Described herein is a detector for determining a position of at least one object. The detector includes:



at least one transfer device;
at least one illumination source adapted to generate at least one light beam for illuminating the object;
at least one first optical receiving fiber and at least one second optical receiving fiber;
at least two optical sensors; and
at least one evaluation device being configured for determining at least one longitudinal coordinate z of the object by evaluating a combined signal Q from the sensor signals.