Abstract: A headlight for a vehicle includes a metal halide lamp and a reflector having a focus and reflecting a light beam, emitted from the lamp, in a forward direction from the front of the vehicle. The lamp has a luminescent tube in which at least sodium is sealed, and positive and negative electrodes. The respective distal ends of the electrodes are located in the luminescent tube and spaced at a predetermined distance from each other. The lamp is positioned so that a straight line connecting the respective distal ends of the electrodes is horizontal and passes through the focus, and so as to meet the following requirement:0.ltoreq.L0/L1.ltoreq.0.4,where L0 is the distance between the focus and the distal end of the negative electrode, and L1 is the distance between the distal ends of the electrodes.

Abstract: A high pressure metal vapor discharge lamp including an outer bulb having a seal portion, an arc tube enclosed within the outer bulb, the arc tube having at least a pair of electrodes and containing at least a light emitting material and a rare gas, a pair of first lead wires of which one ends connect to the electrodes respectively and another ends mounted at the seal portion of outer bulb, a pre-heater disposed within the outer bulb, the pre-heater comprises a heat element and an insulating material covers the heat element and facing the arc tube to give the heat to the arc tube, and a second lead wires connected to the heat element of pre-heater, the portion of the second lead wires which are exposed in the outer bulb are surrounded by a heat-resisting insulator and the base portion of the second lead wires are mounted at the seal portion of outer bulb.

Abstract: A sealed beam type reflective lamp has an envelope comprising a front lens and a reflector on the inner surface of which is formed a metal reflective film, and a tungsten coil filament arranged inside the front lens. The lamp has excellent converging effect and its light beam does not spread even if the filament is brought closer to the front lens. The front lens consists of a central circular lens element and a plurality of concentric ring-shaped prism elements. The inner surfaces of these prism elements define a stepped inner surface of the front lens. An angle formed by an inner surface of the prism lens element and the central axis of the lamp is greater than that of the prism lens element situated outward thereof. The step difference of the inner surfaces of the adjacent prism lens elements is 0.6 mm or less.