Counting and Classifying Small Objects by Far-Field Light Scattering

An approach to small particle counting and classification is proposed in which the size and shape distribution is determined from the far-field pattern of light scattered by the particles. By presuming that the scattering function for each particle species is known from auxiliary experiments or calculations, a general result applicable to irregular particles as well as simply shaped particles is obtained. Inversion formulas, by which the particle distribution is determined from the far-field data, are presented in forms suitable for digital or optical processing. An experimental approach to the design of a real-time optical counting and classifying instrument is suggested.