An optoelectronic imaging system for particle characterization in gas turbines is described. This system includes two CCD cameras viewing the same object field. One of these cameras is double exposed and the second is only open during the second pulse. An analogical subtraction between the output signals of these cameras gives the sign of the transverse velocity vector. Out of focus images are deconvolved by assuming a Gaussian point spread function (PSF) whose spatial parameter sigma increases with the defocusing distance z. The sign ambiguity on z is removed by comparing the power spectrum of the two different defocused images. The amount of defocusing is deduced from the intensity distribution slopes. The measurement accuracy of the size d is better than 10 % for d greater than or equal to 10 mu m through a sample volume with a depth of 4 mm.