridge with constant width is shown.

[0036] Figure 8 Showing a spiral resistor bridge with varying width.

[0037] Figure 9 A spiral resistor bridge with a gap of varying width is shown. DETAILED DESCRIPTION

[0038] The present technology realizes an electrode-based liquid crystal lens with a large diameter, relatively fast switching speed and a high ratio of electrode width to gap width in its peripheral region. This is achieved by a multi-thickness liquid crystal layer, which is thinner at the center and thicker as it moves away from the center of the lens. For a circularly symmetric lens, the liquid crystal regions can be arranged concentrically, where the thickness increases with the radius, and the set of annular or substantially annular electrodes (referred to as ring electrodes) used for each region is different. These ring electrodes can be closed rings or non-closed rings; that is, there can be gaps in the circle or ring formed by the ring electrodes. Similarly, the ring electrodes may or may not be completely circular.

[0039] Each ring electrode has a width equal to the difference between its outer radius and inner radius. The width of the ring electrode decreases with radius and increases with liquid crystal thickness, so that moving outward from the center of the lens, the ring electrode width changes in a stepped sawtooth manner. In the central thin section, the ring electrodes can be designed in a conventional manner with gradual narrowing. At the radius where the electrode width becomes borderline acceptable - for example, the ratio of electrode width to gap width is 20 to 1, the thickness of the liquid crystal is increased, for example doubled, and the width of the ring electrode at this radius is increased accordingly. The widening electrode becomes narrower and narrower the farther it is from the center of the lens, until it becomes unacceptably narrow, at which point the liquid crystal thickness and electrode width can be increased again. This arrangement can be repeated as many times as needed.

[0040] Electrodes can drive liquid crystal segments of different thicknesses with different voltages, for example, with thicker liquid crystal regions driven by higher voltages. These staggered voltages can be provided to ensure that the electrodes in each segment of the lens are isolated from each other in the drive control input circuitry. Alternatively, different groups can be connected to the same group of drive control input circuitry, which can then be adjusted using resistors.

[0041] Such multi-depth lenses can be constructed using photolithographic patterning. For example, for a two-layer design, a circular (top-hat) deposit of SU-8 photoresist or other suitable material can be formed in the center of the surface of one of the lens substrates to form a stepped surface. The step height (i.e., the thickness of the SU-8 deposit) defines the variation in the thickness of the liquid crystal layer trapped between the substrates. The ring electrode can be patterned on the SU-8 deposit, below the SU-8 deposit, or on a substrate without the SU-8 deposit.

[0042] The example inventive liquid crystal lens has a central section of a substrate with a 10-micron-high, 20-mm-diameter platform made of SU-8 photoresist, sitting on a 40-mm-diameter circular lens. 10-micron spacer guards are placed on the platform, and 20-micron spacer guards are placed elsewhere, resulting in a 10-micron-thick liquid crystal layer in the central section and a 20-micron-thick layer in the rest of the lens.

[0043] The thin liquid crystal region at the center of the inventive liquid crystal lens can have a higher switching speed than the thicker peripheral liquid crystal regions. In some cases, this is an acceptable tradeoff, as in many applications (e.g., human vision), the center of the lens is primarily utilized. For example, when such lenses are used in virtual and / or augmented reality devices to correct for vergence-accommodation conflict (VAC), in which the brain is tricked into thinking an image is closer, but the eye doesn't actually accommodate for the closer object, the speed of lens switching can be considered when positioning the image in view. For example, consider making a virtual object appear closer and then moving it laterally across the field of view. If a virtual object should change its virtual position in 100ms, but only the central segment of the lens can switch quickly, while the peripheral segments may take 300ms to switch, the virtual object can be initially positioned / repositioned so that the central lens segment brings the virtual object into focus in 100ms. Then, 300ms later, after the peripheral segments change focus to match the central segment, the virtual object's position in the field of view can be translated laterally to the peripheral segments of the lens, bringing the virtual object into correct focus.

[0044] Multi-depth liquid crystal lens

[0045] Figure 1A A cross-section of an inventive liquid crystal lens 100 is shown. The liquid crystal lens 100 comprises a liquid crystal material 140 sealed between a first transparent substrate 110 and a second transparent substrate 120. A suitable liquid crystal is Merck MLC2140, a nematic liquid crystal. Liquid crystals are also available from many other manufacturers, such as Chisso of Japan. The first transparent substrate 110 has a smooth surface 112 facing a layered or stepped surface 122 defined by the second transparent substrate 120. The smooth surface 112 is flat, uniform, and regular—it has no perceptible protrusions, lumps, or indentations—and, in this example, is planar. In other examples, the smooth surface 112 can be smoothly curved, such as in the shape of a portion of a spherical, parabolic, or aspherical surface.

[0046] In this example, the stepped surface 122 defines three steps 131-133 (also referred to as layers, levels, or terraces), and this example is shown as being concentric with the optical axis 101 of the lens (and therefore concentric with each other). In some cases, these layers are not circular or concentric; for example, they can be elliptical, or have their centers shifted relative to each other and / or the optical axis of the lens. (Other numbers and arrangements of steps are also possible.) The first step 131 has a circular face 134 centered on the optical axis 101 and opposite the smooth surface 112 of the first substrate 110; the second step 132 and the third step 133 have corresponding annular faces 135 also centered on the optical axis 101. The circular faces 134 and the annular faces 135 are connected by a cylindrical face 136, the height of which is selected to provide an integer multiple (e.g., one) wavelength of the optical path difference at the design wavelength. These heights fix the thickness of the different regions of the liquid crystal 140. Unlike a Fresnel lens, which has surfaces formed from curved or angled faces, the circular face 134 and the annular face 135 are planar and parallel to each other and perpendicular to the optical axis 101 of the lens, which is parallel to the cylindrical face 136 .

[0047] Geometrically, the stepped surface 122 can be formed by stacking cylinders of monotonically decreasing radius on top of each other. Physically, the stepped surface 122 can be formed by depositing SUSU-8 photoresist, silicon dioxide, or another suitable material on a piece of glass or plastic and patterning it. The stepped surface can also be formed by 3D printing or molding the second substrate 120 into the desired shape with a resin. Alternatively, the stepped surface can be formed by stamping a suitable material into the desired shape. There are many other suitable manufacturing methods, including microfabrication processes, such as electronic circuit manufacturing, diamond single-point turning, etc.

