Fast electroactive lens switching system and method

Abstract

Conventional liquid crystal lenses turn on and off very slowly such that one can perceive the lens gradually changing from a high optical power to a low optical power. This makes conventional liquid crystal lenses unsuitable for rapidly focusing virtual images in augmented, mixed, or virtual reality systems. In contrast, a fast-switching electroactive lens system of the present invention can switch very quickly (e.g., in 35 milliseconds or less) such that one perceives an instantaneous change in the optical power of the system. The system achieves this fast switching by using an electroactive waveplate in series with a slower liquid crystal lens. The waveplate can quickly switch between emitting vertically or horizontally polarized light. Each lens focuses vertically or horizontally polarized light and transmits orthogonally polarized light. By switching between polarization states, the waveplate effectively opens one lens and closes the other lens much faster than either lens can switch on its own.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority of U.S. Application No. 62 / 954,743, filed on December 30, 2019, which is hereby incorporated by reference in its entirety. Background Art

[0003] Electroactive lenses can be used to adjust the focus of the human eye onto digital images presented in an augmented or virtual reality display, which are located at a fixed virtual position relative to the eye, but simulate different distances. Typical electroactive lenses have low mass and volume and consume little energy, but do not switch optical power quickly. A typical electroactive lens that is thirty to forty millimeters wide takes hundreds of milliseconds to switch from one optical power to another. This delay can be discerned by the user and degrades the quality of the visual experience. Summary of the Invention

[0004] An electroactive lens system of the present invention can switch from one optical power to another in tens of milliseconds or faster, rather than hundreds of milliseconds. This is achieved using a pair of electroactive lens elements (also referred to as electroactive 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 light between those orthogonal polarization states in tens of milliseconds. For example, a first electroactive lens element can be configured to focus horizontally polarized light but not vertically polarized light, and a second electroactive lens element can be configured to focus vertically polarized light but not horizontally polarized light. Even if the electroactive lens elements open and close slowly, e.g., over hundreds of milliseconds, the polarization modulator can switch light between the horizontal and vertical polarization states in tens of milliseconds. If the first electroactive lens element and the second electroactive lens element have different optical powers, the polarization modulator can effectively change the optical power of the lens in tens of milliseconds by quickly switching light between the horizontal and vertical polarization states.

[0005] Although the optical power should be switched within a few tens of milliseconds or less, the time between switching events is rarely short. In practice, the time between switching events can be seconds or longer. The difference between the time required to switch an electroactive lens and the time between switching events can be exploited to increase the switching speed of an apparatus having a fast polarization adjuster (also referred to as a polarization beam rotator or variable retarder) and one or more slower focus-changing devices (electroactive or liquid crystal lens elements). By combining a fast polarization-changing component with one or more slower focus-changing components (e.g., a first electroactive lens element and a second electroactive lens element), the polarization-changing component allows 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 optically present, and vice versa. Since the polarization-changing component can rapidly switch the polarization of incident light from one polarization orientation to another, the system can rapidly switch from one focus-changing component to another without moving parts. In a fast-switching electroactive lens system having only a single focus-changing element, the system can rapidly 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 electroactive lens system.

[0006] An electroactive lens system according to the present invention can include a polarization beam rotator, a first electroactive lens optically communicating with the polarization beam rotator, and a second electroactive lens optically communicating with the polarization switcher and the first electroactive lens. The polarization beam rotator can be switched between a first state and a second state. In the first state, the polarization beam rotator switches the polarization of light between a first polarization state and a second polarization state (e.g., orthogonal linear polarization states). In the second state, the polarization beam rotator transmits light in the first polarization state. The first electroactive lens can be switched between a first focusing state and a first transmission state. In the first focusing state, the first electroactive lens focuses light in the first polarization state and transmits light in the second polarization state. In the first transmission state, the first electroactive lens transmits light in the first polarization state and the second polarization state. Also, the second electroactive lens can be switched between a second focusing state and a second transmission state. In the second focusing state, the second electroactive lens transmits light in the first polarization state and focuses light in the second polarization state. In the second transmission state, the second electroactive lens transmits light in the first polarization state and the second polarization state.

[0007] The polarization switch may include a liquid crystal wave plate and may have a retardation of π / 2 in a first state and a retardation of 0 in a second state. The polarization switch may be configured to switch between the first state and the second state (i) faster than the first electroactive lens is configured to switch between a first focused state and a first non-focused state, and (ii) faster than the second electroactive lens is configured to switch between a second focused state and a second non-focused state. For example, the polarization switch may switch between the first state and the second state within 100 milliseconds, 50 milliseconds, 35 milliseconds, 30 milliseconds, 25 milliseconds, 20 milliseconds, 15 milliseconds, 10 milliseconds, 5 milliseconds or faster. Similarly, the first electroactive lens and the second electroactive lens may each be configured to switch between their respective focused and non-focused states in more than 100 milliseconds.

[0008] The polarization switch and the electroactive lens may be integrated, e.g., without an air gap between the components. For example, the polarization switch and the first electroactive lens may share a first common substrate. Similarly, the first electroactive lens and the second electroactive lens may share a second common substrate.

