In-line Fraunhofer holographic system for measuring particle distribution of fast-moving particles

An in-line Fraunhofer holographic system which can measure the size distribution and the mass of particles ejected from a target surface at speeds up to 5.0 km/s is described. Observed particle diameters range from 4μm to several hudnreds μm, and teh depth of field is 10mm to 15mm. In order to avoid damage of the hologram, an optical relay system is used to relay the interference pattern 90cm. After the hologram has been made a spatially filtered laser is used to reconstruct a real image of particles over a 3D volume. Then the real particle images from the 3D volume are digitized via a CCD camera with 1280×1024 pixels. We have used this system to measure static or slow moving particle field, the experimental results show that the system's performance are very good.