Linear array focused-laser differential interferometry for single-shot multi-point flow disturbance measurements

In this Letter, a modification of the well-known focused-laser differential interferometer (FLDI) is demonstrated, with the primary focus being increasing the number of probed locations efficiently. To generate multiple beams in the FLDI system, a diffractive optical element is used. This approach is significantly more cost-effective and easier to implement than the current approach of generating multiple FLDI beam pairs using a series of Wollaston prisms. The measurements shown here utilize a 1D linear array of points, and the ability to generate a 2D array is demonstrated using two linear diffractive optical elements in tandem. Therefore, this technique, referred to as linear array FLDI (LA-FLDI), is able to provide measurements of fluid disturbances at multiple discrete locations while allowing for high data acquisition rates (>1 MHz). This technique provides a much simpler approach to multipoint FLDI measurements and can increase the throughput of FLDI measurements in impulse aerospace testing facilities.