Abstract: In a light source, a heat sink is in contact with a side-on type discharge tube 110. The heat sink is in contact with a peripheral region 110ws around an exit window 101ww of the discharge tube 110. The heat sink consists of a spring member 101sp kept in direct contact with the peripheral region 101ws, and a radiating block 101bl which connects the spring member 101sp to a radiator box 101bx. Since materials made by sputtering or the like of electrodes in the discharge tube 110 mostly attach to the peripheral region 101ws of side wall 101w, it is feasible to decrease the amount of materials attaching to the exit window 101ww and, in turn, lengthen the lifetime of the discharge tube. Another light source may be constructed in structure in which the heat sink is in contact with a head-on type discharge tube or in structure in which light is outputted from a projecting portion.

Abstract: In a light source, a heat sink is in contact with a side-on type discharge tube 110. The heat sink is in contact with a peripheral region 110ws around an exit window 101ww of the discharge tube 110. The heat sink consists of a spring member 101sp kept in direct contact with the peripheral region 101ws, and a radiating block 101bl which connects the spring member 101sp to a radiator box 101bx. Since materials made by sputtering or the like of electrodes in the discharge tube 110 mostly attach to the peripheral region 101ws of side wall 101w, it is feasible to decrease the amount of materials attaching to the exit window 101ww and, in turn, lengthen the lifetime of the discharge tube. Another light source may be constructed in structure in which the heat sink is in contact with a head-on type discharge tube or in structure in which light is outputted from a projecting portion.

Abstract: A discharge tube is comprised of a glass bulb, a cathode, and an anode. Impregnating porous tungsten with barium makes the cathode tip portion. A clearance between the end face of a lead rod and the end face of the cathode tip portion is filled with a molybdenum-ruthenium brazing filler metal.

Abstract: A discharge tube in which a cathode with a cathode tip portion being fixed to a lead rod and an anode opposed to the cathode tip portion are encapsulated in a discharge gas atmosphere to effect arc discharge, wherein the cathode tip portion comprises: a metal substrate of an impregnated type in which a porous, refractory metal is impregnated with an electron-emissive material or a sintered type in which a refractory metal containing an electron-emissive material is sintered; and a coating of a refractory metal covering a predetermined portion in a surface of the metal substrate and having a thickness of not less than 0.02 &mgr;m nor more than 5 &mgr;m, wherein the metal substrate has a cusp pointed toward the anode, and wherein a tip portion of the cusp of the metal substrate is exposed without being covered by the coating.

Abstract: In order to meet various requirements for discharge tubes for use as light sources, including easiness of production, stability of discharge, long lifetime, etc. without any contradiction between them, a discharge tube of the present invention involves an improvement in the discharge tube for use as a light source constructed to effect arc discharge in a discharge gas atmosphere between a cathode 2, having a cathode tip portion 22 fixed to a lead rod 21, and an anode 3 opposed thereto while keeping the cathode and anode enclosed in the gas. The cathode tip portion has a cusp pointed toward the anode and consists of a refractory metal substrate 221 of an impregnated type or a sintered type containing an electron-emissive material, and a refractory metal coating 222 covering the surface except at the tip portion of the cusp.

Abstract: A discharge tube in which a cathode with a cathode tip portion being fixed to a lead rod and an anode opposed to the cathode tip portion are encapsulated in a discharge gas atmosphere to effect arc discharge, wherein the cathode tip portion comprises: a metal substrate of an impregnated type in which a porous, refractory metal is impregnated with an electron-emissive material or a sintered type in which a refractory metal containing an electron-emissive material is sintered; and a coating of a refractory metal covering a predetermined portion in a surface of the metal substrate and having a thickness of not less than 0.02 &mgr;m nor more than 5 &mgr;m, wherein the metal substrate has a cusp pointed toward the anode, and wherein a tip portion of the cusp of the metal substrate is exposed without being covered by the coating.

Abstract: A discharge tube is comprised of a glass bulb, a cathode, and an anode. Impregnating porous tungsten with barium makes the cathode tip portion. A clearance between the end face of a lead rod and the end face of the cathode tip portion is filled with a molybdenum-ruthenium brazing filler metal.

Abstract: A discharge tube is comprised of a glass bulb, a cathode, and an anode. The cathode consists of a cathode tip portion of a bullet shape made by impregnating porous tungsten with barium, and a cylindrical lead rod of molybdenum having a recess. Apart of a base of the cathode tip portion is placed in the recess of the lead rod and a clearance between the internal surface of the recess of the lead rod and the side face of the insert part of the cathode tip portion is sealed with a molybdenum-ruthenium brazing filler metal.