4.pi. laser Doppler anemometer (LDA) for measuring the velocitie

Details 4.pi. laser Doppler anemometer (LDA) for measuring the velocitie 4.pi. laser Doppler anemometer (LDA) for measuring the velocitie

1989-03-22

1991-03-05

Wallace, Linda J.

Optics: measuring and testing

Velocity or velocity/height measuring

With light detector

356345, G01P 336, G01B 902

Patent

active

049972723

ABSTRACT:
Laser Doppler anemometer with a wavelength-stabilized laser diode (1) whose beam after splitting (7) is so concentrated in a definite area (9) of a particle-containing flow of a fluid with the velocity (17) that in this area (9) an interference fringe pattern is produced, and with at least one semiconductor photodiode (13) on which the laser beams (10, 11) progressing from the area (9) are refocussed after elimination of scattered light fractions by a scattered light trap (diaphragm stop) (14), for the detection of the difference signal I between incident light intensity I.sub.o and scattered light intensity I.sub.scatter which the particles contained in the fluid emit into the whole solid angle 4.pi., where I=I.sub.o -I.sub.scatter. By detection of the laser beam of the intensity I which is modulated with the Doppler frequency after having passed through the point of measurement (9), the whole light intensity I.sub.scatter emitted by the particle into the solid angle 4.pi. can be utilized for the signal-to-noise ratio at the photodetector, and if suitable semiconductor photodiodes are used, the direction of flow can be identified.

REFERENCES:
patent: 3895872 (1975-07-01), Dandliker et al.
patent: 4373807 (1983-02-01), Gouesbet
patent: 4397550 (1983-08-01), Matsuda et al.
patent: 4537503 (1985-08-01), Liu
patent: 4537507 (1985-08-01), Hess
patent: 4540283 (1985-09-01), Bachalo
patent: 4551018 (1985-11-01), Mannava et al.
patent: 4725136 (1988-02-01), McCullough et al.
patent: 4807990 (1989-02-01), Keefer
patent: 4843564 (1989-06-01), Jenson

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