Influence of wind shear on laser propagation Joe Watkins Reza Malek-Madani Svetlana Avramov-Zamurovic
Experimental set up to measure the influence of wind shear on laser light propagation • Laser source: HeNe red laser 2 mW • Laser propagated through a tunnel • Target was observed using beam splitter and camera with 12 bit resolution (possibility to measure 4095 different light intensities) • A phase screen was inserted in the tunnel in order to introduce wind shear perpendicular to the propagation of the laser beam • Three experiments were carried out: NO wind Wind 3m/s Wind 5m/s • Each experiment was monitored for three minutes using camera that recorded changes in the laser light intensities at the target, at the rate of 20 frames per second Wind shear refers to the variation of wind speed over horizontal distances.
Comparison between the 5 m/s wind and no wind conditions Wind 5 m/s No wind All of the frames added together Only one location indentified for ‘hot’ pixel Locations for the maximum intensity for each of 3700 frames
Comparison between the 5 m/s wind and no wind conditions Wind 5 m/sIntensity values for all of the framesVery little variation : mean 1651.8 std = 9.1614averaging radius 10 pixels No WindIntensity values for all of the framesVery little variation : mean 1647.9 std = 9.7914averaging radius 10 pixels
Data Histogram Comparison for Wind Influence Experiments From each experiment 5 runs were averaged and histograms are presented • Mean light intensity for each run for all of the experiments
Data Histogram Comparison for Heat Influence Experiments * No heat * HEAT Phase Screen # of occurrences
Discussion The wind perpendicular to the beam propagation does not have major influence on light intensity fluctuations, compared to the influence the heat phase screen. We were able to establish slight shift in mean value and the shape of the histogram for the three experiments with variable wind velocities Individual Probability Density Functions for each run did not demonstrate reliable differentiation between the experiments.