Canon CR-55 - Manual (Page 50)

46 Regular Maintenance
Cleaning the Sensor Glass and the Rollers
If the scanned images have extraneous marks, or if the scanned documents
become dirty after scanning, then the sensor glass or rollers inside the scanner
may be dirty. Clean them periodically.
1
Hook your finger around the open lever and open the maintenance cover.
2
While lowering the open lever, open the reading unit.