[0009] This electroactive lens system may be used or operated by: setting the polarization switch to the first state or the second state; setting the first electroactive lens to the first focused state or the first non-focused state; setting the second electroactive lens to the second focused state or the second non-focused state; and sending light through the polarization switch, the first electroactive lens, and the second electroactive lens. If the polarization switch is in the first state, the first electroactive lens is in the first focused state, and the second electroactive lens is in the second non-focused state, the second electroactive lens may switch from the second non-focused state to the second focused state while the system transmits light in a first polarization state through the polarization switch, focuses the light with the first electroactive lens, and transmits the light through the second electroactive lens without focusing the light with the second electroactive lens. After the second electroactive lens switches from the second non-focused state to the second focused state, the polarization switch may be switched from the first state to the second state, thereby causing the second electroactive lens to focus the light and causing the first electroactive lens to transmit the light without focusing the light. The second electroactive lens may be switched from the second non-focused state to the second focused state and the polarization switch may be switched from the first state to the second state in response to a desired change in the position of the virtual image. Switching the second electroactive lens from the second non-focused state to the second focused state may take at least 100 milliseconds, and switching the polarization switch from the first state to the second state may take less than 100 milliseconds.

[0010] Another electroactive lens system includes a liquid crystal waveplate optically in series with a first liquid crystal lens and a second liquid crystal lens. The liquid crystal waveplate can switch between a zero wave retardation and a half-wave retardation in 35 milliseconds. The first liquid crystal lens can switch between a first state and a second state. In the first state, the first liquid crystal lens focuses light in a first linear polarization state onto a first focal plane. In the second state, the first liquid crystal lens focuses light in the first linear polarization state onto a second focal plane. The second liquid crystal lens can switch between a first state and a second state. 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. In the second state, the second liquid crystal lens focuses light in the second linear polarization state onto a fourth focal plane.

[0011] The liquid crystal waveplate and the first liquid crystal lens can share a first common substrate, and the first liquid crystal lens and the second liquid crystal lens can share a second common substrate. The first liquid crystal lens and the second liquid crystal lens can transmit light in the second linear polarization state and the first linear polarization state, respectively. The first liquid crystal lens can take more than 35 milliseconds (e.g., 100 milliseconds or more) to switch between the first state and the second state.

[0012] This electroactive lens system can further include a display optically communicating with the liquid crystal waveplate and configured to emit light in the first linear polarization state. And, the electroactive lens system can include a processor operatively coupled to the liquid crystal waveplate, the first liquid crystal lens, the second liquid crystal lens, and the display, and configured to control the retardations of the liquid crystal waveplate, the first liquid crystal lens, the second liquid crystal lens, and the display.

[0013] All combinations of the foregoing concepts and additional concepts discussed in more detail below (provided that these 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 incorporated-by-reference disclosure should be given the meaning that most closely matches the particular concepts disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Those skilled in the art will understand 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 to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to assist in understanding different features. In the drawings, like reference numerals generally refer to like features (e.g., functionally similar and / or structurally similar elements).

[0015] Figure 1A-1C A marker indicating linearly polarized light.

[0016] Figure 2A-2C A marker indicating the liquid crystal alignment (rubbing) direction.

[0017] Figure 3A Shows an exploded view of an exemplary fast-switching electro-active lens system having a fast polarization converter followed by a pair of slower electro-active lenses.

[0018] Figure 3B Shows an integrated fast-switching electro-active lens system.

[0019] Figure 4A Shows a cross-sectional profile view of a fast polarization orientation regulator (variable retarder) in the off state.

[0020] Figure 4B Shows the Figure 4A cross-sectional profile view of a fast polarization orientation regulator (variable retarder) in the on state.

[0021] Figure 5 Shows a fast-switching lens system having a fast polarization converter followed by a pair of slower electro-active lenses, both in the off state (not focusing light).

[0022] Figure 6 Shows Figure 5 a fast-switching lens system in which the fast polarization converter is off (changing the polarization state) and the first electro-active lens is on (focusing light).

[0023] Figure 7 Shows Figure 5 a fast-switching lens system in which the fast polarization converter is on (not changing the polarization state) and the second electro-active lens is on (focusing light).

[0024] Figure 8 Shows the process of actuating a fast-switching lens system in an augmented or virtual reality system, the fast-switching lens system having a fast polarization converter followed by a pair of slower electro-active lenses. Detailed Description

[0025] A fast-switching electroactive lens system can change the focus of linearly polarized light from an object such as a display in an augmented reality headset within 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 principal axes that are orthogonal to each other and orthogonal to the optical axis of the lens. Each lens focuses light polarized along one principal axis (the focusing principal axis) and transmits light polarized along the other principal axis (the transmission principal axis). The amount of focusing, i.e., the optical power, along the focusing principal axis of the lens depends in particular on the liquid crystal thickness and the applied voltage and can be tuned continuously (e.g., between a -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 diopter increments). Each lens can provide zero optical power when turned off (when no voltage is applied) or can provide non-zero optical power when turned off. Other ranges and values of optical power are also possible.

