Abstract: A process for monitoring the light intensity of an optical signaling or display device which has a plurality of light sources arranged on the front of a printed circuit board in a rasterized luminous field (F) and a diffusion lens arranged in the main light emission direction of the light sources or a light-collecting intermediate lens and a diffusion lens arranged in sequence, characterized by the process steps of using an at least partly transparent printed circuit board for arrangement of the light sources, arranging of sensors to detect light on the rear of this circuit board, detecting the light beams emitted rearwards towards the printed circuit board by the light sources and/or detection of the light beams reflected at the intermediate lens or, if this is omitted, at the diffusion lens and passing through the printed circuit board, conversing the detected light beams into signals which are passed to an electronic system, and initiating an action such as increasing the electrical power, advance warning