Lens Barrel Magnet Layout for Accurate Magnetic Sensor Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The presence of disturbance magnetic fields from increased magnet installation in voice coil motor-driven lens barrels interferes with magnetic sensor output, reducing detection accuracy.
Innovation Solution
The lens barrel design includes specific angular and positional arrangements of magnetic force applying units and the magnetic sensor, such as symmetrically disposed yokes and magnets relative to the optical axis, to minimize the influence of disturbance magnetic fields on the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple magnetic force applying members are installed around the lens frame, then the driving force of the voice coil motor is improved, but the disturbance magnetic field increases and interferes with the magnetic sensor output
Solution Approach 1:
The magnetic force applying members are disposed asymmetrically with respect to the magnetic sensor, specifically at positions where the angle between the straight line passing through the magnetic sensor and optical axis, and the straight line orthogonal to the yoke surfaces is 45 degrees or more. This asymmetric angular positioning reduces the disturbance magnetic field's influence on the sensor while preserving driving force.
Solution Approach 2:
The solution addresses the magnetic field interference by changing the spatial dimension of magnet placement. Instead of uniformly distributing magnets around the lens frame, they are positioned at specific angular coordinates (45 degrees or more from the sensor axis), effectively using angular dimension to minimize interference while maintaining radial driving force.
2Device complexity
If magnetic force applying members are disposed close to the magnetic sensor, then the device complexity is reduced, but the sensor detection accuracy deteriorates due to magnetic field interference
Solution Approach 1:
The angular position parameter of the magnetic force applying members is changed to 45 degrees or more relative to the magnetic sensor axis. This parameter modification allows the magnets to be positioned close to the sensor structurally while maintaining detection accuracy by controlling the angular relationship that determines magnetic field interference.
3Volume of moving object
If the lens barrel uses a compact design with integrated magnetic components, then the overall size is reduced, but the disturbance magnetic field affects the magnetic sensor more strongly
Solution Approach 1:
The patent resolves the conflict between compact size and magnetic interference by transitioning from radial distance control to angular position control. The magnetic force applying members are placed at specific angular orientations (45 degrees or more from the sensor axis), allowing compact radial integration while using angular dimension to minimize magnetic field interference with the sensor.
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 enhances sensor output by reducing the impact of disturbance magnetic fields, allowing for precise position detection of the lens frame while maintaining a compact design.
Implementation Method 1
a coil that is mounted to the lens frame and that surrounds an outer periphery of the lens frame, magnetic force applying members that are disposed at a plurality of positions around the lens frame and that apply magnetic forces to the coil
Implementation Method 2
a magnetic sensor that detects an amount of movement of the lens frame
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.