Patent Description:
An electroactive lens can be used to adjust the focus of a person's eye onto a digital image presented in an augmented or virtual reality display at a fixed virtual location from the eye but at various simulated distances. A typical electroactive lens is low in mass and volume and consumes little energy but does not switch optical power quickly. A typical thirty to forty millimeter wide electroactive lens takes a few hundred milliseconds to switch from one optical power to another optical power. This delay is discernable by the user and degrades the quality of the visual experience.

Document <CIT> discloses relevant prior art.

An inventive electroactive lens system can (appear to) switch from one optical power to another in tens of milliseconds, or faster, rather than hundreds of milliseconds. It does this with a pair of electroactive lens elements (also called 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, the first electroactive lens element may be configured to focus horizontally polarized light but not vertically polarized light, and the second electroactive lens element may be configured to focus vertically polarized light but not horizontally polarized light. Even if the electroactive lens elements turn on and off slowly, e.g., in hundreds of milliseconds, the polarization adjuster can switch the light between horizonal and vertical polarization states in tens of milliseconds. If the first and second electroactive lens elements have different optical powers, the polarization adjuster can effectively change the lens's optical power within tens of milliseconds by switching the light between horizonal and vertical polarization states quickly.

Although the optical power should be switched in tens of milliseconds or less, the time between switching events is rarely that brief. In practice, the time between switching events can be several seconds or more. The difference in the time it takes to switch an electroactive lens and the time between switching events can be exploited to increase the switching speed in a device with a fast polarization adjuster (also called a polarization orientation changer 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., first and second electroactive lens elements), 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 components are not optically present, and vice versa. Since the polarization-changing component can switch incident light rapidly from one polarization orientation to the other, the system can rapidly switch from one focus-changing component to the other, with no moving parts. In a fast-changing electroactive lens system with only a single focus-changing element, the system can be rapidly switched from a "lens on" state to a "lens off" state rapidly. There is no limit to the number of focus-changing elements that can be used in a single electroactive lens system.

An inventive electroactive lens system may include a polarization changer, a first electroactive lens in optical communication with the polarization changer, and a second electroactive lens in optical communication with the polarization switcher and the first electroactive lens. The polarization changer is switchable between a first state in which the polarization changer switches a polarization of light between a first and second polarization states (e.g., orthogonal linear polarization states) and a second state in which the polarization changer transmits light in the first polarization state. The first electroactive lens is switchable between a first focusing state in which the first electroactive lens focuses light in the first polarization state and transmits light in the second polarization state and a first transmitting state in which the first electroactive lens transmits light in the first and second polarization states. And the second electroactive lens is switchable between a second focusing state in which the second electroactive lens transmits light in the first polarization state and focuses light in the second polarization state and a second transmitting state in which the second electroactive lens transmits light in the first and second polarization states.

The polarization switcher may comprise a liquid-crystal wave plate and may have a retardance of π/<NUM> in the first state and a retardance of <NUM> in the second state. The polarization switcher can be 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. For instance, the polarization switcher may switch between the first and second states within <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, <NUM> milliseconds, or faster. Similarly, the first and second electroactive lenses may each be configured to switch between their respective focusing and non-focusing states in more than <NUM> milliseconds.

The polarization switcher and electroactive lenses may be integrated together, e.g., with no air gaps between components. For instance, the polarization switcher and first electroactive lens can share a first common substrate. Likewise, the first and second electroactive lenses can share a second common substrate.

This electroactive lens system can be used or operated by setting the polarization switcher to the first or second state; setting the first electroactive lens to the first focusing state or the first non-focusing state; setting the second electroactive lens to the second focusing state or the second non-focusing state; and sending the light through the polarization switcher, the first electroactive lens, and the second electroactive lens. If the polarization switcher is in the first state, the first electroactive lens is in the first focusing state, and the second electroactive lens is in the second non-focusing state, the second electroactive lens can be switched from the second non-focusing state to the second focusing state while the system transmits light in the first polarization state through the polarization switcher, focuses the light with the first electroactive lens, and transmits the light through the second electroactive lens without focusing the light by the second electroactive lens. After the second electroactive lens is switched from the second non-focusing state to the second focusing state, the polarization switcher can 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. Switching the second electroactive lens from the second non-focusing state to the second focusing state and switching the polarization switcher from the first state to the second state may occur in response to a desired change in a position of a virtual image. Switching the second electroactive lens from the second non-focusing state to the second focusing state may take at least <NUM> milliseconds and switching the polarization switcher from the first state to the second state may take less than <NUM> milliseconds.

