Automatic focusing method based on area criterion

Abstract

The invention discloses an automatic focusing method based on an area criterion. The automatic focusing method comprises the following steps: (1) acquiring a holographic image of multi-focal-length plankton; (2) conducting image segmentation on the hologram, and extracting a sub-hologram of each plankton; and (3) sequentially applying an automatic focusing method based on the area criterion to the sub-holograms to obtain the focal length of each plankton. According to the principle that the focusing image is smaller than a fuzzy image in area, the accuracy of detection of the focal length of the plankton is effectively improved, the calculation is simple, and the practicability is high.

Description

technical field [0001] The invention relates to the field of digital holographic microscopic imaging of plankton with multiple focal lengths, in particular to an automatic focusing method based on an area criterion. Background technique [0002] Digital Holographic Microscopy (DHM) imaging technology can record the light wave field information of the entire monitoring area in a planar hologram, and reconstruct the images of plankton at different depths in the monitoring area through numerical reconstruction algorithms, but only When the reconstruction distance is equal to the depth (focal length) of the plankton, the plankton can become a clear image in the reconstructed image, otherwise it will become a blurred image. In order to find the focal length of the plankton in the hologram, researchers have proposed many automatic focusing methods, most of which are based on the sharpness criterion of the image, including two aspects: one is that the clear image has a larger gradi...

AI Technical Summary

Problems solved by technology

[0003] These autofocus methods described above achieve good results in conventional optical microscope images or holograms with only one target, but cannot be accurately found in multi-focal plankton holograms, or even the individual plankton's focal length

The main reasons are as follows: 1. In the traditional optical microscope image, as the objective lens rises and falls, the whole image becomes clear or blurred at the same time, and it is easy to get an extreme point when using the automatic focusing method

However, in the hologram of multi-focal plankton, as the reconstruction distance changes, some plankton become clear, and some plankton become blurred. In this way, the contribution of the clear plankton to the calculation results is changed 2. There is coherent noise in the hologram, which carries a large number of high-frequency components, which will greatly interfere with the calculation results; 3. The plankton The size is mostly between tens of microns and hundreds of microns, which is relatively small compared to the size of the entire hologram, and has a weak influence on the calculation results

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