| 摘要 |
PURPOSE:To prevent previously the deterioration of picture data owing to the deterioration in a light quantity, by detecting directly the light quantity of a light source like a fluorescent lamp, etc. and giving an alarm when the light quantity of the light source is less than a prescribed level or the light quantity difference between at least two points of the light source is less than a prescribed level. CONSTITUTION:When a fluorescent lamp 1 is new and working normally, the light quantity difference is small between the center part and the discharging end part of the lamp 1. Thus the signal of an L level is delivered from a comparator 13 and a light emitting diode 15a emits no light. While the blackening degree of the discharging end part owing to the secular change of the lamp 1 and the light quantity difference between the center part and the end part exceeds a standard level (standard signal Vr). Thus the signal of an H level is delivered from the comparator 13. Then the diode 15a emits the light to warn the deterioration of the lamp 1. This can prevent previously the uneven picture quality due to the deterioration of the light quantity. |
