This study takes place within the EUFAR (European Facility for Airborne Research) project supported by the 7th Framework Program of the European Commission. In meteorology and pollution studies, measurements of the droplet sizes in the 10 to 200 m range are crucial for the understanding of precipitation formation, aerosols impact on clouds and aircraft icing. Our objective is to develop an airborne optical spectrometer sizemeter for atmospheric water droplets. This instrument will measure droplet size in the range of 20 m to 200 m. The principle of the Interferometric Laser Imaging for Droplet Sizing (ILIDS) technique is used to link interference frequency to the droplet size. One of the main objectives of this present study is to develop real time processing software that allows to give droplet information during flight. A new approach is developed that consists in the detection of all the droplet frequencies on a single frame (global approach). Thus, a Fourier analysis based on Fast Fourier Transform is developed. Then, a simulation of ILIDS phenomenon with help of Generalised Lorentz-Mie theory is done. This simulation enables software calibration: relationship between spectral intensity and droplet number or between fringe frequency and droplet size. Simulation is also used to determine the best optical configuration for the software. Simulation is also used to find limits at the software, like the droplet density (overlapping matter) or second order frequencies. Despite PDA uncertainties, it is considering as the reference. So comparisons between PDA and ILIDS apply with the software are done. 丹迪粒子動態(tài)分析儀 PDA