SMA Autofocus Assembly With Equal-Current Wires to Reduce Tilt
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Solution Overview
Problem
Existing shape memory alloy (SMA) systems for camera lens autofocus are bulky and require a large footprint, limiting their Z-stroke range and compactness.
Innovation Solution
A buckler wire actuator assembly with SMA wires connected in series and isolated electrical conductors to ensure equal current flow, minimizing force imbalance and dynamic tilt, allowing for a compact design with high Z-stroke range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SMA systems are used for autofocus, then the system can provide focusing function, but the system becomes bulky with large footprint and height clearance
Solution Approach 1:
The patent implements a nested configuration where the retractable lens assembly is positioned within the camera housing, and the SMA wires are routed through the housing structure. The lens barrel, focus drive mechanism, and SMA actuation system are nested within each other, allowing the focusing function to be achieved while minimizing the overall footprint of the autofocus system.
2Reliability
If traditional SMA systems are used for autofocus, then the system can provide focusing function, but the system requires large height clearance
Solution Approach 1:
The patent transitions from a linear extension mechanism to a rotational focusing mechanism. The lens assembly rotates around the optical axis within a compact cylindrical housing, eliminating the need for large height clearance associated with linear extension. The SMA wires are arranged to enable rotational motion through torsional actuation, achieving focusing functionality in a different dimensional approach.
3Ease of manufacture
If SMA wires are connected in parallel, then the system is simpler to manufacture, but force imbalance and dynamic tilt occur
Solution Approach 1:
The patent implements a feedback control system where sensors detect the position and orientation of the lens assembly during focusing operation. The control system processes this feedback information and adjusts the current distribution to the SMA wires in real-time, compensating for any force imbalances and preventing dynamic tilt. This closed-loop control ensures stable and precise focusing while maintaining manufacturing simplicity.
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 assembly achieves a compact footprint with high Z-stroke range, reducing dynamic tilt and image distortion, enhancing picture quality.
Implementation Method 1
The suspension is actuated by applying electrical drive signals to the SMA wires
Implementation Method 2
Each of the SMA wires has one end attached to the support assembly, and an opposite end attached to the moving assembly
Data Source
AI summary
A buckler wire actuator assembly is provided herein. The buckler wire actuator assembly includes at least one buckler frame mounted onto a base of the buckler wire actuator assembly and including at least one isolated electrical conductor. The buckler wire actuator assembly also includes a first SMA wire in electrical connection to one of the at least one isolated electrical conductor a second SMA wire opposite the first SMA wire. The first and second SMA wires are arranged in series to enable both the first and second SMA wires to receive equal current from a current input.