Pulsed NDIR Optical Detection for Liquid Molecular Concentration

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Solution Overview

Problem

Existing methods for detecting molecules in a liquid medium using Non-Dispersive Infra-Red (NDIR) sensors face limitations, particularly in achieving high accuracy and precision due to scattering noise and small sample volume per measurement, which affects the reliability of molecular concentration quantification.

Innovation Solution

The method involves pulsing a signal beam and a reference beam, optionally with an interference beam, to pass through a liquid sample, using detectors in an optical co-axial configuration to process the output and calculate the concentration of targeted molecules by adjusting for interference and noise, employing techniques like simultaneous pulsing and beam splitting to enhance noise cancellation and sample volume capture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If NDIR sensors are used to detect molecules in liquid medium, then gas detection capability is available, but scattering noise increases and measurement accuracy decreases

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidconcentration measurement precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies periodic pulsing of the infrared beam at frequencies between 1-100 kHz to freeze molecular motion and reduce scattering noise. By using pulsed rather than continuous illumination, the system captures snapshots of molecular positions, reducing the impact of scattering events during the measurement window.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses a reference beam that copies the signal beam's path through the sample but without the absorption interaction. This reference copy allows subtraction of scattering noise from the signal measurement, isolating the true absorption signal from the targeted molecules.

Inventive Principle:

Principle #26Copying

2Measurement precision

If continuous beam is used for detection, then simple detection is achieved, but scattering noise from molecular motion reduces measurement accuracy

Engineering Contradiction:

Improveabsorption measurement accuracyVSAvoidscattering noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic pulsing of the infrared beam to freeze molecular motion during the measurement window. This temporal gating reduces scattering noise by capturing absorption events when molecules are relatively stationary, improving measurement precision.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies preliminary processing steps including background subtraction and reference beam normalization before final concentration calculation. These preliminary actions remove scattering noise and systematic errors from the raw signal.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If small sample volume is used per measurement, then measurement speed increases, but statistical reliability of concentration quantification decreases

Engineering Contradiction:

Improvemeasurement speedVSAvoidconcentration quantification reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements continuous scanning of the infrared beam across the sample volume, continuously collecting absorption data from multiple locations. This continuous action accumulates statistical information while maintaining high measurement throughput.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent performs preliminary averaging of multiple rapid measurements to establish a baseline concentration value. This preliminary statistical processing improves reliability while maintaining fast measurement capability.

Inventive Principle:

Principle #10Preliminary action

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 improves the accuracy, precision, and reliability of molecular concentration measurements in liquids by effectively reducing scattering noise and allowing for larger sample volumes, thereby enhancing the detection of molecules in complex media like human tissue.

Implementation Method 1

NDIR sensors utilize the principle that various gas molecules exhibit substantial absorption at specific wavelengths in the infrared radiation spectrum

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

scattering noise and small sample volume per measurement

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentUS11604138B2Minimization of noise in optical data capture for liquids

Publication Date: 2023.03.14 LIQUID SENSING INC

AI summary

A process quantifies a concentration of a targeted molecule in a liquid sample by pulsing signal and reference beams from their own sources, then spatially combining the pulsed beams into a single radiation beam which passes into the liquid sample and then detecting pulsed output beams after the single radiation beam passes out of the liquid sample. The pulsed outputs of the signal and reference beams are processed to obtain a value over a preselected period of time and, if an interference beam is used, it is processed with the reference beam to obtain a calibration curve adjustment representative of optical interference represented by at least one interfering molecule concentration which is used to calculate the concentration level of the targeted particle in the liquid sample. Two detectors, which may have an optical co-axial configuration, can be used for detection of pulsed beams.