Geometrical compression of lidar return signals.

The dynamic range of lidar return signals has been calculated for coaxial transmitter-receiver geometries via the spatial distribution of irradiance in the detector plane as a function of distance z. It is shown that the z(-2)dependence from the lidar equation can be converted to almost constant signal amplitude for distances up to 3 km by suitable and realistic choice of the geometric parameters. On the other hand, no signal degradation with respect to the lidar equation occurs at large distances. This geometrical compression of lidar return signal amplitudes is rated superior to electronic compression methods such as gain switching or logarithmic amplification.