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Automatic focus determination through cosine and modified cosine score in digital holography

机译：通过数字全息术中的余弦和修正的余弦得分自动确定焦点

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摘要

An automatic focus determination method in digital holography that utilizes the cosine score (CS) of the inner angle between the vectors that result from adjacent axial reconstructed amplitude images is proposed. This method is based on the fact that the optical field near the focus plane contains more regular features of an object than the defocused region. Further, a modified CS (MCS) autofocusing method is proposed to extend the application range and improve the performance of the proposed method. First, a low-pass filter is designed for the object term holograms in the frequency domain. Second, the standardized Z-scores method is applied along the axis to the amplitude images reconstructed from the filtered hologram. Finally, the MCS of the standardized amplitude images is calculated by an improved cosine-like formula. Next, the focus plane is found at the mini-mum MCS for different types of objects. This method enables accurate focus determination for all types of objects, as well as for the image region with a slow change or small size, which offers time savings and the precise autofocusing of objects with large longitudinal volumes. The simulations and experimental results on a United States Air Force resolution chart and living cells are presented, illustrating the efficiency and potential of the methods.
机译：提出了一种数字全息自动聚焦确定方法，该方法利用了相邻轴向重建幅度图像产生的矢量之间的内角的余弦值（CS）。该方法基于以下事实：聚焦平面附近的光场比散焦区域包含更多的物体规则特征。此外，提出了一种改进的CS（MCS）自动聚焦方法，以扩展应用范围并改善该方法的性能。首先，为频域中的目标项全息图设计一个低通滤波器。第二，将标准化Z分数方法沿轴应用于从滤波后的全息图重建的振幅图像。最后，通过改进的余弦式公式来计算标准化振幅图像的MCS。接下来，在最小MCS处找到用于不同类型对象的聚焦平面。这种方法可以对所有类型的对象以及变化缓慢或尺寸较小的图像区域进行准确的焦点确定，从而节省了时间并可以对具有较大纵向体积的对象进行精确的自动聚焦。展示了美国空军分辨率图和活细胞上的仿真和实验结果，说明了该方法的效率和潜力。

著录项

  • 来源
    《Optical engineering》 |2017年第3期|034103.1-034103.8|共8页
  • 作者

    Aga He; Wen Xiao; Feng Pan;

  • 作者单位

    Beihang University, School of Instrumentation Science and Optoelectronics Engineering, Beijing, China;

    Beihang University, School of Instrumentation Science and Optoelectronics Engineering, Beijing, China;

    Beihang University, School of Instrumentation Science and Optoelectronics Engineering, Beijing, China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    autofocusing; digital holography; cosine score; modified cosine score;

    机译：自动对焦数字全息术余弦分数修正余弦分数;

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