Optical assembly

Abstract

An optical assembly comprises an optical element having an adaptable shape, a support structure, a first transmission assembly, a second transmission assembly, and an actuator assembly. The support structure defines a first axis. The actuator assembly is configured to exert a force on both the first transmission assembly and the second transmission assembly. The first transmission assembly comprises a first contact element and a first locking element. The second transmission assembly comprises a second contact element and a second locking element.

Description

[0001] Optical Assembly

[0002] Field

[0003] The present application relates to an optical assembly, and in particular to an optical assembly comprising an optical element having an adaptable shape.

[0004] Background

[0005] An eye focuses on an object by focusing light from the object on the retina of the eye. The shape of the eye and the condition of the refractive elements of the eye can affect the eye’s ability to focus light on the retina. For example, a person may suffer from one or more of near-sightedness, far-sightedness and astigmatism.

[0006] A lens (such as in spectacles or contact lenses) may be worn to correct for near-sightedness, far-sightedness and astigmatism. A prescription may comprise a spherical power (to correct for near-sightedness or far-sightedness) and / or a cylindrical power and direction (to correct for astigmatism). A person’s prescription may change over time. Furthermore, a person may also experience problems with adjusting the focus of the eye for objects at different distances. Glasses or contact lenses with fixed optical properties, such as a fixed focal length, may not be able to correct for this.

[0007] Headsets such as virtual reality (VR) and augmented reality (AR) headsets present virtual objects to a user, either replacing or supplementing the visual environment around the user. The virtual objects may be presented as if being at certain simulated distances from the user. It is desirable that the user is able to focus on these objects at the simulated distance. The simulated distances may change, meaning that it is desirable for the VR or AR headset to change its optical properties such that the user’s eyes adjust and focus on the virtual objects as they would on real objects. The VR or AR headset may be worn by people having different interpupil lary distances. It may be desirable for a VR or AR headset to adapt to the eyesight of the person wearing the VR or AR headset.

[0008] It is advantageous for the comfort of a user that any headset is compact and lightweight. A VR or AR headset or, indeed, glasses, may be provided in a range of shapes and sizes. It is beneficial for optical assemblies used in glasses or headsets to be able to accommodate a range of shapes and sizes of headset. Furthermore, a VR or AR headset may be battery powered, so it is beneficial for components of the VR or AR headset to require little power to operate.

[0009] A lens with an adaptive shape may be used to achieve one or both of adaptable spherical and adaptable cylindrical power. Changes to the shape of the lens may be required in a plurality of locations. It may be bulky, heavy and costly to provide a fully functioning actuator at multiple locations around a lens, especially if each actuator requires zero power to hold in position after having adjusted to the desired position.

[0010] Summary

[0011] According to an aspect of the present invention, there is provided an optical assembly comprising: an optical element having an adaptable shape; a support structure, wherein a first axis is defined relative to the support structure; a first transmission assembly; a second transmission assembly; an actuator assembly configured to exert a force on both the first transmission assembly and the second transmission assembly; wherein the first transmission assembly comprises: a first contact element in contact with the optical element at a first location so as to influence the adaptable shape of the optical element at the first location in a direction parallel to the first axis, the first contact element being movable relative to the support structure; and a first locking element having a transmission state in which the first locking element enables movement of the first contact element relative to the support structure, and a brake state in which the first locking element prevents movement of the first contact element relative to the support structure; and wherein the second transmission assembly comprises: a second contact element in contact with the optical element at a second location different from the first location so as to influence the adaptable shape of the optical element at the second location in a direction parallel to the first axis, the second contact element being movable relative to the support structure; and a second locking element having a transmission state in which the second locking element enables movement of the second contact element relative to the support structure, and a brake state in which the second locking element prevents movement of the second contact element relative to the support structure; such that with the first locking element in its transmission state and the second locking element in its brake state, the force exerted by the actuator assembly results in movement of the first contact element without movement of the second contact element; and such that with the first locking element in its brake state and the second locking element in its transmission state, the force exerted by the actuator assembly results in movement of the second contact element without movement of the first contact element.

[0012] In this way, one actuator may be deployed for moving both the first contact element and the second contact element independently. As such, weight, volume and power consumption are all reduced relative to an optical assembly having more than one actuator.

[0013] The actuator assembly may comprise a shape memory alloy (SMA) element. SMA elements are precise and reliable actuators, that are power-efficient and compact.

[0014] The optical element may comprise a membrane having an adaptable shape. The optical element may be a fluid lens, such as a liquid lens or a gel lens.

[0015] The first contact element may be restricted (i.e. constrained) to moving in a direction parallel to the first axis and the second contact element may be restricted (i.e. constrained) to moving in a direction parallel to the first axis. In this way, controlling movement of the first and second contact elements may be easier because of limiting degrees of freedom.

[0016] The first locking element may be configured to transition between its transmission state and its brake state by movement in a direction perpendicular to the first axis and / or the second locking element may be configured to transition between its transmission state and its brake state by movement in a direction perpendicular to the first axis.

[0017] In this way, the direction of movement required for transition between transmission state and brake state may be perpendicular to movement of the first and second contact elements for adapting the shape of the optical element. In the brake state of the first locking element, the first contact element may engage with the support structure to prevent relative movement between the first contact element and the support structure; and in the brake state of the second locking element, the second contact element may engage with the support structure to prevent relative movement between the second contact element and the support structure. Such engagement may be indirect engagement (e.g. via another component of the optical assembly). In this way, the first and second contact elements may be locked relative to the support structure.

[0018] The first contact element may be configured to move the optical element at the first location so as to influence the adaptable shape of the optical element at the first location; and the second contact element may be configured to move the optical element at the second location so as to influence the adaptable shape of the optical element at the second location. The first and second locations may be different and may be positions around the circumference of the optical element. Accordingly, precise movement of the first and second contact elements may result in precise changing of the shape of the optical element.

[0019] The actuator assembly may comprise an actuator and an intermediate portion between the actuator and the first and second transmission assemblies, wherein the intermediate portion is movable relative to the support structure and comprises a first part configured to drive the first contact element and a second part configured to drive the second contact element. In this way, movement of the actuator may effectively be selectively multiplexed to the first and second contact elements.

[0020] The intermediate portion may be movable in a primary plane orthogonal to the first axis. Accordingly, the actuator needs only to actuate in the primary plane or in a direction parallel to the primary plane.

[0021] The intermediate portion may be movable in a direction parallel to the primary axis and may optionally be constrained to move along an axis parallel to the primary axis. For example, the intermediate part may comprise an annulus which is driven to move along the primary axis (or in a direction parallel to the primary axis) and optionally which is prevented (e.g. by a bearing arrangement) from moving in any other degrees of freedom.

[0022] The intermediate portion may comprise one or more surfaces, wherein each of the one or more surfaces is at an acute, non-zero angle with respect to the primary plane. In this way, movement in the plane may be converted into movement out of the plane.

[0023] In the transmission state of the first locking element, the first locking element may be detached or disengaged from the support structure; and in the transmission state of the second locking element, the second locking element may be detached or disengaged from the support structure. Accordingly, the first and second contact elements may be movable relative to the support structure.

[0024] In the transmission state of the first locking element, the first locking element may engage with the intermediate portion; and in the transmission state of the second locking element, the second locking element may engage with the intermediate portion. In this way, movement of the actuator may be transferred to movement of the first and second contact elements.

[0025] The first locking element may have an overlap state which occurs during a transition between the transmission state and the brake state, and during a transition between the brake state and the transmission state, wherein in the overlap state the first locking element engages with both the support structure and the intermediate portion; and the second locking element may have an overlap state which occurs during a transition between the transmission state and the brake state, and during a transition between the brake state and the transmission state, wherein in the overlap state the second locking element engages with both the support structure and the intermediate portion. In this way, it is possible to avoid a state in which the first locking element is locked neither to the support structure nor to the contact element, which would be likely to result in unpredictable shape behaviour of the lens. In a second arrangement, the first transmission assembly may comprise a first compliant member that extends between the first part of the intermediate portion and the first contact element; and the second transmission assembly further comprises a second compliant member that extends between the second part of the intermediate portion and the second contact element. In this way, the compliant members may absorb a force that would otherwise be exerted by the intermediate portion such that the force is not transmitted to the first and second contact elements.

