3-D measurement of moving particles by circular image shifting

A new approach to the three-dimensional (3-D) measurement of position and velocity of moving particles is introduced. A single TV camera with an apparatus to add circular shift to the image enables us to record the 3-D movement of particles as spiral streaks on a single image. Every shape of the spiral streak on the image plane is related to the position and the velocity of the individual particle. The information about 3-D movement of particles is extracted from the image using an image processing technique. We applied the technique to the measurement of the 3-D water-flow field seeded with tracer particles in a test tank and obtained satisfactory results.