Canon Canoscan CS8000F Service Manual page 26

CHAPTER 2
2. Operation of FARE Function
The frequency of the FAU lamp (cold cathode fluorescent lamp) is 380-700nm, while that of
the infrared LED is 880nm, therefore, their light refractive indexes differ resulting in out of
focus (Figure 2-9-2).
As a solution, CanoScan 8000F employs FARE unit between the CCD and lens, which
consists of a refraction glass for changing the light refractive index and of an electromagnetic
switch for changing the position of the refraction glass.
Firstly, the FAU lamp scans a film passing through the refraction glass. Secondly, the
infrared LED scans a film, at the same time, the electromagnetic switch is turned ON to move
the refraction glass to the position where the infrared LED light does not pass through (Figure
2-9-3).
Finally, the FAU lamp and infrared LED can scan a properly focused film.
FAU Lamp
Light Source
Film
Lens
Refraction Glass
(FARE Unit)
CCD
Figure 2-9-1
2 - 10 
COPYRIGHT 2002 CANON INC. CANOSCAN 8000F REV.0 OCT. 2002 PRINTED IN JAPAN (IMPRIME AU JAPON)
IR LED
Figure 2-9-2
IR LED
Figure 2-9-3