Self-Referencing Optical Spectroscopy for Fluctuating Light Sources
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Solution Overview
Problem
Existing methods for determining substance concentrations in gaseous or fluid media using optical absorption spectroscopy face limitations in achieving high-resolution, cost-effectiveness, and robustness due to the use of broadband light sources, which suffer from spectral and temporal fluctuations, and the expense and fragility of tunable laser sources.
Innovation Solution
A self-referencing optical absorption spectroscopy method utilizing spectrally selective broadband light sources, such as LEDs, where the light is coupled through optical waveguides and a mode coupler to homogenize radiation characteristics, and the measuring cell is designed to change its effective absorption length or pressure to generate a reference signal, allowing for demodulation of the optical signal and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If broadband light sources are used for optical absorption spectroscopy, then cost is reduced and device complexity is lowered, but measurement precision deteriorates due to spectral and temporal fluctuations
Solution Approach 1:
A reference channel is introduced as an intermediary path that receives the same broadband light without passing through the measurement cell. This reference channel compensates for spectral and temporal fluctuations by providing a baseline signal that can be used to normalize the measurement channel signal, thereby maintaining measurement precision while using cost-effective broadband light sources
Solution Approach 2:
The optical path is duplicated into two identical channels: a measurement channel that passes through the sample and a reference channel that does not. Both channels receive the same broadband light source, creating a copy of the light path that can be used for comparison and compensation of source fluctuations
2Measurement precision
If tunable laser sources are used for high resolution measurements, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex tunable laser sources with inexpensive broadband light sources (such as LEDs) that have shorter operational lifetimes or require more frequent replacement. This substitution reduces device complexity and cost while maintaining measurement capability through the use of a broadband spectrum and reference channel compensation
3Device complexity
If broadband light sources are used without reference channels, then device complexity is reduced, but measurement precision deteriorates due to inability to compensate fluctuations
Solution Approach 1:
A reference channel is introduced as an intermediary path that receives the same broadband light without passing through the measurement cell. This reference channel compensates for spectral and temporal fluctuations by providing a baseline signal that can be used to normalize the measurement channel signal, thereby maintaining measurement precision while using cost-effective broadband light sources
Solution Approach 2:
The reference channel provides continuous feedback information about the broadband light source characteristics. This feedback is used to dynamically compensate for and correct fluctuations in the measurement channel, enabling high-precision measurements without requiring complex stabilization systems on the light source itself
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 cost-effective, high-resolution, and fast substance concentration measurements that are robust to external influences, achieving higher accuracy and reliability by eliminating the need for multiple receivers and simplifying the optical path, while being suitable for harsh environments like exhaust ducts of vehicles.
Implementation Method 1
The invention relates to a method and a device for determining substance concentrations in gaseous or fluid media by means of optical absorption spectroscopy
Implementation Method 2
the temporally and locally fluctuating radiation characteristics of the broadband light sources being homogenized by means of a mode coupler in the light path between the second optical fiber and another optical fiber in front of the measuring cell
Data Source
AI summary
The invention relates to a method and to a device for using partially non-stabilized broadband light sources to accurately measure partially broadband-absorbing substances using referencing measuring cells. In order to create a low-cost, high-resolution, and at the same time fast spectrographic device for measuring concentrations of substances in fluid or gaseous media that is also suitable for harsh environments, the light radiated by the broadband light sources (1) through light guiding optical systems is fed through the measuring section of the self-referencing measuring cell (20, 30, 40) or only partially through a measuring cell (10) to a measurement detector (photoreceptor 11) and partially through a reference path (optical waveguide 8) to a reference detector (photoreceptor 15), and a mode coupler (5, 9, 14) is associated with each optical waveguide (2, 4, 7, 8) in order to homogenize the radiation characteristic of the broadband light sources (1), which varies over time and space.