A detector (110) for an optical detection of at least one object (112) is disclosed. The detector (110) comprises: —at least one longitudinal optical sensor (114), wherein the longitudinal optical sensor (114) has at least one sensor region (134), wherein the longitudinal optical sensor (114) is designed to generate at least one longitudinal sensor signal in a manner dependent on an illumination of the sensor region (134) by a light beam, wherein the longitudinal sensor signal, given the same total power of the illumination, is dependent on a beam cross-section of the light beam in the sensor region (134); —at least one transfer device (128), wherein the transfer device (128) exhibits at least two different focal lengths in response to at least one incident light beam, wherein the transfer device (128) is adapted to adjust the beam cross-section of at least one first light beam (130) having a first wavelength and at least one second light beam (132) having a second wavelength different from the first wavelength depending on the wavelength of respective light beams, such that in the sensor region (134), the beam cross-section of the first light beam (130) is different from the beam cross-section of the second light beam (132); and—at least one evaluation device (156), wherein the evaluation device (156) is adapted to differentiate the longitudinal sensor signal of the longitudinal optical sensor (114) into a first longitudinal sensor signal dependent on the illumination of the sensor region (134) by the first light beam and into a second longitudinal sensor signal dependent on the illumination of the sensor region (134) by the second light beam, wherein the evaluation device (156) is designed to generate at least one item of information on a longitudinal position of the object (112) by evaluating the first longitudinal sensor signal and the second longitudinal sensor signal.