[0026] The lenses are aligned such that their optical axes coincide, but their principal axes are rotated 90° relative to each other - the focusing principal axis of the first lens is parallel to the transmission principal axis of the second lens, and the transmission principal axis of the first lens is parallel to the focusing principal axis of the second lens. The lens optical axes are aligned with the optical axis of the waveplate, and the principal axes of the waveplate are aligned with the principal axes of the lenses. In other words, when viewed along the surface normal (the optical axis of the fast-switching electroactive lens system) of the waveplate and the lenses, the waveplate and the lenses have coinciding surface normals and aligned principal axes.

[0027] Because the lenses are aligned with 90°-rotated focusing and transmission principal axes, when the system is illuminated with light linearly polarized along one of the system principal axes, one lens focuses the light and the other lens transmits the light. The operation of switching the lenses transforms the polarization state of the incident light to an orthogonal linear polarization state (e.g., from horizontal to vertical or from +45° to -45°). The waveplate changes state much faster than the lenses, such that the user-observable transition from one optical power to another is much faster than if a single lens provided all the optical adjustment. And if the transitions occur infrequently (e.g., at intervals greater than the lens switching time), then one lens can be switched between optical power levels while the other lens focuses the light such that it is ready for the next transition.

[0028] Polarization state and liquid crystal alignment direction

[0029] 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 linear polarization as if it "enters and exits the plane of the figure".Figure 1B The symbol 10 in [description] indicates that the direction of linear polarization is orthogonal to the direction indicated by symbol 5. In this case, the direction of linear polarization is "left and right in the plane of the figure". Figure 1C The symbol 15 in [description] indicates that the direction of linear polarization is also orthogonal to the direction indicated by symbol 5. The direction of linear polarization indicated by symbol 15 is "up and down in the plane of the figure".

[0030] Figure 2A , 2B Figures 2A, 2B, and 2C show symbols used in the present disclosure to describe the orientation of the rubbing or alignment direction of the alignment layer used in a liquid crystal focusing transducer (electroactive lens). Figure 2A The symbol 20 in [description] indicates the direction of the rubbing direction as if it "enters and exits the plane of the figure". Figure 2B The symbol 25 in [description] indicates that the direction of the rubbing direction is orthogonal to the direction indicated by symbol 20, and in this case, the direction of the rubbing direction is "left and right in the plane of the figure". Figure 2C The symbol 30 in [description] indicates that the rubbing direction is orthogonal to the directions indicated by symbols 20 and 25, where the rubbing direction is "up and down in the plane of the figure". Each liquid crystal lens typically has two alignment layers - one on each side of the liquid crystal material - whose rubbing directions can be parallel, anti-parallel, or orthogonal to each other. In some cases, only one alignment layer may be used to reduce costs. Using two alignment layers increases both the switching speed and the field of view width.

[0031] Figure 1A-1C The symbols shown in Figures 2A - 2C indicate relative directions. If different schematics are from different perspectives, different symbols can be used to indicate the same polarization state in those schematics. Similarly, if different schematics are from different perspectives, the same symbol can be used to indicate different polarization states in those schematics. For example, in a side view or profile view of an optical component, symbol 5 can indicate a horizontal polarization state, and 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, symbol 10 can indicate a horizontal polarization state, and symbol 15 can indicate a vertical polarization state.

[0032] Fast Electroactive Lens Switching System

[0033] Figure 3AShows an exploded view of a fast-switching lens system 300 that includes a polarization orientation transducer (also known as a polarization rotator, polarization modulator, or variable retarder) 40 that is optically communicative with a first electroactive lens 50 and a second electroactive lens 60. The polarization orientation transducer 40, the first electroactive lens 50, and the second electroactive lens 60 are optically in series or stacked together. 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 electroactive lens 50 is oriented orthogonally to the alignment layer of the second electroactive lens 60. In this case, the first electroactive lens 50 has a horizontally oriented liquid crystal rubbing direction 25, and the second electroactive lens 60 has a vertically oriented liquid crystal rubbing direction 30. Other rubbing directions are possible (e.g., ±45° rubbing directions), typically used when less than 100% focusing is desired (in other words, only a portion of the light is focused while another portion of the light that passes through is not focused).

[0034] Although Figure 3A the apparatus 300 shown in Figure 3A is a preferred embodiment, additional polarization switches can be added to add functional control options. For example,

[0035] the apparatus 300 in Figure 3A can rapidly switch between the optical powers of the lenses 50 and 60. If an additional polarization switch is positioned between the lens 50 and the lens 60, actuating the two polarization switches makes it possible to change the polarization state of the light propagating through the system such that the two lenses 50, 60 focus the light. More specifically, the first polarization switch 40 can switch the light from a second polarization state 10 to a first polarization state 15, and a second polarization switch (not shown) can switch the light from the first polarization state 15 to the second polarization state 10. Alternatively, the two polarization switches can be actuated such that neither of the two lenses 50, 60 focuses the light, even if one or both of the 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] The light 45 exiting the polarization adjuster 40 enters the first electro-active lens 50. If the light 45 is in a first polarization state (e.g., vertically polarized) and the first electro-active lens 50 is in a first state (e.g., open), then the first electro-active lens focuses the light 45 onto a first focal plane. If the light 45 is in the first polarization state and the first electro-active lens 50 is in a second state (e.g., closed), then the first electro-active lens 50 focuses the light onto a second focal plane. And if the light 45 is in a second polarization state (e.g., horizontally polarized), then it passes through the first electro-active lens 50 without being focused by the first electro-active lens 50.

