| 摘要 |
Provided is a label detector which detects a label mark on a sheet surely even if the quantity of light passed through the sheet or reflected off the sheet varies according to the kinds of sheet or the presence/absence of a printed label. The label detector comprises a conveyance means for conveying a sheet having a label mark, a detection means for detecting a sensor value of the label mark on a sheet conveyed by the conveyance means, a storage means for storing the sensor value acquired by the detection means at every stepped drive of the conveyance means, a means for judging the start of measurement of the label mark by determining the difference between two positions, one for the sensor value stored by the storage means and the other for the sensor value acquired by the detection means, and a label mark judgment means for judging the intermediate position or the end position of the label mark by determining the difference between two positions, one for the sensor value stored by the storage means and the other for the sensor value acquired by the detection means after a judgment is made that measurement of the label mark has been started by the means for judging the start of measurement of the label mark.
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