Document Security Utilizing Color Gradients

Abstract

The present invention includes apparatus and methods for printing and verifying postage stamps on demand via a personal postage stamp printer. The indicium by which the stamp is printed includes a color stripe and a data field including authentication data that corresponds to the color stripe. To authenticate the stamp, the authentication data in the data field is read and compared with authentication data extracted from the color stripe.

1 . A method incorporating authentication data into a value indicia of a mailpiece comprising:
 (A) scanning a color stripe;   (B) generating color gradient data indicative of at least one characteristic of a variation in intensity of at least one color component along a length of the color stripe.   the color gradient data including a color region representing the authentication data by a substantially continuous sinusoidal variation of at least one color component of the color region, the at least one color component being represented by at least one of a wavelength, amplitude and phase variation.   
     
     
         2 . The method according to  claim 1 , further comprising:
 (A) reading a barcode adjacent to the color stripe to generate barcode data; and   (B) comparing the barcode data with the color gradient data.   
     
     
         3 . The method according to  claim 2 , wherein the color stripe and the barcode are both part of a postage meter indicia, and the comparing step is to authenticate the postage meter indicia. 
     
     
         4 . The method according to  claim 3 , wherein the barcode is a two-dimensional barcode. 
     
     
         5 . The method according to  claim 1 , wherein the variation is a sinusoidal variation and the at least one characteristic is at least one of wavelength, amplitude and phase of the sinusoidal variation.