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Abstract

A system for encoding data into and decoding data from a coded pattern using angular symbology in which symbols are represented by angular orientations of data modulation patterns relative to a reference modulation pattern. The modulation patterns are selected to have components that are localized in a Fourier transform domain. An example of a modulation pattern is a sinusoidal linear pattern in which spatial frequency and angular orientation are localized in the magnitude Fourier transform domain. In one embodiment of the present invention, one or more symbols may be encoded in one or more portions of an image by varying a characteristic of one or more elements of the image in accordance with the data and reference modulation patterns. An element may be image pixels, and the coded pattern is represented by variations to the intensities of the pixels. The coded pattern may be reproduced as a grayscale texture or combined with a non-coded image by adding a graininess to the image. To decode the coded pattern the system performs a two-dimensional fast Fourier transform and identifies the spatial frequencies and relative angular orientations associated with the respective modulation patterns. The system then associates the angular orientations with symbols and arranges the symbols in accordance with the associated spatial frequency values to reproduce the data.

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First Claim