Abstract: An optoelectronic sensor is provided that has a front screen, a measuring unit, a movable deflection unit, and a contamination test unit moved along with the deflection unit for generating a received contamination test signal from contamination test light reflected at the front screen. In this respect, the contamination light unit has at least two contamination test light transmitters and/or at least two contamination test light receivers to form a plurality of contamination test channels and a control and evaluation unit is configured to detect the object by evaluating a received measurement signal of the measuring unit and to evaluate the contamination of the front screen by evaluating the plurality of received contamination test signals of the plurality of contamination test channels.