Sheet feeder and document scanner having ejection detecting sensor

A document scanning device configured to scan document sheets, comprising a document feeder configured to feed the document sheets to be scanned,

• wherein the document feeder comprises:
• a feed tray configured to receive the document sheets to be scanned;
• a catch tray configured to receive the document sheets ejected thereon;
• a feeding mechanism configured to convey the document sheets from the feed tray to the catch tray;
• an ejection mode switching mechanism configured to switch an ejection mode between a first mode and a second mode, the feeding mechanism ejecting, in the first mode, the document sheets sequentially on a stack of document sheets already ejected on the catch tray, the feeding mechanism ejecting, in the second mode, the document sheets sequentially under a stack of document sheets already ejected on the catch tray;
• an ejection detecting sensor configured to detect a document sheet ejected on the catch tray;
• and
• a controller configured to control the feeding mechanism,
• wherein the controller is configured to, in response to an instruction issued to start feeding the document sheets, forbid driving of the feeding mechanism when determining that the ejection mode is set to the second mode and determining based on a detection result of the ejection detecting sensor that there is a document sheet on the catch tray.