Application of in-line digital holography to particle counting in 3D space

In this study, a technique of in-line digital holography was applied to particle counting in 3D space. In order to detect very small particles, holograms were captured by the CCD with a zoom lens. Then, we found that the distance used in the hologram reconstruction is measured from the focal plane, and that depth of field is limited depending on the magnification. This technique is expected to be applied to micro-bubble measurements.