[0037] The light 55 exiting the first electro-active lens 50 enters the second electro-active lens 60, which, like the first electro-active lens 50, can switch between two states (e.g., open and closed states). However, unlike the first electro-active lens 50, the second electro-active lens 60 only acts on light that is in the second polarization state (e.g., horizontally polarized). When the second electro-active lens 60 is in the first state, it focuses the light in the second polarization state onto a third focal plane. And when the second electro-active lens 60 is in the second state, it focuses the light in the second polarization state onto a fourth focal plane. The light 55 in the first polarization state (e.g., vertically polarized) passes through the second electro-active lens 60 without being focused by the second electro-active lens 60. The light 65 exits the second electro-active lens 60 and the system 300.

[0038] If the first electro-active lens 50 and the second electro-active lens 60 provide different optical power levels, then the lens system 300 can be switched between a series 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 diopter (correspondingly, the first / open and second / closed states), and the second electro-active lens 50 can be switched between optical power levels of 0.5 diopters and 1.5 diopters (correspondingly, the first / open and second / closed states), then 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 on a near plane, a near intermediate plane, an intermediate plane, a far intermediate plane, and / or a far plane.

[0039] The fast switching speed of the polarization adjuster 40 makes it possible for the lens system 300 to quickly switch (e.g., within 30 ms or less) between these optical power levels, even if the first electroactive lens 50 and the second electroactive lens 60 can switch slowly (e.g., within 100 ms or more). For example, when the first electroactive lens 50 is on and the polarization adjuster 40 is off, the second electroactive lens 60 can transition from one optical power to another without affecting the light propagating through the lens system 300. Once the second lens 60 has completed its transition and is ready and at the desired optical power, the polarization adjuster 40 switches states, causing the second electroactive lens 60 to focus the light while the first electroactive lens 50 no longer focuses the light, even if the first electroactive lens 50 remains on.

[0040] Figure 3A The components are shown in an exploded perspective view with gaps between them. Although the lens system can operate with gaps as Figure 3A shown, the lens system can also be fabricated from components that are adjacent to and bonded or integrated with each other to eliminate reflections at the interfaces. For example, the first electroactive lens 50 can share a first substrate with the polarization orientation transducer 40 and a second substrate with the second electroactive lens 60.

[0041] Figure 3B An integrated fast-switching electroactive lens system 350 is shown. In this system 350, substrates 41 and 43 together with liquid crystal layer 42 form the polarization adjuster 40. Substrate 43 and 46 together with liquid crystal layer 44 form the first lens 50. And, substrate 46 and 48 together with liquid crystal layer 47 form the second lens 60. Substrates 43 and 46 are shared by multiple components and are thus coated with separate alignment layers and independently actuated electrodes (not shown) on each side.

[0042] Fast polarization adjuster (variable retarder)

[0043] Figure 4A and 4B A side view showing a cross section of the polarization adjuster 40. Figure 4A shows the adjuster 40 in an unpowered or off (first) state, while Figure 4B shows the adjuster 40 in a powered or on (second) state.

[0044] The polarization adjuster 40 is composed of a first substrate 72 and a second substrate 80, where 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, cured along the direction of the desired alignment orientation, and then rubbed with a felt cloth.( Figure 2A-2C Shows the possible rubbing directions of the alignment layer.) 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 can be made of the same material as that used to make the first electrode 75.

[0045] Figure 4A Shows the difference between the electrodes 75 and 85: When the polarization adjuster 40 is off, the alignment layer on the first electrode 75 is configured to orient adjacent liquid crystal molecules in the direction indicated by the symbol 25, while the alignment layer on the second electrode 85 is configured to orient adjacent liquid crystal molecules in the direction indicated by the symbol 20. Due to this configuration, correspondingly, the liquid crystal molecules are aligned with the first electrode 75 in the orientation / direction 25, with the second electrode 85 in the orientation / direction 20, and in the orientation / direction at the intermediate position between the orientation 25 and the orientation 20 in the middle of the liquid crystal layer, and the closer the liquid crystal is to the first electrode 75 and the second electrode 85, the more the liquid crystal molecules gradually twist closer to the orientations 25 and 20. This twisting configuration is indicated by Figure 4A the three symbols 100 in. This twisting of the liquid crystal molecules adjusts or changes the polarization direction of the light 105 from the polarization orientation 10 when the light enters the polarization adjuster 40 to the polarization orientation 5 when the light leaves the polarization adjuster 40.

[0046] Figure 4B Shows the polarization adjuster 40, where a voltage supplier 110 applies an electric field potential to the first electrode 75, while an opposite electric field potential is applied to the 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 the orientation 100 to the orientation 115, as shown in Figure 4B . In this state, the polarization orientation 10 of the light 105 entering the polarization adjuster is the same as the polarization orientation 10 of the light 105 when it leaves the polarization adjuster. In other words, applying a voltage to the electrodes 75 and 85 changes the retardation of the polarization adjuster from π / 2 to 0. The polarization adjuster 40 does not change the propagation direction of the light.

