Abstract: A novel fully phase image encryption technique based on two-step-only quadrature phase-shiftingdigital holography and double random phase encoding in fractional Fourier transform （FRT） domain is proposed, in which only two quadrature phase holograms are required and neither reference-wave intensity nor object-wave intensity measurement is needed. A primary amplitude image is modulated to a fully phase image, and then the fully phase image is encoded into two quadrature digital holograms by using double random-phase masks （RPMS） encoding in the input and fractional Fourier domain transform planes, respectively. The clear primary image can be recovered by simple algorithm with the right keys. The feasibility and validity of this technique has been proved by simulation experiments. And the robustness against occlusion and noise attacks, as well as the effect of the reference wave intensity to image encryption and decryption, has also been investigated.

Key words: encryption, phase-shifting interferometry, digital holography, fractional Fourier transform