Carroll Touch Inc.

Amp LLC

Elo Touchsystems, Inc.

Tyco Electronics Corporation

Timothy E Masters

Wayne J Wehrer

John J Deacon

James E Garrett

Paul B Lucas

John K Carstedt

Henry A Grice, Jr

Robert W Knetsch

John Deacon

A touch system using a plurality of infrared (&ldquo;IR&rdquo;) transmitters and receivers, and a method of determining with increased resolution the location of a touch between the IR transmitters and receivers using on-axis and off-axis detection are disclosed. The inventive touch system and method use, in conjunction with the on-axis and off-axis detection, a coarse and fine sweep of the transmitters and receivers to increase the resolution of identified touch location. The method of determining a touch location involves selection and activation of particular off-axis infrared transmitter and receiver pairs determined from a triangulation interdependence between the x and y coordinates. The increased resolution of the identified touch location is achievable using the inventive system and method without the need for an increased number of IR transmitters and receivers and without the need for higher speed processing capability.

Apparatus and method to improve resolution of infrared touch systems

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

A current injection compensation circuit for dynamically compensating for the effect of ambient conditions on phototransistor output is disclosed. An output voltage is maintained at a nominal reference voltage level independent of ambient light input to allow use of a large output for a detected signal. Phototransistor current is a function only of ambient conditions, especially incident ambient light and is unaffected by compensation current injection. The ambient compensation current injection network can be employed with interactive touch input devices, such as infrared touch entry systems used with video displays.

Phototransistor apparatus with current injection ambient compensation

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Georgetown, TX, United States of America

Timothy E Masters