Proximity Sensors
A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. Proximity sensors often emits an electromagnetic field or a beam of electromagnetic radiation, and looks for changes in the field or return signal.
We have inductive proximity sensors, capacitive proximity switches, photoelectric switch sensors, magnetic sensors, etc with both matel and plastic housing.
Pepperl + Fuchs
Honeywell
Turck
OMRON sensors.