| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that conducts optimum density correction even in the case of an image forming device without an original size detection circuit. SOLUTION: When a CCD 3 reads a high density part 301 of an original contact face 601 at the outside of an original area, since an input voltage Va drops almost to a minimum voltage, a position of a discharge resistor 11 is selected by a SW 12 and a reference voltage Vs starts decreasing. Since the CCD 3 reads a low density part 302 of a next pixel, the input voltage Va increases up to almost a maximum value. Since a discharge time constant is set sufficiently long with respect to a scanning time of one pixel, the SW12 is thrown to a position of a charging resistor 10 while the voltage Vs is not almost reduced and the reference voltage Vs starts rising. The reference voltage Vs of a density correction circuit 8 is included within a range between voltages Vs2 and Vs3 that is not almost fluctuated from the initial voltage Vs even at the outside of the original region and the density correction circuit 8 can properly be operated.
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