| 摘要 |
At least one sheet of paper is conveyed in a feeding direction along a conveyance path. A line perpendicular to the feeding direction of the conveyed sheet includes at least first and second distinct view field regions (lengths) separated from one another by the center of the path. The light directed toward the sheet which passes across the path along the perpendicular line is optically scanned, and a value of the dimension a conveyed sheet projects into each of the first and second view field regions is produced for each scan. The sheet is repetitively scanned a plurality of times as it is conveyed along the path, and the values obtained, for each scan, for at least for the first and second regions are summed with a predetermined constant value to produce a sequence of width values representing the widths of the conveyed paper sheet at a corresponding plurality of longitudinal positions along the sheet. The width values from the sequence which fall within a range about a predetermined nominal width value of the sheet (the range being this nominal width value plus or minus a preset allowable deviation) are selected and used for computing the average width value of the sheet. The average width value is compared with a reference width value. Document skew, dog-ear, puncture and other parameters may also be determined from the measured width values.
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