Research On Optical Encryption Technology Based On Spiral Phase Encoding

With the rapid development of modern technology,the acquisition and processing of data and information has become easier,which means that the security of information is facing greater challenges than ever.Therefore,information encryption schemes to prevent information leakage have also been greatly developed.Among them,optical information security technology has attracted the attention of many researchers in the field of information security because of its advantages in processing large amounts of data at the same time and designing large-capacity space keys.Therefore,the optical image encryption technology has developed rapidly in recent decades and has occupied an important position in the field of information security.This article first introduces the background and significance of optical image encryption research,as well as the development status of several common optical image encryption directions.Then we introduced some basic knowledge commonly used in the field of optical encryption and several classic optical encryption schemes.Finally,two innovative optical encryption schemes are proposed.The first encryption scheme proposed in this paper is an optical encryption system based on unequal modulus decomposition and polarization vortex optical holography.It uses the principle of unequal modulus decomposition and polarization vortex holography to realize encoding and decoding.Firstly,the original image is decomposed into two complex amplitude images by unequal modulus decomposition method,then their polarization states are changed by vortex beams irradiation,and finally they are encrypted in the photorefractive crystals by polarization multiplexing holographic technology.In decryption,the image can be reconstructed successfully when a series of correct keys are provided.The second solution is an optical image encryption technology based on spiral structured phase coherent superposition and vector beam generation system.Firstly,the original image is encoded into two phase plates by using the spiral structured plate and the principle of coherent superposition.Then these two phase plates are brought into the vector beam generation system and Stokes parameters of vector beam are recorded on the output surface to complete the image encryption.The original image can be recovered with the correct keys when decrypted.The system has good key sensitivity and resistance to occlusion attack.And The simulation results verify the correctness and effectiveness of the method.The first optical encryption scheme uses the phase shift characteristics of the spiral phase plate to encrypt the image,while the second encryption scheme combines the spiral structured phase plate and the vector beam generation system to complete the image encryption process.They have a certain degree of novelty,and the decryption process requires the correct keys to be restored.