| 摘要 |
PROBLEM TO BE SOLVED: To correctly determine a double-feeding state of a document regardless of an installation environment of a device and a positional relation of a detection means owing to assembly error. SOLUTION: The image reading device includes: an ultrasonic sensor having a transmitting element 6 for transmitting ultrasonic wave to the document to be conveyed and a receiving element 5 for receiving the ultrasonic wave transmitted from the transmitting element 6 and for outputting a receiving value based on the ultrasonic wave received with the receiving element 5; and a CPU 14 for comparing the receiving value and a reference value, determining whether or not the document conveyance state is the double-feeding state in which a plurality of documents are conveyed on top of each other based on the comparison result and changing the reference value under a predetermined condition. COPYRIGHT: (C)2009,JPO&INPIT
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