Determining Surface Orientations Of Specular Surfaces By Intensity Encoded Illumination

Shree K. Nayar; Arthur C. Sanderson

doi:10.1117/12.942867

12 March 1988 Determining Surface Orientations Of Specular Surfaces By Intensity Encoded Illumination

Shree K. Nayar, Arthur C. Sanderson

Proceedings Volume 0850, Optics, Illumination, and Image Sensing for Machine Vision II; (1988) https://doi.org/10.1117/12.942867
Event: Advances in Intelligent Robotics Systems, 1987, Cambridge, CA, United States

Abstract

This paper discusses an intensity encoded line source illumination approach to estimating the surface orientation of specular surfaces. The normalized brightness difference function (NBDF) is introduced as a real time invertible relationship between image irradiances and surface orientation, and provides the basis for estimation of the surface gradient using relative brightness values rather than calibrated photometric measurements. Two complementary line source intensity patterns are generated for each measurement, and a series of radial lines are scanned to span the surface gradient space. Experiments have estimated the accuracy of the orientation measurement to be within 2-3%. Sensitivity to variations in specularity, and the feasibility of the encoding technique are described. Careful attention to the illumination geometry, distant source approximation and computation speed will be required for the purpose of practical implementation. The use of line sources is most suited to applications where the relevant features can be extracted from a finite set of cross sections of the object. Inspection of solder and machined metal are examples of the application of intensity encoding.

Citation Download Citation

Shree K. Nayar and Arthur C. Sanderson "Determining Surface Orientations Of Specular Surfaces By Intensity Encoded Illumination", Proc. SPIE 0850, Optics, Illumination, and Image Sensing for Machine Vision II, (12 March 1988); https://doi.org/10.1117/12.942867

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