2 in fig1 the path of a ray 14 emitted by one of the led diodes 34 illuminating one of the oled diodes is shown therein the ray 14 is deviated a first time when it penetrates the transparent or translucent material of the collimator 12 this deviation is not visible on account of the proximity between the diode 34 and the corresponding entrance face of the collimator 12 the ray 14 propagates essentially in a straight line in the material of the collimator 12 until it reaches the exit face in the present case an exit facet the ray 14 is then deviated a second time so as to be directed toward a corresponding portion of the oled diode 8 that is near the central portion 4 1 of the substrate 4 in other words the rays emitted by the diodes 34 are deviated by the collimators 12 so as to encounter the corresponding oled diodes 8 in zones of the diodes that are near the optical axis as mentioned above the oled diodes 8 consist of a superposition of a plurality of organic semiconductor layers between two electrodes one of which is transparent in the present case the electrode located to the rear is reflective so that on the one hand the light emitted by the semiconductor layers is effectively directed forward and on the other hand the rays emitted by the led diodes 34 in the direction of the oled diodes 8 are reflected the electrode located to the front may therefore be completely.