Lens Driving Magnet Layout for Precise Hall Position Feedback
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Solution Overview
Problem
Conventional lens driving devices face challenges in accurately detecting the position of the bobbin for auto-focusing and handshake compensation due to difficulties in positioning detection units like Hall sensors.
Innovation Solution
A lens driving device with a magnet configuration featuring asymmetric magnetization and a Hall sensor positioned at the intersection of N-pole and S-pole, allowing for precise detection of magnetic force changes and enhanced assemblability, along with the use of a unidirectional coil unit for efficient winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall sensor is installed for feedback detection, then position information can be detected, but the positioning of the Hall sensor becomes difficult
Solution Approach 1:
The magnet is designed with asymmetric magnetization where the N-pole and S-pole have different areas. The Hall sensor is positioned at the intersection point of the N-pole and S-pole boundaries, which is a unique asymmetric location. This asymmetric design creates a distinct magnetic field distribution that allows the Hall sensor to detect position changes accurately without requiring precise positioning during assembly, as the sensor naturally aligns with the magnetic field gradient at the pole intersection.
2Extent of automation
If a detection unit is installed to detect bobbin position, then auto-focusing function can be performed, but the device complexity increases
Solution Approach 1:
The detection function is merged into the existing magnet structure. The magnet serves dual purposes: generating the magnetic field for voice coil motor operation and providing the magnetic field gradient for Hall sensor-based position detection. By combining the actuation magnet with the sensing function, the patent eliminates the need for separate detection units, thereby reducing device complexity while maintaining auto-focusing capability.
3Power
If a magnet is used for voice coil motor operation, then electromagnetic interaction is achieved, but the magnetic field distribution becomes complex
Solution Approach 1:
The magnet is designed with non-uniform local magnetic properties through asymmetric magnetization. The N-pole and S-pole have different areas, creating localized variations in magnetic field strength and direction. This local quality variation produces a distinct magnetic field gradient at the pole intersection region, which enhances the Hall sensor's ability to detect position changes while maintaining efficient electromagnetic interaction with the voice coil.
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 configuration enables accurate position feedback for the bobbin, improving the speed and precision of auto-focusing and handshake compensation functions, while simplifying assembly and enhancing Hall sensor output.
Implementation Method 1
a detection sensor arranged at a position facing the magnet of the bobbin and detecting change in magnetic force of the magnet due to displacement of the bobbin
Implementation Method 2
The VCM (Voice Coil Motor) operates by an electromagnetic interaction between a magnet fixed in a housing and a coil unit wound on an outer circumferential surface of a bobbin
Implementation Method 3
an upper elastic member and a lower elastic member elastically supporting the bobbin
Data Source
AI summary
A lens driving device is provided, including: a holder member; a bobbin disposed at an inner side of the holder member; a magnet disposed at the holder member; a first coil unit disposed at the bobbin, and facing the magnet; a first support member coupled to the holder member and the bobbin; and a detection sensor disposed at the bobbin, and configured to detect magnetic force of the magnet, wherein the magnet includes a facing surface and an opposite surface disposed at an opposite side of the facing surface, wherein a polarity of the facing surface and a polarity of the opposite surface are different from each other, wherein a polarity of an upper portion of the facing surface and a polarity of a lower portion of the facing surface are different from each other. According to an embodiment, Hall output detected by the detection sensor can be enhanced.