A time of flight, TOF, camera unit for an optical surveillance system and an optical surveillance system comprising such a TOF camera is disclosed. The TOF camera unit comprises a radiation emitting unit for illuminating a surveillance area defined by a first plane, a radiation detecting unit for receiving radiation reflected from said surveillance area and for generating a three-dimensional image from said detected radiation, and at least one mirror for at least partly deflecting said emitted radiation into at least one second plane extending across to said first plane and for deflecting the radiation reflected from said second plane to the radiation detecting unit. The TOF camera and the at least one mirror may be arranged on a common carrier element.