MEMS Mirror Magnetic Field Sensing for Tilt Angle
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Solution Overview
Problem
Conventional MEMS mirrors face challenges in achieving precise tilting and monitoring of tilt angles, especially for larger angles and closely packed arrays, due to limitations in existing sensing technologies such as capacitive and piezoresistive sensing.
Innovation Solution
A MEMS mirror device that utilizes a cylindrical micro-magnet connected to a movable structure, with an arrangement of magnetic field sensors positioned below the micro-magnet to sense changes in the magnetic field distribution caused by the rotation of the micro-magnet, allowing for precise determination of the mirror's position and tilt angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If capacitive sensing electrodes are positioned beneath the movable mirror for position monitoring, then integration into MEMS process is achieved, but for large tilt angles large gap sizes are required which increase device size
Solution Approach 1:
The patent replaces the conventional capacitive sensing mechanism with a magnetic field-based sensing system. A magnet is integrated into the movable mirror structure, and magnetic field sensors are positioned in the fixed frame beneath the mirror. This substitution eliminates the need for large capacitive electrodes while maintaining MEMS process compatibility, as the magnetic components can be fabricated using standard MEMS techniques.
Solution Approach 2:
The invention changes the sensing parameter from electrical capacitance to magnetic field strength. By monitoring changes in magnetic field distribution rather than capacitance values, the system achieves accurate position sensing for large tilt angles without requiring large electrode areas, thus resolving the contradiction between sensing accuracy and device size.
2Area of stationary object
If comb-type capacitive electrodes are used for compact design, then device size is reduced, but sensitivity significantly decreases for larger tilt angles
Solution Approach 1:
The patent replaces comb-type capacitive electrodes with a magnetic field sensing system. The magnet attached to the movable mirror generates a magnetic field that is detected by fixed magnetic sensors in the substrate. This substitution maintains compact device dimensions while providing consistent sensitivity across the full tilt angle range, overcoming the limitation of capacitive sensors whose sensitivity degrades at larger angles.
3Measurement precision
If piezoresistive sensing is used for high tilt angle resolution, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent replaces complex piezoresistive sensing structures with a simpler magnetic field-based system. Instead of integrating piezoresistors into support springs and requiring complex Wheatstone bridge circuits, the invention uses a magnet and magnetic field sensors that can be implemented with standard MEMS processes, significantly reducing fabrication complexity while maintaining high tilt angle resolution.
4Measurement precision
If parallel-plate capacitive sensing is used for large tilt angles, then measurement range is extended, but electrode area must be very large which increases device size
Solution Approach 1:
The patent substitutes parallel-plate capacitive sensing with magnetic field sensing. The magnet固定在movable mirror上产生磁场，fixed magnetic sensors detect field changes as the mirror tilts. This approach enables large angle sensing without requiring large electrode areas, as the magnetic field extends over a larger spatial range compared to capacitive fields.
Solution Approach 2:
The invention changes the physical parameter being measured from capacitance to magnetic field strength. Magnetic field sensors can detect field variations over larger distances and angles compared to capacitive sensors, enabling large tilt angle measurement without the need for large electrode areas that would be required in capacitive systems.
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 precise and cost-effective monitoring of tilt angles, even for larger angles and closely packed arrays, with high sensitivity and resolution, overcoming the limitations of conventional sensing technologies.
Implementation Method 1
one cylindrical micro-magnet connected to the moveable structure; wherein a rotation of the moveable structure around the at least one axis of rotation rotates the micro-magnet around the same axis of rotation; and a fixed structure comprising an arrangement of two or more magnetic field sensors positioned at a certain distance below the micro-magnet
Data Source
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AI summary
The present disclosure describes a device, in particular a Micro-Electro-Mechanical-System (MEMS) mirror. The MEMS mirror device comprises a movable structure configured to rotate around at least one axis of rotation. Further, it comprises a micro-magnet connected to the moveable structure, wherein a rotation of the moveable structure around the at least one axis of rotation rotates the micro-magnet around the same axis of rotation. Further, the MEMS mirror device comprises a fixed structure comprising an arrangement of two or more magnetic field sensors positioned at a certain distance below the micro-magnet, wherein the arrangement of the magnetic field sensors is configured to sense a change of a magnetic field distribution caused by a rotation of the micro-magnet.