Another electroactive lens system includes a liquid-crystal wave plate in optical series with first and second liquid-crystal lenses. The liquid-crystal wave plate is switchable between a <NUM>-wave retardance and a half-wave retardance within <NUM> milliseconds. The first liquid-crystal lens is switchable between a first state in which it focuses light in a first linear polarization state to a first focal plane and a second state in which it focuses light in the first linear polarization state to 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 to a third focal plane and a second state in which it focuses light in the second linear polarization state to a fourth focal plane.

The liquid-crystal wave plate 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 and second liquid-crystal lenses can transmit light in the second and first linear polarization states, respectively. The first liquid-crystal lens may take more than <NUM> milliseconds (e.g., <NUM> milliseconds or more) to switch before the first and second states.

This electroactive lens system may also include a display in optical communication with the liquid-crystal wave plate and configured to emit light in the first linear polarization state. And it 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 a retardance of the liquid-crystal wave plate, the first liquid-crystal lens, the second liquid-crystal lens, and the display.

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

A fast-switching electro-active lens system can change the focus of linearly polarized light from an object, for example, a display in an augmented reality headset, in periods of less than <NUM> milliseconds (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or fewer milliseconds). It does this with a combination of fast-switching wave plates and slow-switching liquid crystal lenses. Each lens has two eigenaxes orthogonal to each other and to the lens's optical axis. Each lens focuses light polarized along one eigenaxis (the focusing eigenaxis) and transmitting light polarized along the other eigenaxis (the transmitting eigenaxis). The amount of focus, i.e., the optical power, along a lens's focusing eigenaxis depends on the liquid crystal thickness and applied voltage, among other things, and can be tuned continuously (e.g., between a -<NUM> and +<NUM> diopters) or switched among two or more discrete states (e.g., in <NUM> or <NUM> diopter increments between <NUM> and <NUM> diopters). Each lens can provide no (zero) optical power when it is off (when no voltage is applied) or can provide a non-zero optical power when it is off. Other ranges and values of optical power are also possible.

The lenses are aligned so that their optical axes are coincident but their eigenaxes are rotated by <NUM>° with respect to each other-the first lens's focusing eigenaxis is parallel with the second lens's transmitting eigenaxis, and the first lens's transmitting eigenaxis is parallel with the second lens's focusing eigenaxis. The lenses optical axes are aligned coincident with the wave plate's optical axis, and the wave plate's eigenaxes are aligned with the lenses' eigenaxes. In other words, the wave plate and lenses have coincident surface normals and aligned eigenaxes when viewed along their surface normals (the fast-switching electroactive lens system's optical axis).

Because the lenses are aligned with <NUM>°-rotated focusing and transmitting eigenaxes, when the system is illuminated by light that is linearly polarized along one of the system's eigenaxis, one lens focuses the light and other lens transmits the light. Transforming the polarization state of the incident light to the orthogonal linear polarization state (e.g., from horizontal to vertical or from +<NUM>° to -<NUM>°) switches the lenses' operation. The wave plate changes state much faster than the lenses, allowing much quicker user-observable transitions from one optical power to the other than if a single lens were to provide all the optical adjustments. 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 light so that it is ready for the next transition.

<FIG> show symbols used in this disclosure to describe different linear polarization orientations or states. Symbol <NUM> in <FIG> indicates that the direction of the linear polarization as if it were "going into and out of the flat plane of the figure. " Symbol <NUM> in <FIG> indicates that the direction of the linear polarization is orthogonal to the direction indicated by symbol <NUM>. In this case, the direction of the linear polarization is "left and right across the flat plane of the figure. " Symbol <NUM> in <FIG> indicates that the direction of the linear polarization is also orthogonal to the direction indicated by symbol <NUM>. The direction of the linear polarization indicate by symbol <NUM> is "up and down across the flat plane of the figure.

