With the development of the helium-neon laser (He-Ne) at the Bell Telephone Laboratories in 1962, the optics community had available a source of continuous wave electromagnetic radiation highly concentrated at a wavelength of 632.8 nanometers (nm), in the red portion of the visible spectrum [REF].
The instrument was soon called the laser Doppler velocimeter (LDV) and the technique laser Doppler velocimetry, also abbreviated LDV.