Micro-Oscillating Comb Electrodes for Precise Micromirror Motion
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Solution Overview
Problem
Micromirror elements manufactured by surface micromachining technology face challenges in achieving high optical flatness over large areas due to thin and susceptible mirror surfaces, while bulk micromachining technology provides rigidity but struggles with precise control of electrostatic attraction and residual vibrations during starting and stopping operations.
Innovation Solution
The design incorporates a micro-oscillating element with a frame, a movable functional portion, and comb-tooth electrodes with a laminate structure of conductors and insulators, where the electrodes overlap in the thickness direction at 0° rotational displacement, allowing for effective electrostatic attraction and precise control of the oscillating motion, reducing residual vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If surface micromachining technology is used to manufacture micromirror elements, then the manufacturing process is simpler and more suitable for mass production, but the mirror surface becomes thin and susceptible to warp, making it difficult to achieve high optical flatness over large areas
Solution Approach 1:
The patent employs a composite structure combining a thick substrate layer (providing rigidity and flatness) with a thin mirror film layer (providing reflective function). The substrate is formed by bulk micromachining to ensure high flatness, while the mirror film is deposited on this rigid base to achieve both structural stability and optical functionality.
Solution Approach 2:
The patent transitions from purely surface-level micromachining to bulk micromachining by etching into the substrate thickness dimension. This allows the mirror support structure to extend vertically into the substrate, providing mechanical rigidity and flatness support that surface micromachining alone cannot achieve.
2Manufacturing precision
If bulk micromachining technology is used to manufacture micromirror elements, then the mirror surface achieves high optical flatness and rigidity, but the comb-tooth electrodes are apart from each other, making it difficult to generate sufficient electrostatic force and control oscillating motion precisely
Solution Approach 1:
The patent implements a multi-layer nested electrode structure where comb-tooth electrodes are arranged in multiple tiers at different vertical positions. The first comb-tooth electrode is positioned closer to the movable mirror support, while the second comb-tooth electrode is positioned farther away. This nesting approach allows electrostatic force to be generated effectively at multiple levels, improving both force magnitude and control precision.
Solution Approach 2:
The patent utilizes the vertical thickness dimension of the bulk substrate to position comb-tooth electrodes at different heights. By etching electrode structures into the substrate at multiple depth levels, the design creates three-dimensional electrode arrangements that maintain close spacing for strong electrostatic coupling while preserving the overall structural rigidity of the bulk micromachined device.
3Device complexity
If conventional comb-tooth electrodes are used in bulk micromachined elements, then the structure is simple, but the electrodes are apart from each other during non-operation, causing residual vibrations and poor controllability during starting and stopping operations
Solution Approach 1:
The patent positions the comb-tooth electrodes in advance during the bulk micromachining process so that they are already in close proximity before the device operates. The electrode structures are pre-formed at specific locations and orientations, ensuring that when voltage is applied, electrostatic force is immediately effective without requiring preliminary movement or adjustment, thereby eliminating residual vibrations and improving response control.
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 controllability and accuracy of the oscillating motion, enabling quick and precise operation of the movable functional portion, suitable for high-speed driving and reducing residual vibrations.
Implementation Method 1
a first comb-tooth electrode and a second comb-tooth electrode for generation of a driving force for the oscillating motion
Data Source
AI summary
A micro-oscillating element includes a frame, a movable functional portion, and a torsional joint for joining the frame and the functional portion. The micro-oscillating element also includes first and second comb-tooth electrodes for generation of the driving force for the oscillating motion of the movable functional portion about the torsional joint. The first comb-tooth electrode includes a plurality of first electrode teeth each having a first conductor, an insulator and a second conductor laminated in the direction of the oscillating motion, where the first conductor and the second conductor are electrically connected with each other. The second comb-tooth electrode includes a plurality of second electrode teeth caused not to face the second conductor but to face the first conductor of the first electrode teeth during non-operation. The second electrode teeth are longer than the first conductor in the direction of the oscillating motion.