ENHANCED OBSERVATION OF NUMBER FLUCTUATIONS BY USE OF STRUCTURED LIGHT

The point statistics of light scattered from structured, incoherent il lumination of a random and fluctuating population of identical scatter ers are derived. Theoretical predictions for a two-beam illumination p attern in which the relative beam intensity is modulated are compared with computer simulations and experiments performed by illumination of a rotating mask of identical but random apertures. The use of structu red light is found to enhance the size of fluctuations, and quantitati ve comparisons between theory and practical measurement are made. The structured-light technique introduces flexibility in fluctuation measu rement, permitting optimal control of the dynamic range, and is releva nt to the development of instrumentation for particle and flow analysi s. (C) 1997 Optical Society of America.