Patent ID: 7502586

Claim:
An automatic document feeder that sequentially conveys a bundle of originals including at least a preceding original and a next original to be conveyed subsequent to the preceding original and each having a first side and a second side, the feeder comprising: a conveying path for sequentially conveying the originals in a conveying direction from a sheet feeding position, at which conveying of the original stars, to a stacking position, at which the originals are stacked, via a reading position, at which reading is sequentially performed for the originals, the reading position being between the sheet feeding position and the stacking position; a reconveying path that branches from said conveying path at a branching position, between the reading position and the stacking position, and merges with said conveying path at a merging position, between the sheet feeding position and the reading position, for feeding, at the merging position, a respective one of the originals that has passed through the reading position to said conveying path; a controlling unit that controls conveyance of the originals to carry out a first conveyance for sequentially conveying the originals along said conveying path from the sheet feeding position to the branching position to read the first side of each of the originals at the reading position, a second conveyance for conveying a respective one of the originals, for which the first conveyance has been carried out, to the branching position via said reconveying path and said conveying path to read the second side of the respective one original at the reading position, and a non-reading conveyance for conveying the respective one original, for which the second conveyance has been carried out, to the stacking position via said reconveying path and said conveying path, including through the reading position; a selecting unit that selects one of a first mode in which the preceding original is conveyed by the first conveyance, the second conveyance, and the non-reading conveyance, and the first conveyance for the next original is started after the preceding original passes the reading position during the non-reading conveyance, or a second mode in which the preceding original is conveyed by the first conveyance and the second conveyance, and the first conveyance for the next original is started in advance of starting the non-reading conveyance for the preceding original; and an original length detecting unit that detects a length of each of the originals in the conveying direction, wherein said selecting unit selects the first mode to switch over from the second mode to the first mode when a length in the conveying direction of the preceding original being conveyed in the second mode is determined to be equal to or greater than a predetermined length based on a detection result of said original length detecting unit.