Optical Data Storage by Use of Optical Encryption and its Compression and Transmission

提出了利用光加密及其压缩传输技术进行光数据存储的方法。(1)利用光折变材料，提出了一种基于联合变换相关器结构的安全光存储器。介绍了一种利用优化算法设计的密钥代码，使其傅立叶变换具有均匀的振幅分布和均匀的随机相位分布。原始二维数据和密钥代码并排放置在输入平面上。它们都以联合功率谱的形式存储在光折变材料中。原始数据的检索可以用相同的键代码实现。通过角复用和键码复用，可以在同一晶体中记录多个二维数据。(2)提出了一种基于物体波相位调制的三维物体加密方法。利用数字全息技术，通过虚拟光学随机相位掩模调制目标波的相位。加密步骤的密钥既是相位分布，也是虚拟光相位掩码的位置。如果其中任何一个不正确，我们都无法解密3D对象。由于全息图的特性，我们可以看到重建的三维物体有一定的视差。实验结果证实了该方法的有效性。(3)提出了一种基于数据压缩的加密数字全息数据重建方法。我们证明了可以减少数字全息图的量化级数。通过计算机仿真，证实了该方法对二值图像特别有用。对于灰度图像，我们提出了位平面分解方法。结果表明，该方法可以获得高质量的重构图像质量和高压缩比。

We proposed optical data storage by use of optical encryption and its compression and transmission.(1)A secure optical storage based on a configuration of a joint transform correlator by use of a photorefractive material has been presented. A key code designed through the use of an optimized algorithm so that its Fourier transform has a uniform amplitude distribution and a uniformly random phase distribution has been introduced. Original two-dimensional data and the key code are placed side-by-side at the input plane. Both of them are stored in a photorefractive material as a joint power spectrum. The retrieval of the original data can be achieved with the same key code. We can record multiple two-dimensional data in the same crystal by angular multiplexing and or key code multiplexing.(2)An encryption method of a 3D object based on phase modulation of an object wave has been proposed. The phase of the object wave is modulated by a virtual optical random phase mask using a digital holographic technique. The keys of an encryption step are both a phase distribution and a position of the virtual optical phase mask. If either of them is not correct, we can not decrypt the 3D object. Owing to a characteristic of a hologram, we can see some parallax of a reconstructed 3D object. Experimental results have been presented to confirm the proposed method.(3)An encrypted digital holographic data reconstruction method with data compression has been proposed. We show the number of quantization levels of the digital hologram can be reduced. By computer simulations, it is confirmed that the method is especially useful for binary images. For gray-scale images, we propose a bit plane decomposition method. By this method, we have shown both high quality reconstructed image quality and a high compression ratio can be achieved.