2-단계 위상 천이 디지털 홀로그래피를 이용한 이진 정보 광 암호화 기법

Abstract

We propose an optical encryption/decryption technique for a security system based on 2-step phase-shifting digital holography. Phase-shifting digital holography is used for recording phase and amplitude information on a CCD device. 2-step phase-shifting is implemented by moving the PZT mirror with phase step of 0 or π/2. The binary data and the key are expressed with random code and random phase patterns. The digital hologram is a Fourier transform hologram and is recorded on CCD with 256 gray level quantization. We remove the DC term of the digital hologram for data reconstruction, which is essential to reconstruct the original binary input data/image. The error evaluation for the decrypted binary data is analyzed. One of errors is a quantization error in detecting the hologram intensity on CCD, and the other is generated from decrypting the data with the incorrect key. The technique using 2-step phase-shifting holography is more efficient than a 4-step method because 2-step phase-shifting holography system uses less data than the 4-step method for data storage or transmission. The simulation shows that the proposed technique gives good results for the optical encryption of binary information.