Compact varifocal configuration

Abstract

One embodiment is directed to a head-mountable viewing component for presenting virtual image information to a user, the head-mountable viewing component comprising: a head-mountable frame; a left optical element for the user's left eye, the left optical element comprising a left fluid / membrane lens coupled to the head-mountable frame and configured to have an electromechanically adjustable focal length for the user's left eye; a right optical element for the user's right eye, the right optical element comprising a right fluid / membrane lens coupled to the head-mountable frame and configured to have an electromechanically adjustable focal length for the user's right eye; and a controller operably coupled to the left optical element and the right optical element and configured to provide one or more commands.

Description

Technical Field

[0003] ,

[0001] (Related Application Data) This application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Application No. 62 / 678,234, filed May 30, 2018. The foregoing application is hereby incorporated by reference in its entirety.

[0002] The present invention relates to a viewing optical assembly, and more particularly to a small variable focus configuration.

Background Art

[0003] It is desirable that the eyepiece display for mixed reality or augmented reality be lightweight, low-cost, have a small shape factor, a wide virtual image field of view, and be as transparent as possible. In addition, it is desirable that it have a configuration that presents virtual image information in multiple focal planes (e.g., two or more) in order to be practical for a wide variety of use cases without exceeding an acceptable tolerance for mismatch between vergence and accommodation. Referring to Figure 1, an augmented reality system is illustrated, characterized by a head-mounted viewing component (2), a handheld controller component (4), and an interconnected auxiliary computing or controller component (6) which may be configured to be worn on the user as a belt pack or equivalent. Each of these components may be operably coupled to one another and to other connected resources (8) such as cloud computing or cloud storage resources (10, 12, 14, 16, 17, 18) via wired or wireless configurations, such as those defined by IEEE 802.11, Bluetooth (RTM), and other connectivity standards and configurations. Various aspects of such components are described, for example, as described in U.S. Patent Applications No. 14 / 555,585, No. 14 / 690,401, No. 14 / 331,218, No. 15 / 481,255, and No. 62 / 518,539 (each of which is incorporated herein by reference as a whole), such as various embodiments of two depicted optical elements (20) through which a user can see the world around them, in addition to a viewing component that may be generated by the associated system component for an augmented reality experience. In some variations, a true variable-focus component may be used as a component of the optical element (20), providing not only one or two focal planes but also its spectrum, which is selectable or adjustable by an integrated control system.Referring to Figures 2A-2C and 3, one category of variable focus configurations comprises a fluid-type lens coupled to a membrane and adjustably housed therein, such that, in response to the rotation of a motor (24), an associated mechanical drive assembly (26) drives a cam member (28) in a rotational state relative to a lever assembly (30), which rotates (48, 46) two opposing field measuring plates (38, 40) relative to a main housing assembly (41), and rotates around an associated rotary pin coupling (32, 34) such that the fluid / membrane lens (36) is compressed (44 / 42, or released depending on the direction / positioning of the motor 24 / cam 28), as shown in Figure 3. This compression / release and reorientation of the opposing field measuring plates (38, 40) relative to each other changes the focus of the fluid / membrane lens (36), thus providing an electromechanically adjustable variable focus assembly. One of the challenges of such a configuration is that, from a geometric standpoint, it is relatively bulky for integration into a head-mountable type of system component (2). Another challenge is that, in such a configuration, there is a consequential change in image position as the focus is varied, due to the nature of the system which reorients the opposing field measurement plates (38, 40) relative to each other as they pivot at the bottom relative to the frame that connects the assemblies. This introduces another undesirable complexity variable that must be addressed in calibration or other steps or configurations. There is a need for smaller variable-focus lens systems and assemblies optimized for use in wearable computing systems. [Overview of the project] [Means for solving the problem]

