Multiplexed Infrared Touch Panel Scanning System
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
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.