This looks somewhat like the concept behind a fresnel zone plate [1] - in general these are highly dispersive (only work at one frequency) so it looks like they have done something to address this. Many (30+) years ago my final year project at university was trying to dynamically synthesise lenses using by electronically manipulating the phase response across a liquid crystal substrate - technology wasn't really there at the time but always thought that it would have been an interesting avenue to follow up on.

[1] http://en.wikipedia.org/wiki/Zone_plate