4.2. Configuring SANE
4.2.1. SANE Backends
Whether you obtained your distribution's official SANE package, obtained a binary from the SANE homepage or compiled your own SANE binary from source, SANE should identify the appropriate backend to use for your hardware when you call scanimage or any other frontend. If no device is found when you run scanimage -L or your chosen frontend, see Section 7 for more info.
http://tldp.org/HOWTO/Scanner-HOWTO/...eshooting.html (Section 7)