DIMMING DEVICE FOR EXPOSING LAMP

摘要

PURPOSE:To attain stable dimming of an exposing lamp by controlling the conducting angle of a thyristor by a trigger pulse generated in accordance with a value obtained by dividing a difference value between specific data read out from a table and digital data obtained from a conversion means by a prescribed value every prescribed time. CONSTITUTION:Light radiated from the exposing lamp 4 is detected and transmitted by a glass fiber 4 and then detected by a photodiode 61 arranged on a position separated from the lamp 4 and the detected light is converted into a current value. The optical current generated from the photodiode 61 is converted into a voltage value by a current/voltage conversion circuit 62, amplified by an amplifier 64 and sent to an A/D converter 65 and the converted digital data are sent to a microcomputer 31. The mirocomputer 31 actuates a timer function included in itself in accordance with the value obtained by dividing the difference value between the level of the input data and the level of reference data corresponding to te setting of exposuer by '2' (H). Consequently, a trigger pulse is generated and the conducting angle of the thyristor 22 is controlled by the trigger pulse to control a voltage impressed to both the ends of the exposure lamp 4.