| 摘要 |
PURPOSE:To suppress the level fluctuation of a picture signal and to secure a stable picture output by executing the feedback control to a lamp turning-on control part for the light quantity level information of a light source lamp. CONSTITUTION:The photoelectric conversion of light from a light source lamp 1 is executed by an optical sensor 2 and an electric signal (a) is inputted to a light quantity detection part 3. Then, a specified analog level signal (b) corresponding to the quantity of light is outputted. The analog level signal (b) is converted to a digital signal (c) of 4 bits corresponding to the level of the light quantity in an A/D conversion part 4 and inputted to a lamp turning-on control part 5. In correspondence to the digital signal (c), when the quantity of light is small, the lamp turning on control part 5 executes control so that a turning-on voltage can be and a tube current (d) can be increased and reversely, when the quantity of light is large, the control part 5 executes control so that the lamp turning on voltage can be lowered and the tube current (d) can be suppressed. Thus, the quantity of light in the lamp 1 for light source can be always fixed. |
