Abstract
An optical image security encryption technique based on randomized pixel positions, amplitude modulation and phase modulation for an image encryption system that is working through a spatial light modulator and nonlinear semiconductor lasers has been proposed. Chaotic injection from a master laser generator (ML), three slave lasers (SL1, SL2 and SL3) through an optical processor can produce chaotic effects on optical image signals. During the confusion process the chaotic image signal of SL1 can be used to generate horizontal flipping of the image signal to randomize pixel positions. SL2, through the optical processor, separates the image signal to columns and rows, after which it divides pixel values of even rows by odd rows and odd rows by even rows. SL3, through the optical processor, divides pixel values of an even column by odd column and odd column by even column. The output of SL3 passes through lens1 to transform the signal into frequency domain and uses four spatial light modulators (SLM1, SLM2, SLM3 and SLM4) to apply quadrant random phase modulation. It then passes resulting signal into lens2 to revert the signal in time domain and extracts it in charge-coupled device CCD image sensor. Extensive analysis of the proposed encryption system is carried out and displays good results in quality metrics in comparison to other encryption techniques. The analysis demonstrates the valuable high security and immunity to noise of the proposed image encryption technique.