Error Analysis of Surface Normals Determined by Radiometry

Surface normals can be computed from three images of a workpiece taken under three distinct lighting conditions without requiring surface continuity. Radiometric methods are susceptible to systematic errors such as: errors in the measurement of light source orientations; mismatched light source irra...

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Bibliographic Details
Published in:IEEE transactions on pattern analysis and machine intelligence 1983-11, Vol.PAMI-5 (6), p.631-645
Main Authors: Ray, Rajarshi, Birk, John, Kelley, Robert B.
Format: Article
Language:English
Subjects:
Applied sciences
Artificial intelligence
Calibration
Computer science
control theory
systems
Computer vision
edge extraction
Error analysis
Exact sciences and technology
Lambertian reflectance
Length measurement
Light sources
Microstructure
needle diagram
Optical collimators
Optical reflection
Pattern recognition. Digital image processing. Computational geometry
photometric stereo
radiometric stereo
Radiometry
reflectance mapping
sensitivity analysis
Size measurement
surface orientation
Testing
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Description
Summary:Surface normals can be computed from three images of a workpiece taken under three distinct lighting conditions without requiring surface continuity. Radiometric methods are susceptible to systematic errors such as: errors in the measurement of light source orientations; mismatched light source irradiance; detector nonlinearity; the presence of specular reflection or shadows; the spatial and spectral distribution of incident light; surface size, material, and microstructure; and the length and properties of the light source to target path. Typically, a 1° error in surface orientation of a Lambertian workpiece is caused by a 1 percent change in image intensity due to variations in incident light intensity or a 1° change in orientation of a collimated light source. Tests on a white nylon sphere indicate that by using modest error prevention and calibration schemes, surface angles off the camera axis can be computed within 5°, except at edge pixels. Equations for the sensitivity of surface normals to major error sources have been derived. Results of surface normal estimation and edge extraction experiments on various non-Lambertian and textured workpieces are also presented.
ISSN:0162-8828
1939-3539
DOI:10.1109/TPAMI.1983.4767454