Piezoelectric MEMS Mirror Actuation for Large Scanning Angles
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Solution Overview
Problem
Conventional electrostatically actuated scanning mirrors face inefficiencies due to high voltage requirements and limited electrode distance, leading to reduced force production and increased size and rotational inertia, making them unsuitable for large scanning angles and amplitudes.
Innovation Solution
A micro-optical electromechanical device with a spring structure incorporating piezoelectric transducers and bending springs, where the piezoelectric thin-film layers are positioned to induce displacement and tilt the mirror, allowing for larger tilt angles and amplitudes with lower voltages and reduced size, utilizing a silicon wafer and cavity silicon-on-insulator process for manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If electrostatic actuation is used with high voltage to produce sufficient force, then the mirror can be actuated, but the device requires high voltage and has limited electrode distance reducing efficiency
Solution Approach 1:
The patent replaces the electrostatic actuation mechanism with a piezoelectric actuation mechanism. The piezoelectric transducer converts electrical signals directly into mechanical displacement through the piezoelectric effect, eliminating the need for high voltages and comb electrode structures. This substitution resolves the contradiction by providing sufficient actuating force through a different physical principle that does not suffer from the voltage-distance trade-off inherent in electrostatic systems.
Solution Approach 2:
The patent changes the fundamental operating parameter of the actuator from voltage (electrostatic) to electrical signal that controls piezoelectric displacement. The piezoelectric material responds to electrical fields by changing its physical dimensions, providing a direct and efficient conversion mechanism. This parameter change enables the system to achieve the required force with much lower voltage requirements and improved efficiency across the entire motion range.
2Force
If electrode distance is reduced to maximize force, then actuating force increases, but the device size and manufacturing complexity increase
Solution Approach 1:
The patent eliminates the complex comb electrode structure entirely by substituting it with a piezoelectric transducer. The piezoelectric element provides the necessary actuating force through its inherent piezoelectric properties, removing the need for precisely engineered electrode gaps and complex interdigitated structures. This substitution dramatically simplifies the device architecture while maintaining or improving force output.
3Length of moving object
If mirror size is increased for large scanning angle, then scanning amplitude improves, but rotational inertia increases requiring higher force
Solution Approach 1:
The patent replaces the high-voltage electrostatic actuation system with a piezoelectric actuation system that provides higher force density. The piezoelectric transducer generates sufficient force to move larger mirrors with greater scanning angles without requiring proportionally higher voltages. This substitution enables the system to achieve large scanning amplitudes while managing the rotational inertia challenge through the high force density characteristics of piezoelectric materials.
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 device achieves high force production at lower voltages, maintaining efficiency across the entire motion range and reducing the size and rotational inertia of the mirror, enabling larger scanning angles and amplitudes with improved manufacturing feasibility.
Implementation Method 1
The spring structure includes piezoelectric transducers each including at least one thin-film layer of piezoelectric material on one side of a bending spring and being adapted to induce in the bending spring a displacement
Data Source
Figure 1a~1c
Figure 2~3
Figure 4~5
AI summary
A micro-optical electromechanical device that includes a body (20), a mirror element (23, 27), and a spring structure (28a, 29a) adapted to flexibly support the mirror element (23, 27) to the body (20). The spring structure includes at least one piezoelectric transducer (29a) adapted to induce in the spring structure a displacement that moves the mirror element (23, 27).