Image reading device, image forming apparatus, and image reading method

An image reading device comprising:

• a reading member that reads an image of a passing document at a read position preset in a document transport path;
• and
• a skew detector that detects a skew of the document by selecting one of a first skew detection mode and a second skew detection mode based on information that specifies a method for detecting the skew of the document,
• the first skew detection mode being a mode in which the skew of the document relative to a transport direction is detected based on an image of a leading-edge section, in the transport direction, read by the reading member,
• the second skew detection mode being a mode in which the skew of the document relative to the transport direction is detected based on an entire image read by the reading member,
• wherein the skew detector detects the skew of the document by switching to the second skew detection mode if reliability of a skew amount detected in the first skew detection mode is determined as being low based on the skew amount and a preset determination amount.

An image reading device comprising:

• a reading member that reads an image of a passing document at a read position preset in a document transport path;
• and
• a skew detector that detects a skew of the document by selecting one of a first skew detection mode and a second skew detection mode based on information that specifies a method for detecting the skew of the document,
• the first skew detection mode being a mode in which the skew of the document relative to a transport direction is detected based on an image of a leading-edge section, in the transport direction, read by the reading member,
• the second skew detection mode being a mode in which the skew of the document relative to the transport direction is detected based on an entire image read by the reading member,
• wherein the skew detector selects the second skew detection mode if the entire image of the document is to be stored into a memory based on a document reading setting.

An image reading device comprising:

• a reading member that reads an image of a passing document at a read position preset in a document transport path;
• a first skew detection mode in which a skew of the document relative to a transport direction is detected based on an image of only a leading-edge section of the passing document in the transport direction;
• a second skew detection mode in which the skew of the document relative to the transport direction is detected based on an entire image read by the reading member;
• and
• a skew detector that detects the skew of the document by selecting one of the first skew detection mode and the second skew detection mode based on information that specifies a method for detecting the skew of the document.