MEMS Scanning Micromirror Decoupled Torsional Stiffness
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Solution Overview
Problem
MEMS scanning micromirrors suffer from image quality issues due to undesired mirror motion and deformation, primarily caused by the torsion beams being the sole point of attachment, which affects suspension stiffness and resonant frequencies, leading to reduced image resolution and quality.
Innovation Solution
The design incorporates a mirror body with a rotation axis supported by a pair of extension bars and cantilever beam assemblies, along with vertical support beams that decouple torsional stiffness from out-of-plane rocking and vertical mode stiffness, allowing for independent adjustment of resonant frequencies and reducing dynamic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If torsion beams are used as the sole point of attachment between mirror plate and frame, then the mirror plate is supported and torsional stiffness is provided, but out-of-plane rocking and vertical translation resonant modes reduce image quality
Solution Approach 1:
The suspension system is segmented into multiple independent beam assemblies (first and second beam assemblies) with distinct functional specializations. Each assembly handles specific degrees of freedom, separating torsional support from vertical and rocking support functions, thereby eliminating the coupled detrimental resonant modes while maintaining required stiffness properties.
Solution Approach 2:
Different beam assemblies are designed with locally optimized properties: some beams are configured to provide torsional stiffness while others are optimized for vertical and rocking support. This local differentiation allows each component to excel at its specific function without compromising overall system performance or introducing harmful resonances.
2Manufacturing precision
If larger scanning angles are used to increase image resolution, then image resolution improves, but stress in the torsion beam increases
Solution Approach 1:
The load path is segmented across multiple beam assemblies with specialized functions. By separating torsional support from other support functions, the system can achieve larger scanning angles with reduced stress concentration in any single beam, as the torsional load is distributed and managed by dedicated beam assemblies optimized for this purpose.
3Manufacturing precision
If higher scanning frequencies are used to increase image resolution, then image resolution improves, but micromirror dynamic deformation increases
Solution Approach 1:
The suspension system is divided into multiple beam assemblies that independently manage different degrees of freedom. This segmentation allows each assembly to be optimized for its specific function, reducing coupled vibrations and dynamic deformations that would otherwise occur in a unified torsion beam design, thereby enabling higher scanning frequencies with minimal mirror deformation.
Solution Approach 2:
Different beam assemblies are locally optimized for specific functions: torsional beams are designed for rotational stiffness while other beams are optimized for vertical and rocking support. This local optimization ensures that each component responds appropriately to its specific load type, minimizing overall dynamic deformation even at high scanning frequencies.
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 configuration enhances image quality by minimizing mirror deformation and allowing for higher image resolution, as the torsional stiffness is primarily provided by the cantilever beams, while the vertical support beams focus on supporting the mirror body without influencing torsional stiffness, thus improving the scanning micromirror's performance.
Implementation Method 1
a pair of cantilever beam assemblies, each of the pair of cantilever beam assemblies being fixed to one of the pair of opposed frame bars and coupled to one end of the pair of extension bars
Implementation Method 2
a pair of vertical support beams connected between each of the pair of opposed frame bars to the mirror body along the rotation axis
Data Source
AI summary
A MEMS scanning micromirror including a mirror body 50, the mirror body 50 having a rotation axis 58 with a pair of extension bars 56 parallel to the rotation axis 58; a frame 60 forming a mirror recess 62 with a recess periphery 64, the frame 60 having a pair of opposed frame bars 66 on the recess periphery 64 along the rotation axis 58; a pair of cantilever beam assemblies 70, each of the pair of cantilever beam assemblies 70 being fixed to one of the pair of opposed frame bars 66 and coupled to one end of the pair of extension bars 56; and a pair of vertical support beams 40 connected between each of the pair of opposed frame bars 66 to the mirror body 50 along the rotation axis 58.