[0026] In the brake state of the first locking element, a force exerted by the first part of the intermediate portion may be absorbed by the first compliant member; and in the brake state of the second locking element, a force exerted by the second part of the intermediate portion may be absorbed by the second compliant member.

[0027] In a third arrangement, the actuator assembly may comprises a pump configured to pump fluid into and out of the fluid lens. In this way, a single pump may be used to control the shape of the optical element. Pressure exerted by fluid within the lens may cause the shape of the optical element to adapt. The first contact element and the second contact element may influence the manner in which the shape of the optical element adapts in response to pressure exerted by fluid within the lens.

[0028] According to another aspect of the disclosure, there is provided a head-mounted device comprising an optical assembly as described.

[0029] According to another aspect of the disclosure, there is provided a method of adapting a shape of an optical element of an optical assembly, the optical assembly comprising: the optical element having an adaptable shape; a support structure, wherein a first axis is defined relative to the support structure; a first transmission assembly; a second transmission assembly; an actuator assembly configured to exert a force on both the first transmission assembly and the second transmission assembly; wherein the first transmission assembly comprises: a first contact element in contact with the optical element at a first location so as to influence the adaptable shape of the optical element at the first location in a direction parallel to the first axis, the first contact element being movable relative to the support structure; and a first locking element having a transmission state in which the first locking element enables movement of the first contact element relative to the support structure, and a brake state in which the first locking element prevents movement of the first contact element relative to the support structure; and wherein the second transmission assembly comprises: a second contact element in contact with the optical element at a second location different from the first location so as to influence the adaptable shape of the optical element at the second location in a direction parallel to the first axis, the second contact element being movable relative to the support structure; and a second locking element having a transmission state in which the second locking element enables movement of the second contact element relative to the support structure, and a brake state in which the second locking element prevents movement of the second contact element relative to the support structure; wherein the method comprises: engaging the first locking element in its transmission state and the second locking element in its brake state, and exerting a force from the actuator to move the first contact element without causing movement of the second contact element; and engaging the first locking element in its brake state and the second locking element in its transmission state, and exerting a force from the actuator to move the second contact element without causing movement of the first contact element.

[0030] In this way, the shape of the optical element may be controlled using only one actuator.

[0031] Brief description of the drawings

[0032] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0033] Figure 1 is a schematic view of the first embodiment of an optical assembly comprising a liquid lens with an adaptable shape the optical assembly having first and second contact elements that are movable by the actuator in a direction parallel to the optical axis, showing the first and second locking elements in their brake states;

[0034] Figure 2 is a schematic view of the first embodiment of Figure 1, showing the first and second locking elements in their transmission states;

[0035] Figure 3 is a schematic view of the first embodiment of Figure 1 , wherein the first and second contact elements have moved in a first direction so as to provide spherical power without cylindrical power;

[0036] Figure 4 shows the same arrangement as Figure 3, wherein the first locking element is in the brake state and the second locking element is in the transmission state;

[0037] Figure 5 shows the same arrangement as Figure 4, wherein the second contact element has moved in the second direction, so as to generate an element of cylindrical power in the lens;

[0038] Figure 6 shows the same arrangement as Figure 5, wherein both the first and the second locking elements are in the brake state;

[0039] Figure 7 shows the same arrangement as Figure 6, wherein both the first and the second locking elements are in the transmission state;

[0040] Figure 8 shows the same arrangement as Figure 7, wherein both the first and second contact elements have moved by an equal amount in a first direction so as to increase the spherical power of the lens whilst maintaining the cylindrical power of the lens, and wherein both the first and the second locking elements are in the transmission state;

[0041] Figure 9 shows the same arrangement as Figure 8, wherein both the first and the second locking elements are in the brake state;

[0042] Figure 10 is a schematic view of a second embodiment of an optical assembly comprising a liquid lens with an adaptable shape the optical assembly having a compliant coupling between the first and second contact elements and the actuator in a direction parallel to the optical axis, showing the first and second locking elements in their brake states;

[0043] Figure 11 is a schematic view of the second embodiment of Figure 10, showing the first and second locking elements in their transmission states and having moved in a first direction so as to provide spherical power without cylindrical power;

[0044] Figure 12 shows the same arrangement as Figure 11, wherein the first locking element is in its brake state and the second contact element has moved in the second direction, so as to alter the cylindrical power of the lens;

[0045] Figure 13 shows the same arrangement as Figure 12, wherein the second locking element is in its brake state and the first contact element has moved in the second direction to the equivalent position as the second contact element such that the cylindrical power of the lens is removed and the spherical power of the lens is inverted relative to the scenario of Figure 11 ;

[0046] Figure 14 shows a schematic view of a third embodiment of an optical assembly comprising a liquid lens with an adaptable shape, the optical assembly having first and second contact elements that are movable in a direction parallel to the optical axis and having a pump driven actuator; Figure 15 is a schematic view of the third embodiment of Figure 14 wherein the pump has been used to transfer liquid into the lens so as to exert an outward pressure on the membrane and the first and second contact elements, such as to move the membrane outwardly to provide spherical power without cylindrical power;

[0047] Figure 16 shows the same arrangement as Figure 15, wherein the first and second locking elements are locked in the same position as in Figure 15 and the pump has been used to transfer liquid out of the lens so as to exert an inward pressure on the membrane and the first and second elements, such as to move the membrane inwardly to provide negative spherical power without cylindrical power

[0048] Figure 17 shows the same arrangement as Figure 16, wherein the first and second contact elements have moved in the second direction to the same position as shown in Figure 15, but wherein the pump is in the position of Figure 16 such as to provide increased spherical power relative to Figure 15;

[0049] Figure 18 shows the third embodiment in a scenario with both spherical and cylindrical power;

[0050] Figure 19 shows the arrangement of Figure 18 with the pump having provided inward pressure so as to increase the spherical power element compared with that shown in Figure 18;

[0051] Figure 20 shows the arrangement of Figure 19 with the pump having provided an outward pressure so as to invert the spherical power of the lens relative to Figure 18 whilst retaining cylindrical power;

[0052] Figure 21 shows a simplified three-dimensional cutaway view of a possible implementation of an intermediate assembly for use between an actuator and first send second contact element;

[0053] Figure 22 shows a two-dimensional cross sectional view of a possible implementation of an intermediate assembly for use between an actuator and first send second contact element, shown in a first position;

[0054] Figure 23 shows a two-dimensional cross sectional view of a possible implementation of an intermediate assembly for use between an actuator and first send second contact element, shown in a second position.

[0055] Figure 24 shows a two-dimensional cross sectional view of a possible implementation of an intermediate assembly for use between an actuator and first send second contact element, shown in a third position.

[0056] Figure 25 shows a two-dimensional cross sectional view of a possible implementation of an intermediate assembly for use between an actuator and first send second contact element, shown in a fourth position.

[0057] Figure 26 provides a plan view of an optical assembly showing an arrangement of an actuator assembly relative to the optical element;

[0058] Figure 27 shows a simplified cross-section of the optical assembly 10 of Figure 26, taken along the line A-A in a plane parallel to the first axis A;

[0059] Figure 28 shows the same cross-section illustrated in Figure 27, illustrating how a shape of the second lens surface 11 might be adapted.

[0060] Detailed description

[0061] First embodiment

[0062] Figure 1 shows a schematic view of a first embodiment of an optical assembly 100 comprising an optical element 110 having an adaptable shape. The optical element 110 may comprise a membrane 111 having an adaptable shape. The optical element 110 may comprise a liquid lens 110. The optical element 110 may comprise a gel lens 110. The optical element 110 may comprise any fluid lens 110. The optical element 110 may comprise a deformable mirror.

