**Next:**Active
Vision
**Up:**Visual-motor
Systems
**Previous:**Attention
and Change Detection
###
Active Differential Photometric
Stereo

*H. Pekau, J.J. Clark*
In previous research our group, in conjunction with Prof. Iwahori of
the Nagoya Technical Institute, had developed a method for obtaining the
shape and absolute depth to a surface having an arbitrary reflectance map.
This algorithm utilized the 3-D controlled motion of a point light source
near to the object. This algorithm, however, required the computation of
the gradient of the image intensity with respect to the light source position.
As such, the solution provided by the algorithm will be extremely sensitive
to noise in the image measurements and errors in the positioning of the
light source. In our current work, we have found that the Clark-Iwahori
differential algorithm can be transformed, via application of the divergence
theorem, into an algorithm that requires only knowledge of the integral
of image intensity over various surfaces and volumes in the light source
position space. No derivatives need be computed. This integral algorithm
promises to be much more robust in the face of image noise and position
errors. We have implemented this new algorithm using the facilities of
the CIM Artificial Perception Lab. For the purposes of this experiment
we constructed a prototype of a planar distributed illumination source,
shown below.

*The prototype of the planar extended light source used in the active
differential shape from shading experiment.*

*Annual Report*

*Fri Nov 26 23:00:32 GMT 1999*