Abstract
To measure velocity distributions around a microbe, the three dimensional Particle Tracking Velocimetry (3D PTV) with a differential interference contrast (DIC) microscope and a single camera has been developed. In this method, the properties of out-of-focus image of a particle are used for estimation of distance from particle to focal plane. In the out-of-focus image of the particle, a ring like image is generated around the center of the particle image and the diameter of the ring like image increases with the distance from the particle to focal plane. Experimental results show that the diameter of the ring like image is proportional to the distance from a particle to the focal plane. The proposed method has been applied to measurements of three dimensional motion of particles around an Euglena in water.
