An Optical Encryption System Which Can Realize The Conversion Of A Color Image To A Gray Image

Nowadays,with the development of global network,information system is playing an important role in people's lives and work.However,there is a problem of network and information security.When people's information is illegally copied and spread,people will suffer huge losses.Therefore,the research of information security system has been widely paid attention to.Compared with traditional electronic image processing technology,optical image processing has many advantages,so it has become one of the most popular research fields in the international community.In this paper,based on Fresnel diffraction and phase iterative algorithms,a new image encryption system is proposed.We discuss its security,and further improve the system of optical image encryption technology.Firstly,this paper introduces the basic theory of optical image encryption,mainly introduces the theory of diffraction based Fresnel diffraction,and the definition,implementation method and related properties of Fourier transform,and the basic principle of phase retrieval algorithm,etc.Second,we introduce several typical optical image encryption techniques,including the double random phase encoding technique,based on phase retrieval algorithm encoding system and tricolor theory color image encryption system,etc.These techniques can be realized by the optical method and the numerical method,which bring many conveniences to the people's research in the future.Then,we propose an improved encryption system based on the phase retrieval algorithm.The encryption system is an optical image encryption system based on Fresnel diffraction and phase iterative algorithm,which can realize the conversion between different images.The ciphertext is placed at the input plane with the first phase mask by iteration,and the second random phase mask is placed in the transform plane.The information of the image can be obtained at the output plane by using the Fresnel diffraction.Finally,we put forward a new color image encryption system based on phase iterative algorithm in Fresnel domain,this system based on tricolor principle,Fresnel diffraction,and phase iterative algorithms.The difference from the previous encryption system is that the ciphertext of the system is a color image,and plaintext is a gray image,which can achieve the conversion of a color image to another gray image.In order to recover the gray image from the color image,the three channels must be placed in some phase masks,and then the gray image can be obtained by using the Fresnel diffraction and the principle of incoherent superposition at output plane.