LiDAR Micro-Mirror Assembly with Segmented Support for Linear Torque
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Solution Overview
Problem
Light steering systems, particularly in LiDAR modules, face challenges in maintaining linear torque control across a wide range of rotation angles due to varying spring stiffness, which complicates the control of micro-mirrors and increases the moment of inertia, leading to non-linear torque requirements and potential structural integrity issues.
Innovation Solution
The implementation of a micro-mirror assembly with flexible support structures that provide different resistive forces for different directions of movement, combined with a mechanical amplification scheme using frames and connection structures, reduces sheer deformation and moment of inertia, making the torque control more linear and efficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the micro-mirror is made thicker to increase structural strength, then the structural integrity is improved, but the moment of inertia increases leading to non-linear torque control
Solution Approach 1:
The micro-mirror is segmented into a thin mirror body and a separate support structure with ribs. The mirror itself is made thin (few micrometers) to reduce moment of inertia, while the support structure provides the necessary structural strength. This segmentation allows the mirror to rotate easily while maintaining structural integrity through the ribbed support framework.
Solution Approach 2:
The support structure features localized rib elements positioned strategically around the mirror periphery. These ribs provide concentrated structural support where needed (at the edges and pivot points) while leaving the central mirror area thin and lightweight. This local reinforcement approach maintains strength without adding unnecessary mass to the rotating portion.
2Strength
If high spring stiffness is used in connection structures to maintain structural integrity, then the structural integrity is improved, but the torque becomes non-linear with respect to rotation angle
Solution Approach 1:
The connection structures use flexible hinges and elastic deformation zones that provide dynamic, adaptive stiffness. Rather than rigid high-stiffness connections, the system employs compliant mechanisms that deform elastically during rotation, allowing the connection to maintain structural integrity while accommodating rotation with more linear torque characteristics.
Solution Approach 2:
The connection structures are designed with varying geometric parameters along their length, creating a gradient of stiffness. The structures are more rigid at the substrate attachment points and progressively more flexible toward the mirror, allowing them to maintain overall structural integrity while enabling easier rotation with reduced non-linearity in the torque-rotation relationship.
3Device complexity
If the moment of inertia is reduced to simplify torque control, then the torque control linearity is improved, but the structural integrity may be compromised
Solution Approach 1:
The system is divided into a thin, lightweight mirror element for easy rotation and a separate, thicker support structure for structural strength. The mirror itself is only a few micrometers thick to minimize moment of inertia, while the support structure contains the heavier rib elements that provide structural integrity without participating in the rotation.
Solution Approach 2:
The support structure acts as an intermediary between the thin mirror and the substrate. It provides the necessary structural strength and rigidity while allowing the thin mirror to rotate with minimal moment of inertia. The support structure mediates between the conflicting requirements of strength and low inertia by bearing the structural loads while permitting easy rotation of the mirror.
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 approach simplifies the control of micro-mirrors by ensuring a more linear relationship between torque and rotation angle, reduces the moment of inertia, and enhances the structural integrity of the pivot points, improving the overall performance and accuracy of light steering systems.
Implementation Method 1
the actuator being configured to generate an electrostatic force between the first fingers and the second fingers to rotate the micro-mirror
Implementation Method 2
The connection structure can be deformed to accommodate the rotation, but the connection structure also has a degree of spring stiffness which varies with the rotation angle
Data Source
AI summary
In one example, an apparatus that is part of a Light Detection and Ranging (LiDAR) module of a vehicle comprises a semiconductor integrated circuit comprising a microelectromechanical system (MEMS) and a substrate. The MEMS comprises an array of micro-mirror assemblies, each micro-mirror assembly comprising: a micro-mirror having a first thickness; and an actuator comprising first fingers and second fingers, the first fingers being connected with the substrate, the second fingers being mechanically connected to the micro-mirror having a second thickness smaller than the first thickness, the actuator being configured to generate an electrostatic force between the first fingers and the second fingers to rotate the micro-mirror to reflect light emitted by a light source out of the LiDAR module or light received by the LiDAR module to a receiver.