MEMS Scanner Suspension for High Frequency and Large Tilt
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Solution Overview
Problem
Current MEMS scanners in LIDAR systems face limitations in maximum angular range and field of view due to high stiffness suspensions required for maintaining high resonance frequencies and robustness against vibrations, which restricts the mechanical tilt angle and size of the mirror, making it challenging to achieve both high refresh rates and large mirror diameters while maintaining mechanical stress within safe limits.
Innovation Solution
A MEMS device with a suspension assembly that includes a central support beam and outer support beams, allowing the oscillator structure to oscillate at a resonance frequency of at least 2 kHz with a maximum deflection angle of 10° or more, while maintaining mechanical stress levels at or below 3 GPa, enabling large mirror diameters and extended angular ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high stiffness suspensions are used to maintain high resonance frequencies and robustness against vibrations, then the resonance frequency and vibration resistance are improved, but the mechanical tilt angle and field of view are limited
Solution Approach 1:
The suspension assembly is divided into multiple support beams (central support beam, first outer support beam, second outer support beam, and interior support beams) that work together to provide both stiffness and flexibility. This segmentation allows the system to achieve high resonance frequency through the combined stiffness of multiple beams while still permitting large mechanical tilt angles through the coordinated deformation of individual beams.
Solution Approach 2:
Different regions of the suspension assembly have different structural properties optimized for their specific functions. The central support beam provides primary structural support and stiffness for high resonance frequency, while the outer support beams and interior support beams are configured to allow greater flexibility and larger tilt angles. This local differentiation of structural quality resolves the contradiction between stiffness and flexibility.
2Area of moving object
If the size of the MEMS scanner is increased to achieve larger mirror diameter, then the field of view is improved, but the inertia increases requiring higher stiffness suspensions which limits the angular range
Solution Approach 1:
The multi-beam suspension structure segments the support function across multiple elements, allowing the system to support larger mirror diameters without proportionally increasing the stiffness of each individual support element. The distributed support structure manages the increased inertia of larger mirrors while maintaining acceptable tilt angles through the collective flexibility of multiple beams.
Solution Approach 2:
The suspension assembly extends in multiple spatial dimensions with central, outer, and interior support beams arranged in a three-dimensional configuration. This multi-dimensional arrangement allows the system to support larger mirrors by distributing loads across different spatial dimensions, managing inertia effects without requiring excessive stiffness in any single dimension, thus preserving angular range.
3Productivity
If high stiffness suspensions are used to maintain operating frequency above 2 kHz, then the refresh rate is improved, but the maximum angular range is limited
Solution Approach 1:
The suspension assembly segments the stiffness function across multiple support beams, allowing the system to achieve high refresh rates (operating frequency above 2 kHz) through the combined stiffness of the multi-beam structure while each individual beam maintains sufficient flexibility to permit maximum angular ranges of 10 degrees or more.
Solution Approach 2:
Different support beams are configured with local structural qualities optimized for their specific roles. The central support beam and outer support beams provide the stiffness necessary for high refresh rates, while the interior support beams and their connection geometries are designed to allow greater angular excursions. This local differentiation enables simultaneous achievement of high productivity and adequate angular range.
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 enables high resonance frequencies and dynamic performance, allowing for robust operation against vibrations and increased scanning capabilities, effectively addressing the limitations of existing MEMS scanners by optimizing the suspension design to balance mechanical stress and angular range.
Implementation Method 1
a suspension assembly mechanically coupled to and between the oscillator structure and the frame, the suspension assembly configured to suspend the oscillator structure within the frame recess
Implementation Method 2
the central support beam twists about the rotation axis as the oscillator structure oscillates
Data Source
AI summary
A microelectromechanical system (MEMS) device including an oscillator structure configured to oscillate about a rotation axis; a frame that is rotationally fixed, the frame including a frame recess within which the oscillator structure is suspended; and a suspension assembly mechanically coupled to and between the oscillator structure and the frame, the suspension assembly configured to suspend the oscillator structure within the frame recess. The suspension assembly includes a central support beam that extends lengthwise along the rotation axis, the central support beam being mechanically coupled to and between the oscillator structure and the frame; a first outer support beam mechanically coupled to the oscillator structure and laterally displaced from the central support beam in a first direction orthogonal to the rotation axis; and at least one first interior support beam directly coupled to and between the central support beam and the first outer support beam.