Global rainbow thermometry for droplet-temperature measurement

Standard rainbow thermometry connects the scattering angle of the main rain bow maximum, generated by a single droplet, to the droplet's refractive ind ex and thus to its temperature. Droplet nonsphericity influences the rainbo w position and therefore degrades the quality of the droplet-temperature me asurement. We propose global rainbow thermometry, which measures the averag e rainbow position that is created by multiple droplets and from which a me an temperature can be derived. The new technique aims at eliminating the no nsphericity effect. The principle of this method is presented, and a typica l recorded image is discussed. (C) 1999 Optical Society of America.