Enhanced method to improve the shift tolerance of double random phase encoding

There is growing interest of the successful application of double random phase encoding in optical encryption techniques. Nevertheless, this method has some weaknesses such as the problem of optical axis alignment. A few modified schemes have been proposed in order to improve the misalignment but not for the DRPE. This paper addresses a simulated solution of DRPE scheme based on 4f optically system to improve the shift tolerance of the decrypting key by using deterministic phase masks instead of random phase masks. The main advantage of deterministic phase masks is the compact and tiny size of the keys and they are long enough so that an attacker cannot try any possible combinations. Initial feasibility studies have been undertaken and show a sufficient enhancement to axis alignment as compared to the conventional DRPE. We describe the principle of masks generation and present the simulations results which have been made to evaluate its performance in terms of data loss and shift of the decrypting key in the Fourier plane.