| 摘要 |
Data is acquired of three images of an object, each image taken under illumination from a different direction S101, it is determined which pixels are in shadow such that data is only available from two images S103 and a range of possible solutions for the gradient of the surface normal of the pixel in shadow are calculated from the two images S105, then a solution is selected using the integrability of the gradient field over an area of the object as a constraint, and minimising a cost function S107. Thus photometric stereo may be used with just three images. The solution may be selected by using a least squares analysis and the constraint that the object is a continuous piecewise polynomial. The cost function may be expressed in terms of a regulisation parameter which is used to compensate for noise. Three spaced light sources may be used, a camera capturing images in sequence as each of the light sources are activated, or each light source may provide radiation of a different frequency or colour, the three images being captured simultaneously, allowing moving objects to be imaged. A three dimensional (3D) image may be generated S109. |
