Particle size and position measurement with digital holography

A method for particle size and position measurement based on digital holography is described. A plane wave passes a particle stream and the diffracted wave is recorded directly by a CCD-sensor without any focusing optics. The reconstruction of the particle distribution from the recorded diffraction pattern is done numerically with a computer. Diffraction patterns from different directions are taken at a fixed instant of time, evaluated independently and finally the reconstructed scenes are combined by tomographic methods.