Patent ID: 7345747
Filing Date: 2008-03-18
Classification: G03H,G07D

Abstract:
1. An arrangement for checking optical diffraction structures on documents comprising: an illumination unit for illuminating at least the diffraction structure of the document and a sensor unit for detecting light components that are diffracted at defined angles being arranged above a support surface of the document; said sensor unit being arranged orthogonally above the support surface of the document; said illumination unit containing at least two monochromatic light sources which are arranged so as to emit light bundles at defined incident angles with respect to a surface normal of the document directed to the diffraction structure and which can be switched on sequentially; at least one light source having an incident angle that corresponds in direction and degree to a diffraction angle at which an intensity maximum of the diffraction pattern that is generated in a structure-specific manner would occur if the diffraction structure were illuminated from the direction of the sensor unit; and said sensor unit being synchronized with the illumination unit in order to detect diffraction signals associated with the switched on light sources.