Lens Positioning Device Using Magnetic Displacement Detection
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Solution Overview
Problem
Existing lens positioning devices using shape memory alloys face inaccuracies in displacement measurement due to non-linear resistance and length changes, and external resistances, leading to errors in lens positioning.
Innovation Solution
A lens positioning device employing three pairs of memory alloy wires and three displacement detecting units with magnetic elements and sensing elements, allowing for accurate displacement calculation in three orthogonal directions without considering external resistances or temperature effects, and eliminating the need for resistance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance change is used to infer length change of shape memory alloy wire, then displacement can be measured, but measurement precision deteriorates due to non-linear relationship and external resistance losses
Solution Approach 1:
The patent replaces the electrical resistance-based measurement system with a magnetic field-based measurement system. Instead of inferring length change through resistance changes (which suffer from non-linearity and external resistance losses), the system uses magnetic elements and magnetic field sensing elements to directly detect displacement through magnetic field changes, achieving both high precision and reliability
Solution Approach 2:
The patent introduces magnetic elements as intermediaries between the lens carrier and the magnetic field sensing elements. These magnetic elements convert the mechanical displacement into magnetic field changes that can be accurately sensed, providing a reliable intermediary measurement mechanism that avoids the direct electrical resistance issues
2Ease of operation
If resistance calculation is used to determine alloy wire length, then displacement can be calculated, but device complexity increases due to need for control elements and resistance calculation circuits
Solution Approach 1:
The patent eliminates the need for resistance calculation circuits and control elements by substituting the electrical measurement approach with a magnetic field sensing approach. The magnetic field sensing elements directly provide displacement information without requiring complex resistance calculation processing
Solution Approach 2:
The patent extracts and removes the resistance calculation functionality from the system entirely. By using magnetic field sensing, the system achieves displacement measurement without the need for control elements and resistance calculation circuits that would otherwise be required
3Adaptability or versatility
If shape memory alloy wire is used to drive lens movement, then focus and OIS functions are achieved, but measurement accuracy deteriorates due to non-linear thermal shrinkage and cold expansion characteristics
Solution Approach 1:
The patent introduces magnetic elements as intermediaries that decouple the measurement function from the shape memory alloy wire's non-linear mechanical behavior. The magnetic elements provide a linear and reliable measurement reference that is not affected by the thermal shrinkage and cold expansion characteristics of the alloy wire, allowing accurate measurement while maintaining the versatility of the SMA-driven lens positioning system
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 provides accurate, fast, and cost-effective lens positioning with improved displacement measurement accuracy and reduced product costs, suitable for greater displacement requirements and faster response times.
Implementation Method 1
There is a lens device that uses a shape memory alloy to drive the lens to move, so as to achieve focus (AF) or hand vibration compensation (OIS). The principle of such lens device utilizes the thermal shrinkage and cold expansion characteristics of the shape memory alloy.
Implementation Method 2
After current passes through the alloy wire, the alloy wire is tightened due to the rise in temperature to pull the lens carrier. Moreover, when the alloy wire shrinks due to heat, its cross section and length change
Implementation Method 3
After current passes through the alloy wire, the alloy wire is tightened due to the rise in temperature
Implementation Method 4
Each of the displacement detecting units includes a magnetic element and a magnetic field sensing element. The magnetic field sensing element is arranged on the housing and corresponding to the magnetic element to sense change of the magnetic field of the magnetic element along each of the three directions when the lens carrier moves.
Data Source
AI summary
A lens positioning device including a lens carrier, a housing, three pairs of memory alloy wires and three displacement detecting units is provided. The three pairs of memory alloy wires are used to control the displacement of the lens carrier in three directions, respectively. Each of the displacement detecting units includes a magnetic element and a magnetic field sensing element. The magnetic field sensing element is arranged corresponding to the magnetic element to sense change of the magnetic field of the magnetic element along each of the three directions when the lens carrier moves. One magnetic element of any one of the three displacement detecting units is arranged at a position that can induce the corresponding magnetic field sensing element and does not interfere with the magnetic field sensing elements of the other two of the three displacement detecting units.