[0048] The stepped surface 122, comprising a circular face 134, an annular face 135, and a cylindrical face 136, is coated with a transparent conductive material, such as ITO, that serves as a ground plane electrode 124. In operation, this electrode 124 maintains the entire stepped surface 122 at the same (ground) potential. This coating can be accomplished by sputtering, vapor deposition, or another suitable thin-film coating method. Electrode 124 is coated with a liquid crystal alignment layer 126, which anchors and / or aligns the liquid crystal material 140 relative to the stepped surface 122.

[0049] The ground plane electrode 124 faces a ring electrode 114 formed on the smooth surface 112 of the first substrate 110. (The center ring electrode 114 may be circular rather than ring-shaped.) The ring electrode 114 may be connected to one or more voltage supplies via a bus and / or a resistor bridge, as described below. The voltage supply applies different (e.g., phase-folded) voltages to the ring electrode 114, thereby generating an electric field that causes the liquid crystal 140 between the ring electrode 114 and the ground plane electrode 124 to realign itself in a gradient manner. This realignment changes the focal length of the lens.

[0050] The ring electrodes 114 are separated by gaps 115 and divided into subsets 114a-114c, with one subset for each step 131-133 of the stepped surface 122. There are at least two, and possibly more (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or more), ring electrodes 114 per subset 114a-114c / step 131-133. The ring electrodes 114 in each subset can be connected to each other via a resistive bridge and to one or more voltage supplies via a bus, as described below.

[0051] The width of the ring electrodes 114 varies as follows: within each subset / for each step, the ring electrodes 114 become progressively narrower the further they are from the optical axis 101 of the lens. (In contrast, the gaps 115 are all approximately the same width, e.g., about 3 microns.) The width of the ring electrodes 114 also gradually increases with the thickness of the liquid crystal / step height. Thus, the outermost ring electrodes 114 in each subset are narrower than the innermost ring electrodes 114 in the next outer subset. Figure 1A In the embodiment, the outermost ring electrode 114 in the first subset 114a is narrower than the innermost ring electrode 114 in the second subset 114b, and the outermost ring electrode 114 in the second subset 114b is narrower than the innermost ring electrode 114 in the third subset 114c. (described below) Figure 4 A plan view of ring electrode 114 is shown. The wider ring electrodes on the lower steps 132 and 133 can apply higher voltages to thicker areas of liquid crystal 140. The electrodes are coated with an insulating layer to prevent the bus from shorting the electrodes. The bus passes through the electrodes and the insulating layer without making electrical contact with the electrodes except at discrete locations.

[0052] The smooth surface 112 and the ring electrode 114 are coated with a liquid crystal alignment layer 116, which can be about 40 nm thick and aligns and / or anchors the liquid crystal material 140 to the smooth surface 112. This alignment layer is typically applied by spin coating, spray coating, dip coating, inkjet printing, or another suitable method. The alignment layer is also rubbed with a felt cloth, exposed to polarized light, or heated to introduce a pre-tilt angle into the alignment layer. An example alignment layer material is Sunever, manufactured by Nissan Chemicals of Japan.

[0053] Figure 1B Show Figure 1A 13. A modified version 100' of the liquid crystal lens 100 in FIG. In this modified liquid crystal lens 100', separate electrodes 124', 124", and 124'" are present on the circular face 134 and the annular face 135 of the stepped surface 122. The electrodes 124', 124", and 124'" may be coated with an insulating layer (not shown) and connected to respective voltage supplies via buses (conductive traces; not shown) formed on the insulating layer. These electrodes 124', 124", and 124'" are not directly connected to each other—they do not extend above the cylindrical face 136 of the stepped surface—and therefore may be maintained at different voltage potentials. For example, these potentials may be selected to account for variations in the thickness of the liquid crystal material 140, such that a larger potential drop occurs across thicker regions of the liquid crystal material 140. This may allow for a reduction in the maximum voltage applied to the ring electrode 114 for actuating the liquid crystal 100'. Alternatively, electrodes 124', 124", and 124'" can be connected to a common ground via a bus so that they are at the same potential. The voltages used to achieve the desired changes in birefringence and optical path difference (OPD) as a function of liquid crystal material and thickness are disclosed in: Wu et al., "Birefringence Measurements of Liquid-Crystals," Applied Optics 23(21):3911-3915, December 1984, DOI: 10.1364 / AO.23.003911. For example, the drive voltage can be increased by 0.2 volts to achieve the same OPD as the thickness of the liquid crystal increases from 15 μm to 25 μm.

[0054] Figure 2A and 2B The inventive liquid crystal lens 200 is shown with a ring electrode 224 formed on a stepped surface 222 of a transparent substrate 220 . Figure 2A shows a cross section of the liquid crystal lens 200, and Figure 2B A perspective view is shown of a portion of a stepped surface 222 and some ring electrodes 224. A transparent substrate 220 and another transparent substrate 210 have smooth (here, planar) surfaces 212 with a liquid crystal material 240 between the smooth surface 212 and the stepped surface 222. The smooth surface 212 is coated with a transparent conductive material, such as ITO, forming a ground plane electrode 214, which is in turn coated with a liquid crystal alignment layer 216.

[0055] Ring electrodes 224 are formed from conductive traces deposited directly on circular face 234 and annular face 235 of the stepped surface, connected by cylindrical face 236 and concentric with the lens' optical axis 201. The faces define steps 231-233, which define regions of increasing liquid crystal thickness moving radially outward from the lens' optical axis 201. There are at least two ring electrodes 224 on circular face 234 and on each annular face 235, providing corresponding subsets 224a-224c of ring electrodes for the steps 231-233 and regions of liquid crystal material 240. The ring electrodes 224 of each subset 224a-224c can be interconnected via a resistive bridge, as described below.

[0056] The outer ring electrode 224 on each face / step is narrower than the inner ring electrode 224 on that face / step. And the innermost ring electrode 224 on each face / step is wider than the outermost ring electrode 224 on the next higher step. Figure 2A , the outermost ring electrode 224 on the first step 231 (first subset 224a) is narrower than the innermost ring electrode 224 on the second step 233 (second subset 224b), and the outermost ring electrode 224 on the second step 233 is narrower than the innermost ring electrode 224 on the third step 233 (third subset 224c).

