Optimization of a laser diode anemometry system
Abstract
A laser Doppler anemometry system using a laser diode as the light source is investigated. A computational procedure for optimizing a Doppler anemometry unit is developed. The aim is the minimization of the following measurement uncertainties: broadening of the signal frequency due to distortion of wavefronts in the measuring volume; frequency broadening caused by misalignment of the lens that collimates the diverging beam of the laser diode; changes in the wavelength of laser and hence the calibration constant of the system resulting from fluctuations in the operating temperature and current. The calculations are based on a generalized relation for the frequency broadening combined with a simulation model for the anemometry system. The optical field of a laser diode is described as a product of a Gaussian and a truncated Lorentzian distribution. The influence of design parameters is examined by means of a computational study and an experimental evaluation of the measuring volume. Flow measurements are taken. The performance is found to improve with the use of a small focal length collimator and a large focal length front lens.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 December 1988
 Bibcode:
 1988STIN...9116364M
 Keywords:

 Laser Anemometers;
 Laser Doppler Velocimeters;
 Optimization;
 Semiconductor Lasers;
 Velocity Measurement;
 Computerized Simulation;
 Frequency Measurement;
 Laser Beams;
 Thermal Blooming;
 Lasers and Masers