Illumination control as a means of enhancing image features in active vision systems.

In this paper, illumination control has been studied as a means of enhancing image features. Such features are points, edges, and shading patterns, which provide important cues for the interpretation of an image of a scene and the recognition of objects present in it. Based on approximate expressions for the reflectance map of Lambertian and general surfaces, a rigorous discussion on how intensity gradients are dependent on the direction of the light is presented. Subsequently, three criteria for the illumination of convex-shaped cylindrical surfaces are given. Two of these, the contrast equalization criterion and the max-min equalization criterion, are developed for optimal illumination of convex polyhedrons. The third, denoted shading enhancement, is applicable for the illumination of convex curved objects. Examples illustrate the merit of the criteria presented.