Patent ID: 7557524

Claim:
An illumination lighting device comprising a plurality of illumination groups, each of said illumination groups containing one or more light emitting diodes and being configured for passing between an energized light emitting state and a non-energized state, and control means for maintaining the luminosity of the lighting device at a desired level, said luminosity being controlled by, at predetermined time intervals, transferring an appropriate number of illumination groups between said energized light emitting state and said non-energized state, whereby said transfer is effected in response to a luminosity reading and/or a usage time measurement, and said lighting device comprises at least one of usage time measuring means for providing a usage time measurement for each of said illumination groups at predetermined time intervals, and a luminosity measuring system comprising i) luminosity measuring means, ii) one or more test light emitting diodes equivalent to the light emitting diodes of said plurality of illumination groups, said luminosity measuring means being able to provide said luminosity reading at predetermined time intervals, on the basis of the light of said one or more test light emitting diodes when said one or more test light emitting diodes are in an energized state, wherein said one or more test light emitting diodes are selected from among light emitting diodes which are part of said illumination groups and which are separate from said illumination groups.