  An elliptical invisible cloak is proposed using a coordinate transformation
in the elliptical-cylindrical coordinate system, which crushes the cloaked
object to a line segment instead of a point. The elliptical cloak is reduced to
a nearly-circular cloak if the elliptical focus becomes very small. The
advantage of the proposed invisibility cloak is that none of the parameters is
singular and the changing range of all parameters is relatively small.

Optics;Classical Physics