[0004] One embodiment relates to a head-mountable viewing component for presenting virtual image information to a user, comprising: a head-mountable frame; a left optical element for the user's left eye, coupled to the head-mountable frame and comprising a left fluid / membrane lens configured to have an electromechanically adjustable focal length for the user's left eye; a right optical element for the user's right eye, coupled to the head-mountable frame and comprising a right fluid / membrane lens configured to have an electromechanically adjustable focal length for the user's right eye; and a controller operably coupled to the left optical element and the right optical element and configured to provide one or more commands thereto and to modify the focal lengths of the left optical element and the right optical element. The head-mountable viewing component according to claim 1, wherein at least one of the left optical element and the right optical element comprises an actuation motor coupled between two frame members. The actuation motor may be configured to provide linear actuation. The actuation motor may be configured to provide rotational actuation. Two frame members may be coupled to the left fluid / membrane lens and configured to change the focal length for the user by moving relative to each other. The two frame members may be rotatable relative to each other to correct the focal length for the user. The two frame members may be displaceable relative to each other in a non-rotatable manner. The actuation motor may include a stepper motor. The actuation motor may include a servo motor. The actuation motor may include a piezoelectric actuator. The actuation motor may include an ultrasonic motor. The actuation motor may include an electromagnetic actuator. The actuation motor may include a shape memory metal alloy actuator. The controller may be configured to command the left and right optical elements to adjust to one of two selectable predetermined focal lengths. The controller may be configured to command the left and right optical elements to adjust to one of three or more selectable predetermined focal lengths. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 illustrates a system configuration according to the present invention, characterized by a head-mountable component having a left optical element and a right optical element. [Figure 2] Figures 2A-2c and 3 illustrate various aspects of the fluid lens system. [Figure 3] Figures 2A-2c and 3 illustrate various aspects of the fluid lens system. [Figure 4] Figures 4A-4B illustrate various aspects of a single-motor type compact fluid lens configuration according to the present invention. [Figure 5] Figures 5, 6, and 7A-7B illustrate various aspects of a multi-motorized compact fluid lens configuration according to the present invention. [Figure 6] Figures 5, 6, and 7A-7B illustrate various aspects of a multi-motorized compact fluid lens configuration according to the present invention. [Figure 7] Figures 5, 6, and 7A-7B illustrate various aspects of a multi-motorized compact fluid lens configuration according to the present invention. [Figure 8A] Figures 8A and 8B illustrate various aspects of a system configuration featuring a head-mountable component with a left optical element and a right optical element according to the present invention. [Figure 8B] Figures 8A and 8B illustrate various aspects of a system configuration featuring a head-mountable component with a left optical element and a right optical element according to the present invention. [Modes for carrying out the invention]

[0006] Referring to Figure 4A, two main elements of one variable focus assembly (50) of the present invention are a fluid / membrane lens (36) inserted between two relatively rigid field measuring frame members (70, 72). In the embodiments depicted, between the fluid / membrane lens (36) and each of the rigid field measuring frame members (70, 72) is a stepper motor, servo motor, ultrasonic motor (i.e., lead zirconate titanate), which can be coupled to the rigid field measuring frame members (56, 58) and also to the rotatable adjustable field measuring members (52, 54), using a coupling assembly such as the one depicted in Figure 4B, which features a shaft (62) coupled to a barrel member (60) coupled to a pin (61) that interfacially connects to a rotatable adjustable field measuring member (52, 54), as shown, and can also be coupled to the rotatable adjustable field measuring member (52, 54), etc. Rotatable adjustable field-of-view measuring members (52, 54) that can be controlled and rotatably adjusted relative to rigid field-of-view measuring frame members (70, 72) using a small actuating motor (64) or other electromechanical actuator (for example, one comprising multiple piezoelectric material components, such as lithium niobate or other single-crystal materials, configured in a substantially circular arrangement, operably coupled to a stator and rotor to generate activation of a rotary ultrasonic motor, or operably coupled to a stator and slider to generate activation of a linear translation ultrasonic motor). In one embodiment, the motor (64) may be configured to generate controlled linear motion of the shaft (62) and the interconnected barrel member (60) relative to the cylindrical housing (63) of the motor (64), such that interconnected pins (61) cause the rotatable adjustable field-of-view measuring members (52, 54) to rotate relative to the rigid field-of-view measuring frame members (70, 72) about an axis substantially parallel to the central axis (65) that is perpendicular to the center of the interconnected fluid / membrane lens (36).In another embodiment, the motor (64) may be configured to generate rotational motion of the shaft (62) relative to the cylindrical housing (63) described for the motor (64), such that interconnected pins (61) cause rotatable adjustable field measuring members (52, 54) to rotate relative to rigid field measuring frame members (70, 72) about an axis substantially parallel to a central axis (65) that is perpendicular to the center of an interconnected fluid / membrane lens (36), and the mechanical coupling between the shaft (62) and the barrel member (60) may have a threaded interface. The mechanical interface between the rotatable adjustable field measuring members (52, 54) and the rigid field measuring frame members (70, 72) may be configured to have field measuring features such as inclines, bulges, or steps, which will compress or release the interconnected fluid / membrane lens (36) using a substantially uniform field measuring load, such as by a grouping of three or more interface features (i.e., one every 120 degrees around the 360-degree field measuring interface between the rotatable adjustable field measuring members (52, 54) and the rigid field measuring frame members (70, 72)). In other words, the fluid / membrane lens (36) can be released or tightened relatively uniformly, preferably without substantial movement or reorientation of the image position of the lens relative to the plane. Furthermore, the mechanical field measuring interface may be configured such that a series of levels of tightening or releasing of the fluid / membrane lens (36) can be obtained predictably. For example, in one embodiment, the motor may be operably coupled to a controller such as a microcontroller or microprocessor so that desired or commanded tightening or loosening of the fluid / film lens (36), which can be correlated with a predetermined focal length for the fluid / film lens (36), can be reliably obtained via commands from the controller to the motor, preferably with relatively low latency. One advantage of such a configuration, as shown and described with reference to Figures 4A and 4B, is that a single motor may be used to control the focal length of the fluid / film lens (36).

[0007] Referring to Figure 5-7B, another embodiment is illustrated, configured to provide a substantially uniform field measurement load (and thus focusing without substantial movement or reorientation of image position) for a compact variable focus configuration featuring interconnected fluid / membrane lenses (36).

[0008] Referring to Figure 5, a compact variable focus assembly (68) features two rigid field measurement frame members (70, 72) and an interconnected fluid / membrane lens (36), with a substantially uniform field measurement load on the fluid / membrane lens (36) provided by a plurality of electromagnetic actuators (76, 77, 78), which can be used to controllably push or move the two rigid field measurement frame members (70, 72) away from each other to provide controllable focus adjustment. The electromagnetic actuators (76, 77, 78) are preferably positioned equidistant from each other in a field measurement manner (i.e., about 120 degrees from each other), as shown, to provide a uniform load on a configuration consisting of three actuators. Other embodiments may include more actuators, such as four actuators spaced 90 degrees apart, etc. In one embodiment, the electromagnetic actuators (76, 77, 78) may be operably coupled between the field measurement frame members (70, 72) so as to push or move the field measurement frame members (70, 72) toward each other in a linear motion in response to their operation. In another embodiment, the electromagnetic actuators (76, 77, 78) may be operably coupled between the field measurement frame members (70, 72) so as to cause rotational motion of a mutual coupling member, such as a mutual coupling member similar to the shaft member (62) of the assembly in Figure 4B, which may be interface-connected to one of the field measurement frame members (70, 72) and can be converted, for example, into linear motion, which pushes or moves the field measurement frame members (70, 72) toward each other. In other words, the electromagnetic actuators (76, 77, 78) may be configured to generate either linear or rotational operating motion, which may be used to push or move two rigid field measurement frame members (70, 72) toward or away from each other to provide controllable focus adjustment.

[0009] Preferably, one or more predictable levels of tightening or loosening of the fluid / membrane lens (36) can be obtained through the operation of electromagnetic actuators (76, 77, 78). For example, in one embodiment, the electromagnetic actuators (76, 77, 78) may be operably coupled to a controller such as a microcontroller or microprocessor so that desired or commanded tightening or loosening of the fluid / membrane lens (36), which can be correlated with a predetermined focal length for the fluid / membrane lens (36), can be reliably obtained via commands from the controller to the electromagnetic actuators (76, 77, 78), preferably with relatively low latency.

[0010] Referring to Figure 6, a compact variable focus assembly (74) features two rigid field measuring frame members (70, 72) and an interconnected fluid / membrane lens (36), with a substantially uniform field measuring load on the fluid / membrane lens (36) provided by a plurality of shape memory metal alloy actuators (80, 82, 84), which can be used to controllably push or move the two rigid field measuring frame members (70, 72) relative to each other and to provide controllable focus adjustment. The shape memory metal alloy actuators (80, 82, 84) are preferably positioned equidistant from each other in a field measuring manner (i.e., about 120 degrees from each other), as shown, to provide a uniform load on the configuration consisting of three actuators. Other embodiments may include more actuators, such as four actuators spaced 90 degrees apart, etc. In one embodiment, the shape memory metal alloy actuators (80, 82, 84) may be operably coupled between the field measurement frame members (70, 72) so as to push or move the field measurement frame members (70, 72) toward each other in a linear motion in response to their operation. In another embodiment, the shape memory metal alloy actuators (80, 82, 84) may be operably coupled between the field measurement frame members (70, 72) so as to cause rotational motion of a mutual coupling member, such as a mutual coupling member similar to the shaft member (62) of the assembly in Figure 4B, which may be interface-connected to a threaded member, such as a threaded member similar to the barrel member (60) of the assembly in Figure 4B, which is coupled to one of the field measurement frame members (70, 72) and can be converted into linear motion, for example, to push or move the field measurement frame members (70, 72) toward each other. In other words, the shape memory metal alloy actuators (80, 82, 84) may be configured to generate either linear or rotational operating motion, which may be used to push or move two rigid field measurement frame members (70, 72) toward or away from each other to provide controllable focus adjustment.

[0011] Preferably, one or more predictable levels of tightening or loosening of the fluid / film lens (36) can be obtained through the operation of shape memory metal alloy actuators (80, 82, 84). For example, in one embodiment, the shape memory metal alloy actuators (80, 82, 84) may be operably coupled to a controller such as a microcontroller or microprocessor so that desired or commanded tightening or loosening of the fluid / film lens (36), which can be correlated with a predetermined focal length for the fluid / film lens (36), can be reliably obtained via commands from the controller to the shape memory metal alloy actuators (80, 82, 84) with relatively low latency.

[0012] Referring to Figures 7A and 7B, a compact variable focus assembly (76) features two rigid field measuring frame members (70, 72) and an interconnected fluid / membrane lens (36), with a substantially uniform field measuring load of the fluid / membrane lens (36) provided by a plurality of piezoelectric actuators (86, 88, 90), which can be used to controllably push or move the two rigid field measuring frame members (70, 72) relative to each other to provide controllable focus adjustment. Each piezoelectric actuator (80, 82, 84) may comprise one or more piezoelectric cells configured to generate a given load and displacement change in response to operation, or may comprise a so-called "ultrasound" or "ultrasonic" actuator configuration (i.e., comprising multiple piezoelectric material components comprising one or more piezoelectric materials such as lead zirconate titanate, lithium niobate, or other single-crystal materials, arranged in a substantially circular array, operably coupled to a stator and rotor to generate activation of a rotary ultrasonic motor, or operably coupled to a stator and slider to generate activation of a linear translation ultrasonic motor). Preferably, the piezoelectric actuators (80, 82, 84) are positioned equidistant from each other in a field-of-view manner (i.e., at approximately 120 degrees from each other), as shown, to provide a uniform load to a configuration consisting of three actuators. Other embodiments may include more actuators, such as four actuators spaced at 90 degrees, etc.In one embodiment, the piezoelectric actuators (80, 82, 84) may be operably coupled between the field measurement frame members (70, 72) so as to push or move the field measurement frame members (70, 72) toward each other in a linear motion in response to their operation. In another embodiment, the piezoelectric actuators (80, 82, 84) may be operably coupled between the field measurement frame members (70, 72) so as to cause rotational motion of a mutual coupling member, such as a mutual coupling member similar to the shaft member (62) of the assembly in Figure 4B, which may be coupled to one of the field measurement frame members (70, 72) and interface-connected to a threaded member, such as a threaded member similar to the barrel member (60) of the assembly in Figure 4B, which can be converted into linear motion and push or move the field measurement frame members (70, 72) toward each other. In other words, the piezoelectric actuators (80, 82, 84) may be configured to generate either linear or rotational operating motion, which may be used to push or move two rigid field measurement frame members (70, 72) toward or away from each other to provide controllable focus adjustment.

[0013] Preferably, one or more predictable levels of tightening or loosening of the fluid / membrane lens (36) can be obtained through the operation of piezoelectric actuators (80, 82, 84). For example, in one embodiment, the piezoelectric actuators (80, 82, 84) may be operably coupled to a controller such as a microcontroller or microprocessor so that desired or commanded tightening or loosening of the fluid / membrane lens (36), which can be correlated with a predetermined focal length for the fluid / membrane lens (36), can be reliably obtained via commands from the controller to the piezoelectric actuators (80, 82, 84) with relatively low latency.

[0014] Referring to Figure 7B, depending on the amount of mechanical distance required in each of the piezoelectric actuators for a given variable focus lens configuration, the piezoelectric actuators may comprise an assembly of a series of interconnected individual piezoelectric devices (92, 94, etc.) such that each actuator generates a given mechanical distance to which its activation is added to others in the assembly, thereby generating an overall assembly distance suitable for the application.

[0015] Referring to Figure 8A, an assembly configuration is illustrated, featuring components such as those discussed above with reference to Figures 4A and 4B, including a head-mountable component (2) having a frame (130) that can be mounted on the user's head so that the user's left (100) and right (102) eyes are exposed to optical elements (20, here, the left optical element 110 and the right optical element 112 are separately labeled, and these optical elements feature a left fluid / film lens 36 and a right fluid / film lens 37, respectively). Left (114) and right (116) motors are configured to electromechanically adjust the focal length of each optical element, for example, as described above with reference to Figures 4A and 4B. A controller (108), such as a microcontroller or microprocessor, may be used to issue commands to the motors (114, 116) to adjust the focal length. In various embodiments, cameras (104, 106) may be coupled to a frame (130) and configured to capture data relating to the respective positions of the eyes (100, 102), which may be used by a controller (108) to determine how to command the motors (114, 116) in terms of a desired focal length. For example, if it is determined that the user is focusing on an object close to the wearable component (2), the system may be configured to cause the controller to use the motors to switch to a closer focal length. Figure 8B illustrates a configuration similar to that of Figure 8A, but with an electromechanical operating configuration similar to that described with reference to Figures 5-7B, in which a plurality of motors or actuators (118, 120, 122; 124, 126, 128) may be operably coupled to a controller (108) and used to adjust the focal length of the optical elements (110, 112).

[0016] Various exemplary embodiments of the present invention are described herein. These embodiments are used by reference in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the present invention. Various modifications may be made to the described invention, and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt specific situations, materials, composition of substances, processes, process actions, or steps to the object, spirit, or scope of the invention. Furthermore, as will be understood by those skilled in the art, each individual modification described and illustrated herein has discrete components and features that can be readily separated from or combined with features of any of several other embodiments without departing from the scope or spirit of the invention. All such modifications are intended to be within the scope of the claims associated with this disclosure.

[0017] The present invention includes methods that can be carried out using the subject device. The methods may include the act of providing such a suitable device. Such provision may be carried out by an end user. In other words, the act of “providing” simply requires the end user to obtain, access, approach, position, configure, activate, launch, or otherwise act to provide the device required in the subject method. The methods enumerated herein may be carried out in any order of the enumerated events that is logically possible, and in the order of the events enumerated.

[0018] Exemplary aspects of the present invention, along with details relating to the selection and manufacture of materials, are described above. Other details of the present invention are understood in relation to the patents and published documents referred to above, and are generally grasped or can be understood by those skilled in the art. The same may apply to the method-based aspects of the present invention in terms of additional actions as generally or theoretically adopted.

[0019] In addition, although the present invention has been described with reference to several embodiments incorporating various features optionally, the present invention should not be limited to what is described or shown as being contemplated for each variation of the present invention. Various changes and equivalents that can be made to the present invention (whether or not listed herein or not included for the sake of brevity) can be substituted without departing from the true spirit and scope of the present invention. In addition, when a range of values is provided, it is to be understood that each intervening value between the upper and lower limits of that range and any other stated or intervening value in the stated range is encompassed within the scope of the present invention.

[0020] Also, it is to be assumed that any optional feature of the variations of the present invention described can be described or claimed independently or in combination with any one or more of the features described herein. Reference to a single item includes the possibility that there are a plurality of the same items. More specifically, as used in this specification and the claims associated with this specification, the singular forms "a, an", "said", and "the" include plural references unless specifically stated otherwise. In other words, the use of the article enables "at least one" of the subject items in the above description and the claims associated with this disclosure. Further, note that such claims can be drafted to exclude any optional element. Accordingly, this recitation is intended to serve as a precedent for the use of such exclusive terms as "alone", "only", and equivalents, or the use of "negative" limitations in relation to the listing of claim elements.

[0021] Without the use of such exclusive terms, the term "comprising" in the claims associated with the present disclosure shall be construed to allow for the inclusion of any additional elements, whether or not a given number of elements are recited within such claims, or the addition of features may be regarded as not transforming the nature of the elements recited in such claims. Except where specifically defined herein, all technical and scientific terms used herein shall be given the broadest possible, generally understood meaning while maintaining the validity of the claims.

[0022] The scope of the present invention should not be limited to the provided examples and / or the present specification, but rather should be limited only by the scope of the claim language associated with the present disclosure.

Claims

1. 1. A head-mountable viewing component for presenting an image to a user, comprising: a. a head-mountable frame; a left optical element for presenting an image to the left eye of the user, the left optical element being coupled to the head-mountable frame, the left optical element comprising two left frame members, a left electromechanical device connected between the two left frame members, and a left fluid / membrane lens between the two left frame members, the left fluid / membrane lens having an electromechanically adjustable focal length for the left eye of the user, the electromechanically adjustable focal length of the left fluid / membrane lens being adjustable by squeezing directly opposed sides on a periphery of the left fluid / membrane lens between the two left frame members towards each other, the two left frame members being positioned on the periphery of the left fluid / membrane lens to provide a substantially uniform peripheral load when the two left frame members are moved relative to each other by the left electromechanical device, causing the adjustment of the focal length without movement or reorientation of the image relative to the plane of the left optical element; c) a right optical element for presenting the image to the right eye of the user, the right optical element being coupled to the head-mountable frame, the right optical element comprising two right frame members, a right electromechanical device connected between the two right frame members, and a right fluid / membrane lens between the two right frame members, the right fluid / membrane lens having an electromechanically adjustable focal length for the right eye of the user, the electromechanically adjustable focal length of the right fluid / membrane lens being adjustable by squeezing directly opposed sides on a periphery of the right fluid / membrane lens between the two right frame members towards each other, the two right frame members being positioned on the periphery of the right fluid / membrane lens to provide a substantially uniform peripheral load when the two right frame members are moved relative to each other by the right electromechanical device, causing the adjustment of the focal length without movement or reorientation of the image relative to the plane of the right optical element; d. a controller operatively coupled to the left and right electromechanical devices, the controller configured to provide one or more commands thereto to modify focal lengths of the left and right fluid / membrane lenses; 1. A head-mountable visibility component comprising:

2. The head-mountable viewing component of claim 1 , wherein at least one of the left and right electromechanical devices comprises an actuation motor interconnected between the two frame members of a respective optical element.

3. The head-mountable viewing component of claim 2 , wherein the actuation motor is configured to provide linear actuation.

4. The head-mountable viewing component of claim 2 , wherein the actuation motor is configured to provide rotational actuation.

5. 3. The head-mountable viewing component of claim 2, wherein the frame members of the respective optical elements are coupled to frame members of the fluid / membrane lenses of the respective optical elements, and the frame members of the respective optical elements are configured to change the focal length for the user by linearly moving relative to one another.

6. The head-mountable viewing component of claim 2 , wherein the two frame members of the respective optical elements are rotatable relative to one another to modify the focal length for the user.

7. The head-mountable viewing component of claim 2 , wherein the two frame members of the respective optical elements are displaceable relative to one another in a non-rotational manner.

8. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises a stepper motor.

9. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises a servo motor.

10. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises a piezoelectric actuator.

11. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises an ultrasonic motor.

12. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises an electromagnetic actuator.

13. The head-mountable viewing component of claim 2 , wherein the actuation motor comprises a shape memory metal alloy actuator.

14. The head-mountable viewing component of claim 1 , wherein the controller is configured to command the left and right optical elements to adjust to one of two selectable predetermined focal lengths.

15. The head-mountable viewing component of claim 1 , wherein the controller is configured to command the left and right optical elements to adjust to one of three or more selectable predetermined focal lengths.

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