Fast autofocusing in digital holography using scaled holograms
Fast autofocusing in digital holography using scaled holograms
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DOI：
10.1016/j.optcom.2012.09.036
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发表时间：
2013-01
影响因子：
2.4
通讯作者：
Hazar A. İlhan;Mert Doğar;Meriç Özcan
中科院分区：
文献类型：
--
作者：
Hazar A. İlhan;Mert Doğar;Meriç Özcan
数字记录的全息图被数字重建以揭示物体的3D轮廓。当物体到记录平面的距离未知时，必须按离散的步长进行重建，并根据一定的准则确定最佳焦距。有一些自动对焦算法利用度量来评估图像的质量，例如对象的清晰度，以确定最佳对焦距离。然而，这种搜索的计算成本随着系统的分辨率变得更高而迅速增加，因为对象图像必须首先从全息图进行数值重建。在这里，我们研究了从缩放全息图获得的物体图像的清晰度曲线的行为。我们发现，使用这种定标可以准确地估计自聚焦距离，并且由此产生的自动对焦速度改善在定标比的平方量级。给出了实验结果，并与仿真结果进行了比较，吻合较好。
Digitally-recorded holograms are numerically reconstructed to reveal the 3D profile of the object. When the distance of the object to the recording plane is not known a priori, one has to perform reconstruction at discrete steps and decide the best focus distance according to some criteria. There are autofocusing algorithms that utilize a metric to assess the quality of the images, such as the sharpness of the object, to decide the best focus distance. However, the computational cost of this search rapidly increases as the resolution of the system becomes higher since the object image has to be numerically reconstructed from the hologram first. Here, we investigate the behavior of the sharpness curves of the object images obtained from the scaled holograms. We find that it is possible to estimate the autofocus distance accurately with this scaling, and the resultant autofocus speed improvement is on the order of square of the scaling ratio. Experimental results are presented and they are in excellent agreement with the simulations.