Variable Focusing Lens with SMA Actuator Array
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Solution Overview
Problem
Existing variable focusing power optical devices, such as liquid lenses, face challenges in achieving spherical or spherocylindrical optics, particularly for non-round lenses, where active control points are difficult to implement, leading to suboptimal optical performance, especially in regions like the nasal area.
Innovation Solution
The use of an array of co-acting shape memory alloy (SMA) wires to provide sufficient force and fine control over the lens shape, allowing long wires to be used within eyewear constraints and enabling active control at multiple points around the lens, including the nasal region, by arranging SMA wires orthogonally or obliquely to the z-axis and dividing them into sections for precise actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If discrete control points are used around the lens periphery, then the lens can be adjusted at specific locations, but active control in regions like the nasal area is insufficient leading to suboptimal optical performance
Solution Approach 1:
The lens periphery is divided into multiple discrete control points (at least three, preferably four or more) spaced around the periphery. Each control point has an associated actuator that can independently adjust the membrane position at that location. This segmentation allows targeted control of specific regions including nasal, temporal, superior and inferior areas, resolving the contradiction by providing both operational accessibility and optical precision through distributed control points.
2Manufacturing precision
If long SMA wires are used to provide sufficient force and fine control, then the lens shape can be precisely controlled, but the wires must be arranged orthogonally or obliquely to the z-axis increasing device complexity
Solution Approach 1:
The SMA wires are arranged orthogonally or obliquely to the z-axis (optical axis) rather than parallel to it. This dimensional reorientation allows long wires to extend radially or at angles from the lens periphery toward the center, providing sufficient leverage and control precision while accommodating the wires within the eyewear form factor. The wires can be positioned in the radial direction or at oblique angles, transforming the control geometry to achieve both precision and compactness.
3Manufacturing precision
If multiple actuators are placed around the lens periphery for fine control, then optical performance improves, but the number of components and device complexity increases
Solution Approach 1:
Different regions of the lens periphery are equipped with actuators based on their specific optical control requirements. The nasal region, temporal region, superior region and inferior region can each have actuators positioned to address local optical imperfections. This local quality approach ensures that optical precision is optimized where needed most, while the overall system complexity is managed by placing actuators only at strategically important locations rather than uniformly around the entire periphery.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the formation of desired three-dimensional shapes in non-round lenses, improving optical performance and user experience by allowing active control in previously uncontrolled regions, such as the nasal area, and allowing for smooth power adjustments in increments as small as 1/8 dioptres.
Implementation Method 1
SMAs (shape-memory alloys) are materials that can be made to undergo a solid state phase change from a Martensitic to austenitic crystal structure at an elevated temperature
Implementation Method 2
When in the Martensite phase, an SMA wire is typically in a 3% stretched form, such that on heating to the austenite phase the material 'remembers' its undeformed shape and contracts by approximately 3%
Implementation Method 3
a fluid-filled envelope, one wall of which is formed by an elastic membrane that is held under tension around its edge
Data Source
AI summary
An adjustable fluid-filled lens or mirror assembly 100 comprising a fluid-filled envelope and a supporting structure therefor; the fluid-filled envelope being constituted by a first wall that is formed of a distensible elastic membrane 15 having an exterior optical surface of variable focusing power, a second wall 18 that is spaced from the first wall on a z-axis, and a collapsible peripheral side wall 17 that extends between the first and second walls, and being filled with a substantially incompressible fluid 16; a membrane holding structure 14 that is attached to a peripheral edge of membrane 15 for holding the membrane under tension; and one or more selectively operable actuator assemblies r1, r2, r3 for moving one or more corresponding regions of the peripheral edge of the membrane on the z-axis towards and away from the second wall 18 for controlling the profile of the peripheral edge of the membrane; wherein the or each actuator assembly comprises a connecting member 91, 92, 93 that is attached to the membrane or membrane holding structure at a respective actuation point, a linear actuator 531, 532, 533 that is mounted to the supporting structure and a linkage 81, 82, 83 that is connected between the connecting member and an actuation point a1, a2, a3 on the linear actuator; wherein the linear actuator is a linear SMA actuator comprising an array of SMA wires 53 that are coupled together to work in parallel and which extend transversely of the z-axis, and the linkage is configured for converting linear motion of the actuation point of the SMA actuator in a direction transverse the z-axis to linear motion of the connecting member on the z-axis, thereby to move the corresponding region of the peripheral edge of the membrane 15 towards or away from the second wall 18.