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Cross-point matrix for infrared touchscreen

  • US 20040145575A1
  • Filed: 01/29/2003
  • Published: 07/29/2004
  • Est. Priority Date: 01/29/2003
  • Status: Active Grant
First Claim
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1. A circuit assembly for detecting a touch point within a display area, comprising:

  • s a plurality of light emitters disposed around a periphery of said display area;

    a plurality of detectors disposed around said periphery, each detector being opposed to a respective light emitter; and

    switching circuitry for connecting said light emitters and detectors in a switching matrix having a plurality of matrix rows and matrix columns, wherein said switching circuitry includes;

    a plurality of row lines, each row line corresponding to a respective matrix row;

    a plurality of column lines, each column line corresponding to a respective matrix column;

    a plurality of light emitter transistors each coupled between a respective light emitter and a respective row line, each light emitter transistor having a control input coupled to a respect column line and responsive to a respective column select signal for connecting its respective light emitter to said respective row line;

    a plurality of pull-up resistances each coupling a respective one of said row lines to a predetermined voltage; and

    a plurality of row transistors each coupled between a respective row line and ground, each row transistor having a control input coupled to a respective row line and responsive to a row select signal for selectably connecting its respective row line to ground.

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