Achieving Perfect Imaging beyond Passive and Active Obstacles by a   Transformed Bilayer Lens
  A bilayer lens is proposed based on transformation optics. It is shown that Pendry's perfect lens, perfect bilayer lens made of indefinite media, and the concept of compensated media are well unified under the scope of the proposed bilayer lens. Using this concept, we also demonstrate how one is able to achieve perfect imaging beyond passive objects or active sources which are present in front of the lens. 
Wei Yan, Min Yan, and Min Qiu