Optically-based access control system

Abstract

Abstract An optically-based coded card identification system is provided in which a card having an access code defined by adjacent differently-polarized elements used in a transmissive or reflective mode is interrogated through a deep red or near infrared transmissive filter as the card is pased by a source of illumination. The use of polarization coupled with the adjacency of the differently-polarized elements makes the code nearly invisible to the naked eye, with the code being made more invisible due to the low visible light transmission of the filter on the face of the card. In one embodiment, coding for the cards is provided by overlying layers of material polarized in different directions, with portions of the layers provided with offset apertures so that light through an aperture in one layer is polaried by an unapertured portion of the adjacent layer immediately thereunder. Alternatively, the same coding effect may be achieved by providing two differently stretched overlying layers of specially prepared transparent material, overprinted front and back with offset iodine patterns, with the iodine causing a polarization characteristic to be imparted to the material at the overprinted area to provide the access code. In one embodiment, the coding elements are arranged in two rows defining complementary codes such that areas of complementary polarizations are simultaneously decoded to provide complementary signals for increasing security and the signal-to-noise ratio for the system. In a further embodiment, an unpolarized detector coupled to a pulsed output detector is used to detect the pulses produced by the light and dark areas of a bar code provided by ordinary printing of a bogus card and to inhibit access upon detection of such a bogus card.

Inventors

• 👤 Aaron A. Galvin
• 👤 Roy L. Harvey
• 👤 Kenneth J. Leff

Bibliographic Details