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Towards Quantitative Diagnostics using Short-Pulse Laser Techniques

Ehn, Andreas LU (2012) In Lund Report on Combustion Physics LRCP-160.
Abstract (Swedish)
Popular Abstract in Swedish

Med utvecklingen av lasern tillkom ett diagnostiserningsverktyg för forskning inom medicin, biologi, fysik, kemi mm. En laser är i princip en ljuskälla som skickar ut ljus med synnerligen välbestämd färg och riktning. Ljus som har en viss färg kan påverka vissa molekyler och atomer. Under vissa förutsättningar svarar dessa ämnen genom att i sin tur skicka ut ljus i en annan färg som är typsikt för detta ämnen. Därför kan man mäta förekomsten av vissa ämnen med hjälp av laser. Det ljus som dessa ämnen skickar ut kan även bära på information av miljön som ämnet befinner sig i, såsom temperatur, tryck, förekomsten av andra ämnen osv. Det finns dock en hel uppsjö av andra mätmetoder som kan mäta... (More)
Popular Abstract in Swedish

Med utvecklingen av lasern tillkom ett diagnostiserningsverktyg för forskning inom medicin, biologi, fysik, kemi mm. En laser är i princip en ljuskälla som skickar ut ljus med synnerligen välbestämd färg och riktning. Ljus som har en viss färg kan påverka vissa molekyler och atomer. Under vissa förutsättningar svarar dessa ämnen genom att i sin tur skicka ut ljus i en annan färg som är typsikt för detta ämnen. Därför kan man mäta förekomsten av vissa ämnen med hjälp av laser. Det ljus som dessa ämnen skickar ut kan även bära på information av miljön som ämnet befinner sig i, såsom temperatur, tryck, förekomsten av andra ämnen osv. Det finns dock en hel uppsjö av andra mätmetoder som kan mäta liknande storheter, men den stora fördelen med laser är att man kan utföra beröringsfria mätningar, med hög prescision in-situ, dvs att man mäter objektet i dess naturliga miljö (”på plats”). Dessa fördelar gör lasermätningar synnerligen användbara i ett flertal forskningsområden, tex i medicinforskning då man kan göra mätningar inne i kroppen eller i förbränningsforskning där man inte stör förbränningen i en motorer eller gasturbinner.



Målet med det arbete som denna avhandling bygger på har varit att utveckla och demonstrera nya laserbaserade mättekniker för undersökningar av tillämpad karraktär, med inriktning på flödesdynamik och förbränning. De problem man försökt att handskas med är mätningar i besvärliga mätmiljöer. Typer av besvärligheter kan vara stora mängder ströljus eller då även ämnen utan intresse påverkas av laserljuset och förstör mätningen. Vidare har modeller utvecklats som gör att andra forskare ska kunna förutse potentialen för detta verktyg i sin forskning. Det har även utvecklats mätmetoder som skapar tvådimensionella bilder av hur ämnenas responssignal ser ut i tidsdomänen. Sådan information är av betydelse eftersom det ger information om ämnets omgivning, och är nödvändig om man ska kunna mäta ämneskoncentrationer från dessa responssignaler. Denna mätmetod möjligör även kvantitativa koncentrationer av ämnen i ett laserskott, vilket är en fördel när man studerar flödesdynamik och turbulens. Tekniken har vidare kombinerats med en tredje mätmetod som möjliggör mätningar av signalresponsens tidsberoende i besvärliga mätmiljöer där spritt ljus och andra störande ljuskällor kan undertryckas. Avhandlingen innehåller även utveckling och utnyttjande av avbildande mätmetoder av ämnen som tidigare inte varit möjliga att avbilda. Slutligen har utveckling och demonstration av en typ av ljusradar utförts som möjliggör mätningar av kvantitativa koncentrations- och temperaturmätningar med mycket hög rumsupplösning. (Less)
Abstract
Laser based diagnostic tools have had an exploding impact on fundamental as

well as applied research in a number of disciplines, such as biomedicine, physical

chemistry etc over the last decades. Whereas fundamental research often investigate

phenomena in extreme conditions, applied research aims at performing in-situ

measurements, in order to understand the many aspects and entangled phenomena

that affects the research of interest. Moreover, laser measurements performed

in applied research often aims at presenting images, since variations, fluctuations

and the complexity of dynamical events are better viewed and understood in its

context, which is provided in an... (More)
Laser based diagnostic tools have had an exploding impact on fundamental as

well as applied research in a number of disciplines, such as biomedicine, physical

chemistry etc over the last decades. Whereas fundamental research often investigate

phenomena in extreme conditions, applied research aims at performing in-situ

measurements, in order to understand the many aspects and entangled phenomena

that affects the research of interest. Moreover, laser measurements performed

in applied research often aims at presenting images, since variations, fluctuations

and the complexity of dynamical events are better viewed and understood in its

context, which is provided in an image. Therefore, a number of diagnostic techniques

have been developed and demonstrated in this work to facilitate laser-based

studies in problematic environments. Issues that often makes optical measurements

problematic could be scattered light and interfering photo-induced signals.

Picosecond lasers and short gated ICCD cameras has been used to suppress interfering

signals in Raman as well as fluorescence studies. Moreover, a model so

simulate the detection has been developed that should be used to evaluate the

potential of performing temporal filtering. By using this evaluation tool, a specific

experimental setup can be evaluated in Raman as well as fluorescence measurements,

if the system is characterized and the temporal shape of the signals are

known. Temporal filtering should be considered as a complementary to other filtering

techniques, such as spectral or polarization filters. The simulating detection

model was further developed to determine temporal shapes of signals in an image.

