Abstract: A scanning and detecting device is disclosed which reflects radiation off an object and detects this radiation in order to establish irregularities or faults in a face of the object. Lighting fixtures light the object and the reflected light is detected by three detecting cameras placed over a slit in a screen. The size of the slit is adjusted to provide uniform reflected light intensity in the absence of imperfections. The size of the slit is controlled by the use of thin metal bands which are adjusted by cam screws and are clamped by adjustable clamps.