The invention relates to securing of information utilising optical imaging technologies
and more specifically to phase encryption and decryption of images. An image is
encrypted into a mask having a plurality of mask resolution elements (Xm,
Ym) by encoding the image using e.g. a phase mask with an encoded phase
value (Xm, Ym) and an encoded amplitude value a (Xm,
Ym), and by further encrypting the mask (using e.g. a spatial light
modulator) by addition of an encrypting phase value c (Xm,
Ym) to the encoded phase value (Xm, Ym)
and by multiplication of an encrypting amplitude value ac (Xm,
Ym) with the encoded phase value a (Xm, Ym). The
method of decrypting comprises the steps of decrypting the mask by radiating electromagnetic
radiation towards the mask and inserting into the path of the electromagnetic radiation
a complex spatial electromagnetic radiation modulator comprising modulator resolution
elements, the decrypting phase value d (Xd, Yd)
and the decrypting amplitude value ad (Xd, Yd)
respectively, of a modulator resolution element (Xd, Yd)
being substantially equal to -c (Xm, Ym)
and ac-1 (Xm, Ym).
