The development of the helium–neon laser (He-Ne) in 1962 at the Bell Telephone Laboratories provided the optics community with a continuous wave electromagnetic radiation source that was highly concentrated at a wavelength of 632.8 nanometers (nm) in the red portion of the visible spectrum. It was discovered that fluid flow measurements could be made using the Doppler effect on a He-Ne beam scattered by small polystyrene spheres in the fluid.
At the Research Laboratories of Brown Engineering Company (later Teledyne Brown Engineering), this phenomenon was used to develop the first laser Doppler flowmeter using heterodyne signal processing. This instrument became known as the laser Doppler velocimeter and the technique was called laser Doppler velocimetry. It is also referred to as laser Doppler anemometry.
Early laser Doppler velocimetry applications included measuring and mapping the exhaust from rocket engines with speeds up to 1000 m/s, as well as determining flow in a near-surface blood artery. Similar instruments were also developed for solid surface monitoring, with applications ranging from measuring product speeds in production lines of paper and steel mills to measuring vibration frequency and amplitude of surfaces.