SprintScan 35LE Service Manual
Functional Description
5
As shown in Figure 1-2, light from the lamp passes through the slide onto the surface of the
CCD, which generates electrical signals proportional to the intensity of the light. The CCD
is operated so that the magnitude of the electrical signal is linearly proportional to the
intensity of received light. Since the CCD scans one line at a time, a stepping motor is
used to move the slide so the CCD can scan the entire slide.
Analog-to-Digital Converter
Output from the CCD is fed to this module, and most of the scanned-data processing is
done in this stage. The waveform output by the CCD is shown in Figure 1-3, where the
magnitude of the output signal with respect to the bias voltage is a function of the intensity
of the light incident upon the CCD.
Figure 1-3. CCD output waveform
Since output-signal bias voltage varies for different CCDs, and output notches degrade
system response, the output-signal bias voltage is first restored to ground, and then a
sample-and-hold operation is carried out to eliminate output notches. The resultant
waveform is shown in Figure 1-4.
Figure 1-4. CCD output signal after bias restored
Output Notch
Valid Data
Vbias
Vaild Data
Vbias = Ground
