| 摘要 |
PURPOSE:To achieve smaller size and higher reliability by processing the exposure set signal of digital values in the form of digital values. CONSTITUTION:An A/D converter 12, central processing unit 13 and digital phase control circuit 14 are connected between a density detecting circuit 11 and a lighting circuit 15. As a result of this, the image density detection value of the original is converted to a digital value, after which it is inputted to the central processing unit 13, from which the exposure set signal being digital quantity is outputted to the digital phase control circuit 14 to form the pulses having the time interval corresponding to the exposure set signal. A lighting circuit 15 is triggered by this signal and the effective power to be applied to an exposure lamp 16 is increased or decreased. Hence, the circuit is constituted at low cost and with a small size by using general-purpose integrated circuits; in addition, the reliability becomes higher because it is difficult to receive the effect of drift. |
