Optical Image Encryption Technology Based On Coherent Diffraction

With the continuous development of various emerging technologies,such as artificial intelligence,big data and data interaction,the security of data transmission and storage is also facing more and more severe challenges in an era of interconnection of all things.To ensure the security of data and information has become a key topic related to national security and economic development.As a traditional technology,digital information encryption technology has slow information processing speed,small capacity,and insufficient security,which can no longer meet the needs of this big data era.However,the development of optical information security technology has unique advantages in solving the above problems.The optical information processing mode is different from the serial operation mode of electronic devices.Optical devices can process each pixel on the image simultaneously,which is a parallel working mode.In addition,the wavelength of light waves is very short,and the frequency is very high accordingly.Multiple signals can be loaded onto one carrier at the same time for processing,so the information capacity of optical information processing can be very large.In optical information processing,the information can also be encoded by modulating the phase,amplitude,wavelength and polarization sate of the carrier signal and other parameters,which has a large key space.This thesis focuses on the study of the application of non-mechanical ptychography encoding in optical information security.A non-mechanical ptychography encoding technique is proposed firstly,and then two types of information security systems are designed and realized based on non-mechanical ptychography encoding.The first is an optical encryption system combined non-mechanical ptychography encoding with Visual Cryptography.Optical experiments is used to verify the effectiveness and feasibility.The result shows that the designed system has high security and imperceptibility.In order to further expand the application range of non-mechanical ptychography encoding,combined non-mechanical ptychography encoding with Extended Visual Cryptography is designed secondly.In this encryption system,the plaintext information is generated into multiple shared through the Extended Visual Cryptography,and then the information is loaded into the diffractive optical path through the spatial light modulator for block diffraction.The key space of the system is greatly expanded by using various diffractive parameters in the diffractive optical path,which improves the security.In this decryption system,only the phase recovery algorithm is needed to obtain the shared pattern,and the plaintext information is obtained after the pattern is stacked.This method uses technology cascading to achieve complementary advantages and achieve the goal of fast information processing,large information capacity and high security.