<FIG> show the symbols used in this disclosure to describe the orientation of the rub or alignment directions of the alignment layers used in the liquid-crystal focus changers (electroactive lenses). Symbol <NUM> in <FIG> indicates that the direction of the rub direction as if it were "going into and out of the flat plane of the figure. " Symbol <NUM> in <FIG> indicates that the direction of the rub direction is orthogonal to the direction indicated by symbol <NUM>, and in this case the direction of the rub direction is "left and right across the flat plane of the figure. " Symbol <NUM> in <FIG> indicates that the rub direction is orthogonal to the directions indicated by symbols <NUM> and <NUM>, with the rub direction "up and down across the flat plane of the figure. " Each liquid-crystal lens typically has two alignment layers-one on either side of the liquid crystal material-whose rub directions may be parallel, anti-parallel, or orthogonal to each other. In some cases, only one alignment layer may be used for cost reduction. Using two alignment layers increases both the switching speed and the width of the field of view.

The symbols shown in <FIG> indicate relative directions. Different symbols can be used to indicate the same polarization state in different drawings if those drawings are from different perspectives. Similarly, the same symbol can be used to indicate the different polarization state in different drawings if those drawings are from different perspectives. For example, in a side or profile view of an optical component, symbol <NUM> may indicate a horizontal polarization state and symbol <NUM> may indicate a vertical polarization state. In an end-on view (i.e., a view along the optical axis) of the same optical component, symbol <NUM> may indicate the horizontal polarization state and symbol <NUM> may indicate the vertical polarization state.

<FIG> shows an exploded view of a fast switching lens system <NUM> that includes a polarization orientation changer (also called a polarization rotator, polarization adjuster, or variable retarder) <NUM> in optical communication with a first electroactive lens <NUM> and a second electroactive lens <NUM>. The polarization orientation changer <NUM>, first electroactive lens <NUM>, and second electroactive lens <NUM> are in optical series with each other or stacked together. The lens system <NUM> may utilize planar liquid crystal in all three components <NUM>, <NUM>, and <NUM>, for example, Merck MLC-<NUM>. The first electroactive lens <NUM> has its alignment layer oriented orthogonal to the alignment layer of the second electroactive lens <NUM>. In this case, the first electroactive lens <NUM> has a horizontally oriented liquid-crystal rub direction <NUM> and the second electroactive lens <NUM> has a vertically oriented liquid-crystal rub direction <NUM>. Other rub directions are also possible (for example, ±<NUM>° rub directions), typically used if less-than-<NUM>% focusing is required (in other words, focus only a portion of the light while allowing the other portion to pass through unfocused).

Although the device <NUM> shown in <FIG> is a preferred embodiment, additional polarization switchers may be added to add functional control options. For example, the device <NUM> in <FIG> can switch quickly between the optical powers of lens <NUM> and lens <NUM>. If an additional polarization switcher is positioned between lens <NUM> and lens <NUM>, actuating both polarization switchers makes it possible to change the polarization state of the light propagating through the system so that both lenses <NUM>, <NUM> focus the light. More specifically, the first polarization switcher <NUM> can switch the light from the second polarization state <NUM> to the first polarization state <NUM>, and the second polarization switcher (not shown) can switch the light from the first polarization state <NUM> to the second polarization state <NUM>. Alternatively, both polarization switchers can be actuated so that neither lens <NUM>, <NUM> focuses the light even though one or both lenses are actuated to provide optical power or are being switched between states. This can be useful for providing more optical power than can be provided by a single lens.

