Elimination of specular surface-reflectance using polarized and unpolarized light
Highlights are an unwanted phenomenon in computer vision, they may severely hamper the use of standard image processing algorithms. Highlights are caused by specular reflectance, thus the objective is to eliminate this type of reflectance. In this paper, a new polarization-based method is introduced to separate the diffuse and specular component of reflection.
A polarisation filter can reduce the intensity of higlights but can not completly eliminate this troublesome effect. Two images input with different orientation of a polarisation filter in front of a camera provide the necessary information to calculate the intensity of specular reflectance on plane surfaces. A third image with different orientation is necessary to determine specular reflectance in three-dimensional scenes. The specular reflectance is substracted from the original image, providing an image without highlights.
Both polarized and unpolarized light is used in this paper. Polarized light has the advantage, that it reduces the degrees of freedom of reflected light, thus no knowlegde about surface properties and image aquisition geometry is required, when specular reflectance shall be removed.
The method introduced in this paper can be applied to all kinds of dielectrics including textured surfaces. Highlights can be removed both from greylevel images and colour images, in the latter case yielding colour constancy.
If the inspected objects are placed at a definite position, it is possible to aquire most of the required data for highlight-elimination during a training phase. In this way, highlights can be removed with just one image input, even if the source of illumination is changing. Thus the hardware-requirements to the vision system are considerably reduced, narrowing the gap between research and practical applications.
KeywordsPhysics-based vision elimination of highlights polarization image-restauration Fresnel reflectance model
Unable to display preview. Download preview PDF.
- M. Born, E. Wolf: Principles of Optics, Pergamon, London 1965Google Scholar
- F.R. Kessler: Physik: Optik II. Deutsches Institut für Fernstudien, Tübingen 1978Google Scholar
- G.J. Klinker, S.A. Shafer, T. Kanade: Using a color reflection model to separate highlights from object color. 1. ICCV: pp. 145–150, London 1987Google Scholar
- G.J. Klinker: A Physical Approach to Color Image Understanding. Wellesley, USA, 1993, A.K. Peters Ltd.Google Scholar
- K. Koshikawa: A polarimetric approach to shape understanding of glossy objects. 3. International Joint Conference on Artificial Intelligence, pp. 493–495, 1979Google Scholar
- V. Müller: Analysis of Optical Reflection — A new Approach to Surface Inspection, In: W.G. Kropatsch, H. Bischof (Eds.): Mustererkennung 1994. 16. Symposium of the German Working Group on Pattern Recognition (DAGM) and 18. Workshop of the Austrian Working Group on Pattern Recognition öAGM, pp. 74–80, Wien 1994Google Scholar
- V. Müller: Polarization-Based Separation of Diffuse and Specular Surface-Reflection, In G. Sagerer, S. Posch, F. Kummert (Eds.): Mustererkennung 1995, pp. 202–209, Springer, Berlin 1995Google Scholar
- S.W. Lee: Understanding of Surface Reflection in Computer Vision by Color and Multiple Views, PhD thesis, University of Pennsylvania, 1991Google Scholar
- H. Li, H. Burkhardt: Prototypentwicklung von Algorithmen zur Orientierungsschätzung von Pralinen aufbauend auf Grauwertmerkmalen (I) — Prinzip und Implementierung. Interner Bericht 3/91, Technische Informatik I, TU-HH, Dezember 1991Google Scholar
- S.K. Nayar, X.S. Fang, T. Boult: Removal of Specularities Using Color and Polarization, IEEE Conference on Computer Vision and Pattern Recognition, pp. 583–590, New York 1993Google Scholar
- B.T. Phong: Illumination for computer generated pictures. Commun. ACM 18, (6), pp. 311–317, June 1975Google Scholar
- S. Shafer: Using Color to Separate Reflection Compenents. Color Research and Applications, Vol. 10, pp. 210–218, 1985Google Scholar
- R. Siegel, J.R. Howell: Thermal radiation heat transfer. Taylor&Francis, Washington 1992Google Scholar
- L.B. Wolff: Spectral and polarization stereo methods using a single light source. 1. ICCV, pp. 708–715, London 1987Google Scholar
- L.B. Wolff: Polarization Methods in Computer Vision, PhD thesis, Columbia University, 1990Google Scholar
- L.B. Wolff, T.E. Boult: Constraining object features using a polarization reflectance model, IEEE Trans. on Pattern Analysis and Machine Intelligence Vol. 13 (6), pp. 635–657, 1991Google Scholar