Covert machine-readable micro-optic feature embedded in lens layer

A method of making a micro-optic security device, the method comprising:

• providing an optical spacer having a first side and a second side;
• forming an icon layer comprising a plurality of image icons of a first color on the first side of the optical spacer;
• and
• forming a focusing layer comprising a plurality of refractive focusing elements on the second side of the optical spacer,
• wherein the plurality of refractive focusing elements project a synthetically magnified image of the plurality of image icons,
• wherein image icons of the first color project a component of the synthetically magnified image that is of the first color, and
• wherein refractive focusing elements of the plurality of refractive focusing elements are doped with a machine-readable taggant which emits a characteristic signal at a first frequency in the ultraviolet spectrum.