Geometrical phase image encryption obtained with space-variant subwavelength gratings
Gabriel Biener, Avi Niv, Vladimir Kleiner, Erez Hasman · Optics Letters · 2005
An optical encryption method based on a geometrical phase produced by space-variant polarization manipulation is presented. The decrypted picture is retrieved either by a polarization measurement of the beam emerging from the encrypted element or by a single intensity measurement of the beam transmitted through the encrypted element followed by an optical key element. Both elements are realized by use of computer-generated space-variant subwavelength dielectric gratings. Theoretical analyses of the optical concept are presented along with experimental results.