We call this technique DIME, Dual Imaging with Modeling Evaluation, since two

acquired images are combined and evaluated by modeling the detection of these

two images. The most common application of such a scheme is fluorescence lifetime

imaging (FLI), which is a widely used optical tool in biomedicine. In comparison

to traditional FLI techniques, the DIME concept allows higher signal-to-noise ratios.

Furthermore, a rapid lifetime determination algorithm is presented, called

RGP-LD (Ramped Gain Profile-Lifetime Determination), that shows promising

potential for fluorescence lifetime imaging, especially in combination with DIME.

The DIME concept has been utilized to achieve quenching corrected fluorescence

images of formaldehyde in a flame, as well as quantitative oxygen concentration

measurements in toluene seeded N2/O2 flows. DIME was also evaluated in combination

with an optical measurement technique called SLIPI (Structured Laser

Illumination Planar Imaging).The combination of techniques was able to provide

quantitative fluorescence lifetime data even though the signal was collected through

multiple scattering media. Picosecond lasers and fast detection systems, such as

streak cameras, MCP-PMT, where used to demonstrate and develop picosecond

LIDAR (LIght Detection And Ranging). Such a scheme allows single ended measurements

in case of limited optical access, which most often is the case in practical

applications. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr Brockhinke, Andreas, Fakultät für Chemie, Physikalische Chemie 1, Universität Bielefeld, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
PicoSecond Laser Diagnostics, Raman Scattering, Photo Fragmentation, Fluorescnece Lifetime Imaging, Temporal Filtering, Fysicumarkivet A:2012:Ehn, LIDAR, Laser-Induced Fluorescence
in
Lund Report on Combustion Physics
volume
LRCP-160
pages
118 pages
defense location
Lecture Hall B, Fysicum, Sölvegatan 14 A, Lund University Faculty of Engineering
defense date
2012-06-15 10:15
ISSN
1102-8718
language
English
LU publication?
yes
id
6353aa1d-ac2e-4d7f-bbf8-9ae0d65862d1 (old id 2542654)
date added to LUP
2012-05-23 14:46:21
date last changed
2016-09-19 08:45:00
@misc{6353aa1d-ac2e-4d7f-bbf8-9ae0d65862d1,
  abstract     = {Laser based diagnostic tools have had an exploding impact on fundamental as<br/><br>
well as applied research in a number of disciplines, such as biomedicine, physical<br/><br>
chemistry etc over the last decades. Whereas fundamental research often investigate<br/><br>
phenomena in extreme conditions, applied research aims at performing in-situ<br/><br>
measurements, in order to understand the many aspects and entangled phenomena<br/><br>
that affects the research of interest. Moreover, laser measurements performed<br/><br>
in applied research often aims at presenting images, since variations, fluctuations<br/><br>
and the complexity of dynamical events are better viewed and understood in its<br/><br>
context, which is provided in an image. Therefore, a number of diagnostic techniques<br/><br>
have been developed and demonstrated in this work to facilitate laser-based<br/><br>
studies in problematic environments. Issues that often makes optical measurements<br/><br>
problematic could be scattered light and interfering photo-induced signals.<br/><br>
Picosecond lasers and short gated ICCD cameras has been used to suppress interfering<br/><br>
signals in Raman as well as fluorescence studies. Moreover, a model so<br/><br>
simulate the detection has been developed that should be used to evaluate the<br/><br>
potential of performing temporal filtering. By using this evaluation tool, a specific<br/><br>
experimental setup can be evaluated in Raman as well as fluorescence measurements,<br/><br>
if the system is characterized and the temporal shape of the signals are<br/><br>
known. Temporal filtering should be considered as a complementary to other filtering<br/><br>
techniques, such as spectral or polarization filters. The simulating detection<br/><br>
model was further developed to determine temporal shapes of signals in an image.<br/><br>
We call this technique DIME, Dual Imaging with Modeling Evaluation, since two<br/><br>
acquired images are combined and evaluated by modeling the detection of these<br/><br>
two images. The most common application of such a scheme is fluorescence lifetime<br/><br>
imaging (FLI), which is a widely used optical tool in biomedicine. In comparison<br/><br>
to traditional FLI techniques, the DIME concept allows higher signal-to-noise ratios.<br/><br>
Furthermore, a rapid lifetime determination algorithm is presented, called<br/><br>
RGP-LD (Ramped Gain Profile-Lifetime Determination), that shows promising<br/><br>
potential for fluorescence lifetime imaging, especially in combination with DIME.<br/><br>
The DIME concept has been utilized to achieve quenching corrected fluorescence<br/><br>
images of formaldehyde in a flame, as well as quantitative oxygen concentration<br/><br>
measurements in toluene seeded N2/O2 flows. DIME was also evaluated in combination<br/><br>
with an optical measurement technique called SLIPI (Structured Laser<br/><br>
Illumination Planar Imaging).The combination of techniques was able to provide<br/><br>
quantitative fluorescence lifetime data even though the signal was collected through<br/><br>
multiple scattering media. Picosecond lasers and fast detection systems, such as<br/><br>
streak cameras, MCP-PMT, where used to demonstrate and develop picosecond<br/><br>
LIDAR (LIght Detection And Ranging). Such a scheme allows single ended measurements<br/><br>
in case of limited optical access, which most often is the case in practical<br/><br>
applications.},
  author       = {Ehn, Andreas},
  issn         = {1102-8718},
  keyword      = {PicoSecond Laser Diagnostics,Raman Scattering,Photo Fragmentation,Fluorescnece Lifetime Imaging,Temporal Filtering,Fysicumarkivet A:2012:Ehn,LIDAR,Laser-Induced Fluorescence},
  language     = {eng},
  pages        = {118},
  series       = {Lund Report on Combustion Physics},
  title        = {Towards Quantitative Diagnostics using Short-Pulse Laser Techniques},
  volume       = {LRCP-160},
  year         = {2012},
}