A micropulse lidar system is described that comprises, a laser light source for emitting a pulsed laser beam, beam shaping means for shaping the intensity distribution of said beam such that said beam has a substantially annular intensity distribution in cross-section, a Schmidt-Cassegrain telescope for transmitting the annular beam to an atmospheric target and for collecting backscattered light returned from said target, and means for detecting and analyzing said backscattered light. The system has higher efficiency and better signal-to-noise ration than a corresponding system without the beam shaping means. There is also a disclosed a method for optimising the design of the beam shaping means.