The solution of several problems in Computer Vision benefits from analyzing collections of images, instead of a single image, of a scene that has variant and invariant elements that give important additional clues to interpret scene structure. If the acquisition is done specially for some vision task, then acquisition parameters can be set up so as to simplify the interpretation task. In particular, changes in scene illumination can significantly increase information about scene structure in a collection of images. In this work, the concept of active illumination, that is, controlled illumination that interferes on the scene at acquisition time, is explored to solve some Computer Vision tasks. For instance, a minimal structured light pattern is proposed to solve stereo correspondence problem, while intensity modulation is used to help in foreground/background segmentation task as well as in image tone enhancement.