[0047] Other configurations of the polarization adjuster are also possible. For example, the alignment layer can have parallel or anti-parallel rubbing directions, rather than as shown in Figure 4A and 4BCrossed or orthogonal rubbing directions. In parallel or antiparallel rubbing directions, the polarization adjuster does not change the polarization state of the incident light when it is turned off (i.e., when no voltage is applied across the liquid crystal by the electrodes); its nominal retardation is 0. Alternatively, the polarization adjuster changes the polarization state of the incident light when it is turned on (i.e., when a voltage is applied across the liquid crystal by the electrodes), for example, by changing horizontally polarized light or vertically polarized light to achieve a retardation change of π / 2.

[0048] The design parameters of the polarization adjuster, 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 set to achieve a fast switching speed and high optical efficiency. Several example turn-off times are shown (indicating preferred liquid crystal thicknesses of 2.4 μm or 5.3 μm), however, the turn-on 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 can also be used, such as MLC2136 manufactured by Merck Chemicals in Germany.

[0049] For a twisted nematic liquid crystal cell placed between two polarizers aligned parallel and perpendicular to the respective surface molecular guides, the transmittance is:

[0050]

[0051] 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 transmitted wavelength. For a twisted nematic liquid crystal cell between parallel polarizers (i.e., θ = π / 2), the transmittance is:

[0052]

[0053] where: x = dΔn / λ. The minimum transmittance 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.

[0054] Transmission minimum number (m) Thickness (d; μm) Estimated turn-off time (ms) 1 2.4 6 2 5.3 29 3 8.1 66 4 10.9 120 5 13.7 190

[0055] A polarization switch that provides a half-wave delay (i.e., θ = π / 2) should have a liquid crystal layer, the thickness of which satisfies the criterion of the minimum transmittance using the equation given above. For a liquid crystal layer with Δn = 0.2, λ = 550 nm, viscosity of 100 mPa, and K = 10 pN, the liquid crystal layer thickness should be 2.4 μm or 5.3 μm within switching times of 6 ms or 29 ms, respectively. These switching times are short enough for the polarization switch to change states (e.g., turn on or off) without any perceptible hysteresis.

[0056] Operation of a fast-switching electroactive lens system

[0057] Figures 5-7 Illustrates the operation of a fast-switching electroactive lens system 500 having a polarization adjuster 120, a first electroactive (liquid crystal) lens 125, and a second electroactive (liquid crystal) lens 130 optically in series with each other. The first electroactive lens 125 has an alignment layer rubbed in the orientation 30, and the second electroactive lens 130 has an alignment layer rubbed in the orthogonal orientation 20. Although Figures 5-7 gaps between components are shown, the components can be in contact with and bonded to each other or otherwise integrated to form a single unit, just as Figure 3B in the system 350. The fast-switching electroactive 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 electroactive lens system 500 and the display 520 are operatively coupled to a processor 510, which can control the polarization adjuster 120, the first electroactive lens 125, and the second electroactive lens 130 in response to the content (video image) shown on the display 520.

[0058] In Figure 5 the polarization adjuster 120 is in the off state, as are the electroactive lenses 125 and 130. Light enters the polarization adjuster 120 in the polarization orientation 5 and exits in the orientation 15 (i.e., it changes from one linear polarization state to an orthogonal linear polarization state). In this example, if the polarization adjuster 120 and the lens 125 are in the de-energized state and the lens 130 is switched to the energized state, no optical focusing occurs because the orientation of the rubbing direction of the lens 130 is orthogonal to the polarization state of the light entering the lens 130. In other words, if the first electroactive lens 125 has no optical power in the off state and the second electroactive lens 130 does not act on the light in the polarization orientation 15, the system 500 does not focus the incident light.

[0059] Figure 6Shows the polarization modulator 120 still in the power-off state, and the first electro-active lens 125 and the second electro-active lens 130 in the power-on state. In this configuration, the first electro-active lens 125 has optical power due to the voltage that actuates its liquid crystal material to change its refractive index distribution. Since the polarization of the light entering the first electro-active lens 125 matches the orientation of the rubbing direction 30 of the first electro-active lens, the first electro-active lens 125 focuses the incident light. However, the second electro-active lens 130 does not focus the light, regardless of its setting, because its rubbing direction 20 is orthogonal to the polarization orientation 15 of the light.

[0060] Figure 7 Shows the polarization modulator 120, the first electro-active lens 125, and the second electro-active lens 130 in the power-on state (i.e., voltage is applied to their liquid crystal layers). Under this condition, the polarization modulator 120 does not change the polarization state of the incident light; instead, the polarization modulator 120 transmits the incident light in the polarization orientation 5. This means that the light emerging from the polarization modulator 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 open state, as Figure 7 shown, this change in the polarization state changes the optical power (focal length) of the lens system 500, even if the states of the first electro-active lens 125 and the second electro-active lens 130 do not change.

