| 摘要 |
PURPOSE:To prevent the largely variance of a reading signal level and the difference at a reading image with reading speed by controlling the light quantity of the light emitting diode group of plural blocks used as a light source based upon reading speed changing-over command given from an external device. CONSTITUTION:A main control part receiving a reading speed changing-over command beforehand from an external device makes a clock changing-over signal (a) into Low, for example, to make an action into a low speed mode, and selects the output of a clock generating circuit 22 generating a low speed clock by a clock changing-over circuit 23. Simultaneously, a lighting-up signal (c) is made into High and a lighting-up signal (d) is made into Low. Next, a lighting-up signal (b) is made into High, and then, the output of a gate G11 comes to be High, a transistor TR12 is turned on through a transistor TR11 and fixing resistances R11 and R12 and a light emitting diode D1 lights up. On the other hand, since the output of a gate G21 comes to be Low, a transistor TR21 and a transistor TR22 are turned off and a light emitting diode D2 does not light up. At the time of a high speed mode, for the main control part, both D1 and D2 light up by making both the lighting-up signal (c) and the lighting-up signal (d) into High.
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