A method for identifying an obstacle (O) in the laser beam (F) of a lidar system includes: commanding the transmission of a laser beam (F); and receiving a lidar signal (S) corresponding to the reflection of the beam (F) on a diffuser present in the beam (F). The detection method further includes: evaluating a set of first parameters of the lidar signal, the set of first parameters including at least an amplitude and a duration, a first detection moment being defined for the lidar signal (S), the duration being defined at each moment as the time elapsed since the first detection moment; identifying an obstacle (O) present in the beam (F) when the amplitude is greater than a first threshold and the duration is greater than a second threshold; and decreasing the power of the beam (F).