Methodologies for Hyperspectral Thermal Imaging

Anders Christian Løchte Jørgensen

doi:10.21996/4vpg-yk48

Methodologies for Hyperspectral Thermal Imaging

Anders Christian Løchte Jørgensen

Publikation: Afhandling › Ph.d.-afhandling

34 Downloads (Pure)

Abstract

Dette PhD projekt omhandler designet, karakteriseringen og udviklingen af et hyperspektralt termografisk kamera. Desuden omhandler projektet analysen af de løbende tredimensionelle hyperspekrale billeder, som er indfanget i løbed af forskellige stadier af fornævnte udvikling. Det hyperspektrale termografiske kamera bygger på et FabryPérot interferometer (FPI) som fungerer som bølgelængde filter af det termiske lys der optages med kameraet.
En stor del kameraudviklingen drejede sig om produktionen af partielt transmitterende spejle til inkorporering i Fabry-Pérot interferometeret, som er blandt de mest essentielle komponenter i kameraet. Denne udvikling vedrørede pådampning af tyndfilm på zinkselenid substrater i form af halv- og kvartbølgelængde lag af
skiftende materialer med henholdsvis højt og lavt refraktivt index. En succesfuld tyndfilmsstruktur bestående af tre lag af henholdsvis germanium/bariumfluorid/germanium blev deponeret på zinkselenid. Spejle af denne type blev inkorporeret it et FPI og det lykkedes at optage hyperspektrale termografiske billeder. På baggrund af disse billeder blev det vist at prøver bestående af en høj-emissivitets carbon-nanotube belagt overflade, aluminium, borosilikatglas, polyimid tape og sortmalet aluminum kunne skilles ad enkeltvist, baseret på deres termiske udstrålingsspektrum. Dette eksperiment viser at funktionaliteten i kameraet of understreget at termiske udstrålingsspektre kan opsamles med et hyperspektralt termografisk kamera, baseret på
et FPI.
Senere i projektet blev lav-absorptions spejle anskaffet bestående af en tre-lags struktur af henholdsvis sermanium/thoriumfluorid/germanium fra selskabet II-VI incorporated. Disse spejle blev brugt til at optage hyperspektrale termografiske billeder med en nøjagtig materialegenkendelse ned til 34 °C af fem prøver bestående af polyimid tape, Al2O3, borosilikatglas, kvartsglas og keramisk Al2O3. Materialegenkendelsen kunne udføres ved 34 °C med korrekt bestemmelse over 94 % af tilfældende. Over 34 °C kunne materialerne bestemmes med 100 % nøjagtighed. Desuden kunne overfladetemperaturen af fornævnte prøver bestemmes indenfor en usikkerhed på 1.1 °C baseret på det termiske udstrålingsspektrum og materialespecifikke temperatur-
modeller. I slutningen af dette projekt forsøges det hyperspektrale kamera anvendt til genkendelse af polymerer opvarmet til 100 °C og separering af transmissions spektret for
specifikke gas-atmosfærer. Begge disse eksperimenter viste lovende resultater. Det kan dermed konkluderes at det hyperspektrale termografiske kamera udviklet i dette projekt kan anvendes til nyttefuld avanceret termografisk analyse.

Originalsprog	Engelsk
Bevilgende institution	Syddansk Universitet
Vejledere/rådgivere	Kjelstrup-Hansen, Jakob, Hovedvejleder Jørgensen, Bjarke, Vejleder, Ekstern person
Eksterne samarbejdspartnere	Newtec Engineering A/S
Dato for forsvar	20. jan. 2022
Udgiver	Syddansk Universitet. Det Tekniske Fakultet
DOI	https://doi.org/10.21996/4vpg-yk48
Status	Udgivet - 5. jan. 2022

Dokumenter og links

10.21996/4vpg-yk48

Open Access VersionForlagets udgivne version, 134 MB

SDU link

Tjek adgangen til materialet i Syddansk Universitetsbiblioteks søgemaskine

Surface temperature determination using long range thermal emission spectroscopy based on a first order scanning Fabry-Pérot interferometer
Kjelstrup-Hansen, J., Løchte Jørgensen, A. C., Larsen, M. N., Petrunin, V. & Jørgensen, B., 17. jan. 2022, I: Optics Express. 30, 2, s. 2186-2196
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › peer review

