Process and arrangement for the evaluation of laser doppler signals

US6078384A · kind A · utility

Assignee

• JENOPTIK GmbH · DE

Inventors

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

Key dates

• Filing date: Aug 7, 1998
• Grant date: Jun 20, 2000
• Expiry date: Aug 7, 2018

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02A90/10
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Processes and arrangements for the evaluation of laser Doppler signals, especially in laser Doppler anemometers (LDA) or vibrometers, are disclosed. The object of these processes and arrangements is to find a simple possibility for evaluating laser Doppler signals which retains the advantages of conventional frequency tracking demodulation and permits dependable actual measurements of velocities and derived movement values also for extremely low velocities and discontinuous particle flows. This object is achieved with the use of a laser Doppler anemometer (LDA) with bandpass filtration and frequency tracking demodulation, by generating at least one orthogonal frequency system which, as a sequence of four state intervals in an invertible one-to-one correlation, is formed of two additively superimposed rectangular functions with a phase displacement of .pi./2, a detector signal containing the Doppler frequency (f.sub.D) is compared after bandpass filtering with respect to its phase with the state intervals of the orthogonal frequency system, wherein a change in the phase position relative to the orthogonal frequency system triggers a compensation of the change in Doppler frequency ge…