Photometric Method For Determining Surface Orientation From Multiple Images

TLDR

The imaging geometry remains unchanged, so image‑point correspondence is known a priori. The study introduces a novel technique called photometric stereo. Photometric stereo varies illumination direction while keeping the viewing direction fixed, using radiance values at each image location to determine surface orientation, and can be applied both generally to compute orientation at each point and specifically to identify points with a given orientation. The method provides sufficient information to determine surface orientation at each image point, is employed in computer‑based image understanding, and its applications are demonstrated with synthesized examples. It can be applied in two ways.

Abstract

A novel technique called photometric stereo is introduced. The idea of photometric stereo is to vary the direction of incident illumination between successive images, while holding the viewing direction constant. It is shown that this provides sufficient information to determine surface orientation at each image point. Since the imaging geometry is not changed, the correspondence between image points is known a priori. The technique is photometric because it uses the radiance values recorded at a single image location, in successive views, rather than the relative positions of displaced features. Photometric stereo is used in computer-based image understanding. It can be applied in two ways. First, it is a general technique for deter-mining surface orientation at each image point. Second, it is a technique for determining object points that have a particular surface orientation. These applications are illustrated using synthesized examples.