Lens Drive Unit with Non-Uniform Center Yoke Height
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Solution Overview
Problem
Conventional linear actuators face challenges in providing sufficient thrust to drive lenses accurately to both ends of the center yoke while maintaining a compact size, as thrust is low near the ends and increasing the center yoke length to achieve this results in a larger lens drive unit.
Innovation Solution
A lens drive unit design featuring two permanent magnets, a yoke with center and back yoke portions, and a coil that surrounds part of the center yoke, where the height of the center yoke facing the magnets is smaller near the middle than at the ends, and the gap between the yoke and magnets is larger near the ends, ensuring consistent thrust across the drive range without increasing the unit's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the length of the center yoke is increased to obtain thrust up to the end of the lens drive range, then the thrust is sufficient across the drive range, but the lens drive unit becomes larger in size
Solution Approach 1:
The patent applies local quality by making the center yoke height position-dependent: the height is smaller near the middle part in the optical axis direction and larger near the two ends. This non-uniform height distribution optimizes the magnetic field strength locally - providing sufficient thrust at the ends where it is typically weaker, while maintaining compact dimensions in the middle region, thus resolving the contradiction between thrust sufficiency and compact size
2Volume of moving object
If the center yoke height is reduced to make the lens drive unit more compact, then the size is reduced, but the thrust becomes insufficient near the ends of the drive range
Solution Approach 1:
The patent implements local quality by varying the center yoke height across different positions along the optical axis. The height is specifically designed to be smaller at the middle part and larger at the two ends, creating localized magnetic field optimization that maintains sufficient thrust at the drive range ends while achieving overall compact dimensions
Solution Approach 2:
The patent resolves the contradiction by transitioning from a uniform one-dimensional center yoke structure to a three-dimensional structure with varying height across different positions. This dimensional variation allows the system to achieve both compact overall size and sufficient localized thrust by optimizing the magnetic field distribution in the vertical dimension
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 achieves necessary thrust to drive the lens up to its full range while maintaining a compact size, preventing thrust reduction near the ends and allowing for a more compact lens barrel.
Implementation Method 1
The lens drive unit includes two permanent magnets, a yoke, and a coil... drives a lens back and forth in the optical axis direction
Implementation Method 2
The yoke has center yoke portions provided in the space where the two permanent magnets are facing each other... and a connect yoke portion that magnetically joins the center yoke portions and the back yoke portion
Data Source
AI summary
A lens drive unit 10 comprises permanent magnets 215a and 215b, a yoke 211, and a coil 210. The yoke 211 has center yoke portions 221a and 222a, a back yoke portion 231 and a connect yoke portion that magnetically joins the center yoke portions 221a and 222a and the back yoke portion 231. The coil 210 is wound so as to surround part of the center yoke portions 221a and 222a. The height of a surface of the center yoke portions facing the permanent magnets in an orthogonal direction to the optical axis direction is such that the height near the middle part in the optical axis direction is smaller than the height near the two ends in the optical axis direction.