Touch panel with automatic frequency control
First Claim
1. A touch panel device for determining the touch location at which a touch sensing surface of the device is touched comprising:
- signal generator means for producing an alternating-current voltage output, the signal generator means having a frequency control input and comprising means for producing an alternating current voltage output of a frequency which is variable and controllable in response to a frequency control signal at the frequency control input;
panel scanning signal applying means for applying panel scanning signals to the touch sensing surface, the panel scanning signal applying means having an input coupled to the signal generator output, the panel scanning signal applying means having first and second panel scanning outputs comprising respective first and second alternating-current voltage panel scanning signals which are driven by the signal generator output and which are one hundred and eighty degrees out of phase from one another;
touch signal detection means having inputs coupled to the first and second panel scanning outputs and a touch signal output, the touch signal detection means comprising means for producing touch signals at the touch current signal output corresponding to the difference between the first and second panel scanning signals;
switching means for selectively coupling the first and second panel scanning outputs to the touch sensing surface so as to selectively apply the first and second panel scanning signals to the touch sensing surface and generate touch current signals at the touch signal output upon touching the touch sensing surface; and
panel output signal processing means having a first input coupled to the touch signal output for receiving the touch current signals, the panel output signal processing means comprising means for determining the touch location from the touch current signals, the panel output signal processing means including signal generator frequency control circuit means coupled to the frequency control input for automatically generating frequency control signals and applying such frequency control signals to the frequency control input, the frequency control means comprising means for automatically generating frequency control signals to shift the frequency of the signal generator means output away from fixed frequency interference spectra, such as due to cathode-ray-tube flyback signals, in the environment in which the touch panel device is used.
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Accused Products
Abstract
A touch panel has panel scanning signals selectively applied to the four sides of a touch sensing surface of the panel so as to establish alternating current voltage gradients in desired directions across the touch sensing surface. When the panel is touched, touch signals result and are utilized by a touch location circuit in determining the location of touch. The impedence touch current resulting from a user'"'"'s touch may also be determined and used. The touch panel circuit automatically adjusts the frequency of the applied panel signals to shift this frequency away from fixed frequency interference spectra, such as due to cathode-ray tube flyback signals, in the environment in which the touch panel is used. The touch location thereby minimizes the effects of such spectra on touch location determinations.
124 Citations
17 Claims
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1. A touch panel device for determining the touch location at which a touch sensing surface of the device is touched comprising:
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signal generator means for producing an alternating-current voltage output, the signal generator means having a frequency control input and comprising means for producing an alternating current voltage output of a frequency which is variable and controllable in response to a frequency control signal at the frequency control input; panel scanning signal applying means for applying panel scanning signals to the touch sensing surface, the panel scanning signal applying means having an input coupled to the signal generator output, the panel scanning signal applying means having first and second panel scanning outputs comprising respective first and second alternating-current voltage panel scanning signals which are driven by the signal generator output and which are one hundred and eighty degrees out of phase from one another; touch signal detection means having inputs coupled to the first and second panel scanning outputs and a touch signal output, the touch signal detection means comprising means for producing touch signals at the touch current signal output corresponding to the difference between the first and second panel scanning signals; switching means for selectively coupling the first and second panel scanning outputs to the touch sensing surface so as to selectively apply the first and second panel scanning signals to the touch sensing surface and generate touch current signals at the touch signal output upon touching the touch sensing surface; and panel output signal processing means having a first input coupled to the touch signal output for receiving the touch current signals, the panel output signal processing means comprising means for determining the touch location from the touch current signals, the panel output signal processing means including signal generator frequency control circuit means coupled to the frequency control input for automatically generating frequency control signals and applying such frequency control signals to the frequency control input, the frequency control means comprising means for automatically generating frequency control signals to shift the frequency of the signal generator means output away from fixed frequency interference spectra, such as due to cathode-ray-tube flyback signals, in the environment in which the touch panel device is used. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A touch panel device for determining the touch location at which a touch sensing surface of the device is touched comprising:
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signal generator means for producing an alternating-current voltage output, the signal generator means having a frequency control input and comprising means for producing an alternating current voltage output of a frequency which is variable and controllable in response to a frequency control signal at the frequency control input; panel scanning signal applying means for applying panel scanning signals to the touch sensing surface, the panel scanning signal applying means having an input coupled to the signal generator output, the panel scanning signal applying means having first and second panel scanning outputs comprising respective first and second alternating-current voltage panel scanning signals which are driven by the signal generator output and which are one hundred and eighty degrees out of phase from one another; touch signal detection means having inputs coupled to the first and second panel scanning outputs and a touch signal output, the touch signal detection means comprising means for producing touch current signals at the touch signal output corresponding to the difference between the first and second panel scanning signals; switching means for selectively coupling the first and second panel scanning outputs to the touch sensing surface so as to selectively apply the first and second panel scanning signals to the touch sensing surface and generate touch current signals at the touch signal output upon touching the touch sensing surface; panel output signal processing means having a first input coupled to the touch signal output for receiving the touch current signals, the panel output signal processing means comprising means for determining the touch location from the touch current signals, the touch signals being at a null value when the touch sensing surface is not touched; the panel output signal processing means including signal generator frequency control means coupled to the frequency control input for automatically generating frequency control signals and applying such frequency control signals to the frequency control input to control the frequency of the output of the signal generator means, the signal generator frequency control means generating an initial frequency control signal for setting the signal generator output means frequency to an initial frequency, the panel output signal processing means including means for establishing a null threshold and for comparing the null touch signals generated at the initial frequency to the null threshold, the signal generator frequency control means comprising means for automatically changing the initial frequency control signal to thereby change the signal generator means output frequency to a second frequency different from the initial frequency in the event the null touch signals generated at the initial frequency exceed the null threshold. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification