Asymmetrical MEMS Mirror Layout to Prevent Light Beam Clipping
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Solution Overview
Problem
Microelectromechanical mirror devices face challenges in reducing size and optimizing the arrangement of tiltable mirror structures to minimize space occupation, particularly in applications like virtual and augmented reality, while avoiding light beam clipping issues.
Innovation Solution
The device features asymmetrical tiltable mirror structures with varying torsional stiffness and a compact design, including a reinforcement structure and optimized die patterning, to reduce size and enhance arrangement, utilizing piezoelectric actuation for efficient light beam direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of tiltable mirror structures is reduced, then area occupation is minimized, but light beam clipping occurs
Solution Approach 1:
The patent applies asymmetry by designing the tiltable mirror structure with non-uniform thickness distribution. The support portion has greater thickness than the mirror surface portion, creating an asymmetric cross-section that optimizes both structural strength and optical performance. This asymmetric design allows the light beam to clear the structure edges without clipping while maintaining compact dimensions.
Solution Approach 2:
The patent transitions from a two-dimensional planar design to a three-dimensional optimized structure by varying the thickness in the vertical dimension. The support portion extends deeper into the substrate than the mirror surface, creating a stepped profile that clears the light beam path in three-dimensional space while minimizing the footprint area.
2Area of stationary object
If compact design is implemented, then space occupation is reduced, but structural reinforcement is compromised
Solution Approach 1:
The asymmetric thickness distribution concentrates material where structurally necessary - the support portion has greater thickness to provide mechanical reinforcement and anchoring strength, while the mirror surface portion remains thin for optical performance and compactness. This resolves the contradiction between compact size and structural strength.
Solution Approach 2:
The patent applies local quality by giving different thickness characteristics to different portions of the same structure. The support portion has high thickness for strength, while the mirror surface has low thickness for compactness and optical quality. Each region has the property it needs locally, achieving both compact overall size and adequate structural reinforcement.
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 achieves reduced area occupation, avoids light projection clipping, and maintains efficient light beam direction with low power consumption, suitable for compact devices like augmented reality glasses and picoprojectors.
Implementation Method 1
a driving structure coupled to the tiltable element for rotation around the first horizontal axis with a resonance movement
Implementation Method 2
a tiltable element carrying a reflecting region elastically suspended above the cavity
Implementation Method 3
a single torsional spring connected to the tiltable element and the frame, extending linearly along the first horizontal axis
Data Source
AI summary
A microelectromechanical device has a first tiltable mirror structure extending in a horizontal plane defined by first and second horizontal axes and includes a fixed structure defining a frame delimiting a cavity, a tiltable element carrying a reflecting region, elastically suspended above the cavity having first and second median axes of symmetry, elastically coupled to the frame by first and second coupling structures on opposite sides of the second horizontal axis. The first tiltable mirror structure has a driving structure coupled to the tiltable element to cause rotation around the first horizontal axis. The first tiltable mirror structure is asymmetrical with respect to the second horizontal axis and has, along the first horizontal axis, a first extension on a first side of the second horizontal axis, and a second extension greater than the first extension, on a second side of the second horizontal axis opposite to the first side.