[0057] Figure 2B The diagram shows how the ring electrodes 224 are connected to voltage supplies 250a and 250b via voltage supply connections or busses 252a-252d (collectively referred to as busses 252). (For clarity, the third step 233 is omitted.) Busses 252 are formed from a conductive material, such as ITO or nickel, deposited on an insulating layer (not shown) covering the ring electrodes 224. The insulating layer fills gaps 225 that separate and electrically isolate the ring electrodes 224 from each other. Each gap 225 is approximately the same width (e.g., approximately 3 microns). This insulating layer may optionally extend above the cylindrical face 236 of the stepped surface 222.

[0058] Each bus bar 252 traverses the insulating layer and at least a portion of the stepped surface 222 to a corresponding ring electrode 224 and is connected to the ring electrode 224 through a corresponding hole or through-hole in the insulating layer. Bus bar 252a traverses the annular surface 235, the cylindrical surface 236, and a portion of the circular surface 234 to the innermost (center) ring electrode 224. Bus bar 252b traverses the annular surface 235, the cylindrical surface 236, and a portion of the circular surface 234 to the outermost ring electrode 224 in the first subset 224a of ring electrodes. Bus bars 252a and 252b together connect the first subset 224a of ring electrodes 224 to a first voltage supply 250a, which drives the first subset 224a of ring electrodes 224 with a first voltage. Similarly, bus bars 252c and 252c traverse the annular surface 235 and the outer cylindrical surface 236 to connect the innermost and outermost electrodes, respectively, of the second subset 224b of the ring electrodes 224 to a second voltage supply 250b, which drives the second subset 224b of the ring electrodes 224 with a second voltage. Due to the increased thickness of the liquid crystal, the second voltage can be higher to achieve the same OPD. Some liquid crystals have such a high response rate to voltage that no increase is needed to compensate for the increased thickness.

[0059] Figure 2C Show Figure 2A and 2B A modified version 200' of the liquid crystal lens 200 in FIG. In this modified liquid crystal lens 200', the ring electrodes 224' are formed below the stepped surface 222' rather than on the stepped surface 222. For example, the ring electrodes 224', the resistive bridge, the insulating layer, and the bus may be formed on a flat substrate surface. Once these elements are formed, additional transparent material, such as a resin or photoresist, may be deposited (and optionally patterned) to form the stepped surface 222' on top of the ring electrodes 224'. When the electrodes are positioned below the stepped surface, the voltage must be adjusted upward, as described above. There are still gaps 225' between adjacent electrodes 224', but those gaps are covered by this additional (insulating) material. The stepped surface 222' is formed so that there are multiple ring electrodes per step. When viewed along the optical axis 201 of the lens, the ring electrodes 224' form a substantially uniform distribution of the ring electrodes 224'. Figure 1A and 2A The patterns used in the liquid crystal lenses 100 and 200 shown in FIG. 1 are similar or identical patterns.

[0060] Figure 3A cross-section of an inventive liquid crystal lens 300 is shown, having liquid crystal material 340 sealed between curved transparent substrates 310 and 320. This liquid crystal lens 300 is a convex-concave lens having a convex outer surface 318 and a concave outer surface 328. In this shape, when made of appropriate materials and having appropriate dimensions, lens 300 is suitable for use as a contact lens or an eyeglass lens. The inventive liquid crystal lens can also have two convex outer surfaces, for example for use as an intraocular lens, or two concave outer surfaces. In any case, the outer surfaces can be spherical segments or more complex shapes, including aspherical shapes, to provide fixed optical power for the lens. The outer surfaces can also be shaped to correct for aberrations (e.g., astigmatism in the patient's eye) or to provide multiple focal lengths, as in bifocal, trifocal, or progressive lenses.

[0061] The inner surfaces of substrates 310 and 320 are also curved. In this case, the upper substrate 310 has a smooth concave inner surface 312, and the lower substrate has a convex stepped inner surface 322. Together, the inner surfaces form a sealed cavity that holds the liquid crystal material 340. Depending on the desired switchable optical properties of the lens 300, the inner surface of the upper substrate can be planar, convex, or have a more complex shape. Likewise, the stepped inner surface 322 can have a shape similar to Figure 1A 、 1B 2A-2C, or angled or concave steps, again depending on the desired switchable optical properties of lens 300. In this example, stepped surface 322 forms three steps 331-333 that form faces that appear circular (334) and annular (335) but slightly curved (convex) when viewed along lens optical axis 301. Each of these faces can abut its adjacent face or an intervening cylindrical face 336.

[0062] The conductive layer on the stepped surface 322 forms a ground plane electrode 324. The lens 300 also includes ring electrodes 312 on the concave inner surface 312 of the upper substrate 310. These ring electrodes 314 are separated by gaps 315 and have a Figure 4 The steps shown in FIG3 (described below) are aligned to reduce and increase widths in the circuit. The ring electrode 314 and gap 315 can be covered with an insulating layer (not shown). A bus and / or a resistor bridge (not shown) connects the ring electrode 314 to a controller or other voltage supply or voltage supply group. Alternatively, the ring electrode can be on or below the stepped surface 322, with the ground plane on the concave inner surface 312 of the upper substrate, as shown in FIG3. Figures 2A-2C .

[0063] Exemplary design process of multi-depth liquid crystal lenses

[0064] When designing the electrode structure of a liquid crystal lens, several factors should be considered. These factors include: (1) the diameter of the lens; (2) the thickness of the central region of the liquid crystal layer (the thinnest part of the liquid crystal layer); (3) the available birefringence (refractive index variation) of the liquid crystal; (4) the minimum allowable width of the electrode (usually set by the photolithography process used to make the electrodes); (5) the minimum number of electrodes required in the lens; (6) the total available optical path difference (OPD); and (7) the design wavelength of the lens.