In operation, linearly polarized light <NUM> from an object (e.g., a display or spatial light modulator in an augmented or virtual reality system) enters the polarization rotator <NUM> in a second polarization state (e.g., vertically polarized as shown by symbol <NUM>). If the polarization rotator <NUM> is in a first state (e.g., off), as shown in <FIG>, then it emits light <NUM> in a first polarization state, which may be rotated by <NUM>° with respect to the second polarization state (e.g., horizontally polarized as shown by symbol <NUM>). If the polarization rotator <NUM> is in a second state (e.g., on), then it emits light <NUM> whose polarization state is the same as the polarization state as the input light <NUM> (horizontally polarized in this example).

The light <NUM> exiting the polarization adjuster <NUM> enters the first electroactive lens <NUM>, which focuses the light <NUM> to a first focal plane if the light <NUM> is in the first polarization state (e.g., vertically polarized) and the first electroactive lens <NUM> is in a first state (e.g., on). If the light <NUM> is in the first polarization state and the first electroactive lens <NUM> is in a second state (e.g., off), the first electroactive lens <NUM> focuses the light to a second focal plane. And if the light <NUM> is in the second polarization state (e.g., horizontally polarized), it passes through the first electroactive lens <NUM> without being focused by the first electroactive lens <NUM>.

Light <NUM> exiting the first electroactive lens <NUM> enters the second electroactive lens <NUM>, which, like the first electroactive lens <NUM>, is switchable between two states (e.g., on and off states). Unlike the first electroactive lens <NUM>, however, the second electroactive lens <NUM> acts only on light in the second polarization state (e.g., horizontally polarized). When the second electroactive lens <NUM> is in the first state, it focuses light in the second polarization state to a third focal plane. And when the second electroactive lens <NUM> is in the second polarization state, it focuses light in the second polarization state to a fourth focal plane. Light <NUM> in the first polarization state (e.g., vertically polarized) passes through the second electroactive lens <NUM> without being focused by the second electroactive lens <NUM>. Light <NUM> exits the second electroactive lens <NUM> and the system <NUM>.

If the first electroactive lens <NUM> and second electroactive lens <NUM> provide different optical power levels, the lens system <NUM> can be switched among a series of different optical power levels focal lengths by actuating the polarization switcher <NUM>, first electroactive lens <NUM>, and second electroactive lens <NUM>. For example, if the first electroactive lens <NUM> can be switched between optical power levels of <NUM> Diopters and <NUM> Diopters (first/on and second/off states, respectively) and the second electroactive lens <NUM> can be switched between optical power levels of <NUM> Diopters and <NUM> Diopters (first/on and second/off states, respectively), the lens system <NUM> can switched among optical power levels of <NUM>, <NUM>, <NUM>, and <NUM> Diopters by actuating the polarization switcher <NUM>, first electroactive lens <NUM>, and second electroactive lens <NUM>. These optical power levels are just examples; other optical power levels are also possible, including optical power levels that are not evenly spaced, such as optical power levels selected to bring objects into focus at near, near-intermediate, intermediate, far-intermediate, and/or far planes.

The fast switching speed of the polarization adjuster <NUM> makes it possible for the lens system <NUM> to switch among these optical power levels quickly (e.g., within <NUM> or less) even though the first and second electroactive lenses <NUM> and <NUM> may switch slowly (e.g., in <NUM> or more). For instance, while the first electroactive lens <NUM> is on and the polarization adjuster <NUM> is off, the second electroactive lens <NUM> may be transitioned from one optical power to the other without affecting the light propagating through the lens system <NUM>. Once the second lens <NUM> has completed its transition, is ready, and is at the desired optical power, the polarization adjuster <NUM> switches states, causing the second electroactive lens <NUM> to focus the light while the first electroactive lens <NUM> no longer focuses the light even if the first electroactive lens <NUM> is still on.

<FIG> shows the components in an exploded, perspective view, with gaps between the components. Although the lens system would work with gaps as shown in <FIG>, the lens system can also be made with the components next to each other and bonded or integrated together to eliminate reflections at the interfaces. For example, the first electroactive lens <NUM> can share a first substrate with the polarization orientation changer <NUM> and share a second substrate with the second electroactive lens <NUM>.

