Eight-Wire SMA Actuator Assemblies for Compact Camera OIS and AF
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Solution Overview
Problem
Existing miniature cameras with folded optics arrangements face challenges in providing simultaneous optical image stabilization (OIS) and auto-focus (AF) due to space constraints, as conventional actuators are bulky and require adjustments to the optical and sensor layout.
Innovation Solution
An SMA actuation apparatus using eight SMA actuator wires arranged in groups on opposite sides of a movable element with reflectional symmetry in three orthogonal planes, allowing for translational and rotational movements to achieve OIS and AF independently or simultaneously, without increasing the apparatus' size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional actuators are used for OIS and AF, then the actuators can provide the required force and movement, but the apparatus size increases and space constraints are violated
Solution Approach 1:
The actuator system is segmented into multiple independent SMA wire actuators (at least three wires) that can be arranged in different spatial configurations. Each wire provides force in a specific direction, and by selectively actuating different combinations of these segmented actuators, the system achieves both OIS and AF functions without requiring a single bulky actuator, thus reducing overall apparatus size while maintaining force requirements.
Solution Approach 2:
The patent utilizes the phase transformation properties of shape memory alloy materials, which undergo significant dimensional changes (parameter change) in response to temperature variations. By applying electrical current to heat the SMA wires, they contract and generate force; when cooled, they return to their original length. This parameter change mechanism enables compact actuator design with high force output relative to size, resolving the contradiction between force generation and apparatus volume.
2Length of moving object
If conventional actuators are used for OIS and AF, then the actuators can provide the required movement, but the optical and sensor layout must be adjusted
Solution Approach 1:
The SMA wire actuator system is designed with multi-functionality to perform both OIS (optical image stabilization) and AF (auto-focus) operations using the same actuator assembly. By selectively controlling which wires are actuated and in what combinations, the system can achieve lateral movements for OIS and axial movements for AF, eliminating the need for separate dedicated actuators for each function and simplifying the overall optical and sensor layout.
Solution Approach 2:
The patent employs dynamic control of the SMA wire actuators where the same physical actuator assembly can dynamically switch between different operational modes (OIS vs. AF) based on control signals. The movable element can be dynamically positioned in three-dimensional space by varying the activation state of different wire combinations, allowing the system to adapt to different operational requirements without physical reconfiguration, thus reducing layout complexity.
3Adaptability or versatility
If SMA actuator wires are arranged to provide simultaneous OIS and AF, then both functions can be achieved, but the arrangement complexity increases
Solution Approach 1:
The patent employs asymmetric arrangements of SMA wire actuators in certain embodiments, where wires are positioned at different locations and angles relative to the movable element. This asymmetric configuration, combined with selective actuation patterns, enables the system to achieve both OIS and AF functions. The asymmetry allows for optimized force vectors that can produce both lateral and axial movements, managing the complexity through deliberate non-uniform positioning rather than requiring symmetric multi-actuator configurations.
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 SMA actuation apparatus enables compact and efficient OIS and AF in miniature cameras by utilizing symmetrical SMA wires, maintaining the camera's compact form factor and preserving the optical path without requiring adjustments to the existing layout.
Implementation Method 1
eight SMA actuator wires connected between the movable element and the support structure such that, on contraction, the actuator wires provide a force on the movable element
Data Source
Figure 1
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Figure 3A~3D
AI summary
The present techniques provide actuator assemblies and methods of controlling actuator assemblies in which two groups of actuator wires are arranged on opposite sides of a movable element to which they are connected. One approach of the present techniques provides an SMA actuation apparatus comprising: a support structure; a movable element, the movable element being supported on the support structure so as to be movable relative to the support structure; and eight SMA actuator wires connected between the movable element and the support structure such that, on contraction, the actuator wires provide a force on the movable element, wherein each actuator wire is inclined with respect to a notional primary axis, wherein the actuator wires are suitable for moving the movable element with translational movement in any direction and/or rotational movement about any axis,and wherein the actuator wires are arranged such that two groups of four of said wires are positioned on opposite sides of the movable element.