What is the Doppler Effect, and how does it apply to LIDAR?
The Doppler effect was discovered in 1842 by an Austrian Physicist named Christian Doppler. This effect is characterized by a change in wavelength (or frequency) of a wave due to the motion of either the source or receiver of the waves. In a LIDAR system, the laser light which is characterized by a light wavelength, experiences this wavelength shift as the light scatters off of the moving air molecules or aerosols in the atmosphere. By comparing the incoming and outgoing laser pulses, one can determine the magnitude of the Doppler shift, and convert this into a velocity number. The diagram below shows both the source light (black), and the reflected light (red) separated by a small wavelength due to the Doppler effect.
