Fast electroactive lens switching systems and methods

Abstract

A conventional liquid crystal lens is switched on and switched off very slowly, so that people can sense that the lens is gradually switched from high optical power to low optical power. This makes conventional liquid crystal lenses unsuitable for fast focusing virtual images in augmented, hybrid, or virtual reality systems. Instead, a fast switching electro-active lens system of the present invention can switch very fast (e.g., within 35 milliseconds or less) such that people perceive instantaneous changes in optical power of the system. The system achieves such fast switching by using an electroactive wave plate in series with a slower liquid crystal lens. The wave plate can be quickly switched between emission of vertical or horizontal polarized light. Each lens focuses vertically or horizontally polarized light and transmits orthogonally polarized light. By switching between polarization states, the speed at which the wave plate effectively opens one lens and closes the other lens is much faster than the speed at which either lens itself is switchable.

Description

[0001] This application is a divisional application of the Chinese patent application number 202080096643.4 (application date: 2020 / 12 / 30, invention name: Rapid electro-active lens switching system and method).

[0002] Cross-reference to related applications

[0003] This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Application No. 62 / 954,743, filed on December 30, 2019, which is incorporated herein by reference in its entirety. Background Art

[0004] Electro-active lenses can be used to adjust the focus of the human eye to a digital image presented in an augmented or virtual reality display. The digital image is located at a fixed virtual position from the eye, but at varying simulated distances. Typical electro-active lenses are low-mass and low-volume and consume little energy, but they do not switch optical power rapidly. A typical 30- to 40-millimeter-wide electro-active lens requires hundreds of milliseconds to switch from one optical power to another. This delay is noticeable to the user and degrades the quality of the visual experience. Summary of the Invention

[0005] An electro-active lens system of the present invention can be (and appears to be) switched from one optical power to another in tens of milliseconds or faster rather than hundreds of milliseconds. This is achieved using a pair of electro-active lens elements (also referred to as electro-active lenses) configured to operate on light in orthogonal polarization states (e.g., horizontal and vertical polarization states) and a dynamic polarization switcher that can switch the light between those orthogonal polarization states in tens of milliseconds. For example, the first electro-active lens element can be configured to focus horizontally polarized light but not vertically polarized light, and the second electro-active lens element can be configured to focus vertically polarized light but not horizontally polarized light. Even if the electro-active lens elements are opened and closed slowly, for example, in hundreds of milliseconds, the polarization adjuster can switch the light between horizontal and vertical polarization states in tens of milliseconds. If the first electro-active lens element and the second electro-active lens element have different optical powers, the polarization adjuster can effectively change the optical power of the lens in tens of milliseconds by quickly switching the light between horizontal and vertical polarization states.

[0006] Although optical power should be switched in tens of milliseconds or less, the time between switching events is rarely brief. In practice, the time between switching events can be seconds or longer. The difference between the time required to switch an electro-active lens and the time between switching events can be exploited to increase the switching speed of a device having a fast polarization adjuster (also known as a polarization orientation changer or variable retarder) and one or more slower focus changing devices (electro-active or liquid crystal lens elements). By combining a fast polarization changing component with one or more slower focus changing components (e.g., a first electro-active lens element and a second electro-active lens element), the polarization changing components allow the optical power of only one focus changing component to be "optically present" in the optical system at a time. While one focus changing device is optically present, the other focus changing component is not, and vice versa. Because the polarization changing components can quickly switch incident light from one polarization orientation to another, the system can quickly switch from one focus changing component to another without moving parts. In a fast-changing electro-active lens system with only a single focus changing element, the system can quickly switch from a "lens on" state to a "lens off" state. There is no limit to the number of focus changing elements that can be used in a single electro-active lens system.

[0007] An electro-active lens system of the present invention may include a polarization converter, a first electro-active lens in optical communication with the polarization converter, and a second electro-active lens in optical communication with the polarization converter and the first electro-active lens. The polarization converter is switchable between a first state and a second state, in which the polarization converter switches the polarization of light between a first polarization state and a second polarization state (e.g., orthogonal linear polarization states), and a second state in which the polarization converter transmits light in the first polarization state. The first electro-active lens is switchable between a first focus state and a first transmission state, in which the first focus state the first electro-active lens focuses light in the first polarization state and transmits light in the second polarization state, and in which the first transmission state the first electro-active lens transmits light in the first polarization state and the second polarization state. Furthermore, the second electro-active lens is switchable between a second focus state and a second transmission state, in which the second focus state the second electro-active lens transmits light in the first polarization state and focuses light in the second polarization state, and in which the second transmission state the second electro-active lens transmits light in the first polarization state and the second polarization state.

[0008] The polarization switcher may include a liquid crystal wave plate and may have a delay of π / 2 in a first state and a delay of 0 in a second state. The polarization switcher may be configured to switch between the first state and the second state (i) faster than the first electro-active lens is configured to switch between the first focused state and the first non-focused state, and (ii) faster than the second electro-active lens is configured to switch between the second focused state and the second non-focused state. For example, the polarization switcher may switch between the first state and the second state in 100 milliseconds, 50 milliseconds, 35 milliseconds, 30 milliseconds, 25 milliseconds, 20 milliseconds, 15 milliseconds, 10 milliseconds, 5 milliseconds, or faster. Similarly, the first electro-active lens and the second electro-active lens may each be configured to switch between their respective focused and non-focused states in more than 100 milliseconds.

[0009] The polarization switcher and the electro-active lens can be integrated together, for example, without an air gap between the components. For example, the polarization switcher and the first electro-active lens can share a first common substrate. Similarly, the first electro-active lens and the second electro-active lens can share a second common substrate.

[0010] This electro-active lens system can be used or operated by: setting a polarization switcher to a first state or a second state; setting the first electro-active lens to a first focused state or a first non-focused state; setting the second electro-active lens to a second focused state or a second non-focused state; and sending light through the polarization switcher, the first electro-active lens, and the second electro-active lens. If the polarization switcher is in the first state, the first electro-active lens is in the first focused state, and the second electro-active lens is in the second non-focused state, the second electro-active lens can be switched from the second non-focused state to the second focused state, while the system transmits light in the first polarization state through the polarization switcher, focuses the light with the first electro-active lens, and transmits the light through the second electro-active lens without the second electro-active lens focusing the light. After the second electro-active lens is switched from the second non-focused state to the second focused state, the polarization switcher can be switched from the first state to the second state, thereby causing the second electro-active lens to focus the light and causing the first electro-active lens to transmit the light without focusing the light. The second electro-active lens can be switched from the second non-focused state to the second focused state and the polarization switcher can be switched from the first state to the second state in response to the desired change in the position of the virtual image. Switching the second electro-active lens from the second non-focused state to the second focused state can take at least 100 milliseconds, and switching the polarization switcher from the first state to the second state can take less than 100 milliseconds.

[0011] Another electro-active lens system includes a liquid crystal wave plate optically connected in series with a first liquid crystal lens and a second liquid crystal lens. The liquid crystal wave plate is switchable between zero wave retardation and half wave retardation within 35 milliseconds. The first liquid crystal lens is switchable between a first state, in which it focuses light in a first linear polarization state onto a first focal plane, and a second state, in which it focuses light in the first linear polarization state onto a second focal plane. The second liquid crystal lens is switchable between a first state, in which it focuses light in a second linear polarization state, orthogonal to the first linear polarization state, onto a third focal plane, and a second state, in which it focuses light in the second linear polarization state onto a fourth focal plane.

[0012] The liquid crystal wave plate and the first liquid crystal lens may share a first common substrate, and the first liquid crystal lens and the second liquid crystal lens may share a second common substrate. The first liquid crystal lens and the second liquid crystal lens may transmit light in the second linear polarization state and the first linear polarization state, respectively. The first liquid crystal lens may take more than 35 milliseconds (e.g., 100 milliseconds or more) to switch between the first state and the second state.

[0013] The electro-active lens system may further include a display in optical communication with the liquid crystal wave plate and configured to emit light in a first linear polarization state. Furthermore, the electro-active lens system may include a processor operably coupled to the liquid crystal wave plate, the first liquid crystal lens, the second liquid crystal lens, and the display, and configured to control retardation of the liquid crystal wave plate, the first liquid crystal lens, the second liquid crystal lens, and the display.

[0014] 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

[0015] 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).

[0016] Figures 1A-1C Markings for linearly polarized light are shown.

[0017] Figures 2A-2C Marks showing the liquid crystal alignment (rubbing) direction.

[0018] Figure 3A Shown is an exploded view of an example fast-switching electro-active lens system having a fast polarization changer followed by a pair of slower electro-active lenses.

[0019] Figure 3B An integrated fast-switching electro-active lens system is shown.

[0020] Figure 4A A cross-sectional profile of a fast polarization orientation modulator (variable retarder) is shown in the off state.

[0021] Figure 4B Shows the open state Figure 4A Cross-sectional profile of a fast polarization orientation regulator (variable retarder).

[0022] Figure 5 Shown is a fast switching lens system having a fast polarization changer followed by a pair of slower electro-active lenses, both off (not focusing light).

[0023] Figure 6 Show Figure 5 A fast-switching lens system in which the fast polarization changer is closed (changing the polarization state) and the first electro-active lens is opened (focusing light).

[0024] Figure 7 Show Figure 5 A fast-switching lens system in which the fast polarization changer is on (does not change the polarization state) and the second electro-active lens is on (focuses the light).

[0025] Figure 8 Shown is the process of actuating a fast-switching lens system having a fast polarization changer followed by a pair of slower electro-active lenses in an augmented or virtual reality system. DETAILED DESCRIPTION

[0026] A fast-switching electro-active lens system can change the focus of linearly polarized light from an object, such as a display in an augmented reality headset, in a period of less than 35 milliseconds (e.g., 30, 25, 20, 15, 10, 5, or fewer milliseconds). This is achieved using a combination of a fast-switching waveplate and a slow-switching liquid crystal lens. Each lens has two characteristic axes that are orthogonal to each other and to the lens's optical axis. Each lens focuses light polarized along one characteristic axis (the focus characteristic axis) and transmits light polarized along the other characteristic axis (the transmission characteristic axis). The amount of focus along the lens's focus characteristic axis, i.e., the optical power, depends, among other things, on the liquid crystal thickness and applied voltage and can be tuned continuously (e.g., between -5 and +5 diopters) or switched between two or more discrete states (e.g., between 0 and 5 diopters in 0.5 or 1.0 diopters increments). Each lens can provide no (zero) optical power when off (when no voltage is applied), or can provide non-zero optical power when off. Other ranges and values ​​of optical power are also possible.

[0027] The lenses are aligned so that their optical axes coincide, but their characteristic axes are rotated 90° relative to each other—the focus characteristic axis of the first lens is parallel to the transmission characteristic axis of the second lens, and the transmission characteristic axis of the first lens is parallel to the focus characteristic axis of the second lens. The lens optical axis is aligned and coincident with the optical axis of the waveplate, and the waveplate characteristic axis is aligned with the lens characteristic axis. In other words, when viewed along the surface normal of the waveplate and lens (the optical axis of the fast-switching electro-active lens system), the waveplate and lens have coincident surface normals and aligned characteristic axes.

[0028] Because the lenses are aligned with 90°-rotated focus and transmission characteristic axes, when the system is illuminated by light linearly polarized along one of the system's characteristic axes, one lens focuses the light and the other lens transmits it. Changing the polarization state of the incident light to an orthogonal linear polarization state (e.g., from horizontal to vertical or from +45° to -45°) switches the operation of the lenses. The waveplate changes state much faster than the lenses, making user-observable transitions from one optical power to another much faster than a single lens providing all optical adjustments. And if transitions occur infrequently (e.g., at intervals greater than the lens switching time), one lens can switch between optical power levels while the other lens focuses light, making it ready for the next transition.

[0029] Polarization state and liquid crystal alignment

[0030] Figure 1A 、 1B and 1C show the symbols used in this disclosure to describe different linear polarization orientations or states. Figure 1A The symbol 5 in indicates the direction of the linear polarization as it "enters and leaves the plane of the figure." Figure 1B The symbol 10 in the figure indicates that the direction of the linear polarization is orthogonal to the direction indicated by the symbol 5. In this case, the direction of the linear polarization is "to the left and to the right in the plane of the figure". Figure 1C The symbol 15 in the figure indicates that the direction of the linear polarization is also orthogonal to the direction indicated by the symbol 5. The direction of the linear polarization indicated by the symbol 15 is "upward and downward in the plane of the figure".

[0031] Figure 2A 、 2B 2C show the notation used in this disclosure to describe the orientation of the rubbing or alignment direction of an alignment layer used in a liquid crystal focus shifter (electro-active lens). Figure 2A The symbol 20 in the graph indicates the direction of the rubbing direction as it "enters and leaves the plane of the graph." Figure 2B The symbol 25 in FIG. 2 indicates that the direction of the rubbing direction is orthogonal to the direction indicated by the symbol 20 , and in this case, the direction of the rubbing direction is “to the left and to the right on the plane of the drawing”. Figure 2C The symbol 30 in the figure indicates a rubbing direction that is orthogonal to the directions indicated by symbols 20 and 25, where the rubbing direction is "upward and downward in the plane of the graphic." Each liquid crystal lens typically has two alignment layers—one on either side of the liquid crystal material—and their rubbing directions can be parallel, antiparallel, or orthogonal to each other. In some cases, only one alignment layer may be used to reduce cost. Using two alignment layers increases both switching speed and field of view.

[0032] Figures 1A-1C 2A-2C indicate relative directions. If different figures are from different viewing angles, different symbols can be used to indicate the same polarization state in those figures. Similarly, if different figures are from different viewing angles, the same symbol can be used to indicate different polarization states in those figures. For example, in a side view or profile view of an optical component, the symbol 5 can indicate a horizontal polarization state, and the symbol 10 can indicate a vertical polarization state. In an end view (i.e., a view along the optical axis) of the same optical component, the symbol 10 can indicate a horizontal polarization state, and the symbol 15 can indicate a vertical polarization state.

[0033] Fast electro-active lens switching system

[0034] Figure 3AAn exploded view of a rapidly switching lens system 300 is shown, comprising a polarization orientation converter (also known as a polarization rotator, polarization modulator, or variable retarder) 40 in optical communication with a first electro-active lens 50 and a second electro-active lens 60. The polarization orientation converter 40, the first electro-active lens 50, and the second electro-active lens 60 are optically connected in series or stacked with one another. The lens system 300 can utilize planar liquid crystals, such as Merck MLC-2140, in all three components 40, 50, and 60. The alignment layer of the first electro-active lens 50 is oriented orthogonal to the alignment layer of the second electro-active lens 60. In this case, the first electro-active lens 50 has a horizontally oriented liquid crystal rubbing direction 25, and the second electro-active lens 60 has a vertically oriented liquid crystal rubbing direction 30. Other rubbing directions are also possible (e.g., ±45° rubbing directions) and are typically used when less than 100% focus is desired (in other words, only a portion of the light is focused, while another portion of the light passes through unfocused).

[0035] although Figure 3A The device 300 shown in FIG is a preferred embodiment, but additional polarization switches can be added to add functional control options. For example, Figure 3A The device 300 in can quickly switch between the optical powers of lens 50 and lens 60. If an additional polarization switcher is positioned between lens 50 and lens 60, actuating both polarization switches makes it possible to change the polarization state of light propagating through the system so that both lenses 50, 60 focus the light. More specifically, the first polarization switcher 40 can switch the light from the second polarization state 10 to the first polarization state 15, and the second polarization switcher (not shown) can switch the light from the first polarization state 15 to the second polarization state 10. Alternatively, both polarization switches can be actuated so that neither lens 50, 60 focuses the light, even if one or both lenses are actuated to provide optical power or switch between states. This can be used to provide more optical power than a single lens can provide.

[0036] In operation, linearly polarized light 35 from an object (e.g., a display or spatial light modulator in an augmented or virtual reality system) enters the polarization rotator 40 in a second polarization state (e.g., vertical polarization as shown by symbol 10). If the polarization rotator 40 is in a first state (e.g., closed), as shown in FIG. Figure 3A , it emits light 45 in a first polarization state (e.g., horizontal polarization as shown by symbol 15), which may be rotated 90° relative to the second polarization state. If the polarization rotator 40 is in a second state (e.g., open), it emits light 45 in the same polarization state as the input light 35 (horizontally polarized in this example).

[0037] Light 45 exiting polarization adjuster 40 enters first electro-active lens 50. If light 45 is in a first polarization state (e.g., vertical polarization) and first electro-active lens 50 is in a first state (e.g., open), first electro-active lens 50 focuses light 45 to a first focal plane. If light 45 is in the first polarization state and first electro-active lens 50 is in a second state (e.g., closed), first electro-active lens 50 focuses light to a second focal plane. If light 45 is in a second polarization state (e.g., horizontal polarization), it passes through first electro-active lens 50 without being focused by first electro-active lens 50.

[0038] Light 55 exiting the first electro-active lens 50 enters a second electro-active lens 60, which, like the first electro-active lens 50, is switchable between two states (e.g., open and closed). However, unlike the first electro-active lens 50, the second electro-active lens 60 only operates on light in a second polarization state (e.g., horizontal polarization). When the second electro-active lens 60 is in the first state, it focuses light in the second polarization state onto a third focal plane. And when the second electro-active lens 60 is in the second polarization state, it focuses light in the second polarization state onto a fourth focal plane. Light 55 in the first polarization state (e.g., vertical polarization) passes through the second electro-active lens 60 without being focused by the second electro-active lens 60. Light 65 exits the second electro-active lens 60 and the system 300.

[0039] If the first electro-active lens 50 and the second electro-active lens 60 provide different optical power levels, the lens system 300 can be switched between a range of different optical power level focal lengths by actuating the polarization switch 40, the first electro-active lens 50, and the second electro-active lens 60. For example, if the first electro-active lens 50 can be switched between optical power levels of 0.0 diopters and 1.0 diopters (respectively, a first / on and a second / off state), and the second electro-active lens 50 can be switched between optical power levels of 0.5 diopters and 1.5 diopters (respectively, a first / on and a second / off state), the lens system 300 can be switched between optical power levels of 0.0, 0.5, 1.0, and 1.5 diopters by actuating the polarization switch 40, the first electro-active lens 50, and the second electro-active lens 60. These optical power levels are merely examples; other optical power levels are possible, including unevenly spaced optical power levels, such as optical power levels selected to focus an object at the near plane, near intermediate plane, intermediate plane, far intermediate plane, and / or far plane.

[0040] The fast switching speed of polarization adjuster 40 makes it possible for lens system 300 to switch between these optical power levels quickly (e.g., in 30 ms or less), even though first electro-active lens 50 and second electro-active lens 60 can switch slowly (e.g., in 100 ms or more). For example, when first electro-active lens 50 is open and polarization adjuster 40 is closed, second electro-active lens 60 can transition from one optical power to another without affecting the light propagating through lens system 300. Once second lens 60 has completed its transition and is ready and at the desired optical power, polarization adjuster 40 switches state, causing second electro-active lens 60 to focus light while first electro-active lens 50 no longer focuses light, even though first electro-active lens 50 is still open.

[0041] Figure 3A The components are shown in exploded perspective with gaps between them. Although the lens system can be used with Figure 3A Although the lens system operates with the gap shown in FIG. , it is also possible to manufacture the lens system from components that are adjacent to each other and bonded or integrated together to eliminate reflections at the interface. For example, the first electro-active lens 50 can share a first substrate with the polarization orientation converter 40 and a second substrate with the second electro-active lens 60.

[0042] Figure 3B An integrated fast-switching electro-active lens system 350 is shown. In this system 350, substrates 41 and 43, together with liquid crystal layer 42, form polarization modifier 40. Substrates 43 and 46, together with liquid crystal layer 44, form first lens 50. And, substrates 46 and 48, together with liquid crystal layer 47, form second lens 60. Substrates 43 and 46 are shared by multiple components and, therefore, are coated with separate alignment layers and independently actuated electrodes (not shown) on each side.

[0043] Fast Polarization Adjuster (Variable Retarders)

[0044] Figure 4A and 4B A side view of a cross section of polarization adjuster 40 is shown. Figure 4A The regulator 40 is shown in an unpowered or off (first) state, while Figure 4B The regulator 40 is shown in a powered or open (second) state.

[0045] The polarization adjuster 40 is composed of a first substrate 72 and a second substrate 80, wherein a planar liquid crystal (e.g., Merck MLC-2140 nematic liquid crystal) is sandwiched and sealed between the two substrates 72 and 80. On the surface of the lower substrate 72 is a transparent conductive coating 75, also known as an electrode (e.g., indium tin oxide (ITO)). Above this electrode 75 is a transparent alignment layer (e.g., polyimide made from Nissan Sunever 410 polyimide varnish). The alignment layer is typically applied in the direction of the desired alignment orientation, cured, and then rubbed with a felt cloth. ( Figures 2A-2C Possible rubbing directions for the alignment layer are shown.) Adjacent to the first electrode 75 is the liquid crystal. On the surface of the upper substrate 80 is another conductive coating (electrode) 85, which may be made of the same material from which the first electrode 75 is made.

[0046] Figure 4A The difference between electrodes 75 and 85 is shown: when the polarization adjuster 40 is closed, the alignment layer on the first electrode 75 is configured to align the adjacent liquid crystal molecules in the direction indicated by symbol 25, and the alignment layer on the second electrode 85 is configured to align the adjacent liquid crystal molecules in the direction indicated by symbol 20. Due to this configuration, the liquid crystal molecules are aligned with the first electrode 75 in orientation / direction 25, aligned with the second electrode 85 in orientation / direction 20, and aligned in the middle of the liquid crystal layer in an orientation / direction intermediate between orientation 25 and orientation 20, and the closer the liquid crystal is to the first electrode 75 and the second electrode 85, the closer the liquid crystal is to orientations 25 and 20. This twisted configuration is represented by Figure 4A This twisting of the liquid crystal molecules adjusts or changes the polarization direction of light 105 from polarization orientation 10 when the light enters polarization adjuster 40 to polarization orientation 5 when the light leaves polarization adjuster 40 .

[0047] Figure 4B Polarization adjuster 40 is shown, wherein voltage supply 110 applies an electric field potential to first electrode 75, and an opposite electric field potential is applied to second electrode 85. The applied voltage can be an alternating current (AC) signal, such as a sine wave or a square wave. When power is applied, the liquid crystal molecules are reoriented from orientation 100 to orientation 115, as shown in FIG. Figure 4B . In this state, the polarization orientation 10 of light 105 entering the polarization modifier is the same as the polarization orientation 10 of light 105 when it leaves the polarization modifier. In other words, applying a voltage to electrodes 75 and 85 changes the retardation of the polarization modifier from π / 2 to 0. Polarization modifier 40 does not change the propagation direction of light.

[0048] Other configurations of polarization modifiers are also possible. For example, the alignment layer can have parallel or antiparallel rubbing directions instead of Figure 4A and 4BIn parallel or antiparallel rubbing directions, the polarization modifier does not change the polarization state of incident light when it is off (i.e., when the electrodes are not applying a voltage across the liquid crystal); its nominal retardation is 0. Alternatively, the polarization modifier changes the polarization state of incident light when it is on (i.e., when the electrodes are applying a voltage across the liquid crystal), for example by changing the horizontally polarized light or the vertically polarized light to achieve a retardation change of π / 2.

