Abstract

Based on differential absorption and scattering technique, the presented lidar-system use as emitter a tunable CO₂ laser. The laser beam is emitted, alternatively, at two frequencies v₁ and v₂, in a sufficiently narrow spectral interval, to can assume that the volume extinction coefficients of atmosphere (due to aerosol and molecular scattering) are constant. The control of emitted lines is made using a computer controlled step motor system that rotates the diffracting grating of the laser resonator. To measure the range and velocity of pollutant clouds, the laser beam is acousto-opticaly modulated using the "chirp" technique. This principle was described in a previous paper [1].

© 1996 IEEE