Editing Anemometer (section)

===Laser Doppler anemometers===
In [[laser Doppler velocimetry]], laser Doppler anemometers use a beam of light from a [[laser]] that is divided into two beams, with one propagated out of the anemometer. Particulates (or deliberately introduced seed material) flowing along with air molecules near where the beam exits reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beam. When the particles are in great motion, they produce a [[Doppler shift]] for measuring wind speed in the laser light, which is used to calculate the speed of the particles, and therefore the air around the anemometer.<ref>{{cite web|last=Iten|first=Paul D.|date=29 June 1976|url=http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=3966324|title=Laser Doppler Anemometer|publisher=United States Patent and Trademark Office|access-date=18 September 2006}}</ref>
[[File:Ultrasonic Windsensor.png|thumb|Fixed mounted 2D ultrasonic anemometer with 3 paths. <br />Central spike keeps birds away.]]