A safety apparatus for a medical system comprises at least one source for emitting an optical signal, and at least one sensor for detecting the optical signal emitted by the at least one source. The at least one source and the at least one sensor are disposed such that an object located in a region to be monitored is detected. A control unit is provided for controlling the medical system, so that the medical system is switched into a safe operating state or interrupted if the detected object is unexpected or unwanted in the monitored region.