Multi-hinge Mirror Assembly for MEMS Scanners
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Solution Overview
Problem
Large MEMS-based mirrors face challenges in maintaining stiffness to avoid internal vibrational modes, leading to loss of optical quality and precision in reflected beams.
Innovation Solution
The solution involves breaking down large mirrors into smaller, separately hinged mirrors connected by rigid struts to ensure synchronization, with torsion hinges and anchors on a substrate, preventing undesirable vibrational modes and reducing inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If large MEMS-based mirrors are used to maintain optical coverage, then the mirror area is sufficient, but internal vibrational modes occur leading to loss of optical quality and precision
Solution Approach 1:
The large mirror is divided into multiple smaller mirror elements (first mirror, second mirror, third mirror) that are separately hinged to the substrate. Each mirror element has its own torsion hinges, preventing internal vibrational modes while collectively providing sufficient optical coverage area.
2Manufacturing precision
If multiple mirrors are used to eliminate vibrational modes, then optical quality is maintained, but the device complexity increases
Solution Approach 1:
Multiple mirror elements are connected through rigid struts that link them together, forming a synchronized assembly. The struts ensure all mirrors rotate in unison about a common axis, maintaining simplicity in control while eliminating individual mirror vibrations through the combined structure.
Solution Approach 2:
The rigid struts serve multiple functions: they connect adjacent mirror elements, provide structural support, and synchronize the rotation of all mirrors about the common axis. This multi-functionality reduces the need for additional synchronization mechanisms, managing device complexity.
3Use of energy by moving object
If smaller mirrors are used to reduce inertia, then the energy required to maintain angular range is reduced, but the mirror area decreases
Solution Approach 1:
The total mirror area is segmented into multiple smaller mirror elements. Each element has reduced mass and moment of inertia, requiring less energy to rotate individually. The collective area of all elements combined maintains the necessary optical coverage, resolving the contradiction between small size and sufficient area.
Solution Approach 2:
The multiple small mirror elements are optically combined to function as a single large mirror system. When all elements are synchronized in position and orientation, they collectively provide the required mirror area for optical coverage while each individual element maintains low inertia for energy-efficient actuation.
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 eliminates internal vibrational modes, maintains precise angular synchronization, and reduces the energy required to maintain angular range and frequency, enhancing optical quality and precision.
Implementation Method 1
First and second torsion hinges extend along the axis of rotation and connect the first mirror to the substrate on opposing sides of the first mirror so that the first mirror rotates on the first and second torsion hinges about the axis of rotation
Data Source
AI summary
A scanning device includes a substrate, which is etched to define a recess in the substrate and to define the following structures contained in the recess: At least first and second mirrors are disposed along a common axis of rotation. Torsion hinges extend collinearly along the axis of rotation and connect the first and second mirrors to the substrate so that the first and second mirrors rotate on the torsion hinges about the axis of rotation. Rigid struts are disposed alongside the axis of rotation and connect the first mirror to the second mirror so that the struts rotate about the axis of rotation together with the first and second mirrors.