| 摘要 |
PURPOSE:To simplify a manufacturing process and to shorten time by automatically adjusting a gain based on an output from a sensor receiving light reflected by an original. CONSTITUTION:An exposing lamp 2 is turned off, and digital outputs from the ports A4 to A8 of a CPU 8 are changed over to switch a gain to 16 stages via analog switches 8 to 21 of a gain selecting circuit 16. An output related to each gain, obtained as light reflected by an original, and received by an EE sensor 4, is fetched to the CPU 7 and stored therein as black data from the port A2 with the aid of an arithmetic amplifier 8 and voltage dividing resistances R6 and R7. Similarly, when the lamp 2 is turned on, white data is stored, and the difference between the black and white data on each gain is operated. In the increasing order, arithmetic results are compared with an appropriate, upper gain limit, and the gain corresponding to the first data just below the upper gain limit is automatically set. Offsetting is adjusted in a simi lar manner. Consequently, manual adjustment is not needed any more; therefore the manufacturing process of an image density reader is simplified, and the production time is shortened. |
