The speckle phase statistics for a CO2 cw coherent lidar system were measured in the Fraunhofer diffraction region using an optical heterodyne technique.1 The transmitted laser beam propagated 1000 m through a turbulent atmosphere before striking a diffuse target. The beam was scattered from the target and created a speckle pattern in the receiver plane of the system. The returned radiation (speckle pattern) was mixed with an optical local oscillator to create a heterodyned signal at 100 kHz. Since the phase of the optical wave is preserved in the heterodyne process, it can be recovered from the signal.
© 1989 Optical Society of AmericaPDF Article