Online full-phase digital holographic encryption based on electrically addressed spatial light modulators

Abstract

A novel full-phase digital holographic encryption scheme with double random key masks, which are performed by electrically addressed liquid-crystal spatial light modulators for optical processing, is demonstrated. Phase-shifting digital holography is employed to generate the key holograms derived from the double key masks for implementing the encryption and decryption. The experimental results show the feasibility of the full-phase encryption scheme with computer-programmable key masks for securing data via online processing.Introduction: Double random-phase encoding [1], an extensively adopted method for optical encryption, uses two independent randomphase masks in the input plane and Fourier plane to convert a primary image to be encrypted into stationary white noise data. Moreover, double random-phase encoding in the Fresnel domain has been utilised to increase encryption dimensions and data security [2]. As an image encrypted by the double random-phase encoding method involves complex data that can be stored or transmitted using a holographic technique, optoelectronic information encryption [3, 4] based on phase-shifting digital holography has been proposed [5]. Moreover, phase encoding for optical encryption with a random-phase mask (such as ground glass or a phase mask film) can ensure high information security and is robust against counterfeiting [6][7][8][9][10]. In this Letter, a novel full-phase digital holographic encryption scheme using electrically addressed liquid-crystal spatial light modulators (LC-SLMs) [11,12] for online optical processing is proposed and demonstrated. The LC-SLMs are operated in phase-modulation mode [13] to represent the phase-encoded input object and the double random-phase masks in the object and reference arms. Owing to the fact that a primary image to be encrypted is phaseencoded into a phase object, the random-phase mask in the object arm can be treated as the role, of a phase diffuser the other key mask being for optical encryption. Furthermore, double random-phase masks using LC-SLMs can be electrically addressed during encryption procedures to overcome alignment problems encountered in practical optical encryption. This allows an encryption system to be programmable and provides potential applications with high data security via online processing.

One million fps digital holography

“…Introduction: Digital holography [1][2][3] is a technique capable of recording complex amplitude information of an object. In this technique, an interference fringe image of the object, which is called a hologram, is recorded by a CCD (charge-coupled device) or CMOS image sensor, and the complex amplitude of the object is numerically reconstructed from the electronically recorded hologram by the computer.…”