at Princeton University have developed a novel technique for measuring the
velocity of air flow by observing velocity-related frequency shifts in light
scattered from moving air molecules or particles suspended in the moving air.
Scattered light is passed through an absorption line filter window gas cell with
a notch type attenuation profile as a function of frequency. The scattering
region is illuminated with a narrow linewidth light source coincident in
frequency with a strong absorption line of an absorption line filter. Light
scattered from stationary air molecules or particles is passed into the filter
and a portion of that light falling within the strongly attenuated region is
absorbed. As the velocity of the molecules or particles in the scattering region
increases, the scattering frequency is shifted d ue to the Doppler effect, and
the portion of the scattered light falling beyond the filter cutoff increases.
This causes the intensity of the light transmitted through the filter to
increase. The intensity of the transmitted light is directly related to the
shifted frequency, thereby providing a measurement of the velocity of the air.
The cell transmission can be quantified by comparing the intensity of the light
transmitted through the cell with the intensity seen in the absence of the cell,
thereby lea ding to a quantitative measure of the relative velocity between the
light source and scattering volume.
anticipated that this method will be useful for real time measurement of flight
speed and for wind tunnel measurements.
protection has been granted as US patent #4,988,190
seeking industrial collaborators to commercialize this technology. For more
William H. Gowen
Office of Technology Licensing and Intellectual
New South Building
Princeton, NJ 08544-0036
(609) 258-1159 fax