Use of resistive touch screen as a proximity sensor
First Claim
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1. A touch screen proximity sensing apparatus comprising:
- a touch screen comprising a bottom layer and a top layer wherein the top layer and bottom layer are oriented such that they are separate but capable of being temporarily pressed together by a user;
a control circuit operatively connected to the touch screen;
a plurality of measurement circuits comprising;
a first measurement circuit comprising a resistive sensor circuit; and
a second measurement circuit comprising a proximity capacitance sensor circuit;
wherein the proximity capacitance sensor circuit detects an object by determining an equivalent capacitance between the touch screen and the object, and comprise a bias circuit configured to apply a particular voltage to the bottom layer of the touch screen, said particular voltage being substantially the same as the voltage applied to the top layer;
wherein the resistive sensor circuit measures a touch position by measuring a voltage along a voltage gradient on at least one of the top layer and bottom layer;
wherein the control circuit selectively connects the touch screen with one of the plurality of measurement circuits; and
wherein the control circuit disables the first measurement circuit when said object is detected, said object being a face of said user, the control circuit only enabling the first measurement circuit when said object is no longer detected.
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Abstract
An apparatus and method for the use of a resistive touch screen as a proximity sensor. The touch screen operates in a touch sensing mode and a proximity sensing mode. The proximity sensing mode turns off the touch sensing circuit and uses the equivalent capacitor formed by the top layer of the touch screen with a nearby object to detect proximity. A control circuit selectively connects the touch screen with measurement circuits to perform each of the sensing functions. The control circuit can be implemented with timing based control or an event driven topology.
4 Citations
15 Claims
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1. A touch screen proximity sensing apparatus comprising:
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a touch screen comprising a bottom layer and a top layer wherein the top layer and bottom layer are oriented such that they are separate but capable of being temporarily pressed together by a user; a control circuit operatively connected to the touch screen; a plurality of measurement circuits comprising; a first measurement circuit comprising a resistive sensor circuit; and a second measurement circuit comprising a proximity capacitance sensor circuit; wherein the proximity capacitance sensor circuit detects an object by determining an equivalent capacitance between the touch screen and the object, and comprise a bias circuit configured to apply a particular voltage to the bottom layer of the touch screen, said particular voltage being substantially the same as the voltage applied to the top layer; wherein the resistive sensor circuit measures a touch position by measuring a voltage along a voltage gradient on at least one of the top layer and bottom layer; wherein the control circuit selectively connects the touch screen with one of the plurality of measurement circuits; and wherein the control circuit disables the first measurement circuit when said object is detected, said object being a face of said user, the control circuit only enabling the first measurement circuit when said object is no longer detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a system comprising a touch screen comprising a bottom layer and a top layer, and a plurality of measurement circuits comprising a capacitive proximity circuit and a resistive touch circuit, a method for proximity detection using the touch screen comprises the steps of:
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performing a resistive touch operation by a user comprising the steps of; disabling the plurality of measurement circuits that are not the resistive touch circuit; operatively connecting the resistive touch circuit and the touch screen; and measuring touch information obtained by the touch screen; performing a proximity capacitive sensing operation comprising the steps of; disabling the plurality of measurement circuits that are not the capacitive proximity circuit; operatively connecting the capacitive proximity circuit and the touch screen; applying a particular voltage to the bottom layer of the touch screen, the particular voltage being substantially the same as the voltage applied to the top layer of the touch screen; and measuring proximity information obtained by the touch screen; generating a mode selection signal comprising a touch state and a proximity state, said mode selection signal being maintained in said proximity state when a face of said user is detected to be in contact with said touch screen by said capacitive proximity circuit; performing the resistive touch operation when the mode selection signal is in the touch state; and performing the proximity capacitive sensing when the mode selection signal is in the proximity state. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification