US Patent 7533022 Printed media with machine readable markings

A printed media, such as a card bears a visible light image, such as a picture or photograph, for viewing by a human. A machine readable array of infra-red dots is located over the visible light image. In a preferred embodiment the infra-red dots encode sound recording data associated with the visible light image. Solomon-Reed encoding and checkerboard modulation of the dots is employed to ensure reliable retrieval of the sound recording.