Capacitively Controlled Fabry-Perot Interferometer Mirror Gap Adjustment
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Solution Overview
Problem
Micromechanical Fabry-Perot interferometers face challenges with existing actuation mechanisms that consume significant surface area and require numerous processing steps, limiting the accuracy and efficiency of mirror gap adjustment.
Innovation Solution
A capacitively controlled Fabry-Perot interferometer is implemented, utilizing direct electrostatic attractive forces between mirrors with capacitively coupled control electrodes to adjust the mirror gap, allowing for precise control over a broad range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If MEMS actuators are used to move the mirror, then the mirror gap can be adjusted, but the actuators consume significant surface area and require many additional processing steps
Solution Approach 1:
The patent extracts the control functionality from separate MEMS actuators and integrates it directly into the mirror structure itself. The mirror is designed with a conductive layer that can be directly actuated by control electrodes, eliminating the need for additional actuator components and their associated processing steps.
Solution Approach 2:
The patent merges the mirror and actuator functions into a single integrated structure. The mirror contains a conductive layer that serves both as the reflective surface and as the actuated element, while control electrodes are positioned to directly influence the mirror's position through electrostatic forces, combining what were previously separate components.
2Measurement precision
If control electrodes are capacitively coupled to the mirror, then the mirror gap can be adjusted over a broad range with high accuracy, but the electrostatic attractive force requires precise control
Solution Approach 1:
The patent implements feedback control by monitoring the capacitance between the control electrodes and the mirror, which changes as the mirror gap is adjusted. This capacitance information is used to control the voltage applied to the electrodes, enabling precise and stable positioning of the mirror throughout a broad range of gap values.
Solution Approach 2:
The patent utilizes changes in capacitance as a function of mirror gap distance to enable precise control. By measuring the capacitance between the control electrodes and the mirror, the system can determine the exact gap position and adjust the electrostatic force accordingly to achieve the desired precision.
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 solution enables accurate and efficient adjustment of the mirror gap, enhancing the interferometer's ability to select specific wavelengths of electromagnetic radiation, while minimizing surface area usage and processing complexity.
Implementation Method 1
actuating relative movement between the bottom mirror and top mirror with a direct electrostatic attractive force between the two mirrors
Implementation Method 2
The electric potential of at least one of the two mirrors is set through a capacitively coupled control electrode
Data Source
AI summary
This disclosure describes a capacitively controlled Fabry-Perot interferometer which comprises a first mirror layer with a first metallic thin-film layer embedded in a first insulating layer and a second mirror layer with a second metallic thin-film layer embedded within a second insulating layer. A control region in the first metallic thin-film layer is at least partly aligned in an actuation direction with a control region in the second metallic thin-film layer. The interferometer also comprises a first control electrode and a first dielectric layer, and the first dielectric layer lies between the first control electrode and at least a part of the control region of the first metallic thin-film layer.