The present invention relates to a laser anemometer making it possible to determine the relative velocity between the anemometer and an ambient medium. The architecture of the anemometer includes a laser source, emission and reception optics for focusing a laser beam onto a measurement zone containing particles in suspension in the ambient medium and for receiving the radiation back-scattered by the particles. It also includes an optical mixer for mixing the received radiation and reference radiation representing the radiation emitted by the source, and a detector at the output of the mixer. The relative velocity between the anemometer and the ambient medium is determined by computation on the basis of the Doppler effect generated by the radiation and detected by the detector. The laser source is located remotely from a common support which carries the optical emission and reception system as well as the mixer. It is connected to this common support by at least one optical fiber. The detector is also remotely located and connected by at least one optical fiber. The main emission channel of the emission and reception system carried by the support is produced with the aid of unguided optics.
A method and apparatus for performing simultaneous multi-point measurements of multiple velocity components in a gas flow is described. Pulses of laser light are directed to a measurement region of unseeded gas to produce Rayleigh or Mie scattered light in a plurality of directions. The Rayleigh or Mie scattered light is collected from multiple directions and combined in a single collimated light beam. The Rayleigh or Mie scattered light is then mixed together with a reference laser light before it is passed through a single planar Fabry-Perot interferometer for spectral analysis. At the output of the interferometer, a high-sensitivity CCD camera images the interference fringe pattern. This pattern contains the spectral and spatial information from both the Rayleigh scattered light and the reference laser light. Interferogram processing software extracts and analyzes spectral profiles to determine the velocity components of the gas flow at multiple points in the measurement region. The Rayleigh light rejected by the interferometer is recirculated to increase the accuracy and the applicability of the method for measurements at high temperatures without requiring an increase in the laser energy.
