Process and arrangement for the measurement of physical values of light scattering moving particles by means of a laser doppler anemometer

US5781283A · kind A · utility

Assignee

• JENOPTIK GmbH · DE

Inventors

• Ehrhard Dammann · Jena, DE
• Juergen Bauer · Burgkunstadt, DE

Key dates

• Filing date: May 10, 1996
• Grant date: Jul 14, 1998
• Expiry date: May 10, 2016

Classification

• Technology area (CPC G): Physics
• CPC primary: G01P5/26
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A process is provided for measuring physical values of light-scattering moving particles by means of laser Doppler anemometry and to a corresponding laser Doppler anemometer (LDA) with phase modulation. Generating a moving intensity-modulated superimposition signal in the measured volume of a LDA which is based on an uncomplicated driving of the phase modulator is achieved by having the phase modulator being driven by two sinusoidal driving signals with different frequencies (.omega..sub.1, .omega..sub.2) which are coupled so as to be fixed with respect to phase and frequency and wherein one frequency (.omega..sub.2) is an integer multiple of the other frequency (.omega..sub.1), and a filter frequency (f.sub.F) which is a common multiple of the two frequencies (.omega..sub.1, .omega..sub.2) is filtered out from the output signal of the receiver by a bandpass filter. For this purpose, one of two sidebands occurring in the output signal of the receiver is suppressed by the appropriate amplitude adjustment of the driving signals at the phase modulator. The process and related arrangement are used for measuring velocity in flowing media and for measurements of length and acceleration o…