[0065] Consider the following example design process for a desired lens with a diameter of 30 mm, a starting thickness of the liquid crystal of 10 microns (0.010 mm), a usable birefringence (refractive index variation) of 0.22 (e.g., 1.5 to 1.72) of the liquid crystal, a minimum allowable electrode width of 500 microns, and a minimum number of electrodes in the lens of 15. More than the minimum number of electrodes is required, but less than the minimum number is not required. The design wavelength is 550 nm (green).

[0066] In this example, the first step is to determine the width of the electrode ring group using the same process used to design a liquid crystal lens without a stepped surface. Although the minimum required number of electrodes is 15, calculating the width of 15 electrodes shows that the outermost electrode does not meet the minimum required width. By increasing the number of electrodes to 20, at least eleven inner electrodes meet the required minimum width. The liquid crystal thickness and width and the number of outer electrodes can be adjusted to compensate as described below. Each electrode should have the same surface area as all other electrodes. This is calculated by determining the entire surface area of ​​the lens and dividing by the required number of electrodes. In this example, the entire surface of a 30mm diameter lens is 706.86mm 2 When this value is divided by 20, each electrode should have a diameter of 35.343 mm. 2 of surface area. (The gaps between the electrodes are small enough to be ignored at this stage of the design process.)

[0067] The outer diameter of the outermost ring electrode is set to the desired lens diameter, which in this case is 30 mm. The inner diameter of the outermost ring electrode is calculated by subtracting the desired surface area of ​​the outermost ring electrode from the total lens surface area, then dividing by π and taking the square root of the quotient to obtain the inner radius of the outermost ring electrode. Double this radius to obtain the inner diameter of the outermost ring electrode. In this example, the total surface area of ​​706.86 square millimeters is subtracted from the 35.343 mm of the single electrode. 2 The required area is 671.52mm within the outer electrode 2The surface area of ​​the ring electrode is calculated, which corresponds to an inner radius of 14.62 mm and an inner diameter of 29.24 mm. This process is repeated until all electrodes are calculated, where the inner diameter of each ring electrode is smaller than the gap between the electrodes, which serves as the outer diameter of the next inner ring electrode. (If desired, the innermost electrode can be circular.)

[0068] Table 1 shows the results of these calculations, where ring electrode No. 1 is the innermost electrode and ring electrode No. 20 is the outermost electrode. Table 1 shows that only the central eleven electrodes (electrodes No. 1-11) meet the minimum width requirement of 0.5 mm, while the remaining nine electrodes (electrodes No. 12-20) do not meet this requirement.

[0069]

[0070] Table 1: Starting Ring Electrode Width (Conventional Liquid Crystal Lens)

[0071] The first part of the solution to this design problem of making each electrode at least 0.5 mm wide is to make the No. 12 electrode wider and then restart the electrode design calculations so that the No. 13+ electrodes have the same area as the wider No. 12 electrode. But before doing so, we should consider the available OPD to ensure that the electrode to OPD ratio is sufficient to provide the required optical power and wavefront smoothness.

[0072] The available OPD for this design is calculated by multiplying the thickness of the liquid crystal layer by its available birefringence and then dividing by the design wavelength. In this case, a central 10 micron thickness multiplied by an available birefringence of 0.22 yields an optical retardation of 2.2 microns. 2.2 microns of retardation divided by the design wavelength of 550 nm (green) shows that an OPD of four waves is available. However, the OPD is insufficient to provide the required optical power with the desired wavefront smoothness by simply increasing the width of electrodes 12-20. In a stepped manner, optical power can be achieved, but the wavefront will be quite rough.

[0073] The second part of the solution is to increase the available OPD. This is achieved by increasing the thickness of the liquid crystal layer at a radius greater than the outer radius of electrode 11, then repeating the electrode design process outlined above, but this time starting with the inner diameter of electrode 12, which is the outer diameter of electrode 11 in Table 1. In other words, a second step or layer of electrodes with a radius greater than the outer radius of electrode 11 is created, where the electrodes on the second step have a width of 0.5 mm or greater.

[0074] To meet the design goal of at least 15 electrodes, the area of ​​each electrode of the second step is set to the area of ​​the second step divided by four (a total of 15 electrodes minus the 11 inner electrodes on the first / center step). This calculation gives each of the four electrodes a width of 79.53 mm. 2Table 2 shows the width and radius of the four electrodes on the second step, as well as the radius and width of the No. 11 ring electrode (the outermost electrode on the first step) and the first electrode whose radius is larger than the required lens radius:

[0075] Electrode number area Outer radius (mm) Electrode width (mm) Remark 11 388.77 11.12 0.52 First step 12 468.29 12.21 1.08 Second step 13 547.81 13.21 1.00 14 627.34 14.13 0.93 15 706.86 15.00 0.87 outermost 16 786.38 15.82 0.82 Exceeds the lens radius

[0076] Table 2: Ring electrode radius and width of the second step

[0077] Table 3 shows the final electrode radius and width of the stepped lens, where electrode No. 1 is the innermost (center) electrode and electrode No. 15 is the outermost electrode:

[0078]

[0079]

[0080] Table 3: Final Ring Electrode Width

[0081] We then determined the increase in thickness of the liquid crystal layer above the second step by calculating the increase in width of the first thickened electrode from the previously thinner electrode and increasing the liquid crystal layer thickness proportionally. In this example, the increase in thickness is a factor of 2.08, which translates to an increase in OPD (and step height) of 10.8 microns for a new total thickness of 20.8 microns.

[0082] In other lenses, the number of electrodes can be much larger, for example, 100, 200, 300, or more in a 30 mm diameter lens. Each step can be one or more wavelengths higher than the next outer step. Slower increases will produce more steps, while larger increases will produce fewer steps. For example, a 30 mm lens with a starting OPD of 3 waves and increments by one wave each time will have five steps. If the increments are 3 waves each time, the lens will have two steps. The above example uses 15 electrodes to illustrate a design approach with a smaller, more easily readable set of values. This allows the thickness of the liquid crystal layer to increase by a non-integer amount (a factor of 2.08). Alternatively, the increase in OPD / step height can be done by integer multiples of the design wavelength to increase diffraction efficiency. If the step height is set to an integer multiple of the design wavelength, the lens diameter may not be exactly the desired value. However, with a larger number of electrodes, such as 300 electrodes in a 30 mm diameter lens, the difference becomes negligible, and the target 30 mm diameter may be missed by only a few tens of microns.

