Optimal focal plane analysis research using noise caused by depth of field of objective lens in digital holographic microscopy (DHM)

In digital holographic microscopy (DHM) technol-ogy, we have to record a magnified laser beam that has passed through an objective lens onto an image sensor. In this process, when the specimen is not positioned on the accurate focal plane of the objective lens, a noise called a phase error occurs. This phase error becomes a factor that prevents accurate analysis by the observer. In addition, as the magnification of the objective lens increases, the depth of field becomes narrow, making it difficult to find an accurate focal plane. To solve this problem, we propose a method to find the optimal focal plane using the noise map generated by the recorded holographic video. In this paper, we verify the effectiveness of the proposed method by comparing the optimal 3D profile in the focal plane found by the proposed method and the 3D profile in a different position with the ideal comparison target, respectively.