Tunable Diode Lidar Calibration Using an Internal Gas Reference Cell

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Solution Overview

Problem

Existing remote gas detection systems, such as lidar, often produce inaccurate results due to calibration issues, leading to costly false positives or negatives in detecting greenhouse gases like methane, which can result in unnecessary repairs or non-compliance with regulatory standards.

Innovation Solution

Implementing an internal gas reference cell with a known gas concentration within the lidar system to ensure a minimum absorption signal is detected, and using external gas sample cells with known concentrations for calibration, allowing adjustments to parameters and image processing to enhance accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If remote gas detection systems are used without internal calibration references, then device complexity is reduced, but measurement precision deteriorates due to calibration issues

Engineering Contradiction:

Improvegas concentration detection accuracyVSAvoidsystem structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The gas reference cell is nested within the lidar system enclosure, allowing the calibration reference to be integrated into the existing device structure without adding external complexity. The reference cell is positioned within the optical path inside the housing, enabling compact integration while maintaining measurement precision.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

A gas reference cell containing a known concentration of gas is introduced as an intermediary element within the optical path. This reference cell acts as a mediator that provides known absorption values, enabling the system to calibrate and verify its measurements without requiring external calibration equipment or complex external reference systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If external calibration methods are used, then manufacturing precision requirements are reduced, but reliability deteriorates due to field calibration difficulties

Engineering Contradiction:

Improvecalibration accuracy in fieldVSAvoidcalibration implementation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The gas reference cell is pre-filled with a known concentration of gas during manufacturing, establishing a calibrated reference state before deployment. This preliminary calibration action ensures that the reference is ready for immediate use in the field without requiring complex calibration procedures or specialized equipment during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses its own internal reference cell to perform self-calibration and verify its measurement accuracy. The reference cell containing known gas concentration allows the lidar system to independently verify its performance without requiring external calibration services or complex field procedures, thereby improving reliability while maintaining ease of manufacture.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If no minimum absorption signal is guaranteed, then device complexity is reduced, but measurement precision deteriorates due to insufficient signal

Engineering Contradiction:

Improveabsorption signal detectionVSAvoidsignal generation mechanism

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The gas reference cell serves as an intermediary that introduces a known absorption signal into the optical path. By positioning the reference cell within the beam path, it guarantees a minimum absorption signal at specific wavelengths, ensuring sufficient signal for precise measurements without requiring complex signal generation mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Ensures accurate calibration of lidar systems for gas detection by providing a reliable baseline for absorption measurements, reducing false positives and negatives, and enabling precise concentration measurements in the field.

Implementation Method 1

provides known absorptions at wavelengths particular to the gas of interest

Methodology Applied

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

Implementation Method 2

determine gas concentrations... detection of methane gas

Methodology Applied

Scientific EffectLight absorption and detection: Absorption (EM radiation)

Data Source

PatentUS20260029390A1System for accurate tunable diode lidar gas detection

Publication Date: 2026.01.29 QLM TECH LTD

AI summary

A system for accurate tunable diode lidar gas detection, in which an internal gas reference cell with a known concentration of the gas of interest, such as methane (CH4), is provided. The gas reference cell provides known absorptions at wavelengths particular to the gas. The beam from the tunable laser of the lidar system passes through the gas reference cell before scanning a scene, and provides a known level of gas absorption at those known absorption wavelengths. This guarantees there is a minimum signal to be detected by the lidar system, and provides a calibrated, known signal to measure. The temperature of the tunable laser may be controlled using a thermoelectric cooler, adjusting scans of the tunable laser with absorption from the gas reference cell. By making lidar measurements using such calibrated cells, better calibration the system and providing more accurate values gas concentration path length (CPL) from the scene.