Dirt insensitive optical paper path sensor
US4670647A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 27, 1984 |
| Grant date | Jun 2, 1987 |
| Priority date | — |
| Expiry date | Sep 27, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03G2215/00721
- WIPO fieldHandling
- WIPO sectorMechanical engineering
Abstract
The present invention is concerned with a self-adjusting document sensor compensating for degradation of the sensor system. A suitable light source and a detector are provided, the output of the detector being fed into an amplifier whose gain depends upon a feedback signal. Periodically, the output of the amplifier is compared to a reference. If the output of the amplifier falls below the reference, a pulse is sent to a ripple counter whose digital output is fed back to the amplifier to change the gain of the amplifier. If the detector is an unbiased photodiode operating in the transconductance mode, the leakage currents and their subsequent effect on output with amplifier gain changes will be minimized.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.