【作者】 王军；

【导师】 赵建林；

【作者基本信息】 西北工业大学 ， 光学工程， 2006， 硕士

【摘要】 在数字全息术的实用化过程中,由于现有CCD参数对记录条件的限制,降低了再现像的分辨能力。作为数字全息干涉计量术中的一个关键环节,相位去包裹一直未得到很好的解决。这些在一定程度制约了数字全息术的实际应用。本文对上述问题进行了深入研究,并提出相应的改进方法,在此基础上建立了一套较为实用的数字全息图记录与再现实验系统。其主要内容包括: (1)通过对CCD靶面的精确平移,实现了大幅面数字全息图的拼接记录。针对计算机处理能力的限制以及最大物参夹角的影响,在理论分析的基础上提出了用于大幅面数字全息图再现的分割再现合成技术。采用平面参考光波记录时,拼接后的全息图越大,所能记录的物场越大;采用球面参考光波记录时,拼接后的全息图越大,再现像的横向分辨率越高。利用精密电控平移台移动CCD分别对平面波记录和球面波记录的情况进行了详细地实验研究,结果证明了上述方法的可行性。 (2)从理论和实验两方面研究了欠采样情况下所获取的数字全息图的再现问题,分析了造成频谱混叠现象的原因。提出了利用“亚像元”成像技术重建高分辨率数字全息图的方法。实验结果表明,该方法可有效地突破最大物参角的限制,同时可以消除由于欠采样造成的频谱混叠现象。 (3)建立了一个可有效地消除包裹相位图中不连续点的模型,在此基础上进行多方向去包裹运算,然后求其平均值,从而达到与路径无关的目的。文中给出了具体算法,并通过数值模拟和实验验证了该方法的有效性和可行性。结果表明,这种方法既具有很强的抗噪声能力,又能很好地处理较大面积的欠采样区域,并且具有很强的稳定性和较高的效率。 (4)利用VC++与MATLAB混合编程技术,将本文完成的以及本实验室近年来已经完成的有关数字全息图处理的功能模块进行了集成,比较系统、完整地实现了数字全息的记录、再现以及后处理功能。系统的集成极大地方便了相关研究工作,同时利于发现问题。代码打包后软件的保密性、稳定性、独立性更强,更趋于实用化;同时也可以满足低端用户群的需要。更多还原

【Abstract】 Nowadays, the resolving power of the reconstructed image in the applications of digital holography is restricted by the finite size and resolution of the CCD. And the phase unwrapping, as an important process, hasn’t been perfectly solved in digital holographic interferometry. In this dissertation, we discussed these two problems, which restrict the applications of digital holography, and presented some improved methods. Basing on these, we developed a practical experimental system for effectively recording and reconstructing digital holograms. The main contents are as follows:(1) Some methods for recording and reconstructing digital holograms with large size are proposed. Based on breadthwise moving the CCD camera precisely, a hologram with large size can be obtained by image fusion. For the processing limitation of the computer and the influences of the critical angle between the object and reference beams, a method is proposed based on theoretical analyses, which is demonstrated to be feasible for segmenting, reconstructing, and fusing digital holograms by the experimental results.(2) After the frequency aliasing in reconstructions of under-sampled digital holograms are investigated both theoretically and experimentally, a novel method based on the sub-pixel imaging technique is proposed to reconstruct digital holograms with large size and high resolution. The experimental results show that the method can overcome the limitations of the critical angle between the object and reference beams, and omit the frequency aliasing.(3) A model to effectively eliminate local branch points without influencing normal points is established. And then, by calculating the mean values of the unwrapped phase along multiple certain directions, the goal of path independence can be achieved. Employing numerical simulations and experiments demonstrate the feasibilities and the efficiencies of the approach. It is shown that the proposed method also exhibits very strong stability and high efficiency even in presence of serious noises and relatively large under sampled areas.(4) By mixed programming between MATLAB and VC++, a practical system for recording and reconstructing digital holograms is developed by packaging the current and previous work in our laboratory. Recording, reconstructing, and pre-processing can be easily implemented by the system, which has good man-machine interface, high computational speed and better stability.更多还原