A sensor for checking a value document which is configured such that for the check of the value document this is introducible into a measuring plane of the sensor and for its check is transported along a transport direction (x) past the sensor, the sensor comprising: - at least one light source through which a value document present in the measuring plane can be illuminated in a region of the measuring plane, - a detection device having at least two photodetectors arranged side by side for detecting detection light which, upon the check of the value document, emanates from the value document in a detection region of the measuring plane due to the illumination with the light source, wherein the detection light of the value document is detectable by the photodetectors in at least two different spectral regions, - a collecting optic common to the photodetectors, through which the detection light emitted by the value document in the detection region can be collected and collimated to a light beam, wherein the photodetectors are arranged after the collecting optic, viewed along the optical axis (a) of the detection ray path, characterized in that - each of the photodetectors has associated therewith a detector lens which is arranged after the collecting optic and before the respective photodetector, viewed along the optical axis (a) of the detection ray path, and - the detector lenses are arranged side by side such that each detector lens receives a partial light beam (L') of the light beam collimated by the collecting optic and directs it onto the respective photodetector, so that the detection region whose detection light is detectable at the same point in time by the photodetectors substantially coincides for the different photodetectors, wherein the optical axes (b) of the detector lenses are respectively arranged outside the optical axis (a) of the detection ray path such that the collimated light beam is divided laterally by the detector lenses into at least two partial light beams (L'), wherein the optical axes (b) of the detector lenses preferably have the same lateral distance from the optical axis (a) of the detection ray path, and - at least two of the photodetectors of the detection device are arranged offset from each other perpendicularly to the transport direction of the value document, but at the same position (xo), viewed along the transport direction (x). - at least one light source through which a value document present in the measuring plane can be illuminated in a region of the measuring plane, - a detection device having at least two photodetectors arranged side by side for detecting detection light which, upon the check of the value document, emanates from the value document in a detection region of the measuring plane due to the illumination with the light source, wherein the detection light of the value document is detectable by the photodetectors in at least two different spectral regions, - a collecting optic common to the photodetectors, through which the detection light emitted by the value document in the detection region can be collected and collimated to a light beam, wherein the photodetectors are arranged after the collecting optic, viewed along the optical axis (a) of the detection ray path, - each of the photodetectors has associated therewith a detector lens which is arranged after the collecting optic and before the respective photodetector, viewed along the optical axis (a) of the detection ray path, and - the detector lenses are arranged side by side such that each detector lens receives a partial light beam (L') of the light beam collimated by the collecting optic and directs it onto the respective photodetector, so that the detection region whose detection light is detectable at the same point in time by the photodetectors substantially coincides for the different photodetectors, wherein the optical axes (b) of the detector lenses are respectively arranged outside the optical axis (a) of the detection ray path such that the collimated light beam is divided laterally by the detector lenses into at least two partial light beams (L'), wherein the optical axes (b) of the detector lenses preferably have the same lateral distance from the optical axis (a) of the detection ray path, and - at least two of the photodetectors of the detection device are arranged offset from each other perpendicularly to the transport direction of the value document, but at the same position (xo), viewed along the transport direction (x).