Double Imaging by a Periodic Bi-Fold Transformation Medium

In this paper, double imaging by a periodic bi-fold transformation medium is presented. It is shown that a periodic array of axisymmetric isovolumetric coordinate transformation metamaterials has a double imaging with different angles of sight ±θ due to peculiar refractions on the surface of the medium. The condition for the double imaging is presented and the double imaging operations are confirmed based on ray tracing and full-wave simulations.