We implement an optical encryption system based on double-random
phase encoding of the data at the input and the Fourier planes. In
our method we decrypt the image by generating a conjugate of the
encrypted image through phase conjugation in a photorefractive
crystal. The use of phase conjugation results in
near-diffraction-limited imaging. Also, the key that is used during
encryption can also be used for decrypting the data, thereby
alleviating the need for using a conjugate of the key. The effect
of a finite space–bandwidth product of the random phase mask
on the encryption system’s performance is discussed. A theoretical
analysis is given of the sensitivity of the system to misalignment
errors of a Fourier plane random phase mask.
© 1998 Optical Society of America
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