| 摘要 |
PURPOSE:To obtain binarized processing data without receiving any influences from dust, etc., even when the dust, etc., sticks to a sheet member, by previously providing a black correction line at a part of the white part between the two effective reading areas of the sheet member. CONSTITUTION:A correction line 20 is previously written as black waveform information in a part of a white section 11 between the two effective reading areas 6 and 6' of a sheet member 1. When the white section 11 containing the line 20 is read by an image sensor, an abnormal white waveform is obtained due to the black waveform of the correction line 20. Then the actual picture information in the area 6 or 6' is read by the image sensor and auto shading correction is performed by performing a division process on the results obtained by reading the white section 11 and actual picture information in the area 6 or 6'. In accordance with the results of the division process, the threshold level is set at a level lower than conventional practices and binary coded. By setting the threshold level by taking the reference waveform of the white waveform including the line 20 provided by setting a condition equivalent to a condition where dust sticks to the sheet member 1 in such way, binarized processing data can be obtained without receiving any influences from dust, etc., even when the dust, etc., sticks to the sheet member 1.
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