An optical module for an optical unit associated with forming a light curtain for monitoring a protective or surveillance field. The optical module includes at least one radiation emitting and/or radiation receiving element for transmitting and/or receiving a radiation beam associated with forming a light curtain. The optical module includes a module body for mounting a radiation transmitter/receiver carrier that carries the at least one transmitting and/or receiving element associated with the radiation beam. The module body has at least one alignment element for aligning the optical module within a support element that forms an outer housing of the optical unit.