Patent ID: 7745778
Filing Date: 2010-06-29
Classification: G02B,G06K

Abstract:
1. An identification system, comprising: at least one tag having encoded information attached to a surface of an object to be identified, said tag comprising a first elliptical polarization filter, said first elliptical polarization filter comprising a first frequency selective surface (FSS) disposed on said surface, said first FSS comprising least a first periodic pattern of spaced apart electrically conductive lines having a sub-wavelength line-to-line spacing, said lines including at least one subwavelength geometrical feature, said pattern being operable to receive incident radiation having a wavelength between 400 nm and 1 mm and output radiation having a phase differential for a first orthogonal linear polarization state relative to the other linear polarization state; a receiver remotely located from said tag operable for differentially attenuating said first and said other orthogonal polarization states comprising a second elliptical polarizing filter coupled to receive said output radiation, said second elliptical filter comprising a second FSS comprising least one periodic second pattern of spaced apart electrically conductive lines having a sub-wavelength line-to-line spacing, said lines including at least one subwavelength geometrical feature, and a first linear polarizer optically coupled to said second elliptical polarizing filter; a photodetector optically coupled to said linear polarizer for generating an intensity pattern, and a processor operable for determining whether said intensity pattern corresponds to said encoded information.