Lens Moving Unit with Sensing and Correction Magnets for Stable Autofocus
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lens moving units in camera modules suffer from instability in electromagnetic force and eccentricity of the lens barrel due to magnetic forces, which hinder quick and accurate auto focusing.
Innovation Solution
A lens moving unit with a bobbin mounted with a coil unit, a cover member with a magnet, and a detection unit comprising a sensing magnet and a correction magnet, where the sensing magnet is positioned to detect the bobbin's movement and the correction magnet offsets the attractive force, ensuring accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voice coil unit motor is used for auto focusing, then the lens moving unit can perform focusing function, but electromagnetic force instability and lens barrel eccentricity occur due to magnetic force
Solution Approach 1:
The magnet is divided into two separate magnets: a first magnet for generating electromagnetic force with the coil unit, and a second magnet for generating magnetic force with the elastic member. This segmentation separates the electromagnetic actuation function from the magnetic stabilization function, eliminating the interference between magnetic forces that causes lens barrel eccentricity and electromagnetic force instability.
2Ease of operation
If a magnet is mounted on the cover member for auto focusing, then focusing function is achieved, but magnetic force causes lens barrel eccentricity
Solution Approach 1:
The single magnet on the cover member is segmented into two separate magnets positioned at different locations: the first magnet adjacent to the coil unit for electromagnetic interaction, and the second magnet positioned to interact with the elastic member. This segmentation allows independent optimization of electromagnetic force generation and magnetic force balance, eliminating lens barrel eccentricity.
Solution Approach 2:
The elastic member acts as an intermediary between the second magnet and the lens barrel, mediating the magnetic force to provide stable support without direct magnetic attachment to the lens barrel. This intermediary approach prevents magnetic interference with the lens barrel while maintaining focusing capability.
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 solution allows for accurate and rapid auto focusing by detecting the bobbin's position using a sensing magnet and offsetting attractive forces with a correction magnet, stabilizing the bobbin's position relative to the cover member, thereby enhancing focusing precision and reducing focusing time.
Implementation Method 1
a voice coil unit motor. The voice coil unit motor is operated by an electric interaction between a magnet fixed to a housing and a coil unit wound on a periphery of a bobbin coupled to a lens barrel to perform an auto focusing function
Implementation Method 2
a vertically-moving bobbin is elastically supported by upper and bottom elastic members to reciprocally move to a direction parallel to an optical axis
Implementation Method 3
a detection unit configured to detect a movement parallel to an optical axis of the bobbin, wherein the detection unit includes a sensing magnet mounted at a periphery of the bobbin, and a position detection sensor arranged at a lateral wall of the cover member and formed at an inner lateral surface opposite to the sensing magnet
Implementation Method 4
a correction magnet mounted at a side opposite to that of the sensing magnet
Data Source
AI summary
One embodiment of a lens moving unit includes a bobbin mounted with at least one sheet of lens and arranged at a periphery with a coil unit, a cover member mounted with a magnet at a position corresponding to that of the coil unit, upper and bottom elastic members respectively coupled at one distal end to upper and bottom surfaces of the bobbin to support movement of the bobbin to an optical axis direction, and a detection unit to detect a movement parallel to an optical axis of the bobbin, wherein the detection unit includes a sensing magnet mounted at a periphery of the bobbin, and a position detection sensor arranged at a lateral wall of the cover member and formed at an inner lateral surface opposite to the sensing magnet, wherein the bobbin includes a correction magnet mounted at a side opposite to that of the sensing magnet.