Marking and authenticating documents with liquid crystal materials
First Claim
1. A method of repeatably authenticating documents comprising the steps of:
- (1) applying a liquid crystal material to the document, which material exhibits a predetermined response to an electrical or magnetic stimulus, and(2) examining the document for detectable characteristics of the predetermined response of the liquid crystal material when said stimulus is applied.
1 Assignment
0 Petitions
Accused Products
Abstract
Method and apparatus for authenticating documents such as government notes and currency, stock certificates, and the like by marking the document with an encapsulated dyed liquid crystal material and examining the document for unique optical characteristics of the mark. Reading apparatus for the document measures changes in reflectivity of the liquid crystal mark with changes in an electrical field applied thereto. In other embodiments, reflectivity is measured at a plurality of different wavelengths. In one embodiment, the dye absorbs in regions of the electromagnetic spectrum "invisible" to the human eye and the reading apparatus monitors reflectivity changes at these invisible wavelengths.
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Citations
14 Claims
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1. A method of repeatably authenticating documents comprising the steps of:
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(1) applying a liquid crystal material to the document, which material exhibits a predetermined response to an electrical or magnetic stimulus, and (2) examining the document for detectable characteristics of the predetermined response of the liquid crystal material when said stimulus is applied. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus for authenticating documents marked with an encapsulated liquid crystal matrial and dye comprising:
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means forming a read station for receiving the document or sample; means for directing a beam of radiation along an optical axis toward the read station; means for detecting radiation received from the read station along the optical axis; means for applying a field across the document; means for changing or modulating the value of the applied field; and means for comparing the values of detected radiation for different values of the applied field. - View Dependent Claims (11, 12, 13)
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14. A method of authenticating documents comprising the steps of:
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(1) applying a liquid crystal material to the document, which material exhibits a predetermined response to an external electrical or magnetic stimulus, (2) applying said external stimulus to said document, and (3) examining the document for a detectable characteristic of the response of the liquid crystal material.
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Specification