[0049] The design parameters of the polarization regulator, including the liquid crystal material and the liquid crystal thickness, can be selected to increase the switching speed. The following formula gives an example design that is set to achieve fast switching speed and high optical efficiency. Several example closing times are shown (indicating a preferred liquid crystal thickness of 2.4μm or 5.3μm), however, the opening time can be reduced by using a switching voltage higher than required. The liquid crystal used in the preferred embodiment is HAE614752 manufactured by Jiangsu Hecheng Display Technology Co., Ltd. in China. Other liquid crystals may also be used, such as MLC2136 manufactured by Merck Chemicals in Germany.

[0050] For a twisted nematic liquid crystal cell placed between two polarizers aligned parallel and perpendicular to the respective surface molecular guides, the transmittance is:

[0051]

[0052] Where u = πdΔn / θλ, θ is the liquid crystal twist angle, d is the cell thickness, Δn is the refractive index anisotropy of the liquid crystal material, and λ is the transmission wavelength. For a twisted nematic liquid crystal cell between parallel polarizers (i.e., θ = π / 2), the transmittance is:

[0053]

[0054] Where: x = dΔn / λ. The minimum transmission value of this expression occurs at Where m is a positive integer. The first minimum occurs at x=0.87, which corresponds to Δn=0.2, λ=550 nm and d=2.4 μm.

[0055] Minimum transmission value number (m) Thickness (d; μm) Estimated closing time (ms) 1 2.4 6 2 5.3 29 3 8.1 66 4 10.9 120 5 13.7 190

[0056] A polarization switcher that provides half-wave retardation (i.e., θ = π / 2) should have a liquid crystal layer whose thickness meets the criteria for minimum transmittance using the equation given above. For a liquid crystal layer with Δn = 0.2, λ = 550 nm, a viscosity of 100 mPa, and K = 10 pN, the liquid crystal layer thickness should be 2.4 μm or 5.3 μm, respectively, with a switching time of 6 ms or 29 ms. These switching times are short enough for the polarization switcher to change state (e.g., open or close) without a human-perceptible hysteresis.

[0057] Operation of a fast-switching electro-active lens system

[0058] Figure 5-7 The operation of a fast switching electro-active lens system 500 is shown having a polarization modifier 120, a first electro-active (liquid crystal) lens 125, and a second electro-active (liquid crystal) lens 130 optically connected in series with each other. The first electro-active lens 125 has an alignment layer rubbed in orientation 30, and the second electro-active lens 130 has an alignment layer rubbed in an orthogonal orientation 20. Although Figure 5-7 Gaps between components are shown, but the components may be in contact with each other and bonded together or otherwise integrated to form a single unit, as in Figure 3B The fast-switching electro-active lens system 500 focuses and / or transmits polarized light emitted by a display 520, such as a transparent organic light-emitting diode (OLED) display in an augmented reality system. The fast-switching electro-active lens system 500 and the display 520 are operably coupled to a processor 510 that can control the polarization modifier 120, the first electro-active lens 125, and the second electro-active lens 130 in response to content (video images) shown on the display 520.

[0059] exist Figure 5 In FIG5 , polarization adjuster 120 is in an off state, as are electro-active lenses 125 and 130. Light enters polarization adjuster 120 at polarization orientation 5 and exits at orientation 15 (i.e., it changes from one linear polarization state to an orthogonal linear polarization state). In this example, if polarization adjuster 120 and lens 125 are in an off state and lens 130 is switched to an on state, no optical focusing occurs because the rubbing direction of lens 130 is oriented orthogonal to the polarization state of the light entering lens 130. In other words, if first electro-active lens 125 has no optical power in the off state and second electro-active lens 130 does not act on light in polarization orientation 15, system 500 does not focus the incident light.

[0060] Figure 6Polarization adjuster 120 is shown still in its de-energized state, along with first electro-active lens 125 and second electro-active lens 130 in their energized states. In this configuration, first electro-active lens 125 possesses optical power due to the voltage actuating its liquid crystal material, thereby changing its refractive index profile. Because the polarization of light entering first electro-active lens 125 matches the orientation of its rubbing direction 30, first electro-active lens 125 focuses the incoming light. However, second electro-active lens 130 does not focus light, regardless of its configuration, because its rubbing direction 20 is orthogonal to the light's polarization orientation 15.

[0061] Figure 7 The polarization adjuster 120, the first electro-active lens 125, and the second electro-active lens 130 are shown in an energized state (i.e., a voltage is applied to their liquid crystal layers). In this condition, the polarization adjuster 120 does not transform the polarization state of the incident light; instead, the polarization adjuster 120 transmits the incident light in polarization orientation 5. This means that the light emitted from the polarization adjuster 120 is no longer polarized in the same orientation as the rubbing direction 30 of the first electro-active lens 125, but is now polarized in the same orientation as the rubbing direction 20 of the second electro-active lens 130. Therefore, the second electro-active lens 130 focuses the incident light, but the first electro-active lens 125 does not focus the incident light. If the second electro-active lens 130 has a higher optical power (shorter focal length) than the first electro-active lens 125 in the on state, as shown Figure 7 As shown, this change in polarization state changes the optical power (focal length) of lens system 500, even though the states of first electro-active lens 125 and second electro-active lens 130 are not changed.

[0062] View video with a fast-switching electro-active lens system

[0063] Figure 8 A process is shown by which a rapidly switching electro-active lens system, similar to the systems in Figures 3 and 5-7, can be used to adjust the focus of a virtual image appearing in a video or other dynamic environment presented via an augmented, mixed, or virtual reality system. In the following example, the electro-active lens system includes a polarization-changing component (or polarization converter) that can switch between states A (e.g., π / 2 delay) and B (e.g., 0 delay) within 35 milliseconds, and two focus-changing components (electro-active lenses or focus converters, lenses A and B) that can each switch states within approximately 350 milliseconds. The electro-active lens system is used to show an augmented / virtual reality system that displays a video clip lasting eight seconds. Displaying the video clip involves changing focus every two seconds, with the focus changes occurring within 35 milliseconds and being apparent to the viewer.

