Patent ID: 6907124

Claim:
A method of decryption of an encrypted image having a non-encrypted image intensity pattern I(x′,y′) and encoded into a mask having a plurality of mask resolution elements (x m ,y m ) with an encoded phase value φ(x m ,y m ) and an encoded amplitude value a(x m ,y m ) and encrypted by addition of an encrypting phase value φ c (x m ,y m ) to the encoded phase values φ(x m ,y m ) and by multiplication of an encrypting amplitude value a c (x m ,y m ) with the encoded amplitude value a(x m ,y m ) each mask resolution element (x m ,y m ) modulating the phase and the amplitude of electromagnetic radiation incident upon it with the complex value a(x m ,y m )a c (x m ,y m )e iφ(xm,ym)−iφ(xm,ym) , and the method comprising the steps of radiating electromagnetic radiation towards the mask, inserting into the path of the electromagnetic radiation a complex spatial electromagnetic radiation modulator comprising modulator resolution elements (x d ,y d ), each modulator resolution element (x d ,y d ) modulating the phase and the amplitude of electromagnetic radiation incident upon it with a predetermined complex value a d (x d ,y d )e iφd(xd,yd) , the decrypting phase value φd(x d ,y d ) and the decrypting amplitude value a d (x d ,y d ), respectively, of a modulator resolution element (x d ,y d ) being substantially equal to −φ c (x m ,y m ) and a c −1 (x m ,y m ), respectively, of a corresponding mask resolution element (x m ,y m ), and imaging the mask and the electromagnetic radiation modulator onto the image having the image intensity pattern I(x′,y′).