SMA Wire Actuation for Camera Lens Movement
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Solution Overview
Problem
Miniature camera lenses require precise and compact actuation mechanisms for focusing and zooming, which is challenging due to the limited space and the inherent properties of shape memory alloy (SMA) materials, particularly in designing and manufacturing SMA actuators that can efficiently drive camera lens movement while maintaining image quality.
Innovation Solution
A camera lens actuation apparatus using SMA wire arranged at acute angles to the optical axis, coupled at a common point and extending in a V-shape, provides increased movement and force while minimizing the size of the apparatus, and employs a suspension system with resilient flexures to balance off-axis forces and resist tilting, allowing for compact and efficient design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SMA wire is arranged parallel to the optical axis, then the actuator structure is simple, but the degree of movement along the optical axis is insufficient
Solution Approach 1:
The SMA wire is arranged at an acute angle to the optical axis rather than parallel to it. This angular arrangement transforms the linear contraction of the SMA wire into a amplified displacement along the optical axis through geometric leverage, effectively converting a one-dimensional wire contraction into useful two-dimensional lens movement.
Solution Approach 2:
The actuation system uses multiple SMA wires arranged symmetrically at acute angles to the optical axis. This segmentation into multiple angled wires provides both the necessary movement amplification and force balance to prevent lens tilting, resolving the contradiction between achieving sufficient movement and maintaining structural simplicity.
2Length of moving object
If SMA wire is arranged at acute angles to increase movement, then the degree of movement is enhanced, but off-axis forces cause lens tilting
Solution Approach 1:
Multiple SMA wires are arranged symmetrically at acute angles to the optical axis, creating balanced off-axis force components. The symmetric configuration ensures that lateral force components from individual wires cancel each other out, while the axial components add up to provide the desired lens movement without causing tilting.
Solution Approach 2:
While the overall arrangement is symmetric for force balancing, individual SMA wires are positioned asymmetrically at acute angles rather than parallel to the optical axis. This asymmetric angular arrangement is what enables the movement amplification effect while the symmetric multiplication of such wires provides force balance.
3Volume of moving object
If the actuation apparatus is miniaturized, then the camera size is reduced, but the available space for SMA wire arrangement is limited
Solution Approach 1:
The acute angular arrangement of SMA wires utilizes three-dimensional space more efficiently within the miniaturized camera volume. By arranging wires at angles rather than parallel to the optical axis, the design achieves amplified lens movement without proportionally increasing the lateral footprint, thus accommodating miniaturization constraints.
Solution Approach 2:
The SMA wire arrangement is integrated within the compact camera structure, with wires positioned to extend from the lens element toward the camera housing in a nested configuration. This allows the actuation mechanism to be embedded within the minimal available space while still achieving the required lens displacement range.
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
The solution enhances the degree of movement along the optical axis, balances forces to prevent lens tilting, and facilitates the use of compact suspension systems, thereby improving the miniaturization and performance of miniature camera lenses.
Implementation Method 1
The SMA material is arranged on heating to drive movement of the camera lens element. Actuation may be achieved by control of the temperature of the SMA material over an active temperature range in which the SMA material changes between martensite and austenite phases in which the stress and strain of the SMA material changes.
Implementation Method 2
The temperature of the SMA material may be changed by selectively passing a current through the SMA material to heat it causing a phase change
Implementation Method 3
The solution employs a suspension system with resilient flexures to balance off-axis forces and resist tilting
Data Source
AI summary
A camera lens actuation apparatus for driving motion of a camera lens supported on a support structure by a suspension system. The apparatus incorporates a subassembly comprising SMA wire connected to at least one mounting member which is mounted to the support structure. At least one pair of lengths of SMA wire are held in tension between the camera lens element and the support structure at respective acute angles to the optical axis applying a tensional force having a component along the optical axis. The lengths of SMA wire in the pair are held at angle as viewed along the optical axis. There may be plural pairs with a balanced arrangement in which the forces generated have no net component perpendicular to the optical axis and generate no net torque around any axis perpendicular to the optical axis. A control circuit controls heating of the SMA wire in response to a measure of its resistance.