Daylight harvesting light fixture and control system for same

An electric lamp comprising a lamp housing defining an aperture, an electrically powered light source mounted in said housing for illuminating a space through said aperture, a power supply for powering said light source, and a photosensor in said housing arranged for sensing illumination in said space through said aperture;

• a switch connected for interrupting and restoring electrical power to said light source to cause a dark interval of duration imperceptible to the human eye;
• circuit means connected to said photosensor and cooperative with said switch means for deriving an ambient illumination signal during said dark interval representative of existing illumination of said space free of contribution from said light source;
• processor means receiving said ambient illumination signal for estimating a supplemental light output requirement from said light source which in combination with said existing illumination suffices to raise total illumination of said space to a target illumination level;
• and
• power control means responsive to said processor means for restoring power to said light source at an adjusted power level for producing said supplemental light output.