Concealing information in security hologram using interferometry

A new method utilizing holographic interferometry technique is described to conceal information in security holograms for enhancing their anti-counterfeiting ability. This concealed information can only be imitated if security hologram is illuminated through correct decoding wavefront generated through a key hologram. In decoding process, three spatially separated focus spots emerge at predefined positions which upon divergence further generate interferometric fringes modulated with concealed information in them. When security hologram is perfectly aligned, interferometric fringes disappear and concealed information becomes visible. The advantage of encoding through this technique lies in the fact that relative repositioning of key and security hologram becomes much easier and also additionally brings multifold improvement in the security level of the verification systems.