Backscatter particle image velocimetry via optical time-of-flight sectioning

Conventional particle image velocimetry (PIV) configurations require a minimum of two optical access ports, inherently restricting the technique to a limited class of flows. Here, the development and application of a novel method of backscattered time-gated PIV requiring a single-optical-access port is described along with preliminary results. The light backscattered from a seeded flow is imaged over a narrow optical depth selected by an optical Kerr effect (OKE) time gate. The picosecond duration of the OKE time gate essentially replicates the width of the laser sheet of conventional PIV by limiting detected photons to a narrow time-of-flight within the flow. Thus, scattering noise from outside the measurement volume is eliminated. This PIV via the optical time-of-flight sectioning technique can be useful in systems with limited optical access and in flows near walls or other scattering surfaces.