Identifying a dot-matrix hologram by the deviations of the fringe positions of its grating dots

Abstract

Dot-matrix holograms created by two-beam writers usually contain two-dimensional grating dots. Although the dot positions may be accurate, the fringe positions of the dots are randomly determined. The random fringe positions are good tools to identify a hologram. A grating position-deviation coefficient derived from the fringe position difference of two grating dots with the same pitch and the same orientation is defined and it is used as data to identify a dot-matrix hologram. Experiments have proved the proposed method practical and feasible. Because the fringe position difference between the two grating dots with the same pitch and the same orientation is difficult to reproduce, it is excellent for anticounterfeiting.