Led illumination source/display with individual led brightness monitoring capability and calibration method

摘要

An LED area illumination source/display ( 10 ) such as an electronic billboard is made up of a number of individual pixels with each pixel including a number of LEDs, e.g., a red ( 18 ), blue ( 19 ) and green LED ( 20 ), with each LED representing a primary color being arranged to be energized separately. At least one light sensor (22) is incorporated into the display for providing a measure of the light emitted from each LED representing a primary color in each pixel. The source/display ( 10 ) is susceptible of being self-calibrated by initially energizing the LEDs ( 18, 19, 20 ) at less than a maximum level and increasing the energization level as necessary during use to restore the original light output of degraded LEDs.