Abstract: Metal halide vapor arc lamps for reprographic and projection processes emitting in the blue, green and red bands with excellent primary color separation and having significant blue emission at a wavelength of about 450 nm, contain a fill of indium, zinc, lithium and thallium iodides.

Abstract: A high intensity metal halide discharge lamp has a fill comprising mercury, sodium iodide and scandium triiodide plus an inert starting gas. Cadmium or zinc may be added in a molar ratio relative to ScI.sub.3 within the range of 0.04 to 1.0 to achieve a lowering in color temperature of several hundred degrees Kelvin at the cost of a minor decrease in lumens which is offset by an improvement in maintenance.

Abstract: An electrode for a miniature high pressure metal halide lamp having a volume not exceeding 1 cc and a discharge current not exceeding 1 ampere comprises a slender tungsten shank with a few secondary turns of mandrel-less coiled-coil overwind thereon and preferably a balled distal end. The shank diameter is chosen in the range of 5 to 15 mils and above the size where melt-back starts at the intended lamp current, and the overwind is made of primary wire not exceeding 3 mils originally wound on a primary mandrel of 3 to 7 mils subsequently removed. This assures a rapid glow-to-arc transition which provides good maintenance and also reduces ballast requirements.

Abstract: High pressure discharge lamps containing a fill of mercury and metal halides, having a power input of 250 watts or below and useable for general illuminating purposes achieve higher efficacy by developing high end temperatures without excessively obstructing the transmission of light and without creating excessive thermal losses through radiation and conduction. To reduce the obstruction of light, heat-conserving coatings on the lamp ends are preferably omitted and small neck seals are used which serve also to reduce thermal losses. The lamps are constructed with an aspect ratio of arc chamber length to diameter from 0.9 to 2.5 and with an electrode insertion factor from 0.1 to 0.6 and operate with a wall loading from 10 to 35 watts/cm.sup.2 and with an arc loading from 60 to 150 watts/cm.

Abstract: In a discharge lamp where the arc tube has main electrodes and a starter electrode, there is provided a voltage doubling circuit comprising a diode and a capacitor connected in series across the input terminals. The circuit is poled to generate a positive potential at the junction of diode and capacitor which is coupled through a resistor to the starter electrode. Voltage doubling may be provided across the gap from starter to adjacent main electrode or from starter to remote main electrode to improve starting. Where the arc tube contains sodium, the positive potential may also be applied to the arc tube frame to reduce sodium loss by electrolysis.

Abstract: A jacketed high intensity discharge lamp utilizes a starter electrode voltage doubling circuit comprising a diode and a mica-dielectric capacitor which is electrically interposed between an inlead into the jacket and the frame side rod and forms an integral structural part of the frame which supports the arc tube. The starter electrode is resistively connected to the side rod to facilitate starting and the arrangement maintains a positive D.C. bias on the frame which reduces electrolysis of sodium through the arc tube walls.