This invention relates to a process for regulating the exposure time of a light sensor, characterized in that it comprises the following steps: a) setting the exposure time of the sensor to a value selected in a first range of M prefixed values defined between a minimum and a maximum value; b) acquiring an image of an object on the sensor, such image comprising a plurality of luminous pixels; c) analyzing the acquired image in order to detect its level of luminosity; d) comparing the detected level of luminosity with a prefixed higher (lower) global threshold level representative of a condition of overexposure (under-exposure) of the image; e) varying the exposure time of the sensor and iteratively repeating the previous steps until an optimum exposure time equal to the highest (lowest) exposure time is found, amongst the ones set, for which the image presents a level of luminosity which is smaller (greater) than the prefixed higher (lower) global threshold level.