Near-field characteristics of periodic surface relief diffraction structures from far-field measurements

The method for testing effectiveness of holographic security devices

“…Intensity of the light reflected from the OVG depends on diffraction efficiency of the periodic structure. The investigations into diffraction efficiency can be done with measurements of angular dependency of the diffraction field intensity 3 . In this method one can theoretically calculate a profile of the periodic structure.…”

“…The method requires application of a laser in order to illuminate particular points of the OVG surface so the measurements are carrying out at several points by means of the scanning system. To obtain the foil profile parameters complicated calculations aimed at solution of the light diffraction inverse problem 3,4,5,6 are to be made. Measurements of the diffraction field upon a transparent holographic foil can be difficult to do because of low level of the reflected radiation power.…”