How Is The Dust Detected? - Ricoh B132 Service Manual

SCANNER UNIT

How is the Dust Detected?

To detect dust on the ARDF exposure glass, the ARDF transport belt turns and the
CCD scans this belt.
The ARDF transport belt has four grooves cut across it in the main scan direction.
These grooves are recessed. Because of this, they are not easily contaminated
with dust, and they are used as reference points during dust detection. Another
part of the belt could have dust on it, and give an incorrect reference.
NOTE: The illustration shows the belt if it were a perfect circle.
4 mm
34 mm
Belt Circumference: 136 mm
B132D976.WMF
To detect dust, the belt turns one time. The IPU (through the CCD) checks for dust.
If a dark spot is detected for 96% of this rotation, the IPU determines that dust is
present on the ARDF exposure glass.
B132/B200 6-38 SM