Patent ID: 6850324

Claim:
A device for measuring the sizes of substantially spherical particles comprising: a light source supplying a light beam for illuminating the particles, which then diffract the light beam; optical means for splitting the diffracted light beam into a plurality of concentric annular areas; optical means for concentrating the diffracted light beam, which respectively correspond to said plurality of concentric annular areas, into a plurality of points different from each other; and photodetection means for detecting the light intensities respectively corresponding to these points, the particle sizes being determined on the basis of these light intensities, wherein the optical means for concentrating comprise a focusing optical means having a plane input face and an aspherical output face, and wherein the optical means for splitting comprise a plurality of annular portions of deviating optical means, these annular portions intercepting the concentrated light, and deflecting the light intercepted along their respective directions which are different from each other.