NDIR Gas Sensor Light Coupling Miniaturization
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Solution Overview
Problem
Existing NDIR gas sensors require large light cavities for accurate sensing, leading to high manufacturing costs and increased size, with limited miniaturization potential due to complex structures and high power consumption.
Innovation Solution
A gas sensor design utilizing first and second light coupling portions to reflect and condense light, with adjustable curvature radii and light shielding films to enhance light path length and reflectivity, while minimizing size through the use of infrared reflective materials and light filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long light path is used for accurate sensing, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent employs curved reflective surfaces (spherical or elliptical mirrors) within the light cavity to redirect light paths. This curvature allows light to bounce multiple times through the gas sample in a compact volume, achieving a long effective light path without increasing the physical device size proportionally
Solution Approach 2:
The light cavity is designed with nested reflective structures where inner reflective surfaces are positioned within outer boundaries. This nesting allows multiple light reflections to occur within a confined spatial envelope, maximizing light path length while minimizing overall device volume
2Measurement precision
If Au coating is applied to light cavity surface for high reflectivity, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive gold (Au) coating with cheaper alternative reflective materials that provide sufficient reflectivity for the application. These cost-effective coatings maintain adequate light reflection performance while significantly reducing manufacturing expenses
Solution Approach 2:
The invention adjusts the reflectivity parameter from the high standard of gold coating to a sufficient level achievable with cheaper materials. By optimizing the balance between reflectivity and cost, the patent achieves acceptable measurement precision without the high manufacturing cost of Au coating
3Measurement precision
If filament light source is used for NDIR sensing, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent replaces the thermal filament light source with an LED (light-emitting diode) light source. This substitution transitions from a thermal radiation mechanism to an electroluminescence mechanism, significantly reducing power consumption while maintaining sufficient light output for NDIR gas sensing measurements
4Measurement precision
If various optical reflective structures are added for appropriate light path, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs the light cavity with integrated reflective surfaces that serve multiple functions: defining the light path, reflecting light back through the sample, and structurally containing the gas chamber. This multi-functionality reduces the need for separate optical components, simplifying the overall device structure while maintaining precise light path control
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 design achieves a longer light path for accurate sensing while reducing overall size, improving gas sensing efficiency by optimizing light focus, blocking external light leakage, and enhancing reflectivity, thus enabling miniaturization without compromising measurement performance.
Implementation Method 1
a gas sensor using an NDIR (Non-Dispersive Infra-Red) system is configured to reversely count a gaseous concentration by measuring an absorption rate of a target gas on a light path in accordance with a unique absorption wavelength of NDIR and a Beer-Lambert law
Implementation Method 2
a surface of the light cavity is treated with Au to make sure of high reflectivity of infrared rays
Implementation Method 3
a first light coupling portion for reflecting and condensing light emitted from a light source portion toward a light cavity portion and a second light coupling portion for reflecting and condensing the light reflected from the light cavity portion
Data Source
AI summary
The present invention relates to a gas sensor employing a non-dispersive infrared (NDIR) scheme. The gas sensor may comprise: a light source portion for emitting light; a light cavity portion for multi-reflecting the emitted light; a light detecting portion for detecting the multi-reflected light; a first light coupling portion for reflecting and concentrating the light emitted by the light source portion toward the light cavity portion; and a second light coupling portion for reflecting and concentrating the light reflected by the light cavity portion toward the light detecting portion. The first light coupling portion may comprise a light emitting surface that faces a side surface of the light cavity portion and has a via hole through which light passes, and a reflecting surface extending from the light emitting surface so as to surround the upper portion and the side portion of the light source portion such that light emitted by the light source portion is reflected toward the via hole of the light emitting surface. The second light coupling portion may comprise a light incident surface that faces a side surface of the light cavity portion and has a via hole through which light incident from the light cavity portion passes, and a reflecting surface extending from the light incident surface so as to surround the upper portion and the side portion of the light detecting portion such that light incident from the light cavity portion is reflected toward the light detecting portion.