Self-Calibrating MEMS Mirror Positioning via Capacitive Sensing
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Solution Overview
Problem
Existing optical interferometers face challenges in accurately determining the position of a moveable mirror without increasing system size, cost, and complexity, as traditional methods require bulky laser sources and additional interferometers.
Innovation Solution
A Micro-Electro-Mechanical System (MEMS) apparatus with a non-planar mirror and a MEMS actuator having variable capacitance, coupled with a capacitive sensing circuit and a calibration module, allows for self-calibration of mirror positioning by mapping stored capacitances to mirror positions, reducing the need for external interferometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser and auxiliary interferometer are used to measure the moving mirror position, then the measurement precision is improved, but the device complexity and size increase
Solution Approach 1:
The patent implements self-calibration by using the interferometer's own optical components and detected interferograms to determine mirror position, eliminating the need for external laser sources and auxiliary interferometers. The system uses its inherent optical path and detected interference patterns to calibrate and measure position autonomously
Solution Approach 2:
The patent extracts and removes the external laser source and auxiliary interferometer from the system, retaining only the essential interferometer components needed for operation. This extraction eliminates the bulky external measurement equipment while preserving the core interferometric measurement capability
2Measurement precision
If a laser and auxiliary interferometer are used to measure the moving mirror position, then the measurement precision is improved, but the device size increases
Solution Approach 1:
The system uses its own optical path and detected interferograms for self-calibration, eliminating the need for separate external laser sources and auxiliary interferometers that would increase system size. The calibration is performed using the interferometer's inherent components
Solution Approach 2:
The patent removes the external laser source and auxiliary interferometer from the system configuration, keeping only the minimal interferometer components required for operation. This extraction significantly reduces the overall system size while maintaining measurement precision
3Measurement precision
If a laser and auxiliary interferometer are used to measure the moving mirror position, then the measurement precision is improved, but the manufacturing cost increases
Solution Approach 1:
The patent implements self-calibration using the interferometer's own optical components and detected signals, eliminating the need for expensive external laser sources and auxiliary interferometer equipment. This self-sufficient approach reduces component costs and system complexity
Solution Approach 2:
The patent extracts and removes the costly external laser source and auxiliary interferometer from the system, retaining only the essential interferometer components. This reduction in component count and complexity directly lowers manufacturing and acquisition costs
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 cost-effective determination of mirror position within a compact MEMS interferometer system, enhancing the integration of interferometer/spectrometer systems on small chips and reducing system complexity.
Implementation Method 1
A capacitive sensing circuit coupled to the MEMS actuator for sensing the capacitance of the MEMS actuator at multiple reference positions of the moveable mirror
Implementation Method 2
an interferogram produced by the interferometer based on the non-planar surface
Data Source
AI summary
A Micro-Electro-Mechanical System (MEMS) apparatus provides for self-calibration of mirror positioning of a moveable mirror of an interferometer. At least one mirror in the MEMS apparatus includes a non-planar surface. The moveable mirror is coupled to a MEMS actuator having a variable capacitance. The MEMS apparatus includes a capacitive sensing circuit for determining the capacitance of the MEMS actuator at multiple reference positions of the moveable mirror corresponding to a center burst and one or more secondary bursts of an interferogram produced by the interferometer based on the non-planar surface. A calibration module uses the actuator capacitances at the reference positions to compensate for any drift in the capacitive sensing circuit.