Photometric stereo

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Photometric stereo is a technique in computer vision for estimating the surface normals of objects by observing that object under different lighting conditions.

The technique was originally introduced by Woodham in 1980.[1] The special case where the data is a single image is known as shape from shading, and was analyzed by B. K. P. Horn in 1989.[2]

Methods

Under Woodham's original assumptions — Lambertian reflectance, known point-like distant light sources, and uniform albedo — the problem can be solved by inverting the linear equation I=n\cdot L, where I is a (known) vector of m observed intensities, n is the (unknown) surface normal, and L is a (known) 3\times m matrix of normalized light directions.

Photometric stereo has since been generalized to many other situations, including non-uniform albedo, extended light sources, and non-Lambertian surface finishes.[3] Current research aims to make the method work in the presence of projected shadows, highlights, and non-uniform lighting.

See also

References

  1. ↑ Woodham, R.J. 1980. Photometric method for determining surface orientation from multiple images. Optical Engineerings 19, I, 139-144.
  2. ↑ B. K. P. Horn, 1989. Obtaining shape from shading information. In B. K. P. Horn and M. J. Brooks, eds., Shape from Shading, pages 121–171. MIT Press.
  3. ↑ "A Photometric Stereo Approach to Face Recognition". University of the West of England. Retrieved 2011-03-27. 
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