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In terms of climate science, getting the accurate cloud particle sizes, shape and number distributions is necessary for searching the influence of cloud on the environment, radiative transfer, remote sensing measurements and understanding precipitation formation. Many methods and instruments have been developed to measure cloud particles, yet there is still restricted to one-dimensional or two-dimensional projections of particle positions, unable to get the three-dimensional information of the spatial distribution of particles. In-line holography is particularly useful for particles field measurements, because it can directly get the three-dimensional information of the particles and quickly access and storage holographic image. In this paper, the main work is using digital in-line holographic system to measure simulated cloud particles in the laboratory. For digital recording hologram reconstructing, we consider the image intensity in conjunction with the edge sharpness of the particles, to obtain an automatically selected threshold of each particle. Using the threshold, we can get a binary image to identify the particles and separate the particles from background, and then get the information such as the location, shape, particle size of particles. The experimental results show that the in-line digital holography can be used to detect the cloud particles, which can gain many parameters of the simulated cloud particles in the plane perpendicular to the optical axis, and can estimate volume parameters of the simulated cloud particles. This experiment is a basis for the further in situ detection of atmospheric cloud particles.
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