The planar perfect lens: physical requirements and possible alternative realizations

Several alternative possibilities of how to create an electromagnetic device being able to reconstruct near-field distribution of a source with sub-wavelength resolution (so-called perfect lens) are considered. It is shown that there is a variety of such means not involving double-negative (left-handed, or Veselago) materials or periodical backward-wave structures. It is demonstrated that devices working in a similar manner can be constructed using planar grids or material sheets imposing necessary boundary conditions at two parallel planes in air.