[0083] The final design step is to adjust the inner and outer radius of the electrodes to provide a gap between the electrodes, thereby eliminating electrical contact between the electrodes. Each electrode can be powered by a voltage different from the voltage applied to the adjacent electrode, so the gap prevents electrical shorting. The typical gap width is 3 microns, so the radius value of each electrode is adjusted by 1.5 microns (that is, the inner radius increases by 1.5 microns and the outer radius decreases by 1.5 microns). Although the typical gap is currently 3 microns, as lithography technology improves, this gap can be reduced.

[0084] While a 30mm diameter lens typically has 300 electrodes, this number is a result of limitations in photolithography. Generally, the more electrodes, the better, as the wavefront steps are much smaller. As photolithography advances, the number of electrodes can be increased from hundreds to thousands or more.

[0085] Example voltages applied to the example lens design are as follows:

[0086] Electrode number Fu 1 1.87 2 1.66 3 1.51 4 1.36 5 1.23 6 1.11 7 1.00 8 0.94 9 0.86 10 0.81 11 0.75 12 0.71 13 0.66 14 0.62 15 0.57

[0087] Table 4: Ring electrode voltages

[0088] Ring electrodes and resistance bridges

[0089] Figure 4 The optical axis 101, 201 and 301 of the lens is shown as shown by the ring electrodes 114, 224, 224' and 314 and Figure 1A 、 2A 2C and 2C and described above. The dotted lines represent the boundaries or transitions between the first steps 131, 231, and 331 and the second steps 132, 232, and 332, and between the second steps 132, 232, and 332 and the third steps 133, 233, and 333. In this pattern, there are four ring electrodes per step, and there are three steps in total. Other suitable patterns may have more or fewer steps and / or more or fewer ring electrodes per step. Generally, more ring electrodes provide finer control over the focal length of the lens and better spatial resolution. And more steps can achieve larger diameter lenses. In today's state of photolithography, a reasonable range of electrodes per step is between 30 and 100, with each lens having one, two, three, four, or five steps. As photolithography technology advances, these numbers may increase.

[0090] The ring electrode width varies with the radius and the number of steps, but the gaps are all approximately the same width. The gap width can be set to a minimum width (e.g., approximately 3, 4, or 5 microns) that provides the desired electrical isolation between adjacent ring electrodes and can be patterned, for example, using photolithography or other techniques. With the current state of photolithographic liquid crystal birefringence technology, the ring electrode width can range from 5 mm to 15 μm, while the step height can range from 1 μm to 30 μm.

[0091] Figure 4 Also shown are two buses 452a and 452b (collectively referred to as buses 452) that connect the innermost and outermost ring electrodes on the first step, respectively, to voltage supply terminals on a controller or voltage supply. Other buses (omitted for clarity) connect at least the innermost and outermost ring electrodes on other steps to other voltage supply terminals on a controller or other voltage supply. For lenses with more ring electrodes per step, additional buses can also connect to the intermediate ring electrodes. As described above, these buses 452 are on a transparent insulating layer (not shown) that is on top of the ring electrodes and fills the gaps between the ring electrodes. Each bus 452 is connected to a corresponding ring electrode through a hole or through-hole in the insulating layer.

[0092] A resistive arc or curved resistor bridge 460 connects the ring electrodes on each step. Resistive bridge 460 acts as a voltage divider network, connecting the innermost ring electrode on each step to the outermost ring electrode on each step. The voltage applied by bus 452 drops across resistor bridge 460 in proportion to its resistance, creating a voltage gradient across the ring electrodes. This voltage gradient creates a corresponding refractive index gradient in the liquid crystal material, thereby imparting optical power to the lens.

[0093] Each resistive arc 460 can be formed as a thin, curved strip of resistive material, such as ITO, carbon nanotubes, silver nanowires, or a similar material that is conductive and optically transmissive, that spans the gap between the inner and outer ring electrodes to connect points on the outer edge of the inner ring electrode with points on the inner edge of the outer ring electrode. These points can be separated from each other in azimuth (i.e., in cylindrical coordinates where the optical axis of the lens coincides with the cylindrical z-axis, the ends (terminals) of the resistive arcs can have different angular coordinates θ). This angular separation can range from a few degrees (e.g., 1°, 5°, or 10°) to 360° or more, corresponding to resistive arcs that follow a spiral path between the electrodes. These resistive arcs are referred to as "spiral" resistive arcs. In Figure 4 , the resistive arcs 460 each subtend an angle of 90. The resistive arcs 460 are evenly distributed across the angle, but other subtending angles and angular distributions are possible.

[0094] The arc length of the resistive arc depends on the angular separation between its end and the electrode radius. Typically, the resistive arc 460 can span any specified length from 1 micron to 10 cm. Several resistive arcs each having a different average radius can be connected in series by the same resistive arc material of short lengths. These short lengths can be oriented at almost any desired rotation angle. The resulting spiral resistive arc can span one or more (e.g., two, five, or ten) rotations around the inner electrode to provide higher resistance (and lower power dissipation). Typically, when all other things are equal, the larger the length of the spiral resistive arc, the higher its effective resistance is for a given arc width. In other words, a high ratio of the length to width of the resistive arc produces higher resistance.

[0095] For a helical resistive arc consisting of a single rotation around the inner radius of the electrode, the limiting factor in its length is the circumference of the electrode, which can be several orders of magnitude greater than the arc width (that is, the coplanar dimension perpendicular to the length and / or direction of the arc at any given point along the arc). This length can be further increased by promoting a resistive arc consisting of subsequent additional rotations (and / or partial rotations) around the inner radius of the electrode. The maximum length is limited by the number of rotations, which is limited by the width and circumference of the electrode.

[0096] The gap between the electrodes may be approximately 1.5 microns wide, but the gap and / or resistive arc width may range from 0.1 microns to 10 microns, including any and every value and subrange therebetween (e.g., 0.242, 0.50, 0.7673, 1.0, 1.22, and 1.43 microns). The electrodes, gap, and / or resistive arc may be formed by, for example, photolithography, etching, printing (e.g., printing of a conductive polymer), self-assembly, lift-off, laser ablation, and / or any other method of thin film patterning. When photolithography is used, it may involve proximity lithography, contact lithography, projection lithography, interference lithography, maskless lithography, electron beam lithography, and / or another other lithographic technique. When etching is used, it may involve wet (liquid-based) etching and / or dry (plasma-based) etching.