[0063] The first embodiment of the optical assembly 100 is shown in Figures 2 to 9, in various different operational positions. The optical assembly 100 comprises a support structure 120. Movement of elements of the optical assembly 100 may be defined relative to the support structure 120. A first axis, Z, is defined relative to the support structure 120.

[0064] The optical assembly 100 comprises a plurality of transmission assemblies, including at least a first transmission assembly 130 and a second transmission assembly 140. The first transmission assembly 130 and the second transmission assembly 140 may be a subset of a larger number of transmission assemblies located around a periphery of the lens 110. The transmission assemblies may be used to define the shape of the lens 110.

[0065] The optical assembly 100 comprises an actuator assembly 150 configured to exert a force on both the first transmission assembly 130 and the second transmission assembly 140. The actuator assembly 150 comprises an actuator 152 and an intermediate portion 155 having a first part 154 and a second part 156.

[0066] In this way, the first and second transmission assemblies 130, 140 may be driven by the same actuator 152. In arrangements with further transmission assemblies in addition to the first and second transmission assemblies 130, 140, the number of actuators 152 may be less than the number of transmission assemblies 130, 140. There may be only a single actuator 152 for the plurality of transmission assemblies 130, 140. There may be only a single actuator 152 for all of the transmission assemblies 130, 140 in the optical assembly.

[0067] The first transmission assembly 130 comprises a first contact element 132. The first contact element 132 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The first contact element 132 is in contact with the membrane 111 at a first location 112. In this way, movement of the first contact element 132 moves the membrane 111 at the first location 112. Thus, the first contact element 132 influences the adaptable shape of the membrane 111 at the first location 112. The membrane 111 and the first contact element 132 may be configured to retain mutual contact at the first location 112 such that they always move together. In this way, the membrane 111 moves with the first contact element 132 even when not assisted by tension or gravity.

[0068] The first transmission assembly 130 further comprises a first locking element 134 having a brake state 138 (shown, for example, in Figure 1) and having a transmission state 136 (shown, for example, in Figure 2).

[0069] In the transmission state 136 of the first transmission assembly 130, the first locking element 134 enables movement of the first contact element 132 relative to the support structure 120. In this way, when the first part 154 of the intermediate portion 155 is engaged with the first contact element 132 via the first locking element 134, movement of the first part 154 of the intermediate portion 155 effects movement of the first contact element 132. This in turn effects movement of the membrane 111 at the first location 112.

[0070] In the brake state 138 of the first transmission assembly 130, the first locking element 134 prevents movement of the first contact element 132 relative to the support structure 120. In this way, movement of the first part 154 of the intermediate portion 155 does not effect movement of the first contact element 132. Thus, movement of the first part 154 of the intermediate portion 155 does not effect movement of the membrane 111 in the region of the first location 112.

[0071] In a corresponding way, the second transmission assembly 140 comprises a second contact element 142. The second contact element 142 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The second contact element 142 is in contact with the membrane 111 at a second location 114. I n this way, movement of the second contact element 142 moves the membrane 111 at the second location 114. Thus, the second contact element 142 influences the adaptable shape of the membrane 111 at the second location 114. The membrane 111 and the second contact element 142 may be configured to retain mutual contact at the second location 114 such that they always move together. In this way, the membrane 111 moves with the first contact element 132 even when not assisted by tension or gravity.

[0072] The second transmission assembly 140 further comprises a second locking element 144 having a brake state 148 (shown, for example, in Figure 1) and having a transmission state 146 (shown, for example, in Figure 2).

[0073] In the transmission state 146 of the second transmission assembly 140, the second locking element 144 enables movement of the second contact element 142 relative to the support structure 120. In this way, when the second part 156 of the intermediate portion 155 is engaged with the second contact element 142 via the second locking element 144, movement of the second part 156 of the intermediate portion 155 effects movement of the second contact element 142. This in turn effects movement of the membrane 111 in the region of the second location 114.

[0074] In the brake state 148 of the second transmission assembly 140, the second locking element 144 prevents movement of the second contact element 142 relative to the support structure 120. In this way, movement of the second part 156 of the intermediate portion 155 does not effect movement of the second contact element 142. Thus, movement of the second part 156 of the intermediate portion 155 does not effect movement of the membrane 111 in the region of the second location 114.

[0075] If the first locking element 134 is in its transmission state 136 and the second locking element 144 in its brake state 148, a force exerted by the actuator assembly 150 results in movement of the first contact element 132 without movement of the second contact element 142. If the first locking element 134 is in its brake state 138 and the second locking element 144 is in its transmission state 146, the force exerted by the actuator assembly 150 results in movement of the second contact element 142 without movement of the first contact element 132.

[0076] In this way, a single actuator 152 may be used to alter different parts of the lens 110 at different times (or at the same time), in order to achieve multiple adaptations to the shape of the lens 110 using only one actuator 152.

[0077] Once the shape of the membrane 111 at the first location 112 has been adapted by the actuator assembly 150 to its desired position, the position of the membrane 111 at the first location 112 may be fixed using the brake state 138 of the first locking element 134. The actuator 152 may then be used to move the membrane 111 at the second location 114. Once the desired position of the membrane 111 at the second location 114 has been achieved, the position of the membrane 111 at the second location 114 may be fixed using the brake state 148 of the second locking element 144.

[0078] Figure 1 shows the first locking element 134 in its brake state 138 and the second locking element 144 in its brake state 148. In Figure 2, the first locking element 134 is shown in its transmission state 136 and the second locking element 144 is shown in the transmission state 146.

[0079] With both the first locking element 134 and the second locking element 144 still in their transmission states 136, 146, Figure 3 shows both the first part 154 of the intermediate portion 155 and the second part 156 of the intermediate portion 155 having moved an equal distance parallel to the axis Z in a downward direction in the orientation of the figure. This results in the first contact element 132 and the second contact element 142 having moved correspondingly downwards which in turn results in the membrane 111 having moved correspondingly downwards at both the first location 112 and the second location 114. Thus, the membrane 111 has a curvature which is symmetrical about the Z axis in the cross sectional view of Figure 3. Thus, the optical element 110 has a change in spherical power.

[0080] Figure 4 shows the first locking element having moved to its brake state 138 whilst the second locking element 144 remains in its transmission state 146.

[0081] Figure 5 shows the second part 156 of the intermediate portion 155 having moved upwards parallel to the axis Z in the orientation of the figure, which results in the second contact element 142 having moved correspondingly upwards which in turn results in the membrane having moved correspondingly upwards at the second location 114. However, the first locking element 134 being in the brake state, there is no change to the position of the first contact element 132 and therefore no change to the position of the membrane at the first location 112.

[0082] Consequently, the membrane 111 adopts an asymmetrical shape. Thus, this approach can be deployed to effect a change in cylindrical power of the optical element 110.

[0083] Figure 6 shows the same position of the membrane 111 as in Figure 5, but now both the first locking element 134 and the second locking element 144 are in their brake states 138, 148. Figure 7 shows the same position of the membrane 111 as in Figures 5 and 6, but now both the first locking element 134 and the second locking element 144 are in their transmission states 136, 146.

[0084] Figure 8 shows, with both the first locking element 134 and the second locking element 144 in their transmission states 136, 146, both the first contact element 132 and the second contact element 142 having been moved downwards by the intermediate portion 155 an equal distance parallel to the axis Z relative to their positions in Figure 7. In this way, the membrane 111 retains its asymmetry (thus retaining its cylindrical power) whilst having increased spherical power.

[0085] Figure 9 shows both the first contact element 132 and the second contact element 142 unmoved relative to Figure 8, but with the first locking element 134 and the second locking element 144 in their brake states 138, 148. In this way, the intermediate portion 155 may be moved elsewhere (e.g. out of the plane of the cross section of Figure 9) in order to influence positions of other (e.g. third and subsequent contact elements) whilst retaining the positions of the first and second contact elements 132, 142.

