Fully Compensated Optical Gas Sensing With Dual Collinear Paths
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Solution Overview
Problem
Existing optical gas detection systems are bulky, power-intensive, and prone to errors due to thermal drift, filter bandwidth variations, and source intensity changes, which affect accuracy and require complex calibration.
Innovation Solution
A compact, low-power optical gas detection system using two optical pathways with substantially collinear paths, where one LED produces two wavelengths, and a ratio of detector signals is used to measure gas concentration, canceling out variations in the light source and filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional broadband light source and optical filter are used for gas detection, then gas concentration measurement is achieved, but the system becomes bulky and power-intensive
Solution Approach 1:
The patent extracts only the necessary spectral bands using narrowband LEDs instead of using a broadband light source with optical filters. This eliminates the need for bulky optical filter components and reduces power consumption while maintaining gas detection accuracy through direct wavelength selection matching gas absorption characteristics
Solution Approach 2:
The patent replaces the mechanical/optical filter system with electronic wavelength selection using LEDs. Instead of physically filtering broadband light through optical filters, the system electronically selects specific wavelengths by activating LEDs that emit at the precise absorption wavelengths of target gases, simplifying the optical path and reducing power requirements
2Measurement precision
If traditional optical filter system is used, then wavelength selection is achieved, but thermal drift and source intensity changes affect measurement accuracy
Solution Approach 1:
The patent implements a feedback mechanism using a reference LED and reference detector that continuously monitors the optical path conditions. The ratio of the measurement signal to the reference signal compensates for thermal drift and source intensity changes, as both the measurement LED and reference LED are affected equally by environmental conditions, allowing the ratio to remain stable and accurate
Solution Approach 2:
The patent changes the operational parameters by using narrowband LEDs with center wavelengths precisely matched to gas absorption peaks rather than using broadband sources with filters. This parameter change from broadband to narrowband emission eliminates the sensitivity to thermal drift and source intensity variations that plagues filter-based systems, as the LED wavelength is inherently stable
3Adaptability or versatility
If color wheels or filters are used at photodetectors for multi-gas detection, then multiple gas measurements are achieved, but device complexity increases
Solution Approach 1:
The patent achieves multi-gas detection capability through a universal approach where multiple LEDs with different wavelengths can be used to detect different gases. Each gas has its specific absorption wavelength, and by selecting appropriate LEDs, the same simple optical path can detect multiple gases without requiring complex color wheels or multiple filters, making the system universally applicable to various gas detection needs
Solution Approach 2:
The patent segments the detection function by assigning specific LEDs to specific gas detection tasks based on their emission wavelengths. Instead of using a single complex optical path with color wheels that must sequentially filter for different gases, the system segments the functionality into dedicated wavelength sources, allowing simultaneous or rapid sequential detection of multiple gases through simple wavelength selection
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
The system achieves high accuracy and stability, reducing size and power consumption by an order of magnitude, while simplifying calibration and eliminating the need for complex drift compensation.
Implementation Method 1
Most molecules can absorb infrared light, causing them to bend, stretch or twist. The amount of IR light absorbed is proportional to the concentration. The energy of the photons is not enough to cause ionization, and thus the detection principle is very different from that of a photoionization detector (RD). Ultimately, the energy is converted to kinetic energy, causing the molecules to speed up and thus heat the gas.
Implementation Method 2
The detector has an optical filter in front of it that eliminates a light except the wavelength that the selected gas molecules can absorb.
Data Source
AI summary
System and apparatus for robust, portable gas detection. Specifically, this disclosure describes apparatuses and systems for optical gas detection in a compact package using two optical pathways. There is a need for a very compact, low-power, gas detection system for gases such as CO2, NOx, water vapor, methane, etc. This disclosure provides an ultra-compact and highly stable and efficient optical measurement system based on principals of optical absorption spectroscopy using substantially collinear pathways.