Lens Barrel Magnet Layout for Accurate VCM Position Sensing
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Solution Overview
Problem
In lens barrels driven by voice coil motors, the increasing number of magnets leads to a disturbance magnetic field that reduces the output of magnetic sensors used for position detection, causing interference and inaccurate readings.
Innovation Solution
The lens barrel design incorporates a configuration where magnetic force applying members, including flat plate-shaped yokes and magnets, are positioned to minimize the disturbance magnetic field impact on the sensor, with specific angles and symmetrical arrangements to optimize magnetic flux density and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of magnets in the voice coil motor is increased to improve driving force, then the magnetic driving capability is enhanced, but the disturbance magnetic field increases causing sensor output reduction and detection inaccuracy
Solution Approach 1:
A magnetic shielding member is introduced as an intermediary component between the magnets and the magnetic sensor. This shielding member selectively blocks disturbance magnetic field lines while allowing the position detection magnetic field to pass through, thereby protecting the sensor from harmful magnetic interference without affecting the voice coil motor's driving capability
Solution Approach 2:
The magnetic shielding member is positioned specifically at locations where disturbance magnetic fields affect the sensor most strongly. By applying shielding only in these critical local areas rather than throughout the entire structure, the solution effectively reduces sensor interference while maintaining overall system performance and minimizing unnecessary material usage
2Object-affected harmful factors
If magnetic shielding measures are added to protect the sensor, then sensor protection from disturbance magnetic field is improved, but device complexity increases
Solution Approach 1:
The magnetic shielding member is designed to serve multiple functions simultaneously: it shields the magnetic sensor from disturbance magnetic fields, maintains the magnetic flux density required for position detection, and integrates with the existing voice coil motor structure. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving effective sensor protection
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 effectively suppresses the influence of the disturbance magnetic field, allowing for accurate position detection and improved sensor output while maintaining a compact design.
Implementation Method 1
a magnetic sensor that detects an amount of movement of the lens frame
Implementation Method 2
a lens barrel in which a lens is driven by means of a voice coil motor (VCM)
Data Source
AI summary
Provided is a lens barrel with which it is possible to suppress the influence of a disturbance magnetic field on a magnetic sensor. A coil that surrounds an outer periphery of a lens frame, magnetic force applying members that are disposed at a plurality of positions around the lens frame, and a magnetic sensor that detects an amount of movement of the lens frame are provided. In a plane orthogonal to an optical axis, the magnetic force applying members that are disposed on both sides adjacent to the magnetic sensor are disposed in postures in which a first angle (θ1, θ2) formed between a first straight line (L1) and a second straight line (L2) is smaller than 45°, the first straight line (L1) being a straight line passing through the magnetic sensor and the optical axis and the second straight line (L2) being a straight line orthogonal to surfaces of a first yoke and a second yoke of the magnetic force applying member that face each other.