Foreign Object Debris Discrimination Using Modulated Laser Light
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Solution Overview
Problem
Existing foreign object debris (FOD) discrimination systems struggle to effectively detect and classify smaller, complexly shaped FOD, such as sand grains, due to their subtle damage mechanisms and interference from reflective and transient environmental conditions like moisture, fog, dust, ash, or smoke.
Innovation Solution
A method involving the illumination of particles within a sensing volume with a modulated electromagnetic radiation pulse, followed by the analysis of the scattered return signals to classify particle position, velocity, and electromagnetic characteristics based on the amplitude and frequency of the mixed signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-wavelength, multi-angle scattering light sources and sensors are used to identify FOD, then scattering cross sections can be provided, but the system cannot effectively detect smaller FOD with complex geometries and is affected by reflective and transient environmental conditions
Solution Approach 1:
The patent introduces a modulated laser beam as an intermediary that actively interacts with FOD particles. The laser light is modulated at a known frequency, and the scattered light is detected and mixed with the reference signal. This intermediary approach enables the system to overcome environmental interference by using the modulated signal as a reference, allowing precise detection of smaller FOD particles through their unique scattering signatures.
Solution Approach 2:
The patent changes the parameters of the light source by using modulated laser light instead of conventional continuous light. The modulation frequency and amplitude are controlled parameters that can be adjusted to optimize detection. By varying these parameters, the system can distinguish FOD particles from environmental interference and accurately characterize particles of different sizes and compositions.
2Measurement precision
If conventional optical sensors are used to detect FOD, then scattering cross sections can be measured, but smaller particles like sand grains cause damage that is barely visible and difficult to detect
Solution Approach 1:
The patent replaces conventional mechanical or simple optical detection systems with a sophisticated optical measurement system based on light modulation and interference. The modulated laser beam creates an interference pattern when scattered light is mixed with the reference signal, enabling detection at the level of individual small particles. This substitution of detection methodology dramatically improves sensitivity to particles as small as sand grains.
Solution Approach 2:
The modulated laser beam serves as an intermediary that amplifies the detection capability for small particles. By modulating the laser and using the scattered light as a reference signal, the system creates an interference pattern that enhances the visibility of particles even when they cause only minimal damage. This intermediary approach makes previously undetectable small particles measurable.
3Measurement precision
If modulated electromagnetic radiation is used to illuminate particles, then particle characteristics can be classified, but the system complexity increases
Solution Approach 1:
The modulated laser beam serves multiple functions simultaneously: it illuminates the particles, provides a reference signal for interference, and enables classification of particle characteristics. The same laser source is used for both illumination and as a reference, reducing the need for separate components. This multi-functionality approach maintains high classification accuracy while minimizing the increase in system complexity.
Solution Approach 2:
The patent merges the illumination function and reference signal generation into a single modulated laser beam. Instead of using separate light sources for illumination and reference, the system combines these functions by modulating the laser beam and using the modulated signal as both the illumination source and the reference for interference measurements. This merging reduces system complexity while maintaining measurement 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 approach enables precise discrimination and classification of FOD, even in complex geometries and adverse environmental conditions, by utilizing the scattering information and Doppler shift analysis to determine particle characteristics and movement.
Implementation Method 1
receiving one or more electromagnetic radiation return signals that have been scattered by the particle illuminated by the modulated electromagnetic radiation pulse
Implementation Method 2
determining a velocity of the particle using the particle's Doppler shift from the frequency of the mixed signal fRS−fLS
Data Source
AI summary
A method of foreign object debris discrimination includes illuminating a particle located within a sensing volume with a modulated electromagnetic radiation pulse emitted from a source; receiving one or more electromagnetic radiation return signals that have been scattered by the particle illuminated by the modulated electromagnetic radiation pulse at a detector; mixing, using a controller, the electromagnetic radiation return signal of amplitude IRS and frequency fRS with a reference signal of amplitude ILS and frequency fRS; analyzing, using the controller, an amplitude of the mixed signal √{square root over (ILSIRS)}, and frequency of the mixed signal, fRS−fLS; and classifying, using the controller, a particle position, a velocity, and electromagnetic characteristic of the particle based on the amplitude, √{square root over (ILSIRS)}, and frequency, fRS−fLS, of the mixed signal.