| 摘要 |
PURPOSE:To evade a fault such as an illumination accident during operation by providing a lighting device with a fault detecting device for taking an initial diagnosis and a normal diagnosis and also providing a power varying focusing device with another fault detecting device for taking the normal diagnosis. CONSTITUTION:It is judged whether a voltage current applied to a main lamp LM is normal or abnormal and when the current is abnormal, it is judged whether the abnormality continues for longer than a constant time or not to decide that a turn-on circuit 23M is abnormal when so, thereby making an LED 20M on a display panel 12 illuminate. Further, if only the lamp current is abnormal, it is decided that the main lamp LM has burned and an LED 21M of the display panel 12 is made to illuminate. Even if a current pulse flowing through the lamp falls to low level temporarily and an abnormality flag is detected, a self-diagnostic circuit does not detect the abnormality unless a pulse signal for decision making continues 15 times. Therefore, if a fault occurs during use, the fault position can be known by checking the display panel. |
