Random phase images generated by affine transformations as optical coding masks

FABIAN MOSSO; MYRIAN TEBALDI; ROBERTO TORROBA; NESTOR BOLOGNINI

Sidney (Australia)

Congreso; 20th Congress of the International Commission for Optic; 2008

International Comission of Optics

In this contribution we present algorithms to generate a pseudo-random pattern of an input image through an affine transformation. The basic parameters affine transformation (AT) uses are: scaling, rotation and translation. In this proposal, we also include shearing procedures. The advantages and disadvantages of using these new parameters are discussed. The properties of the random patterns obtained by using affine transformation are not still well established. We center our interest that the affine transformation parameters have on the random properties observed in the final transformed image. The number of iteration needed to reach a random code was studied. This study shows that iterative processes leads rather quickly to uniform output images. Potential uses in optical security schemes are explored. In this context, we show applications on optical coding and decoding by using these AT images as a set of random phase masks.  This procedure offers the advantage over the conventional random phase image encryption that we do not need to send the encrypting mask to the authorizer user, but an original open image and the set of affine transformation parameters that lead to the construction of the encrypting mask. Therefore we are increasing the security against eavesdroppers.