Focusing algorithm based on droplet measurement

In-line digital hologram can realize particle detection in space of 3D coordinate. The in-line digital hologram is based on the coherent light imaging theory. When the distance of reconstruction deviate from the focus, we find the edge of the reconstructed image will appear a lot of stripes caused by diffraction. The traditional evaluation method is to focus on the image directly. It will not be able to get the correct position, and can´t get accurate particle three-dimensional of space. In this paper, it is based on the detection of laboratory cloud droplets particles to research the focus plane position of reconstructed image.