A flatbed scanner usually include the following parts:
Charge-coupled device (CCD) array
Mirrors
Scan head
Glass plate
Lamp
Lens
Cover
Filters
Stepper motor
Stabilizer bar
Belt
Power supply
Interface port(s) (i.e. USB, LPT, RJ45, etc.)
Control circuitry
Check out this site: http://computer.howstuffworks.com/scanner.htm
