High contrast ratio paper sensor

Details High contrast ratio paper sensor High contrast ratio paper sensor

1983-01-28

1985-09-10

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250223R, G01N 2186

Patent

active

045408874

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.

REFERENCES:
patent: 3435240 (1969-03-01), Brunton
patent: 3827808 (1974-08-01), Cho
patent: 3882308 (1975-05-01), Daughton et al.
patent: 4092068 (1978-05-01), Lucas et al.
patent: 4217491 (1980-08-01), Dufford et al.
patent: 4352988 (1982-10-01), Ishida

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