Dynamic appearance-changing optical devices (dacod) printed in a shaped magnetic field including printable fresnel structures

Abstract From the Canadian patent

A printed image is disclosed wherein the image may be in the form of an array of magnetically aligned platelets or flakes that may by uniform in shape and size and wherein the flakes are arranged in a particularly manner to form optically illusive images useful as security devices or useful in beam steering applications. In one embodiment of this invention printed array is disclosed a plurality of concentric rings of magnetically aligned platelets disposed upon a substrate in the form of a Fresnel structure preferably a Fresnel reflector. Advantageously since the magnetic field can be controlled with respect to strength and direction one can easily design a field that will correct for …