[0064] This example video clip begins with a digital image at a distance. At the two-second mark, the simulated distance of the digital image changes from far to far-between, as shown in the following example. Figure 8 As shown in the bottom trace in . At the four-second mark, the simulated distance changes from far middle to near. At the six-second mark, the simulated distance changes from near to middle. At the eight-second mark, the simulated distance changes from middle back to far.

[0065] For the purposes of this example, the simulated distances for far, intermediate far, intermediate, and near are 6 meters, 2 meters, 1 meter, and 0.5 meters, respectively. To view images at these distances, the electro-active lens system provides a net perceivable optical power of zero diopters, half a diopters, one diopters, and two diopters of optical power, respectively, in the same order. In this example, lenses A and B are each switchable between at least a subset of these optical powers, with lens A being switchable between a zero diopter state and a two-diopter state, and lens B being switchable between a zero diopter state, a half-diopter state, and a single-diopter state.

[0066] In this example, when the polarization converter is in state A, lens A is optically present and lens B is not. When the polarization converter is in state B, lens A is optically absent and lens B is present. That is, lens A focuses light that is transmitted when the polarization converter is in state A but not when the polarization converter is in state B, and lens B focuses light that is transmitted when the polarization converter is in state B but not when the polarization converter is in state A. Because the lens is not actuated or because the incident light is of a polarization state that is not focused by the lens, the lens that does not focus light provides zero optical power.

[0067] At the start of the video, the polarization converter is in state A, lens A is at zero diopter because it is off, and lens B is also at zero diopter because it is off and because the polarization converter is in state A. The net perceivable optical power of the electro-active lens system is zero diopter.

[0068] Shortly after the video clip begins, for example, at the one-second mark, a processor coupled to or integrated into the electro-active lens instructs lens B to switch its optical power from zero diopters to one-half diopters. Although lens B changes focus, the viewer cannot see any optical effect occurring in lens B because the polarization converter has rendered lens B optically inactive (the polarization converter is still in state A). Lens B has a full second to complete its change to the new optical power, which is far more time than necessary. At the two-second mark in the video clip, the polarization converter switches its state from state A to state B, thereby rendering lens B optically active, causing the net perceptible optical power of the system to change from zero diopters to one-half diopters in 35 milliseconds.

[0069] Shortly after the two-second mark passes, for example, at the three-second mark, the processor instructs lens A to switch its optical power from zero to two diopters. Although lens A changes focus, the viewer cannot see any optical effect occurring in lens A because the polarization converter has rendered lens A optically inactive (the polarization converter is still in state B, so the net perceived optical power of the electro-active lens system remains at one-half diopters). Lens A has a full second to complete its change to the new optical power, which is much longer than necessary. At the four-second mark in the video clip, the polarization converter again switches states, rendering lens A optically present and lens B optically inactive, causing the system's net perceived optical power to change from one-half diopters to two diopters in 35 milliseconds.

[0070] Shortly after the four-second mark passes, for example, at the five-second mark, the processor instructs Lens B to switch its optical power from half a diopter to one diopter. While in this transitional state, the user cannot see any optical effect occurring because the polarization converter has rendered Lens B optically inactive. Lens B has a full second to complete its change to the new optical power, which is far more time than necessary. At the six-second mark in the video clip, the polarization converter switches state, causing the system's net perceived optical power to change from two diopters to one diopter in 35 milliseconds.

[0071] Shortly after the six-second mark has passed, for example, at the seven-second mark, lens A is instructed to switch its optical power from one diopter to zero diopter. Although lens A changes focus, the viewer cannot see any optical effect occurring in lens A because the polarization converter has rendered lens A optically inactive (the polarization converter is still in state B). Lens A has a full second to complete its change to the new optical power, which is much longer than necessary. At the eight-second mark in the video clip, the polarization converter again switches states, rendering lens A optically present and lens B optically absent (non-existent), resulting in the system's net perceived optical power changing from two diopters to zero diopters in 35 milliseconds.

[0072] The sequence may be modified and repeated as needed, dependent upon and coordinated by signals from a controller or processor presenting the digital image.

[0073] Although the lens may take hundreds of milliseconds to change focus, the viewer observes each focus change occurring within 35 milliseconds.

[0074] The video output can be prepared in advance and can be programmed / controlled to coordinate with the electro-active lens assembly to reduce the viewer's perception of the focus switching time. However, in some cases, the video image may not be prepared in advance and cannot be used to control the switching in this pre-programmed manner. Instead, the electro-active lens operates in an on-demand switching mode controlled by the viewer using a switch or other command device. In these cases, a similar strategy can be employed, where the polarization converter's change of state from one state to another can be delayed until the focus change time period has completed, so that the user sees a 35 millisecond optical switching period and a 350 millisecond lag between the switch command and execution, which is more desirable than having the user experience a 350 millisecond focus change duration.

[0075] In another embodiment, a single electro-active lens can be used with a polarization rotator. Using two tunable lenses allows for a nearly infinite combination of fast switching configurations from one optical power to another, such as from one diopter to two diopters to one-half diopters to one diopter to one-half diopters, etc., while using a single lens allows for fast switching between zero optical power to another optical power, then back to zero diopters, then to another optical power, then to zero diopters, etc.

[0076] Although the system works when randomly polarized light enters the system, such as unpolarized emission from a non-polarized OLED display, the system works best with polarized light. Unpolarized or randomly polarized light can be polarized using a polarizer filter located at the point of light entry into the system, or by using a display technology that emits polarized light, such as an LED display or a polarized OLED display.

