Adaptive frequency touchscreen controller and method for controlling touchscreen thereby

Abstract

A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilizw look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator.

Description

technical field [0001] The present invention relates generally to touch screens and, more particularly, to methods and apparatus for adjusting the frequency of a touch screen controller to match the controller to the specific operating characteristics of a particular touch screen. technical background [0002] Touch screens are used in conjunction with various display types, including cathode ray tubes (ie, CRTs) and liquid crystal displays (ie, LCD screens), as a means of entering information into data processing systems. When the touch screen is placed on the display screen or integrated into the display screen, the user can select the displayed icon or element by touching the position corresponding to the target icon or element on the screen. Touch screens have become commonly used in a variety of different applications including, for example, point of sale systems, information kiosks, automated teller machines (ie, ATMs), data entry systems, and the like. [0003] In on...

AI Technical Summary

Problems solved by technology

[0008] Global or local frequency mismatches can be caused by different sources

While some sources of mismatch can be overcome with adequate quality control, such controls are often costly

For example, variations in touch screen glass substrates may alter the acoustic velocity, resulting in a global frequency mismatch, and it may not be economically feasible to adequately control the glass supply chain and manufacturing process to ensure that the acoustic velocity of all substrates is within a narrow range

Controlling the glass supply chain and manufacturing process is even more problematic when the acoustically reflective array is printed directly onto the faceplate of a cathode ray tube (i.e. CRT)

Print mask distortion is especially problematic if the array is to be printed directly onto a CRT panel

Other array printing techniques such as embossing also suffer from registration errors introduced during the printing process, which can lead to further frequency mismatches

Yet another source of frequency mismatch can come from improper correction for spherical geometry effects on non-planar substrate surfaces

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