Effect of Particle Shape on the Response of Single Particle Optical Counters

Abstract

An optical aerosol particle counter measures the size and number concentration of airborne particles in a limited size range by means of light scattering on single particles. The amount of light which an individual particle scatters is a function of its size, refractive index and shape. Particle sizing based on this principle is known since more than 35 years. Meanwhile the subject has been steadily developed and since about 25 years optical particle counters using white light illumination are commercially available. After the invention of the laser principle successful attempts have been made to replace the white light illumination by coherent and monochromatic laser light. Nowadays optical particle counters have found useful applications in basic aerosol research, particle technology, air pollution studies and clean room monitoring. Since in these fields of research particles are mainly nonspherical it is of general interest how optical particle counters respond to particles of irregular shape.