Image Polarization Encryption And Image Polarization Multiplexing Algorithm Research

In the period of rapid development of computer networks and modern communication technologies,digital information such as images,texts,audio,and video can be easily transmitted and downloaded on the network,and the secure transmission and storage of information is particularly important.As one of the important information storage methods in digital information,image has gradually become one of the mainstream of people's information exchange because of its vivid image.However,while bringing convenience to people,how to achieve secure storage and transmission of images is always a hot issue.The research focus of this thesis is to study the polarization encryption of images and the polarization multiplexing of images by using the polarization characteristics of the light field.The purpose is to expand the encryption channel of images and enhance the encryption effect of images.The thesis uses Jones vector and Stokes vector to describe the polarization characteristics of the light field.According to the principle that the polarization state of the light wave changes after the polarizing element passes,a Stokes vector-based encryption algorithm is designed.The algorithm loads the image to be encrypted and the random image on a Spatial Light Modulator(SLM),polarizes the polarization through the polarizer and the Q-plate,and superimposes the two beams with a beam splitter.The polarizer is used to screen the polarization state of the superimposed beam.The intensity map recorded by CCD is the final ciphertext,and the simulation results verify the effectiveness of the algorithm.In this thesis,a two-image asymmetric polarization encryption algorithm based on Q-plate is designed.The two original image information is decomposed into two pure phase plates by the principle of interference decomposition.The two pure phase plates are loaded into the optical path through SLM..The polarization state is modulated by Q-plate,and its polarization state is screened by a pixelated polarizer.The light intensity information recorded by CCD is the ciphertext we need.In the whole process of polarization encryption algorithm,the decryption key is different from the encryption key,which realizes asymmetric polarization encryption and improves the security of the algorithm.The simulation results show that the algorithm is sensitive to the key,and the ciphertext has good anti-shear attack and anti-noise attack ability.In this thesis,an image polarization multiplexing algorithm is proposed by using polarizing devices for different transmittances of light waves in different polarization directions.The images of multiple polarization states are superimposed and separated to recover the original image.The experimental optical path of vector light generation based on 4f system is constructed.The image is converted into complex amplitude information by polarization coding and the generated hologram is loaded on the SLM.Two quarter-wave plates are used to generate two orthogonal base vectors.Light,using a Ronchi grating to achieve collinear superposition,resulting in a vector light field,rotating the polarizer to detect a polarization-multiplexed image.Through the decomposition and resynthesis of the beam,the polarization multiplexing of multiple images was carried out,and the numerical simulation and optical experiments were completed.The effectiveness of the proposed algorithm was verified.