Adaptive thresholding scheme for optically-based touch screens
First Claim
1. An adaptive thresholding circuit for use with an optically-based touch screen of the type which is overlaid on the face of a display, said display being used to display a plurality of touch targets, said targets being respective sources of signals, said circuit comprising:
- means for receiving signals from said plurality of targets,means for establishing a single threshold for said targets based on the levels of said signals as they are received from said plurality of targets over a predetermined period of time, andmeans for comparing said threshold with the level of ones of said signal received from said plurality of targets over a subsequent period of time, and for generating a predetermined signals for each of said ones of said subsequently received signals that exceeds said threshold.
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Abstract
The sensitivity of an optically-based touch screen is substantially impro by adaptively establishing the detection threshold based on the peak trapped light measured over a number of frames on the screen being painted. In accordance with one feature of the invention, the peak trapped light from a target area painted on the screen is compared with a priorly established threshold as a way of determining that a target area is being touched by the user. In accordance with another feature of the invention, the threshold is modified in a way that compensates for possible erroneous touch indications due, for example, to bright spots on the screen.
34 Citations
11 Claims
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1. An adaptive thresholding circuit for use with an optically-based touch screen of the type which is overlaid on the face of a display, said display being used to display a plurality of touch targets, said targets being respective sources of signals, said circuit comprising:
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means for receiving signals from said plurality of targets, means for establishing a single threshold for said targets based on the levels of said signals as they are received from said plurality of targets over a predetermined period of time, and means for comparing said threshold with the level of ones of said signal received from said plurality of targets over a subsequent period of time, and for generating a predetermined signals for each of said ones of said subsequently received signals that exceeds said threshold. - View Dependent Claims (2, 3, 4, 5)
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6. An adaptive thresholding circuit for use with an optically-based touch screen of the type which is overlaid on the face of a display, said display being used to display at least one pattern of touch targets, said arrangement comprising
means for receiving signals from said plurality of targets, said signals having respective signal levels, means for establishing a common signal level threshold for said plurality of targets based on the levels of said signals as they are received from said plurality of targets over a predetermined period of time, and means responsive to said threshold and to the level of individual ones of said signals subsequently received from said plurality of targets for outputting a predetermined signal whenever one of said ones of said subsequently receive signals exceeds said threshold.
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11. A method of performing adaptive thresholding of signals received from a plurality of sources of signals, said signals having respective signal levels, said method comprising the steps of
establishing a common threshold for said plurality of sources based on the levels of the signals as they are received from said plurality of sources over a predetermined period of time. comparing said threshold with the level of ones of said signals receive from said plurality of sources over a subsequent period of time, and generating a predetermined signal for each of said ones of said subsequently received signals having a level which exceeds said common threshold.
Specification