| 摘要 |
PURPOSE:To prevent occurrence of discontinuation at the juncture of a pattern and improve an accuracy by impressing a predetermined randam noise unto the beginning and termination of the deflective output for deflection and scanning of an electronic beam. CONSTITUTION:An exposure control circuit is made up of an operational amplifier OP, a capacitor C, an integrator INT, an amplifier AMP,analogue switches SW1 and SW2, a flipflop FF and others. There are further an oscillator OSC, an and circuit AND, a counter COUNT, a counter decoder D1 and D2, a noise generator NG and others to cause the noises from the noise generator to be contained into the deflective output in the beginning and termination of the deflective output. When a scanning start pulse is applied to a terminal t, the flipflop FF and integrator INT are operated to initially cause the counter COUNT to count the output from the oscillator OSC. successively, when the predetermined count is obtained, the noise is generated through the decoder D2 from a noise generator NG and after elapse of the predetermined time, the COUNT is cleared with the decoder D1. |
