Capacitance-based proximity with interference rejection apparatus and methods

Claim 2

A capacitance-based proximity sensor for locating the position of an object while rejecting a frequency of electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, and (c) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of electrical interference, wherein the generator means comprises means for evaluating the electrical interference and for producing the reference signal, and wherein the evaluating means includes means for storing a table of frequencies of selected reference signals and measures of electrical interference IM for each of these frequencies, and for producing a reference signal whose frequency has the lowest IM associated therewith.

Claim 3

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, (c) object locator means responsive to the measurement means for producing a position signal, having a high frequency component, indicating the position of the object relative to the electrode array, (d) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference, and wherein said generator means comprises evaluation means responsive to the object locator means for determining the magnitude of the high frequency component of the position signal, and means responsive to the evaluation means for changing the frequency of the reference signal when the magnitude of the high frequency component of the position signal exceeds a predetermined value.

Claim 4

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, (c) object locator means responsive to the measurement means for producing a position signal, having a high frequency component, indicating the position of the object relative to the electrode array, (d) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference, and wherein said generator means comprises evaluation means responsive to the object locator means for determining the magnitude of the high frequency component of the position signal, and means responsive to the evaluation means for changing the frequency of the reference signal when the magnitude of the high frequency component of the position signal exceeds a predetermined value.

Claim 5

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, wherein said measurement means comprises driver means for developing, synchronously with the reference signal, voltage changes on the electrode array, charge measuring means for measuring, synchronously with the reference signal, charges coupled to the electrode array and thus capacitance, means for selectively inhibiting the driver means from developing voltage changes, the coupled charge measurements made during inhibition of the driver means representing the interference measure IM, and (c) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference, wherein said generator means includes means for changing the frequency of the reference signal when the interference measure IM exceeds a predetermined level.

Claim 6

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, wherein said measurement means comprises driver means for developing, synchronously with the reference signal, voltage changes on the electrode array, charge measuring means for measuring, synchronously with the reference signal, charges coupled to the electrode array and thus capacitance, means for selectively inhibiting the driver means from developing voltage changes, the coupled charge measurements made during inhibition of the driver means representing the interference measure IM, and (c) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference, wherein said generator means includes means for changing the frequency of the reference signal when the interference measure IM exceeds a predetermined level.

Claim 7

The proximity sensor as in claim 3 wherein the generator means further includes means for storing a table of frequencies of reference signals and associated interference measures IM made for reference signals with each of such frequencies, and for producing a reference signal whose frequency has the lowest interference measure IM associated therewith.

Claim 8

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, wherein the electrode array comprises a plurality of first electrode strips spaced apart from each other in a first array, and a plurality of second electrode strips spaced apart from each other and in close proximity with the first electrode strips; (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, and (c) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference.

Claim 9

A capacitance-based proximity sensor for locating the position of an object while rejecting electrical interference, comprising: (a) an electrode array for forming capacitances which vary with movements of the object, wherein the electrode array comprises a plurality of first electrode strips spaced apart from each other in a first array, and a plurality of second electrode strips spaced apart from each other and in close proximity with the first electrode strips; (b) measurement means coupled to the electrode array for measuring the capacitances synchronously with a reference signal, and (c) generator means for supplying a reference signal to the measurement means, said reference signal having a frequency which is not coherent with the frequency of the electrical interference.

Claim 10

The proximity sensor of claim 5 wherein the measurement means includes driver means for developing, synchronously with the reference signal, voltage changes on the electrode array, a charge transfer means coupled to the electrode array for producing synchronously with the frequency of the reference signal, measurement signals representing charges coupled onto the electrode array as a result of the voltage changes, synchronous demodulator means coupled to the charge transfer means for rectifying the measurement signals synchronously with the reference signal, and low pass filter means coupled to the synchronous demodulator means for producing signals representing the average DC values of the rectified signals, and thus representing the capacitances of the electrode array.

Claim 11

The proximity sensor of claim 6 wherein the measurement means includes a plurality of capacitance measurement elements, each being connected to a respective electrode strip.

Claim 12

The proximity sensor of claim 7 further comprising a plurality of synchronous demodulation elements, each connected to a respective capacitance measurement element.

Claim 13

The proximity sensor of claim 1 further including a position locator means connected to the output of the measurement means for providing a position signal representative of the location of the object relative to the electrode array.

Claim 14

The detection system of claim 1 wherein the electrode array comprises first and second electrode sets spaced from each other to develop a capacitance for the touch pad.

Claim 15

The detection system of claim 10 wherein the first and second set of electrodes are generally orthogonal to each other to form virtual electrodes to provide capacitance.

Claim 16

The detection system of claim 1 wherein the measuring means comprises a capacitive measurement element coupled to the electrode array, a synchronous demodulator coupled to the capacitive measurement element, and a low-pass filter coupled to the demodulator.

Claim 19

The method of claim 13 and further including producing a signal indicating the position of the object relative to the electrode array.