A double images hiding technique based on optics interference is proposed. The images are encoded into two pure phase masks via numerical calculation. Two coherent parallel light beams propagate through the masks and interference at preset positions, the decoded images will appear at preset positions. The position coordinates and wavelength can also be used as encoding parameters. Computer simulation is carried out to verify the algorithm.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.