1. Introduction
Light plays a vital role in our daily lives while communicating with the world around us. But while the world is made of objects, these objects do not communicate their properties directly to an observer; they rather fill the space around them with a pattern of light rays that is perceived and interpreted by the human visual system. Such a pattern of light rays can be measured, yielding the now ubiquitous images and videos. Visual information plays an increasing role in our lives and evolution and it is believed that up to 50% of the human brain is involved in some way in processing visual information.