Patent Description:
To provide a more realistic virtual reality (VR) experience for viewers, some headmounted display (HMD) designers have begun to propose varifocal optical systems to induce the accommodation reflex or response in the eye of the viewer to mimic the effect of the eye of the viewer focusing on virtual objects that are varied in distance from the viewer. Some proposed systems may employ motors to alter various intercomponent distances to achieve such an effect. For example, distances between the eye of the viewer and the display, distances between the display or the eye and one or more lenses or other optical components, or distances between individual optical components may be altered over time to mimic the varying distances of virtual objects from the viewer by causing the eye of the viewer to focus on the virtual object (e.g., by shaping of the human lens, by contracting or dilating the human pupil, and so on) in a manner similar to that in the real world. Such systems may require a significant level of power and space to implement within an HMD system or other optical device.

The accompanying drawings illustrate a number of exemplary embodiments and are a part of the specification.

Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. While the exemplary embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed.

None of the embodiments described with reference to <FIG> mandate the combination of all features recited in at least one independent claim, and they do therefore not constitute embodiments of the claimed invention.

The present disclosure is generally directed to varifocal apparatuses, systems, and methods employing a deformable stepped lens. In some examples, by employing an actuator to apply at least one force to deform the lens (e.g., by applying radial force to one or more locations along a perimeter of the lens toward the center of the lens), the shape of the lens may be altered from one state to another, thus altering the optical power and/or focal length of the lens. As will be explained in greater detail below, embodiments of the instant disclosure may facilitate a low-power, low-volume varifocal system that may be implemented in a virtual reality display system, such as an HMD.

The following will provide, with reference to <FIG>, detailed descriptions of varifocal apparatuses, systems, and methods that may include a deformable stepped lens. An exemplary apparatus including such a lens is discussed in conjunction with <FIG>. A description of a deformable stepped lens to which a force may be applied to the deformable stepped lens to alter its shape, and thus its optical power, is presented in connection with <FIG>. An exemplary HMD is presented in reference to <FIG>. and an exemplary display system that includes a deformable stepped lens employable in the exemplary HMD of <FIG> is discussed in connection with <FIG>. Various embodiments of a varifocal apparatus that may include a deformable stepped lens are discussed with reference to <FIG>. A description of an exemplary system that may employ a varifocal system that includes a deformable stepped lens is presented in conjunction with <FIG>. Further, a method of varifocal operation that may employ a deformable stepped lens is presented in reference to <FIG>, and a method of providing a varifocal system that may include such a lens is provided in connection with <FIG>.

<FIG> is a cross-sectional view of an exemplary varifocal apparatus <NUM> employing a deformable stepped lens <NUM>. As the term is used herein, a deformable stepped lens may be any deformable (e.g., bendable, twistable, or otherwise flexible) lens that employs a stepped (e.g., discontinuous) surface on at least one side of the lens to provide an optical power similar to that of a thicker lens having a continuous surface on both sides of the lens. One example of a deformable stepped lens may be a deformable Fresnel lens, such as a Fresnel lens with a stepped surface that mimics the operation of a convex lens surface. In some examples, deformable stepped lens <NUM> may have a first side that is substantially flat and a second side opposite the first side that includes a plurality of concentric ridges or steps, such as that often seen in a Fresnel lens. However, other types of deformable stepped lenses may be employed in other embodiments.

As illustrated in <FIG>, apparatus <NUM> may also include an actuator <NUM> coupled to deformable stepped lens <NUM> such that, when actuated, may apply force to deformable stepped lens <NUM> to alter its shape (e.g., from a first state to a second state). As a result of the change in shape, an optical power provided by deformable stepped lens <NUM> may be modified (e.g., from a first optical power associated with the first state to a second optical power associated with the second state). In some examples, such as that depicted in <FIG>, actuator <NUM> may apply a radial force along a perimeter of deformable stepped lens <NUM> toward a center of deformable stepped lens <NUM> (e.g., with deformable stepped lens <NUM> initially being in a substantially flat or relaxed state). In at least some embodiments, deformable stepped lens <NUM> may be deformed to acquire a more "domed" shape or appearance, with a center of deformable stepped lens <NUM> moving toward the stepped surface (e.g., as outward movement <NUM>) or away from the stepped surface (e.g., as inward movement <NUM>), depending on the shape of deformable stepped lens <NUM>, the force applied thereto by actuator <NUM>, and/or other factors. In some examples, outward, movement <NUM> of the center of deformable stepped lens <NUM> may result in a controllable decrease in optical power (e.g., an increase in focal length), while inward movement <NUM> of the center of deformable stepped lens <NUM> may result in a controllable increase in optical power (e.g., a decrease in focal length). In some embodiments, deformable stepped lens <NUM> may be made of a polymer (e.g., optically clear silicone) or other material that facilitates a lens of low modulus. Accordingly, in such embodiments, application of a rather modest force may cause a significant change in optical power provided by deformable stepped lens <NUM>.

Further, in some embodiments, actuator <NUM> may apply a force at each of a plurality of distinct portions of deformable stepped lens <NUM>, such as along the perimeter or other portions of deformable stepped lens <NUM>. In such examples, each force may be represented as a corresponding force vector, and at least one of the force vectors may include a direction component that is different from a corresponding direction component of at least one other force vector. For example, each of multiple force vectors operating at a distinct location about a perimeter of deformable stepped lens <NUM> may be directed toward the center of deformable stepped lens <NUM>, thus indicating that each force vector is directed in a different direction from any of the other force vectors. In other embodiments, actuator <NUM> may impart a force along a substantially continuous portion of deformable stepped lens <NUM>, such as along a portion or an entirety of the perimeter thereof.

<FIG> are cross-sectional views of deformable stepped lens <NUM> of <FIG> while providing different optical powers in corresponding states regarding the shape of deformable stepped lens <NUM>. In each of these views, actuator <NUM> is not explicitly depicted therein to simplify the views and the associated discussion. More specifically in reference to <FIG>, deformable stepped lens <NUM> may be in a relaxed state <NUM> (e.g., a state in which deformable stepped lens <NUM> is not subjected to a force that would cause a change from its natural shape). In relaxed state <NUM>, in some examples, an eye <NUM> of a viewer and a display plane <NUM> (e.g., a light-emitting surface of a display device) may be positioned at opposing sides of deformable stepped lens <NUM> such that display plane <NUM> may be in focus at eye <NUM>, as indicated by the selected light rays denoted in <FIG>. In some examples, in relaxed state <NUM>, deformable stepped lens <NUM> may provide some base level of optical power such that an image provided at display plane <NUM> may appear larger and/or closer to eye <NUM> that such an image would otherwise appear to eye <NUM> in the absence of deformable stepped lens <NUM>.

<FIG> depicts deformable stepped lens <NUM> in a deformed state <NUM> in which a radial force <NUM> is applied to a perimeter of deformable stepped lens <NUM> such that the center of deformable stepped lens <NUM> exhibits outward movement <NUM> toward display plane <NUM>. Consequently, as a result of radial force <NUM>, deformable stepped lens <NUM> may acquire a domed shape (e.g., roughly parabolic in profile) directed toward display plane <NUM>. In some examples, the change in shape of deformable stepped lens <NUM> from relaxed state <NUM> (e.g., in which deformable stepped lens <NUM> may be substantially flat) to deformed state <NUM> results in a reduction in optical power from the perspective of eye <NUM> (e.g., from a first optical power in relaxed state <NUM> to a second (lesser) optical power in deformed state <NUM>). Consequently, presuming no changes in focusing in eye <NUM>, eye <NUM> may be focused on a plane positioned beyond display plane <NUM>. Also, in some embodiments, the reduction in optical power may also be attributed, at least in part, to a reduction in distance between the center of deformable stepped lens <NUM> and display plane <NUM>.

<FIG> depicts deformable stepped lens <NUM> in another deformed state <NUM> in which a radial force <NUM> is applied to a perimeter of deformable stepped lens <NUM> such that the center of deformable stepped lens <NUM> exhibits inward movement <NUM> toward eye <NUM>. Consequently, as a result of radial force <NUM>, deformable stepped lens <NUM> may acquire a domed shape (e.g., roughly parabolic in profile) directed toward eye <NUM>. In some embodiments, radial force <NUM> and radial force <NUM> may differ in some respect (e.g., by including an additional vector force component aside from a radial component, by applying force to a particular portion of the perimeter of deformable stepped lens <NUM>, etc.) to cause either deformed state <NUM> or deformed state <NUM>. In some examples, the change in shape of deformable stepped lens <NUM> from relaxed state <NUM> (e.g., in which deformable stepped lens <NUM> may be substantially flat) to deformed state <NUM> results in an increase in optical power from the perspective of eye <NUM> (e.g., from a first optical power in relaxed state <NUM> to a second (greater) optical power in deformed state <NUM>). Consequently, presuming no changes in focusing of eye <NUM>, eye <NUM> may be focused on a plane positioned in front of display plane <NUM>. Also, in some examples, the increase in optical power may also be attributed, at least in part, to an increase in distance between the center of deformable stepped lens <NUM> and display plane <NUM>.

In some embodiments, after an increase or decrease in optical power associated with deformable stepped lens <NUM> resulting from radial force <NUM> or radial force <NUM>, eye <NUM> may alter its optical configuration (e.g., by altering the shape of its lens, by altering the size of its pupil, and so on) so that eye <NUM> may reacquire focus at display plane <NUM>. Accordingly, the viewer may perceive the change in focus as a change in distance between an image presented at display plane <NUM> and eye <NUM>. As a result, the use of radial force <NUM> and/or radial force <NUM> may generate a varifocal effect for eye <NUM> of the viewer. Moreover, in some examples, the magnitude of radial force <NUM> or radial force <NUM> may be related to the amount of change in the optical power provided by deformable stepped lens <NUM>.

While the examples of <FIG> indicate radial force <NUM> and/or radial force <NUM> are applied at a perimeter of deformable stepped lens <NUM>, and are at least primarily directed toward a center of deformable stepped lens <NUM>, alternative examples of a direction of a force and/or a location to which such a force is applied, are possible in other embodiments. For example, one or more forces may be applied to locations other than the perimeter of deformable stepped lens <NUM> in other embodiments, such as at one or both sides of deformable stepped lens <NUM> inside the perimeter. Also, the one or more forces may be applied to such alternative locations, such as away from the center of deformable stepped lens <NUM>, or in other directions apart from toward the center of deformable stepped lens <NUM>. Moreover, while relaxed state <NUM> of <FIG> represents an essentially flat state of deformable stepped lens <NUM>, and deformed states <NUM> and <NUM> represent domed states of deformable stepped lens -<NUM>, other embodiments may employ different states in the absence or presence of external forces. In one example, a relaxed state of deformable stepped lens <NUM> in the absence of an external force may represent a domed shape of deformable stepped lens <NUM>. Further, deformable stepped lens <NUM> may assume a deformed state representing a flat shape in response to one or more radial forces being directed away from the center of deformable stepped lens <NUM>, such as by way of actuator <NUM> pulling an edge area of deformable stepped lens <NUM> away from its center. Other alternative embodiments are also possible.

<FIG> is a perspective view of an exemplary HMD <NUM> that may present images to the eyes (e.g., eye <NUM>) of a viewer as part of a virtual reality (VR), augmented reality (AR), or mixed reality (MR) system. To present these images, HMD <NUM>, in some embodiments, may include at least one exemplary display system <NUM> that may include a varifocal apparatus (e.g., apparatus <NUM>) having a deformable stepped lens (e.g., deformable stepped lens <NUM>). In some embodiments, two separate display systems <NUM>, one per user eye, may be incorporated in HMD <NUM>.

<FIG> is a side view of an exemplary display system <NUM> that may be employed within an HMD (e.g., HMD <NUM> of <FIG>). As shown, display system <NUM> may include a display <NUM> (e.g., a liquid crystal display (LCD), a liquid crystal on silicon (LCoS) display, an organic light-emitting diode (OLED) display, and so on) located on an optical axis <NUM> with an eye <NUM> of a viewer. In some examples in which two display systems <NUM> are incorporated in a single HMD <NUM>, a single shared display <NUM> may be used for both display systems <NUM>.

Also located on optical axis <NUM>, between display <NUM> and eye <NUM>, may be deformable stepped lens <NUM>, some embodiments of which are described above. Also, as discussed earlier, actuator <NUM> may be coupled to deformable stepped lens <NUM> to impart at least one force onto deformable stepped lens <NUM> to alter the optical power provided by deformable stepped lens <NUM>.

In some examples, also located on optical axis <NUM> between eye <NUM> and deformable stepped lens <NUM> may be a rigid lens <NUM>. In other examples, rigid lens <NUM> may be located between deformable stepped lens <NUM> and display <NUM>. In some embodiments, rigid lens <NUM> may provide a base amount of optical power, such as to magnify an image provided by display <NUM> as perceived by eye <NUM> of the viewer. In some examples, the deformation or doming of deformable stepped lens <NUM> via actuator <NUM> may yield differing changes in focal length for different field angles. In some examples, these differences in focal length modification may be mitigated by varying the thickness of deformable stepped lens <NUM> as a function of the radius of deformable stepped lens <NUM> so that the amount and profile of curvature of deformable stepped lens <NUM> under varying levels of force applied by actuator <NUM> may be controlled. In such embodiments, rigid lens <NUM> may be dimensioned to compensate for the variation in thickness of deformable stepped lens <NUM>. In other examples in which deformable stepped lens <NUM> may not be circular (e.g., roughly rectangular) as viewed by eye <NUM>, rigid lens <NUM> may be dimensioned to compensate for that non-circular shape.

Also in display system <NUM>, a controller <NUM> may be communicatively coupled to deformable stepped lens <NUM>. Controller <NUM>, in some embodiments, may include hardware logic, a processor (e.g., a microprocessor or microcontroller) that executes one or more software or firmware instructions, or some combination thereof. In some examples, controller <NUM> may identify an amount of force to be applied via actuator <NUM> to provide a corresponding level of optical power by deformable stepped lens <NUM>. Controller <NUM>, in some embodiments, may determine the desired amount of optical power based on input from an application (e.g., a virtual reality application) being executed in a system that includes at least HMD <NUM>. Controller <NUM> may then direct actuator <NUM> to provide the identified amount of force to alter the shape of deformable stepped lens <NUM> to provide the desired optical power.

As depicted in <FIG>, display system <NUM>, in some embodiments, may include one or more of an input interface <NUM>, a deflectometry subsystem <NUM>, a focus detection subsystem <NUM>, and/or an eye-tracking subsystem <NUM>. In some examples, one or more of input interface <NUM>, deflectometry subsystem <NUM>, focus detection subsystem <NUM>, and/or eye-tracking subsystem <NUM> may be included in, or located external to, HMD <NUM>.

In some examples, input interface <NUM> may receive information (e.g., from the viewer) about an optical correction prescription of the viewer. Based at least in part on this information, controller <NUM> may identify the amount of force to be applied to deformable stepped lens <NUM> to control actuator <NUM>. In some embodiments, the optical correction prescription may include a spherical component that may be provided by deformable stepped lens <NUM>. Further, in some examples, the optical correction prescription may also include a cylindrical component and an axis component associated with astigmatism of eye <NUM>. In such examples, controller <NUM> may identify a plurality of forces to be applied at different locations of deformable stepped lens <NUM> so that different amounts of optical power may be applied at different orientations about optical axis <NUM> according to the spherical, cylindrical, and axis components of the optical correction prescription. Thus, in such examples, the viewer may use HMD <NUM> without corrective eyewear, such as prescription glasses.

Input interface <NUM>, in some embodiments, may provide a user interface (e.g., buttons, switches, keyboard, touchscreen, etc.) that the viewer may employ to enter the optical correction prescription information. In other examples, input interface <NUM> may be a communication interface (e.g., wired or wireless) coupled to a computer, smartphone, or other device that stores the optical correction prescription information. Further, in some embodiments, controller <NUM> may store the optical correction prescription or other information indicative thereof (e.g., control information for actuator <NUM> for providing the proper optical correction) in association with an identity of the viewer so that the information need not be reentered upon subsequent uses of HMD <NUM> by the user.

Deflectometry subsystem <NUM>, if included in display system <NUM>, may measure a current state of the shape of deformable stepped lens <NUM>. Based on the current state of the shape of deformable stepped lens <NUM>, controller <NUM> may select one or more forces to apply to deformable stepped lens <NUM> to alter or adjust the shape of deformable stepped lens <NUM> via actuator <NUM> to provide the desired level of optical power. In some examples, deflectometry subsystem <NUM> may employ any of several techniques involving optical detection, ultrasound detection, or others to detect the current shape of deformable stepped lens <NUM>.

In some embodiments, focus detection subsystem <NUM>, if included in display system <NUM>, may detect a level of focus of an image provided by display <NUM>. onto or into eye <NUM> of the viewer. Based at least in part on the detected level of focus, controller <NUM> may select one or more forces to apply to deformable stepped lens <NUM> to alter the shape of deformable stepped lens <NUM> via actuator <NUM> to provide the desired level of optical power for proper focus to eye <NUM>. In other examples, controller <NUM> may select one or more forces to apply to deformable stepped lens <NUM> to alter the shape of deformable stepped lens <NUM> via actuator <NUM> to intentionally defocus the image from display <NUM> to cause an accommodation reflex in eye <NUM>, as discussed above. In some examples, focus detection subsystem <NUM> may include an optical wavefront sensor or other device for detecting how an image may be perceived in eye <NUM>.

In some examples, eye-tracking subsystem <NUM> (e.g., an infrared (IR) based tracking system), if included in display system <NUM>, may provide information indicating a gaze angle of eye <NUM> (e.g., relative to optical axis <NUM>). Based on this information, controller <NUM> may control the one or more forces imparted on deformable stepped lens <NUM> via actuator <NUM> based on that information. In some examples in which the deformation of deformable stepped lens <NUM> may yield different changes in focal length for different field angles, controller <NUM> may adjust the optical power provided via deformation of deformable stepped lens <NUM> based on the current gaze angle of eye <NUM> in lieu of varying the thickness of deformable stepped lens <NUM>, as described above.

In some embodiments, controller <NUM> may receive information from deflectometry subsystem <NUM>, focus detection subsystem <NUM>, and/or eye-tracking subsystem <NUM> on a repetitive or ongoing basis and control actuator <NUM> accordingly to provide a desired optical power via deformable stepped lens <NUM> over time. In some examples, controller <NUM> may implement a closed-loop feedback control system based on the information received from deflectometry subsystem <NUM>, focus detection subsystem <NUM>, and/or eye-tracking subsystem <NUM>.

<FIG> is perspective view of an exemplary varifocal apparatus 100A that may include a deformable stepped lens (e.g., deformable stepped lens <NUM>). In some embodiments, apparatus 100A may also include an actuator 104A having a ring <NUM>, a plurality of pads <NUM> contacting the perimeter of deformable stepped lens <NUM>, a plurality of flexures <NUM> extending substantially perpendicularly from ring <NUM> and connecting pads <NUM> to ring <NUM>, and a first shape-memory alloy (SMA) wire <NUM> (e.g., shaped as a ring) routed about pads <NUM>. In other embodiments, first SMA wire <NUM> may be routed about flexures <NUM>. In some examples, first SMA wire <NUM> may be a Nitinol (nickel-titanium alloy) wire, although other alloys or materials may be utilized in other embodiments. As depicted in <FIG>, pads <NUM> and flexures <NUM> are positioned equidistant about deformable stepped lens <NUM>. and ring <NUM>, although such an arrangement may not be utilized in other embodiments.

In some examples, when no electrical current is carried by first SMA wire <NUM>, first SMA wire <NUM> may retain a length such that essentially no radial force is applied via pads <NUM> to the perimeter of deformable stepped lens <NUM>, which thus retains a relaxed state (e.g., relaxed state <NUM>) providing a first optical power. In some embodiments, in response to carrying electrical current, first SMA wire <NUM> may heat accordingly, causing a reduction in its length, thus forcing pads <NUM> toward the center of deformable stepped lens <NUM>, thereby deforming the lens into a substantially domed shape and altering the optical power of deformable stepped lens <NUM>, as discussed earlier. In some embodiments, controller <NUM> may directly or indirectly provide an amount of current to first SMA wire <NUM> that is appropriate to cause deformable stepped lens <NUM> to provide the desired amount of optical power.

In the embodiment of <FIG>, first SMA wire <NUM> is positioned toward a side of pads <NUM> closest to flexures <NUM> such that, when first SMA wire <NUM> is heated, the center of deformable stepped lens <NUM> may protrude away from ring <NUM> so that deformable stepped lens <NUM> acquires a first deformed state (e.g., deformed state <NUM>). In other examples, in addition to or in lieu of first SMA wire <NUM>, a second SMA wire <NUM> (the position thereof indicated via dashed line in <FIG>) may be positioned toward a side of pads <NUM> furthest from flexures <NUM> such that, when second SMA wire <NUM> is heated, the center of deformable stepped lens <NUM> may protrude toward ring <NUM> so that stepped deformable stepped lens <NUM> acquires a second deformed state (e.g., deformed state <NUM>). In embodiments in which both first SMA wire <NUM> and second SMA wire <NUM> are used, SMA wires <NUM> and <NUM> may be located on opposing sides of a plane defined by the perimeter of deformable stepped lens <NUM> so that deformable stepped lens <NUM> may be domed in either direction relative to ring <NUM>, thus potentially extending the range of optical powers that may be provided by deformable stepped lens <NUM>.

In some embodiments, multiple SMA wires may be employed instead of a single, thicker SMA wire, such as first SMA wire <NUM> or second SMA wire <NUM>. In doing so, the multiple SMA wires may provide a similar level of radial force to deformable stepped lens <NUM> when heated, while possibly cooling more quickly due to exhibiting a greater surface area than a single SMA wire <NUM> or <NUM>, thus possibly facilitating a more responsive relaxation of deformable stepped lens <NUM>. when the flowing of current through the multiple SMA wires ceases.

Unlike the example of deformable stepped lens <NUM> of <FIG>, the perimeter of deformable stepped lens <NUM> may not be circular, in some examples. In such cases, flexures <NUM> may be of different thicknesses, or the distribution of flexures <NUM> and pads <NUM> about the perimeter of deformable stepped lens <NUM> may not be equidistant, so that a distribution of the force imparted by first SMA wire <NUM> and/or second SMA wire <NUM> may actuate deformable stepped lens <NUM> in a rotationally symmetrical dome shape about the center of deformable stepped lens <NUM>.

In some embodiments, an actuator component other than first SMA wire <NUM> or second SMA wire <NUM> may be employed to provide the radial force by way of flexures <NUM> and pads <NUM>, such as electroactive polymers (EAPs) that may lengthen and contract in response to an electric field.

In some examples, controller <NUM> may compensate for a hysteretic response of apparatus 100A. More specifically, apparatus 100A may require some period of time during which current flows before first SMA wire <NUM> or second SMA wire <NUM> imparts a desired force on the perimeter of deformable stepped lens <NUM>, and may require cooling for some period of time after current ceases to flow prior to first SMA wire <NUM> or second SMA wire <NUM> lengthening, thus returning deformable stepped lens <NUM> to its relaxed state (e.g., relaxed state <NUM>). In such embodiments, controller <NUM> may implement a predictive control loop to anticipate the need to alter the current through first SMA wire <NUM> or second SMA wire <NUM>. In other examples, the controller <NUM> may also employ eye-tracking subsystem <NUM> to anticipate the need to alter the current to first SMA wire <NUM> or second SMA wire <NUM>, such as by anticipating a future gaze angle of eye <NUM> based on a current gaze angle, a direction and/or rate of change of gaze angle, and the like.

<FIG> is a front view of another exemplary varifocal apparatus 100B that may include a deformable stepped lens (e.g., deformable stepped lens <NUM>). In addition to deformable stepped lens <NUM>, apparatus 100B may include a plurality of actuators <NUM> (e.g., collectively operating as actuator <NUM> of <FIG>), each of which may impart a radial force toward the center of deformable stepped lens <NUM> to alter the optical power of deformable stepped lens <NUM>. As depicted in <FIG>, actuators <NUM> may be spaced equidistant about the perimeter of deformable stepped lens <NUM>, although other spacings may be employed in other embodiments. Further, in some examples, such as when deformable stepped lens <NUM> is circular (e.g., as in <FIG>), actuators <NUM> may each simultaneously impart the same magnitude of force to each associated location of deformable stepped lens <NUM>, such as to provide an optical power that is substantially the same in all directions about optical axis <NUM> (e.g., rotationally symmetrical about the center of deformable stepped lens <NUM>). In other embodiments, such as when providing correction for astigmatism of eye <NUM>, different amounts of force may be applied by actuators <NUM> to provide an optical power that varies about optical axis <NUM>, such as to accommodate astigmatism of eye <NUM>. Also, in some examples, actuators <NUM> may be positioned and/or oriented relative to the perimeter of deformable stepped lens <NUM> to force deformable stepped lens <NUM> to protrude in one direction or another when the force is applied, in a manner analogous to that provided above by apparatus 100A of <FIG>. Examples of actuators <NUM> include, but are not limited to, stepper motors, each of which controller <NUM> may control independently.

<FIG> is a front view of yet another exemplary varifocal apparatus 100C that may include a deformable stepped lens (e.g., deformable stepped lens <NUM>). In some embodiments, apparatus 100C may include an aperture mechanism <NUM> that may be driven by a single actuation motor (e.g., a stepper motor) not explicitly depicted in <FIG>. Aperture mechanism <NUM>, in response to a force provided by the actuation motor, may apply a force at multiple points on the perimeter of deformable stepped lens <NUM>. In some examples, aperture mechanism <NUM> may be arranged in a fashion similar to a traditional camera aperture mechanism, with multiple overlapping segments that move simultaneously based on the force from the actuation motor to increase or reduce a radial force at each contact point along the perimeter of deformable stepped lens <NUM> by a segment of aperture mechanism <NUM>. In some examples, the number of contact points may equal the number of segments. While six contact points are illustrated in <FIG>, greater or fewer numbers of contact points and segments may be employed in other examples, with a greater number of points possibly providing a more evenly distributed radial force about the perimeter of deformable stepped lens <NUM>.

<FIG> is a block diagram of an exemplary system <NUM> that may employ a varifocal apparatus (e.g., apparatus <NUM>, 100A, 100B, or 100C) that includes a deformable stepped lens (e.g., deformable stepped lens <NUM>). As illustrated in <FIG>, exemplary system <NUM> may include one or more modules <NUM> for performing one or more tasks. As will be explained in greater detail below, modules <NUM> may include a prescription determination module <NUM> and a force control module <NUM>. Although illustrated as separate elements, one or more of modules <NUM> in <FIG> may represent portions of a single module or application.

In the example embodiments described in greater detail below, system <NUM> may be employed as at least a portion of a display system (e.g., display system <NUM> of <FIG> and <FIG>) for providing varifocal functionality for users of an HMD (e.g., HMD <NUM> of <FIG>) or other display device. Such a system may include additional elements <NUM>, such as deformable stepped lens <NUM>, actuator <NUM>, input interface <NUM>, deflectometry subsystem <NUM>, focus detection subsystem <NUM>, and/or eye-tracking subsystem <NUM>. Additionally, one or more modules <NUM> and/or additional elements <NUM> (e.g., input interface <NUM>), or portions thereof, may reside outside HMD <NUM> or other display device.

Prescription determination module <NUM>, in some embodiments, may receive viewer identification information (e.g., from input interface <NUM>) and corresponding optical correction prescription information. Based on such information, prescription determination module <NUM> may store information indicative of the prescription (e.g., the optical correction prescription itself, control information for actuator <NUM>, or the like) for each viewer.

In some examples, focus control module <NUM> may receive information to identify or generate a desired optical power that is to be provided by way of imparting a force onto deformable stepped lens <NUM> via actuator <NUM>. Such information, as discussed above, may include optical correction prescription information, information from a VR or similar application, a current gaze angle of the user, a proposed accommodation response to be elicited from the eyes of the user, a current force being applied via actuator <NUM>, relationships between force and optical power provided by deformable stepped lens <NUM>, and/or the like. From such information, focus control module <NUM> may generate control information for actuator <NUM> to impart a force on deformable stepped lens <NUM> to provide a desired optical power for the eyes of the viewer. In some examples, the optical power may facilitate the focusing of the image from a display (e.g., display <NUM> of <FIG>) onto the eyes, and/or may facilitate slight off-focusing of such an image to elicit the accommodation reflex.

In certain embodiments, one or more of modules <NUM> in <FIG> may represent one or more software applications or programs that, when executed by a computing device, may cause the computing device to perform one or more tasks. One or more of modules <NUM> in <FIG> may also represent all or portions of one or more special-purpose computers configured to perform one or more tasks.

As illustrated in <FIG>, system <NUM> may also include one or more memory devices, such as memory <NUM>. Memory <NUM> generally represents any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, memory <NUM> may store, load, and/or maintain one or more of modules <NUM>. As illustrated in <FIG>, system <NUM> may also include one or more physical processors, such as physical processor <NUM>, that may access and/or modify one or more of modules <NUM> stored in memory <NUM>, thus operating as controller <NUM> of <FIG>. Additionally or alternatively, physical processor <NUM> may execute one or more of modules <NUM>. In yet other examples, one or more of modules <NUM>, or portions thereof, instead may be implemented as hardware components not stored in memory <NUM>, such as electronic circuitry for performing one or more tasks described above. Additionally, in some examples, memory <NUM> may include information generated and/or employed by modules <NUM> (e.g., viewer identifiers, information describing optical correction prescriptions of the viewers, control information for actuator <NUM>, and so on), as described above.

In other examples, some functionality described above as performed by physical processor <NUM> executing modules <NUM> may instead be performed by special-purpose circuitry included in system <NUM>.

<FIG> is a flow diagram of an exemplary method <NUM> of varifocal operation that may employ a deformable stepped lens (e.g., deformable stepped lens <NUM>). The steps shown in <FIG> may be performed by any suitable computer-executable code and/or computing system, including the system(s) illustrated in <FIG> and <FIG>. In one example, each of the steps shown in <FIG> may represent an algorithm whose structure includes and/or is represented by multiple sub-steps, examples of which are described above in greater detail.

As illustrated in <FIG>, at step <NUM>, an amount of force to be applied to the deformable stepped lens may be identified (e.g., by focus control module <NUM>). In some embodiments, the amount of force may be based on a particular optical power to be provided by the deformable stepped lens in view of one or more sources of information, including, but not limited to, optical correction prescription information (e.g., received via prescription determination module <NUM>) for the eyes of the viewer, VR application information, current gaze angle information, information relating force magnitudes to resulting optical powers provided by the deformable stepped lens, and/or the like. At step <NUM>, an actuator (e.g., actuator <NUM>) may be directed to apply the identified amount of force to the deformable stepped lens from a first state to the second state, where the deformable stepped lens may include or provide a first optical power in the first state and a second optical power in the second state that is different than the first optical power.

<FIG> is a flow diagram of an exemplary method <NUM> of providing a varifocal system (e.g., display system <NUM> of <FIG>) that may include a deformable stepped lens (e.g., deformable stepped lens <NUM>). At step <NUM>, an actuation subsystem (e.g., actuator <NUM>) may be mechanically coupled to the deformable stepped lens that, when held in a first state by the actuation subsystem, has a shape that provides a first optical power. In some examples, the first state may be a relaxed state, in which a force is not being imparted onto the deformable stepped lens, or may be deformed state, in which at least some force is being imparted onto the deformable stepped lens. At step <NUM>, a control subsystem (e.g., including controller <NUM>) may be communicatively coupled to the actuation subsystem to direct the actuation subsystem to apply a force to the deformable stepped lens, where the force alters the shape of the lens from the first state to a second state, and where the lens, when held in the second state, provides a second optical power that is different from the first optical power.

As explained above in conjunction with <FIG>, the apparatuses, systems, and methods described herein may facilitate a varifocal optical system, such as what may be employed in an HMD or other display system. In some examples, the use of a deformable stepped lens and corresponding actuator, as described above, may provide a low-power, volume-efficient means of providing accurate focus for the eyes of a viewer, such as for focusing on an image of a display. Moreover, in some embodiments, the apparatuses, systems, and methods herein may also take into account an optical correction prescription of the viewer, thus possibly relieving the viewer of the burden of wearing corrective eyewear, such as prescription glasses, when viewing the display. In addition, slight changes in force imparted by the actuator on the deformable stepped lens may result in slight alterations in optical power, which may be useful in eliciting an optical accommodation reflex in the eyes of the viewer, thus potentially lending a greater degree of realism to the images presented to the user by the display system.

As detailed above, the computing devices and systems described and/or illustrated herein broadly represent any type or form of computing device or system capable of executing computer-readable instructions, such as those contained within the modules described herein. In their most basic configuration, these computing device(s) may each include at least one memory device and at least one physical processor.

In some examples, the term "memory device" generally refers to any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, a memory device may store, load, and/or maintain one or more of the modules described herein. Examples of memory devices include, without limitation, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, Hard Disk Drives (HDDs), Solid-State Drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, or any other suitable storage memory.

In some examples, the term "physical processor" generally refers to any type or form of hardware-implemented processing unit capable of interpreting and/or executing computer-readable instructions. In one example, a physical processor may access and/or modify one or more modules stored in the above-described memory device. Examples of physical processors include, without limitation, microprocessors, microcontrollers, Central Processing Units (CPUs), Field-Programmable Gate Arrays (FPGAs) that implement softcore processors, Application-Specific Integrated Circuits (ASICs), portions of one or more of the same, variations or combinations of one or more of the same, or any other suitable physical processor.

Although illustrated as separate elements, the modules described and/or illustrated herein may represent portions of a single module or application. In addition, in certain embodiments one or more of these modules may represent one or more software applications or programs that, when executed by a computing device, may cause the computing device to perform one or more tasks. For example, one or more of the modules described and/or illustrated herein may represent modules stored and configured to run on one or more of the computing devices or systems described and/or illustrated herein. One or more of these modules may also represent all or portions of one or more special-purpose computers configured to perform one or more tasks.

In addition, one or more of the modules described herein may transform data, physical devices, and/or representations of physical devices from one form to another. For example, one or more of the modules recited herein may receive data (e.g., application data, optical correction data, etc.) to be transformed, and transform the received data into control signals for an actuator to provide a desired optical power via a deformable stepped lens. Additionally or alternatively, one or more of the modules recited herein may transform a processor, volatile memory, nonvolatile memory, and/or any other portion of a physical computing device from one form to another by executing on the computing device, storing data on the computing device, and/or otherwise interacting with the computing device.

In some embodiments, the term "computer-readable medium" generally refers to any form of device, carrier, or medium capable of storing or carrying computer-readable instructions. Examples of computer-readable media include, without limitation, transmission-type media, such as carrier waves, and non-transitory-type media, such as magnetic-storage media (e.g., hard disk drives, tape drives, and floppy disks), optical-storage media (e.g., Compact Disks (CDs), Digital Video Disks (DVDs), and BLU-RAY disks), electronic-storage media (e.g., solid-state drives and flash media), and other distribution systems.

Embodiments of the instant disclosure may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., a virtual reality (VR), an augmented reality (AR), a mixed reality (MR), a hybrid reality, or some combination and/or derivatives thereof. Artificial reality content may include completely generated content or generated content combined with captured (e.g., real-world) content. The artificial reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional effect to the viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, e.g., create content in an artificial reality and/or are otherwise used in (e.g., perform activities in) an artificial reality. The artificial reality system that provides the artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

The process parameters and sequence of the steps described and/or illustrated herein are given by way of example only and can be varied as desired. The various exemplary methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.

The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed.

The embodiments disclosed herein should be considered in all respects illustrative and not restrictive.

Claim 1:
A head-mounted display apparatus comprising:
a deformable stepped lens (<NUM>) that:
provides a first optical power when a shape of the deformable stepped lens comprises a first state; and
provides a second optical power different from the first optical power when the shape of the deformable stepped lens comprises a second state different from the first state; and characterised by,
an actuator (<NUM>) coupled to the deformable stepped lens that is configured to apply an amount of force identified with the second optical power to the deformable stepped lens to alter the shape of the deformable stepped lens from the first state to the second state.