计算全息和光学图像的随机相位加密技术研究

【作者】 郭建涛；

【导师】 胡家升；

【作者基本信息】 大连理工大学 ， 信号与信息处理， 2004， 硕士

【摘要】 随着社会的发展，信息量的爆炸式增长和因特网进入人们的日常生活已经成为时代的标志。本论文研究目的在于将传统电子设备的灵活性和光学的快速并行计算结合起来，实现光学图像加密和图像识别，实现高效的信息安全保护。 基于加密过程中相位函数的随机性，首先研究用计算机制全息图的方法。主要包括傅立叶变换全息图和相息图，指出不论在衍射效率还是成像质量，相息图都比傅立叶变换全息图更适宜用于随机相位加密。 论文将光学加密方法分为两类进行研究，一种是基于联合变换相关器的加密方法。它虽然具有平移不变的系统特性，但振幅型滤波器降低了系统的衍射效率；第二种是基于匹配滤波相关器的加密方法。这种方法在基于投影限制集算法的基础上，利用纯相位函数，改善了系统的衍射效率，但同时带来了对系统光学元件对准的严格要求。为了提高光学元件的衍射效率和系统的实际可操作性，在比较两类加密方法的基础上，实现了在联合变换相关器上的纯相位加密方法。论文同时给出了计算机仿真和光学试验结果，证明这种方法的正确性和可行性。 最后为了在因特网中传输保护信息，提出用加密隐藏的方法进行信息传输。用纯相位的加密函数和密钥函数一起能够很好地重建原始信息；但是由于加密结果容易引起攻击者注意，所以将其隐藏在一幅非安全性的图像中进行传输，仿真结果证明该方法可以隐藏的信息量大、恢复效果好，具有很强的鲁棒性。更多还原

【Abstract】 With the social development, the information increasing and the entrance of Internet to the people’s life have already become the time sign. In this thesis, the research aims to combine the flexibleness of electrical equipment with the fast parallel optical computing, so that it can realize optical image encryption and recognition and high efficiency of information security protection.Some research works in the execution methods of hologram have been done firstly based on the randomicity of phase function used for encryption. It includes Fourier transform hologram and kinoform mostly. The research indicates that kinoform is more suitable for random phase encryption than the other hologram either the diffraction efficiency or the equality of reconstruction image.The thesis categorizes the encryption methods as two sorts. The first is based on the joint transform system .The expected advantage from this security system is the shift invariance, but the disadvantage is that the amplitude characteristic of filter restricts system’s diffractive efficiency. The second is based Vander lugt correlator. This method improves the diffractive efficiency of system because of optical phase-only elements, which produce from project onto constraints algorithm, but at the same time it has the problem of misalignment sensitivity of the filter mask in the VLC system. To obtain high diffractive efficiency and the convenient manipulation in practice simultaneously, the phase-only decryption in the JTC has been adopted based on the above methods’ compare. The validity and feasibility of this method is proved though computer simulation and optical experiment result.Finally, the way of information hiding is used in order to transmit the protected image though Internet. Using encrypted and key functions, the original information can be reconstructed very well. But the encryption result may arouse the attackers’ notice, so it can be hided in a common image. The simulation illustrates the system ability to recover the hidden image under distortions and the robustness of the hidden image against removal trails. The information capacity which system can be hided is also enormous.更多还原