Patent ID: 7991186
Filing Date: 2011-08-02
Classification: G06T,G07D

Abstract:
1. A method for generating a printed security image on a banknote, said security image comprising an original image and a security pattern, the method comprising the steps of: obtaining said security pattern, wherein said security pattern in the spatial domain is the inverse Fourier transform of the combination in the frequency domain between the Fourier transform of an auxiliary image and a radially symmetric, two-dimensional pattern, said two-dimensional pattern created by sweeping a self-similar, one-dimensional function along a 360-degree arc, said security pattern being detectable from the maximum value of the cross-correlation of said one-dimensional function with the Fourier transform of one line of said banknote, said line being sampled along any arbitrary direction and with any resolution between 50 and 1200 dots per inch; generating the security image in the spatial domain by merging at least one color of at least a part of the original image with the security pattern.