Image foils providing a synthetic integral image

Method for authentication of an object having a polymer foil stack provided at a surface of said object, said polymer foil stack comprising at least one polymer foil, a first interface of said polymer foil stack comprising optically distinguishable image data bearer structures in a first array, a second interface of said polymer foil stack having focusing elements in a second array, said second interface being provided at a distance from said first interface, said image data bearer structures in said first array being repeated with first object distances in a first object direction and with second object distances in a second object direction, provided at a first angle with respect to said first object direction, said focusing elements in said second array being repeated with first focusing element distances in a first focusing element direction and with second focusing element distances in a second focusing element direction, provided at a second angle with respect to said first focusing element direction, wherein said first focusing element direction is parallel to said first object direction, wherein said second focusing element direction is parallel to said second object direction, wherein both first ratios between corresponding pairs of said first object distances and said first focusing element distances and second ratios between corresponding pairs of said second object distances and said second focusing element distances are equal to unity;

• said method comprising the steps of:
• moving said polymer foil stack between a first distance relative to a viewer and a second distance relative a viewer, said second distance being considerably smaller than said first distance;
• wherein rays from said polymer foil stack forming a first synthetic integral image corresponding to said image data bearer structure do not converge at said first distance;
• and
• observing said polymer foil stack at said second distance;
• determining authenticity of said object when said first synthetic integral image corresponding to said image data bearer structures appears at said second distance.