Patent ID: 8324817

Claim:
An LED-based light tube for use in a conventional fluorescent fixture comprising: a housing including a light transmitting portion; at least one electrical connector attached to the housing and configured for engagement with the conventional fluorescent fixture; at least one LED arranged to produce light in a direction toward the light transmitting portion; a sensor operable to detect a brightness level and output a signal corresponding to the detected brightness level; and a controller in electrical communication with the at least one electrical connector and operable to compare the signal to a predetermined value corresponding to a desired brightness level and control an amount of power provided to the at least one LED in response to the signal to adjust the light produced by the at least one LED to achieve the desired brightness level, wherein the controller is operable to estimate an efficiency of the at least one LED at least partially based on the brightness level detected by the sensor and wherein the estimated efficiency of the at least one LED is at least partially based on a comparison between a power consumption of the at least one LED and the brightness level detected by the sensor.