Patent ID: 6963059

Claim:
An optical sensing device comprising: a light source for illuminating a surface portion with radiation; a photodetector device having at least one photosensitive element responsive to radiation reflected from the illuminated surface portion; and conversion means for integrating an output signal of said at least one photosensitive element over time during an integration period of variable duration, which duration depends on power of said light source and level of radiation reflected from the illuminated surface portion, said optical sensing device further comprising a regulating system for controlling the power of the light source as a function of a comparison between a parameter representative of the evolution of the integration of the output signal of said at least one photosensitive element and at least one reference value; wherein said representative parameter is a rate of evolution of the integrated output signal of said at least one photosensitive element, said regulating system comprising: means for determining said rate of evolution during the integration period; comparator means for comparing the determined rate of evolution with at least one reference rate value; and power control means for controlling the power of the light source as a function of the result of the comparison between the determined rate of evolution and said at least one reference rate value.