Holographic Correlation Velocimetry

We describe a method for measuring three dimensional (3D) velocity fields of a fluid at high speed, by combining a correlation-based approach with in-line holography. While this method utilizes tracer particles contained within the flow, our method does not require the reconstruction of individual particle images. The direct flow reconstruction approach developed here, allows for measurements at seeding densities in excess of the allowable levels for techniques based on particle reconstruction. We outline the theory behind our method, which we term Holographic Correlation Velocimetry (HCV), subsequently applying it to both synthetic and laboratory data. Moreover, because the system is based on in-line holography, it is very efficient with regard to the use of light, as it does not rely on side scattering. This efficiency could be utilized to create a very high quality system at a modest cost. Alternatively, this efficiency makes the system appropriate for high-speed flows and low exposure times, which is essential for imaging dynamic systems