A ground-based incoherent Doppler lidar system uses the edge of a high-resolution spectral filter to measure wind speed with an accuracy of 10-25 cm/s and a spatial resolution of 15-30 m, a significant improvement over present methods. The edge filter measures the frequency of a small portion of the pulsed 1.06-µm output from a Nd:YAG laser, while the major portion of the output is tuned so that the laser wavelength is spectrally located on the stee¥edge of the filter. Because of the stee¥edge of the optical filter, small shifts in frequency caused by the Doppler shift of the backscattered light are detected as significant amplitude changes, yielding high measurement sensitivity. Using a 100-MH¥filter, for example, a wind speed of 1 m/s will produce an amplitude variation of 4%, making it easily detectable, and the differential nature of the measurement makes it insensitive to linewidth and frequency drift of the laser and filter.
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