Invisible Cloaks and Functional Thinking

To make an image invisible, they much use a sequence of lenses to bend the light around a given object. In this way they need to think of the path for light as a function of the position of each lens.

http://www.rochester.edu/newscenter/watch-rochester-cloak-uses-ordinary-lenses-to-hide-objects-across-continuous-range-of-angles-70592/