Abstract: The present invention provides a discharge lamp capable of effectively radiating a light suitable for a photosensitizer used in PDT and PDD, and relates to a discharge lamp which radiates a light suitable for the wavelength region of absorption of a photosensitizer having a relatively large absorption coefficient in the range of wavelength of 600 n-800 nm, and more specifically, the discharge lamp is filled with 0.1 &mgr;mol/cm3 or more of any of the elements selected from the group of lithium (Li), sodium (Na), rubidium (Rb) and potassium (K) as an emitting element, and in addition, at least one or more rare gases selected from the group of neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe) is also filled, and by filling such an emitting element, a light having the wavelength region of the main absorption within the range of the wavelength of 600 nm-800 nm can be radiated.

Abstract: A light source device for a liquid crystal projector in which it is possible to prevent distinct appearance of a shadow of the conducting wiring of a lamp on a screen, even if an integrator lens is used, is achieved according to the invention by the fact that, in a light source device which has a metal halide lamp with bilateral sealed terminations in which seal areas are joined in one piece to two ends of an arc tube, and a concave reflector, in which one of the seal areas of the lamp is installed and held in a base opening of the concave reflector, and in which the other seal area extends in toward the front opening of the concave reflector, by conducting wiring connected to the outer lead pin which projects from the seal area toward the front opening of the concave reflector being positioned running toward the arc tube in a manner resting directly on this seal area, and then being drawn out in the vicinity of the arc tube with to behind the concave reflector.

Abstract: To minimize "color hue" and "flickering" on an irradiated surface such as a screen or the like, is achieved by the fact that, in a metal halide lamp of the short arc type which has a cathode and an anode in which at least rare earth halides and mercury are encapsulated and which is operated with an essentially horizontal discharge direction using direct current power, the cathode has a tungsten electrode shaft about which a tungsten coil is wound, and the relationship 0.029<S/I<0.076 is satisfied where S is the cross section of the electrode shaft (mm.sup.2) and I the current in steady-state luminous operation (A). In accordance with another aspect of the invention, the lamp is operable with a current I (amperes) in steady-state luminous operation in a range from 1.6<I<5.0 and the anode has a tip formed of a roughly cylindrical rod with a bevelled edge between a blunt end of the rod and a peripheral surface of the rod, and with the relationship of the current I and the area S of the blunt end (mm.

Abstract: A metal halide lamp in which rare earth halides are encapsulated and the occurrence of milky cloudiness is suppressed to achieve a prolongation of the service life of the lamp. To achieve this result, inert gas, mercury, indium halide, cesium halide, and rare earth halides are encapsulated in an emission part, with the encapsulation amount of the indium halide being from 0.8 micromole to 8.0 micromole/cm.sup.3 of tube volume, and the lamp is operated with an essentially horizontal arc axis using a direct current. Furthermore, iodine and bromine are contained in the halogen which forms the halides, and there is a ratio of the iodine atom number to the total halogen atom number is greater than or equal to 50%.

Abstract: A metal halide discharge lamp operated from a D.C. power source, which is suitable for an optical light source, has a quartz arc tube. Anode and cathode electrodes are disposed in the arc tube. The gap length between electrodes is so short that the metal halide discharge lamp functions as a point light source. The arc tube contains an inert gas, mercury and metal halide additives including metal bromine. By utilizing the catephoresis effects, the transformation of silica (SiO.sub.2) of the arc tube to cristobalite or the formation of an opaque substance on the arc tube is prevented. Atomic percent of bromine to halogen contained in the arc tube is about 60% to 90% and a wall load developed in the arc tube is substantially greater than 40 W/cm.sup.2.

Abstract: Arc discharged by a short arc discharge lamp can be made so small in diameter as to appear like a spot. Therefore, the illuminance efficiency of the short arc discharge lamp can be made high and its brightness can also be enhanced.

Abstract: A metal halide lamp comprising a luminous sealed tube, a pair of electrodes housed in the luminous tube and rare gas, mercury and metal halide sealed in the luminous tube, characterized in that boron or a boron compound is sealed in the luminous sealed tube in such a manner as not to contact the surfaces of the electrodes. The metal halide lamp is advantageous in that the electrodes are prevented from corrosion and that the blackening with time of the inner wall of the luminous tube is suppressed.