Diffractive Grating Displacement Sensor for MEMS Lateral Motion
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Solution Overview
Problem
Existing displacement sensors are unable to accurately measure lateral movements between surfaces due to limitations in sensitivity, alignment, and nonlinear response, particularly when integrated with MEMS devices.
Innovation Solution
A miniaturized position sensor using deformable diffractive gratings with patterns on two surfaces, where the top surface has reflective grating lines and the bottom surface has etched grooves, allowing for modulation of diffraction efficiency with lateral displacement, measured by photodetectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitor structures and impedance measurements are used for displacement sensing, then the measurement can be implemented, but the sensitivity is insufficient and the solution becomes costly and complicated
Solution Approach 1:
The patent replaces traditional mechanical/capacitive displacement sensing with optical diffraction-based sensing. By using a diffractive grating structure illuminated by light, the system measures displacement through optical path length changes rather than electrical impedance, achieving higher sensitivity and simpler implementation suitable for MEMS integration.
Solution Approach 2:
The patent changes the measurement parameter from electrical impedance to optical diffraction efficiency. By monitoring how the diffracted light intensity varies with the position of the reflective surface, the system achieves more sensitive and linear displacement measurements compared to capacitive methods.
2Measurement precision
If optical position encoders with diffraction gratings are used, then lateral displacement can be detected, but the system becomes complex with multiple optical components
Solution Approach 1:
The patent extracts and eliminates unnecessary optical components from traditional encoder systems. By using a single diffractive grating structure that directly modulates light intensity based on surface position, the system removes the need for complex beam splitters, multiple mirrors, and interference fringe generation components while maintaining lateral displacement detection capability.
Solution Approach 2:
The patent uses a simplified optical copying approach where the position information is directly encoded in the intensity of diffracted light rather than requiring complex interference patterns. The diffractive grating creates a direct intensity modulation that copies positional information into optical signal strength, simplifying the readout mechanism.
3Measurement precision
If deformable diffractive structures are used for distance measurement, then the distance between surfaces can be measured, but lateral displacement cannot be detected
Solution Approach 1:
The patent makes the diffractive grating structure universal by designing it to respond to both normal distance changes and lateral displacements. The grating is positioned and oriented such that both types of movement modulate the diffracted light intensity, enabling a single structure to perform multiple measurement functions that would traditionally require separate sensing mechanisms.
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
Enables accurate measurement of lateral displacements with high sensitivity and dynamic range, suitable for integration with MEMS devices and applications like accelerometers and geophones, while simplifying the optical system.
Implementation Method 1
the first and second diffractive patterns being essentially equal and overlapping... adapted to diffract light within a chosen range of wavelengths
Data Source
AI summary
The present invention relates to a displacement sensor device and the system including the device, wherein the device comprises a first at least partially transparent plane surface with a first diffraction pattern and a second plane surface comprising a second reflecting diffraction pattern. The diffractive patterns being adapted to diffract light within a chosen range of wavelengths, the second surface being positioned below and parallel to the first surface constituting a pair wherein said first and second diffractive patterns being essentially equal, the device also comprising displacement means for allowing a movement in a direction parallel to said surfaces, the device thus providing a movement sensitive diffraction pattern.