Accession Number : ADD001819

Title :   Laser Doppler Velocimeter.

Descriptive Note : Patent,


Personal Author(s) : Farmer,William M ; Hornkohl,James O

Report Date : 29 Jul 1975

Pagination or Media Count : 5

Abstract : This invention relates to the measurement of velocity of a flowing medium, and more particularly to a laser doppler velocimeter measuring fluid velocity in two components. A beam from a laser penetrates a two-dimensional Bragg cell and is diffracted into four output beams each with different frequencies and focused to a point in moving media where two components of velocity are to be obtained. Polarization rotation plates can be used to intercept the four output beams from the two-dimensional Bragg cell in order to adjust the orientation of polarization which eliminates cross-talk. The scattered light from the probe point in the moving medium is optically collected and projected into a photo-multiplier tube, the output thereof being fed to carrier frequency separation and doppler data processing electronics. The two-dimensional Bragg cell consists of a pair of right angle intersecting water columns with a pair of oscillating ultrasonic crystals located near the intersecting point and perpendicular to one each of the water columns. Light penetration from a laser beam is obtained by placing a pair of windows of optical quality on both sides of the cell's housing at the intersecting point of the water columns.

Descriptors :   *Laser velocimeters, *Patents, Optical equipment components, Signal processing, Data processing, Laser beams, Doppler systems, Fluid flow

Subject Categories : Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE