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Development of a spectral and goniophotometric imagingmeasurement system for optical characterization of materials
Umeå University, Faculty of Science and Technology, Department of Physics.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
Abstract [en]

In this thesis, a novel color measurement system has been developed and its performance evaluated.It is a modular spectral imaging goniophotometer that measures angle resolved spectralreflectance and transmittance of materials, e.g. textiles, papers, coated materials and flexibleelectronics. It is a highly flexible system that can, unlike most commercial systems, capturereflectance images of both high spectral and spatial resolution over a wide range of measurementgeometries.

It is important that the system can produce geometrically correct images of the samples, as well ascapture spectral information with high accuracy, i.e. the system needs to be both geometricallyand photometrically calibrated. A line-scan spectral camera and a high accuracy translationstage provide 2D-scans of the sample, where imaged area, sample position and measurementgeometry is controlled by a high precision robotic arm. Assessment of spectral and spatialresolution, characterization of the light source and spectral accuracy of the camera are someof the evaluations carried out. Spectral accuracy, and thus color measurement accuracy, isevaluated with the color difference formula CIE ∆Eab. During these evaluations the system isable to measure colors at ∆Eab < 14 and ∆Eab < 30 for a matte and glossy sample respectively,both of which are standard color calibration samples. These results show large color differencesthat are most likely caused by the low signal-to-noise ratio for short wavelengths due to thelight source. Finally, the system’s angle resolved measurement capability is demonstrated bymeasurements of goniochromatic samples whose color shifts with the viewing angle. The changein color is successfully captured for viewing angles in the range of 0 to 45 degrees from the surfacenormal.

Abstract [sv]

I detta examensarbete har ett nytt system f¨or f¨argm¨atning utvecklats och dess prestanda utv¨arderas.Det ¨ar en modul¨ar och spektralt avbildande goniofotometer som tar vinkeluppl¨osta spektral re-flektans och transmittans m¨atningar av material, som t.ex. textilier, papper, belagda materialoch flexibel elektronik. Det ¨ar ett mycket flexibelt system som kan, till skillnad fr˚an de flestakommersiella system, ta reflektansbilder av b˚ade h¨og spektral och spatial uppl¨osning ¨over ettbrett spektrum av m¨atningsgeometrier.

Det ¨ar viktigt att systemet kan producera geometriskt korrekta avbildningar av prover, samtf˚anga spektral information med h¨og noggrannhet. D.v.s. att systemet m˚aste vara b˚ade geometrisktoch fotometriskt kalibrerat. En spektral linje-kamera och ett stegbord med h¨og noggrannhetger 2D-skanningar av provet, d¨ar m¨atomr˚adet, provposition och m¨atgeometri styrs aven robotarm. Spektral och spatial uppl¨osning, karakterisering av ljusk¨allan och kamerans spektralanoggrannhet ¨ar n˚agra av de utv¨arderingar som utf¨orts. Den spektrala noggrannheten, ochd¨armed noggrannheten f¨or f¨argm¨atning, utv¨arderas med f¨argskillnadsformeln CIE ∆Eab. Underdessa utv¨arderingar har systemet m¨att f¨argskillnader p˚a ∆Eab < 14 och ∆Eab < 30 f¨or ett respektivematt och blankt prov. Dessa resultat visar stora f¨argskillnader som ¨ar mest sannolikt orsakasav det l˚aga signal-brusf¨orh˚allande f¨or korta v˚agl¨angder p˚a grund av ljusk¨allas position och spektralaf¨ordelning. Slutligen demonstreras systemets f¨orm˚aga att g¨ora vinkeluppl¨osta m¨atningarav goniokromatiska prover, vars f¨arg skiftar med betraktningsvinkeln. Systemet detekterarf¨argskiftningen framg˚angsrikt f¨or betraktningsvinklar 0 till 45 grader fr˚an ytnormalen.

Place, publisher, year, edition, pages
2014. , 30 p.
Keyword [en]
goniophotometric, hyper spectral, colorimetry, optical characterization
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:umu:diva-97670OAI: diva2:775537
Subject / course
Fysik D - examensarbete
Educational program
Master of Science Programme in Engineering Physics
2014-08-29, Universitetsklubben, Universum, Umeå, 09:00 (Swedish)
Available from: 2015-01-09 Created: 2015-01-03 Last updated: 2015-01-09Bibliographically approved

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