Waveguide Grating Optical Displacement Sensor
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Solution Overview
Problem
Conventional optical position sensing systems are prone to detection errors due to vibrations and require high stability, and existing systems using air hole arrays are lengthy and sensitive to electromagnetic interferences.
Innovation Solution
An optical displacement sensing system utilizing a broadband light source, fiber collimator, optical sensor with a waveguide grating, and optical spectrum analyzer, which generates reflected light with a resonance wavelength to distinguish positions without the need for an optical encoder or specific phase light, and is insensitive to electromagnetic interferences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical encoder with diffraction pattern is used for position sensing, then position detection can be achieved, but the system is sensitive to vibrations and produces detection errors
Solution Approach 1:
The patent replaces the conventional mechanical/optical encoder system with a waveguide grating-based optical sensing system. Instead of using diffraction patterns from moving gratings, the invention uses resonance wavelength detection in waveguide structures, eliminating the need for precise mechanical positioning and reducing vibration sensitivity.
Solution Approach 2:
The system changes the detection parameter from spatial diffraction patterns to spectral resonance wavelengths. By measuring wavelength shifts in the resonance spectrum rather than positional changes in diffraction patterns, the system achieves vibration immunity while maintaining measurement precision.
2Measurement precision
If air hole arrays are used for displacement sensing, then displacement detection can be achieved, but the system length is elongated
Solution Approach 1:
The waveguide grating structure integrates multiple functional elements within a compact volume. The grating periods are embedded within the waveguide core, allowing the sensing function to be nested within the existing waveguide structure rather than requiring separate array components, thus reducing overall system length.
Solution Approach 2:
The invention transitions from a spatial arrangement of air hole arrays to a spectral domain detection method. By encoding displacement information in wavelength dimension rather than spatial dimension, the system achieves the same measurement capability with a more compact physical footprint.
3Measurement precision
If air hole arrays are used for displacement sensing, then displacement detection can be achieved, but the system becomes sensitive to electromagnetic interferences
Solution Approach 1:
The patent replaces electromagnetic field-based detection with optical resonance-based detection in dielectric waveguides. The waveguide grating structure confines and guides optical fields, providing immunity to external electromagnetic interferences that would affect conventional electromagnetic sensing methods.
4Measurement precision
If conventional optical position sensing system is used, then position detection can be achieved, but the system complexity and cost increase
Solution Approach 1:
The waveguide grating structure serves multiple functions simultaneously: it acts as both the sensing element and the optical waveguide, eliminating the need for separate components. This multi-functionality reduces system complexity and component count while maintaining measurement precision.
Solution Approach 2:
The waveguide grating structure is self-resonant, meaning it naturally produces the resonance condition without requiring external modulation or complex control mechanisms. The structure itself provides the sensing mechanism through its inherent optical resonance properties, simplifying the overall system design.
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 micrometer-scale or nanometer-scale displacement detection with reduced system length and cost, and improved stability, allowing for efficient position differentiation based on resonance wavelengths.
Implementation Method 1
The waveguide grating is configured to be resonated by the received incident light, and to form a reflected light with a resonance wavelength and emitted to the sensing terminal
Implementation Method 2
the waveguide grating is configured to be resonated by the received incident light, and to form a reflected light with a resonance wavelength
Implementation Method 3
the fiber collimator includes an input terminal, a sensing terminal and an output terminal; and the input terminal is coupled to the broadband light source and configured to receive the incident light, and the sensing terminal is configured to transmit the incident light
Implementation Method 4
The optical spectrum analyzer is coupled to the output terminal to display a spectrum of the reflected light
Data Source
AI summary
An optical displacement sensing system is provided. With configuration of an optical sensor disposed on a displacement platform and in cooperation with a broadband light source and an optical spectrum analyzer, when the displacement platform moves, the waveguide grating of the optical sensor is resonated and the reflected light provided with a resonance wavelength is formed. The waveguide grating has the plurality of grating periods, and when the displacement platform moves to a different position to make the broadband light source correspond to a different grating period, the position can correspond to the different resonance wavelength. Therefore, according to the aforementioned configuration, the position is determined according to the different resonance wavelength, instead of using an optical encoder; furthermore, the micrometer-scale or nanometer-scale displacement detection is achieved.