<FIG> shows an integrated fast-switching electroactive lens system <NUM>. In this system <NUM>, substrates <NUM> and <NUM>, together with liquid crystal layer <NUM>, form the polarization adjuster <NUM>. Substrates <NUM> and <NUM>, together with liquid crystal layer <NUM>, form the first lens <NUM>. And substrates <NUM> and <NUM>, together with liquid crystal layer <NUM>, form the second lens <NUM>. Substrates <NUM> and <NUM> are shared by multiple components and so are coated on each side with separate alignment layers and independently actuated electrodes (not shown).

<FIG> show side views of a cross section of the polarization adjuster <NUM>. <FIG> shows the adjuster <NUM> in an unpowered or off (first) state, while <FIG> shows the adjuster <NUM> in a powered or on (second) state.

The polarization adjuster <NUM> is comprised of a first substrate <NUM> and a second substrate <NUM>, with planar liquid crystal (for example, Merck MLC-<NUM> nematic liquid crystal) sandwiched and sealed between the two substrates <NUM> and <NUM>. On the surface of lower substrate <NUM> is a transparent, electrically conductive coating <NUM>, also called an electrode (for example, indium tin oxide (ITO)). Atop this electrode <NUM> is a transparent alignment layer (for example, polyimide made from Nissan Sunever <NUM> polyimide varnish). The alignment layer is typically applied, cured, and then rubbed with a felt cloth along in the direction of the desired alignment orientation. (<FIG> illustrate possible rubbing directions for the alignment layer. ) Adjacent to electrode <NUM> is the liquid crystal. On the surface of upper substrate <NUM> is another electrically conductive coating (electrode) <NUM>, which can be made of the same material(s) that the first electrode <NUM> is made from.

<FIG> shows a difference between the electrodes <NUM> and <NUM>: when the polarization adjuster <NUM> is off, the alignment layer on the first electrode <NUM> is configured to orient the adjacent liquid crystal molecules in the direction indicated by symbol <NUM>, whereas the alignment layer on the second electrode <NUM> is configured to orient the adjacent liquid crystal molecules in the direction indicated by symbol <NUM>. As a result of this configuration, the liquid crystal molecules are aligned at the first electrode <NUM> in orientation/direction <NUM>, aligned at the second electrode <NUM> in orientation/direction <NUM>, aligned in the middle of the liquid crystal layer in an orientation/direction midway between orientation <NUM> and orientation <NUM>, and gradually twisted closer to orientations <NUM> and <NUM> the closer the liquid crystal is to the first electrode <NUM> and second electrode <NUM>, respectively. This twisted configuration is indicated by the three symbols <NUM> in <FIG>. This twisting of liquid crystal molecules adjusts or changes the polarization direction of light <NUM> from polarization orientation <NUM> as it enters the polarization adjuster <NUM> to polarization orientation <NUM> as it exits the polarization adjuster <NUM>.

<FIG> shows the polarization adjuster <NUM> with a voltage supply <NUM> applying an electric field potential to the first electrode <NUM> while the opposite electric field potential is applied to the second electrode <NUM>. The applied voltage may be an alternating current (AC) signal, such as a sine or square wave. When power is applied, the liquid crystal molecules reorient from orientation <NUM> to orientation <NUM> as shown in <FIG>. In this state, the polarization orientation <NUM> of the light <NUM> entering the polarization adjuster is the same as the polarization orientation <NUM> of the light <NUM> as it exits the polarization adjuster. In other words, applying the voltage to the electrodes <NUM> and <NUM> changes the polarization adjuster's retardance from π/<NUM> to <NUM>. The polarization adjuster <NUM> does not change the light's direction of propagation.

Other configurations of the polarization adjuster are also possible. For instance, the alignment layers can have parallel or anti-parallel rub directions instead of crossed or orthogonal rub directions as in <FIG>. With parallel or anti-parallel rub directions, the polarization adjuster does not change the polarization state of incident light when it is off (i.e., when no voltage is applied across the liquid crystal by the electrodes); its nominal retardance is <NUM>. Instead, the polarization adjuster changes the polarization state of incident light when it is 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 for a retardance change of π/<NUM>.