[0077] Conclusion

[0078] 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, a person skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application or applications for which the invention is taught. A person skilled in the art will recognize or be able to ascertain many equivalents to the specific inventive embodiments described herein using no more than routine experimentation. Therefore, it should be understood that the foregoing embodiments are given by way of example only, and that within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced in a manner other 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 (provided such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent) is included within the inventive scope of the present disclosure.

[0079] The above embodiments can be implemented in any of a variety of ways. For example, the design and development of embodiments of the technology disclosed herein can 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 across multiple computers).

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 multiple items are separated 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. Generally, the term "or" used herein should only be interpreted as indicating an exclusive alternative (i.e., "one or the other, but not both") before an exclusive term such as "any one," "one," "only one," or "exactly one." "Substantially consisting of..." when used in the claims, should have the ordinary meaning as used in the field of patent law.

[0085] 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.

[0086] 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.

[0087] In summary, the present invention includes but is not limited to the following:

[0088] 1. An electro-active lens system comprising:

[0089] a polarization converter switchable between a first state and a second state, wherein in the first state the polarization converter switches the polarization of light between the first polarization state and the second polarization state, and in the second state the polarization converter transmits light in the first polarization state;

[0090] a first electro-active lens in optical communication with the polarization switcher and switchable between a first focus state in which the first electro-active lens focuses light in the first polarization state and transmits light in the second polarization state, and a first transmissive state in which the first electro-active lens transmits light in both the first and second polarization states; and

[0091] a second electro-active lens in optical communication with the polarization switcher and the first electro-active lens and switchable between a second focus state in which the second electro-active lens transmits light in the first polarization state and focuses light in the second polarization state, and a second transmissive state in which the second electro-active lens transmits light in both the first and second polarization states.

[0092] 2. An electro-active lens system according to claim 1, wherein the polarization switch comprises a liquid crystal wave plate.

[0093] 3. The electro-active lens system of claim 1 , wherein the polarization switch has a delay of π / 2 in the first state and a delay of 0 in the second state.

[0094] 4. An electro-active lens system according to claim 1, wherein the polarization switcher is configured to switch between the first state and the second state (i) faster than the first electro-active lens is configured to switch between the first focused state and the first unfocused state, and (ii) faster than the second electro-active lens is configured to switch between the second focused state and the second unfocused state.

[0095] 5. An electro-active lens system according to claim 4, wherein the polarization switcher is configured to switch between the first state and the second state within 100 milliseconds.

[0096] 6. An electro-active lens system according to claim 5, wherein the first electro-active lens is configured to switch between the first focused state and the first unfocused state in more than 100 milliseconds, and the second electro-active lens is configured to switch between the second focused state and the second unfocused state in more than 100 milliseconds.

[0097] 7. An electro-active lens system according to claim 5, wherein the polarization switcher is configured to switch between the first state and the second state within 30 milliseconds.

[0098] 8. The electro-active lens system of item 1, wherein the polarization switcher and the first electro-active lens share a first common substrate, and the first electro-active lens and the second electro-active lens share a second common substrate.

[0099] 9. The electro-active lens system of claim 1 , wherein the first polarization state is a first linear polarization state and the second polarization state is a second linear polarization state orthogonal to the first linear polarization state.

[0100] 10. A method of focusing light using an electro-active lens system, the electro-active lens system comprising:

[0101] a polarization converter switchable between a first state and a second state, wherein in the first state the polarization converter switches the polarization of light between the first polarization state and the second polarization state, and in the second state the polarization converter transmits light in the first polarization state;

[0102] a first electro-active lens in optical communication with the polarization switcher and switchable between a first focus state in which the first electro-active lens focuses light in the first polarization state and transmits light in the second polarization state, and a first transmissive state in which the first electro-active lens transmits light in both the first and second polarization states; and

[0103] a second electro-active lens in optical communication with the polarization switcher and the first electro-active lens and switchable between a second focus state and a second transmissive state, wherein in the second focus state the second electro-active lens transmits light in the first polarization state and focuses light in the second polarization state, and in the second transmissive state the second electro-active lens transmits light in both the first polarization state and the second polarization state, the method comprising:

[0104] setting the polarization switch to one of the first state or the second state;

[0105] placing the first electro-active lens in one of the first focused state or a first non-focused state;

[0106] placing the second electro-active lens in one of the second focused state or the second non-focused state; and

[0107] The light is sent through the polarization switcher, the first electro-active lens, and the second electro-active lens.

[0108] 11. The method of clause 10, wherein the polarization switcher is in the first state, the first electro-active lens is in the first focused state, and the second electro-active lens is in the second non-focused state, and further comprising:

[0109] switching the second electro-active lens from the second non-focusing state to the second focused state while transmitting light in the first polarization state through the polarization switcher, focusing the light with the first electro-active lens, and transmitting the light through the second electro-active lens without focusing the light by the second electro-active lens;

[0110] After the second electro-active lens has been switched from the second non-focusing state to the second focused state, the polarization switcher is switched from the first state to the second state, thereby causing the second electro-active lens to focus the light and causing the first electro-active lens to transmit the light without focusing the light.

[0111] 12. A method according to item 11, wherein the second electro-active lens is switched from the second non-focusing state to the second focused state and the polarization switch is switched from the first state to the second state in response to a desired change in the position of the virtual image.

[0112] 13. A method according to claim 11, wherein switching the second electro-active lens from the second non-focusing state to the second focused state requires at least 100 milliseconds, and switching the polarization switcher from the first state to the second state requires less than 100 milliseconds.

[0113] 14. The method of item 10, wherein the first polarization state is a first linear polarization state, and the second polarization state is a second linear polarization state orthogonal to the first linear polarization state.

