Cross-point matrix for infrared touchscreen
First Claim
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.
5 Assignments
0 Petitions
Accused Products
Abstract
A circuit assembly detects a touch point within a display area. A plurality of light emitters are disposed around a periphery of the display area. A plurality of detectors are disposed around the periphery, each detector being opposed to a respective light emitter. Switching circuitry for connecting the light emitters and detectors in a switching matrix has a plurality of matrix rows and matrix columns. The switching circuitry includes a plurality of row lines, each row line corresponding to a respective matrix row and a plurality of column lines, each column line corresponding to a respective matrix column. Low-side switching transistors selectably couple the light emitters and detectors to the row and column lines, respectively. A common modulated signal is coupled to the anodes of all the light emitters. A detection signal is provided by connecting the collector terminals for the detector phototransistors in common. Consequently, high-side multiplexing circuits are avoided.
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Citations
16 Claims
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1. A circuit assembly for detecting a touch point within a display area, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A touch screen display comprising:
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an electronically-controlled visual display panel for presenting visual information within a display area;
a touch-point circuit assembly including;
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, said detectors having respective output terminals connected in common to provide a detection signal; 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 respective 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; and
a controller for selectably activating pairs of said light emitters and detectors in a sequence to detect said touch point. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification