Scanner sensors

A document scanner uses two kinds of sensors: the image sensor that captures each page, and the paper sensors that track each sheet through the feeder. When a paper sensor is dirty or faulty, the scanner reports jams, double feeds or an empty tray that aren't really there.

Image sensors: CIS and CCD

• CIS (contact image sensor) is a row of sensors that sits right against the glass, lit by LEDs. It is compact and energy-efficient, and most current desktop document scanners use it.
• CCD (charge-coupled device) uses mirrors and a lens to focus the page onto a small sensor. It has more depth of field, so it handles creased pages and bound books well, and it is common in flatbeds and some production scanners.

Paper sensors

• Paper-present and empty sensors detect whether there is paper in the tray and when the stack runs out.
• Feed and jam sensors track each page along the paper path and stop the scanner if a page doesn't arrive on time.
• Ultrasonic double-feed sensors detect two sheets stuck together by how ultrasound passes through the paper, so no page is skipped unseen.

Sensor problems

Paper dust on a sensor is the most common cause of false errors, so clean the sensors first, following your scanner's manual; see cleaning supplies. If the errors continue, the sensor may need replacing. We carry replacement sensors for selected Kodak, Fujitsu and Canon models among our spare parts. Send us your model and the error you see, and we'll help you find the right part.

See also the parts of a document scanner.