Abstract: The system comprises a laser transmitter/receiver set which transmits laser radiation and processes the radiation received by retro-reflection and a remotely-placed retro-reflecting and modulating set which modulates the laser radiation and sends it back to the receiver. These two sets are mechanically separated, and one can be placed on board an aircraft and the other on the ground, for example. The modulation is done by a frequency-controlled acousto-optical deflector to obtained the operating conditions of diffraction according to Bragg's law. The laser radiation, after crossing the deflector, is sent back by a catadioptric device along its original path. The double passage through the deflector, on the way out and back, produces a shift in the frequency of the laser radiation, the value of the said shift being equal to twice the control frequency of the deflector. A double axis or single axis optical scanning device is added on, for functioning in a wide field.

Abstract: Laser telemetry and Doppler measurement apparatus using pulse compression has a transmitter for providing a periodic pulsed transmission laser wave having a pair of pulses, one pulse being frequency modulated on one side of a main frequency F.sub.E, and the other pulse being frequency modulated on the other side of the main frequency F.sub.E. The transmitter also provides a reference laser wave having a frequency F.sub.L. A photomixer is adapted for superheterodyne reception of the reference laser wave and a return laser signal which has been reflected from a target. The return laser signal has a Doppler shift frequency F.sub.D. The photomixer provides a beat signal having a frequency F.sub.I plus F.sub.D, where F.sub.I is an intermediate frequency. A Doppler aquisition loop transposes the beat signal frequency and provides a transposed signal to compensate for the Doppler shift. The Doppler acquisition loop provides a coarse compensation signal having a frequency near the frequency F.sub.D.