Patent ID: 8451322
Filing Date: 2013-05-28
Classification: G01B,G06T

Abstract:
1. An apparatus for determining the gradients of the surface normals of an object, comprising: a receiving unit configured to receive data of three 2D images of said object, wherein each image is captured under illumination from a different direction; an establishing unit configured to establish which pixels of the image are in shadow such that there is only data available from two images from these pixels; a determining unit configured to determine a range of possible solutions for the gradient of the surface normal of a shadowed pixel using the data available for the two images; and a selecting unit configured to select a solution for the gradient using the integrability of the gradient field over an area of the object as a constraint and minimizing a cost function, wherein the determining unit is configured to determine the range of possible solutions by expressing the normal as the albedo scaled surface normal b: wherein c is [c where e projecting b into a 2D gradient space using the operator P[x