For understanding such dispersed two-pjase flow as spray and bubbly flow, not only the size and velocity distribution of particles but those simultaneous properties of individual particles are required to understand the unsteady behavior of flow fields. The improved interferometric imaging technique has been developed by the authors that can measure the planar or even volumetric distribution of diameter and velocity vector of particles instantaneously. The accurate diameter determination by the optical compression and subpixel frequency estimation by a Gaussian interpolation technique enables the accurate determination of the droplet correspondence between two successive images and consequently the velocity vectors of each droplet can be measured even from the image of denser spray. The results showed the significant difference of particle behavior depending on the group of diameters in the unsteady flow.