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Holograms; security holograms; optical security; extended fractional Fourier transforms.

This paper describes a simple method for making dual beam encoded extended fractional Fourier transform (EFRT) security holograms. The hologram possesses different stages of encoding so that security features are concealed and remain invisible to the counterfeiter. These concealed and encoded anticounterfeit security features in the security hologram can only be read through a key hologram. Key hologram also facilitates in-built repositioning of security hologram. The method of fabrication, the principle of reconstruction and the experimental results are presented.

Amit K Sharma^{1 2} D P Chhachhia¹ D Mohan³ A K Aggarwal¹

1. Coherent Optics Division, Central Scienti¯c Instruments Organisation, Sector 30, Chandigarh 160 030, India
2. Department of Applied Science, IIMT Engineering College, Meerut 250 001, India
3. Department of Physics, Panjab University, Chandigarh 160 014, India

Published

January 2008

Manuscript received

16 January 2007

Manuscript revised

21 August 2007

Accepted

28 August 2007