| 摘要 |
<p>A method for minimizing the shadowing effects of a contaminant on a surface acoustic wave touchscreen is provided. The disclosed system compares the measured waveform against a baseline waveform for each axis and validates the new touch if the measured waveform is different from the baseline waveform for either axis. As a consequence of this approach, even if the new touch lies within the shadow created by a contaminant in one axis, the new touch is still validated as it is not within the shadow created by the contaminant in the second axis. In one embodiment, after the system determines that the measured response is different from the baseline in at least one axis, the system compares the new touch to one or more selection criteria to insure that it is a valid touch and not due to a contaminant, electrical noise, or other improper source. Preferably the duration of the new touch is monitored, thus allowing the new touch to be invalidated if the duration is too short, indicating system noise, or too long, indicating for example, a contaminant. Also preferably the size of the new touch is determined, thus allowing the touch to be invalidated if the size is too large which may be indicative of a contaminant or other foreign body resting on the touchscreen surface.</p> |
