Carroll Touch Inc.

Paul B Lucas

James E Garrett

Timothy E Masters

John K Carstedt

A touch input device which continuously samples and digitally stores ambient light readings and compares these with previously stored readings is taught. Briefly stated, a phototransistor is turned on before, during and after an LED emitter energization. An ambient value is calculated which is subtracted from the value obtained during LED firing so as to develop a signal indicative of the presence or absence of the LED pulse, irrespective of ambient light fluctuations. The ambient level is stored for comparison purposes during the next sampling of the associated phototransistor.

Touch input device having digital ambient light sampling

An infrared touch input system is taught. Briefly stated, the system comprises a four-sided frame having an infrared transparent bezel along the inside thereof and having infrared emitters along the top and one side of the frame with infrared detectors along the sides opposite the emitters. Darlington transitor arrays are used as source and sink drivers for driving the LED's in an array. The I/O lines of a microprocessor in conjunction with the source and sink drivers are used to selectively energize each LED. Additional I/O lines of the microprocessor in conjunction with BCD decoders are used to selectively energize corresponding infrared detecting phototransistors before, during and after LED turn-on. A host computer supplies a clocking signal for the microprocessor with programming in the microprocessor thereby automatically performing the selection and deselection of emitters and detectors. A serial data stream is outputted from the microprocessor which indicates to the host computer the location of any broken light beams thereby indicating a stylus hit.

Touch input device

An infrared touch input system having bezel glare compensation via power profiling is taught. Briefly stated, a touch input system is utilized having a four-sided frame and having an infrared transparent bezel along the inside thereof and having infrared emitters along the top and one side of the frame with infrared detectors along the sides opposite the emitters. The optical power used with emitter-detector pairs adjacent the corners of the bezel is reduced with respect to emitter-detector pairs approaching the center of the bezel. In this manner, light which is reflected after striking the side of the bezel adjacent the emitter-detector pair and which is received by the emitter is of low intensity or is ignored.

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Urbana, IL, United States of America

Paul B Lucas