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Acquisition and Analysis of Hyperspectral Thermal Images for Sample Segregation
Løchte Jørgensen, A. C., Kjelstrup-Hansen, J., Jensen, B. B. E., Petrunin, V., Fink, S. F. & Jørgensen, B., mar. 2021, I: Applied Spectroscopy. 75, 3, s. 317-324
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › peer review

Citationsformater

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AB - This PhD project focuses on the development and characterisation of a hyperspectral thermal imaging system. The imaging system is based on a commercial microbolometer sensor, with a sensitivity in the long wave infrared (LWIR) range between 8 and 14 µm, followed by a scanning Fabry-Pérot interferometer (FPI) in front of the collecting optics. The hyperspectral datacube is therefore plane scanned, which allows the camera to build the hyperspectral datacube while being statically mounted. The scanning FPI, acting as a wavelength filter, operates in the first order. The most essential components in the FPI are the thermal mirrors which constitute the focus of the first part of this thesis. Initial physical vapour deposition (PVD) experiments provided thermal mirrors that lead to hyperspectral thermal images which documented the concept of the imager. A mirror was produced by using a recipe which consisted of three-layer-structure including an absentee layer at the design wavelength of 10.5 µm. The thermal mirror recipe comprised of an antireflective coated ZnSe substrate upon which a Ge/BaF2/Ge-coating was deposited. The two mirrors used in the FPI showed average absorption values of 10.5 % and 6.8 % measured by standard Fourier transform infrared spectroscopy (FTIR) measurements combined with a reflection-configured FTIR measurement. The mirrors were incorporated into an FPI and used to acquire hyperspectral thermal images. It was shown that the difference in the emission spectrum of five samples of polyimide tape, a carbon nanotube coated aluminium surface, borosilicate glass, black painted aluminium, and bare aluminium was measurable at 100 °C as opposed to the measurements of the emitted thermal radiation at room temperature (RT). The RT measurements were very inefficient using the high absorption homegrown mirrors, and at the final part of this project, commercially coated thermal mirrors were purchased and incorporated into the FPI. These mirrors consist of an antireflective coated ZnSe substrate coated with a Ge/ThF4/Ge coating with absorption values of <2 % within the sensor sensitivity range measured by a combination of FTIR and FTIRR measurements. These mirrors were incorporated into the FPI and used to acquire hyperspectral thermal images. A logistic regression model was used to differentiate between polyimide tape, Al2O3, borosilicate glass, fused silica, and Al2O3 ceramic at temperatures as low as 34 °C. Each material was recognised with true positive rates above 94 %, calculated from the individual pixel spectrum. The surface temperature of the samples was subsequently predicted using pre-fitted partial least squares (PLS) models, which predicted all surface temperature values with a common root mean square error (RMSE) of 1.10 °C whereby it outperformed conventional thermography. The last chapter concerns applications of the hyperspectral thermal imaging system developed in this thesis. Two separate images are analysed and documents a strong segregation of organic gasses based on transmission spectra, and a promising segregation of polymers based on emission spectra at 100 °C compound temperature. In summary, it is concluded that an FPI based hyperspectral thermal imager is a viable instrument for hyperspectral acquisition of light emitted within the LWIR range.

U2 - 10.21996/4vpg-yk48

DO - 10.21996/4vpg-yk48

M3 - Ph.D. thesis

PB - Syddansk Universitet. Det Tekniske Fakultet

ER -

Methodologies for Hyperspectral Thermal Imaging

Abstract

Dokumenter og links

SDU link

Fingeraftryk

Relaterede publikationer

Surface temperature determination using long range thermal emission spectroscopy based on a first order scanning Fabry-Pérot interferometer

Acquisition and Analysis of Hyperspectral Thermal Images for Sample Segregation

Citationsformater