| 摘要 |
PURPOSE:To use a single sensor to control stably the print density by allowing the read output of each toner color to pass a corresponding correcting circuit to fix the output level and inputting it to a print density control circuit. CONSTITUTION:Amplifying circuits (correcting circuits) 13a-13c only for individual toners which correct levels of ununiform density detection outputs of a toner mark sensor 12, which are different by toner color, to the same level and AND gates (switching circuits) 14a-14c which obtain outputs of the toner mark sensor 12 and print color designating outputs 15a-15c and switch them for each toner to input outputs of the toner mark 12 to specific amplifying circuits are provided. Consequently, the AND gate 14a is operated to input the output of the sensor 12 to the amplifying circuit 13 to correct its level in case the print color designating output 15a indicates red and the toner mark sensor 12 detects a red toner mark 11. The quantity of each replenished toner is controlled by a print density control circuit 16 based on the density detection output of the toner mark sensor 12 whose level is corrected. |