[0114] 15. An electro-active lens system comprising:

[0115] Liquid crystal waveplates that can switch between zero-wave delay and half-wave delay in 35 milliseconds;

[0116] a first liquid crystal lens in optical communication with the liquid crystal wave plate and switchable between a first state and a second state, wherein in the first state, the first liquid crystal lens focuses light in a first linear polarization state onto a first focal plane, and in the second state, the first liquid crystal lens focuses light in the first linear polarization state onto a second focal plane; and

[0117] a second liquid crystal lens, which is in optical communication with the liquid crystal wave plate and the first liquid crystal lens and can be switched between a first state and a second state, wherein in the first state, the second liquid crystal lens focuses light in a second linear polarization state orthogonal to the first linear polarization state onto a third focal plane, and in the second state, the second liquid crystal lens focuses light in the second linear polarization state onto a fourth focal plane.

[0118] 16. The electro-active lens system of item 15, wherein the liquid crystal wave plate and the first liquid crystal lens share a first common substrate, and the first liquid crystal lens and the second liquid crystal lens share a second common substrate.

[0119] 17. The electro-active lens system of item 15, wherein the first liquid crystal lens is configured to transmit light in the second linear polarization state, and the second liquid crystal lens is configured to transmit light in the first linear polarization state.

[0120] 18. The electro-active lens system of claim 15, wherein the first liquid crystal lens is configured to switch between the first state and the second state in more than 35 milliseconds.

[0121] 19. The electro-active lens system of clause 15, further comprising:

[0122] A display is in optical communication with the liquid crystal wave plate and is configured to emit light in the first linear polarization state.

[0123] 20. The electro-active lens system of clause 15, further comprising:

[0124] A processor is operably coupled to the liquid crystal wave plate, the first liquid crystal lens, the second liquid crystal lens, and the display and is configured to control delays of the liquid crystal wave plate, the first liquid crystal lens, the second liquid crystal lens, and the display.

Claims

1. An electro-active lens system comprising: a variable retarder having a first characteristic axis and a second characteristic axis orthogonal to the first characteristic axis and switchable between a first delay and a second delay; a first electro-active lens arranged to receive light from the variable retarder and configured to focus light polarized along the first characteristic axis and transmit light polarized along the second characteristic axis without focusing light polarized along the second characteristic axis at a first variable optical power; and a second electro-active lens arranged to receive light from the variable retarder via the first electro-active lens and configured to transmit light polarized along the first characteristic axis without focusing the light polarized along the first characteristic axis and to focus the light polarized along the second characteristic axis with a second variable optical power.

2. The electro-active lens system of claim 1 , wherein the variable retarder is configured to switch between the first delay and the second delay faster than the first electro-active lens is configured to change the first variable optical power or faster than the second electro-active lens is configured to change the second variable optical power.

3. The electro-active lens system of claim 1 , wherein the variable delay is configured to switch between the first delay and the second delay in no more than 35 milliseconds.

4. The electro-active lens system of claim 1, wherein the first retardation is 0 and the second retardation is π / 2.

5. The electro-active lens system of claim 1 , wherein the first electro-active lens is configured to change the first variable optical power when the variable retarder is switched to one of the first delay or the second delay and the second electro-active lens is configured to change the second variable optical power when the variable retarder is switched to the other of the first delay or the second delay.

6. The electro-active lens system of claim 1 , wherein the second electro-active lens is switchable between a first state in which the first electro-active lens focuses light polarized along the second characteristic axis with a first optical power, and a second state in which the second electro-active lens focuses light polarized along the second characteristic axis with a second optical power different from the first optical power.

7. The electro-active lens system of claim 1 , wherein the variable retarder is a first variable retarder, and the electro-active lens system further comprises: A second variable retarder is disposed between the first electro-active lens and the second electro-active lens and is configured to convert light polarized along the first characteristic axis to light polarized along the second characteristic axis.

8. The electro-active lens system of claim 1 , wherein the variable retarder and the first electro-active lens share a first substrate, and the first electro-active lens and the second electro-active lens share a second substrate.

9. The electro-active lens system of claim 1 , further comprising: A display is arranged to emit light polarized along one of the first characteristic axis or the second characteristic axis.

10. The electro-active lens system of claim 1 , further comprising: A processor is configured to switch the variable retarder between the first delay and the second delay to control the first variable optical power of the first electro-active lens and to control the second variable optical power of the second electro-active lens.

11. An electro-active lens system comprising: a switchable wave plate switchably having a first characteristic axis and a second characteristic axis orthogonal to the first characteristic axis; a first liquid crystal lens arranged to receive light from the switchable waveplate and having a first alignment layer aligned with the first characteristic axis; and A second liquid crystal lens is arranged to receive light from the switchable wave plate via the first liquid crystal lens and has a second alignment layer aligned with the second characteristic axis.

12. The electro-active lens system of claim 11, wherein the switchable wave plate comprises a liquid crystal layer having a thickness selected to provide a half-wave retardation.

13. A method of focusing light using an electro-active lens system, the electro-active lens comprising a variable retarder, a first electro-active lens, and a second electro-active lens, the first electro-active lens providing a first variable optical power to light in a first polarization state and not providing the first variable optical power to light in a second polarization state; the second electro-active lens providing a second variable optical power to light in the second polarization state and not providing the second variable optical power to light in the first polarization state, the method comprising: displaying video via the electro-active lens system; and While displaying the video, the focus of the electro-active lens system is changed by changing the delay of the variable retarder without changing the first variable optical power or the second variable optical power.

14. The method of claim 13, wherein displaying the video comprises emitting light from a display polarized in one of the first polarization state or the second polarization state.

15. The method of claim 13, wherein displaying the video comprises polarizing light in one of the first polarization state or the second polarization state.

16. The method of claim 13, wherein changing the focus of the electro-active lens system is preprogrammed to occur in coordination with changes in the analog distance to the digital image of the video.

17. The method of claim 13, wherein changing the focus of the electro-active lens system occurs in response to a command from a viewer.

18. The method of claim 13, wherein changing the delay of the variable delay comprises switching the delay between 0 and π / 2 in no more than 35 milliseconds.

19. The method according to claim 13, further comprising: The first variable optical power is varied without changing the focus of the electro-active lens system.

20. The method of claim 19, wherein changing the first variable optical power requires at least 100 milliseconds.

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