computer 8 by means of said interface 8 to enable modification of the control signals that the graphic card of the computer 8 emits in driving the display 1 when it is not possible to respect the standard ambient conditions consequently it is clear that the display 1 is connected to the computer 8 in the self calibration step it is necessary to convey the brightness emitted by the display onto the sensor 3 as likewise it is necessary to bring the sensor 4 up to the display to adjust white balancing so that the microcomputer can regulate via the computer 8 the emission of the graphic card with which the latter is equipped advantageously use of a dome or deflector 7 during self calibration means that the sensor 4 is not impinged upon by environmental light but only by the light emitted by the display lastly in a preferred embodiment said illumination sensor 3 is a tsl257 e35 manufactured by texas instruments the intrinsic characteristics of construction of which guarantee its reliability but above all robustness of the system in regard to disturbance on the supply and or deriving from the environmental climatic conditions so that the factory calibration of the circuitry that drives said component guarantees perfect behaviour of the system throughout its service life without calling for any further intervention it is clear that the fact of entrusting calibration of the display 1 to a sensor 4 of extremely high precision as compared to the precision of the device 1 radically solves the problem of maintenance interventions during.