Patent ID: 7753365

Claim:
An image scanning apparatus comprising: a document tray arranged to receive a plurality of documents; an image scanning unit arranged to scan the documents; a transfer unit arranged to transfer the documents on the document tray one by one toward the image scanning unit; a lifting and lowering device arranged to lift and lower the document tray; a height detection sensor arranged to detect an upper surface height of the documents stacked on the document tray; and a control unit arranged to control the lifting and lowering device; wherein the control unit controls the lifting and lowering device while switching between a first control mode and a second control mode in which a document scanning speed of the second control mode is faster than that of the first control mode; and when the height detection sensor detects that the upper surface height becomes lower than a predetermined height due to a transfer of the document by the transfer unit: in the first control mode, until the upper surface height reaches a target height that is higher by a predetermined distance than when the height detection sensor detects that the upper surface height becomes higher than the predetermined height, the control unit elevates the document tray at predetermined pitches each time the one document is transferred during an inter-transfer time between completion of the document transfer and start of a subsequent document transfer; and in the second control mode, until the upper surface height reaches a height that is higher by a predetermined distance than a height at a time when the height detection sensor detects that the upper surface height becomes higher than the predetermined height, the control unit elevates the document tray at predetermined pitches during the inter-transfer time each time the one document is transferred.