U.S. Philips Corporation

Levinus P Bakker

Gerardus M W Kroesen

The invention relates to a method of adjusting a desired spectrum of light emitted by a gas discharge lamp during its operation, said gas discharge lamp comprising a first ionizable substance and a second substance which is less readily ionizable than the first substance. According to the invention, the gas discharge lamp is operated such that gases of both substances cans be excited, while the partial pressure of the first substance is adjusted in dependence on the desired spectrum. For this purpose, for example, the current through the lamp may be modulated. In an alternative embodiment, this is suitably achieved in that the partial mercury pressure is varied, for example through an adjustment of the temperature of a mercury amalgam present in the gas discharge lamp. The invention also relates to a gas discharge lamp whose color can be varied during its operation, and to a luminaire provided with a supply for such a lamp.

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Utrecht, Netherlands

Levinus P Bakker