Ricoh FW830 Service Manual page 32

31 December 1992 EXPOSURE
3.6 AUTO DENSITY SENSOR (ADS)
[B]
[B]
[A]
[A]
Center Line
10mm
18 mm
Sampled Area
33.5 mm
20 mm
The ADS [A] measures the reflectivity of the original's background. Based on
the originals background image density, the CPU automatically adjusts the
development bias and exposure light intensity to achieve a good copy image.
The ADS is located at the original registration rollers. It reads the reflectivity
of the white plate [B] by emitting light from ADS (standard white), which is
located above the ADS, prior to the arrival of the original. This standard white
level (VSD) is used for comparison with the background level of the original
(VOD).
The ADS samples a 43.5 mm by 10 mm area near the leading edge of the
original. As shown in the above illustration, sampling starts 15 mm from the
leading edge.
The highest voltage detected by the ADS is held (peak hold) and used for the
exposure voltage adjustment.
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