A pulsed laser beam (3) is discharged from the emitting element (T) to the reflectors (1) and onto a rotating mirror. The rotating mirror (2) scans the laser as it rotates. The diffuse reflection (4) from the sensing object is then returned to the receiving element (R) by means of the rotating mirror. The location of the sensing object (SO) is measured based on the travel time of the laser and the angular information of the rotating mirror. The monitoring area (max. 190°) is divided into 528 segments of 0.36° each by the rotating mirror. An additional sensor (5) detects dirt on the lens’ surface to guarantee functionality.