Optical encryption and decryption of three dimensional objects by computer generated holograms

In this paper, a method to encrypt and decrypt three-dimensional objects using computer generated holograms is proposed. The amplitude and phase information of a three dimensional object obtained computationally using phase shifting interferometer and stored on digital computer. Encryption is performed using a random phase mask at a plane located in the Fresnel diffraction region. The decryption key is recorded as a digital hologram. Different images of the three dimensional object at different planes can be restored after the decryption. A comparison between Single and Multiple phases encoding for binary and gray scale images is performed. Bit error rate and mean square error are reported to measure the quality of the decryption process. Results show that, multiple phase encoding is more secure than single phase encoding. Also, multiple phase encoding increases the mean square error for the gray scale images.