[0061] Viewing video with a fast-switching electro-active lens system

[0062] Figure 8 Shows a process by which the focus of virtual images that appear in a video or other dynamic environment presented via an augmented, mixed, or virtual reality system can be adjusted using a fast-switching electro-active lens system similar to the systems in FIGS. 3 and 5 - 7. In the following example, the electro-active lens system includes a polarization-changing component (or polarization transformer) that can switch between state A (e.g., π / 2 delay) and B (e.g., 0 delay) in 35 milliseconds, and two focus-changing components (electro-active lenses or focus transformers, lenses A and B) that can each switch states in approximately 350 milliseconds. The electro-active lens system is used in an augmented / virtual reality system to show a video clip that lasts for eight seconds. Displaying the video clip involves changing the focus once every two seconds, where the focus change occurs within 35 milliseconds, which is obvious to the viewer.

[0063] This example video clip starts with a digital image at a long distance. At the two - second mark, the simulated distance of the digital image changes from long distance to far - mid, as shown by the bottom trace in Figure 8 . At the four - second mark, the simulated distance changes from far - mid to near. At the six - second mark, the simulated distance changes from near to mid. At the eight - second mark, the simulated distance changes from mid back to long distance.

[0064] For the purposes of this example, the simulated distances of long, far - mid, mid, and near are 6 meters, 2 meters, 1 meter, and 0.5 meters respectively. To view the images at these distances, the electro - active lens system provides net perceivable optical powers of zero diopter, half - diopter, one diopter, and two diopters in the same order. In this example, lenses A and B can each switch between at least one subset of these optical powers, where lens A can switch between the zero - diopter state and the two - diopter state, and lens B can switch between the zero - diopter state, the half - diopter state, and the one - diopter state.

[0065] In this example, when the polarization converter is in state A, lens A is optically present and lens B is not optically present. When the polarization converter is in state B, lens A is not optically present and lens B is present. That is, lens A focuses the light transmitted when the polarization converter is in state A rather than when it is in state B, and lens B focuses the light transmitted when the polarization converter is in state B rather than when it is in state A. Lenses that do not focus light provide an optical power of zero diopter because the lens is not actuated or because the incident light is in a polarization state that is not focused by the lens.

[0066] 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.

[0067] Shortly after the start of the video clip, for example, at the one - second mark, a processor coupled to or integrated in the electro - active lens instructs lens B to switch the optical power from zero diopter to half - diopter. Although lens B changes focus, the viewer cannot see any optical effect occurring in lens B because the polarization converter has made lens B not optically present (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 is required. At the two - second mark in the video clip, the polarization converter switches state from state A to state B, thereby making lens B optically present, and thus changing the net perceivable optical power of the system from zero diopter to half - diopter in 35 milliseconds.

[0068] Shortly after the two - second mark has passed, e.g., at the three - second mark, the processor instructs lens A to switch its optical power from zero to two diopters. While lens A changes its focus, the viewer cannot see any optical effect occurring in lens A because the polarization converter has made lens A optically non - existent (the polarization converter is still in state B, so the net perceivable optical power of the electro - active lens system remains at one - half diopter). Lens A has a full second to complete its change to the new optical power, which is far more than the time required. At the four - second mark in the video clip, the polarization converter switches states again, thus making lens A optically existent while lens B is not optically existent, causing the net perceivable optical power of the system to change from one - half diopter to two diopters in 35 milliseconds.

[0069] Shortly after the four - second mark has passed, e.g., at the five - second mark, the processor instructs lens B to switch its optical power from one - half diopter to one diopter. While in the transition state of the change, the user cannot see any optical effect occurring because the polarization converter has made lens B optically non - existent. Lens B has a full second to complete its change to the new optical power, which is far more than the time required. At the six - second point in the video clip, the polarization converter switches states, causing the net perceivable optical power of the system to change from two diopters to one diopter in 35 milliseconds.

[0070] Shortly after the six - second mark has passed, e.g., at the seven - second point, lens A is instructed to switch its optical power from one diopter to zero diopters. While lens A changes its focus, the viewer cannot see any optical effect occurring in lens A because the polarization converter has made lens A optically non - existent (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 far more than the time required. At the eight - second mark in the video clip, the polarization converter switches states again, thus making lens A optically existent while lens B is optically absent (non - existent), causing the net perceivable optical power of the system to change from two diopters to zero diopters in 35 milliseconds.

[0071] This sequence can be modified and repeated as needed, depending on and coordinated by a signal from a controller or processor that presents a digital image.

[0072] Although the lens may take hundreds of milliseconds to change focus, the viewer observes each change in focus occurring in 35 milliseconds.

[0073] The video output can be pre-prepared and can be programmed / controlled to coordinate with the electroactive lens assembly to reduce the viewer's perception of focus switching time. However, in some cases, the video image may not be pre-prepared and may not be available for controlling the switching in this pre-programmed manner. Instead, the electroactive 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 change of state of the polarization converter from one state to another can be delayed until the focus change time period has been completed, such that the user sees a 35 millisecond optical switching period and a 350 millisecond lag between the switching command and its execution, which is more desirable than having the user experience a 350 millisecond focus change duration.

