Abstract: The invention relates to a high pressure mercury lamp which is operated with an internal pressure at least equal to one hundred and some dozen atm and in which the thermal load and gas convection are considered. A fused silica glass discharge vessel is filled with mercury in an amount at least equal to 0.15 mg/mm3 and rare gas. The length of the electrode which projects into the discharge vessel and which is positioned at the top is greater than the length of the electrode which projects into the discharge vessel and which is positioned at the bottom. Where the lamp wattage is W (W) and the maximum value of the inside diameter in the direction perpendicular to the axis which extends between the pair of electrodes within the discharge vessel is D (mm), the following conditions are met: 0.35×(W)½≦L1≦0.69×(W)½ L2≦0.76×(W){fraction (1/2.64)} and at the same time (2.50)e0.0022W≦D≦(5.0)e0.0034W.

Abstract: A metal halide lamp in which the radiant efficiency is not adversely affected, in which outstanding color reproducibility is obtained, and which is suitable for a light source of an OHP or a direct projector is achieved, according to the invention, by the fact that, within an arc tube provided with a pair of electrodes, together with mercury and a starting rare gas, halides of dysprosium (Dy), yttrium (Y) and cesium (Cs) are encapsulated with the molar ratio of the encapsulated metals Dy to Y is being fixed in the range of 0.3.ltoreq.Dy/Y.ltoreq.1.0. In this way the green portion to which there is a sensitive visual reaction is reduced, the blue portion increased, and thus the color reproducibility is increased.

Abstract: A reflector discharge lamp in which a concave reflector has a front cover and in which a foil seal arrangement of hermetically sealed portions of a discharge lamp mounted therein can be advantageously prevented from reaching a high temperature. This is achieved by the discharge lamp being arranged such that a longitudinal axis of the discharge lamp coincides with the optical axis of the concave reflector by the end area of one of the hermetically sealed portions of the discharge lamp being located in an area of the concave reflector which is opposite the front cover. The end area of the other hermetically sealed portion projecting at least partially through and beyond an aperture in the front cover.

Abstract: A metal halide lamp in which no color shadowing occurs on the light acceptance surface and which at the same time emits with sufficient brightness is achieved according to the invention by encapsulating lutetium halide and one or more of the metal halides from groups A, B and C in an arc tube of a metal halide lamp together with a mercury halide:Group A: dysprosium halide, holmium halide, erbium halide, thulium halideGroup B: cerium halide, praseodymium halide, neodymium halideGroup C: cesium halide.