Biaxial MEMS Mirror Resonant Frequency Adjustment
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Solution Overview
Problem
Existing MEMS scanning devices face challenges in adjusting their resonant frequency, particularly in reducing it, which is necessary for various applications like touch panels, as large-area mirror plates increase damping forces and costs, and altering one component's frequency affects the other's undesirably.
Innovation Solution
The introduction of moment-of-inertia-altering blocks positioned on the rear surface of the mirror plate, away from the gimbal axis, allows for independent adjustment of the resonant frequency by modifying the moment of inertia without significantly increasing mass, thus reducing the resonant frequency while maintaining low driving torque and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large mirror size is used, then the resonant frequency is difficult to increase, but the scanning angle and scanning speed are improved
Solution Approach 1:
The patent changes the physical parameters of the mirror by adding or removing material through laser trimming to adjust the resonant frequency while maintaining the large mirror size for scanning angle requirements
Solution Approach 2:
The patent applies local material removal or addition at specific locations on the mirror surface (via laser trimming) to precisely adjust the resonant frequency without affecting the overall mirror size and scanning angle
2Productivity
If the mirror size or mass is decreased, then the resonant frequency increases, but the scanning angle is reduced
Solution Approach 1:
The patent modifies the mass parameter of the mirror through selective material removal or addition, allowing resonant frequency adjustment while preserving the mirror area needed for adequate scanning angle
3Productivity
If material is removed via laser trimming, then the resonant frequency increases, but the manufacturing complexity increases
Solution Approach 1:
The patent employs automated laser trimming processes that self-regulate the material removal based on feedback from resonant frequency measurements, reducing the need for complex manual intervention and multiple trimming iterations
4Productivity
If a large-area mirror plate is used to achieve low resonant frequency, then the resonant frequency decreases, but the damping force increases
Solution Approach 1:
The patent adjusts the resonant frequency by modifying the mass distribution parameters (through material addition or removal) rather than changing the mirror area, thereby achieving low resonant frequency without the increased damping that would result from a larger mirror area
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 approach enables precise control of the resonant frequency of MEMS scanning mirrors, allowing for different frequency requirements without increasing damping forces or power consumption, and maintains the cost-effectiveness of the device by not enlarging the mirror plate area.
Implementation Method 1
One or more gimbal moment-of-inertia-altering blocks are positioned on a rear surface of the mirror plate away from the gimbal axis of rotation. Additionally, one or more mirror plate moment-of-inertia-altering blocks are positioned on a rear surface of the mirror plate away from the mirror plate rotation axis such that the distance from the mirror plate axis determines a resonant frequency of the biaxial MEMS device.
Data Source
AI summary
A biaxial micro-electromechanical (MEMS) device is disclosed. The device includes a gimbal rotatable about a gimbal axis of rotation. A pair of gimbal torsion bars connects the gimbal to a support along the gimbal rotation axis. A mirror plate is rotatable about a mirror axis of rotation, the mirror plate rotation axis being substantially perpendicular to the gimbal rotation axis. A pair of mirror plate torsion bars connects the mirror plate to the gimbal along the mirror plate axis of rotation. One or more gimbal moment-of-inertia-altering blocks are positioned on a surface of the mirror plate away from the gimbal axis of rotation. Additionally, one or more mirror plate moment-of-inertia-altering blocks are positioned on a surface of the mirror plate away from the mirror plate rotation axis such that the distance from the mirror plate axis determines a resonant frequency of the biaxial MEMS device.