Lens Driving Magnet Layout for Precise AF Sensing
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Solution Overview
Problem
Existing lens driving devices face challenges in achieving precise auto-focusing (AF) driving due to interference between the magnet for driving and the magnet for sensing, which affects the position sensor output, particularly in miniaturized and low-power consuming camera modules used in smartphones and similar devices.
Innovation Solution
A lens driving device design that includes a bobbin with a first coil and magnets, where the second magnet is positioned to minimize interference by having a shorter length along the optical axis and increasing width in other directions, allowing for precise AF driving by optimizing the magnetic field sensing range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second magnet is positioned closer to the first coil to enhance sensing capability, then the position sensor output range is improved, but interference between the driving magnet and sensing magnet increases
Solution Approach 1:
The patent applies dimensionality change by making the second magnet shorter in the optical axis direction (vertical dimension) and wider in the radial direction (horizontal dimension). This dimensional transformation allows the magnet to maintain sufficient sensing capability in the radial direction while reducing magnetic interference in the optical axis direction where the driving magnet is located.
Solution Approach 2:
The second magnet is designed with non-uniform dimensions, being shorter in the optical axis direction and wider in the radial direction. This local quality differentiation optimizes the magnetic field distribution, providing strong sensing output in the radial direction while minimizing interference in the optical axis direction.
2Volume of moving object
If the camera module is miniaturized to reduce device size, then the overall device dimensions are improved, but the separation distance between driving and sensing magnets decreases, increasing interference
Solution Approach 1:
The patent resolves the miniaturization interference problem by changing the dimensional characteristics of the second magnet. By making it shorter in the optical axis direction and wider radially, the design achieves compact overall size while maintaining adequate magnetic field separation and sensing capability.
Solution Approach 2:
The patent changes the geometric parameters of the second magnet, specifically reducing its length in the optical axis direction and increasing its width in the radial direction. This parameter optimization allows the camera module to be miniaturized while maintaining sufficient separation between magnetic components to reduce interference.
3Force
If the second magnet is made longer in the optical axis direction to increase magnetic field strength, then the sensing capability is improved, but the interference with the driving magnet increases
Solution Approach 1:
The second magnet is designed with differentiated local dimensions, being shorter in the optical axis direction where interference occurs and wider in the radial direction where sensing is needed. This local quality optimization maintains sufficient magnetic field strength for sensing while minimizing interference with the driving magnet.
Solution Approach 2:
The patent transforms the magnetic field generation approach by orienting the second magnet's extended dimension radially rather than axially. This dimensional change allows the magnet to produce strong radial magnetic fields for sensing while reducing axial magnetic field strength that would interfere with the driving magnet.
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 design effectively suppresses interference between the driving and sensing magnets, enhancing the range of the position sensor output and enabling precise AF driving, even in compact camera modules.
Implementation Method 1
a first position sensor disposed on the housing and configured to sense strength of a magnetic field of the second magnet
Implementation Method 2
a first coil disposed on an outer circumference surface of the bobbin
Data Source
AI summary
One embodiment comprises: a housing; a bobbin, which is arranged inside the housing and is for mounting a lens; first coils arranged around the outer peripheral surface of the bobbin; a first magnet arranged in the housing; a second magnet arranged at the bobbin and spaced from the first coils; and a first position sensor arranged in the housing and sensing the intensity of a magnetic field of the second magnet, wherein the length of the second magnet in the direction of an optical axis is shorter than the length of thereof in the direction perpendicular to the direction of the optical axis.