Multi-aperture coherent Doppler lidar for mitigation of turbulence and vibration induced speckle effects

Summary form only given. A 1.55 /spl mu/m coherent Doppler laboratory lidar system has been developed to study the enhancement in the measured lidar SNR through the use of a dual aperture balanced heterodyne array using incoherent and coherent summation of the detected array signals. A 30 mW, 1.55 /spl mu/m, single frequency diode laser is used as the main excitation source. The beam is split into a LO channel and a main projected beam followed by a 27 MHz acousto-optic shifter. The main portion is sent to a rotating target and the reflected backscatter is collected by two spatially separated single mode, polarization preserving fibers. The two collected signals are branched into in-phase and quadrature signals for balanced heterodyne detection. The four channels are detected and the electrical signals are analyzed using spectrum analyzers, channel oscilloscopes, and then computer interfaced. We have studied the effects of target rotation on the Doppler center frequency, spread of the Doppler shifted signal, and the influence of the geometrical and velocity aspects of the target.