MEMS Mirror Suspension Layout for Wide-Angle Robust LiDAR Scanning
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Solution Overview
Problem
Existing MEMS scanning mirrors face a trade-off between mechanical stress, scan angle, and robustness due to the design limitations of torsion beams, which are exacerbated by vibrations and shocks, particularly in automotive LIDAR applications.
Innovation Solution
A MEMS-mirror device with a mirror body suspended by torsion beams that are geometrically parallel and centered around the rotation axis, allowing for a compact design with reduced tensile stress and non-linearity, and coupled with out-of-plane support beams for enhanced stiffness and resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cross-sectional area of torsion beams is increased to reduce mechanical stress, then the rotation angle increases, but the stiffness for other DOF decreases making the device less robust
Solution Approach 1:
The patent divides the single torsion beam into multiple parallel torsion beams (first plurality and second plurality). Each torsion beam has a smaller cross-sectional area, but collectively they provide the required rotational stiffness while maintaining individual beam strength and reducing mechanical stress through distributed load bearing.
Solution Approach 2:
The patent transitions from a single-plane torsion beam configuration to a three-dimensional arrangement with torsion beams distributed in multiple planes (first and second plurities at different positions). This spatial distribution allows the system to achieve both rotational flexibility and resistance to unwanted motions in multiple degrees of freedom.
2Strength
If the torsion beams are positioned away from the rotation axis to reduce mechanical stress, then the rotation angle increases, but tensile stress and non-linearity increase
Solution Approach 1:
The patent employs an asymmetric arrangement where torsion beams are positioned at different distances from the rotation axis in different planes. The first plurality of torsion beams and second plurality are arranged asymmetrically to optimize the balance between reducing mechanical stress and minimizing tensile stress and non-linearity.
Solution Approach 2:
Different torsion beams have different local properties - some are positioned closer to the rotation axis while others are farther away. Each torsion beam's position and cross-sectional area are locally optimized to achieve the desired balance between rotational flexibility and stress reduction.
3Speed
If multiple torsion beams are used to increase rotational stiffness, then the resonance frequency increases, but the device complexity increases
Solution Approach 1:
The patent combines multiple torsion beams into a unified suspension structure that collectively provides rotational stiffness. The first and second plurities of torsion beams are merged into a single functional unit that suspends the mirror body, achieving high resonance frequency while maintaining manufacturing simplicity through integrated design.
Solution Approach 2:
The multiple torsion beams serve multiple functions simultaneously: they provide rotational stiffness for scanning, support the mirror body, define the rotation axis, and suppress unwanted motions. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
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 a larger scan angle, reduced mechanical stress, and improved robustness against vibrations, facilitating precise control and smaller die size while maintaining high resonance frequency.
Implementation Method 1
an actuator, such as an electrostatic actuator, an electromagnetic actuator or a piezoelectric actuator to induce a rotation in the mirror body around the rotation axis
Implementation Method 2
an actuator, such as an electrostatic actuator, an electromagnetic actuator or a piezoelectric actuator to induce a rotation in the mirror body around the rotation axis
Implementation Method 3
an actuator, such as an electrostatic actuator, an electromagnetic actuator or a piezoelectric actuator to induce a rotation in the mirror body around the rotation axis
Implementation Method 4
The first and the second extension portion are each flexibly coupled at a lateral side to the support with a respective plurality of torsion beams
Implementation Method 5
These motions can be suppressed by a high translational stiffness in the corresponding direction, or a high rotational stiffness around the corresponding axis
Implementation Method 6
The torsion beams of a respective plurality of torsion beams have a respective first end that is attached to the support and a respective second end that is attached to the respective extension portion. The respective first end and the respective second end have mutually different positions in the direction of the longitudinal axis and in the lateral direction (x) are at mutually opposite sides (x1, x2) of the rotation axis.
Data Source
AI summary
A MEMS-mirror device (1) is provided that comprises a support (2), a mirror body (3) that is rotationally suspended with respect to the support along a rotation axis (4), and an actuator (7A,7B) to induce a rotation in the mirror body around the rotation axis. The mirror body (3) has a mirror surface (311) that in a neutral state defines a reference plane (x, y) having a longitudinal axis (y) through a center of the mirror body parallel to the rotation axis (4) and a lateral axis (x) transverse to the longitudinal axis. The mirror body (3) has a central portion (31) and integral therewith a pair of extension portions (32A, 32B) that extend in mutually opposite directions along the longitudinal axis. Each of the extension portions (32A, 32B) is flexibly coupled at a lateral side (322A, 322B) to the support with a respective plurality (6A, 6B) of torsion beams (61) which in a neutral state of the mirror body extend in the reference plane (x, y). The torsion beams of a respective plurality of torsion beams have a respective first end (611) attached to the support and a respective second end (612) attached to the respective extension portion, wherein the respective first end and the respective second end have mutually different positions (y1, y2) in the direction of the longitudinal axis (y) and in the lateral direction (x) are at mutually opposite sides (x1, x2) of the rotation axis (4).