Canon CANOSCAN D1230 series Service Manual page 34

2. Operation of FARE system
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 2-10-2).
As a solution, D2400U 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
2-10-3).
Finally, the FAU lamp and infrared LED can scan a properly focused film.
CCFL
Light source
Film
Lens
Refraction glass
(FARE Unit)
CCD
Figure 2-10-1
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COPYRIGHT 2001 CANON INC. CANOSCAN D1230U/D2400U REV.0 MAR. 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
IR LED
Figure 2-10-2
CHAPTER 2
IR LED
Figure 2-10-3
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