数字全息在实时动态测量和信息隐藏中的应用研究

【作者】 朱竹青；

【导师】 聂守平；

【作者基本信息】 南京师范大学 ， 物理电子学， 2013， 博士

【摘要】 数字全息术是利用光电传感器件(如CCD或CMOS)代替干板记录全息图,然后将全息图存入计算机,用计算机模拟光学衍射过程来实现被记录物体的全息再现和处理。它具有制作成本低,成像速度快,记录和再现灵活、全息图易于网络传输等优点,一直成为研究人员关注的热点。数字全息术现已被广泛地应用于物体显微观测、微小形变测量、粒子束监测、目标识别和信息隐藏等应用领域。但数字全息术在提高再现像质量、加速数字全息图再现运算、物体动态变化实时测量、数字全息实时再现显示以及大容量数字全息隐藏等关键问题仍然值得深入的研究。本论文主要围绕如何利用数字全息实现物体动态变化过程实时记录与再现和大容量数字全息的生成与信息隐藏展开讨论和研究的,主要创新点包括以下几个方面：1.针对现有的相移数字全息术,提出了一种基于圆偏振光干涉的相移数字全息术的新方法。该方法利用左旋与右旋偏振光分别作为物光和参考光,经偏振片后相互干涉形成数字全息图,而相移由偏振片旋转角度决定。通过理论推导和数值模拟,研究了提高偏振相移数字全息再现质量的实验优化参数条件。实验结果同时表明在优化参数条件下,该技术能有效去除再现图中零级分量和共轭分量,再现质量好。2.针对利用相位阵列实现瞬时相移数字全息术的方法,提出了基于偏振方向空间周期性瞬时四步相移数字全息实验方案,该方法不需要相移阵列与成像器件CCD间像素对应,大大降低了实际实验的操作难度。通过插值运算,研究了瞬时相移复合数字全息图再现算法,数值模拟所获得的实验结果具有传统相移数字全息图再现特点,并通过光学实验所获得的相移全息图处理与运算验证了该瞬时相移数字全息术方案的可行性,这将会为诸如细胞诊断、等离子分析等动态过程实时探测提供了一种全新的记录手段和可行方案。3.针对CPU并行运算的不足,开发出一种利用MATLAB语言编写、GPU加速数字全息图再现的软件,大大缩短了数字全息图再现运算时间,提高了全息图后期处理的效率。针对物体动态过程的实时表征,基于.Net平台,利用C#编程语言开发出集CCD所记录的全息图实时采集、GPU加速全息图再现运算和再现结果实时显示诸功能于一体的数字全息实时测量软件,解决了以往动态过程后期表征的缺点。利用该软件,实验研究了转速1Rpm三维物体的动态变化过程,实时显示帧速达21fps,验证了该软件的可靠性和实用性,这将会为诸如细胞诊断、等离子分析等动态过程实时表征提供了软件保障和技术支持。4.针对复值图像的空域信息隐藏,提出了一种基于离散余弦变换的复值图像信息隐藏方案。比较多种嵌入系数下宿主图像不可见性和提取出的隐藏图像质量,得出该信息隐藏方式下优化嵌入系数。多种攻击方式下的实验结果表明该方法比空域像素直接相加隐藏更具有抗攻击效果好,再现质量高的优点。利用该信息隐藏方法,研究了三维物体相移数字全息图的信息隐藏和攻击实验,结果表明：相对于二维图像的信息隐藏,数字全息的信息隐藏使得宿主图像更具不可察性,隐藏信息更具有安全性和鲁棒性。5.从大容量信息隐藏需求出发,提出了基于偏振复用和波长复用两种大容量数字全息生成方案。针对实验所获得偏振复用数字全息图与模拟所得的偏振复用相移数字全息图信息隐藏及攻击实验比较发现,隐藏相移数字全息图的系统抗攻击能力强,再现像质量高。研究了含有三幅图像信息的波长复用相移数字全息生成原理、再现方法和信息隐藏,攻击实验结果表明隐藏该波长复用数字全息图,系统鲁棒性能高,隐藏信息容量大,同时所需要的宿主图像冗余信息空间与单幅图像一样,从而巧妙地解决了在有限的载体信息中隐藏尽可能多的秘密信息的要求。更多还原

【Abstract】 Digital holography acquires the digital hologram with CCD which is stored and numerically reconstructed by computer. Attracted more attentions by reseachers worldwide, Digital holography has many advantages such as low cost, fast capture speed, flexible record and reconstruction method and convenient transmission which is applied in many domains such as microscopy observation, micro-disform measurement, particle flow detection, target recognition and information hiding. But several key problems such as enhancing the quality of reconstructed image, acceleration of the reconstruction calculation, real-time measurement of dynamic process of the object, real-time reconstruction view and large capacity digital hologram hiding shoule be deeply studied. From the point of how to realize the dynamic process real-time measurement of the object and large capacity information hiding by digital hologray, The main innovation points are listed in the below:1. According to existing phase-shifting digital holography methods, a new method of phase-shifting digital holography based on the interference between two circle-polarized beams is presented, where the phase changes depend on the rotated angle of polarizer. Optimized parameters are obtained for good quality of reconstructed image with theoretical analysis and numerical simulation, where optical experimental results demonstrate this technology can effectively remove the zero-order and conjugated image and acquire good-quality reconstructed image.2. One-shot four-step phase-shifting digital holography based on periodic polarization distribution instead of periodic phase array in space domain is presented where no precise alignments between phase array and CCD are needed and the experimental difficultites are greatly reduced. Reconstruction algorithms of compound hologram are studied with interpolation calulation and the same results are obtained between optical experiments and theoretical simulation. The feasibility of one-shot phase-shifting digital holography is demonstrated with experimental results which can provide the brand new measurement method and high performance detection scheme in dynamic process such as cell diagnose and plasma analysis.3. According to the deficiency of CPU in parallel computation, the accelerated calculation software based on GPU is designed with Matlab code with obvious acceleration speed and high efficiency. According to the real-time characterization of the dynamic process, the powerful real-time reconstruction view software is designed including real-time recording, accelarted calculation and real-time display three functions compiled with C#codes and.Net platform. With this tool, the dynamic process of the3D object rotated by1Rpm are studied and the display speed can get21frames per second, which can provide the software ensurement and technology support in real-time characterization of dynamic process such as cell diagnose and plasma analysis.4. According to the information hiding method of complexed image embedded in the space domain, a new complex value information hiding technology is presented with DCT and Double Random Phase Encoding and optimized embedding coefficient is obtained by comparing the invisibility of the host image and the quality of the extracted hiding image under different embedding coefficients. The attack results indicate3D object phase-shifting digital hologralm as hiding information and the information embedded in the DCT domain have better anti-attack effects and robustness.5. From the need of large capacity information hiding, two large capacity digital holography schemes are presented based on polarization-multiplexing and waveleng-multiplexing tecnologies. The attack effecs are compared in two polarization-multiplexing digital holograms with and without phase shifting. The results indicate two schemes can enlarge the hidden information capacity, skillfully solve the problem of more embedded information in limited redundant information of host image and have better anti-attack effects with phase-shifting digital hologralm as hiding information.更多还原