Browse Prior Art Database

Multiplexed Infrared Touch Panel Scanning System

IP.com Disclosure Number: IPCOM000038907D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR [+3]

Abstract

This article describes a multiplexed scanning control system that reduces interface wiring for the touch-sensitive infrared (IR) panels. The circuit uses shift registers and software to replace wires. Further, a simplified method of self-test is provided. (Image Omitted) Infrared touch panels contain a bezel that surrounds a display, such as a CRT. Fig. 1 shows a typical arrangement wherein IR light- emitting diodes (LEDs) and photo-detectors are mounted in the bezel. The bezels are usually bulky and difficult to package because of the amount of interface wiring and circuitry built into them. Fig. 2 shows the conventional method of sequentially driving the LEDs and reading the photo-detector outputs. "M" coded lines enter the bezel assembly which contains decode logic to sequentially turn on "N" LED/drivers.

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Multiplexed Infrared Touch Panel Scanning System

This article describes a multiplexed scanning control system that reduces interface wiring for the touch-sensitive infrared (IR) panels. The circuit uses shift registers and software to replace wires. Further, a simplified method of self-test is provided.

(Image Omitted)

Infrared touch panels contain a bezel that surrounds a display, such as a CRT. Fig. 1 shows a typical arrangement wherein IR light- emitting diodes (LEDs) and photo-detectors are mounted in the bezel. The bezels are usually bulky and difficult to package because of the amount of interface wiring and circuitry built into them. Fig. 2 shows the conventional method of sequentially driving the LEDs and reading the photo-detector outputs. "M" coded lines enter the bezel assembly which contains decode logic to sequentially turn on "N" LED/drivers. Similarly, decode logic gates the photo-detector outputs to determine optical path continuity. Because of the relatively large number of control signals, control logic self-test is difficult to implement. Fig. 3 is a block diagram of the scanning control system disclosed herein. It shows a multiplexed scanning control system that reduces the interface wiring and amount of circuitry on the bezel 2, shown in broken lines. A microprocessor controller 1 requires only a 3-wire connection to the bezel. The controller is housed remotely from the bezel. The microprocessor 1 executes a scan sequence by producing sequent...