초록 ▼

A touch input device having infrared light beams defined by a plurality of pairs of light emitters and phototransistors is disclosed. A feedback loop containing a programmable amplifier is employed to compensate for the effects of ambient light and for device irregularities. The phototransistor curr

A touch input device having infrared light beams defined by a plurality of pairs of light emitters and phototransistors is disclosed. A feedback loop containing a programmable amplifier is employed to compensate for the effects of ambient light and for device irregularities. The phototransistor current is first converted to a signal voltage by an operational amplifier and then is input into a low pass filter. The output of the lowpass filter is input into a feedback loop containing a summing amplifier, a programmable amplifier and an integrator. As light emitters and phototransistors are sequentially activated, the feedback loop with the programmable amplifier compares outputs signals in the unactivated state with those input when the light emitters are activated to compensate for ambient conditions and errors.

대표청구항 ▼

A touch input device for use with a visual display, comprising: a plurality of paris of light emitters and light detectors forming light beams spanning the visual display; means for intermittently activating corresponding emitters and detectors forming individual light beams; and means for detecting

A touch input device for use with a visual display, comprising: a plurality of paris of light emitters and light detectors forming light beams spanning the visual display; means for intermittently activating corresponding emitters and detectors forming individual light beams; and means for detecting the interruption of individual light beams, further comprising a feedback loop containing a programmable amplifier, a summing amplifier and an integrator, the programmable amplifier having a unique amplification ratio for each detector and being sequentially responsive to signals detected by each detector during a time interval greater than the time during which the corresponding emitter is activated, output from the programmable amplifier establishing a constant reference level independent of signals output by an activated detector, during a portion of the time interval during which the corresponding emitter is inactive, the signal induced in each detector from the corresponding emitter resulting in an output level from the programmable amplifier exceeding the reference level, so that signals induced by each light beam can be distinguished from signals due to ambient conditions and the variability of the components of the touch input device.