Accuracy in laser anemometry

Examines the fundamental limitations imposed by photodetection noise on the accuracy with which flow velocity can be determined in laser anemometry. A variety of processing methods are examined for the Doppler-difference or time-of-flight (two-spot) optical geometries. It is shown that in most situations the most accurate methods of velocity determination are either to fit the autocorrelation function, or power spectrum, in Doppler-difference anemometry, or to determine the peak separation in two-spot anemometry by detecting the median of the delayed autocorrelation function peak. Peak-intensity detection in two-spot anemometry is demonstrated to be superior where well-separated beams can be employed.