The polarization adjuster's design parameters, including the liquid crystal material and liquid crystal thickness, may be selected to increase the switching speed. The formulas below give an example design set to achieve fast switching speed and high optical efficiency. Several example turn-off times are shown (indicating that a preferred liquid crystal thickness of either <NUM> or <NUM>), however, the turn-on times may be reduced by using higher-than-needed switching voltages. The liquid crystal used in the preferred embodiment is HAE614752 made by Jiangsu Hecheng Display Technology Co. Other liquid crystals may be used as well, for example, MLC2136 made by Merck Chemicals of Germany.

For a twisted nematic liquid crystal cell placed between two polarizers aligned parallel and perpendicular to the respective surface molecular directors, the transmission is: <MAT> 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/<NUM>), the transmission becomes: <MAT> where x = dΔn/λ. The transmission minima for this expression occur for <MAT>, where m is a positive integer. The first minimum occurs for x = <NUM>, which corresponds to Δn = <NUM>, λ = <NUM> and d = <NUM>.

A polarization switcher that provides a half wave of retardance (i.e., θ = π/<NUM>), should have a liquid crystal layer whose thickness meets the criteria for minimum transmission using the equation given above. For a liquid crystal layer with Δn = <NUM>, λ = <NUM>, a viscosity of <NUM> mPa, and K = <NUM> pN, the liquid crystal layer thickness should <NUM> or <NUM> for a switching time of <NUM> or <NUM>, respectively. These switching times are short enough for the polarization switcher to change state (e.g., turn on or off) without a lag perceptible by a person.

<FIG> illustrate operation of a fast-switching electroactive lens system <NUM> with a polarization adjuster <NUM>, a first electroactive (liquid crystal) lens <NUM>, and a second electroactive (liquid crystal) lens <NUM> in optical series with each other. The first electroactive lens <NUM> has alignment layers rubbed in orientation <NUM> and the second electroactive lens <NUM> has alignment layers rubbed in orthogonal orientation <NUM>. Although <FIG> show gaps between the components, the components can be touching each other and bonded together or otherwise integrated to form a single unit just like the system <NUM> in <FIG>. The fast-switching electroactive lens system <NUM> focuses and/or transmits polarized light emitted a display <NUM>, such as a transparent organic light-emitting diode (OLED) display in an augmented reality system. The fast-switching electroactive lens system <NUM> and display <NUM> are operably coupled to a processor <NUM>, which can control the polarization adjuster <NUM>, first electroactive lens <NUM>, and second electroactive lens <NUM> in response to the content (video imagery) shown on the display <NUM>.

In <FIG>, the polarization adjuster <NUM> is in an off state, as are the electroactive lenses <NUM> and <NUM>. Light entering polarization adjuster <NUM> in polarization orientation <NUM> and exits in orientation <NUM> (i.e., it is changed from one linear polarization state to an orthogonal linear polarization state). In this example, if polarization adjuster <NUM> and lens <NUM> are in the electrically off state and lens <NUM> is switched to the electrically on state, no optical focusing takes place because the orientation of the rub direction of lens <NUM> is orthogonal to the polarization state of the light entering the lens <NUM>. Put differently, if the first electroactive lens <NUM> has no optical power in the off state, and the second electroactive lens <NUM> does not act upon the light in polarization orientation <NUM>, the system <NUM> does not focus incident light.

<FIG> shows polarization adjuster <NUM> still in the electrically off state and the first and second electroactive lenses <NUM> and <NUM> in the electrically on state. In this configuration, the first electroactive lens <NUM> has optical power thanks to a voltage that actuates its liquid crystal material, changing its refractive index distribution. Because the polarization of light entering the first electroactive lens <NUM> matches the orientation of the first electroactive lens's rub direction <NUM>, the first electroactive lens <NUM> focuses the incident light. The second electroactive lens <NUM>, however, does not focus light, regardless of its setting, because its rub direction <NUM> is orthogonal to the polarization orientation <NUM> of the light.

<FIG> shows the polarization adjuster <NUM>, first electroactive lens <NUM>, and second electroactive lens <NUM> in the electrically on state (i.e., with voltages applied to their liquid crystal layers). In this condition, the polarization adjuster <NUM> does not transform the polarization state of the incident light; instead, the polarization adjuster <NUM> transmits the incident light in polarization orientation <NUM>. This means that the light emerging from polarization adjuster <NUM> is no longer polarized in the same orientation of the rub direction <NUM> of the first electroactive lens <NUM> but is now polarized in the same orientation of the rub direction <NUM> of the second electroactive lens <NUM>. As a result, the second electroactive lens <NUM> focuses the incident light but the first electroactive lens <NUM> does not. If the second electroactive lens <NUM> has a higher optical power (shorter focal length) in the on state than the first electroactive lens <NUM>, as shown <FIG>, this change in the polarization state changes the optical power (focal length) of the lens system <NUM> even though the states of the first and second electroactive lenses <NUM> and <NUM> did not change.

<FIG> illustrates a process by which a fast-switching electroactive lens system like the systems in <FIG> and <FIG> can be used to adjust the focus of virtual images appearing in a video or other dynamic environment presented via an augmented, mixed, or virtual reality system. In the following example, the electroactive lens system includes a polarization-changing component (or polarization changer) that can switch between states A (e.g., π/<NUM> retardance) and B (e.g., <NUM> retardance) in <NUM> milliseconds and two focus-changing components (electroactive lenses or focus changers, lenses A and B) that can switch states in about <NUM> milliseconds each. The electroactive lens system is used in an augmented/virtual reality system that shows a video clip of eight seconds duration. Displaying the video clip involves changing the focus every two seconds, with the focus change occurring in <NUM> milliseconds as apparent to the viewer.

This example video clip begins with the digital image at far distance. At the two-second mark, the digital image's simulated distance changes from far distance to far-intermediate as shown in the bottom trace in <FIG>. At the four-second mark, the simulated distance changes from far-intermediate to near. At the six-second mark, the simulated distance changes from near to intermediate. And at the eight-second mark, the simulated distance changes back to far distance from intermediate.

For purposes of this example, the simulated distances for far, far intermediate, intermediate, and near are <NUM> meters, <NUM> meters, <NUM> meter, and <NUM> meters, respectively. To view images at these distances, the electroactive lens system provides net perceptible optical powers, in the same order, of zero diopters, a half diopter, one diopter, and two diopters of optical power, respectively. In this example, lenses A and B are each switchable among at least a subset of these optical powers, with lens A switchable between a zero-diopter state and a two-diopter state and lens B switchable among a zero-diopter state, a half-diopter state, and a one-diopter state.

In this example, when the polarization changer is in state A, lens A is optically present and lens B is not. When polarization changer is in state B, lens A is not optically present and lens B is present. That is, lens A focuses light transmitted by the polarization changer is in state A but not when the polarization changer is in state B, and lens B focuses light transmitted by the polarization changer is in state B but not when the polarization changer is in state A. A lens that is not focusing light, either because the lens is not actuated or because the incident light is the polarization state that isn't focused by the lens, provides an optical power of zero diopters.

At the start of the video, the polarization changer is in state A, lens A is at zero diopters because it is off, and lens B is also at zero diopters because it is off and because the polarization changer is in state A. The net perceptible optical power of the electroactive lens system is zero diopters.

Shortly after the video clip begins, for example, at the one-second mark, a processor coupled to or integrated in the electroactive lens instructs lens B to switch optical power from zero diopters to one-half diopter. While lens B changes focus, the viewer cannot see any optical effects occurring in lens B because the polarization changer has rendered lens B not optically present (the polarization changer is still in state A). Lens B has a full second to complete its change to the new optical power, far more time than required. At the two-second mark in the video clip, the polarization changer switches states from state A to state B, causing lens B to be optically present, causing the net perceptible optical power of the system to change from zero diopters to one-half diopter in <NUM> milliseconds.

