Gas Analyzer Laser Interference Noise Reduction
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Solution Overview
Problem
Gas analyzing apparatuses using laser absorption spectroscopy face challenges in reducing interference noise due to multiple reflections of laser light between optical elements, which conventional methods like randomly moving condenser lenses cannot effectively address.
Innovation Solution
The apparatus includes an actuating unit that moves at least one optical element, such as the laser light emitting or receiving element, by an amplitude of n/2 times the wavelength of the laser light, allowing for two states of operation where interference noise phases are opposite, enabling noise reduction through signal averaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a condenser lens is finely moved randomly along the optical axis direction, then interference noise may be reduced, but the interference noise cannot be effectively reduced and the measurement precision remains insufficient
Solution Approach 1:
The patent applies periodic action by moving the optical element (condenser lens or light receiving element) with a specific amplitude of n/2 times the wavelength of laser light. This periodic movement creates two distinct states where interference noise phases are opposite, allowing effective noise reduction through signal averaging. The movement follows a controlled periodic pattern rather than random movement, enabling systematic elimination of interference noise while improving measurement precision.
Solution Approach 2:
The patent changes the movement parameter from random fine movement to a specific deterministic amplitude of n/2 times the wavelength. By precisely controlling the movement amplitude to match the wavelength relationship, the system transforms the interference noise pattern into two opposite phases that can be effectively averaged out, thereby improving measurement precision and reducing interference noise simultaneously.
2Measurement precision
If optical elements are moved to reduce interference noise, then measurement accuracy improves, but the device complexity increases
Solution Approach 1:
The actuating unit is designed with multi-functionality, serving both to position optical elements for optimal light collection and to introduce controlled periodic movement for interference noise reduction. This single actuating mechanism performs multiple functions: maintaining optical alignment and generating the wavelength-based movement pattern, thereby reducing overall device complexity while achieving improved measurement precision.
Solution Approach 2:
By changing the movement amplitude parameter to a specific value (n/2 times wavelength), the system achieves interference noise reduction without requiring complex additional mechanisms. The parameter change approach allows a simple actuating unit to accomplish both positioning and noise reduction functions, avoiding the need for separate complex control systems.
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 effectively reduces interference noise compared to random fine movement methods, improving the accuracy of gas concentration measurements by averaging signals from these states, and allows for a more compact actuating unit design.
Implementation Method 1
Gas analyzing apparatuses to measure gas concentration using laser absorption spectroscopy are known
Implementation Method 2
The coherence of laser light causes interference light, due to multiple reflection of light between the optical elements. The interference light is superimposed on the measuring light as an interference noise
Data Source
AI summary
In gas analyzing apparatuses, interference noises should be reduced. A gas analyzing apparatus for analyzing component included in measuring object gas, including: a light emitting unit to irradiate laser light to the measuring object gas; a light receiving unit to receive the laser light having passed through the measuring object gas; an actuating unit to change an optical path length of the laser light by moving at least one optical element that is arranged in a light path where the laser light is passing; and a calculating unit to calculate concentration of the measuring object gas, based on signals detected by the light receiving unit in two states where the optical element is at different positions by n/2 times the wavelength of the laser light (where, n is integer) is provided.