Split Beam Self-Mixing Interferometry for Particulate Matter Sensors
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Solution Overview
Problem
Conventional self-mixing interferometry sensors require multiple sensors oriented in different directions to estimate particulate matter concentration accurately, leading to increased cost, complexity, and power consumption due to the inability to measure particle speed perpendicular to the beam direction.
Innovation Solution
A single self-mixing interferometry sensor splits its optical emission into multiple beams, using diffractive or beam-shaping optical elements to direct each beam differently, allowing for the estimation of particle speed and concentration by combining speed information with beam geometry, thereby reducing the need for multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple self-mixing interferometry sensors are used oriented in different directions, then particle speed measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides a single optical beam into multiple beam segments using diffractive optical elements, creating multiple measurement regions from one sensor. This segmentation allows the single sensor to measure particle speeds in different directions simultaneously, resolving the contradiction by providing multi-directional measurement capability without requiring multiple sensors.
Solution Approach 2:
The patent introduces spatial dimensionality by creating multiple beams at different angles from a single source. By projecting beams in different directions within the same measurement volume, the system achieves three-dimensional particle speed measurement capability while maintaining a single-sensor architecture, thus improving measurement precision without increasing device complexity.
2Measurement precision
If multiple self-mixing interferometry sensors are used oriented in different directions, then particle speed measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The patent merges the functions of multiple sensors into a single sensor system by using optical beam splitting. The single self-mixing interferometry sensor processes multiple beam directions simultaneously, combining what would require separate sensors into one integrated system, thereby reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The single sensor system is designed to perform multiple measurement functions simultaneously - measuring particle speeds in different directions and estimating particulate matter concentration. This multi-functionality eliminates the need for separate dedicated sensors for each measurement type, reducing overall power consumption while improving concentration estimation accuracy through integrated multi-directional data.
3Device complexity
If a single sensor is used with beam splitting, then device complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent introduces diffractive optical elements as intermediaries between the single sensor and the measurement volume. These elements split and direct the optical beam into multiple paths, enabling the single sensor to effectively perform multi-directional measurements. The intermediary optical elements preserve measurement precision by creating distinct measurement regions while maintaining the simplicity of a single-sensor architecture.
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 enhances the accuracy of particulate matter concentration estimation while minimizing the size, cost, and power consumption of the sensor system, enabling efficient detection of PM10 and PM2.5 particles.
Implementation Method 1
coherent or partially coherent electromagnetic radiation emitted by a stimulated emission-based electromagnetic radiation source (e.g., a laser)
Implementation Method 2
The set of one or more optical elements may include one or more diffractive optical elements
Implementation Method 3
receive a reflection or backscatter of the electromagnetic radiation back into the optical resonant cavity
Implementation Method 4
self-mix the generated and reflected/backscattered electromagnetic radiation within the optical resonant cavity, and generate an output indicative of the self-mixing
Implementation Method 5
Such re-coupling induces a measurable phase-sensitive change (e.g., a Doppler frequency shift) in the electric field and carrier distribution of the optical resonant cavity
Implementation Method 6
The output of a self-mixing interferometry sensor may include a photocurrent produced by a photodetector (e.g., a photodiode)
Data Source
AI summary
Various sensors, including particulate matter sensors, are described. One particulate matter sensor includes a self-mixing interferometry sensor and a set of one or more optical elements. The set of one or more optical elements is positioned to receive an optical emission of the self-mixing interferometry sensor, split the optical emission into multiple beams, and direct each beam of the multiple beams in a different direction. The self-mixing interferometry sensor is configured to generate particle speed information for particles passing through respective measurement regions of the multiple beams.