Patent ID: 8111388
Filing Date: 2012-02-07
Classification: G01J

Abstract:
1. A luminous flux monitoring system for a light fixture, the light fixture, coupled to an electric power source, comprising a housing defining an interior space including an interior surface and a transmissive panel disposed a spaced-distance from the interior surface, with the housing including a light source coupled to the interior surface, the system comprising: a light sensor coupled to the interior surface a spaced distance from the light source and aligned to receive light from at least the transmissive panel, the light sensor configured to measure luminous flux in the interior space; and a controller coupled to the electric power source, the light source, and the light sensor, wherein the controller is configured to determine if a light sensor measurement of luminous flux in the interior space is more or less than a reference value of luminous flux, wherein the reference value of luminous flux is a value comprising a difference between a total luminous flux measurement in the interior space from ambient light and light from the light source and an ambient luminous flux measurement in the interior space with the light source off, with the difference multiplied by a depreciation factor, and wherein if the measurement of luminous flux is less than the reference value, the controller is configured to activate an end-of-life indicator.