Automatic document feeder having a document shunting path

An automatic document feeder comprising:

• a document feeding portion for feeding a document placed thereon, wherein the document is fed in order of a leading edge and a rear edge of the document in said document feeding portion;
• a document reading portion for reading the document;
• a document discharging portion;
• a document conveyance path connecting said document feeding portion, said document reading portion and said document discharging portion;
• a conveying roller, which is capable of forwardly rotating and reversely rotating, for conveying the document along said document conveyance path;
• a document shunting path branched from said document conveyance path between the document feeding portion and the document reading portion;
• a first detector for detecting at least one of the leading edge and the rear edge of the document;
• and
• a second detector which is disposed in said document conveyance path between said first detector and said document reading portion for detecting the leading edge of the document,
• wherein said conveying roller is forwardly rotated to convey the document with the leading edge thereof headed, and, after the rear edge of the document is detected by said first detector, said conveying roller is reversely rotated to move the rear edge of the document into said document shunting path, until the leading edge of the document is moved back to a position on an upstream side of said document reading portion, to thereby convey the document in a forward direction and a reverse direction on the upstream side of said document reading portion, and the document is again conveyed in the forward direction toward the the upstream side of said document reading portion, and the document is again conveyed in the forward direction toward the document reading portion so as to read the document based on a detection signal at a time that said second detector has detected the leading edge of the document during conveyance of the document in the reverse direction, and
• wherein, in a case that said second detector has already detected the leading edge of the document before said first detector detects the rear edge of the document while the document is fed from said document feeding portion, the document is conveyed in the reverse direction so as to be fed to the document shunting path.