Illumination Device and Method for Calibrating an Illumination Device over Changes in Temperature, Drive Current, and Time

摘要

An illumination device and method is provided herein for calibrating individual LEDs in the illumination device, so as to obtain a desired luminous flux and a desired chromaticity of the device over changes in drive current, temperature, and over time as the LEDs age. The calibration method may include subjecting the illumination device to a first ambient temperature, successively applying at least three different drive currents to a first LED to produce illumination at three or more different levels of brightness, obtaining a plurality of optical measurements from the illumination produced by the first LED at each of the at least three different drive currents, obtaining a plurality of electrical measurements from the photodetector and storing results of the obtaining steps within the illumination device to calibrate the first LED at the first ambient temperature. The plurality of optical measurements may generally include luminous flux and chromaticity, the plurality of electrical measurements may generally include induced photocurrents and forward voltages, and the calibration method steps may be repeated for each LED included within the illumination device and upon subjecting the illumination device to a second ambient temperature.

主权项

1. A method for calibrating an illumination device comprising at least a first light emitting diode (LED) and a photodetector, the method comprising:
subjecting the illumination device to a first ambient temperature; successively applying at least three different drive currents to the first LED to produce illumination at three or more different levels of brightness; obtaining a plurality of optical measurements from the illumination produced by the first LED at each of the at least three different drive currents, wherein the plurality of optical measurements comprise luminous flux and chromaticity; obtaining a plurality of electrical measurements from the photodetector, wherein the plurality of electrical measurements comprise a plurality of photocurrents, which are induced on the photodetector by the illumination produced by the first LED at each of the at least three different drive currents, and forward voltages that are measured across the photodetector before, during or after each induced photocurrent is measured; and storing results of the obtaining steps within the illumination device to calibrate the first LED at the first ambient temperature.