Touch panel with ambient light sampling
First Claim
1. In a touch input device having a panel and means for defining a plurality of beams of radiant energy arranged parallel to the panel, each of said beams being defined by an energy emitter and an energy detector, the improvement comprising sampling means for sampling the ambient output level of one of said detectors immediately prior to the energization of its associated emitter, storage means for temporarily storing a signal representative of said ambient output level, and comparator means for comparing the instantaneous output of said detector with said stored signal during a subsequent interval while said emitter is energized for deriving a signal manifesting the interruption or noninterruption of said beam.
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Abstract
A dynamic level shifter for photoelectric touch panels incorporating a plurality of photoelectric transducers periodically senses the ambient light level, immediately before the interval when each transducer can receive a pulse of radiant energy during normal operation of the panel. The output of the phototransducer during the such interval is compared with the output during the previous ambient interval, to develop a signal indicative of the presence or absence of the pulse, irrespective of ambient light fluctuations.
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Citations
22 Claims
- 1. In a touch input device having a panel and means for defining a plurality of beams of radiant energy arranged parallel to the panel, each of said beams being defined by an energy emitter and an energy detector, the improvement comprising sampling means for sampling the ambient output level of one of said detectors immediately prior to the energization of its associated emitter, storage means for temporarily storing a signal representative of said ambient output level, and comparator means for comparing the instantaneous output of said detector with said stored signal during a subsequent interval while said emitter is energized for deriving a signal manifesting the interruption or noninterruption of said beam.
- 11. In a touch panel having a plurality of pulsed beams of radiant energy traversing the space parallel and adjacent to said touch panel, each beam being defined by an emitter and a detector, the improvement comprising a plurality of comparators, one for each of a set of said detectors, and a plurality of RC networks, one for each of said sets, each of said comparators having one input connected to the output of said set, and another input connected to the output of said RC network, said RC network developing a time weighted integral of the output of its respective set, whereby the output of the comparator manifests the relative level of the output produced by said set in relation to the time weighted integral of said output, and means for sequentially sampling each of said comparators during pulsing of a beam associated therewith.
- 14. For use with a sensing device for periodically sensing the intensity of a radiant beam, apparatus for compensating for the ambient radiation level comprising means for sensing the ambient radiation level immediately before said intensity sensing, means for developing an electrical representation of said ambient radiation level, storage means for storing said representation, and comparing means operative during said intensity sensing for comparing said stored representation with an electrical representation of said intensity.
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22. In a touch input device having a panel and means for defining a plurality of beams of radiant energy arranged parallel to the panel, each of said beams being defined by an energy emitter and an energy detector, the combination comprising means for pulsing said energy emitters sequentially, for causing the energy detectors associated with said energy emitters to produce responsive signals during such pulses, sampling means for sampling the ambient output levels of each of said detectors, immediately prior to the energization of its associated energy emitter, storage means for temporarily storing signals representative of said ambient output levels, said comparator means for comparing the instantaneous output of each of said detectors during said pulses with the stored signal representative of the ambient output level of such detector subsequent to the previous said pulse, said comparator producing a signal in response to said comparison manifesting the interruption or non-interruption of each of said plurality of beams.
Specification