[0074] In another embodiment, a single electroactive lens can be used with a polarization rotator. Using two adjustable lenses allows for an almost infinite combination of fast switching configurations from one optical power to another, such as from one diopter to two diopters to one-half diopter to one diopter and back to one-half diopter, etc., while using a single lens allows for fast switching between zero optical power and another optical power, then back to zero diopters, then to another optical power, then to zero diopters, etc.

[0075] Although the system works when randomly polarized light enters the system - such as the unpolarized emission from an unpolarized OLED display - the system works best under polarized light. Unpolarized or randomly polarized light can be polarized using a polarizer filter located at the light entry point of the system, or by using a display technology such as an LED display or a polarized OLED display that emits polarized light.

[0076] Conclusion

[0077] Although various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily conceive of many other devices and / or structures for performing the functions and / or obtaining the results and / or one or more of the 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 the actual parameters, dimensions, materials, and / or configurations will depend upon one or more specific applications for which the inventive teachings are used. Those skilled in the art can recognize or be able to determine, with the use of no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. Accordingly, it is to be understood that the foregoing embodiments are presented by way of example only and that the embodiments of the invention may be practiced otherwise than as specifically described and claimed within the scope of the appended claims and their equivalents. The inventive embodiments of the present disclosure relate to each and every separate feature, system, article, material, kit, and / or method described herein. Additionally, 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.

[0078] The above embodiments can be implemented in any of a variety of ways. For example, embodiments of the techniques 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 among multiple computers.

[0079] Moreover, various inventive concepts can be embodied as one or more methods, examples of which have been provided. The acts performed as part of a method can be ordered in any suitable way. Accordingly, embodiments can be constructed that execute the acts in an order different from that illustrated, which can include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0080] It should be understood that all definitions, as defined and used herein, take precedence over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of defined terms.

[0081] As used herein in the specification and claims, the indefinite article "a" shall be understood to mean "at least one" unless expressly stated to the contrary.

[0082] As used herein in the specification and claims, the phrase "and / or" shall be understood to mean "any one or both" of the elements so combined, i.e., the elements exist together in some cases and separately in other cases. Multiple elements listed with "and / or" shall be construed in the same manner, i.e., "one or more" of the elements so combined. Other elements may optionally exist in addition to the elements specifically pointed out by the "and / or" clause, whether related or unrelated to those specifically pointed out. Thus, as a non-limiting example, when used in conjunction with open-ended language (such as "comprising"), a reference to "A and / or B" may in one embodiment refer only to A (optionally including elements other than B); in another embodiment only to B (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); and so on.

[0083] As used herein in this specification and claims, "or" shall be understood to have the same meaning as "and / or" as defined above. By way of example, when separating multiple items in a list, "or" or "and / or" shall be interpreted inclusively, i.e., including at least one, but also including more than one of several elements or a list of elements and optionally additional unlisted items. Only terms with an express contrary indication, such as "only one of... " or "exactly one of... " or when used in the claims "consisting of... " shall refer to including exactly one element of a plurality of elements or a list of elements. Generally, the term "or" as used herein shall only be interpreted to indicate an exclusive alternative (i.e., "one or the other, but not both") before exclusive terms such as "any one", "a", "only one", or "exactly one". "Consisting essentially of... " when used in the claims shall have the ordinary meaning as used in the field of patent law.

[0084] As used herein in the specification and claims, when referring to a list of one or more elements, the phrase "at least one" shall be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, and not excluding any combination of the elements in the list of elements. This definition also allows elements other than those specifically referred to by the phrase "at least one" within the list of elements to optionally be present, whether or not they are related to those 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, it 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, it 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); and so on.

[0085] In the claims as well as in the foregoing specification, all connecting words such as "comprising", "including", "carrying", "having", "containing", "involving", "accommodating", "consisting of", etc. shall be understood to be open, that is, meaning including but not limited to. As set forth in Section 2111.03 of the Patent Examination Procedure Manual of the United States Patent and Trademark Office, only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

Claims

1. An electroactive lens system, comprising: a polarization switch that can switch between a first state and a second state, in the first state, the polarization switch switches the polarization of light between a first polarization state and a second polarization state, and in the second state, the polarization switch transmits light in the first polarization state; a first electroactive lens that is optically communicated with the polarization switch and can switch between a first focusing state and a first non - focusing state, in the first focusing state, the first electroactive lens focuses light in the first polarization state and transmits light in the second polarization state without focusing light in the second polarization state, and in the first non - focusing state, the first electroactive lens transmits light in the first polarization state and the second polarization state without focusing light in the first polarization state or the second polarization state; and a second electroactive lens that is optically communicated with the polarization switch and the first electroactive lens and can switch between a second focusing state and a second non - focusing state, in the second focusing state, the second electroactive lens transmits light in the first polarization state and focuses light in the second polarization state without focusing light in the first polarization state, and in the second non - focusing state, the second electroactive lens transmits light in the first polarization state and the second polarization state without focusing light in the first polarization state or the second polarization state.

2. The electroactive lens system according to claim 1, wherein the polarization switch comprises a liquid crystal wave plate.

