PARTICLE IMAGE VELOCIMETRY ANALYSIS USING AN OPTICALLY ADDRESSED SPATIAL LIGHT-MODULATOR - EFFECTS OF NONLINEAR TRANSFER-FUNCTION

Optical processors for generating a two-dimensional squared autocorrel ation function have been presented for postprocessing particle image v elocimetry photographs of fluid flows. The incoherent-to-coherent conv ersion can be performed by an optically addressed spatial light modula tor. The transfer function of these devices is far from linear and wil l influence the performance of the optical processor. Two different tr ansfer functions, characterizing the two main types of commercial opti cally addressed spatial light modulators as an analog and a binary tra nsfer function, have been simulated digitally. Results of numerical si mulations on the influence of introducing these nonlinear transfer fun ctions to the correlation function for particle image velocimetry anal ysis are presented.