Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1987-06-25
1989-08-08
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250214B, 340712, 341 24, 341 31, G01V 904
Patent
active
048555908
ABSTRACT:
An input device which can be employed to input commands to a computer directly through a CRT display is disclosed. The input device employs a plurality of infrared light emitting diodes and phototransistors aligned in individual emitter-detector pairs. Infrared beams from the emitter cross the display field before striking the corresponding detector. Emitters and detectors are sequentially activated and each emitter is pulsed or modulated at a frequency different from the variation of ambient conditions during each emitter activation interval. The detection circuitry thus can distinguish the varying emitter signal from ambient or spurious variations. A number of pulses at the pulsed or modulated emitter frequency would be detected unless an opaque element were blocking the particular beam.
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Bures Milan
Kratochvil Paul P.
Rowlette John R.
AMP Incorporated
Pitts Robert W.
Westin Edward P.
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