3. The electroactive lens system according to claim 1 or 2, wherein the polarization switch has a retardation of π / 2 in the first state and a retardation of 0 in the second state.

4. The electroactive lens system according to any one of the preceding claims, wherein the polarization switch is configured to switch between the first state and the second state (i) faster than the first electroactive lens is configured to switch between the first focusing state and the first non - focusing state, and (ii) faster than the second electroactive lens is configured to switch between the second focusing state and the second non - focusing state.

5. The electroactive lens system according to claim 4, wherein the polarization switch is configured to switch between the first state and the second state within 100 milliseconds.

6. The electroactive lens system according to claim 5, wherein the first electroactive lens is configured to switch between the first focusing state and the first non - focusing state in more than 100 milliseconds, and the second electroactive lens is configured to switch between the second focusing state and the second non - focusing state in more than 100 milliseconds.

7. The electroactive lens system according to claim 5, wherein the polarization switch is configured to switch between the first state and the second state within 30 milliseconds.

8. The electroactive lens system according to any one of the preceding claims, wherein the polarization switch and the first electroactive lens share a first common substrate, and the first electroactive lens and the second electroactive lens share a second common substrate.

9. The electroactive lens system according to any one of the preceding claims, 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.

10. A method of focusing light with an electroactive lens system, the electroactive lens system comprising: A polarization switch that can switch between a first state and a second state. In the first state, the polarization switch switches the polarization of light between a first polarization state and a second polarization state. In the second state, the polarization switch transmits light in the first polarization state. A first electroactive lens that is optically communicated with the polarization switch and can switch between a first focused state and a first non-focused state. In the first focused state, the first electroactive lens focuses light in the first polarization state and transmits light in the second polarization state without focusing light in the second polarization state. In the first non-focused state, the first electroactive lens transmits light in the first polarization state and the second polarization state without focusing light in the first polarization state or the second polarization state. And A second electroactive lens that is optically communicated with the polarization switch and the first electroactive lens and can switch between a second focused state and a second non-focused state. In the second focused state, the second electroactive lens transmits light in the first polarization state and focuses light in the second polarization state without focusing light in the first polarization state. In the second non-focused state, the second electroactive lens transmits light in the first polarization state and the second polarization state without focusing light in the first polarization state or the second polarization state. The method includes: Setting the polarization switch to one of the first state or the second state; Setting the first electroactive lens to one of the first focused state or the first non-focused state; Setting the second electroactive lens to one of the second focused state or the second non-focused state; and Sending the light through the polarization switch, the first electroactive lens, and the second electroactive lens.

11. The method according to claim 10, wherein the polarization switch is in the first state, the first electroactive lens is in the first focused state, and the second electroactive lens is in the second non-focused state, and the method further includes: Switching the second electroactive lens from the second non-focused state to the second focused state while allowing light in the first polarization state to transmit through the polarization switch, focusing the light with the first electroactive lens, and allowing the light to transmit through the second electroactive lens without focusing the light with the second electroactive lens. and After the second electroactive lens has been switched from the second non - focused state to the second focused state, the polarization switcher is switched from the first state to the second state, thereby causing the second electroactive lens to focus the light and causing the first electroactive lens to transmit the light without focusing the light.

12. The method according to claim 11, wherein the second electroactive lens is switched from the second non - focused state to the second focused state and the polarization switcher is switched from the first state to the second state in response to a desired change in the position of the virtual image.

13. The method according to claim 11, wherein switching the second electroactive lens from the second non - focused state to the second focused state takes at least 100 milliseconds and switching the polarization switcher from the first state to the second state takes less than 100 milliseconds.

14. The method according to any one of claims 10 - 13, 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.

15. An electroactive lens system comprising: a liquid - crystal waveplate that can switch between a zero - wave retardation and a half - wave retardation in 35 milliseconds; a first liquid - crystal lens optically communicating with the liquid - crystal waveplate and capable of switching between a first state and a second state, in the first state, the first liquid - crystal lens focuses light in a first linear polarization state onto a first focal plane and does not focus light in a second linear polarization state orthogonal to the first linear polarization state, and in the second state, the first liquid - crystal lens focuses light in the first linear polarization state onto a second focal plane and does not focus light in the second linear polarization state; and a second liquid - crystal lens optically communicating with the liquid - crystal waveplate and the first liquid - crystal lens and capable of switching between a first state and a second state, in the first state, the second liquid - crystal lens focuses light in the second linear polarization state onto a third focal plane and does not focus light in the first linear polarization state, and in the second state, the second liquid - crystal lens focuses light in the second linear polarization state onto a fourth focal plane and does not focus light in the first linear polarization state.

16. The electroactive lens system according to claim 15, wherein the liquid - crystal waveplate 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.

17. The electroactive lens system according to 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.

18. The electroactive lens system according to claim 15, further comprising: a display optically communicating with the liquid - crystal waveplate and configured to emit light in the first linear polarization state.

19. The electroactive lens system according to claim 18, further comprising: A processor, operably coupled to the liquid crystal waveplate, the first liquid crystal lens, the second liquid crystal lens, and the display, and configured to control the liquid crystal waveplate, the first liquid crystal lens, the second liquid crystal lens, and the display.

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