Diffractive structure of semitransparent hologram overlays applied to prevent document forgery was analysed by a combination of microscopic and spectroscopic methods. It was shown that the diffractive structure is fully covered by a polymer. The shortest period was possible to detect by confocal optical microscope. The properties of diffracted light were analysed by spectrogoniometer; good correlation with the period of the structure was obtained. Therefore spectrogoniometric measurements may be applied to detect the period of diffractive structure inside semitransparent hologram overlays.
COBISS.SI-ID: 4626458