Multi-pass Optical Cell for Laser-induced Incandescence

Solution Overview

Problem

Laser-induced incandescence (LII) measurements face challenges in achieving sufficient incandescence signal levels without increasing laser power, especially when dealing with low-density particulate samples, as conventional methods require higher power outputs or larger, unwieldy lasers for in-situ field measurements.

Innovation Solution

A multi-pass optical cell configuration that reflects the laser beam multiple times through the measurement region, maintaining high fluence and increasing the area of illumination without the need for increased laser power, allowing for effective incandescence of particulate matter and enhanced signal levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the diameter of the laser beam is increased to illuminate a larger area, then the area of illumination is increased, but the power output of the laser must be increased to maintain the required threshold fluence

Engineering Contradiction:

Core Design Contradiction:

Area of stationary objectVSPower

Solution Approach 1:

Multiple passes of the laser beam through the measurement region are combined to achieve the effect of illuminating a larger area. The beam is reflected back through the same region multiple times, accumulating the total energy delivery while maintaining the same fluence level on each pass, thus avoiding the need for higher power output.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The laser beam is periodically reflected back through the measurement region multiple times. This periodic action allows the same high-fluence beam to interact with the particulate analyte repeatedly, effectively increasing the total illuminated area over time without requiring increased laser power.

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If the power output of the laser is increased to generate a desired signal level, then the incandescence signal level is improved, but the laser becomes too large or unwieldy for in-situ field measurements

Engineering Contradiction:

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The laser beam is made to continue acting on the particulate analyte by reflecting it multiple times through the measurement region. This continuous action allows a lower-power laser to accumulate sufficient energy delivery to generate the desired incandescence signal, avoiding the need for a large, high-power laser system.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The periodic reflection of the laser beam through the measurement region enables repeated energy delivery to the particulate analyte. This periodic action allows a compact, lower-power laser to achieve the same measurement precision as a large, high-power laser would provide in a single pass.

Inventive Principle:

Principle #19Periodic action

3Area of stationary object

If the laser beam is reflected multiple times through the measurement region, then the area of illumination is increased, but the beam energy may be attenuated

Engineering Contradiction:

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

High-reflectivity mirrors are used as intermediaries to reflect the laser beam through the measurement region multiple times. These mirrors minimize energy loss during reflection, allowing the beam to maintain its fluence level across multiple passes and effectively increase the illuminated area without significant energy attenuation.

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

The multi-pass optical cell effectively increases the area of illumination while maintaining sufficient fluence, enhancing LII measurement capabilities without the need for high-power lasers, thus improving the detection of particulate properties and temperatures.

Implementation Method 1

LII is directed toward heating particulates suspended in a gas phase to incandescence, thereby stimulating emission of blackbody or quasi-blackbody radiation

Methodology Applied

Scientific EffectLaser heating: Absorption (EM radiation)

Implementation Method 2

heating particulates suspended in a gas phase to incandescence, thereby stimulating emission of blackbody or quasi-blackbody radiation

Methodology Applied

Scientific EffectIncandescence: Incandescence

Implementation Method 3

A multi-pass optical cell configuration that reflects the laser beam multiple times through the measurement region

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS10067049B1Method and system for multi-pass laser-induced incandescence

Publication Date: 2018.09.04

AI summary

Various technologies for measurement of properties of a particulate suspended in a gas phase via laser-induced incandescence (LII) are described herein. A beam of light can be emitted into a multi-pass optical cell using a laser. The multi-pass optical cell comprises a system of one or more mirrors that repeatedly reflects the beam through a measurement region, stimulating incandescence of particulates present in the measurement region. An LII detection system having a field of view that encompasses the measurement region then receives blackbody or quasi-blackbody radiation emitted by the incandescing particles and outputs data indicative of one or more properties of the particulates in the measurement region.