Decoupled MEMS Micromirror Hinge Design for Cross-Coupling Reduction
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Solution Overview
Problem
Existing MEMS micromirror devices face issues with cross-coupling and pistoning effects due to weaker X-hinges, leading to reduced reliability and increased sensitivity changes when tilting about orthogonal axes, which complicates calibration and control, and makes them more susceptible to shock and vibration.
Innovation Solution
The design decouples mechanical loads between hinges for tilting about two orthogonal axes, using stronger Y-hinges to reduce cross-coupling and pistoning effects, and increases the area of rotor and stator electrodes to enhance electrostatic force, allowing for stronger hinges and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If weaker X-hinges are used to enable tilting about orthogonal axes, then the device can achieve two-axis tilting capability, but cross-coupling and pistoning effects increase leading to reduced reliability
Solution Approach 1:
The device segments the tilting mechanism into two independent hinge systems: stronger Y-hinges for primary tilting and weaker X-hinges for secondary tilting. This segmentation allows each hinge type to be optimized for its specific function, with Y-hinges providing structural strength and X-hinges enabling the required two-axis capability without compromising overall reliability.
Solution Approach 2:
Different hinge strengths are applied locally to different axes: Y-hinges are designed with higher strength and stiffness to minimize cross-coupling, while X-hinges are designed with lower strength to enable smooth tilting about the orthogonal axis. This local differentiation of mechanical properties resolves the contradiction between achieving two-axis capability and maintaining reliability.
2Area of stationary object
If smaller electrode area is used to reduce device size, then the device footprint is reduced, but electrostatic force decreases requiring weaker hinges
Solution Approach 1:
The electrode geometry parameters are optimized to maximize electrostatic force generation within a compact footprint. By adjusting electrode area, spacing, and configuration, sufficient electrostatic force is achieved for reliable actuation without requiring larger device dimensions, thereby avoiding the need for weaker hinges.
3Measurement precision
If stronger hinges are used to reduce cross-coupling, then tilting precision improves, but the device becomes more susceptible to shock and vibration
Solution Approach 1:
The hinge system is segmented into Y-hinges with higher stiffness for precision tilting and X-hinges with lower stiffness that can accommodate shock and vibration. This segmentation allows the Y-hinges to provide the necessary tilting precision while the X-hinges act as compliant elements that absorb mechanical shocks without transmitting them to the optical element.
Solution Approach 2:
The weaker X-hinges serve as a cushioning mechanism that absorbs shock and vibration before it can affect the optical element. By designing these hinges with lower strength, they deform preferentially under shock loads, protecting the more precision-critical Y-hinge system and the optical element from damage.
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 design reduces cross-coupling and pistoning effects by an order of magnitude, increases the actuator area by at least 50%, and enhances the overall reliability of the tiltable MEMS micromirror device by using stronger hinges and reducing sensitivity changes.
Implementation Method 1
a first stator electrode positioned on the substrate beneath the first or the second actuator region, for tilting the gimbal structure and the platform about the first axis; and a second stator electrode positioned on the substrate beneath the third actuator region, for tilting the platform relative to the gimbal structure about the second axis
Data Source
AI summary
A two-axis tiltable linear array of MEMS micromirrors is described. The individual micromirrors of the array are flexibly suspended over a common substrate by using two pairs of serpentine hinges coupled by a gimbal ring and are actuated by using tilt and roll electrodes. The tilt actuator regions of the micromirrors are disposed within the gimbal rings, the roll hinges connecting the tilt actuator regions to the micromirrors, which provides for decoupling of the tilt and the roll of the micromirror. The structure allows for considerable decoupling of the tilt and the roll and, or the pistoning effects observed upon micromirror actuation. The structure is suitable for application in a wavelength selective optical switch.