  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.