[0097] The resistance of each resistive arc can be equal between each electrode connected. This can be achieved by choosing the lengths of the resistive arcs to be the same or nearly the same (e.g., 50 microns each) rather than preserving the angular size (e.g., Figure 4 Setting the resistive arc to a uniform length ensures uniform resistance between the electrodes.

[0098] The spiral nature of the spiral resistive arc can minimize distortion of the wavefront by the lens. The voltage in the region of the spiral resistive arc along the length (direction of travel) of the arc can vary between the voltages of the two connected electrodes. As a result, the refractive index in the arc region can vary between the refractive index in each of the two electrode regions connected by the arc, thereby causing minimal disruption to the wavefront profile. Etched regions of the conductive material forming the arc can experience fringing fields from the electrodes and / or the resistive arc, which can minimize disruption.

[0099] Figure 5A is a view taken along the optical axis showing (at this magnification level) a plurality of annular electrodes 3200 suitable for use in a liquid crystal lens having a stepped or layered internal substrate surface. The annular electrodes 3200 (at this magnification level) are substantially separated by a plurality of substantially annular non-conductive gaps 3300. In addition, Figure 5A Shown is a voltage supply connection (bus) 3700 and a spiral shaped gap 3400 having a non-overlapping portion 3410 (partially visible in this view) and an overlapping portion 3420. The voltage supply connection 3700 connects the inner electrode 3200 to a voltage supply (not shown).

[0100] Figure 5B 44 is a close-up of a pair of conductive and / or resistive adjacent electrodes 4110 and 4120 suitable for actuating liquid crystal above a step in an inventive liquid crystal lens. Electrodes 4110 and 4120 are substantially separated by a gap 4400, which defines a single-gap non-overlapping portion 4410 and a double-gap overlapping portion 4420. Gap 4400 can be visualized as starting at a starting end 4430 and ending at an ending end 4440, with an abrupt change in radius at location 4450. Overlap portion 4420 defines a (curved) overlap length 4490.

[0101] Between the dual gaps of overlapping portion 4420 is a spiral arc 4500 having a (bend) arc length 4590. Arc 4500 can be formed from the same material as adjacent electrodes 4110 and 4120 and can therefore provide a conductive and / or resistive connection between those electrodes, which can allow current to flow from electrode 4110 through arc inlet 4540, along arc 4500 length 4590, around arc corner 4560, and out of arc outlet 4550 to electrode 4120, and / or in the reverse direction. The longer the bend length 4490, the longer the arc length 4590, and thus the greater the resistance provided by spiral arc 4500. Similarly, the closer the dual gaps of overlapping portion 4420 are, the narrower the arc 4500 is, and the greater the resistance provided by spiral arc 4500. The change in radius of the gap 4400 as it transitions from the non-overlapping portion 4410 to the overlapping portion 4420 can be abrupt, as shown at gap corner 4460, or more gradual, occurring over any desired portion (and up to the entire length) of the non-overlapping portion 4410. Similarly, the arc 4500 can have a substantially constant radius and / or can have breaks and / or discontinuities, such as shown at arc corner 4560.

[0102] Figure 6A 51 is a view along the optical axis at electrodes 5110 and 5120 suitable for use in an inventive liquid crystal lens. These electrodes 5110 and 5120 (as seen at this level of magnification) are essentially separated by a spiral gap 5400 with an overlapping portion spanning several turns.

[0103] Figure 6B yes Figure 6A 5420. This figure shows adjacent electrodes 5110 and 5120 substantially separated by a spiral gap 5400 having an overlap 5420 spanning several revolutions. This structure appears to include three gap rings 5422, 5424, and 5426. The geometry of the overlap 5420 of gap 5400 substantially defines the geometry of spiral arc 5500, at least in a plane perpendicular to the optical axis. The geometry of spiral arc 5500 in the direction of the optical axis can be controlled by the depth of electrode layer 5100. In this example, given the geometry of the spiral arc 5500, current can flow from the electrode 5110 through the arc inlet 5550, along the first radial portion 5555, around the first corner 5560, along the first arc portion 5562, around the second corner 5572, along the second radial portion 5574, around the third corner 5576, along the second arc portion 5564, around the fourth corner 5582, along the third radial portion 5584 and out of the arc outlet 5540 to the electrode 5120. The gap width Wg can be constant or can vary along the gap 5400. Similarly, the arc width Wa can be constant or vary along the arc 5500.

[0104] Figure 7-9 Additional aspects of the resistive bridge geometry are shown. Figure 7 Adjacent electrodes 7110 and 7120 are shown substantially separated by a spiral gap 7400 that defines a substantially constant arc width Wa at each position along the spiral arc 7500. In contrast, Figure 8 , adjacent electrodes 8110 and 8120 are substantially separated by a spiral gap 8400 having a varying arc width Wa. Figure 9 Electrodes 9110 and 9120 are shown substantially separated by a spiral-shaped gap 9400 that varies in width from a relatively thin width Wg1 at the innermost turn of gap 9400 to a relatively wider width Wg2 at the outermost turn of gap 9400 .

[0105] Lens electronics

[0106] Each inventive liquid crystal lens (e.g., lenses 100, 100', 200, 200', and 300 described above) can include or be coupled to electronics for actuating the liquid crystal material to change the focal length of the lens. The control electronics provide an alternating current, such as a sine wave or square wave oscillating at a frequency of 1 Hz to 20 kHz and a peak-to-peak amplitude ranging from zero volts to 500 volts. These electronics can include sensors, such as a rangefinder or tilt switch, that detect the position at which the person wearing the lens is looking. The electronics can also include a wireless interface, including an antenna and a transceiver, for receiving wireless commands to change the focus from an external device, such as a key fob or smartphone, controlled and actuated by the wearer, and for transmitting device information to the external device. The antenna can take the form of a ring or annular metal piece positioned along or near the outer edge of the lens.

