A 3-D imaging system is described. The 3-D imaging system comprises an illumination unit for emitting light onto a target scene, an imaging sensor for imaging the target scene by detecting scattered/reflected light, an evaluation unit for determining distance information related to the target scene on the basis of light propagation time and synchronization means for providing synchronization information to the evaluation unit. The synchronization means comprises means for generating an electrical reference signal in the illumination unit, the reference signal being directly derived from the emitted light.