| 摘要 |
It is judged on the basis of the illuminance of the light, emitted from a lamp, which has been measured by an illumination photometer whether or not the exchange of the lamp is required, whereby when the illuminance of the lamp has been reduced due to the blackening of the lamp, the time when exchanging the lamp can be judged before the illuminance of the lamp has become equal to or lower than the necessary illuminance. In addition, it is judged on the basis of the resistance value of the lamp which has been measured by a resistance measuring device whether or not the exchange of the lamp is required, whereby when the illuminance of the lamp has been reduced due to the degradation of the filament, the time when exchanging the lamp can be judged before the illuminance of the lamp has become equal to or lower than the necessary illuminance. As a result, for both of the reduction of the illuminance of the lamp due to the blackening of the lamp and the reduction of the illuminance of the lamp due to the breaking of the filament, the time when exchanging the lamp can be judged before the illuminance of the lamp has become equal to or lower than the necessary illuminance. <IMAGE> |
