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US 7,710,623 B2Granted
Security hologram, method of recording same, and method of using same wherein the holographic imaging includes a single coherent beam of electromagnetic radiation in combination with a Lloyd's mirror to provide both reference and object beams
AssigneeE.I. du Pont de Nemours and Company
InventorSteven William MacMaster
Life of this patent
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Abstract
A security hologram is disclosed that is invisible to a human eye or to various optical detectors until the hologram is optically coupled to a suitable modifier (e.g., a prism). Also disclosed is a method of recording the security hologram and a method of using the hologram in security applications to establish authenticity of article(s).
Claims3
A method for making a security hologram comprising a covert image of an object, said method comprising the steps of:
- a) placing the object in contact with a first face of a prism, placing a first photosensitive film in contact with a second face of the prism, and holographically exposing the object, the prism and the first photosensitive film to a first coherent beam of electromagnetic radiation that is incident upon a third face of the prism wherein the first photosensitive film results in a first exposed photosensitive film having a H1 hologram of the object;
- b) curing the first exposed photosensitive film with electromagnetic radiation resulting in a first cured photosensitive film and removing the object from being proximate to the prism;
- and
- c) placing a second photosensitive film in contact with the first face of the prism, exposing the first cured photosensitive film, the prism and the second photosensitive film to a second coherent beam of electromagnetic radiation that is incident upon the third face of the prism wherein the second photosensitive film results in a second exposed photosensitive film having a H2 hologram , and curing the second photosensitive film with electromagnetic radiation resulting in a second cured photosensitive film, wherein the holographic imaging in step c) is effected using a single coherent beam of electromagnetic radiation in combination with a Lloyd's mirror to provide both reference and object beams.
1 more element
Dependencies are inferred from the claim text.