MEMS Reflector Center Support for Parasitic Oscillation
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Solution Overview
Problem
Microelectromechanical (MEMS) reflectors in LIDAR systems face issues with parasitic oscillation modes, particularly the piston mode, which can have low resonance frequencies and interfere with desired operational oscillation modes, making it challenging to maintain high tilt amplitudes while minimizing unwanted vibrations.
Innovation Solution
A central support structure is fixed to the reflector's center, perpendicular to the device plane, extending from packaging components, which increases the spring constant of piston mode oscillations, thereby raising the resonance frequency above operational frequencies and reducing vibration amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If flexible or partly mobile suspenders are used to support the reflector, then the tilt amplitude can be generated, but the piston mode resonance frequency remains low and interferes with operational modes
Solution Approach 1:
The support structure is segmented into two functional parts: flexible suspenders attached to the reflector edges for tilt generation, and a rigid central support attached to the reflector center for piston mode suppression. This segmentation allows each part to perform its specialized function without interfering with the other.
Solution Approach 2:
Different parts of the reflector are provided with different support characteristics: the edges have flexible suspenders that allow tilt motion, while the center has a rigid support that suppresses piston mode. This local differentiation of support quality enables simultaneous achievement of tilt amplitude and piston mode frequency separation.
2Ease of operation
If the reflector is designed to maximize tilt amplitude at operational frequencies, then scanning performance is improved, but parasitic piston mode oscillations occur at low frequencies that can interfere with operation
Solution Approach 1:
The rigid central support structure converts the harmful low-frequency piston mode oscillations into a beneficial high-frequency mode. By increasing the piston mode resonance frequency above the operational scanning frequencies, the previously harmful parasitic oscillation becomes a high-frequency mode that does not interfere with the low-frequency scanning operation.
3Use of energy by moving object
If thin reflector design is used to reduce mass, then power consumption is reduced, but the piston mode amplitude becomes larger at the center compared to edges
Solution Approach 1:
The support parameters are changed by introducing a rigid central support with different stiffness characteristics than the edge suspenders. This parameter change compensates for the non-uniform piston mode amplitude distribution in thin reflectors by providing additional support at the center where the amplitude is largest.
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 shifts the resonance frequency of parasitic oscillation modes, such as the piston mode, above operational frequencies, enhancing the vibration performance and reducing unwanted vibrations in MEMS reflector systems.
Implementation Method 1
the resonance frequencies of all parasitic oscillation modes, including the piston mode, become much larger than the resonance frequencies of the operational oscillation modes
Data Source
AI summary
A scanning microelectromechanical reflector system comprising a reflector with a reflector body, a first cavity vertically aligned with the reflector body above the device plane and a second cavity vertically aligned with the reflector body below the device plane. The reflector also comprises a central attachment point located within a central opening in the reflector body. One or more flexures extend from the sidewalls of the central opening to the central attachment point. The flexures allow the central attachment point to remain stationary in the device plane when actuator units tilt the reflector body out of the device plane. The reflector system comprises a central support structure which extends through the cavity to the central attachment point of the reflector.