Seok Hee JEON, Young Gwan HWANG¹, and Sang Keun GIL^1*

Department of Electronic Engineering, The University of Incheon, Incheon 402-749, Korea
¹Department of Electronic Engineering, The University of Suwon, Suwon 440-600, Korea

(Received December 20, 2007; Accepted June 3, 2008)

In this paper we propose an encryption/decryption technique of gray-level image information using an on-axis 2-f digital holographic optical encrypting system with two-step phase-shifting method. This technique reduces the number of holograms in phase-shifting digital holography and minimizes the setup of the encryption system more than multi-step phase-shifting technique. We are able to get the complete decrypted image by controlling the K-ratio which is defined as the reference beam intensity versus the object beam intensity. We remove the DC-term of the phase-shifting digital hologram to reconstruct and decrypt the original image information. Simulation results show that the proposed method can be used for encryption and decryption of a 256 gray-level image. Also, the result shows some errors of the decrypted image according to K-ratio.

Key words: optical encryption, phase-shifting digital holography, Fourier optics, optical signal processing

^*E-mail address: skgil@suwon.ac.kr