数字全息自动聚焦及像质增强技术研究

发布时间：2018-06-15 19:07

本文选题：大物成像 + 自动聚焦　；参考：《南京邮电大学》2016年硕士论文

【摘要】：本文旨在进行数字全息关键技术研究。利用理论推导和实验探究相结合的方法,通过对国内外数字全息技术领域进行深入调研与分析,本文对数字全息的三个关键技术进行了研究:(1)为了简化无透镜大物体傅里叶变换数字全息实验光路设置,本文深入研究了一种无透镜大物体合成孔径数字全息成像方法,该方法通过改进马赫-曾德尔干涉仪,将原始参考光分成两束,其中一束进行重定向,作为第二束物光,两束物光照在大物体不同部位,与参考光干涉在CCD上成像后,利用合成孔径技术,实现了一次曝光大物体数字全息成像;(2)在数字全息自动聚焦重建中,为了降低重建过程中重建像均值漂移对部分自动聚焦判据函数的影响,本文提出了一种新型强适应性自动聚焦判据函数,即基于高频分量的标准差对比度法,该方法仅利用原始全息图高频能量计算判据,减小了以往方法中存在的均值漂移问题,且更简单、高效,在不同像质的数字全息图重建过程中,表现出强适应性;(3)在数字全息重建过程中,重建像会因为散斑噪声而使得像质降低,为了提高数字全息重建像像质,本文提出了一种有效的像质增强算法,即大物体低像质数字全息重建像在衍射极限下的频率外延增强算法,该算法将原始全息图+1级傅里叶滤波光谱重建像进行自适应高斯滤波后,降低散斑噪声,作为原始光谱,对其通过连续梯度迭代分析,得到预测光谱,最后将预测光谱对原始光谱进行校正,恢复出重建像的高频信息。
[Abstract]:The purpose of this paper is to study the key techniques of digital holography. By using the method of combining theoretical derivation and experimental inquiry, through the in-depth investigation and analysis of the domestic and foreign digital holographic technology field, In this paper, three key techniques of digital holography are studied. (1) in order to simplify the arrangement of optical path of lensless large object Fourier transform digital holography experiment, a lensless large object synthetic aperture digital holographic imaging method is studied in this paper. By improving the Mach Zehnder interferometer, the original reference light is divided into two beams, one of which is redirected as the second beam of object light, and the two beams of object light are illuminated in different parts of the large object, and the light is interfered with the reference light on the CCD. In order to reduce the influence of the mean shift of reconstruction image on partial autofocus criterion function in digital holographic autofocus reconstruction, a large object digital holographic imaging with a single exposure is realized by using synthetic aperture technology. In this paper, a new strong adaptive autofocus criterion function, standard deviation contrast method based on high frequency components, is proposed. This method only uses the criterion of calculating the high frequency energy of the original hologram, and reduces the mean drift problem existing in the previous methods. In the process of digital holographic reconstruction, the reconstructed image will be reduced because of speckle noise. In order to improve the image quality of digital hologram reconstruction, In this paper, an effective image enhancement algorithm is proposed, that is, the frequency epitaxy enhancement algorithm for large objects with low image quality digital holographic reconstruction under the diffraction limit. In this algorithm, the speckle noise is reduced by adaptive Gao Si filtering after the spectral reconstruction of the original hologram is reconstructed by Fourier filter, and the predicted spectrum is obtained by continuous gradient iterative analysis, and the speckle noise is reduced as the original spectrum. At last, the original spectrum is corrected by the predicted spectrum, and the high frequency information of the reconstructed image is restored.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O438.1;TN26

【相似文献】