CHARACTERIZATION OF PULSED COHERENT DOPPLER LIDAR WITH THE SPECKLE EFFECT

The relationships among heterodyne efficiency gamma, number of speckle cells M, and the ratio of receiver area to coherence area S(R)/S(C) f or a pulsed coherent laser radar (CLR) are written through the use of mutual coherence functions. It is shown that numerical values for S(R) /S(C) that follow Goodman's definition [J. W. Goodman, in Laser Speckl es and Related Phenomena, J. C. Dainty, ed. (Springer-Verlag, Berlin, 1975), pp. 9-75] or that are obtained through the use of a transverse- field coherence length agree. In the frame of the Gaussian model propo sed by Frehlich and Kavaya [Appl. Opt. 30, 5325 (1991)] a new equation is derived: M = (1 + S(R)/S(C)). This equation agrees with our experi mental results. Our theoretical analysis shows that the number of spec kle cells for an optimal monostatic CLR system is M approximately 4. A n experiment has been conducted with a ground-based pulsed CO2 LIDAR a nd remote hard targets to study the probability density function of LI DAR returns as a function of M and to study the dependence of M on S(R )/S(C). An assessment of CLR performance through the use of M or the c ollecting aperture S(R) is discussed.