| 摘要 |
PROBLEM TO BE SOLVED: To measure an accumulated lighting time in a high luminance discharge lamp, and to determine its deterioration and lifetime. SOLUTION: This luminaire has a discharge lamp 1, a reflector 2, a projecting plate 4, a light detecting part 5, and a control part 6. An opening part 21 to project light radiated in a direction almost perpendicular to the vertical light emitting face of an arc tube 12 onto the projecting plate 4 is formed on the wall surface of the reflector 2. The optical sensor 51 of the light detecting part 5 detects luminous intensity of light projected onto the projecting plate 4 in the almost center part of the arc tube 12, and the optical sensor 52 detects luminous intensity in the lower part of the arc tube 12. The control part 6 calculates a luminous intensity ratio in the almost center part and the lower part of the arc tube 12 to make it as a reference value when a discharge tube 1 is first mounted to the luminaire, and when replacing the discharge lamp 1 and lighting it, measures the accumulated lighting time afterward, and calculates a ratio to the reference value of the luminous intensity ratio for every prescribed time. If the ratio becomes not less than a prescribed threshold, 0.8 for instance, the discharge lamp 1 is determined to have expiration of its lifetime. COPYRIGHT: (C)2009,JPO&INPIT |
