New Doppler Holographic Technique for Fluid Velocity Visualization and Measurement

Abstract

The analysis and experimental verification of a new quantitative flow visualization technique which measures two-dimensional velocity components and utilizes the temporal filtering properties of holograms is presented. With this technique, the flow field is seeded with particles that scatter light from an illuminating laser beam. The doppler-shifted scattered light is passed through a lens which maps the light to positions in the focal plane of the lens determined by the scattering direction. A hologram is made of the light in the focal plane using a frequency-shifted reference beam. Only the portions of the velocity field having specific two-dimensional velocity components are reconstructed when a small area of the hologram is illuminated.