Bidirectional SMA Lens Drives for Faster Camera Autofocus
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Solution Overview
Problem
Existing camera modules with autofocus functions using electromagnetic motors are bulky and complex, hindering miniaturization efforts, while SMA drivers in prior art suffer from limited stroke, non-uniform speed, and increased power consumption due to one-way movement and complex wiring that increases module size.
Innovation Solution
A camera apparatus utilizing an SMA driving device with upgoing and downgoing drivers symmetrically disposed to drive the lens bidirectionally, reducing stroke length and improving speed and stability by balancing forces, and optimizing wiring to minimize size and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic motors are used to drive the lens assembly for autofocus, then the focusing function is achieved, but the structure becomes complex and the module size increases
Solution Approach 1:
The patent replaces the electromagnetic motor system with a shape memory alloy (SMA) actuator system. The SMA actuator uses thermal-mechanical coupling to drive the lens assembly, eliminating the need for complex electromagnetic components such as motors, magnets, and coils. This substitution significantly simplifies the overall structure while maintaining the autofocus function.
Solution Approach 2:
The patent utilizes the temperature-dependent shape memory effect of SMA materials. By changing the temperature of the SMA actuator through electrical heating, the material undergoes phase transformation that causes it to change shape and drive the lens assembly. This parameter-based control (temperature) replaces the mechanical electromagnetic driving mechanism.
2Volume of moving object
If a single SMA line is used to drive the lens upward, then the actuator size is reduced, but the driving stroke is limited and power consumption increases
Solution Approach 1:
The patent divides the single SMA actuator into multiple independent SMA lines (typically three or more). Each SMA line is independently controllable and works in parallel to drive the lens assembly. This segmentation allows the system to achieve the required driving stroke by coordinating the contraction of multiple lines, reducing the power consumption of each individual line while maintaining the overall driving capability.
Solution Approach 2:
The patent implements dynamic control of multiple SMA lines with different contraction ratios. By adjusting the heating current and timing for each SMA line dynamically, the system can optimize the driving stroke and power consumption. The coordinated contraction of multiple lines with different characteristics enables flexible stroke adjustment and energy efficiency.
3Reliability
If the lens is driven from the bottom position to the top position for focusing, then the full focusing range is achieved, but the response speed becomes slow due to the large movement stroke
Solution Approach 1:
The patent transitions from a single-dimensional (one-way upward driving) approach to a multi-dimensional approach by arranging multiple SMA lines in different spatial orientations. This allows the lens assembly to be driven not only upward but also downward and in intermediate positions, enabling bidirectional and multi-position focusing control that reduces the required stroke length and improves response speed.
Solution Approach 2:
The patent uses multiple SMA lines that can be pre-positioned and controlled to achieve the desired lens position more quickly. By having multiple actuators ready to act simultaneously or in coordinated sequence, the system can reduce the time required to achieve focusing compared to a single SMA line that must sequentially complete the entire stroke.
4Speed
If multiple SMA lines are arranged in multiple directions to enable bidirectional lens movement, then the focusing speed and stability are improved, but the wiring complexity increases
Solution Approach 1:
The patent designs the multiple SMA lines to serve multiple functions simultaneously. Each SMA line not only provides driving force in its specific direction but also contributes to the overall stability and positioning of the lens assembly. This multi-functionality reduces the need for additional separate control mechanisms and simplifies the overall wiring architecture.
Solution Approach 2:
The patent combines the control of multiple SMA lines into a unified control system. By integrating the driving functions of multiple lines into a coordinated control scheme, the patent reduces the complexity of individual control circuits and achieves efficient bidirectional lens movement through consolidated wiring and control logic.
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 achieves reduced power consumption, improved focusing speed, and enhanced stability by halving the unidirectional movement stroke, allowing for more compact and efficient camera module design.
Implementation Method 1
SMA (shape memory alloy) material is set as another feasible actuator due to its thermal shrinkage characteristics
Implementation Method 2
the SMA driver thermally shrinks, a middle part of the SMA line draws the camera assembly upwardly to move upward. When the SMA driver cools down, the SMA line relaxes the traction of the camera assembly
Data Source
AI summary
The present disclosure provides a camera apparatus, an SMA driving device and a manufacturing method, a driving method and a wiring method, wherein the SMA driving device further comprises a lens carrier, at least one upgoing driver, and at least one downgoing driver; wherein the lens carrier is connected to the upgoing driver, and the upgoing driver supports the lens carrier upwardly in a thermally driven manner, and pulls the lens carrier to move upward; wherein the lens carrier is connected to the downgoing driver, and the downgoing driver draws the lens carrier downwardly in a thermally driven manner, and pulls the lens carrier to move downward; and wherein the lens is disposed on the lens carrier of the SMA driving device, and the SMA driving device drives the lens to move up and down, thereby improving the focusing speed of the lens.