| 摘要 |
PURPOSE:To permit correct reading of original density by setting time limiting device with the change in the original density when the change in the detected original density arrives at a prescribed number and taking the output signal of a density detecting means via delay circuit within the time limit thereof. CONSTITUTION:Prior to exposure operation of an original image to a photoreceptor, the density of the original is detected by the output of a photoamplifier 1 which is a density detecting means. The output of the amplifier 1 is inputted via a buffer 3 to a delay circuit 4. The output of the buffer 3 is inputted to a counter 13 and time limiting devices 14, 15, and the output of the counter 13 is inputted to a discriminating circuit 16 for count number. The devices 14, 15 are made operatable since the count number of the counter 13 arrives at a preset number N, by which reading of the density information by a pressure plate or the open part of the pressure plate differing from the original and taking in of the same through the circuit 4 are prevented. |
