Optical paper sensing method and apparatus having light source a

Details Optical paper sensing method and apparatus having light source a Optical paper sensing method and apparatus having light source a

1991-03-21

1993-02-16

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250205, G01N 2186

Patent

active

051873745

ABSTRACT:
A method and apparatus for sensing the presence of a document moved to a printing station in a printer and for detecting skewness (if any) of the document at the printing station. A first light-detector pair and a second light-detector pair are used, with the sensitivity of each of the detectors in the light-detector pairs being adjusted each time the printer is turned on. A controller and a stored program are used to adjust the sensitivity of the detector along with a resistor network providing steps of resistance. The particular resistance step to which a detector is adjusted also gives a measure of the useful life left for the detector.

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