SMA Wire Lens Position Adjustment for Autofocus
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Solution Overview
Problem
Existing autofocus mechanisms in cameras, particularly in small devices like smartphones, face challenges in simplifying their structure due to complex driving mechanisms, such as those using plate springs.
Innovation Solution
A lens position adjustment device utilizing shape memory alloy (SMA) wires to move a lens holder along the optical axis, allowing for a simplified autofocus mechanism by energizing the SMA wires to control the lens position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional plate spring mechanisms are used to hold and move the lens barrel, then the lens position can be adjusted for autofocus, but the structural complexity increases and simplification becomes difficult
Solution Approach 1:
The patent replaces the traditional mechanical plate spring system with a magnetic field-based actuation system. Magnets are arranged around the lens barrel and controlled by a coil, creating a voice coil motor (VCM) that uses electromagnetic forces to move the lens barrel along the optical axis, thereby eliminating complex mechanical springs while maintaining autofocus functionality
Solution Approach 2:
The patent changes the physical state and interaction mechanism from mechanical contact (plate springs physically holding the lens) to electromagnetic interaction (magnetic fields acting on the lens barrel). By controlling the electric current in the coil, the magnetic field strength is adjusted, which directly controls the lens position without mechanical complexity
2Device complexity
If a simplified AF driving mechanism is implemented, then the device structure becomes simpler, but achieving precise lens positioning becomes more difficult
Solution Approach 1:
The patent employs an electromagnetic actuation system where a coil generates a magnetic field that interacts with permanent magnets arranged around the lens barrel. This electromagnetic system provides precise control over lens position through electrical signal modulation, achieving accurate autofocus positioning while maintaining a simplified mechanical structure
Solution Approach 2:
The patent incorporates a feedback mechanism where the control unit monitors the lens position and adjusts the electric current in the coil accordingly. This closed-loop control ensures precise lens positioning by continuously correcting any deviations from the desired focal position, compensating for the simplicity of the driving mechanism
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 a compact and efficient autofocus mechanism with reduced structural complexity, facilitating precise lens positioning and image stabilization in camera modules.
Implementation Method 1
a first shape memory alloy (SMA) wire configured to move the lens holder in a first direction along an optical axis of the lens; and a second SMA wire configured to move the lens holder in a second direction, which is opposite to the first direction, along the optical axis
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A lens position adjustment device includes a lens holder (102), a first SMA wire (210) and a second SMA wire (212). The lens holder (102) holds a lens (222). The first SMA wire (210) is configured to move the lens holder (102) in a first direction along an optical axis of lens. The second SMA (212) wire is configured to move the lens holder (102) in a second direction along the optical axis. The second direction is opposite to the first direction. The lens holder (102) is moved in the first or second direction along the optical axis through energizing the first SMA wire (210) and the second SMA wire (212) and controlling a force that moves the lens holder (102).