[0086] For example, since the intermediate portion 155 is disconnected from the first and second contact elements 132, 142, the first and second parts 154, 156 of the intermediate portion 155 may move vertically upwards to locations adjacent to the first and second contact elements 132, 142 without influencing the positions of the first and second contact elements 132, 142.

[0087] It may undesirable for the first locking element 134 to be in neither its brake state 138 nor its transmission state 136. Similarly, it may be undesirable for the second locking element 144 to be in neither its brake state 148 nor its transmission state 146. This is because the position of the membrane 111 may be difficult to control in such circumstances. In order to avoid such scenarios, it may be that a transition between the brake state 138 and the transmission state 136 of the first locking element 134 involves an overlap state in which the first locking element 134 is in both its brake state 138 and its transmission state 136 simultaneously. Correspondingly, it may be that a transition between the brake state 148 and the transmission state 146 of the second locking element 144 involves an overlap state in which the second locking element 144 is in both its brake state 148 and its transmission state 146 simultaneously. Alternatively, it may be that the first locking element 134 is bistable between its brake state 138 and its transmission state 136 without an overlap state. Similarly, it may be that the second locking element 144 is bistable between its brake state 148 and its transmission state 146 without an overlap state.

[0088] In some embodiments, an actuator assembly 150 may be able to provide sufficient force to the first and second transmission assemblies 130, 140 to move the membrane 111 to the desired position in all scenarios. However, such an actuator assembly 150 may be too large and / or use too much power.

[0089] The reasons why the forces required to move the edge of the optical element vary from actuation point to actuation point can be due to the spacing of the actuation points, the shape of the optical element, the position of the optical centre relative to the periphery of the lens and the desired optical shape of the optical element. For example, a cylindrical element of distortion on top of a spherical distortion will increase the force required at some points while reducing the force at other points. In a desired optical configuration, different actuation points may experience forces or component forces in either direction along the z-axis (parallel to the optical axis).

[0090] This problem may be solved by moving other actuation points to a position that reduces the force required to move the first actuation point (which needs to be moved) to the required position. For example, by reducing the pressure in the fluid and / or reducing the local distortion of the component which extends between the actuation points when the first actuation point is in the desired location. The first actuation point is then moved to the desired position and the brake element is active. The other actuation points are then moved to their desired positions. In some embodiments, after positioning the first actuation point in the desired position, the other actuation points may not be driven directly to their final desired positions, but may be further positioned to assist subsequent actuation points to achieve their desired positions.

[0091] In an example embodiment, this problem may be solved by moving the first and second transmission assemblies 130, 140 in a specific manner and / or order to minimize the power required to move the membrane 111 to the desired position. In this way, the actuator assembly 150 can be made smaller and / or require less power. Some examples of the manner in which the first and second transmission assemblies 130, 140 are moved to minimized the power requirements are set out below.

[0092] In a first example, the actuator assembly 150 may be unable to provide sufficient force to the first transmission assembly 130 to move the first contact element 132 relative to the support structure 120 as required. The first transmission assembly 130 may be in a brake state 138, in which the first locking element 134 prevents movement of the first contact element 132 relative to the support structure 120. The second transmission assembly 140 may be in a transmission state 146, in which the second locking element 144 enable movement of the second contact element 142 relative to the support structure 120. In this way, when the second part 156 of the intermediate portion 155 is engaged with the second contact element 142 via the second locking element 144, movement of the second part 156 of the intermediate portion 155 effects movement of the second contact element 142. This in turn effects movement of the membrane 111 in the region of the second location 114. In this first example, the second contact element 142 is moved to an intermediate position which reduces the force required to move the first contact element 132. The intermediate position of the second contact element 142 may not be the desired position of the second contact element 142.

[0093] When the second contact element 142 is in the intermediate position, the second transmission assembly 140 is put into the brake state 148 to hold the second contact element 142 in the intermediate position relative to the support structure 120.

[0094] The first transmission assembly 130 is put into a transmission state 136 in which the first locking element 134 enables movement of the first contact element 132 relative to the support structure 120. In this way, when the first part 154 of the intermediate portion 155 is engaged with the first contact element 132 via the first locking element 134, movement of the first part 154 of the intermediate portion 155 effects movement of the first contact element 132. This in turn effects movement of the membrane 111 at the first location 112. As the second contact element 142 has been moved to the intermediate position which reduces the force required to move the first contact element 132, the actuator assembly 150 may now be able to provide enough force to the first transmission assembly 130 to move the first contact element 132 relative to the support structure 120 as required.

[0095] Once the first contact element 132 is in the desired position, the first transmission assembly 130 is put back into the brake state 138.

[0096] The second transmission assembly 140 is then put back int the transmission state 146, moved from the intermediate position to the desired position, and then put back into the brake state 148 to hold the second contact element 142 at the desired position.

[0097] When in the brake state 138 the transmission assemblies 130, 140 may be capable of resisting forces that the actuator is no able to actuate against.

[0098] In this way, if when in the desired optical element configuration the actuator actuating a first actuation point experiences a force that is greater than the force it can drive against, then the first actuation point can be positioned in the desired location by moving the other actuation points around the edge of the optical element so as to reduce the force required to move the first actuation point to the desired position. The actuator can be then used to move the first actuation point to the desired position and the other actuators can then be moved to their desired position.

[0099] The above set out example may be applied to an optical assembly in which the actuator assembly 150 configured to exert a force on both the first transmission assembly 130 and the second transmission assembly 140 comprises an actuator 152 and an intermediate portion 155 having a first part 154 and a second part 156. In arrangements with further transmission assemblies in addition to the first and second transmission assemblies 130, 140, the number of actuators 152 may be less than the number of transmission assemblies 130, 140. There may be only a single actuator 152 for the plurality of transmission assemblies 130, 140. There may be only a single actuator 152 for all of the transmission assemblies 130, 140 in the optical assembly.

[0100] Alternatively, it may be applied to an optical assembly in which the actuator assembly 150 configured to exert a force on both the first transmission assembly 130 and the second transmission assembly 140 comprises more than one actuator 152. In arrangements with further transmission assemblies in addition to the first and second transmission assemblies 130, 140, the number of actuators 152 may be less than or equal to the number of transmission assemblies 130, 140. There may be a single actuator 152 for each of the plurality of transmission assemblies 130, 140, and / or some transmission assemblies 130, 140 may share a single actuator 153.

[0101] Alternatively, it may be applied to an optical assembly in which the actuator assembly 150 configured to exert a force on both the first transmission assembly 130 and the second transmission assembly 140 comprises a first actuator 152 and a second actuator 152, wherein the first actuator 152 exerts a force on the first transmission assembly 130 and the second actuator 152 exerts a force on the second transmission assembly 140. The first actuator 152 may comprise a first part 154 and the second actuator 152 may comprise a second part 156.

[0102] In an example in which the actuator assembly 150 comprises a first actuator 152 and a second actuator 152. In the transmission state 136 of the first transmission assembly 130, the first locking element 134 enables movement of the first contact element 132 relative to the support structure 120. In this way, when the first part 154 of the first actuator is engaged with the first contact element 132 via the first locking element 134, movement of the first part 154 effects movement of the first contact element 132. This in turn effects movement of the membrane 111 at the first location.

[0103] In the brake state 138 of the first transmission assembly 130, the first locking element 134 prevents movement of the first contact element 132 relative to the support structure 120. In this way, movement of the first part 154 does not effect movement of the first contact element 132. Thus, movement of the first part 154 does not effect movement of the membrane 111 in the region of the first location 112.

[0104] In a corresponding way, in the transmission state 146 of the second transmission assembly 140, the second locking element 144 enables movement of the second contact element 142 relative to the support structure 120. In this way, when the second part 156 is engaged with the second contact element 142 via the second locking element 144, movement of the second part 156 effects movement of the second contact element 142. This in turn effects movement of the membrane 111 in the region of the second location 114.

[0105] In the brake state 148 of the second transmission assembly 140, the second locking element 144 prevents movement of the second contact element 142 relative to the support structure 120. In this way, movement of the second part 156 does not effect movement of the second contact element 142. Thus, movement of the second part 156 does not effect movement of the membrane 111 in the region of the second location 114.

[0106] In this way, a two actuators 152 may be used to alter different parts of the lens 110 at different times (or at the same time), in order to achieve multiple adaptations to the shape of the lens 110.

[0107] Second embodiment

[0108] Figures 10 to 13 show schematic views of a second embodiment of an optical assembly 200 comprising an optical element 110 having an adaptable shape, in various different operational positions. Features of the second embodiment of the optical assembly 200 that correspond with those of the first embodiment of the optical assembly 100 have been provided with the same reference numerals.

[0109] The optical assembly 200 comprises an optical element 110 having an adaptable shape. The optical element 110 may comprise a membrane 111 having an adaptable shape. The optical element 110 may comprise a liquid lens 110. The optical element 110 may comprise a gel lens 110. The optical element 110 may comprise any fluid lens 110.

[0110] The optical assembly 200 comprises a support structure 120. Movement of elements of the optical assembly 200 may be defined relative to the support structure 120. A first axis, Z, is defined relative to the support structure 120.

[0111] The optical assembly 200 comprises a plurality of transmission assemblies, including at least a first transmission assembly 130 and a second transmission assembly 140.

[0112] The optical assembly 200 comprises an actuator assembly 150 configured to exert a force on both the first transmission assembly 130 and the second transmission assembly 140. The actuator assembly 150 comprises an actuator 152 and an intermediate portion 155 having a first part 154 and a second part 156. In this way, the first and second transmission assemblies 130, 140 may be driven by the same actuator 152. In arrangements with further transmission assemblies in addition to the first and second transmission assemblies 130, 140, the number of actuators 152 may be less than the number of transmission assemblies 130, 140. There may be only a single actuator 152 for the plurality of transmission assemblies 130, 140. There may be only a single actuator 152 for all of the transmission assemblies 130, 140 in the optical assembly.

[0113] The first transmission assembly 130 comprises a first contact element 132. The first contact element 132 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The first contact element 132 is in contact with the membrane 111 at a first location 112. In this way, movement of the first contact element 132 moves the membrane 111 at the first location 112. Thus, the first contact element 132 influences the adaptable shape of the membrane 111 at the first location 112.

[0114] The first transmission assembly 130 further comprises a first locking element 134 having a brake state 138 (shown, for example, in Figure 10) and having a transmission state 136 (shown, for example, in Figure 11).

[0115] The first transmission assembly 130 further comprises a first compliant member 162 that extends between the first part 154 of the intermediate portion 155 and the first contact element 132. The first compliant member 162 limits relative movement between the first part 154 of the intermediate portion 155 and the first contact element 132 and provides a degree of biasing towards a neutral position of the first contact element 132 relative to the first part 154 of the intermediate portion 155. The first compliant member 162 may comprise a spring, a flexure, or any other element with an appropriate degree of compliance.

[0116] In the transmission state 136 of the first transmission assembly 130, the first locking element 134 enables movement of the first contact element 132 relative to the support structure 120. In this way, movement of the first part 154 of the intermediate portion 155 effects movement of the first contact element 132. This in turn effects movement of the membrane 111 at the first location 112.

[0117] In the brake state 138 of the first transmission assembly 130, the first locking element 134 prevents movement of the first contact element 132 relative to the support structure 120. In this way, movement of the first part 154 of the intermediate portion 155 does not effect movement of the first contact element 132. Instead, force exerted by the first part 154 of the intermediate portion 155 is absorbed by the first compliant member 162. Thus, movement of the first part 154 of the intermediate portion 155 does not effect movement of the membrane 111 in the region of the first location 112.

[0118] The first compliant member 162 is sufficiently stiff to drive the first contact element 132 when the first locking element 134 is in the transmission state 136 and sufficiently flexible to accommodate movement of the first part 154 of the intermediate portion 155 without movement of the first contact element when the first locking element 134 is in the brake state 138.

[0119] In a corresponding way, the second transmission assembly 140 comprises a second contact element 142. The second contact element 142 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The second contact element 142 is in contact with the membrane 111 at a second location 114. In this way, movement of the second contact element 142 moves the membrane 111 at the second location 114. Thus, the second contact element 142 influences the adaptable shape of the membrane 111 at the second location 114.

[0120] The second transmission assembly 140 further comprises a second locking element 144 having a brake state 148 (shown, for example, in Figure 1) and having a transmission state 146 (shown, for example, in Figure 2). The second transmission assembly 140 further comprises a second compliant member 164 that extends between the second part 156 of the intermediate portion 155 and the second contact element 142. The second compliant member 164 limits relative movement between the second part 156 of the intermediate portion 155 and the second contact element 142 and provides a degree of biasing towards a neutral position of the second contact element 142 relative to the second part 156 of the intermediate portion 155. The second compliant member 164 may comprise a spring, a flexure, or any other element with an appropriate degree of compliance.

[0121] In the transmission state 146 of the second transmission assembly 140, the second locking element 144 enables movement of the second contact element 142 relative to the support structure 120. In this way, movement of the first part 154 of the intermediate portion 155 effects movement of the second contact element 142. This in turn effects movement of the membrane 111 in the region of the second location 114.

[0122] In the brake state 148 of the second transmission assembly 140, the second locking element 144 prevents movement of the second contact element 142 relative to the support structure 120. In this way, movement of the second part 156 of the intermediate portion 155 does not effect movement of the second contact element 142. Instead, force exerted by the second part 156 of the intermediate portion 155 is absorbed by the second compliant member 164. Thus, movement of the second part 156 of the intermediate portion 155 does not effect movement of the membrane 111 in the region of the second location 114.

[0123] The second compliant member 164 is be sufficiently stiff to drive the second contact element 142 when the second locking element 144 is in the transmission state 146 and sufficiently flexible to accommodate movement of the second part 156 of the intermediate portion 155 when the second locking element 144 is in the brake state 148.

[0124] If the first locking element 134 is in its transmission state 136 and the second locking element 144 in its brake state 148, a force exerted by the actuator assembly 150 results in movement of the first contact element 132 without movement of the second contact element 142. If the first locking element 134 is in its brake state 138 and the second locking element 144 is in its transmission state 146, the force exerted by the actuator assembly 150 results in movement of the second contact element 142 without movement of the first contact element 132.

[0125] In this way, a single actuator 152 may be used to alter different parts of the lens 110 at different times (or at the same time), in order to achieve multiple adaptations to the shape of the lens 110 using only one actuator 152.

[0126] Once the shape of the membrane 111 at the first location 112 has been adapted by the actuator assembly 150 to its desired position, the position of the membrane 111 at the first location 112 may be fixed using the brake state 138 of the first locking element 134. The actuator 152 may then be used to move the membrane 111 at the second location 114. Once the desired position of the membrane 111 at the second location 114 has been achieved, the position of the membrane 111 at the second location 114 may be fixed using the brake state 148 of the second locking element 144.

[0127] It may undesirable for the first locking element 134 to be in neither its brake state 138 nor its transmission state 136. Similarly, it may be undesirable for the second locking element 144 to be in neither its brake state 148 nor its transmission state 146. This is because the position of the membrane 111 may be difficult to control in such circumstances. In order to avoid this, it may be that the first locking element 134 is bistable between its brake state 138 and its transmission state 136 without an overlap state.

[0128] Similarly, it may be that the second locking element 144 is bistable between its brake state 148 and its transmission state 146 without an overlap state. In some embodiments, an actuator assembly 150 may be able to provide sufficient force to the first and second transmission assemblies 130, 140 to move the membrane 111 to the desired position in all scenarios. However, such an actuator assembly 150 may be too large and / or use too much power. This problem may be solved in a similar way to that as set out in the first embodiment.

[0129] Third embodiment

[0130] Figures 14 to 20 show schematic views of a third embodiment of an optical assembly 300 comprising an optical element 110 having an adaptable shape, in various different operational positions. Features of the third embodiment of the optical assembly 300 that correspond with those of the first embodiment of the optical assembly 100 and the second embodiment of the optical assembly 200 have been provided with the same reference numerals.

[0131] The optical assembly 300 comprises an optical element 110 having an adaptable shape. The optical element 110 may comprise a membrane 111 having an adaptable shape. The optical element 110 comprises a liquid lens. The optical element 110 may comprise a gel lens 110. The optical element 110 may comprise any fluid lens 110.

[0132] The optical assembly 300 comprises a support structure 120. Movement of elements of the optical assembly 300 may be defined relative to the support structure 120. A first axis, Z, is defined relative to the support structure 120.

[0133] The optical assembly 300 comprises an actuator assembly 150. The actuator assembly 150 comprises an actuator 152 configured to drive a pump 151 by which liquid may be transferred into or out of the liquid lens 110. The pump 151 may comprise a pump element 153.

[0134] Thus, a pressure within the liquid lens 110 may be controlled by operating the pump 151. The pressure within the liquid lens has the effect of influencing the shape of the membrane 111. Using the pump 151 to pump in a first direction causes the membrane 111 to move in an outward direction while using the pump 151 in a second direction opposite the first direction causes the membrane 111 to move in an inward direction.

[0135] The optical assembly 300 comprises a plurality of transmission assemblies, including at least a first transmission assembly 130 and a second transmission assembly 140.

[0136] The first transmission assembly 130 comprises a first contact element 132. The first contact element 132 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The first contact element 132 is in contact with the membrane 111 at a first location 112.

[0137] While the first contact element 132 influences the position of the membrane at the first location 112, the first contact element 132 may not be the predominant cause of movement of the position of the membrane 111 at the first location 112. This is because, although some of the pressure resulting from the pump 151 may act on the first contact element 132, the pressure also acts on the membrane 111 directly. The membrane 111 and the first contact element 132 may be configured to retain mutual contact at the first location 112 such that they always move together. In this way, the membrane 111 moves with the first contact element 132 even when not assisted by tension or gravity. The first transmission assembly 130 further comprises a first locking element 134 having a brake state 138 (shown, for example, in Figure 14) and having a transmission state 136 (shown, for example, in Figure 17).

[0138] In the transmission state 136 of the first transmission assembly 130, the first locking element 134 enables movement of the first contact element 132 relative to the support structure 120. In this way, first contact element 132 influences the adaptable shape of the membrane 111 at the first location 112.

[0139] In the brake state 138 of the first transmission assembly 130, the first locking element 134 prevents movement of the first contact element 132 relative to the support structure 120. In this way, changing the pressure using the pump 151 does not affect the position of the membrane 111 at the first location 112.

[0140] In a corresponding way, the second transmission assembly 140 comprises a second contact element 142. The second contact element 142 is movable relative to the support structure 120 in a direction parallel to the first axis, Z. The second contact element 142 is in contact with the membrane 111 at a second location 114.

[0141] While the second contact element 142 influences the position of the membrane at the second location 114, the second contact element 142 may not be the predominant cause of movement of the position of the membrane 111 at the second location 114. This is because, although some of the pressure resulting from the pump 151 may act on the second contact element 142, the pressure also acts on the membrane 111 directly. The membrane 111 and the second contact element 142 may be configured to retain mutual contact at the second location 114 such that they always move together. In this way, the membrane 111 moves with the second contact element 142 even when not assisted by tension or gravity.

[0142] The second transmission assembly 140 further comprises a second locking element 144 having a brake state 148 (shown, for example, in Figure 14) and having a transmission state 146 (shown, for example, in Figure 17).

[0143] In the transmission state 146 of the second transmission assembly 140, the second locking element 144 enables movement of the second contact element 142 relative to the support structure 120. In this way, the second contact element 142 influences the adaptable shape of the membrane 111 at the second location 114.

[0144] In the brake state 148 of the second transmission assembly 140, the second locking element 144 prevents movement of the second contact element 142 relative to the support structure 120. In this way, changing the pressure using the pump 151 does not affect the position of the membrane 111 at the second location 114.

[0145] If the first locking element 134 is in its transmission state 136 and the second locking element 144 in its brake state 148, a force exerted by the actuator assembly 150 results in movement of the membrane 111 at the first location 112 and movement of the first contact element 132, but does not result in movement of the membrane 111 at the second location 114 or movement of the second contact element 142.

[0146] Conversely, if the first locking element 134 is in its brake state 138 and the second locking element 144 is in its transmission state 146, a force exerted by the actuator assembly 150 results in movement of the membrane 111 at the second location 114 and movement of the second contact element 142, but does not result in movement of the membrane 111 at the first location 112 or movement of the first contact element 132. In this way, a single actuator 152 may be used to alter different parts of the lens 110 at different times (or at the same time), in order to achieve multiple adaptations to the shape of the lens 110 using only one actuator 152.

[0147] Once the shape of the membrane 111 at the first location 112 has been adapted by the actuator assembly 150 to its desired position, the position of the membrane 111 at the first location 112 may be fixed using the brake state 138 of the first locking element 134. The actuator assembly 150 may then be used to move the membrane 111 at the second location 114. Once the desired position of the membrane 111 at the second location 114 has been achieved, the position of the membrane 111 at the second location 114 may be fixed using the brake state 148 of the second locking element 144.

[0148] An optional additional feature of the third embodiment (which is not shown in the Figures) is the inclusion of a valve in series with the pump.

[0149] It may undesirable for the first locking element 134 to be in neither its brake state 138 nor its transmission state 136. Similarly, it may be undesirable for the second locking element 144 to be in neither its brake state 148 nor its transmission state 146. This is because the position of the membrane 111 may be difficult to control in such circumstances. In order to avoid this, it may be that the first locking element 134 is bistable between its brake state 138 and its transmission state 136 without an overlap state. Similarly, it may be that the second locking element 144 is bistable between its brake state 148 and its transmission state 146 without an overlap state.

[0150] In some embodiments, an actuator assembly 150 may be able to provide sufficient force to the first and second transmission assemblies 130, 140 to move the membrane 111 to the desired position in all scenarios. However, such an actuator assembly 150 may be too large and / or use too much power. This problem may be solved in a similar way to that as set out in the first embodiment.

[0151] Position sensing

[0152] In any of the embodiments described above, each contact element may have an associated position sensor. When a contact element (such as a first contact element 132, or a second contact element 142) reaches the desired position as measured by the associated position sensor, the locking element associated with the contact element (such as the first locking element 134 or the second locking element 144 may change from its transmission state 136, 146 to its brake state 138, 148 so that the position of the membrane at that point is then fixed.

[0153] Actuator assembly

[0154] The disclosure is not limited to any particular type of actuator assembly 150 or any particular type of actuator 152. The actuator 152 may comprise one or more of: shape memory alloy (SMA), a voice coil motor (VCM) or any other appropriate actuator, for example one or more motors.

[0155] The actuator assembly 150 of the first embodiments and the actuator assembly 150 of the second embodiment make use of an intermediate portion 155 to transfer a force between the actuator 152 and the first contact element 132 and between the actuator 152 and the second contact element 142. The present disclosure is also not limited to any particular type of intermediate portion 155.

[0156] In some arrangements, the actuator 152 may act to move in a direction within a primary plane orthogonal to the first axis, Z, to trigger movement of the first contact element 132 and / or the second contact element 142 in a direction parallel to the first axis, Z, via the intermediate portion 155. This may result from the intermediate portion 155 comprising one or more surfaces at an acute, nonzero angle with respect to the primary plane. Thus, movement of the intermediate portion 155 in the primary plane may result in that part of the intermediate portion 155 which is engageable with the first contact element 132 or the second contact element 142 when in the transmission state 136, 146 moving in a direction parallel to the first axis, Z.

[0157] What follows are examples of a possible implementation of an intermediate portion 155 which may be particularly compatible with the first embodiment 100 shown in Figures 1 to 9.

[0158] Figure 21 shows a three-dimensional cutaway view of a first example of an intermediate portion 155 which is a component of an intermediate assembly that further comprises a first additional portion 157. The intermediate portion 155 and the first additional portion 157 each comprise a plurality of mutually facing surfaces at an acute, non-zero angle with respect to the primary plane. Movement of the intermediate portion 155 relative to the first additional portion 157 in the primary plane the mutually facing surfaces to slide with respect to one another. This causes movement of the intermediate portion 155 in the direction of the first axis, Z. In this way, the intermediate portion 155 can be used to drive the first contact element 132 and the second contact element 142.

[0159] A second example of an intermediate portion 155 is shown in the two-dimensional cross sectional views of Figures 21 to 25. In the second example, the intermediate portion 155 may be a component of an intermediate assembly which further comprises not only a first additional portion 157 but also a second additional portions 158 and a third additional portions 159.

[0160] Figure 22 shows the intermediate portion 155 and first, second and third additional portions 157, 158, 159 in a neutral position.

[0161] Figure 23 shows how relative movement between third additional portion 159 and support structure 120 is deployed to move both the first and the second parts 154, 156 of the intermediate portion 155 the same distance in the Z direction.

[0162] Figure 24 shows how relative movement between first additional portion 157 and the intermediate portion 155 is deployed to move first and second parts 154, 156 of the intermediate portion 155 different distances in the Z direction.

[0163] Figure 25 shows how, having started in the configuration of Figure 24, relative movement between third additional portion 159 and the intermediate portion 155 is deployed to move both the first and the second parts 154, 156 of the intermediate portion 155 the same distance in the Z direction, whilst retaining the relative offset between the first and the second parts 154, 156 of the intermediate portion 155 achieved in Figure 24.

[0164] Second additional portion 158 may act as an interface between first and third additional portions 157, 159.

[0165] In this way, the skilled person will appreciate one possible method for triggering movement of the intermediate portion 155 in order to move the first and second contact elements 132, 142 so as to manipulate the shape of the membrane 111 at the first and second locations 112, 114.

[0166] The first and second examples shown in Figures 21 to 25 may be deployed in a scenario where there are considerably more contact elements than only the first contact element 132 and the second contact element 142. The intermediate portion 155 may be movable in a first degree of freedom relative to the support structure 120 in the primary plane. For example, the intermediate portion 155 may be translatable in a first degree of freedom in the primary plane. In another example, the intermediate portion 155 may be rotatable in the primary plane.

[0167] The intermediate portion 155 may be movable in one degree of freedom relative to the support structure 120 in the primary plane. The intermediate portion 155 may be movable in more than one degree of freedom relative to the support structure 120 in the primary plane. In certain embodiments, the intermediate portion 155 may be movable in two degrees of freedom relative to the support structure 120 in the primary plane. For example, the intermediate portion 155 may be translatable in the primary plane in two degrees of freedom, or the intermediate portion 155 may be translatable in the primary plane in one degree of freedom and may be rotatable in the primary plane. In certain embodiments, the intermediate portion 155 may be movable in three degrees of freedom relative to the support structure 120 in the primary plane. For example, the intermediate portion 155 may be translatable in the primary plane in two degrees of freedom and may be rotatable in the primary plane.

[0168] Where the intermediate portion 155 is a component of an intermediate assembly which further comprises first, second and third additional portions 157, 158, 159, one or more of the first, second and third additional portions 157, 158, 159 may be movable relative to the support structure in a secondary plane. The secondary plane may be perpendicular to the first axis, Z, and may be separated from the primary plane along the first axis, Z. The intermediate portion 155 may be movable in a first degree of freedom relative to the support structure in the primary plane, and one or more of the first, second and third additional portions 157, 158, 159 may be movable in a second degree of freedom relative to the support structure 120 in the secondary plane. One or more of the first, second and third additional portions 157, 158, 159 may comprise a plurality of surfaces at an acute, non-zero angle with respect to the primary plane. The first degree of freedom and the second degree of freedom may be different. Movement parallel to the secondary plane of the plurality of surfaces at an acute, non-zero angle of the one or more of the first, second and third additional portions 157, 158, 159 may adapt the shape of the optical element.

[0169] In the context of surfaces of the one or more of the first, second and third additional portions 157, 158, 159 extending out of the secondary plane may mean any structure or part of the one or more of the first, second and third additional portions 157, 158, 159 that is not parallel to the secondary plane.

[0170] In the context of movement parallel to the secondary plane of the of the one or more of the first, second and third additional portions 157, 158, 159, movement parallel to the secondary plane may be any movement that has a component parallel to the secondary plane.

[0171] In other examples, the intermediate portion may be driven to move along a direction parallel to the primary axis. Optionally, the intermediate portion may be constrained (e.g. by a bearing arrangement) to move along a direction parallel to the primary axis only and prevented from moving in other degrees of freedom. The intermediate portion may take any suitable form but may comprise an annulus, for example. Any suitable actuator may be used to drive movement of the intermediate portion along the direction parallel to the primary axis. The actuator may comprise one or more SMA elements and examples of such actuators are disclosed in, for example: WO2017 / 134456A1 and WO2019 / 243842A1 , both of which are incorporated herein in their entireties. Alternatively or additionally, any other actuator may be used. For example, one or more voice coil motors (VCMs) or other motors may be used.

[0172] Lens Figure 26 illustrates an optical assembly 10 showing an arrangement of the actuator assembly 150 relative to the optical element 110, wherein the actuator assembly 150 is arranged around an edge portion of the optical element 110. The hashed area 13 indicates an overlap between the optical element 110 and the actuator assembly 150. The arrangement shown is exemplary, and the arrangement of the actuator assembly 150 relative to the optical element 110 may differ. For example, the degree of overlap between the optical element 110 and the actuator assembly 150 may differ such that the actuator assembly 150 extends beyond an edge of the optical element 110 when viewed along the first axis, or the optical element 110 extends beyond an edge of the actuator assembly 150 when viewed along the first axis.

[0173] Figure 27 shows a simplified cross-section of the optical assembly 10 of Figure 26, taken along the line A-A in a plane parallel to the first axis A. In the example shown, the optical element 110 comprises a lens comprising a curved first lens surface 14. The first lens surface 14 may be rigid, such that the shape of the first lens surface 14 is not adaptable. The optical element 110 may further comprise a second lens surface 11 that has an adaptable shape. The second lens surface 11 is shown in Figure 27 as being planar and parallel to the primary plane. The shape of the second lens surface 11 may be adaptable such that the second lens surface 11 is not planar. The second lens surface 11 may comprise the membrane 111 described previously.

[0174] Figure 28 shows the same cross-section illustrated in Figure 27, illustrating how a shape of the second lens surface 11 might be adapted. Two examples of a shape of the second lens surface 1 T, 11” are shown, wherein the shape the second lens surface 1 T, 11” has been adapted such that the second lens surface 1 T, 11” is not planar. In a first example, the second lens surface 1 T is shown as being curved away from first lens surface 14. In a second example, the second lens surface 11” is shown as being curved towards the first lens surface 14. The amount by which the shape of the second lens surface 11 is adapted may vary. The second lens surface 11 may be adapted to form different shapes.

[0175] The second lens surface 11 is shown as being either planar or having rotational symmetry about the first axis. The second lens surface 11 may have a different shape to those illustrated, and may not have rotational symmetry about the first axis.

[0176] Figures 27 and 28 show the optical element 110 as comprising lens, comprising a first lens surface 11 and a second lens surface 14, wherein the shape of the second lens surface 11 is adaptable. In other examples, the first lens surface 14 may have an adaptable shape and the second lens surface 11 may be rigid, or the first lens surface 14 and the second lens surface 11 may each have an adaptable shape. The optical element 110 illustrated in Figures 27 and 28 may comprise a liquid or gel lens, wherein a cavity between the first lens surface 14 and the second lens surface 11 contains a liquid or a gel. In other examples, the optical element 110 may have a different structure. For example, the optical element 110 may comprise a sheet, such as a mirror, having an adaptable shape.

[0177] SMA

[0178] The above-described actuator assemblies comprise at least one SMA element. The term 'shape memory alloy (SMA) element’ may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and / or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA element’ may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and / or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

[0179] Other variations

[0180] It will be appreciated that there may be many other variations of the above-described examples.

[0181] For example, the first and second locking elements 134 and 144 have been illustrated and described as moving with the contact elements 132 and 142 when in their respective transmission states. In some examples, the locking elements 134 and 144 may be fixed relative to the support structure in that they are not arranged to move with the respective contact elements 132 and 142.

[0182] Taking the first locking element 134 as an example, the first locking element 134 may be configured to have a transmission state in which the first locking element is disengaged from the first contact element 132. In this state, the first contact element 132 is free to move relative to the support structure and is driven to move by the actuator 152 via the intermediate portion 155. In the brake state, the first locking element 134 is configured to engage with the first contact element 132, holding it still with the respect to the support structure as the intermediate portion 155 is driven to move relative to the support structure. The second locking element 142 may be arranged in an analogous way.

[0183] This type of arrangement may require the contact element to have a large enough extent in the relevant direction to facilitate the braking of the contact element at any position within a range of movement.

Claims

Claims1. An optical assembly comprising: an optical element having an adaptable shape; a support structure, wherein a first axis is defined relative to the support structure; a first transmission assembly; a second transmission assembly; an actuator assembly configured to exert a force on both the first transmission assembly and the second transmission assembly; wherein the first transmission assembly comprises: a first contact element in contact with the optical element at a first location so as to influence the adaptable shape of the optical element at the first location in a direction parallel to the first axis, the first contact element being movable relative to the support structure; and a first locking element having a transmission state in which the first locking element enables movement of the first contact element relative to the support structure, and a brake state in which the first locking element prevents movement of the first contact element relative to the support structure; and wherein the second transmission assembly comprises: a second contact element in contact with the optical element at a second location different from the first location so as to influence the adaptable shape of the optical element at the second location in a direction parallel to the first axis, the second contact element being movable relative to the support structure; and a second locking element having a transmission state in which the second locking element enables movement of the second contact element relative to the support structure, and a brake state in which the second locking element prevents movement of the second contact element relative to the support structure; such that with the first locking element in its transmission state and the second locking element in its brake state, the force exerted by the actuator assembly results in movement of the first contact element without movement of the second contact element; and such that with the first locking element in its brake state and the second locking element in its transmission state, the force exerted by the actuator assembly results in movement of the second contact element without movement of the first contact element.

2. The optical assembly of claim 1 wherein the actuator assembly comprises a shape memory alloy (SMA) element.

3. The optical assembly of claim 1 or claim 2 wherein the optical element comprises a membrane having an adaptable shape.

4. The optical assembly of any preceding claim wherein the optical element is a fluid lens.

5. The optical assembly of any preceding claim wherein the first contact element is restricted to moving in a direction parallel to the first axis and the second contact element is restricted to moving in a direction parallel to the first axis.

6. The optical assembly of any preceding claim wherein the first locking element is configured to transition between its transmission state and its brake state by movement in a direction perpendicular to the first axis and wherein the second locking element is configured to transition between its transmission state and its brake state by movement in a direction perpendicular to the first axis.

7. The optical assembly of any preceding claim wherein:in the brake state of the first locking element, the first contact element engages with the support structure to prevent relative movement between the first contact element and the support structure; and in the brake state of the second locking element, the second contact element engages with the support structure to prevent relative movement between the second contact element and the support structure.

8. The optical assembly of any preceding claim wherein: the first contact element is configured to move the optical element at the first location so as to influence the adaptable shape of the optical element at the first location; and wherein the second contact element is configured to move the optical element at the second location so as to influence the adaptable shape of the optical element at the second location.

9. The optical assembly of any preceding claim wherein the actuator assembly comprises an actuator and an intermediate portion between the actuator and the first and second transmission assemblies, wherein the intermediate portion is movable relative to the support structure and comprises a first part configured to drive the first contact element and a second part configured to drive the second contact element.

10. The optical assembly of claim 9 wherein the intermediate portion is movable in a primary plane orthogonal to the first axis.

11. The optical assembly of claim 10 wherein the intermediate portion comprises one or more surfaces, wherein each of the one or more surfaces is at an acute, non-zero angle with respect to the primary plane.

12. The optical assembly of any preceding claim wherein: in the transmission state of the first locking element, the first locking element is detached from the support structure; and in the transmission state of the second locking element, the second locking element is detached from the support structure.

13. The optical assembly of claim 9 or any claim dependent on claim 9 wherein: in the transmission state of the first locking element, the first locking element engages with the intermediate portion; and in the transmission state of the second locking element, the second locking element engages with the intermediate portion.

14. The optical assembly of claim 9 or any claim dependent on claim 9 wherein: the first locking element has an overlap state which occurs during a transition between the transmission state and the brake state, and during a transition between the brake state and the transmission state, wherein in the overlap state the first locking element engages with both the support structure and the intermediate portion; and the second locking element has an overlap state which occurs during a transition between the transmission state and the brake state, and during a transition between the brake state and the transmission state, wherein in the overlap state the second locking element engages with both the support structure and the intermediate portion.

15. The optical assembly of any of claims 1 to 13 wherein the first locking element is bistable between its brake state and its transmission state and the second locking element is bistable between its brake state and its transmission state.

16. The optical assembly of claim 9 or any claim dependent on claim 9 wherein:the first transmission assembly further comprises a first compliant member that extends between the first part of the intermediate portion and the first contact element; and the second transmission assembly further comprises a second compliant member that extends between the second part of the intermediate portion and the second contact element.

17. The optical assembly of claim 16 wherein: in the brake state of the first locking element, a force exerted by the first part of the intermediate portion is absorbed by the first compliant member; and in the brake state of the second locking element, a force exerted by the second part of the intermediate portion is absorbed by the second compliant member.

18. The optical assembly of claim 4 or any claim dependent on claim 4, wherein the actuator assembly comprises a pump configured to pump fluid into and out of the fluid lens.

19. The optical assembly of claim 18 wherein pressure exerted by fluid within the lens causes the shape of the optical element to adapt.

20. The optical assembly of claim 19 wherein the first contact element and the second contact element influence the manner in which the shape of the optical element adapts in response to pressure exerted by fluid within the lens.

21. A head-mounted device comprising an optical assembly according to any preceding claim.

22. A method of adapting a shape of an optical element of an optical assembly, the optical assembly comprising: the optical element having an adaptable shape; a support structure, wherein a first axis is defined relative to the support structure; a first transmission assembly; a second transmission assembly; an actuator assembly configured to exert a force on both the first transmission assembly and the second transmission assembly; wherein the first transmission assembly comprises: a first contact element in contact with the optical element at a first location so as to influence the adaptable shape of the optical element at the first location in a direction parallel to the first axis, the first contact element being movable relative to the support structure; and a first locking element having a transmission state in which the first locking element enables movement of the first contact element relative to the support structure, and a brake state in which the first locking element prevents movement of the first contact element relative to the support structure; and wherein the second transmission assembly comprises: a second contact element in contact with the optical element at a second location different from the first location so as to influence the adaptable shape of the optical element at the second location in a direction parallel to the first axis, the second contact element being movable relative to the support structure; and a second locking element having a transmission state in which the second locking element enables movement of the second contact element relative to the support structure, and a brake state in which the second locking element prevents movement of the second contact element relative to the support structure;wherein the method comprises: engaging the first locking element in its transmission state and the second locking element in its brake state, and exerting a force from the actuator to move the first contact element without causing movement of the second contact element; and engaging the first locking element in its brake state and the second locking element in its transmission state, and exerting a force from the actuator to move the second contact element without causing movement of the first contact element.

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