Browse Prior Art Database

Holographic Document Viewing System

IP.com Disclosure Number: IPCOM000091943D
Original Publication Date: 1968-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Magill, PJ: AUTHOR

Abstract

Protection of holograms against unauthorized duplication can be achieved. The holograms used are of the type termed image holograms in which a subject 0, as in drawing 1, is imaged near, or on, hologram plate H by virtue of lens L, the image being designated I. In the reconstruction, two real and two virtual images can be seen. One conjugate pair corresponds to the images of the object. The other conjugate pair corresponds to the images of the lens. When the hologram is placed in its original position and viewed from the side opposite the emulsion, a virtual image is seen, but difficult to view in its entirety. The virtual image of the lens, on the other hand, is easy to view in its entirety.

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Holographic Document Viewing System

Protection of holograms against unauthorized duplication can be achieved. The holograms used are of the type termed image holograms in which a subject 0, as in drawing 1, is imaged near, or on, hologram plate H by virtue of lens L, the image being designated I. In the reconstruction, two real and two virtual images can be seen. One conjugate pair corresponds to the images of the object. The other conjugate pair corresponds to the images of the lens. When the hologram is placed in its original position and viewed from the side opposite the emulsion, a virtual image is seen, but difficult to view in its entirety. The virtual image of the lens, on the other hand, is easy to view in its entirety.

Rotating the hologram 180 degrees about its vertical axis enables the viewer to perceive the real images of the object and the lens. To view the real image of the object in its entirety, it is necessary to view through the image of the lens. In other words, the lens establishes the limiting aperture of the system.

Thus, as in drawing 2, any unauthorized attempts to photograph the real image of the object in planes a or c other than the limiting aperture of the lens, in plane b, results in a document having less than the total information present.

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