Shortly after the two-second mark has passed, for example, at the three-second mark, the processor instructs lens A to switch optical power from zero to two diopters. While lens A changes focus, the viewer cannot see any optical effects in lens A occurring because the polarization changer has rendered lens A not optically present (the polarization changer is still in state B, so the net perceptible optical power of the electroactive lens system remains at one-half diopter). Lens A has a full second to complete its change to the new optical power, far more time than required. At the four-second mark in the video clip, the polarization changer switches states again, causing lens A to be optically present and lens B not to be optically present, resulting in the net perceptible optical power of the system changing from one-half diopters to two diopters in <NUM> milliseconds.

Shortly after the four-second mark has passed, for example, at the five-second mark, the processor instructs lens B to switch optical power from one-half diopter to one diopter. While in the transition state of change, the user cannot see any optical effects occurring because the polarization changer has rendered lens B not optically present. Lens B has a full second to complete its change to the new optical power, far more time than required. At the six-second point in the video clip the polarization changer switches states, resulting in the net perceptible optical power of the system changing from two diopters to one diopter in <NUM> milliseconds.

Shortly after the six-second mark has passed, for example, at the seven-second point, lens A is instructed to switch optical power from one diopter to zero diopters. While lens A changes focus again, the viewer cannot see any optical effects occurring in lens A because the polarization changer has rendered lens A not optically present (the polarization changer is still in state B). Lens A has a full second to complete its change to the new optical power, far more time than required. At the eight-second mark in the video clip, the polarization changer switches states again, causing lens A to be optically present and lens B to be optically absent (not present), resulting in the net perceptible optical power of the system changing from two diopters to zero diopters in <NUM> milliseconds.

This sequence may be modified and repeated as desired, tied to and coordinated by signals from the controller or processor presenting the digital images.

Although the lenses may take hundreds of milliseconds to change focus, the viewer observes each focus change occurring within <NUM> millisecond.

The video output can be prepared beforehand and can be programmed/controlled to be coordinated with the electroactive lens components to reduce the viewer's perception of focus-switching time. However, in some cases, video imagery may not be pre-prepared and cannot be used to control the switching in this pre-programmed manner. Instead, the electroactive lens operates in an on-demand switching mode controlled by the viewer with a switch or other command device. In these cases, a similar strategy may be employed where the polarization changer changes state from one state to another state can be delayed until the focus-changing time period has completed, resulting in the user seeing a <NUM>-millisecond optical switching period and a <NUM>-millisecond lag between the switching command and the execution, which may be more desirable than having the user experience a <NUM> millisecond change-of-focus duration.

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

Although the system functions when randomly polarized light enters the system, for example, non-polarized emission from a non-polarized OLED display, it works best with polarized light. Non-polarized or randomly polarized light can be polarized with a polarizer filter located at the light entry point of the system, or by using display technology that emits polarized light, such as LED displays or polarized OLED displays.

While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize or be able to ascertain, using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims, inventive embodiments may be practiced otherwise than as specifically described. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein.

The above-described embodiments can be implemented in any of numerous ways. For example, embodiments of designing and making the technology disclosed herein may be implemented using hardware or a combination of hardware and 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.

Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood to control over dictionary definitions and/or ordinary meanings of the defined terms.

Claim 1:
An electroactive lens system (<NUM>, <NUM>, <NUM>) comprising:
a polarization switcher (<NUM>, <NUM>) switchable between a first state in which the polarization switcher switches a polarization of light between a first polarization state and a second polarization state and a second state in which the polarization switcher transmits light in the first polarization state;
a first electroactive lens (<NUM>, <NUM>) in optical communication with the polarization switcher and switchable between a focusing state in which the first electroactive lens focuses light in the first polarization state and transmits light in the second polarization state without focusing the light in the second polarization state and a non-focusing state in which the first electroactive lens transmits light in the first polarization state and the second polarization state without focusing the light in the first polarization state or the second polarization state; and
a second electroactive lens (<NUM>, <NUM>) in optical communication with the polarization switcher and the first electroactive lens and switchable between a focusing state in which the second electroactive lens transmits light in the first polarization state without focusing the light in the first polarization state and focuses light in the second polarization state and a non-focusing state in which the second electroactive lens transmits light in the first polarization state and the second polarization state without focusing the light in the first polarization state or the second polarization state.