Camera Actuator Back Yoke Structure for Magnetic Interference Control
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Solution Overview
Problem
Magnetic interference between multiple moving bodies in actuators for camera modules causes position detection errors and deteriorates driving performance, especially when implementing autofocus and optical image stabilization functions in mobile terminals with zoom lenses.
Innovation Solution
The actuator design includes a back yoke structure that minimizes magnetic interference by forming gaps with the side surfaces of magnets and using covers to concentrate magnetic fields, allowing for enhanced driving force and reduced interference between adjacent magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple magnets are installed on moving bodies to implement AF and OIS functions, then the driving force is enhanced, but magnetic interference between adjacent magnets occurs causing position detection errors
Solution Approach 1:
A magnetic shielding layer is introduced as an intermediary component between adjacent magnets to block magnetic field interference. The shielding layer, positioned in the gap between magnets, prevents magnetic flux from one magnet from reaching adjacent magnets, thereby eliminating position detection errors while preserving the driving force of each magnet
Solution Approach 2:
The harmful magnetic field interference is extracted and isolated from the system by introducing a dedicated shielding structure. The magnetic shielding layer captures and contains the magnetic flux within specific regions, preventing it from interfering with adjacent magnets and their position detection mechanisms
2Device complexity
If magnets are positioned closer together to reduce device size, then the device complexity is reduced, but magnetic interference between magnets increases
Solution Approach 1:
The magnetic shielding layer serves as a mediator that enables magnets to be positioned closer together without direct magnetic interference. By inserting the shielding layer in the gap between adjacent magnets, the design achieves compact dimensions while the shielding layer blocks the harmful magnetic flux that would otherwise cause interference in closely spaced configurations
3Power
If the gap between magnets and back yoke is reduced to improve driving efficiency, then the driving force is enhanced, but magnetic field leakage increases causing interference
Solution Approach 1:
The magnetic shielding layer acts as an intermediary that allows the gap between the magnet and back yoke to be minimized for improved driving efficiency, while simultaneously preventing magnetic field leakage from affecting adjacent components. The shielding layer is positioned to block leaked flux without interfering with the primary magnetic field needed for driving
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 design improves driving precision and operational reliability by minimizing magnetic interference, enabling more efficient and precise control of the actuator's moving parts, and allows for a more compact structure suitable for miniaturization of mobile devices.
Implementation Method 1
generate an electromagnetic force between the coil and the magnet so that the mover moves in the optical axis direction or in a direction perpendicular to the optical axis
Implementation Method 2
an actuator or camera module with a physical structure that refracts the light of the subject using a reflector placed at the front of the lens
Data Source
AI summary
An actuator for a camera according to an embodiment includes a plurality of moving bodies rotating in different directions, a magnet installed on each of the plurality of moving bodies, and a back yoke provided at a rear side of at least one of the magnets respectively installed on the plurality of moving bodies. The back yoke includes a cover that forms a gap with a side surface of a magnet provided at a front side thereof and covers the side surface.