Patent ID: 9024535
Filing Date: 2015-05-05
Classification: H05B,Y02B

Abstract:
1. Optical lighting apparatus having a constant luminance output comprising: a plurality of light-emitting devices having a desired luminance output; a light diffuser positioned to receive the output of the light-emitting devices; a photodetector adapted to receive light energy reflected off the light diffuser and for generating an output signal proportional to the amount of received incident light at the photodetector; an optical insulator positioned between the light-emitting devices and the photodetector to block the photodetector from receiving light directly from the light-emitting devices; a controller circuit for variably controlling the drive current to the light-emitting devices in response to the output signal from the photodetector; a temperature sensor proximate to the photodetector for sensing the temperature thereat; a heater proximate to the photodetector and having a preset temperature greater than a highest expected ambient temperature to maintain the temperature of the photodetector at the preset temperature to permit the output luminance from the light-emitting devices to be constant and independent of changes in ambient temperature less than the highest expected ambient temperature.