显微数字全息相位重构的窗口选取和倾斜校正

Selection of Filter Window and Correction of Tilt Aberration in the Phase Reconstruction of Microscopic Digital Holography

对显微数字全息相位重构技术中影响重构像质量的两个因素进行了讨论。分析了用角谱法进行重构的过程中频谱滤波窗的大小与形状的选取对重构像质的影响,指出滤波窗口的选取应以刚好将原始像的二维频谱完全包括为原则;分析了在对放在载玻片与盖玻片之间的生物样品进行的实验中,重构像场倾斜的原因及相应的校正方法,并对这些分析和倾斜校正方法进行了实验验证。结果表明,要获得最佳的相位重构,应根据被测物体频谱分布的大小和形状,精确选取滤波窗。CCD探测面和样品的倾斜将导致重构相位像场的倾斜,通过图像处理可以得到一定程度的校正。

Two main determining factors, which limit the quality of the reconstructed image from the microscopic digital hologram by employing the angular spectrum method, are discussed. First are the shape and the size of the spatial filter selected. The corresponding selection principle of the spatial filter is presented, and the experimental result shows that the manual spatial filter exactly selected according to the distribution of the spectrum of the virtual image should be employed to obtain the optimal reconstructed phase image. Second is the phase tilt aberration of the reconstructed image when the specimen is put between two glasses. It is caused by the CCD plane or the sample plane being not perpendicular to the propagation axes. The correction method by the image processing is presented. The theoretical and the experimental result of an onion specimen are shown.