Position multiplexing multiple-image encryption using cascaded phase-only masks in Fresnel transform domain

A position multiplexing method based on the modified Gerchberg–Saxton algorithm (MGSA) and a cascaded phase modulation scheme in the Fresnel transform domain is proposed in the multiple-image-encryption framework. First of all, each plain image is encoded into a complex function using the MGSA. The phase components of the created complex functions are then multiplexed with different position parameters, and summed. The phase part of the summation result is recorded in the first phase-only mask (POM). The MGSA is applied on the amplitude part of the summation result to determine another phase only function which is then recorded in the second POM. The simulation results show that the crosstalk between multiplexed images is significantly reduced compared with an existing similar method [20]. Therefore, the multiplexing capacity in encrypting multiple grayscale images can be increased accordingly.