I am presenting you with the first known technology of safe capacitive sensors.
So far, most of the sensors authorized to protect persons in working surroundings operate as tactile sensors or as barriers, typically light barriers. This limits the practical usefulness. If you intend to detect the approach of a person to an arbitrary surface you have to set up an additional (safety) surface in a certain distance. The penetration of this safety surface must be registered. With light barriers or cameras this is only possible in simpler cases at the present state of the art.
Another possibility to detect someone is to use his or her electrical capacity in relation to the surroundings is.