Low pressure sodium-mercury lamp yielding substantially white light
AssigneeMatsushita Electric Works R&D Laboratory, Inc.
InventorsJakob Maya, Jagannathan Ravi
Life of this patent
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Abstract
Low pressure sodium lamp color output is shifted from yellow to a fuller spectral range of visible light (white) by effective simultaneous excitation of sodium and a mercury additive. This is made possible principally by controlling the vapor constituents and the excitation arrangement.
Claims18
A low-pressure sodium lamp comprising:
- (1) arc-containing enclosure means;
- (2) sodium metal, mercury metal, and a rare gas within the enclosure, the sodium composition in the amalgam comprising at most 20 percent by weight with the rare gas pressure from 0.1 to 30 Torr, and
- (3) means for exciting the mixture in a manner to produce an arc with a cold spot temperature from about 100.degree. C. to about 400.degree. C. and with excitation of the resonant and upper states of Na and Hg in the arc,
- whereby a substantially white color output is obtainable from the lamp;
- and wherein said means for excitation are selected from the group of excitation means consisting of (a) alternating current (CW);
- (b) pulse train of any waveshape with rise times in the range of 10.sup.-8 to 10.sup.-5 microseconds;
- (c) pulse burst of duty cycle greater than 5%;
- (d) direct current;
- (e) combination of the foregoing;
- and (f) individual ones or combinations of the foregoing controlled to maintain a minimal discharge (simmer) normally which can be raised to an operational illuminating state;
- and further comprising means for changing the color temperature of the lamp by varying one or both of excitation waveform and cold spot temperatures thereof.
A sodium lamp with controlled or controllable emission of light of a spectral output including white, with a color temperature in the range of 2,000.degree. to 6,000.degree. K., comprising:
- (a) means defining an arc region of low pressure rare gas (30 Torr or less) with a source of vaporizable sodium and mercury material therein,
- (b) means for striking and maintaining an arc discharge of a gas mixture of vaporized sodium and mercury and of the rare gas in the arc region,
- the foregoing sodium-mercury composition and the excitation means constructed and arranged to cause both sodium and mercury atoms to give off radiation by resonant and upper states excitation, the electron energy distribution function of the arc discharge being such that such higher level excitation is substantial while maintaining a cold spot temperature in the arc discharge region in a range of from 100.degree. to 400.degree. C. thus limiting sodium vapor generation in relation to mercury vapor generation.
Method of generating a composite visible light range radiation in the color temperature range from 2,000.degree. to 6,000.degree. K. by establishing a vapor mixture of gasses including two gasses that are excitable in a low pressure arc to states of energy emission at wavelengths that are spread apart, but which average to an apparent color emission known as white light and establishing and maintaining such an arc discharge therein with a cold spot temperature of 100.degree. to 400.degree. C. and with an electron energy distribution function such that those excited states are realized.
Dependencies are inferred from the claim text.