Absorption Line Filter Window and Method for Velocity Measurements by Light Scattering

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Researchers 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.


It is anticipated that this method will be useful for real time measurement of flight speed and for wind tunnel measurements.


Patent protection has been granted as US patent #4,988,190

Princeton is seeking industrial collaborators to commercialize this technology. For more information please contact:

             William H. Gowen
             Office of Technology Licensing and Intellectual Property
             Princeton University
             4 New South Building
             Princeton, NJ 08544-0036
             (609) 258-6762
             (609) 258-1159 fax

Patent Information:
For Information, Contact:
William Gowen
Licensing Associate
Princeton University
Richard Miles
Opto-Electronics/ELE ENG