Secure documents - methods and applications

A paper substrate having a laser ablated field area comprising an array of a plurality of laser-formed partial ablations that do not completely pierce the paper, the array having a density rate of ablations of at least 600 ablations per square centimeter, the partial ablations are not readily ascertainable by the unaided eye when viewed at an angle approximately perpendicular to a surface of the substrate using reflected light, and not readily ascertainable when viewed at an angle approximately perpendicular to the surface of the substrate but using light transmitted through the substrate, whereby when the surface is illuminated by a light source located at an angle relative to the surface of the substrate and viewed from a position at substantially the same angle relative to the surface as the light source the laser ablations appear lighter than the substrate outside the laser ablated field area.

A method of verifying a document comprising providing a paper substrate having an array of a plurality of laser formed microperforations separated by a land area, the array of microperforations having a diameter in the range of 80 to 120 microns, the land area separating adjacent microperforations being at least 600 microns, wherein the paper substrate when copied on reprographic equipment reproduces as a field of visible dots.

A method for creating a synthetic watermark in a paper substrate which comprises providing a paper substrate, applying a laser to the substrate to form partial ablations in the substrate in an area array having a density of at least 600 ablations per square centimeter.