Westinghouse Electric Corporation

Edward Chen

William A Thornton

Edward W Morton

Daniel A Larson

Dorothy Rachko

High-intensity-discharge lamp of the mercury-metal halide type efficiently illuminates objects with excellent color appearance. The arc tube filling comprises the usual inert, ionizable starting gas and mercury in predetermined amount as required to provide a predetermined operating voltage drop between the lamp electrodes. The metal halide filling substantially comprises a predetermined limited amount of thallous iodide, a predetermined limited amount of stannous iodide and a predetermined limited amount of calcium iodide. The stannous iodide is used in such amount that it serves primarily to enhance the emission of the calcium iodiode and the amount of stannous iodide is sufficiently limited to curtail the generation of the characteristic continuous tin emission. The calcium iodide is present in greater gram amount than the tin iodide so that the effects of the calcium iodide emission are predominant. The resulting discharge has its emission concentrated in three selected wavelength portions of the visible spectrum, namely, blue violet which is due primarily to the calcium iodide emission, green which is due to the thallium iodide emission, and red which is due to the tin-iodide-enhanced calcium iodide emission. The efficiency of the composite discharge is good and the color appearance of illuminated objects is excellent.

High-intensity-discharge lamp of the mercury-metal halide type which

Method and apparatus for expressing as a number the relative brightness of artificial illumination as it is perceived by the average observer. There is extracted (i.e., detected) from the illumination to be measured, a blue-appearing narrow band, a green-appearing narrow band, a yellow-appearing narrow band and a red-orange-appearing narrow band. From these extracted bands are generated six different signals: a signal expressed as (aB) where (a) is about 0.23 and (B) is the watts of energy in the blue band, a signal expressed as (bG) where (b) is about 0.97 and (G) is the watts of energy in the green band, a signal expressed as (cR) where (c) is about 0.33 and (R) is the watts of energy in the red-orange band, a signal expressed as (dY) where (d) is about 0.19 and (Y) is the watts of energy in the yellow band, a signal expressed as (eG) where (e) is about 0.25 and (G) is the watts of energy in the green band, and a signal expressed as (fR) where (f) is about 0.25 and (R) is the watts of energy in the red-orange band. These signals are combined in the following manner: aB+bG+cR-dY+(the larger of eG and fR minus the smaller of eG and fR). These combined signals are expressed as a number which is indicative of the relative brightness of artificial illumination as perceived by the average observer.

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Glen Rock, NJ, United States of America

Edward Chen