[0107] The wireless interface and optional sensors are coupled to a processor or controller, such as a suitable microprocessor or integrated circuit, which applies voltage directly to the ring electrodes or actuates one or more voltage supplies that apply voltage to the ring electrodes. The processor, wireless interface, optional sensors, and optional voltage supply are powered by a battery, capacitor, or other suitable power source, which can be recharged using inductive or magnetic resonance charging via the antenna or another coil. The electronics containing the antenna and optional separate charging coil can be embedded in one of the substrates of the lens or sandwiched between the substrates. The antenna and / or optional separate charging coil can also be located on the surface of one substrate or along a seam between substrates and connected to the electronics via one or more conductive traces.

[0108] Conclusion

[0109] Although various inventive embodiments have been described and illustrated herein, a person of ordinary skill in the art will readily conceive of a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more advantages described herein, and each of such variations and / or modifications is considered 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 exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend on the specific application or applications for which the invention is taught. 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.

[0110] It will be understood that the foregoing embodiments are presented by way of example only, and that within the scope of the appended claims and their equivalents, inventive embodiments may be practiced in a manner different from that 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.

[0111] Furthermore, various inventive concepts can be embodied as one or more methods, examples of which have been provided. The actions performed as part of a method can be ordered in any suitable manner. Thus, embodiments can be constructed in which actions are performed in an order different from that illustrated, which can include performing some actions simultaneously, even though actions are shown as sequential in an illustrative embodiment.

[0112] 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.

[0113] As used herein in the specification and claims, the indefinite articles "a" and "an" should be understood to mean "at least one" unless explicitly indicated to the contrary.

[0114] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "either one or both" of the elements so combined, i.e., the elements are present in combination in some cases and separately in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., "one or more" of the elements are so combined. In addition to the elements specifically indicated by the "and / or" clause, other elements may optionally be present, whether related or unrelated to those specifically indicated. Thus, as a non-limiting example, when used in conjunction with open language (e.g., "comprising"), a reference to "A and / or B" may refer to only A (optionally including elements other than B) in one embodiment; to only B (optionally including elements other than A) in another embodiment; to both A and B (optionally including other elements) in yet another embodiment; and so on.

[0115] As used herein in this specification and claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating multiple items in a list, "or" or "and / or" will be interpreted as inclusive, that is, including at least one, but also including more than one element in several elements or element lists and optionally additional unlisted items. Only terms that clearly indicate the opposite, such as "only one of..." or "exactly one of..." or "consisting of..." when used in the claims will refer to including exactly one element in multiple elements or element lists. In general, the term "or" as used herein, when preceded by exclusive terms such as "any one of," "one of...", "only one of..." or "exactly one of...", should only be interpreted as indicating exclusive alternatives (i.e., "one or the other but not both"). "Substantially consisting of..." when used in the claims, should have the ordinary meaning as used in the field of patent law.

[0116] As used herein in the specification and claims, when referring to a list of one or more elements, the phrase "at least one" should be understood to refer to at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether or not related to those elements specifically identified. Thus, as a non-limiting example, in one embodiment, "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 to at least one, optionally including more than one A, without B (and optionally including elements other than B); in another embodiment, can refer to at least one, optionally including more than one B, without A (and optionally including elements other than A); in yet another embodiment, can refer 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.

[0117] In the claims and throughout the foregoing description, all transitional terms such as "comprises," "comprising," "with," "having," "containing," "involving," "containing," "consisting of," and the like are to be construed as open-ended, i.e., meaning 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 provided in Section 2111.03 of the United States Patent Office Manual of Patent Examining Procedures.

Claims

1. An electro-active lens comprising: a first substrate having a uniform surface; a second substrate having a stepped surface opposite the uniform surface, the stepped surface having at least a first step and a second step, the first step being separated from the uniform surface by a first distance, the second step being further away from the optical axis of the electro-active lens than the first step and being separated from the uniform surface by a second distance, the second distance being greater than the first distance; a liquid crystal material disposed between the uniform surface and the stepped surface; a ground electrode disposed on one of the uniform surface or the stepped surface; as well as A plurality of ring electrodes are disposed on the other of the uniform surface or the stepped surface for applying a voltage on the liquid crystal material, the plurality of ring electrodes including at least two ring electrodes for the first step and at least two ring electrodes for the second step.

2. The electro-active lens of claim 1 , wherein the uniform surface is a planar surface.

3. The electro-active lens of claim 1 , wherein the uniform surface is a curved surface.

4. The electro-active lens of claim 1 , wherein the stepped surface is formed by stacking cylinders of different diameters concentric with an optical axis of the electro-active lens.

5. The electro-active lens of claim 1 , wherein the first step is taller than the second step by a height selected to provide an optical path distance equal to an integer number of waves at a design wavelength of the electro-active lens.

6. The electro-active lens of claim 1 , wherein the first step has a circular surface opposite the uniform surface and centered on the optical axis of the electro-active lens, and the second step has an annular surface concentric with the circular surface and opposite the uniform surface.

7. The electro-active lens of claim 6 , wherein the ground electrode is disposed on the stepped surface and the plurality of ring electrodes are disposed on the uniform surface, wherein the at least two ring electrodes for the first step are opposite the circular face, and the at least two ring electrodes for the second step are opposite the annular face.

8. The electro-active lens of claim 6 , wherein the ground electrode is disposed on the uniform surface and the plurality of ring electrodes are disposed below the stepped surface, wherein the at least two ring electrodes for the first step are below the circular face and the at least two ring electrodes for the second step are below the annular face.

9. The electro-active lens of claim 6 , wherein the ground electrode is disposed on the uniform surface and the plurality of ring electrodes are disposed on the stepped surface, wherein the at least two ring electrodes for the first step are on the circular face and the at least two ring electrodes for the second step are on the annular face.

10. The electro-active lens of claim 9, further comprising: A bus bar is disposed on a cylindrical surface connecting the circular surface and the annular surface to connect at least one of the at least two ring electrodes for the first step to a voltage supplier.

11. The electro-active lens of claim 1 , wherein the at least two ring electrodes for the first step comprise a first electrode having a first diameter and a first width, and the at least two ring electrodes for the second step comprise a second electrode having a second diameter greater than the first diameter and a second width greater than the first width.

