Leaf Spring Openings for MEMS Mirror Resonance Control
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Solution Overview
Problem
MEMS scanning mirrors used in LIDAR applications face challenges in achieving lower resonance frequencies while maintaining robustness against vibrations and thermal loads, as high stiffness and low inertia designs make it difficult to reduce resonance frequencies without compromising mechanical stresses and optical performance.
Innovation Solution
The design incorporates leaf springs with openings that reduce torsional stiffness around the main rotation axis, allowing for a lower natural resonance frequency without significantly affecting stiffness around the optical axis, achieved by creating holes or openings in the leaf springs to decrease stiffness in one direction while maintaining it in others.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mirror body is made light and stiff with high stiffness suspension to achieve low inertia, then resonance frequency increases and dynamic performance improves, but it becomes difficult to design for lower resonance frequencies which are desirable for firing more laser pulses and reducing mechanical stresses
Solution Approach 1:
The leaf spring is designed with non-uniform thickness, being thickest at the center and thinner at the ends, creating localized variations in stiffness. This allows the suspension to have high stiffness where needed while enabling lower resonance frequencies through reduced stiffness in specific regions, resolving the contradiction between productivity and speed parameters.
Solution Approach 2:
The invention changes the geometric parameters of the leaf spring, specifically the thickness distribution along its length. By making the thickness variable rather than uniform, the resonance frequency can be adjusted to lower values while maintaining the necessary suspension stiffness, enabling higher productivity through more laser pulses per scan.
2Reliability
If the leaf spring has high torsional stiffness to maintain robustness against vibrations, then mechanical robustness improves, but resonance frequency increases making it difficult to operate at lower frequencies
Solution Approach 1:
The variable thickness design of the leaf spring creates local stiffness variations that allow high torsional stiffness for vibration robustness while enabling lower overall resonance frequency, resolving the contradiction between reliability and speed parameters.
3Weight of moving object
If the mirror body uses a thin mirror with reinforcement structure to achieve low inertia, then weight decreases and dynamic performance improves, but mechanical stresses increase
Solution Approach 1:
By changing the thickness parameter of the leaf spring from uniform to variable, the mechanical stress distribution is optimized. The thicker center region handles higher stresses while the thinner end regions reduce overall weight, resolving the contradiction between weight and stress parameters.
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 enables the production of slower MEMS mirror devices with reduced mechanical stresses and increased capability for firing more laser pulses in a single scan, while maintaining robustness against vibrations and thermal loads.
Implementation Method 1
at least one leaf spring providing torsional stiffness with respect to a rotation of the mirror body around the rotational axis
Data Source
AI summary
A mirror device includes a frame, a mirror body arranged in the frame and rotatable around a rotation, support beams connected between the mirror body and the frame and a leaf spring providing torsional stiffness with respect to a rotation of the mirror body around the rotational axis. The leaf spring has a maximum thickness that is smaller than a minimum width thereof, where the leaf spring has openings that reduce the thickness thereof or the penetrate the leaf spring in the thickness direction.