The invention relates to an optical sensor (1) for detecting objects and comprising a transmitter (5) emitting transmitted light beams (4), a receiver (7) receiving received light beams (6) and an analyzing and processing unit for analyzing and processing received signals of the receiver (7). An arrangement of plane mirrors (13a-d) is associated with the receiver (7) as a sole receiving optical device (13), with two adjacent plane mirrors (13a-d) adjoining each other with their longitudinal edges. The receiving optical device (13) is arranged at a distance from the receiver (7) such that the distribution of the received light beams (6) reflected back from an object on the plane mirrors (13a-d) is dependent on the distance of the object from the optical sensor (1). By means of the receivingoptical device (13), objects within a depth of field can be detected.