Laser doppler velocimeter
AssigneesAgency of Industrial Science and Technology, Ministry of International Trade & Industry
InventorsKiyofumi Matsuda, Tomoaki Eiju
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Abstract
A laser Doppler velocimeter using two laser beams, when used for the measurement of the flow velocity of slow moving particles, fails to provide the measurement because the Doppler frequency and the pedestal component overlap on the power spectrum. This difficulty is eliminated by having a prism disposed in the path of one of the laser beams used. When this prism is continuously moved, the pedestal component and the Doppler frequency are separated from each other on the power spectrum, enabling the velocimeter to effect the measurement easily and accurately.
Claims7
A laser Doppler velocimeter adapted to determine the velocity of flow of particles in motion by causing two coherent beams to impinge upon one point of the path of said particles thereby producing scattered light and a consequent interference beat, detecting in said interference beat the Doppler frequency due to the Doppler shift caused by the particles in motion and calculating the velocity of motion of the particles based on the Doppler frequency, which velocimeter is provided in the path of one of said two beams with at least one prism having an incident plane arranged perpendicular to the path of the incident beam and a refractive plane being at angles with the incident plane, said prism being adapted to be moved in a direction parallel to the refractive plane for producing continuous change in the length of the beam path therethrough, thereby to modulate the frequency of the beam.
Dependencies are inferred from the claim text.