Abstract: A high-pressure mercury lamp is provided that includes a transparent envelope made of quartz glass, in which mercury, halogen, and a rare gas are sealed and a pair of electrodes provided in the transparent envelope. The amount of the halogen sealed in the transparent envelope is in the range from 1.0×10−6 &mgr;mol/mm3 to 1.0×10−2 &mgr;mol/mm3, and 2.5 mol % to 25 mol % of oxygen with respect to the amount of the halogen is present in the transparent envelope. The high-pressure mercury lamp can prevent blackening of an inner wall of the transparent envelope from occurring over a long period of lighting without deteriorating the startability or lamp characteristics, thus achieving a long life.

Abstract: A high pressure discharge lamp which achieves a long life of at least 3000 hours and in which variations in lamp characteristics are suppressed is disclosed. In the high pressure discharge lamp of the present invention, during manufacturing of an electrode, a covering member 123 having a coil shape and being made of refractory metal is applied on a discharge side end of an electrode rod 122 made of refractory metal so as to cover a circumference of the electrode rod 122 in a vicinity of the discharge side end. The discharge side end 124 on which the covering member 123 is applied is fused into a semi-sphere by intermittently heat fusing the discharge side end according, for instance, to arc discharge or laser irradiation.

Abstract: A short-arc high pressure discharge lamp with a shorter distance between electrodes than a conventional lamp that realizes a long life of at least 3000 hours and suppresses the arc jump phenomenon is disclosed. In the high pressure discharge lamp, an electrode tip 124 is transformed into a semi-sphere by fusing and processing an electrode rod 122 and a coil 123 wound around an end of the electrode rod 122. A thickness “de” and a diameter “&phgr;e” of the semi-sphere are each set in a range predetermined in correspondence with a power input (W) of the short-arc high pressure discharge lamp.

Abstract: A high pressure discharge lamp having a pair of electrodes with a space of 0.5 mm to 2.0 mm inclusive between them and disposed in an arc tube. An electrical discharge takes place between the electrodes. Each of the electrodes has an electrode rod and a head that is provided at the discharge side end of the electrode rod and having a larger diameter than the electrode rod. A surface of the head being opposite to the other electrode is convexly curved and a protruding part is formed in the vicinity of the center portion of the end of the head.

Abstract: A short-arc high-pressure mercury vapor discharge lamp includes a pair of electrodes in an arc tube and encloses mercury, a rare gas, and so forth in the arc tube. The lamp is so constructed as to be operated at a lamp current of, for example, about 1.5 A or higher, or at a lamp voltage/lamp current ratio of about 37.5 (V/A) or lower. In addition, the distance between the electrodes, and the like are set so that the rated power per unit arc length P/d≧88 (W/mm) and the tube wall loading Pw (rated power P/internal surface area of the arc tube)≦1.0 (W/mm2). Thus, a lamp is constructed having, even with a relatively low lamp voltage, a high lamp power of, for example, 125 W or higher, having a short arc length and a high luminous flux per unit arc length, and furthermore being one in which damage to the arc tube does not occur.

Abstract: A short-arc high pressure discharge lamp with a shorter distance between electrodes than a conventional lamp that realizes a long life of at least 3000 hours and suppresses the arc jump phenomenon is disclosed. In the high pressure discharge lamp, an electrode tip 124 is transformed into a semi-sphere by fusing and processing an electrode rod 122 and a coil 123 wound around an end of the electrode rod 122. A thickness “de” and a diameter “Øe” of the semi-sphere are each set in a range predetermined in correspondence with a power input (W) of the short-arc high pressure discharge lamp.

Abstract: A high pressure discharge lamp having a pair of electrodes with a space of 0.5 mm to 2.0 mm inclusive between them and disposed in an arc tube. An electrical discharge takes place between the electrodes. Each of the electrodes has an electrode rod and a head that is provided at the discharge side end of the electrode rod and having a larger diameter than the electrode rod. A surface of the head being opposite to the other electrode is convexly curved and a protruding part is formed in the vicinity of the center portion of the end of the head.

Abstract: A high pressure discharge lamp which achieves a long life of at least 3000 hours and in which variations in lamp characteristics are suppressed is disclosed. In the high pressure discharge lamp of the present invention, during manufacturing of an electrode, a covering member 123 having a coil shape and being made of refractory metal is applied on a discharge side end of an electrode rod 122 made of refractory metal so as to cover a circumference of the electrode rod 122 in a vicinity of the discharge side end. The discharge side end 124 on which the covering member 123 is applied is fused into a semi-sphere by intermittently heat fusing the discharge side end according, for instance, to arc discharge or laser irradiation.

Abstract: A high-pressure mercury vapor discharge lamp comprises an arc tube in which a pair of electrodes are provided and in which a rare gas as a starting gas, a material from which a free halogen is to be produced during a lighting operation, and mercury are enclosed. The arc tube satisfies X/L≧88, in which X(W) is a lighting operation power and L (mm) is a distance between the electrodes. The high-pressure mercury vapor discharge lamp satisfies the following expression: 1.2≦&phgr;/(X×10−2+3.2)≦1.6 in which &phgr; (mm) is the inner diameter of the arc tube. Therefore, the high-pressure mercury vapor discharge lamp has a high luminance, a good emission spectrum, and a long life.

Abstract: The present invention provides a high pressure discharge lamp which is provided with a discharge tube containing a pair of electrodes therein and being filled with mercury, an inert gas and a halogen gas, the amount of the mercury filled being 0.12 to 0.35 mg/mm3, the halogen gas being at least one gas selected from the group consisting of Cl, Br and I and being present in an amount of 10−7 to 10−2 &mgr;mol/mm3, and the electrodes being mainly composed of tungsten, and the tungsten as a material of the electrodes contains not more than 12 ppm of potassium oxide (K2O). In such a high pressure discharge lamp, blackening of the discharge tube due to the potassium oxide (K2O) contained in the tungsten, and decrease in illumination maintenance can be prevented, thus providing a high pressure discharge lamp with a long lifetime, a lighting optical apparatus using the high pressure discharge lamp as a light source, and an image display system using the lighting optical apparatus.