| 摘要 |
PURPOSE:To improve the correction of shading distortion even just after the lighting of a light source by changing over the lower limit of the correcting range of shading distortion into >=2 stages in a reader used for a facsimile device. CONSTITUTION:A voltage Vr is set so that the relation of voltage Vp proportional to a peak value < reference voltage Vr is obtained when a peak value of a pictue signal is less than a threshold value lower than the peak value at steady-state value at normal temperature and the relation of Vp>=Vr when the peak value exceeds the threshold value, the lower limit value of the correcting range is changed over to C1 just after lighting and to C2 after the lighting. When the calculation and storage of the correcting coefficient is finished, an original 2 is fed in front of a white reference plate 1 and scanned by a CCD image sensor 4, and an original picture signal and the correcting coefficient read from a memory 10 are multiplied. Since the correcting coefficient of the correcting range with the low lower limit value C1 just after the lighting of a fluorescent light 3 and that of a high lower limit value C2 at steady-state at normal temperature are outputted respectively from the memory 10, a picture signal applied with proper correction for shading distortion at all times is outputted from a multiplier 9. |
