| 摘要 |
PURPOSE: A discharge lamp is provided to adopt a cathode with a 0.005~0.15 range of an ST/S area ratio where ST is a lateral area of a cathode tip member unit and S is a lateral area of the cathode, thereby reducing the use of the cathode tip member unit. CONSTITUTION: A cathode(5) is comprised of a cathode tip member unit(7) and a main body unit(6). The cathode tip member unit possesses more than 90 percent of a tungsten fill factor. The main body unit is comprised of pure tungsten connected to the cathode tip member unit. A ratio of ST/S is above 0.005 and below 0.15 where ST is a lateral area of the cathode tip member unit and S is a lateral area of the cathode. A lateral area of the cathode S is in a range in which a length between an anode and cathode tip is limited up to twice of a maximum diameter of the cathode.
|
