Piezoelectric Stress Adjustment for MEMS Scanning Engine Frequency Stability
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Solution Overview
Problem
Torsional hinge MEMS scanning engines experience variations in resonant frequency and scan velocity due to environmental factors like temperature, which can lead to reduced reliability and operational life, especially in applications requiring precise and stable light beam scans for laser printing and projection displays.
Innovation Solution
A pivotally oscillating structure with a pair of torsional hinges supported by a piezoelectric device that adjusts stress on the hinges using electrical control signals based on feedback from sensors monitoring resonant frequency or scan velocity, allowing for real-time compensation to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scanning engine operates in variable temperature environments, then the resonant frequency and scan velocity vary, but this leads to reduced reliability and operational life
Solution Approach 1:
The patent applies parameter changes by using a piezoelectric device to dynamically adjust the stress on torsional hinges, thereby changing the mechanical parameters of the scanning engine to compensate for temperature-induced frequency drift. This allows the resonant frequency to be actively controlled and stabilized despite environmental temperature variations.
Solution Approach 2:
The patent implements feedback control by using a sensor to monitor the resonant frequency or scan velocity and using this information to control the piezoelectric device. This closed-loop feedback system automatically adjusts the hinge stress to maintain stable resonant frequency, resolving the contradiction between reliability and frequency stability.
2Stability of the object's composition
If environmental factors like temperature are not compensated, then the device structure remains simple, but the scan velocity and resonant frequency become unstable
Solution Approach 1:
The patent introduces a piezoelectric device as an intermediary element between the support structure and the torsional hinges. This intermediary component enables active compensation of temperature effects without requiring complete redesign of the scanning engine structure, thus achieving scan velocity stability with moderate complexity increase.
Solution Approach 2:
The patent employs composite material principles by integrating the piezoelectric device with the mechanical structure of the scanning engine. This combination of piezoelectric material and mechanical components creates a hybrid system that provides both structural support and active frequency stabilization.
3Reliability
If stress changes in torsional hinges are not adjusted, then the device operation is simple, but the resonant frequency drifts with temperature changes
Solution Approach 1:
The patent implements self-service automation where the sensor and piezoelectric device work together to automatically monitor and adjust the hinge stress without external intervention. The system self-regulates the resonant frequency by detecting drift and applying compensatory stress through the piezoelectric actuator, ensuring consistent performance automatically.
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 solution effectively stabilizes the resonant frequency and scan velocity of the scanning engine, enhancing its reliability and operational life by counteracting stress changes caused by temperature variations and other environmental factors, ensuring consistent performance in demanding applications.
Implementation Method 1
A pivotally oscillating structure with a pair of torsional hinges supported by a piezoelectric device that adjusts stress on the hinges using electrical control signals
Data Source
AI summary
The present invention provides methods and apparatus for adjusting the resonant frequency, scan velocity or other parameters of a pivotally functional surface such as an oscillating mirror used as the scanning engine of a laser printer or projection display. The selected parameter is adjusted by the application of tensional or compression stress to the torsional hinges of the mirror. According to one embodiment, the appropriate stress is generated by a slice of piezoelectric material bonded to the mirror device itself or to other portions of the support structure of the scanning engine.