Abstract: A device for detecting quality alterations in bulk goods transported on moving belt conveyors comprising a pulsed, monochromatic light source (1), frequency multipliers (2) and dichroic mirrors (3) or prisms to simultaneously generate several light beams having different wavelengths and irradiate several spots (6) of the flow of bulk goods on the belt conveyor (7). In addition, a detector unit is provided for observing the irradiated spots (6) in the flow of bulk goods for measuring excited photoluminescence, reflected light and temperatures, as well as for carrying out signal analysis with time resolution. The triggering of the device is adapted to the running speed of the belt conveyor (7) and allows the same area of the moving flow of the bulk goods to be irradiated several times in the spots (6) with beams having different wavelengths. The signal analysis includes detecting signal intensity and the fading behaviour of the signals in defined spectral ranges.