High contrast ratio paper sensor
US4540887A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 28, 1983 |
| Grant date | Sep 10, 1985 |
| Priority date | — |
| Expiry date | Jan 28, 2003 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB41J11/009
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A high contrast ratio sensor is provided by introducing a pair of photodetectors into the sensor circuitry. One of the detectors is a diffuse detector and the other is either a reflective or transmittance detector. The two photodetectors are connected in a manner to cause the diffuse detector output to subtract from the reflective (or transmissive) detector output. This subtraction of signals provides a high contrast ratio. In a first embodiment, a diffuse detector and a reflectance detector are located on the same side of the paper as the emitter light and in a second embodiment a diffuse detector and a transmittance detector are located on opposite sides of the paper to be sensed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.