Reduction of vertical segregation in a discharge lamp
First Claim
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1. An apparatus for operating a high-intensity discharge lamp, which comprises:
- an amplitude modulator with a first input, a second input and an output coupled to the lamp, means for providing a current to said first input, said current periodically sweeping from a first frequency to a second frequency in a sweep time; and
means for providing to said second input a modulating frequency which excites a longitudinal mode of the lamp wherein metal halides within the lamp are moved along the lamp axially in response to the level of longitudinal mode excitation.
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Abstract
An apparatus for reducing vertical segregation of a discharge lamp. A current/voltage input sweeps through a frequency range between the first azimuthal acoustic resonance mode and a first radial acoustic resonance mode of the discharge lamp. The current/voltage input is subsequently amplitude modulated. Alternatively, without amplitude modulation, the current/voltage input sweeps through the frequency range for a first portion of the period, and then for a second portion of the period drops to a relatively constant frequency.
46 Citations
28 Claims
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1. An apparatus for operating a high-intensity discharge lamp, which comprises:
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an amplitude modulator with a first input, a second input and an output coupled to the lamp, means for providing a current to said first input, said current periodically sweeping from a first frequency to a second frequency in a sweep time; and
means for providing to said second input a modulating frequency which excites a longitudinal mode of the lamp wherein metal halides within the lamp are moved along the lamp axially in response to the level of longitudinal mode excitation. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for operating a high-intensity discharge lamp, which comprises:
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means for providing an input power signal to the high-intensity discharge lamp, and means for varying said input power signal over a period, said period having a first portion and a second portion, wherein the input power signal sweeps from a first frequency to a second frequency during said first portion of said period and wherein said input power signal maintains a substantially constant third frequency during said second portion of said period, and wherein the third frequency excites a longitudinal mode of the lamp and wherein metal halides within the lamp are moved along the lamp axially and vertical segregation of light output from said lamp is reduced in response to the longitudinal mode excitation. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An apparatus for operating a high intensity discharge lamp comprising:
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an amplitude modulator having a first input, a second input and an output coupled to the lamp, means for providing a current to said first input, said current periodically sweeping from a first frequency to a second frequency in a sweep time, and means for providing to said second input an amplitude modulating signal at a modulating frequency which excites a longitudinal acoustic mode of the lamp whereby vertical color segregation in the lamp is reduced in response to said longitudinal acoustic mode excitation. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An apparatus for operating a high intensity discharge lamp comprising:
means for supplying over a time period a varying input power signal to the high intensity discharge lamp without amplitude modulation thereof, said input power signal having a first portion and a second portion of said time period such that the input power signals sweeps from a first frequency to a second frequency during said first portion of said time period and wherein said input power signal maintains a substantially constant third frequency during the second portion of said time period, and wherein the third frequency excites a longitudinal acoustic mode of the lamp whereby vertical segregation of light output from said lamp is reduced in response to the longitudinal acoustic mode excitation. - View Dependent Claims (20, 21, 22)
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23. A method of operating a high intensity discharge lamp, comprising:
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supplying the high intensity discharge lamp with an input power waveform, stabilizing an arc discharge of the lamp by periodically sweeping the frequency of said input power waveform from a first frequency to a second frequency in a sweep time period, and exciting a longitudinal acoustic mode in said lamp. - View Dependent Claims (24, 25, 26, 27, 28)
said longitudinal acoustic mode is excited in the lamp by maintaining the frequency of said input power waveform at a substantially constant third frequency during a second portion of the sweep time period. -
28. The method as claimed in claim 27 wherein said substantially constant third frequency is substantially equal to one half of a power frequency of a longitudinal acoustic mode of the lamp.
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Specification