12. The electro-active lens of claim 1, wherein the plurality of ring electrodes comprises at least ten ring electrodes for the first step and at least ten ring electrodes for the second step.

13. The electro-active lens of claim 1, wherein each of the at least two ring electrodes for the first step has a first area, and each of the at least two ring electrodes for the second step has a second area larger than the first area.

14. The electro-active lens of claim 1 , further comprising: a first resistive bridge connecting two of the at least two ring electrodes for the first step; as well as A second resistive bridge connects two of the at least two ring electrodes for the second step.

15. The electro-active lens of claim 1 , wherein the electro-active lens further comprises: a first spacer bead having a first diameter between the first step and the uniform surface; as well as A second spacer bead has a second diameter greater than the first diameter between the second step and the uniform surface.

16. A method of focusing light using an electro-active lens, the electro-active lens comprising: a first substrate having a uniform surface; a second substrate having a stepped surface opposite the uniform surface and having at least a first step and a second step, the first step being separated from the uniform surface by a first distance, the second step being further away from the optical axis of the electro-active lens than the first step and being separated from the uniform surface by a second distance, the second distance being greater than the first distance; a liquid crystal material disposed between the uniform surface and the stepped surface; and a plurality of ring electrodes, the method comprising: actuating a first portion of the liquid crystal material between the first step and the uniform surface with a voltage applied to at least two inner ring electrodes of the plurality of ring electrodes; as well as A second portion of the liquid crystal material between the second step and the uniform surface is actuated with a voltage applied to at least two outer ring electrodes of the plurality of ring electrodes.

17. An electro-active lens comprising: a first substrate having a uniform surface; a second substrate having a stepped surface opposite the uniform surface, the stepped surface having at least a first step and a second step, wherein a height difference between the first step and the second step is selected to provide an optical path length equal to an integer number of wavelengths at a design wavelength of the electro-active lens; a liquid crystal material disposed between the uniform surface and the stepped surface, the liquid crystal material having a thickness that increases with increasing distance from an optical axis of the electro-active lens; a ground electrode disposed on the stepped surface; as well as A plurality of ring electrodes are disposed on the uniform surface and are used to apply a voltage to the liquid crystal material. The plurality of ring electrodes include at least ten ring electrodes opposite to the first step and at least ten ring electrodes opposite to the second step.

18. The electro-active lens of claim 17, wherein the at least ten ring electrodes opposite the first step include a first electrode having a first diameter and a first width, and the at least ten ring electrodes for the second step include a second electrode having a second diameter greater than the first diameter and a second width greater than the first width.

19. The electro-active lens of claim 17, wherein each of the at least ten ring electrodes for the first step has a first area, and each of the at least ten ring electrodes for the second step has a second area larger than the first area.

20. The electro-active lens of claim 17, wherein the plurality of ring electrodes comprises at least one hundred ring electrodes for the first step and at least one hundred ring electrodes for the second step.

21. The electro-active lens of claim 17, further comprising: a first resistance bridge connecting two of the at least ten ring electrodes opposite the first step; as well as A second resistive bridge connects two of the at least ten ring electrodes opposite the second step.

22. An electro-active lens comprising: a first substrate having a uniform surface; a second substrate having a stepped surface opposite the uniform surface, the stepped surface having at least a first step and a second step, the second step being further away from the optical axis of the electro-active lens than the first step; a liquid crystal material disposed between the uniform surface and the stepped surface, the liquid crystal material having a first thickness between the uniform surface and a first step of the stepped surface, and a second thickness between the uniform surface and a second step of the stepped surface, the second thickness being greater than the first thickness; a ground electrode disposed on the stepped surface; a plurality of first ring electrodes disposed on the uniform surface opposite to the first step, for applying a first voltage to the liquid crystal material, each of the plurality of first ring electrodes having a first area; as well as A plurality of second ring electrodes are disposed on the uniform surface opposite to the second step and are used to apply a second voltage to the liquid crystal material. Each of the plurality of second ring electrodes has a second area larger than the first area.

23. The electro-active lens of claim 22, wherein the plurality of first ring electrodes comprises at least one hundred first ring electrodes, and the plurality of second ring electrodes comprises at least one hundred second ring electrodes.

24. The electro-active lens of claim 22, further comprising: a first resistance bridge connecting two first ring electrodes of the plurality of first ring electrodes; as well as A second resistance bridge connects two second ring electrodes of the plurality of second ring electrodes.

25. An electro-active lens comprising: a first substrate having a curved surface; a second substrate having a stepped surface opposite the curved surface, the stepped surface having at least a first step and a second step, the second step being further away from the optical axis of the electro-active lens than the first step; a liquid crystal material disposed between the curved surface and the stepped surface, wherein the liquid crystal material has a first thickness between the curved surface and a first step of the stepped surface, and a second thickness between the curved surface and a second step of the stepped surface, the second thickness being greater than the first thickness; a ground electrode disposed on the stepped surface; as well as A plurality of ring electrodes are disposed on the curved surface and are used to apply a voltage to the liquid crystal material. The plurality of ring electrodes include at least ten ring electrodes opposite to the first step and at least ten ring electrodes opposite to the second step.

26. The electro-active lens of claim 25, wherein a height difference exists between the first step and the second step, the height difference being selected to provide an optical path length equal to an integer number of wavelengths at a design wavelength of the electro-active lens.

27. The electro-active lens of claim 25, wherein the at least ten ring electrodes opposite the first step include a first electrode having a first diameter and a first width, and the at least ten ring electrodes opposite the second step include a second electrode having a second diameter greater than the first diameter and a second width greater than the first width.

28. The electro-active lens of claim 25, wherein each of the at least ten ring electrodes opposite the first step has a first area, and each of the at least ten ring electrodes opposite the second step has a second area greater than the first area.

29. The electro-active lens of claim 25, wherein the plurality of ring electrodes comprises at least one hundred ring electrodes opposite the first step and at least one hundred ring electrodes opposite the second step.

30. The electro-active lens of claim 25, further comprising: a first resistance bridge connecting two of the at least ten ring electrodes opposite the first step; as well as A second resistive bridge connects two of the at least ten ring electrodes opposite the second step.

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