The disclosed scanner allows detecting decay time characteristics of light emitted by a luminescent marking on an item which is transported, even at high speed, on a distribution/production line. The detection zone of the scanner's light sensor has a shape elongated along a path of the moving item, and the responsivity of the light sensor, within the wavelength range of the emitted luminescence light, is uniform over the detection zone. The control unit of the scanner is further operable to adapt the drive current, or drive voltage, powering its excitation light source to accordingly adapt the intensity of the excitation light delivered to the marking so that its light sensor can reliably measure the corresponding luminescence light response, and thus accurately determine a corresponding decay time value.