Investigation of two colour photometric stereo for the surface inspection of steel bars

Yuan Fei Chen

Investigation of two colour photometric stereo for the surface inspection of steel bars

Yuan Fei Chen

Montanuniversität

Publikation: Thesis / Studienabschlussarbeiten und Habilitationsschriften › Diplomarbeit › Begutachtung

Abstract

Diese Arbeit beschäftigt sich mit einer berührungslosen optischen Messmethode, genannt Zwei Farben Photometric Stereo", sowie der dazugehörigen Kalibrationstechnik. Das Grundprinzip besteht darin, ein Objekt von zwei bekannten Punkten aus mit jeweils einer blauen und einer grünen Lichtquelle zu beleuchten, und nur ein Bild von einer fixierten Position aufzunehmen. Dieses Bild wird nun so aufgeteilt, dass man es den jeweiligen Lichtquellen zuordnen kann. Mittels der so erhaltenen Intensitäten kann man Rückschlüsse auf das Rückstrahlverhalten und die Oberflächennormale ziehen. Der Ablauf der Arbeit ist folgender: Aufgrund der ungleichmässigen Beleuchtung muss man zuerst den Messaufbau mit einem bekannten Objekt kalibrieren. Die Kalibration ermöglicht es die aufgenommenen Bilder zu korrigieren und so das tatsächliche Rückstrahlvermögen und die tatsächliche Oberflächennormale zu berechnen. Diese Technik kann in vielen Bereichen der Qualitätsprüfung von Oberflächen eingesetzt werden. Das Verfahren nutzt günstige Bauteile, benötigt kein langwieriges Initialisieren und es ist auch Bauteil unabhängig. In dieser Arbeit werden ebenfalls Ergebnisse eines experimentellen Versuchsaufbaus gezeigt.

Originalsprache	Englisch
Qualifikation	Dipl.-Ing.
Gradverleihende Hochschule	Montanuniversität
Betreuer/-in / Berater/-in	O'Leary, Paul, Betreuer (intern)
Publikationsstatus	Veröffentlicht - 14 Okt. 2005

Schlagwörter

Zwei Farben Photometric Stereo
Oberflächennormale
Rückstrahlverhalten

Dieses zitieren

@phdthesis{c28005f374684106a578db6afd72211b,

title = "Investigation of two colour photometric stereo for the surface inspection of steel bars",

abstract = "This thesis presents the optical non-contact surface measurement method, termed {"}Two Colour Photometric Stereo{"}, along with its calibration techniques. The principle is to take two images of an object from the same camera view, while illuminating from two known directions respectively with a blue and a green light source. Based on the intensity values in the two different images, one can estimate the surface normal vectors and surface albedo. The relative position of the light source relative to the camera are determined from a calibration process. During the calibration a target is observed which enables the determination of the calibration matrix. With the calibration matrix, one can compute a measured pixel intensity. Whereby the intensity is corrected to eliminate the effects of nonuniform illumination. From the corrected images, one can obtain the reconstructed albedo and surface normals. The technique has applications in automatic inspection for quality control of a wide range of manufactured and processed surfaces, it uses a low-cost fixed lighting configuration, requires no initial training, and is largely pose invariant. Experimental results are presented in the thesis.",

keywords = "Zwei Farben Photometric Stereo, Oberfl{\"a}chennormale, R{\"u}ckstrahlverhalten, Two colour Photometric Stereo, Surface Normal, Albedo",

author = "Chen, {Yuan Fei}",

year = "2005",

month = oct,

day = "14",

language = "English",

type = "Diploma Thesis",

school = "Montanuniversitaet Leoben (000)",

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TY - THES

T1 - Investigation of two colour photometric stereo for the surface inspection of steel bars

AU - Chen, Yuan Fei

PY - 2005/10/14

Y1 - 2005/10/14

N2 - This thesis presents the optical non-contact surface measurement method, termed "Two Colour Photometric Stereo", along with its calibration techniques. The principle is to take two images of an object from the same camera view, while illuminating from two known directions respectively with a blue and a green light source. Based on the intensity values in the two different images, one can estimate the surface normal vectors and surface albedo. The relative position of the light source relative to the camera are determined from a calibration process. During the calibration a target is observed which enables the determination of the calibration matrix. With the calibration matrix, one can compute a measured pixel intensity. Whereby the intensity is corrected to eliminate the effects of nonuniform illumination. From the corrected images, one can obtain the reconstructed albedo and surface normals. The technique has applications in automatic inspection for quality control of a wide range of manufactured and processed surfaces, it uses a low-cost fixed lighting configuration, requires no initial training, and is largely pose invariant. Experimental results are presented in the thesis.

AB - This thesis presents the optical non-contact surface measurement method, termed "Two Colour Photometric Stereo", along with its calibration techniques. The principle is to take two images of an object from the same camera view, while illuminating from two known directions respectively with a blue and a green light source. Based on the intensity values in the two different images, one can estimate the surface normal vectors and surface albedo. The relative position of the light source relative to the camera are determined from a calibration process. During the calibration a target is observed which enables the determination of the calibration matrix. With the calibration matrix, one can compute a measured pixel intensity. Whereby the intensity is corrected to eliminate the effects of nonuniform illumination. From the corrected images, one can obtain the reconstructed albedo and surface normals. The technique has applications in automatic inspection for quality control of a wide range of manufactured and processed surfaces, it uses a low-cost fixed lighting configuration, requires no initial training, and is largely pose invariant. Experimental results are presented in the thesis.

KW - Zwei Farben Photometric Stereo

KW - Oberflächennormale

KW - Rückstrahlverhalten

KW - Two colour Photometric Stereo

KW - Surface Normal

KW - Albedo

M3 - Diploma Thesis

ER -