Optical Gas Sensor with Nested Reflective Cones
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Solution Overview
Problem
Existing optical gas sensors, particularly non-dispersive infrared (NDIR) sensors, face challenges in achieving optimized compactness and sensitivity for gas detection, as they often require complex configurations and suffer from reduced light detection efficiency due to aperture placement and reflective segment geometries.
Innovation Solution
A gas sensor design featuring a chamber with transverse walls and a peripheral cylindrical wall containing reflective segments that form converging cones for light emission and reference detection, optimized with aperture placement outside the light cone projections and inclined optical axes to enhance light collection and sensitivity, allowing for improved gas analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light source and photodetectors are arranged in a conventional configuration, then the sensor can detect gas concentration, but the device size increases and sensitivity decreases
Solution Approach 1:
The measurement photodetector and reference photodetector are nested within the chamber formed by the transverse walls and peripheral wall, with the light source positioned at the apex of the emission cone inside the same chamber. This nested arrangement allows all optical components to occupy a compact three-dimensional space rather than extending linearly, significantly reducing the overall device volume while maintaining detection sensitivity through optimized light path geometry.
Solution Approach 2:
The invention transitions from a conventional linear or planar arrangement of optical components to a three-dimensional configuration using converging cones. The emission cone and measurement/reflection cones create a volumetric light path arrangement where the light source, chamber, and photodetectors are positioned in three-dimensional space with specific angular relationships, enabling compact packaging while preserving optical performance.
2Productivity
If apertures are placed in the transverse walls for gas admission, then gas can flow through the chamber, but light detection efficiency is reduced due to aperture placement within light cone projections
Solution Approach 1:
The apertures are positioned asymmetrically in the transverse walls at locations that are not aligned with the projections of the emission cone and measurement/reflection cones. This asymmetric placement ensures that the apertures do not intercept the light paths, allowing gas to flow through the chamber while maintaining full light detection efficiency. The specific angular and positional relationships of the cones create natural zones where apertures can be placed without compromising optical performance.
3Measurement precision
If reflective segments are added to maximize light path length, then detection sensitivity increases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The peripheral wall is designed with a curved cross-section that forms converging cones, replacing the need for multiple separate flat reflective segments. This curved geometry naturally guides light rays from the emission cone through the chamber and toward the photodetectors, maximizing the light path length and detection sensitivity while simplifying manufacturing. The continuous curved surface is easier to fabricate than multiple precisely aligned flat mirrors, reducing device complexity.
4Illumination intensity
If the light source emits in a wide cone to illuminate the chamber, then more light reaches the photodetector, but the aperture placement becomes more constrained
Solution Approach 1:
The invention uses a three-dimensional converging cone geometry where the light source emits light in an emission cone that is systematically redirected by the curved peripheral wall into measurement and reflection cones. This volumetric arrangement allows the apertures to be positioned in the transverse walls outside the conical projections, effectively utilizing the third dimension to separate gas flow paths from light paths. The wide emission cone is thus accommodated without compromising aperture placement, as the conical geometry creates defined spatial zones.
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 design enhances the sensitivity and compactness of gas sensors by optimizing light detection and minimizing aperture impact, enabling more accurate gas species concentration measurement and increased detection efficiency for gases like carbon dioxide and methane.
Implementation Method 1
a first reflective segment, able to receive a first portion of the emission cone in order to reflect it toward the measurement photodetector
Implementation Method 2
a second reflective segment, able to receive a second portion of the emission cone in order to reflect it toward the reference photodetector
Implementation Method 3
the species from which a gas is composed have absorption spectral properties that are different from one another. Thus, knowing a spectral absorption band of a gaseous species, its concentration may be determined via an estimation of the absorption of the light passing through the gas
Data Source
AI summary
A gas sensor comprises a chamber configured to receive a gas; a light source configured to emit a light wave propagating through the chamber in an emission cone; a measurement photodetector and a reference photodetector, each configured to detect a light wave emitted by the light source and having passed through the chamber. The chamber extends between two transverse walls, arranged opposite one another and connected to one another by a peripheral wall extending therebetween, about a longitudinal axis (Z), and comprising a first reflective segment configured to receive a first portion of the emission cone to reflect it toward the measurement photodetector, thus forming a measurement cone converging toward the measurement photodetector. A second reflective segment of the peripheral wall is configured to receive a second portion of the emission cone to reflect it toward the reference photodetector, thus forming a reference cone converging toward the reference photodetector.