IMAGE SHIFTING FOR PIV USING BIREFRINGENT AND FERROELECTRIC LIQUID CRYSTALS

摘要

This paper discusses a new implementation of electrooptical image shifting, used to resolve directional ambiguity in particle image velocimetry (PIV) measurements. The setup uses a ferroelectric liquid crystal (FLC) as a polarization rotator and a birefringent calcite plate as a shifter. The system can be used with non-polarized light sources and fluorescent particles. The minimum shifting time (pulse separation) is approximately 100 mu s. This compact electrooptical device is usually positioned in front of the camera lens, though it has also been mounted inside the lens body. Sample vector maps from a turbulent multidirectional flow are included. [References: 12]